Abstract
The epidemiologic features of reactivated cytomegalovirus (CMV) antigenemia were studied among 4,382 cancer patients who were cared for and tested at the University of Texas M. D. Anderson Cancer Center from 2001 to 2004. The effects of stem cell transplant (SCT) status, underlying disease, age, sex, ethnicity, and antibody status (prior to CMV exposure) on the incidence of CMV antigenemia were determined; and the CMV burdens were quantified. Antigenemia occurred in 9.3% of patients with non-SCT (n = 2511), 12.0% with autologous SCT (n = 582), and 39.1% with allogeneic SCT (n = 1289). Non-SCT patients with lymphoid tumors had a significantly higher rate of antigenemia than those with myeloid tumors (13.6% versus 3.9%) (P < 0.001); however, after allogeneic SCT, the underlying diseases had little effect, except for multiple myeloma (56.8%) (P = 0.014). Among the allogeneic SCT recipients, higher CMV antigenemia rates were also associated with female sex, older age, and positivity for pre-SCT CMV antibody. Depending on the underlying disease and its associated initial CMV risk, allogeneic SCT increased the risk by 2.6- to 29.6-fold (overall, 4.0-fold). With or without SCT, Asians had the highest CMV antigenemia rates and burdens, followed by blacks, Hispanics, and whites, and these partially correlated with antibody prevalence. Among the 808 patients with antigenemia, the circulating peak CMV burden was significantly higher among non-SCT patients (geometric mean, 18.7 positive cells per 106 leukocytes) than among allogeneic SCT patients (geometric mean, 7.7 positive cells per 106 leukocytes) or autologous SCT patients (geometric mean, 7.0 positive cells per 106 leukocytes) who underwent monitoring for CMV. Together, these results allow stratification of CMV risks and suggest a substantial CMV reactivation among non-SCT cancer patients and, thus, the need for better diagnosis and control.
Human cytomegalovirus (CMV), a β-herpesvirus, causes a variety of infections, such as congenital infections in neonates, infectious mononucleosis in healthy individuals, and reactivation in immunocompromised patients (18). CMV reactivation is a common and severe problem in organ and stem cell transplant (SCT) recipients and in those infected with human immunodeficiency virus (HIV), particularly before the era of effective antiretroviral therapy. Among SCT recipients, the rate of CMV reactivation in the bloodstream (antigenemia or viremia) has been reported to be from 30% to 70% (2, 11, 13). Routine monitoring of CMV antigenemia by testing for the CMV pp65 antigen (or other means) has played a crucial role in detecting the virus and guiding effective antiviral therapy in SCT recipients (4, 16).
The incidence of CMV antigenemia among patients who have severe underlying diseases, such as leukemia, lymphoma, or solid tumors, but who are not transplant recipients or HIV infected is largely unknown. In this population, CMV antigenemia has been reported only in small series or case studies (7-9). Even among SCT and organ transplant recipients, large-scale epidemiologic studies performed to determine the effects of underlying diseases (and associated treatment), sex, age, and ethnicity on antigenemia are scanty. As the incidence of cancer increases, because cancer care has improved and intensified over recent decades, and as patients with cancer survive longer, various infectious complications have become more pronounced. Therefore, in-depth knowledge of the epidemiology of CMV antigenemia in cancer patients is important not only clinically for risk assessment and the timely diagnosis and treatment of the infection to allow better management of underlying cancers but also scientifically for better understanding of the virus-host interaction.
In this study, I performed a comprehensive epidemiologic analysis of the incidence of CMV antigenemia in 4,382 consecutively tested patients with cancer who had or had not received SCT. Patients were stratified by SCT status, underlying disease, age, sex, ethnicity, and antibody status. The CMV burden among various groups was analyzed quantitatively. These analyses provided remarkable insight into how these factors influence the incidence of reactivated CMV antigenemia.
MATERIALS AND METHODS
This retrospective cohort study included all consecutive patients who were tested for blood CMV pp65 antigen from January 2001 to December 2004 at The University of Texas M. D. Anderson Cancer Center, a 500-bed comprehensive cancer center in Houston, TX. Patients were identified through an electronic database search of archived microbiology records. Almost all patients had a primary diagnosis of cancer or precancerous disease. Rare patients positive for HIV or healthy donors were excluded. This study was approved by the center's institutional review board.
The CMV pp65 data were obtained from microbiology records. Clinical and demographic data were abstracted from electronic medical records and registration information. The ethnicity of a patient was based on registration information, continental origin, name, language, and religion. A patient's SCT status was either non-SCT, autologous SCT (auto-SCT), or allogeneic SCT (allo-SCT). Allo-SCT superseded prior auto-SCT, if applicable. The sources and donor types of stem cells for allo-SCT were not further stratified.
The blood CMV pp65 antigen test was based on the monoclonal antibody against the virus and immunofluorescence (Chemicon International, Inc., Temecula, CA). The test was standardized and performed consistently over the years in my laboratory (16). When the test results were positive, the number of positive cells per 106 circulating white blood cells (WBCs) was measured. All allo-SCT recipients were monitored one to three times per week after SCT until at least day 100, and most patients underwent CMV prophylaxis. Most auto-SCT recipients were also tested, but not as regularly. Non-SCT patients with hematologic tumors were frequently tested during antineoplastic treatment, particularly after an extended period of lymphopenia, a known risk for CMV reactivation. This practice was learned over the years at The University of Texas M. D. Anderson Cancer Center. Non-SCT patients with solid tumors were infrequently tested, and there were hardly any guidelines. They were mainly tested during times of acute illness or complications, such as when they had neutropenic fever or were admitted to the hospital and required a differential diagnosis of CMV infection; in general, those who were tested had clinically more severe illness than those who were not tested. Therefore, the necessity to use the pp65 test provided a clinically approximated baseline for all patients with or without SCT.
Anti-CMV antibody data from January 2000 to December 2004 were retrieved and covered antigenemia data 1 year before the pre-SCT period. The antibody test was based on latex agglutination (BD Microbiology Systems, Sparks, MD) or enzyme-linked immunoassay (Diamedix, Miami, FL), or both.
Categorical data were analyzed primarily by the χ2 test. Quantitative data for the number of CMV-positive cells were transformed by logarithm first and were then analyzed by Student's t test. A few web-based statistical tools were used for such analyses. Significant P values (≤0.05) or nearly significant ones are given.
RESULTS
During the 4-year period studied, 4,382 patients were tested for CMV antigenemia, with 50,932 tests performed. There were 2,547 men and 1,835 women, with a mean age of 50 years (24.7 years and 71.0 years for the 10th and 90th percentiles, respectively).
There were 3,163 whites, 672 Hispanics, 342 blacks, and 205 Asians; and the mean ages for these four groups were 53.4, 41.1, 47.5, and 41.4 years, respectively. Because of international referral, immigration, and the overall older age of cancer patients, a significant portion of Hispanics and Asians were from or born in foreign countries. On the other hand, most whites and blacks were born in the United States.
The numbers of patients with non-SCT, auto-SCT, and allo-SCT were 2,511, 582, and 1,289, respectively. Allo-SCT patients underwent a mean of 32.1 CMV antigenemia tests, with a median testing span (from the first test to the last test during the study years, up to 4 years) of 213 days (44 days and 903 days for the 10th and 90th percentiles, respectively). Auto-SCT and non-SCT patients underwent a mean of 4.2 and 2.8 tests, respectively, and their median testing spans were 18 days and 1 day, respectively; despite the fewer number of CMV tests, the overall clinical follow-up of these patients was comparable to or even longer than that of allo-SCT patients. Typically, a positive test led to multiple follow-up tests, whereas a negative test ruled out the presence of CMV antigenemia, particularly in the non-SCT setting.
Association of underlying diseases and SCT with CMV antigenemia.
Table 1 shows the associations of underlying diseases and SCT with CMV antigenemia. Patients with a wide range of underlying cancer types, whether or not they were treated by the use of SCT, showed detectable CMV antigenemia; however, the rates varied considerably.
TABLE 1.
Frequency of CMV antigenemia by cancer type and SCT status
| Underlying disease | No. of patients positive for CMV antigenemia/no. tested (%)
|
RR (P value)a | ||
|---|---|---|---|---|
| Non-SCTb | Auto-SCTc | Allo-SCTd | ||
| Lymphoid hematologic malignancies | 161/1,180 (13.6) | 223/565 (39.5) | 2.9 (<0.001) | |
| Acute lymphoblastic leukemia | 26/235 (11.1) | 66/150 (44.0) | 4.0 (<0.001) | |
| Chronic lymphocytic leukemia | 66/400 (16.5) | 36/85 (42.4) | 2.6 (<0.001) | |
| Lymphoma | 69/545 (12.7) | 36/278 (12.9) | 121/330 (36.7) | 2.9 (<0.001) |
| Multiple myeloma | 7/77 (9.1) | 22/189 (11.6) | 25/44 (56.8) | 5.2 (<0.001) |
| Myeloid hematologic malignancies | 32/829 (3.9) | 217/582 (37.3) | 9.7 (<0.001) | |
| Acute myelogenous leukemia | 25/625 (4.0) | 155/381 (40.7) | 10.2 (<0.001) | |
| Chronic myelogenous leukemia | 6/120 (5.0) | 44/150 (29.3) | 5.9 (0.001) | |
| Myelodysplastic syndrome | 1/84 (1.2) | 18/51 (35.3) | 29.6 (<0.001) | |
| Other hematologic diseases | 3/59 (5.1) | 0/8 (0) | 17/39 (43.6) | 9.7 (<0.001) |
| Solid tumors and other nonhematologic diseases | 31/366 (8.5) | 12/107 (11.2) | 22/59 (37.3) | 4.1 (<0.001) |
| Total | 234/2,511 (9.3) | 70/582 (12.0) | 504/1,289 (39.1) | 4.0 (<0.001) |
RR, relative risk. The P values are for allo-SCT patients versus non-SCT and auto-SCT patients.
For non-SCT patients, lymphoid (161/1,180) versus myeloid (32/829), χ2 = 53.9 and P < 0.001; lymphoid (161/1,180) versus myeloma (7/77), χ2 = 1.29 and P was not significant.
For auto-SCT (70/582) versus non-SCT patients with the same cancer types (110/1,047), χ2 = 0.88 and P was not significant.
For allo-SCT patients, lymphoid (223/565) versus myeloid (217/582), χ2 = 0.59 and P was not significant; myeloma (25/44) versus all others (479/1,245), χ2 = 6.01 and P = 0.014.
Non-SCT patients had an overall positivity rate of 9.3%, and those with lymphoid hematologic malignancies were affected more than those with myeloid hematologic malignancies (13.6% versus 3.9%; P < 0.001). Among the latter group, those with myelodysplastic syndrome had an even lower positivity rate of 1.2% (1 of 84), suggesting that CMV reactivation occurs primarily among patients with severe underlying diseases involving the lymphoid system. Non-SCT patients with solid tumors had a tested CMV antigenemia rate of 8.5%; however, this rate was an overestimate, because most patients with solid tumors did not have severe complications or immune suppression that warranted testing for CMV. Overall, patients with solid tumors accounted for only 14.6% (366 of 2,511) of all non-SCT patients, which should not invalidate the study.
Auto-SCT patients had an overall positivity rate of 12.0%, similar to that of non-SCT patients who had the same underlying diseases (10.5%) (P > 0.05). Thus, auto-SCT did not appreciably increase the risk of CMV antigenemia.
Allo-SCT patients, despite routine prophylaxis, had an overall CMV antigenemia rate of 39.1%, four times that for non-allo-SCT patients (i.e., non-SCT and auto-SCT patients combined, owing to similar rates), and the types of underlying diseases (and their related treatments) had little effect on the rate. The only exception was patients with multiple myeloma, who had a positivity rate of 56.8%, which was significantly higher than that for allo-SCT patients with all other underlying diseases combined (38.5%) (P = 0.014). Compared with the CMV risk among non-allo-SCT patients with the same underlying diseases, the relative risk conferred by allo-SCT varied from 2.6 for chronic lymphocytic leukemia patients to 29.6 for myelodysplastic syndrome patients (Table 1).
The positivity rates in Table 1 represented cumulative rates by patient, which combined the number of tests as well as the lengths of follow-up per patient. By individual test, the positivity rates for the allo-SCT, auto-SCT, and non-SCT groups were 4.6% (1,917 of 41,440 tests), 5.9% (145/2,453), and 9.0% (637/7,039), respectively, or 5.3% (2,699/50,932) overall. These rates, however, did not adequately reflect the CMV risk in the allo-SCT setting. Rather, the vast number of tests in the allo-SCT setting reflected the CMV risk and the need to detect it after SCT, usually within several weeks.
Association of ethnicity with CMV antigenemia.
Ethnic differences were analyzed after the stratification of the patients by SCT status and their underlying diseases. Among the non-allo-SCT patients tested (Table 2), the CMV antigenemia rates were 18.0% for Asians, 13.6% for blacks, 12.6% for Hispanics, and 8.3% for whites. The difference between whites and each of the other ethnic groups was highly significant (P ≤ 0.003). Higher rates were found among nonwhite patients with acute lymphoblastic leukemia, lymphoma, and multiple myeloma than among white patients with the same diseases, with most differences being statistically significant. In contrast, similar rates for patients with chronic lymphocytic leukemia and myeloid and other hematologic diseases were found among all ethnic groups. In all disease categories with significant differences between ethnic groups, Asians had the highest rates.
TABLE 2.
Association of ethnicity with CMV antigenemia among non-SCT and auto-SCT patients combined
| Underlying disease | No. of patients positive for CMV antigenemia/no. tested (%)
|
P value for whites vs those of the following ethnicities:
|
|||||
|---|---|---|---|---|---|---|---|
| White | Black | Asian | Hispanic | Black | Asian | Hispanic | |
| Acute lymphoblastic leukemia | 7/110 (6.4) | 2/18 (11.1) | 3/13 (23.1) | 14/94 (14.9) | NSa | 0.037 | 0.041 |
| Chronic lymphocytic leukemia | 57/344 (16.6) | 5/33 (15.2) | 1/8 (12.5) | 3/15 (20.0) | NS | NS | NS |
| Lymphoma | 56/588 (9.5) | 16/70 (22.9) | 8/31 (25.8) | 25/134 (18.7) | <0.001 | 0.004 | 0.003 |
| Multiple myeloma | 10/165 (6.1) | 11/52 (21.2) | 3/13 (23.1) | 5/36 (13.9) | 0.001 | 0.023 | NS |
| Myeloid and other hematologic diseases | 25/658 (3.8) | 3/79 (3.8) | 3/36 (8.3) | 4/123 (3.3) | NS | NS | NS |
| Solid tumors and other nonhematologic diseases | 29/357 (8.1) | 2/34 (5.9) | 6/32 (18.8) | 6/50 (12.0) | NS | 0.045 | NS |
| Total | 184/2,222 (8.3) | 39/286 (13.6) | 24/133 (18.0) | 57/452 (12.6) | 0.003 | <0.001 | 0.003 |
NS, not significant.
Among the allo-SCT patients (Table 3), the overall antigenemia rate was again the highest for Asians (61.1%), followed by blacks (48.2%), Hispanics (40.9%), and whites (36.5%). Thirteen (92.9%) of the 14 Asians with acute lymphoblastic leukemia were CMV viremic; this rate is significantly higher than the rates for Asians with all other underlying diseases combined (53.4%; 31 of 58) and for patients of other ethnic groups with the same disease (all P ≤ 0.025); the only negative patient was a 13-year-old child who was negative for CMV antibody pre-SCT. Thus, given the right circumstances, all latent CMV can be reactivated. Asian patients with lymphoma and myeloid and other hematologic diseases also had significantly higher positivity rates than whites. Hispanic patients with multiple myeloma had the highest positivity rate (six of eight) in this disease category, and this rate was significantly higher than that for Hispanics with all other diseases combined (relative risk = 1.89; P = 0.046).
TABLE 3.
Association of ethnicity with CMV antigenemia among allo-SCT patients
| Underlying disease | No. of patients positive for CMV antigenemia/no. tested (%)
|
P value for whites vs those of other ethnicities
|
|||||
|---|---|---|---|---|---|---|---|
| White | Black | Asian | Hispanic | Black | Asian | Hispanic | |
| Acute lymphoblastic leukemia | 34/88 (38.6) | 3/7 (42.9) | 13/14 (92.9)a | 16/41 (39.0) | NSb | <0.001 | NS |
| Chronic lymphocytic leukemia | 33/80 (41.3) | 1/1 (100) | 1/1 (100) | 1/3 (33.3) | |||
| Lymphoma | 88/261 (33.7) | 4/8 (50.0) | 7/11 (63.6) | 22/50 (44.0) | NS | 0.041 | NS |
| Multiple myeloma | 15/30 (50.0)c | 4/6 (66.7) | 0/0 (0) | 6/8 (75.0)d | NS | NS | |
| Myeloid and other hematologic diseases | 155/436 (35.6) | 14/33 (42.4) | 23/44 (52.3) | 42/108 (38.9) | NS | 0.029 | NS |
| Solid tumors and other nonhematologic diseases | 18/46 (39.1) | 1/1 (100) | 0/2 (0) | 3/10 (30.0) | NS | ||
| Total | 343/941 (36.5) | 27/56 (48.2) | 44/72 (61.1) | 90/220 (40.9) | 0.077 | <0.001 | NS |
For Asians with acute lymphoblastic leukemia (13/14) versus Asians with all other diseases combined (31/58), χ2 = 7.37 and P = 0.007; for Asians with acute lymphoblastic leukemia (13/14) versus whites with acute lymphoblastic leukemia (34/88), χ2 = 14.3 and P < 0.001; for Asians with acute lymphoblastic leukemia (13/14) versus Hispanics with acute lymphoblastic leukemia (16/41), χ2 = 12.1 and P < 0.001; for Asians with acute lymphoblastic leukemia (13/14) versus blacks with acute lymphoblastic leukemia (3/7), P = 0.025 (by Fisher exact test).
NS, not significant.
For whites with myeloma (15/30) versus those with all other diseases (328/911), relative risk = 1.39, χ2 = 2.46, and P was not significant.
For Hispanics with myeloma (6/8) versus those with all other diseases (84/212), relative = 1.89, χ2 = 3.99, and P = 0.046.
Association of sex and age with CMV antigenemia.
An association between sex and CMV antigenemia was evident among the allo-SCT patients but not among the auto-SCT or the non-SCT patients (Table 4). Women with allo-SCT had a significantly higher rate than men with allo-SCT (relative risk = 1.2; P = 0.006). This difference was seen among all ethnic groups (data not shown).
TABLE 4.
Association of sex with CMV antigenemia
| Sex | No. patients positive for CMV antigenemia/no. tested (%)a
|
||
|---|---|---|---|
| Non-SCT | Allo-SCT | Auto-SCT | |
| Male | 148/1,488 (9.9) | 279/774 (36.0) | 36/285 (12.6) |
| Female | 86/1,023 (8.4) | 225/515 (43.7) | 34/297 (11.4) |
The relative risks (P values for women versus men) for the non-SCT, allo-SCT, and auto-SCT patients were 0.85 (P was not significant), 1.2 (P = 0.006), and 0.91 (P was not significant), respectively.
Age was significantly associated with CMV antigenemia in allo-SCT patients in a linear fashion: the older that the patients were, the higher that the rate was (Fig. 1), reaching 50% for those ≥60 years old. Yet even among children, the rate was 34%. When only white patients were analyzed, the linear correlation was better because the 1- to 9-year-old and the 10- to 19-year-old age groups had lower CMV antigenemia rates (data not shown). An age association was not evident for non-allo-SCT patients, owing to the overall lower antigenemia rates (data not shown).
FIG. 1.
Association of age with occurrence of CMV antigenemia among allo-SCT recipients.
Prevalence of anti-CMV antibodies and association with CMV antigenemia.
The presence of the anti-CMV antibody is an indication of prior CMV infection, which is a risk factor for future reactivation. Such antibody data were available for 1,418 non-allo-SCT patients (45.8% of 3,093 patients), 1,131 patients before allo-SCT (87.7% of 1,289 patients), and 466 patients after allo-SCT (36.1% of 1,289 patients). The lower antibody test percentages among patients with non-allo-SCT or after allo-SCT were due to the lack of need or short post-SCT survival.
Antibody prevalence data are shown in Table 5. Consistent with more CMV activity after allo-SCT, the post-allo-SCT group had the highest rates of antibody positivity (88.6%) for all ethnicities combined, and this rate reached 100% for Asians (versus a rate of 87.2% for whites) (P = 0.043). Ethnic differences in antibody positivity rates were more evident in the pre-allo-SCT and the non-allo-SCT groups: they were the lowest for whites and higher for the other groups (P < 0.05 in most comparisons). With or without allo-SCT, women had higher rates than men (P ≤ 0.024 for the non-allo-SCT and pre-allo-SCT groups). Underlying diseases and age had little effect on antibody positivity rates (data not shown). Specifically, patients with multiple myeloma had an antibody positivity rate of 75.2% (185 of 246) (non-allo-SCT and pre-allo-SCT results combined).
TABLE 5.
Prevalence of anti-CMV antibodies by SCT status, ethnicity, and sex
| Category | No. of patients positive for CMV antibody/no. tested (%)
|
P value for post-SCT vs pre-SCT | ||
|---|---|---|---|---|
| Non-SCT and auto-SCT | Pre-allo-SCT | Post-allo-SCTa | ||
| Ethnicity | ||||
| White | 770/987 (78.0) | 621/846 (73.4) | 285/327 (87.2) | <0.001 |
| Black | 129/152 (84.9) | 41/48 (85.4) | 23/26 (88.5) | NSb |
| Asian | 54/64 (84.4) | 54/58 (93.1) | 28/28 (100) | NS |
| Hispanic | 188/215 (87.4) | 146/179 (81.6) | 77/85 (90.6) | 0.059 |
| Sex | ||||
| Male | 600/781 (76.8) | 494/669 (73.8) | 240/275 (87.3) | <0.001 |
| Female | 541/637 (84.9) | 368/462 (79.7) | 173/191 (90.6) | <0.001 |
| P value | <0.001 | 0.024 | NS | |
| Total | 1141/1,418 (80.5) | 862/1,131 (76.2) | 413/466 (88.6) | <0.001 |
Most patients in this category were tested for CMV antibody before SCT.
NS, not significant.
The association of CMV antibody positivity with CMV antigenemia was also evaluated. Antibody-negative patients with non-allo-SCT and allo-SCT showed antigenemia rates of 2.5% (7 of 277) and 8.2% (22 of 269), respectively. In contrast, CMV antigenemia occurred much more frequently among antibody-positive patients (Table 6): 14.3% for non-allo-SCT patients (n = 1141) and 52.8% for allo-SCT patients after transplantation (n = 862). In both groups, Asians had the highest antigenemia rates, whereas whites had the lowest: 24.1% versus 11.9% (P = 0.01) for non-allo-SCT patients, respectively, and 74.1% versus 50.4% (P < 0.001) for allo-SCT patients, respectively. Antibody-positive allo-SCT patients with multiple myeloma had an antigenemia rate of 72.7% (24 of 33), which was higher than that for patients with all other underlying diseases combined (52.0%, 431 of 829; P = 0.019). The antigenemia rates also differed by sex: among antibody-positive non-allo-SCT patients, the rate was significantly higher for men than for women; among allo-SCT patients, the opposite was the case.
TABLE 6.
Frequency of CMV antigenemia among patients who tested positive for CMV antibody
| Category | Non-SCT and auto-SCT patients
|
Allo-SCT patientsb
|
||
|---|---|---|---|---|
| No. of CMV antigenemia-positive patients/no. of antibody-positive patients (%) | RRa (P value) | No. of CMV antigenemia-positive patients/no. of antibody-positive patients (%) | RR (P value) | |
| Ethnicity | ||||
| White | 92/770 (11.9) | 1.0 | 313/621 (50.4) | 1.0 |
| Black | 23/129 (17.8) | 1.49 (0.064) | 25/41 (61.0) | 1.21 (NSc) |
| Asian | 13/54 (24.1) | 2.01 (0.010) | 40/54 (74.1) | 1.47 (<0.001) |
| Hispanic | 35/188 (18.6) | 1.56 (0.016) | 77/146 (52.7) | 1.05 (NS) |
| Sex | ||||
| Male | 99/600 (16.5) | 0.72d (0.024) | 245/494 (49.6) | 1.15d (0.028) |
| Female | 64/541 (11.8) | 210/368 (57.1) | ||
| Total | 163/1,141 (14.3) | 455/862 (52.8) | ||
RR, relative risk.
Number of virus-positive patients after allo-SCT/number of antibody-positive patients before allo-SCT.
NS, not significant.
Female versus male.
Quantitative analyses of CMV-positive cells.
Among the 808 patients with CMV antigenemia, the numbers of CMV-positive cells ranged from 1 to 13,333 cells per 106 WBCs. To gain insight into the factors that influence the viral burden in these patients, a series of quantitative analyses that used the number of CMV-positive cells or the peak value in case of two or more positive tests for a patient were performed (Fig. 2). The number of CMV-positive cells by the antigenemia assay generally correlates with the CMV viral loads (12).
FIG. 2.
Peak values for the numbers of CMV-positive cells per 106 WBCs in relation to (A) SCT status and (B) ethnicity in non-SCT patients. Each dot represents a positive patient's value. Data for patients with negative test results were not included in the analysis. The bars indicate geometric mean.
For the allo-SCT patients (n = 504) and the auto-SCT patients (n = 70), the geometric means of the peak numbers of cells were similar (7.7 positive cells and 7.0 positive cells per 106 WBCs, respectively). In contrast, non-SCT patients (n = 234) had significantly higher peak values (18.7 positive cells per 106 WBCs) than SCT patients (Fig. 2A) (P < 0.001 for both comparisons). This difference could be explained by CMV monitoring and/or prophylaxis in SCT recipients.
Data on the viral burdens among the different ethnic groups were also compared. For allo-SCT and auto-SCT patients combined (owing to similar numbers of positive cells), no significant difference by ethnicity was seen: geometric means were 7.2 positive cells per 106 WBCs for Asians (n = 51), 8.5 positive cells per 106 WBCs for blacks (n = 38), 7.5 positive cells per 106 WBCs for Hispanics (n = 102), and 7.6 positive cells per 106 WBCs for whites (n = 383). Thus, routine CMV prophylaxis probably had a similar effect in controlling the viral burdens in the patients of the different ethnic groups. Non-SCT patients, however, showed remarkable variations by ethnicity (Fig. 2B). Asians had the highest geometric mean number of positive cells (61.0 cells; n = 17), whereas Hispanics had the lowest (9.0 cells; n = 45) (P = 0.001). Blacks and whites also had significantly higher burdens, 28.7 (n = 28) and 18.8 positive cells per 106 WBCs (n = 144), respectively, than Hispanics (P < 0.05 for both comparisons). The difference between the viral burdens of Asians and whites was also significant (P = 0.033). These results suggest that without routine CMV prophylaxis and monitoring, ethnic host factors likely vary in their abilities to control or tolerate the CMV viral burden. The mean ages for these patients were similar for Asians (46.8 years), blacks (47.6 years), and Hispanics (45.8 years) but were older for whites (60.0 years).
Underlying diseases had little effect on the peak viral burden in SCT patients (data not shown). However, non-SCT patients with lymphoid malignancies (acute lymphoblastic leukemia, chronic lymphocytic leukemia, and lymphomas) had the heaviest CMV burden: 11 (6.8%) of 161 of these positive patients had >1,000 to 13,333 positive cells per 106 WBCs (blood volume, ∼0.3 ml), significantly more than in those with nonlymphoid tumors (0 of 73) (χ2 = 5.23; P = 0.022). These patients were all adults (mean age, 42 years; age range, 19 to 73 years) and were of all ethnicities. Overall, the geometric mean peak viral burden was slightly higher in patients with non-SCT lymphoid malignancies than in those with nonlymphoid tumors (20.9 and 14.7 positive cells per 106 WBCs, respectively; t = 1.16; degrees of freedom = 232; P = 0.25).
DISCUSSION
Two epidemiologic aspects of CMV antigenemia in cancer patients were measured in this study: the incidence of antigenemia (scope) and the individual circulating viral burden (magnitude). Several major conclusions can be drawn from the findings, which should be of clinical value for risk assessment and the timely diagnosis and treatment of the infection. First, reactivated CMV antigenemia posed a substantial problem in non-SCT cancer patients, particularly those with lymphoid malignancies and multiple myeloma (Table 1), suggesting insufficient lymphoid control (both humoral and cellular) of the virus in these patients. In addition, the viral burden was higher in these and other non-SCT patients than in allo-SCT and auto-SCT patients (Fig. 2A), which was consistent with the lack or insufficiency of routine monitoring and/or prophylaxis. Therefore, patients with non-SCT lymphoid cancer may need more monitoring for CMV. Second, auto-SCT was not significantly associated with an increased risk of CMV antigenemia, other than that caused by underlying disease, unlike allo-SCT. Thus, most auto-SCT patients had sufficient residual lymphoid function to keep CMV in check. Third, allo-SCT increased the CMV risk by 2.6- to 29.6-fold (overall, 4.0-fold), depending on the initial risk associated with the underlying disease. However, after allo-SCT, the underlying diseases had little effect on the risk, except among those with multiple myeloma. Fourth, remarkable ethnic variations in antigenemia rates were found. Asians had the highest antigenemia rates in most disease categories, with or without SCT, whereas whites had the lowest (Tables 2 and 3). Non-SCT Asian patients also experienced the heaviest viral burden (Fig. 2B).
Consistent with the finding of a high CMV rate among allo-SCT Asian patients (61.1%) (Table 3), a recent study of 154 allo-SCT adult Japanese patients that used a pp65 antigen assay similar to that used in this study found a CMV antigenemia rate of 69.5% (2). Among allo-SCT recipients, two studies (17, 19) have shown that ethnicity plays a role in the risk of graft-versus-host disease, which may in turn affect immune suppression and CMV reactivation. The ethnic comparisons in this study should be valid, in view of the uniformity of the CMV tests (tests for antigenemia and antibodies) and the clinical management used and the stratification of the data analysis. In addition, age did not adversely affect the conclusion because Asians were, on average, 12 years younger than whites, and younger age was associated with less CMV antigenemia (Fig. 1) instead of more. The reasons behind ethnic variations in CMV antigenemia rates are likely multiple. The higher rates of CMV antibody positivity among the Asians and blacks partially explain the results (Table 5). Yet among all antibody-positive patients, Asians and blacks still had higher antigenemia rates (Table 6). Non-SCT Asians and blacks also had higher circulating viral burdens (Fig. 2B). Furthermore, it was unexpected that non-SCT Hispanic patients, despite having higher rates of antigenemia and antibody positivity than whites, had the lowest magnitude of viral burden (Fig. 2B). Together, these data suggest that host factors play a role in ethnic variations in antigenemia rates and viral burden. Host immunogenetic mechanisms that govern humoral and cellular anti-CMV immunity are known to affect CMV reactivation (18).
CMV is a ubiquitous, large, complex virus that coevolves with humans and other primates; it molds with immune systems to establish life-long latent infections with periodic shedding of the virus to sustain passage into new hosts. A recent study with peptides spanning the entire CMV proteome and cytokine flow cytometry found that the human immune system dedicates ∼10% of the memory repertoire of CD4+ and CD8+ T cells to keep the virus in check (21). Thus, normal immunity against CMV is robust. The finding of a low antigenemia rate in myelodysplastic syndrome, a preleukemic, less severe disease, is consistent with this feature (Table 1). Mucosal or epithelial (local) reactivation may occur during subclinical levels of stress, such as during space flight in astronauts (15). CMV antigenemia, on the other hand, represents a systemic form of reactivation that probably occurs only under conditions of severe immunocompromise, as was known previously (18) and seen in this study. Therefore, from the virus-host interaction standpoint, further studies are needed to delineate what host factors, such as human leukocyte antigen alleles, are protective and what are susceptible. This knowledge may lend insight into CMV virology research and vaccine development. The development of a CMV vaccine has become a priority for the U.S. national vaccine strategy to protect against primary or congenital infection in neonates and reactivation in immunocompromised individuals (1).
The reported CMV reactivation rates among auto-SCT patients vary considerably, ranging from 4% for patients with CMV disease (10) and 13% for patients with viremia, viruria, and CMV disease combined (3) to 29% for patients with antigenemia (viremia) (20) and 39% for patients with antigenemia (5). The rate of 12% from this study was at the median. It has been noted that the preparation of autologous stem cells affected CMV reactivation after transplantation (10). The intensity of monitoring for CMV may also affect the detection rate, particularly those with low-level transient positivity for CMV. One study found no need for routine monitoring (3); the data presented here, as being from a larger-scale and longer-duration study, also support this notion. The institutional practice at The University of Texas M. D. Anderson Cancer Center seems to be adequate for auto-SCT.
The higher CMV antigenemia rate for allo-SCT patients with myeloma can be explained, at least partially, by the use of pre-SCT treatment regimens, which frequently include dexamethasone, prednisone, or thalidomide or these drugs in combination. These immunosuppressive agents likely weakened the surveillance for CMV at the subviremic level (potentiation effect), and subsequent allo-SCT brought about further viremia (antigenemia). This effect was most striking in Hispanics (Table 3). Whether a direct association between CMV and multiple myeloma exists is unknown, and it is difficult to imagine how a common childhood infection that is usually subclinical relates to a rare malignancy several decades later. Nonetheless, Buhler et al. (6) recently found, in a small study, that a high rate (40%) of monoclonal gammopathy, a frequent precursor of multiple myeloma, was seen among immunocompetent subjects with primary CMV infection but not among those with Epstein-Barr virus infection. Another study found that CMV protected a myeloma cell line from apoptosis induced by growth factor withdrawal (22).
In the present study, no attempts were made to distinguish CMV antigenemia from CMV disease or infection (the latter is a clinicovirologic correlate) (14). Nonetheless, CMV antigenemia is abnormal, and the circulatory viral burden generally correlates with the degree of severity of CMV disease. In addition, routine anti-CMV prophylaxis, the use of steroids, and comorbidities, particularly in allo-SCT recipients, may also obscure symptoms and signs that would otherwise be attributable to CMV infection. A detailed analysis of the clinical features of CMV antigenemia is in progress. Preliminary data suggest that various clinical manifestations, such as prolonged fever, pneumonitis, heart failure, and retinitis, existed in these patients, particularly those with heavy viral burdens. Therefore, the findings from this study may be a practical alert for pathologists, clinical microbiologists, oncologists, and infectious disease specialists of the risk of CMV antigenemia during the diagnosis and treatment of cancer, particularly those non-SCT patients in whom the risk of CMV antigenemia is less recognized.
Acknowledgments
I thank the staff of the clinical microbiology laboratory for CMV antigenemia and antibody testing over the years, Indra De and Audrey Pham for assistance with data collection, Jeffrey Tarrand and Krishna Komanduri for helpful discussion, and Ann Sutton for editorial assistance.
There is no conflict of interest to declare.
This work was supported in part by a University Cancer Foundation grant from The University of Texas M. D. Anderson Cancer.
Footnotes
Published ahead of print on 7 February 2007.
REFERENCES
- 1.Arvin, A. M., P. Fast, M. Myers, S. Plotkin, and R. Rabinovich. 2004. Vaccine development to prevent cytomegalovirus disease: report from the National Vaccine Advisory Committee. Clin. Infect. Dis. 39:233-239. [DOI] [PubMed] [Google Scholar]
- 2.Asano-Mori, Y., K. Oshima, M. Sakata-Yanagimoto, M. Nakagawa, K. Kandabashi, K. Izutsu, A. Hangaishi, T. Motokura, S. Chiba, M. Kurokawa, H. Hirai, and Y. Kanda. 2005. High-grade cytomegalovirus antigenemia after hematopoietic stem cell transplantation. Bone Marrow Transplant. 36:813-819. [DOI] [PubMed] [Google Scholar]
- 3.Bilgrami, S., J. Aslanzadeh, J. M. Feingold, R. D. Bona, J. Clive, D. Dorsky, R. L. Edwards, and P. L. Tutschka. 1999. Cytomegalovirus antigenemia, viruria and disease after autologous peripheral blood stem cell transplantation: no need for surveillance. Bone Marrow Transplant. 24:69-73. [DOI] [PubMed] [Google Scholar]
- 4.Boeckh, M., T. A. Gooley, D. Myerson, T. Cunningham, G. Schoch, and R. A. Bowden. 1996. Cytomegalovirus pp65 antigenemia-guided early treatment with ganciclovir versus ganciclovir at engraftment after allogeneic marrow transplantation: a randomized double-blind study. Blood 88:4063-4071. [PubMed] [Google Scholar]
- 5.Boeckh, M., T. Stevens-Ayers, and R. A. Bowden. 1996. Cytomegalovirus pp65 antigenemia after autologous marrow and peripheral blood stem cell transplantation. J. Infect. Dis. 174:907-912. [DOI] [PubMed] [Google Scholar]
- 6.Buhler, S., K. Laitinen, H. Holthofer, A. Jarvinen, K. O. Schauman, and K. Hedman. 2002. High rate of monoclonal gammopathy among immunocompetent subjects with primary cytomegalovirus infection. Clin. Infect. Dis. 35:1430-1433. [DOI] [PubMed] [Google Scholar]
- 7.Chemaly, R. F., H. A. Torres, R. Y. Hachem, G. M. Nogueras, E. A. Aguilera, A. Younes, M. A. Luna, G. Rodriguez, J. J. Tarrand, and I. I. Raad. 2005. Cytomegalovirus pneumonia in patients with lymphoma. Cancer 104:1213-1220. [DOI] [PubMed] [Google Scholar]
- 8.Cox, F., and W. T. Hughes. 1975. Cytomegaloantigenemia in children with acute lymphocytic leukemia. J. Pediatr. 87:190-194. [DOI] [PubMed] [Google Scholar]
- 9.Hermouet, S., C. A. Sutton, T. M. Rose, R. J. Greenblatt, I. Corre, R. Garand, A. M. Neves, R. Bataille, and J. W. Casey. 2003. Qualitative and quantitative analysis of human herpesviruses in chronic and acute B cell lymphocytic leukemia and in multiple myeloma. Leukemia 17:185-195. [DOI] [PubMed] [Google Scholar]
- 10.Holmberg, L. A., M. Boeckh, H. Hooper, W. Leisenring, S. Rowley, S. Heimfeld, O. Press, D. G. Maloney, P. McSweeney, L. Corey, R. T. Maziarz, F. R. Appelbaum, and W. Bensinger. 1999. Increased incidence of cytomegalovirus disease after autologous CD34-selected peripheral blood stem cell transplantation. Blood 94:4029-4035. [PubMed] [Google Scholar]
- 11.Junghanss, C., M. Boeckh, R. A. Carter, B. M. Sandmaier, M. B. Maris, D. G. Maloney, T. Chauncey, P. A. McSweeney, M. T. Little, L. Corey, and R. Storb. 2002. Incidence and outcome of cytomegalovirus infections following nonmyeloablative compared with myeloablative allogeneic stem cell transplantation, a matched control study. Blood 99:1978-1985. [DOI] [PubMed] [Google Scholar]
- 12.Li, H., J. S. Dummer, W. R. Estes, S. Meng, P. F. Wright, and Y. W. Tang. 2004. Measurement of human cytomegalovirus loads by quantitative real-time PCR for monitoring clinical intervention in transplant recipients. J. Clin. Microbiol. 41:187-191. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Ljungman, P., R. de La Camara, N. Milpied, L. Volin, C. A. Russell, A. Crisp, A. Webster, et al. 2002. Randomized study of valacyclovir as prophylaxis against cytomegalovirus reactivation in recipients of allogeneic bone marrow transplants. Blood 99:3050-3056. [DOI] [PubMed] [Google Scholar]
- 14.Ljungman, P., P. Griffiths, and C. Paya. 2002. Definitions of cytomegalovirus infection and disease in transplant recipients. Clin. Infect. Dis. 34:1094-1097. [DOI] [PubMed] [Google Scholar]
- 15.Mehta, S. K., R. P. Stowe, A. H. Feiveson, S. K. Tyring, and D. L. Pierson. 2000. Reactivation and shedding of cytomegalovirus in astronauts during spaceflight. J. Infect. Dis. 182:1761-1764. [DOI] [PubMed] [Google Scholar]
- 16.Nicholson, V. A., E. Whimbey, R. Champlin, D. Abi-Said, D. Przepiorka, J. Tarrand, K. Chan, G. P. Bodey, and J. M. Goodrich. 1997. Comparison of cytomegalovirus antigenemia and shell vial culture in allogeneic marrow transplantation recipients receiving ganciclovir prophylaxis. Bone Marrow Transplant. 19:37-41. [DOI] [PubMed] [Google Scholar]
- 17.Oh, H., F. R. Loberiza Jr., M. J. Zhang, O. Ringden, H. Akiyama, T. Asai, S. Miyawaki, S. Okamoto, M. M. Horowitz, J. H. Antin, A. Bashey, J. M. Bird, M. H. Carabasi, J. W. Fay, R. P. Gale, R. H. Giller, J. M. Goldman, G. A. Hale, R. E. Harris, J. Henslee-Downey, H. J. Kolb, M. R. Litzow, P. L. McCarthy, S. M. Neudorf, D. G. Serna, G. Socie, P. Tiberghien, and A. J. Barrett. 2005. Comparison of graft-versus-host-disease and survival after HLA-identical sibling bone marrow transplantation in ethnic populations. Blood 105:1408-1416. [DOI] [PubMed] [Google Scholar]
- 18.Pass, R. F. 2001. Cytomegalovirus, p. 2675-2705. In D. M. Knipe, P. M. Howley, D. E. Griffin, M. A. Martin, R. A. Lamb, and B. Roizman (ed.), Fields virology, 4th ed. Lippincott Williams & Wilkins, Philadelphia, PA.
- 19.Remberger, M., J. Aschan, B. Lonnqvist, S. Carlens, B. Gustafsson, P. Hentschke, S. Klaesson, J. Mattsson, P. Ljungman, and O. Ringden. 2001. An ethnic role for chronic, but not acute, graft-versus-host disease after HLA-identical sibling stem cell transplantation. Eur. J. Haematol. 66:50-56. [DOI] [PubMed] [Google Scholar]
- 20.Rossini, F., E. Terruzzi, S. Cammarota, F. Morini, M. Fumagalli, I. Verga, E. Elli, M. Verga, I. Miccolis, M. Parma, and E. M. Pogliani. 2005. Cytomegalovirus infection after autologous stem cell transplantation: incidence and outcome in a group of patients undergoing a surveillance program. Transplant Infect. Dis. 7:122-125. [DOI] [PubMed] [Google Scholar]
- 21.Sylwester, A. W., B. L. Mitchell, J. B. Edgar, C. Taormina, C. Pelte, F. Ruchti, P. R. Sleath, K. H. Grabstein, N. A. Hosken, F. Kern, J. A. Nelson, and L. J. Picker. 2005. Broadly targeted human cytomegalovirus-specific CD4+ and CD8+ T cells dominate the memory compartments of exposed subjects. J. Exp. Med. 202:673-685. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Wei, G. Q., M. F. Lin, H. Huang, and Z. Cai. 2004. Human cytomegalovirus protects multiple myeloma cell line KM3 cells from apoptosis induced by growth factor withdrawal. Chin. Med. J. 117:903-907. [PubMed] [Google Scholar]