Abstract
BACKGROUND
The objectives of this study were to determine i) the prevalence and the copy numbers of oral human papilloma virus type 16 (HPV-16) in HIV-infected subjects compared with non-HIV controls, and ii) the effects of antiretroviral therapy (ART) and its duration on the virus.
METHODS
A cross-sectional study was performed in HIV-infected subjects with and without ART, and non-HIV individuals. Saliva samples were collected and the DNA extracted from those samples was used as a template to detect HPV-16 E6 and E7 by quantitative polymerase chain reaction. Student t-test and ANOVA test were performed to determine the prevalence rates among groups.
RESULTS
Forty-nine HIV-infected subjects; 37 on ART (age range 23–54 yr, mean 37 yr), 12 not on ART (age range 20–40 yr, mean 31 yr), and 20 non-HIV controls (age range 19–53 yr, mean 31 yr) were enrolled. The prevalence of oral HPV-16 infection and the copy numbers of the virus were significantly higher in HIV-infected subjects than non-HIV controls when using E6 assay (geometric mean =10,696 vs. 563 copies/105 cells, p<0.001), but not E7 assay. No significant difference was observed between those who were and were not on ART. Long-term use of ART did not significantly change the prevalence of oral HPV-16 infection and the copy numbers of the virus (p=0.567).
CONCLUSION
We conclude that the prevalence of oral HPV-16 infection and the copy numbers of the virus are increased by HIV infection. Neither the use of ART nor its duration significantly affected the virus.
Keywords: Antiretroviral therapy, HIV, Oncogenic virus, Oral human papilloma virus type 16, Saliva
Introduction
Human papillomaviruses (HPVs) are a group of 7.9 kb double-stranded circular DNA viruses that are classified into two groups; low risk and high risk types (1, 2). High-risk species including HPV-16 are usually involved in epithelial carcinogenesis and found in premalignant and malignant lesion (2). Substantial molecular evidence has suggested that HPV-16 is a high risk genotype that plays an important role in the pathogenesis of a subset of head and neck squamous cell carcinoma (HNSCC) (3). Previous studies have shown that HPV-16 is identified in 90% of HPV associated HNSCC (4), and in 50% of oropharyngeal SCC (4, 5, 6).
The prevalence and incidence of HPVs infection and HPVs-associated diseases including oral SCC have been shown to be greater in HIV-infected subjects when compared to non-HIV subjects (7, 8). A previous study by Chuang et al. (9) reported that patients with HPV-16 positive surveillance salivary rinses are at high risk for development of recurrence and distant metastasis of HNSCC. This finding may represent an immunologic impairment that contributes to cancer development and subsequent recurrence and metastasis.
Antiretroviral therapy (ART) is the standard treatment of HIV-infection, which consists of a combination of three or four drug groups including nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), integrase inhibitors (INIs), and fusion inhibitors (FIs). Since they are administered for long periods of time, combinations of three ART are usually prescribed simultaneously to minimize viral resistance to the drugs (10). The following combinations are commonly prescribed: one NNRTI + two NRTIs; one or two PIs + two NRTIs; and three NRTIs.
It is well accepted that ART decreased the prevalence of opportunistic diseases, and improved the quality of life of HIV-infected subjects (11). However, an increased risk for malignancy of different organs including oropharynx has been observed among the subjects even in the ART era (12, 13). Previous studies reported an increased prevalence of oral HPV infection in HIV-infected subjects after the initiation of ART (14). In addition, ART increased the prevalence of HPV-associated oral cancers (15). HIV-infected subjects received ART as a life-long therapy. Thus, it is important to determine the effects of long-term use of ART on oral HPVs infection. Since malignant transformation caused by HPV-16 is mediated through the expression of E6 and E7, we, therefore, focused on the detection of HPV-16 E6 and E7 in our study. The objectives of this study were to determine 1) the prevalence and the copy numbers of oral HPV-16 in a group of HIV-infected subjects compared with non-HIV controls, and 2) the effects of ART and its duration on the prevalence of oral HPV-16 in HIV-infected subjects.
Materials and methods
Subjects
A cross-sectional study was performed in HIV-infected subjects who came to receive ART at the Internal Medicine Clinic at Songklanagarind Hospital and Hat Yai Regional Hospital in southern Thailand. The inclusion criteria of subjects enrolled were i) seropositive for antibody to HIV when tested with a particle agglutination test for antibodies to HIV (SERODIA®-HIV, Fujirebio Inc., Shinjuku-ku, Tokyo, Japan) and enzyme-linked immunosorbent assay (ELISA) (Enzygnost® Anti-HIV ½ Plus, Behring, Behringwerke AG, Marburg, Germany), ii) currently taking ART, and iii) willing to participate in the study. The exclusion criteria were i) HIV-infected subject with history of local radiation therapy on head and neck region; ii) HIV-infected subject with any other immune deficiency diseases; iii) severely ill HIV-infected subject who could not cooperate with the study procedures of saliva collection. HIV-infected individuals who came to those hospitals but had not yet started ART and did not have any other immune disorders, and non-HIV infected volunteer were asked to participate as controls.
Sample size was calculated from the following formula:
where n = sample size, σ = standard deviation, δ = mean difference, Zα/2 and Zβ denote the corresponding percentiles of the standard normal distributions.
n = 2 [(1.96 + 0.84) × 30/40]2
n = 9
Ethics
The study protocol was approved by the research committee at the Prince of Songkla University, and at the Ministry of Public Health. All information about the patients and their identity were anonymous. Subjects were given both verbal and written information about the nature of the study and written consent obtained. They were allowed to leave the study at any time during the procedures.
Clinical examination
History taking and oral examination were performed in HIV-subjects with and without ART and non-HIV individuals. Clinical diagnosis of HIV-related oral lesions was made according to the criteria classified by the EC-Clearinghouse (16).
The following data were recorded; use of ART, CD4+ cell count, HIV viral load, smoking habit and alcohol consumption.
Saliva collection
All subjects were prohibited from smoking, eating, drinking, or brushing their teeth for 1 hour before collecting the saliva. Paraffin-stimulated saliva samples were collected as previously described (17).
DNA extraction
DNA in saliva samples was extracted by using QIAamp DNA extraction kit (Qiagen, Hilden, Germany) and used as a template to detect HPV E6 and E7 by quantitative polymerase chain reaction (Q-PCR). Cases with HPV loads ≥0 were supposed to be positive and an HPV load equal of 0 was supposed to indicate a negative case.
PCR amplification and quantification of HPV DNA
Q-PCR to detect HPV DNA was performed using an ABI Prism 7300 machine (Applied Biosystems, Carlsbad, CA, USA) available at the Scientific Equipment Center, Prince of Songkla University. Each sample was tested in duplicate in an assay with primers specific for E6 and E7 using TaqMan probes as shown in Table 1.
Table 1.
Sequences of primers and probes used to detect HPV DNA by quantitative polymerase chain reaction
| HPV-16 E6 |
| Forward primer, 5′-TCAGGACCCACAGGAGCG-3′ |
| Reverse primer, 5′-CCTCACGTCGCAGTAACTGTTG-3′ |
| Probe, 5′-(FAM)- CCCAGAAAGTTACCACAGTTATGCACAGAGCT-(TAMRA)-3′ |
| HPV-16 E7 |
| Forward primer, 5′-CCGGACAGAGCCCATTACAA-3′ |
| Reverse primer, 5′-CGAATGTCTACGTGTGTGCTTTG-3′ |
| Probe, 5′-(FAM)-CGCACAACCGAAGCGTAGAGTCACACT-(TAMRA)-3′ |
| β-actin |
| Forward primer, 5′-TCACCCACACTGTGCCCATCTACGA-3′ |
| Reverse primer, 5′-CAGCGGAACCGCTCATTGCCAATGG-3′ |
| Probe, 5′-(FAM)-ATGCCCTCCCCCATGCCATCCTGCGT-(TAMRA)-3′ |
In brief, 20 μg of DNA was added to PCR master mix containing 2× of DyNAmo Flash Probe Master (Finnzyme, Espoo, Finland), 20 μM of each primers, 20 μM TaqMan probes, and 6 μM distilled water. Initial denaturation occurred at 95°C for 7 min, followed by 40 cycles: 5s at 95°C, 30s at 60°C. A final extension was done at 72°C for 5 min.
Standardization
Quantitation of standard recombinant DNA was created from recombinant plasmids of E6 and E7 amplicons obtained from the DF/HCC DNA Resource Core, the Harvard Institute of Proteomics, Harvard Medical School, USA. Their recombinant plasmids were confirmed by PCR gel electrophoresis. The amount of the recombinant plasmid was measured by spectrophotometer and calculated the copies using the following formula:
n = base pair of 1 copy of a recombinant plasmid
The standard curve was created by ten-fold serial dilution from 104 to 109 copies of each standard recombinant plasmid. β-actin was used as a housekeeping gene (2 copies/genome) using the same serial dilutions of the plasmid.
Statistical analysis
Estimates of the prevalence of oral HPV were expressed in percentage and 95% confidence interval. Comparison of the prevalence rates among groups was performed using Student t-test and ANOVA test on logarithmic transformation of the values. Factors associated with the levels of oral HPV were identified using univariate and multivariate analyses.
Results
Demographic data and medical status
Stimulated saliva were collected from four groups of subjects as follows: Group I: non HIV-infected controls (n=20) (13 Male, 7 Female, age range 19–53 years, mean age 31 years), Group II: HIV-infected subjects who did not receive ART (n=12) (8 Male, 4 Female, age range 20–40 years, mean age 31 years), Group III: HIV-infected subjects who received short-term ART (< 3 yr) (n=19) (10 Male, 9 Female, age range 23–54 years, mean age 36 years), and Group IV: HIV-infected subjects who received long-term ART (≥ 3 yr) (n=18) (6 Male, 12 Female, age range 32–50 years, mean age 39 years). No oral lesion associated with HPV infection was observed. The most common combination of ART used among HIV-infected subjects was 2 NRTIs + 1 NNRTI.
Demographic data and medical status of the subjects are shown in Table 2.
Table 2.
Demographic data and medical status of subjects that saliva samples were obtained
| Variables | HIV-infected subjects
|
Non-HIV subjects | ||
|---|---|---|---|---|
| No ART (n=12) | With ART
|
|||
| Short-term ART | Long-term ART | |||
|
| ||||
| Age | ||||
| Age range (year) | 20–40 | 23–54 | 32–50 | 19–53 |
| Mean age (year) | 31 | 36 | 39 | 31 |
|
| ||||
| Gender | ||||
| Male | 8 (67%) | 10 (53 %) | 6 (33%) | 7 (35%) |
| Female | 4 (33%) | 9 (47%) | 12 (67%) | 13 (65%) |
|
| ||||
| Smoking habit | ||||
| Smoker | 4 (33%) | 6 (32%) | 7 (39%) | 7 (35%) |
| Non-smoker | 8 (67%) | 13 (68%) | 11 (61%) | 13 (65%) |
|
| ||||
| Alcohol consumption | ||||
| Drinker | 4 (33%) | 5 (26%) | 3 (17%) | 11 (55%) |
| Non-drinker | 8 (67%) | 14 (74%) | 15 (83%) | 9 (45%) |
|
| ||||
| Oral hygiene | ||||
| Good | 0 (0%) | 2 (10%) | 0 (0%) | 1 (5%) |
| Fair | 7 (58%) | 10 (53%) | 9 (50%) | 12 (60%) |
| Poor | 5 (42%) | 7 (37%) | 9 (50%) | 7 (35%) |
|
| ||||
| Oral lesiona | ||||
| Yes | 9 (75%) | 10 (53%) | 10 (56%) | 5 (25%) |
| No | 3 (25%) | 9 (47%) | 8 (44%) | 15 (75%) |
|
| ||||
| Use of ART | ||||
| 2NRTIs + 1 NNRTI | - | 18 (95%) | 14 (78%) | - |
| 2NRTIs + 2PIs | - | 1 (5%) | 1 (6%) | - |
| Others | - | 0 (0%) | 3 (16%) | - |
|
| ||||
| CD4+ cell count (cell/mm3) | ||||
| Geometric mean | 126 | 140 | 465 | - |
| Range | 6–580 | 9–600 | 184–1,214 | - |
|
| ||||
| HIV viral load (copies) | ||||
| Geometric mean | 0 | 0 | 0 | - |
| Range | 0–14,800 | 0–750,000 | 0–24,600 | - |
No oral lesion associated with human papilloma virus (HPV) was observed. ART, antiretroviral therapy; NRTIs, nucleoside reverse transcriptase inhibitors; NNRTIs, non-nucleoside reverse transcriptase inhibitors; PIs, protease inhibitors.
PCR amplification and quantification of HPV DNA
Prevalence of oral HPV-16 infection detected by E6 assay was significantly higher in HIV-infected subjects than non-HIV controls (Table 3). However, no significant difference was observed when using E7 assay. The prevalence was not significantly affected by use of ART. In addition, no significant difference was observed between those who received short-term and long-term ART.
Table 3.
Prevalence of oral HPV-16 in each subject group
| Group | Prevalence
|
|||
|---|---|---|---|---|
| HPV-16 E6 | p-value | HPV-16 E7 | p-value | |
|
| ||||
| Non-HIV (n=20) | 9 (49%) | 0.024 | 8 (40%) | 0.108 |
| HIV (n=49) | 37 (76%) | 31 (63%) | ||
|
| ||||
| HIV-no ART (n=12) | 8 (67%) | 0.454 | 7 (58%) | 0.738 |
| HIV-ART (n=37) | 29 (78%) | 24 (65%) | ||
|
| ||||
| Short-term ART (n=19) | 14 (74%) | 0.692 | 15 (79%) | 0.091 |
| Long-term ART (n=18) | 15 (83%) | 9 (50%) | ||
ART, antiretroviral therapy; HPV, human papillomavirus.
Tables 4 and 5 show that HIV-infected subjects had significantly higher copy numbers of oral HPV-16 than non-HIV controls. Use of ART and its duration did not significantly affect the copy numbers of the virus. By using HPV-16 E6 assay, however, HIV-infected subjects who were on ART had relatively higher copy numbers of the virus than those who were not on the medication (geometric mean= 11,138 vs. 9,239 copies/105 cells, p=0.912). Long-term ART seemed to increase the number of HPV-16 E6 (Table 4). In contrast, by using HPV-16 E7 assay, HIV-infected subjects who were on ART showed relatively lower copy numbers of the virus than those who were not on the medication (geometric mean= 6,980 vs. 16,595 copies/105 cells, p=0.569). Long-term ART seemed to decrease the copy numbers of HPV-16 E7 (Table 5).
Table 4.
Geometric mean of HPV-16 copy number of each subject group using HPV-16 E6 primers
| HPV-16 status | Group | n (%) | Geometric mean (copies/105 cells) | 95% CI
|
p-value | |
|---|---|---|---|---|---|---|
| lower | upper | |||||
|
| ||||||
| HPV-16 negative | non-HIV | 11/23 (48%) | 0 | - | - | - |
| HIV | 12/23 (52%) | 0 | - | - | ||
|
| ||||||
| HPV-16 positive | non-HIV | 9/46 (20%) | 563 | 229 | 1,386 | <0.001 |
| HIV | 37/46 (80%) | 10,696 | 3,067 | 37,304 | ||
|
| ||||||
| HIV-no ART | 8/37 (22%) | 9,239 | 498 | 171,338 | 0.912 | |
| HIV-ART | 29/37 (78%) | 11,138 | 2,822 | 391,913 | ||
|
| ||||||
| short-term ART | 14/29 (48%) | 7,227 | 783 | 66,703 | 0.567 | |
| long-term ART | 15/29 (52%) | 16,677 | 2,617 | 106,262 | ||
ART, antiretroviral therapy; HPV, human papillomavirus.
Table 5.
Geometric mean of HPV-16 copy number of each subject group using HPV-16 E7 primers
| HPV-16 status | Group | n (%) | Geometric mean (copies/105 cells) | 95% CI
|
p-value | |
|---|---|---|---|---|---|---|
| lower | upper | |||||
|
| ||||||
| HPV-16 negative | non-HIV | 12/30 (40%) | 0 | - | - | - |
| HIV | 18/30 (60%) | 0 | - | - | ||
|
| ||||||
| HPV-16 positive | non-HIV | 8/39 (21%) | 454 | 66 | 3,142 | 0.026 |
| HIV | 31/39 (79%) | 8,487 | 2,562 | 28,112 | ||
|
| ||||||
| HIV-no ART | 7/31 (23%) | 16,595 | 1,322 | 208,310 | 0.569 | |
| HIV-ART | 24/31 (77%) | 6,980 | 1,758 | 27,712 | ||
|
| ||||||
| short-term ART | 15/24 (63%) | 14,728 | 2,599 | 83,475 | 0.170 | |
| long-term ART | 9/24 (37%) | 2,011 | 297 | 13,625 | ||
ART, antiretroviral therapy; HPV, human papillomavirus.
Factors associated with the levels of oral HPV-16
On univariate analysis, several factors including CD4+ cell count, HIV viral load, alcohol consumption, smoking, and age showed some correlations with the levels of oral HPV-16 detected. HIV-infected subjects with older age had significantly higher levels of HPV-16 in saliva than those who were younger. Sex was not found to be associated with the levels of the virus. No significant association between types of ART prescribed and the levels of oral HPV-16 was observed. Duration of ART was not found to be significantly associated with the levels of the virus. On multivariate analysis, no significant risk factor associated with the levels of oral HPV-16 was observed among the subjects.
Discussion
In this study, Q-PCR assay was used to detect HPV-16 E6 and E7 in saliva. Prevalence of oral HPV-16 infection was found to be significantly higher in HIV-infected subjects than non-HIV-controls. However, use of ART and its duration did not significantly affect the prevalence and the copy numbers of the virus.
Interestingly, the copy numbers of HPV-16 E6 were increased but HPV-16 E7 seemed to be decreased in HIV-infected subjects who received ART compared with those who did not. The different findings between E6 and E7 assays may be due to the fact that the immune system can produce anti-E7 protein but not for E6 protein (15). Therefore, the copy numbers of HPV-16 E7 detected were lower than those of E6.
High prevalence of HPV infection was reported in HIV-infected subjects compared to non-HIV individuals (7). It is not clear whether there are any direct interactions between HIV and HPV. It has been reported that HIV-tat gene, which encodes a transactivator protein, can transactivate HPV long control region and increase HPV E7, E1, and L1 expression (8, 18, 19). Tat also increases HPV shedding (8). Of interest, it was shown that HIV did not only increase the expression of E6 and E7 oncoproteins in HPV16-positive oral keratinocytes but also enhance the proliferative capacity of the cells (8, 19). Thus, HIV may play a crucial role in the HPV-associated pathogenesis by exhorting oncogenic stimulus via tat protein.
The findings of higher prevalence of HPV among HIV-infected subjects than non-HIV individuals were consistent with those reported by others (14, 20). However, the prevalence of HPV detected in the study performed by Cameron et al (2005) was lower than that in the present study. The difference in races of the subjects enrolled may be the reason for that (14). The difference may also be due to the chosen sampling method (swabs of 3 oral sites vs whole saliva collection). Previous reports have indicated that mucosal scrapes of three separate sites or buccal mucosal biopsy provide an incomplete analysis of total oral HPV infection (14, 21).
It should be noted that despite high prevalence of oral HPV-16 infection observed in the present study, no oral lesions associated with the virus were seen. Although clinically healthy oral mucosa can also be infected with HPV-16, the significance of latent oral HPV-infection is unknown (15). Based on the literature, the prevalence of asymptomatic oral HPV infection varies between 11% to 25% (22). This wide variation has been explained by differences in sampling and HPV testing methods (23).
It has been reported that persons with HIV/AIDS have an increase risk of oropharyngeal cancer two to six folds compared with general population (7). Orophalyngeal cancer including oral SCC can occur as a result of oral HPV infection (13). Epidemiologic data support the view that HIV-infected individuals are at higher risk for HPV-associated oral SCC (7, 8). Subjects who have high levels of oral HPV-16 may have an increase risk of oral cancers associated with HPV-16 infection. Thus, levels of HPV-16 in saliva may be a useful marker to early detect HIV-infected subjects who are at risk for developing HPV-related oral SCC.
In this study, no significant difference in oral HPV-16 infection was observed among HIV-infected subjects who received ART compared with those who did not. These findings were consistent with a previous study by Cameron et al., (14). In contrast, other studies from developing countries revealed that oral HPV infections have become more prevalent since HAART era (13, 24). The risk remained significant even when CD4+ cell count and HIV viral load were adjusted (13). In addition, a study by Greenspan et al (25) reported that there was a significant increase in oral warts among HIV-infected patients who were on HAART or ART. These inconsistent findings may be due to the differences in races and HAART regimens used in those studies.
With respect to duration of ART use, no significant difference was observed in the copy numbers of oral HPV-16 between those who were on short-term and long-term ART. This result was different from other reports (13, 14, 25, 26). The difference may be due to the more frequent use of PI in the previous studies than in the present study. PI may affect epithelial differentiation and proliferation leading to oral warts and/or HPV associated-cancers (13, 26).
In univariate analysis, several factors including CD4+ cell count, HIV viral load, alcohol consumption, smoking, and age, were found to be associated with the copy numbers of oral HPV-16. However, the association was not observed when those factors were adjusted in multivariate analysis. This might be because HIV infection was the strong risk factor for HPV-16 infection and that the effects of those factors were masked by the effects of HIV.
The strength of this study was that it used a highly sensitive Q-PCR method to detect oral HPV-16 that may present at a relatively low copy numbers in saliva. The study demonstrated that saliva is a good sample to detect oral HPV-16. This is because the virus infects oral epithelial cells and is regularly shed during the process of cell differentiation.
The present study has some limitations because it was conducted as a cross-sectional study. It lacked the information of changes in the copy numbers of oral HPV-16 overtime in those subjects who were on long-term use of ART. Thus, longitudinal studies should be performed in the future to better demonstrate the effects of long-term use of ART on the prevalence of oral HPV-16. Another limitation of this study is that the information regarding subjects’ sexual behaviors is lacking. Although a previous study reported that there is no association between oral sex and oral HPV detection in oral mucosa (27), oral sex has been associated with oral HPV infection and with head and neck cancers (28). Thus, oral sex behavior of the subjects might affect the prevalence and the copy numbers of the virus detected in this study.
In conclusion, the findings of this study suggest that the prevalence of oral HPV-16 infection and the copy numbers of the virus were significantly higher in HIV-infected subjects than non-HIV controls. No significant difference was observed between those who were and were not on ART. Long-term use of ART did not significantly affect the prevalence and the copy numbers of HPV-16.
Acknowledgments
Ms. Korntip Amornthatree was a graduate student in Biomedical Sciences at the Faculty of Medicine, Prince of Songkla University. Subject recruitment and saliva collection were supported by NIH/NIDCR grant R21-DE-018340 (to Prof. Dr. Wipawee Nittayananta). Laboratory investigations were supported by a research grant from Prince of Songkla University. We thank Ms. Jintana Pradutkanchana and Ms. Welawee Chaiyaphan for technical assistance.
References
- 1.Campisi G, Panzarella V, Giuliani M, et al. Human papillomavirus: its identity and controversial role in oral oncogenesis, premalignant and malignant lesions. Int J Oncol. 2007;30:813–23. [PubMed] [Google Scholar]
- 2.Ha PK, Pai SI, Westra WH, et al. Real-time quantitative PCR demonstrates low prevalence of human papillomavirus type 16 in premalignant and malignant lesions of the oral cavity. Clin Cancer Res. 2002;8:1203–9. [PubMed] [Google Scholar]
- 3.McKaig RG, Baric RS, Olshan AF. Human papillomavirus and head and neck cancer: epidemiology and molecular biology. Head Neck. 1998;20:250–65. doi: 10.1002/(sici)1097-0347(199805)20:3<250::aid-hed11>3.0.co;2-o. [DOI] [PubMed] [Google Scholar]
- 4.Gillison ML, Koch WM, Capone RB, et al. Evidence for a causal association between human papillomavirus and a subset of head and neck cancers. J Natl Cancer Inst. 2000;92:709–20. doi: 10.1093/jnci/92.9.709. [DOI] [PubMed] [Google Scholar]
- 5.Fouret P, Monceaux G, Temam S, Lacourreye L, St Guily JL. Human papillomavirus in head and neck squamous cell carcinomas in nonsmokers. Arch Otolaryngol Head Neck Surg. 1997;123:513–6. doi: 10.1001/archotol.1997.01900050063008. [DOI] [PubMed] [Google Scholar]
- 6.Paz IB, Cook N, Odom-Maryon T, Xie Y, Wilczynski SP. Human papillomavirus (HPV) in head and neck cancer. An association of HPV 16 with squamous cell carcinoma of Waldeyer’s tonsillar ring. Cancer. 1997;79:595–604. doi: 10.1002/(sici)1097-0142(19970201)79:3<595::aid-cncr24>3.0.co;2-y. [DOI] [PubMed] [Google Scholar]
- 7.Palefsky J. Human papillomavirus-related disease in people with HIV. Curr Opin HIV AIDS. 2009;4:52–6. doi: 10.1097/COH.0b013e32831a7246. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Kim RH, Yochim JM, Kang MK, Shin KH, Christensen R, Park NH. HIV-1 Tat enhances replicative potential of human oral keratinocytes harboring HPV-16 genome. Int J Oncol. 2008;33:777–82. [PubMed] [Google Scholar]
- 9.Chuang AY, Chuang TC, Chang S, et al. Presence of HPV DNA in convalescent salivary rinses is an adverse prognostic marker in head and neck squamous cell carcinoma. Oral Oncol. 2008;44:915–9. doi: 10.1016/j.oraloncology.2008.01.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Ho DD. Time to hit HIV, early and hard. N Engl J Med. 1995;333:450–1. doi: 10.1056/NEJM199508173330710. [DOI] [PubMed] [Google Scholar]
- 11.Charkraborty N, Bhattacharyya S, De C, et al. Incidence of multiple Herpesvirus infection in HIV seropositive patients, a big concern for Eastern Indian scenario. Virol J. 2010;7:147. doi: 10.1186/1743-422X-7-147. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Clifford GM, Polesel J, Rickenbach M, et al. Cancer Risk in the Swiss HIV Cohort Study: Associations with Immunodeficiency, Smoking, and Highly Active Antiretroviral Therapy. J Natl Cancer Inst. 2005;97:425–32. doi: 10.1093/jnci/dji072. [DOI] [PubMed] [Google Scholar]
- 13.Gillison ML. Oropharyngeal cancer: a potential consequence of concomitant HPV and HIV infection. Curr Opin Oncol. 2009;21:439–44. doi: 10.1097/CCO.0b013e32832f3e1b. [DOI] [PubMed] [Google Scholar]
- 14.Cameron JE, Mercante D, O’Brien M, et al. The impact of highly active antiretroviral therapy and immunodeficiency on human papillomavirus infection of the oral cavity of human immunodeficiency virus-seropositive adults. Sex Transm Dis. 2005;32:703–9. doi: 10.1097/01.olq.0000175398.34610.2e. [DOI] [PubMed] [Google Scholar]
- 15.Syrjänen S. Human papillomavirus infection and its association with HIV. Adv Dent Res. 2011;23:84–9. doi: 10.1177/0022034511399914. [DOI] [PubMed] [Google Scholar]
- 16.EC-Clearinghouse on Oral Problems Related to HIV Infection and WHO Collaborating Centre on Oral Manifestations of the Immunodeficiency Virus. Classification and diagnostic criteria for oral lesions in HIV infection. J Oral Pathol Med. 1993;22:289–91. [PubMed] [Google Scholar]
- 17.Nittayananta W, Talungchit S, Jaruratanasirikul S, et al. Effects of long-term use of HAART on oral health status of HIV-infected subjects. J Oral Pathol Med. 2010;39:397–406. doi: 10.1111/j.1600-0714.2009.00875.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Tornesello ML, Buonaguro FM, Beth-Giraldo E, Giraldo G. Human immunodeficiency virus type 1 tat gene enhances human papillomavirus early gene expression. Intervirology. 1993;36:57–64. doi: 10.1159/000150322. [DOI] [PubMed] [Google Scholar]
- 19.Nyagol J, Leucci E, Onnis A, et al. The effects of HIV-1 Tat protein on cell cycle during cervical carcinogenesis. Cancer Biol Ther. 2006;5:684–90. doi: 10.4161/cbt.5.6.2907. [DOI] [PubMed] [Google Scholar]
- 20.Coutlee F, Trottier A-M, Ghattas G, et al. Risk Factors for Oral Human Papillomavirus in Adults Infected and Not Infected With Human Immunodeficiency Virus. Sex Transm Dis. 1997;24:23–31. doi: 10.1097/00007435-199701000-00006. [DOI] [PubMed] [Google Scholar]
- 21.Lawton G, Thomas S, Schonrock J, Monsour F, Frazer I. Human papillomaviruses in normal oral mucosa: a comparison of methods for sample collection. J Oral Pathol Med. 1992;21:265–9. doi: 10.1111/j.1600-0714.1992.tb01008.x. [DOI] [PubMed] [Google Scholar]
- 22.Syrjänen KJ, Syrjänen SM. Papillomavirus infection in human pathology. London: Wiley; 2000. [Google Scholar]
- 23.Kellokoski JK, Syrjänen SM, Chang F, Yliskoski M, Syrjänen KJ. Southern blot hybridization and PCR in detection of oral human papillomavirus (HPV) infections in women with genital HPV infections. J Oral Pathol Med. 1992;21:459–64. doi: 10.1111/j.1600-0714.1992.tb00975.x. [DOI] [PubMed] [Google Scholar]
- 24.Patton LL, McKaig R, Strauss R, Rogers D, Eron JJ., Jr Changing prevalence of oral manifestations of human immuno-deficiency virus in the era of protease inhibitor therapy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000;89:299–304. doi: 10.1016/s1079-2104(00)70092-8. [DOI] [PubMed] [Google Scholar]
- 25.Greenspan D, Canchola AJ, MacPhail LA, Cheikh B, Greenspan JS. Effect of highly active antiretroviral therapy on frequency of oral warts. Lancet. 2001;357:1411–2. doi: 10.1016/S0140-6736(00)04578-5. [DOI] [PubMed] [Google Scholar]
- 26.Danaher RJ, Wang C, Roland AT, Kaetzel CS, Greenberg RN, Miller CS. HIV protease inhibitors block oral epithelial cell DNA synthesis. Arch Oral Biol. 2010;55:95–100. doi: 10.1016/j.archoralbio.2009.12.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Rintala M, Grénman S, Puranen M, Syrjänen S. Natural history of oral papillomavirus infections in spouses: a prospective Finnish HPV Family Study. J Clin Virol. 2006;35:89–94. doi: 10.1016/j.jcv.2005.05.012. [DOI] [PubMed] [Google Scholar]
- 28.D’Souza G, Kreimer AR, Viscidi R, et al. Case-control study of human papillomavirus and oropharyngeal cancer. N Engl J Med. 2007;356:1944–56. doi: 10.1056/NEJMoa065497. [DOI] [PubMed] [Google Scholar]