Abstract
Background
High homology and cross-reactive immune responses have been reported between SARS-CoV-2 and seasonal human coronaviruses (HCoVs). However, the impact of preexisting immunity against seasonal HCoVs on SARS-CoV-2 vaccination is undetermined.
Methods
We conducted a cross-sectional study involving pediatric and adult participants between August 2020 and August 2023. IgG titers against SARS-CoV-2 and seasonal HCoV-229E, -HKU1, -NL63, and -OC43 were quantified by electrochemiluminescent immunoassay. A paired analysis was performed in a subset of participants with samples collected before and after SARS-CoV-2 vaccination.
Results
A total of 1804 participants were enrolled (median age, 44 years; range, 2–95). IgG titers against HCoV-229E, -HKU1, and -OC43 increased during early childhood. Among participants without prior SARS-CoV-2 infection who were SARS-CoV-2-vaccinated, anti-spike IgG titers against SARS-CoV-2 positively correlated with titers against HCoV-OC43, -HKU1, and -NL63 (Spearman r = 0.40, 0.26, and 0.12, respectively; P < .0001, P < .0001, and P = .0002). In paired analysis, participants with high baseline HCoV-HKU1 and -OC43 IgG titers developed higher postvaccination anti-SARS-CoV-2 spike IgG responses than those with low baseline titers (geometric mean [arbitrary units/mL]: 111 384 vs 54 610 and 113 279 vs 50 099; P = .03 and .015). Multivariable linear regression analyses demonstrated that baseline HCoV-HKU1 and -OC43 IgG titers remained independently associated with postvaccination anti-SARS-CoV-2 spike IgG levels (β = 110 592 and 108 855; 95% CI, 17 922–203 262 and 12 013–205 697; P = .020 and .028).
Conclusions
Higher baseline immunity to HCoV-HKU1 and -OC43 was associated with stronger SARS-CoV-2 vaccine–induced antibody responses. These findings suggest that preexisting immunity against seasonal betacoronaviruses may enhance humoral immune response to SARS-CoV-2 vaccination.
Keywords: betacoronaviruses, preexisting immunity, SARS-CoV-2, seasonal coronaviruses, vaccine
A cross-sectional and paired analysis involving pediatric and adult participants found that higher baseline IgG titers to seasonal betacoronaviruses HKU1 and OC43 were associated with stronger antibody responses to SARS-CoV-2 vaccination.
SARS-CoV-2 is a member of the human coronavirus (HCoV) family, which has had significant impact on humanity since its emergence in 2019. In addition to SARS-CoV-2, there are other coronaviruses known to cause human diseases, including SARS-CoV, Middle East respiratory syndrome coronavirus, and seasonal HCoVs [1]. The seasonal HCoVs consist of 2 alphacoronaviruses (HCoV-229E and -NL63) and 2 betacoronaviruses (HCoV-HKU1 and -OC43), which typically cause mild upper respiratory tract infections [1]. Previous studies have shown that primary exposure to seasonal HCoVs typically occurs by 10 years of age, and most adults have detectable serum antibodies indicating prior immunity [2–4].
Closely related viruses with high homology can induce cross-reactive immune responses. Such preexisting cross-reactive immunity can substantially alter immune responses to subsequent infections with closely related viruses, in some cases by enhancing protection [5, 6] but in other cases resulting in worsened disease severity [7, 8]. Given the high degree of homology in structural and nonstructural proteins among HCoVs, particularly among the betacoronaviruses, which include SARS-CoV-2 [1, 9], there has been considerable interest in whether preexisting immunity against seasonal HCoVs affects immune responses to SARS-CoV-2 infection. Multiple large-scale studies have shown that antibodies against seasonal HCoVs, especially HCoV-OC43 and -HKU1, are boosted upon SARS-CoV-2 infection, suggesting cross-reactive immunity [2, 10–17].
Similarly, the impact of preexisting humoral immunity against seasonal HCoVs on SARS-CoV-2 vaccine responses has been of great interest; however, it has been evaluated in only a few studies with conflicting results [2, 4, 18, 19]. The major limitations of these studies were that they were relatively small-scaled, and the participants were predominantly adults who had seasonal HCoV-specific humoral immunity at baseline. As primary immunity against seasonal HCoVs typically occurs in early childhood, it is essential to include participants across a broad age range, including young children, to evaluate the effects of preexisting seasonal HCoV-specific immunity. Understanding the effect of cross-reactive immune responses to SARS-CoV-2 vaccines induced by preexisting immunity against seasonal HCoVs may provide insights in identifying immune epitopes that are conserved between genetically diverse HCoVs, which can potentially contribute to the development of pan-coronavirus vaccines targeting multiple HCoVs. Here, we performed a prospective cross-sectional study including pediatric and adult participants to evaluate the effect of preexisting seasonal HCoV immunity on SARS-CoV-2 vaccine responses.
METHODS
Study Design and Participants
This study utilized data and serum samples from the seroMARK and seroMARK-VR projects, which are prospective cross-sectional studies conducted in Ontario, Canada. The projects were originally planned to investigate SARS-CoV-2 seroprevalence and vaccine responses across diverse racial and ethnic backgrounds, with a focus on a Black Canadian population [20]. Pediatric and adult participants were enrolled regardless of their SARS-CoV-2 infection and vaccination status, and serum samples were collected at a single timepoint between August 2020 and August 2023. Paired serum samples were collected from a subset of participants before and after SARS-CoV-2 vaccination. Research ethics approval was obtained from Clinical Trials Ontario (CTO3274 and 3654), The Hospital for Sick Children (3274-CIA-Aug/2020-42457 and 3654-CIA-Jun/2021-55478), and the London Health Sciences Centre (3274-CIA-Nov/2020-45486 and 3654-CIA-Oct/2021-59895). Demographic data were collected, including age, sex, race and ethnicity, chronic medical conditions (chronic lung disease, heart disease, malignancy, chronic kidney disease, hematologic disease, and metabolic disease), and SARS-CoV-2 vaccination history. SARS-CoV-2 vaccines administered within 7 days prior to blood collection were excluded from the analyses.
Antibody Quantification
Sera were stored at −20 °C or colder until testing. Serum antibody titers were quantified by an electrochemiluminescent immunoassay as previously reported [3]. In summary, a multiplexed chemiluminescent immunoassay (MSD V-PLEX Coronavirus Panel 2, K15369U; Meso Scale Diagnostics) was utilized for the detection of IgG against SARS-CoV-2 spike, receptor-binding domain (RBD), and nucleocapsid, as well as HCoV-229E, -NL63, -HKU1, and -OC43 spike proteins. Assays were performed according to the manufacturer's protocol. Briefly, multispot plates were blocked with MSD Blocker A for 30 minutes and washed, after which they were incubated with reference standard, controls, and diluted serum samples for 2 hours. After another wash, MSD SULFO-TAG Anti-Human IgG detection antibody was added and incubated for an hour, followed by a final wash. MSD Gold Read Buffer B was added, and signals were immediately read by the MSD QuickPlex SQ120 instrument. All incubations were performed at room temperature with shaking at 700 rpm. Wash steps were repeated 3 times with MSD Wash Buffer. Raw data were processed in MSD Discovery Workbench software (version 4.0) and then analyzed in RStudio (version 1.2.5033). Manufacturer-defined cutoff values for SARS-CoV-2–specific IgG were 1960, 5000, and 538 arbitrary units (AU)/mL for anti-spike, -nucleocapsid, and -RBD, respectively. Participants with reactive titers against nucleocapsid and spike/RBD were interpreted as having a history of natural SARS-CoV-2 infection. Since no established thresholds exist for seasonal HCoVs, we defined the 15 percentiles of anti-seasonal HCoV IgG titers as a cutoff to classify participants as having high or low preexisting immunity. This cutoff was selected empirically to capture the lower end of the antibody distribution, representing individuals with relatively low baseline immunity while preserving an adequate sample size for robust statistical comparisons.
Statistical Analyses
Anti-spike IgG titers were compared by Mann-Whitney U test or Kruskal-Wallis test with Dunn's multiple comparisons. Two-sided Spearman rank correlation analyses were performed to evaluate correlations between anti-spike IgG titers against SARS-CoV-2 and seasonal HCoVs following SARS-CoV-2 vaccination. Because the vaccinated participants had varying numbers of vaccine doses, a sensitivity analysis was conducted across subgroups stratified by the number of doses received. A subset of participants (n = 55) had paired serum samples collected before and after SARS-CoV-2 vaccination and remained seronegative for SARS-CoV-2 infection. For this subset, a Friedman test with Dunn's multiple comparisons was used to assess changes in anti-spike IgG titers following vaccination. To investigate the association between baseline seasonal HCoV antibody levels and postvaccination SARS-CoV-2 titers, unadjusted and multivariable linear regression models were performed. Multivariable models were adjusted for age, vaccine dose, and the number of days since the first vaccine dose. Statistical analyses and visualization were conducted in GraphPad Prism (version 10.3.1) or R (version 4.0.2). P values <.05 were considered statistically significant.
RESULTS
Study Population
A total of 2001 individuals were enrolled. After exclusion of participants with missing data on date of birth (n = 124) and SARS-CoV-2 vaccine history (n = 73), 1804 participants were included in the analysis. Participant demographics are summarized in Table 1. The age range was 2 to 95 years (median, 43 years); 5.8% (n = 105) were <10 years old. Ethnic distribution was as follows: Black (67.5%), White (15.0%), Asian (11.1%), and other (6.5%). Serum samples were collected between August 2020 and August 2023. At the timing of sampling, 72.6% of participants had received at least 1 dose of SARS-CoV-2 vaccination. Among vaccinated participants, 95.8% received ≥2 doses and 95.3% received regimens composed only of mRNA vaccines.
Table 1.
Demographics
| SARS-CoV-2 Vaccine, No. (%) | |||
|---|---|---|---|
| Total (n = 1804) | − (n = 495) | + (n = 1309) | |
| Age, y | |||
| Median (range) | 43 (2–95) | 43 (2–85) | 46 (3–95) |
| <10 | 105 (5.8) | 94 (19.0) | 11 (0.8) |
| ≥10, <20 | 204 (11.3) | 87 (17.6) | 117 (8.9) |
| ≥20, <30 | 228 (12.6) | 45 (9.1) | 183 (14.0) |
| ≥30, <40 | 252 (14.0) | 58 (11.7) | 194 (14.8) |
| ≥40, <50 | 364 (20.2) | 89 (18.0) | 275 (21.0) |
| ≥50, <60 | 276 (15.3) | 54 (10.9) | 222 (17.0) |
| ≥60, <70 | 236 (13.1) | 43 (8.7) | 193 (14.7) |
| ≥70, <80 | 105 (5.8) | 17 (3.4) | 88 (6.7) |
| ≥80 | 34 (1.9) | 8 (1.6) | 26 (2.0) |
| Sex | |||
| Male | 650 (36.2) | 207 (42.2) | 443 (33.9) |
| Female | 1146 (63.8) | 284 (57.8) | 862 (66.1) |
| Other/unknown | 8 | 4 | 4 |
| Race | |||
| Black | 1190 (67.5) | 324 (69.2) | 866 (66.9) |
| White | 265 (15.0) | 63 (13.5) | 202 (15.6) |
| Asian | 195 (11.1) | 43 (9.2) | 152 (11.7) |
| Other | 112 (6.5) | 38 (8.1) | 74 (5.8) |
| Unknown | 42 | 27 | 15 |
| Year of serum collection | |||
| 2020 | 306 (17.0) | 306 (61.8) | 0 (0.0) |
| 2021 | 474 (26.3) | 24 (4.8) | 450 (34.4) |
| 2022 | 603 (33.4) | 96 (19.4) | 507 (38.7) |
| 2023 | 421 (23.3) | 69 (13.9) | 352 (26.9) |
| Doses of SARS-CoV-2 vaccination | |||
| 0 | 495 (27.4) | 495 (100) | 0 (0.0) |
| 1 | 55 (3.0) | 0 (0.0) | 55 (4.2) |
| 2 | 764 (42.4) | 0 (0.0) | 764 (58.4) |
| 3 | 376 (20.8) | 0 (0.0) | 376 (28.7) |
| 4 | 114 (6.3) | 0 (0.0) | 114 (8.7) |
Anti-seasonal HCoV Spike IgG Titers Increase in Early Childhood
Although antibody levels varied among individuals and there were no defined cutoff thresholds for reactivity against seasonal HCoVs, nearly all participants had detectable anti-spike IgG against all 4 seasonal HCoVs (geometric means [AU/mL], 15 417, 3684, 13 762, and 45 039 for HCoV-229E, -NL63, -HKU1, and -OC43, respectively; Supplementary Figure 1). Anti-seasonal HCoV spike IgG titers were lower in early childhood and increased with age, with the exception of HCoV-NL63 (Figure 1). Statistical analysis demonstrated significant associations between younger age and lower IgG titers for HCoV-229E, -HKU1, and -OC43. The geometric mean titers (AU/mL) among participants aged ≤5, 6 to 19, and ≥20 years were 2176, 7626, and 18 355 for HCoV-229E; 5137, 10 678, and 14 760 for HCoV-HKU1; and 33 211, 46 453, and 45 107 for HCoV-OC43 (Supplementary Figure 2). There was no difference in antibody titers between male and female participants (Supplementary Figure 3). Furthermore, the titers did not statistically differ among Black, White, and Asian participants, except for anti-HCoV-HKU1 IgG, which was slightly higher in Black as compared with White participants (geometric means [AU/mL], 14 461 vs 12 001; P = .001; Supplementary Figure 4). Next, to investigate whether anti-spike IgG against seasonal HCoVs can cross-react to SARS-CoV-2 spike protein, serum samples collected early in the pandemic (until December 2020) were analyzed from participants who were SARS-CoV-2 naive (ie, unvaccinated and without serologic evidence of SARS-CoV-2 infection). Among 282 participants who were SARS-CoV-2 naive, only 2 had positive anti-SARS-CoV-2 spike IgG, indicating that seasonal HCoV spike-specific IgG generally does not cross-react to SARS-CoV-2 spike (Supplementary Figure 5).
Figure 1.
Anti-seasonal HCoV spike IgG titers by age. A total of 1804 serum samples were collected from participants (age, 2–95 years; median, 43 years). Anti-spike IgG titers against HCoV-229E, -NL63, -HKU1, and -OC43 were quantified and plotted with age. Red dots and black lines respectively represent geometric mean and standard deviation. AU, arbitrary units; HCoV, human coronavirus.
Correlations Between Anti-SARS-CoV-2 and Anti-seasonal HCoV Antibodies on SARS-CoV-2 Infection
To assess correlations between anti-spike IgG titers against SARS-CoV-2 and seasonal HCoVs in the context of SARS-CoV-2 infection, 495 samples were analyzed from participants who were SARS-CoV-2 unvaccinated: 349 SARS-CoV-2 noninfected and 146 infected. Notably, anti-HCoV-OC43 spike IgG titers were significantly higher in participants with previous SARS-CoV-2 infection as compared with participants who were noninfected (geometric mean [AU/mL], 48 442 vs 29 797; P = .00005; Supplementary Figure 6). In keeping with the previous reports [2, 11–15, 21], this result indicated that seasonal HCoV-OC43–specific antibodies are boosted following SARS-CoV-2 infection.
Correlations Between Anti-SARS-CoV-2 and Anti-seasonal HCoV Antibodies on SARS-CoV-2 Vaccination
Next, anti-spike IgG titers against SARS-CoV-2 and seasonal HCoVs were analyzed among participants who were SARS-CoV-2 noninfected to assess correlations in the context of SARS-CoV-2 vaccination. Among 1186 participants without serologic evidence of previous SARS-CoV-2 infection, 31, 522, 222, and 62 respectively received 1, 2, 3, and 4 doses of SARS-CoV-2 vaccines, whereas 349 were unvaccinated. Importantly, positive correlations were observed between anti-spike IgG titers against SARS-CoV-2 and those against HCoV-OC43, -HKU1, and -NL63 among participants who had received any dose of SARS-CoV-2 vaccines (r = 0.40, 0.26, and 0.12; P < .0001, P < .0001, and P = .0002; Supplementary Figure 7). Consistent findings were observed when the analysis was stratified by vaccine dose: positive correlations between anti-spike IgG titers against SARS-CoV-2 and HCoV-OC43 and -HKU1 were seen among participants who received ≥2 vaccine doses (r = 0.36 and 0.25, r = 0.38 and 0.27, and r = 0.53 and 0.42 for those received 2, 3, and 4 doses; Supplementary Figure 8). In summary, these data demonstrate positive correlations between anti-spike IgG titers against SARS-CoV-2 and the seasonal betacoronaviruses HCoV-OC43 and -HKU1 following SARS-CoV-2 vaccination.
Anti-SARS-CoV-2 Antibodies, Not Anti-seasonal HCoV Antibodies, Increase Upon Each Dose of SARS-CoV-2 Vaccines
If antibodies newly generated by SARS-CoV-2 vaccines cross-reacted with seasonal HCoVs, anti-seasonal HCoV spike IgG titers would be expected to increase with each SARS-CoV-2 vaccine dose. To assess this, anti-spike IgG titers against SARS-CoV-2 and seasonal HCoVs were stratified by SARS-CoV-2 vaccine dose among vaccinated participants. As expected, among 349, 31, 522, 222, and 62 participants without serologic evidence of previous SARS-CoV-2 infection, who respectively received 0, 1, 2, 3, and 4 doses of SARS-CoV-2 vaccines, anti-SARS-CoV-2 spike IgG titers showed dose-dependent increases (geometric means [AU/mL], 167, 33 595, 73 422, 192 325, and 273 827; Figure 2). In contrast, no dose-dependent increase was observed for anti-seasonal HCoV spike IgG titers. These findings indicated that the de novo antibodies generated by SARS-CoV-2 vaccines did not cross-react with seasonal HCoVs.
Figure 2.
Anti-SARS-CoV-2 spike IgG titers, not anti-seasonal HCoV spike IgG titers, increase upon each dose of SARS-CoV-2 vaccines. Anti-spike IgG titers against SARS-CoV-2 and HCoV-229E, -NL63, -HKU1, and -OC43 among participants without serologic evidence of previous SARS-CoV-2 infection are shown by the doses of previous SARS-CoV-2 vaccinations. In total, 349, 31, 522, 222, and 62 participants received 0, 1, 2, 3, and 4 doses of SARS-CoV-2 vaccines, respectively. Box-and-whisker plots represent the 2.5th and 97.5th percentiles (error bars), quartiles 1 and 3 (box), median (line), and outliers (circles). Statistical significance was determined by Kruskal-Wallis test with Dunn's multiple comparisons. ****P < .0001. AU, arbitrary units; HCoV, human coronavirus; ns, not significant.
Paired Analysis Demonstrates an Association Between Preexisting HCoV-HKU1 and -OC43 Immunity and SARS-CoV-2 Vaccine Immunogenicity
Although the previous results suggested that baseline immunity against seasonal HCoVs was associated with SARS-CoV-2 vaccine immunogenicity, we could not formally assess this hypothesis as the majority of participant samples were collected at a single time point. To overcome this limitation, a paired analysis was performed in a subset of the participants (n = 55) without serologic evidence of previous SARS-CoV-2 infection whose samples were collected pre– and post–SARS-CoV-2 vaccination. The median age of this cohort was 49 years (range, 4–82), and the participants respectively received 1 (n = 5), 2, (n = 39), 3 (n = 10), or 4 (n = 1) doses of SARS-CoV-2 vaccines. As expected, anti-SARS-CoV-2 spike IgG titers significantly increased following SARS-CoV-2 vaccination (geometric means [AU/mL], 98 vs 9912; P < .0001; Figure 3). In contrast, there were no differences in anti-spike IgG titers against HCoV-229E, -NL63, -HKU1, and -OC43 following SARS-CoV-2 vaccination (geometric means [AU/mL], 18 714 vs 15 911, 3709 vs 3392, 11 271 vs 13 802, and 27 326 vs 42 618; P = .45, P > .99, P > .99, and P = .17).
Figure 3.
Paired analysis of anti-spike IgG titers against seasonal HCoVs and SARS-CoV-2 pre– and post–SARS-CoV-2 vaccinations. Paired analysis is shown for anti-spike IgG titers against HCoV-229E, -NL63, -HKU1, -OC43, and SARS-CoV-2. Serum samples were collected pre– and post–SARS-CoV-2 vaccines from 55 participants without serologic evidence of previous SARS-CoV-2 infection. Each dot represents a study participant. Statistical significance was determined by Friedman test corrected with Dunn's multiple comparisons. ****P < .0001. AU, arbitrary units; HCoV, human coronavirus; ns, not significant.
Finally, to assess if preexisting humoral immunity against seasonal HCoVs influences SARS-CoV-2 vaccine immunogenicity, baseline (ie, prevaccination) anti-seasonal HCoV titers and postvaccination anti-SARS-CoV-2 titers were analyzed. There were no differences in postvaccination anti-SARS-CoV-2 spike IgG titers when the median baseline anti-seasonal HCoV spike IgG was used as a cutoff (geometric means [AU/mL], 77 997 vs 133 189, 88 430 vs 118 378, 108 242 vs 92 180, and 86 891 vs 111 740; P = .22, P = .74, P > .99, and P > .99, respectively, for participants with low vs high baseline IgG titers against HCoV-229E, -NL63, -HKU1, and -OC43). Notably, however, postvaccination anti-SARS-CoV-2 spike IgG titers were significantly higher in participants with high baseline humoral immunity against HCoV-OC43 and -HKU1 but not for HCoV-229E and -NL63 when lower cutoffs were applied (ie, 15 percentiles of baseline anti-seasonal HCoV IgG titers; geometric means [AU/mL], 61 354 vs 108 875, 117 141 vs 95 935, 54 610 vs 111 384, and 50 099 vs 113 279; P = .06, .68, .03, and .015 for HCoV-229E, -NL63, -HKU1, and -OC43; Figure 4). Between participants with low and high baseline seasonal HCoV IgG titers, there were no differences in baseline anti-SARS-CoV-2 spike IgG titers and demographics including age, underlying diseases, numbers of SARS-CoV-2 vaccines, and interval between vaccination and sample collection. Furthermore, univariate and multivariable linear regression analyses were performed, adjusting for age, number of vaccine dose, and interval since the first vaccine dose. Baseline HCoV-HKU-1 and -OC43 IgG titers remained significantly associated with postvaccination anti-SARS-CoV-2 spike IgG levels after adjustment (β = 110 592 and 108 855; 95% CI, 17 922–203 262 and 12 013–205 697; P = .020 and .028 for HCoV-HKU-1 and -OC43; Supplementary Table 1). In summary, these results indicated that participants with higher baseline humoral immunity against seasonal betacoronaviruses HCoV-HKU1 and -OC43 generated higher SARS-CoV-2 spike-specific antibodies as compared with those with low baseline immunity.
Figure 4.
High baseline anti-spike IgG titers against HCoV-HKU1 and -OC43 are associated with higher SARS-CoV-2 vaccine immunogenicity. Anti-SARS-CoV-2 spike IgG titers before (“Baseline”) and after (“Post”) SARS-CoV-2 vaccines are shown, as well as their differences (“Delta”) among participants with low and high baseline anti-seasonal HCoV spike IgG titers. Serum samples were collected pre– and post–SARS-CoV-2 vaccination from 55 participants without serologic evidence of previous SARS-CoV-2 infection. Cutoffs for baseline seasonal HCoV immunity were defined as the 15th percentile of anti-spike IgG for each seasonal HCoV. Each dot represents a study participant. Bars represent the geometric mean. Statistical significance was determined by the Kruskal-Wallis test. *P < .05. AU, arbitrary units; HCoV, human coronavirus; ns, not significant.
DISCUSSION
In this study, we aimed to investigate the effect of preexisting humoral immunity against seasonal HCoVs on SARS-CoV-2 vaccine responses. By analyzing 1804 participants including young children, we observed that anti-seasonal HCoV spike IgG titers increased in early childhood, with most adult participants exhibiting reactive antibodies. We demonstrated positive correlations of anti-spike IgG titers between SARS-CoV-2 and HCoV-OC43 and -HKU1 in the context of SARS-CoV-2 vaccination. Furthermore, anti-SARS-CoV-2 spike IgG titers, not anti-seasonal HCoV spike IgG titers, showed a dose-dependent increase on SARS-CoV-2 vaccinations, indicating that antibodies generated by SARS-CoV-2 vaccines did not cross-react with seasonal HCoVs.
In addition, we performed a paired analysis in a subset of 55 participants with pre– and post–SARS-CoV-2 vaccination serum samples. As expected, anti-spike IgG titers against SARS-CoV-2 significantly increased following SARS-CoV-2 vaccinations, while titers against seasonal HCoVs remained unchanged. Most important, participants with high baseline anti-HCoV-HKU1 and -OC43 IgG titers mounted significantly higher anti-SARS-CoV-2 spike IgG titers following SARS-CoV-2 vaccines as compared with those with low baseline titers, likely reflecting an immunologic priming effect of prior HCoV exposure. Together, these findings indicated that individuals with high preexisting humoral immunity against seasonal betacoronaviruses HCoV-HKU1 and -OC43 may experience enhanced SARS-CoV-2 vaccine immunogenicity.
Closely related viruses with a high degree of homology can induce cross-reactive immune responses. Such preexisting cross-reactive immunity may modulate immune responses upon subsequent infection or vaccination of a closely related virus, a mechanism known as immune imprinting, which has been most extensively studied in influenza virus [22–24]. SARS-CoV-2 and seasonal HCoVs, especially the betacoronaviruses HCoV-OC43 and -HKU-1, share high degree of homology, including the spike protein, which has been the main target of SARS-CoV-2 vaccines [1, 9, 18]. Cross-reactive immune responses between HCoVs during SARS-CoV-2 infection have been reported [10–15], and our study also demonstrated positive correlations of anti-spike IgG titers between SARS-CoV-2 and seasonal HCoVs in the context of SARS-CoV-2 infection.
The aforementioned notwithstanding, the impact of preexisting humoral immunity to seasonal HCoVs on SARS-CoV-2 vaccine responses has remained uncertain. While some studies have reported associations between higher preexisting antibodies against seasonal HCoVs and enhanced SARS-CoV-2 vaccine immunogenicity [18, 19], other studies found no such associations [2, 4]. To address the major limitations of earlier studies, including small-scaled studies limited to adult participants with high anti-seasonal HCoV antibodies at baseline, we herein conducted a large-scale study including young children and adults, thereby capturing a broad spectrum of baseline immunity against seasonal HCoVs. Most important, we identified a positive association between preexisting humoral immunity against seasonal HCoV-OC43 and -HKU-1 and SARS-CoV-2 vaccine immunogenicity. These findings align with previous studies showing that preexisting cross-reactive CD4+ T cells derived from seasonal HCoVs enhance SARS-CoV-2–specific CD4+ T-cell responses after SARS-CoV-2 vaccination [25, 26]. Furthermore, our results might contribute to the information needed to facilitate development of next-generation coronavirus vaccines, including pan-coronavirus vaccines, by identifying epitopes that are conserved among diverse coronaviruses.
In addition to the aforementioned, our study is associated with several limitations. First, we assessed only the effect of humoral immunity, and cell-mediated immunity against seasonal HCoVs on SARS-CoV-2 vaccine immunogenicity was not investigated. Additionally, we did not evaluate antibody functionality, such as neutralization. Second, although we found that participants with higher baseline anti-seasonal HCoV spike IgG titers mounted stronger antibody responses to SARS-CoV-2, there are no clinically validated cutoffs to stratify preexisting seasonal HCoV immunity for categorizing participants as having high or low baseline immunity. Future research is needed to establish the standardized thresholds. Third, cross-reactivity between anti-seasonal HCoV and SARS-CoV-2 antibodies was assessed with serum samples collected during the early pandemic rather than with prepandemic samples. Although we restricted this analysis to participants who were SARS-CoV-2 naive (ie, unvaccinated individuals without serologic evidence of SARS-CoV-2 infection), unrecognized exposure cannot be completely excluded. However, the rate of anti-SARS-CoV-2 spike IgG positivity in our cohort (0.7%, 2/282) was comparable to that observed in prepandemic samples analyzed with the same assay (0.5%, 2/407) [3], supporting the interpretation that the detected reactivity represents true background signal rather than previous infection. Fourth, antibody responses to noncoronavirus antigens were not assessed, precluding direct evaluation of a generalized humoral responder phenotype. Therefore, we cannot exclude the possibility that individuals with low seasonal HCoV antibody titers may have a reduced overall capacity to mount antibody responses. Yet, the association was specific to betacoronaviruses (HCoV-OC43 and -HKU1) and not consistently seen for alphacoronaviruses, arguing against a uniform hyporesponsive state. Last, although our study differs from previous reports by including young children, only a small number of children received SARS-CoV-2 vaccines. Overall, a longitudinal study including young children measuring humoral and cell-mediated immunity pre– and post–SARS-CoV-2 vaccination is warranted to precisely assess the effect of preexisting immunity against seasonal HCoVs on SARS-CoV-2 vaccine responses.
In conclusion, our study indicated that preexisting humoral immunity against seasonal betacoronaviruses HCoV-OC43 and -HKU-1 enhances anti-SARS-CoV-2 spike antibody responses following SARS-CoV-2 vaccination. The results highlight cross-reactive immune recognition within the betacoronaviruses and provide insights in the development of next-generation coronavirus vaccines by identifying epitopes that are conserved among coronaviruses. It is unclear whether a high prevalence of seasonal HCoVs within a community affects COVID-19 vaccine effectiveness in a manner that might influence vaccination strategies; this would be an area for future research.
Supplementary Material
Notes
Acknowledgments. We appreciate the contributions by the participants. The seroMARK team is supported by a Community Advisory Group, as follows: Dr Pamela Appelt (chair), Oakville, Ontario; Dr Mark Awuku, Windsor, Ontario; Mr Paul Bailey, Toronto, Ontario; Dr Janet Collins, London, Ontario; Mr Liben Gebremikael, Toronto, Ontario; Ms Jenny Gumb, Toronto, Ontario; Ms Tesfai Mengesha, Toronto, Ontario; Ms Adaoma Patterson, Toronto, Ontario; Dr Cheryl Prescod, Toronto, Ontario; Ms Noelle Richardson, Toronto, Ontario; Dr Sylvanus Thompson, Toronto, Ontario; Ms Nicole Welch, Toronto, Ontario.
Data availability statements. The data underlying this article will be shared on reasonable request to the corresponding author.
Patient consent statement. This study was approved by Clinical Trials Ontario (CTO3274 and 3654), The Hospital for Sick Children (3274-CIA-Aug/2020-42457 and 3654-CIA-Jun/2021-55478), and the London Health Sciences Centre (3274-CIA-Nov/2020-45486 and 3654-CIA-Oct/2021-59895).
Financial support. This work was supported by The Hospital for Sick Children Foundation; the University of Toronto COVID-19 Action Initiative and the Office of Equity, Diversity and Inclusion, Temerty Faculty of Medicine, University of Toronto; the COVID-19 Immunity Task Force, Canada and the Canadian Institutes of Health Research.
Contributor Information
Etsuro Nanishi, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Matthew Hwang, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Ana Citlali Márquez, Public Health Laboratory, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada; Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
Walter Byrne, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Maria-Rosa La Neve, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Alice Litosh, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Jasmik S Saini, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Kimberly Thompson, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Nicole Wisener, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Makiko Nanishi, Division of Respiratory Medicine, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada.
Julia E M Upton, Division of Immunology and Allergy, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Aaron Campigotto, Division of Microbiology, Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Michelle Barton, Division of Infectious Diseases, Department of Paediatrics, Children's Hospital, London Health Sciences Centre, University of Western Ontario, London, Ontario, Canada.
Agatha N Jassem, Public Health Laboratory, British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada.
Upton D Allen, Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Supplementary Data
Supplementary materials are available at Open Forum Infectious Diseases online. Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.
References
- 1. Cui J, Li F, Shi ZL. Origin and evolution of pathogenic coronaviruses. Nat Rev Microbiol 2019; 17:181–92. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Lin CY, Wolf J, Brice DC, et al. Pre-existing humoral immunity to human common cold coronaviruses negatively impacts the protective SARS-CoV-2 antibody response. Cell Host Microbe 2022; 30:83–96.e4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Tanunliong G, Liu AC, Kaweski S, et al. Age-associated seroprevalence of coronavirus antibodies: population-based serosurveys in 2013 and 2020, British Columbia, Canada. Front Immunol 2022; 13:836449. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Yin D, Han Z, Lang B, et al. Effect of seasonal coronavirus immune imprinting on the immunogenicity of inactivated COVID-19 vaccination. Front Immunol 2023; 14:1195533. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Sridhar S, Begom S, Bermingham A, et al. Cellular immune correlates of protection against symptomatic pandemic influenza. Nat Med 2013; 19:1305–12. [DOI] [PubMed] [Google Scholar]
- 6. Turtle L, Bali T, Buxton G, et al. Human T cell responses to Japanese encephalitis virus in health and disease. J Exp Med 2016; 213:1331–52. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7. Mongkolsapaya J, Dejnirattisai W, Xu XN, et al. Original antigenic sin and apoptosis in the pathogenesis of dengue hemorrhagic fever. Nat Med 2003; 9:921–7. [DOI] [PubMed] [Google Scholar]
- 8. Dejnirattisai W, Jumnainsong A, Onsirisakul N, et al. Cross-reacting antibodies enhance dengue virus infection in humans. Science 2010; 328:745–8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9. Murray SM, Ansari AM, Frater J, et al. The impact of pre-existing cross-reactive immunity on SARS-CoV-2 infection and vaccine responses. Nat Rev Immunol 2023; 23:304–16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10. Anderson EM, Goodwin EC, Verma A, et al. Seasonal human coronavirus antibodies are boosted upon SARS-CoV-2 infection but not associated with protection. Cell 2021; 184:1858–64.e10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11. Guo L, Wang Y, Kang L, et al. Cross-reactive antibody against human coronavirus OC43 spike protein correlates with disease severity in COVID-19 patients: a retrospective study. Emerg Microbes Infect 2021; 10:664–76. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Prévost J, Gasser R, Beaudoin-Bussières G, et al. Cross-sectional evaluation of humoral responses against SARS-CoV-2 spike. Cell Rep Med 2020; 1:100126. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13. Aydillo T, Rombauts A, Stadlbauer D, et al. Immunological imprinting of the antibody response in COVID-19 patients. Nat Commun 2021; 12:3781. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. Cohen KW, Linderman SL, Moodie Z, et al. Longitudinal analysis shows durable and broad immune memory after SARS-CoV-2 infection with persisting antibody responses and memory B and T cells. Cell Rep Med 2021; 2:100354. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15. Aguilar-Bretones M, Westerhuis BM, Raadsen MP, et al. Seasonal coronavirus-specific B cells with limited SARS-CoV-2 cross-reactivity dominate the IgG response in severe COVID-19. J Clin Invest 2021; 131:e150613. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16. McNaughton AL, Paton RS, Edmans M, et al. Fatal COVID-19 outcomes are associated with an antibody response targeting epitopes shared with endemic coronaviruses. JCI insight 2022; 7:e156372. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17. Wratil PR, Schmacke NA, Karakoc B, et al. Evidence for increased SARS-CoV-2 susceptibility and COVID-19 severity related to pre-existing immunity to seasonal coronaviruses. Cell Rep 2021; 37:110169. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18. Hu C, Wang Z, Ren L, et al. Pre-existing anti-HCoV-OC43 immunity influences the durability and cross-reactivity of humoral response to SARS-CoV-2 vaccination. Front Cell Infect Microbiol 2022; 12:978440. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Asamoah-Boaheng M, Grunau B, Karim ME, et al. Are higher antibody levels against seasonal human coronaviruses associated with a more robust humoral immune response after SARS-CoV-2 vaccination? Front Immunol 2022; 13:954093. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Allen UD, Barton M, Upton J, et al. Disproportionate rates of COVID-19 among Black Canadian communities: lessons from a cross-sectional study in the first year of the pandemic. J Racial Ethn Health Disparities 2024; 12:649–58. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Dugas M, Grote-Westrick T, Vollenberg R, et al. Less severe course of COVID-19 is associated with elevated levels of antibodies against seasonal human coronaviruses OC43 and HKU1 (HCoV OC43, HCoV HKU1). Int J Infect Dis 2021; 105:304–6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22. Huang CQ, Vishwanath S, Carnell GW, Chan ACY, Heeney JL. Immune imprinting and next-generation coronavirus vaccines. Nat Microbiol 2023; 8:1971–85. [DOI] [PubMed] [Google Scholar]
- 23. Cobey S. Vaccination against rapidly evolving pathogens and the entanglements of memory. Nat Immunol 2024; 25:2015–23. [DOI] [PubMed] [Google Scholar]
- 24. Zhou Z, Barrett J, He X. Immune imprinting and implications for COVID-19. Vaccines (Basel) 2023; 11:875. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25. Loyal L, Braun J, Henze L, et al. Cross-reactive CD4(+) T cells enhance SARS-CoV-2 immune responses upon infection and vaccination. Science 2021; 374:eabh1823. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26. Mateus J, Dan JM, Zhang Z, et al. Low-dose mRNA-1273 COVID-19 vaccine generates durable memory enhanced by cross-reactive T cells. Science 2021; 374:eabj9853. [DOI] [PMC free article] [PubMed] [Google Scholar]
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