Effect of naturally acquired type-specific serum antibodies against human papillomavirus type 16 infection

Naturally developed HPV16 antibodies and risk of newly detected cervical HPV infection outcomes

Little is known about the protection conferred by antibodies from natural human papillomavirus (HPV) infection. Our objective was to evaluate the association between HPV16 seroreactivity and HPV16 redetection, newly detected HPV infections, and loss of HPV DNA detection during follow-up. We analyzed data from 2462 unvaccinated Brazilian women. HPV16 IgG and neutralizing antibodies at baseline were assessed by enzyme-linked immunosorbent assay (n = 1975) and by the pseudovirus-based papillomavirus neutralization assay (n = 487). HPV detection, genotyping, and viral load were assessed by PCR-based methods. The associations were analyzed by Cox proportional hazards models. We observed a positive association between HPV16 IgG seroreactivity and redetection of HPV16 infections. Age-adjusted hazard ratios (HR) with 95% confidence intervals (CI) ranged from 2.45 (1.04-5.74) to 5.10 (1.37-19.00). Positive associations were also observed between HPV16 IgG antibodies and (1) newly detected HPV infections by genotypes unrelated to HPV16 (age-adjusted HR [95% CI] = 1.32 [1.08-1.2]) and (2) loss of detection of HPV infections by genotypes unrelated to HPV16 (age-adjusted HR [95% CI] = 1.24 [1.03-1.50]). Naturally developed HPV16 antibodies do not prevent recurrent HPV infections. Overall HPV16 IgG and neutralizing antibodies seem to be serological markers for latent or past infections.

Association of naturally acquired type-specific HPV antibodies and subsequent HPV re-detection: systematic review and meta-analysis

BACKGROUND

Understanding the role of naturally acquired (i.e., infection-induced) human papillomavirus (HPV) antibodies against reinfection is important given the high incidence of this sexually transmitted infection. However, the protective effect of naturally acquired antibodies in terms of the level of protection, duration, and differential effect by sex remains incompletely understood. We conducted a systematic review and a meta-analysis to (1) strengthen the evidence on the association between HPV antibodies acquired through past infection and subsequent type-specific HPV detection, (2) investigate the potential influence of type-specific HPV antibody levels, and (3) assess differential effects by HIV status.

METHODS

We searched Embase and Medline databases to identify studies which prospectively assessed the risk of type-specific HPV detection by baseline homologous HPV serostatus among unvaccinated individuals. Random-effect models were used to pool the measures of association of naturally acquired HPV antibodies against subsequent incident detection and persistent HPV positivity. Sources of heterogeneity for each type were assessed through subgroup analyses stratified by sex, anatomical site of infection, male sexual orientation, age group, and length of follow-up period. Evidence of a dose-response relationship of the association between levels of baseline HPV antibodies and type-specific HPV detection was assessed. Finally, we pooled estimates from publications reporting associations between HPV serostatus and type-specific HPV detection by baseline HIV status.

RESULTS

We identified 26 publications (16 independent studies, with 62,363 participants) reporting associations between baseline HPV serostatus and incident HPV detection, mainly for HPV-16 and HPV-18, the most detected HPV type. We found evidence of protective effects of baseline HPV seropositivity and subsequent detection of HPV DNA (0.70, 95% CI 0.61-0.80, NE = 11) and persistent HPV positivity (0.65, 95% CI 0.42-1.01, NE = 5) mainly for HPV-16 among females, but not among males, nor for HPV-18. Estimates from 8 studies suggested a negative dose-response relationship between HPV antibody level and subsequent detection among females. Finally, we did not observe any differential effect by baseline HIV status due to the limited number of studies available.

CONCLUSION

We did not find evidence that naturally acquired HPV antibodies protect against subsequent HPV positivity in males and provide only modest protection among females for HPV-16. One potential limitation to the interpretation of these findings is potential misclassification biases due to different causes.

Correlation between cervical HPV DNA detection and HPV16 seroreactivity measured with L1-only and L1+L2 viral capsid antigens

Introduction. Persistent human papillomavirus (HPV) type 16 infection is the main causal agent of cervical cancer. Most HPV infections clear spontaneously within 1-2 years. Although not all infected women develop detectable HPV antibodies, about 60-70 % seroconvert and retain their antibodies at low levels.Aim. We investigated if cervical HPV16 DNA positivity was associated with HPV16 seroreactivity measured with two different antigen formulations. We assessed if associations were influenced by co-infection with other HPV types and HPV16 viral load.Methodology. We used baseline data for women participating in the Ludwig-McGill cohort, a longitudinal investigation of the natural history of HPV infection and cervical neoplasia. The study enrolled 2462 Brazilian women from 1993 to 1997 (pre-vaccination). ELISA assays were based on L1-only or L1+L2 virus-like particles (VLPs). Seroreactivity was expressed as normalized absorbance ratios. HPV genotyping and viral load were evaluated by PCR protocols. Pearson's r was used to measure correlations between interval-scaled variables. Serological accuracy in HPV16 DNA detection was assessed using receiver operating characteristic (ROC) curves. We analysed the association between HPV DNA positivity and HPV16 seroreactivity by linear regression.Results. Correlations between L1+L2 and L1-only VLPs for detection of HPV16 were poor (r=0.43 and 0.44 for dilutions 1 : 10 and 1 : 50, respectively). The protocol with the best accuracy was L1+L2 VLPs at serum dilution 1 : 10 (ROC area=0.73, 95 % CI: 0.65-0.85). HPV16 DNA positivity was correlated with HPV16 seroreactivity and was not influenced by co-infection or viral load. To a lesser degree, HPV16 seroreactivity was correlated with infection by other Alpha-9 papillomavirus species.Conclusion. HPV16 DNA positivity and HPV16 seroreactivity are strongly correlated. L1+L2 VLPs perform better than L1-only VLPs for detecting IgG antibodies to HPV16 in women infected with HPV16 or other Alpha-9 HPV species. This study advances our understanding of humoral immune responses against HPV16 by providing insights about the influence of VLP antigen composition to measure humoral immune response against naturally acquired HPV infection.