Comparison of different assays to assess human papillomavirus (HPV) type 16- and 18-specific antibodies after HPV infection and vaccination

HPV-specific antibodies in female genital tract secretions captured via first-void urine retain their neutralizing capacity

Human papillomavirus (HPV) vaccines, primarily relying on neutralizing antibodies, have proven highly effective. Recently, HPV-specific antibodies have been detected in the female genital tract secretions captured by first-void urine (FVU), offering a minimally invasive diagnostic approach. In this study, we investigated whether HPV16-specific antibodies present in FVU samples retain their neutralizing capacity by using pseudovirion-based neutralization assays. Paired FVU and serum samples (vaccinated n = 25, unvaccinated n = 25, aged 18-25) were analyzed using two orthogonal pseudovirion-based neutralization assays, one using fluorescence microscopy and the other using luminescence-based spectrophotometry. Results were compared with HPV16-specific IgG concentrations and correlations between neutralizing antibodies in FVU and serum were explored. The study demonstrated the presence of neutralizing antibodies in FVU using both pseudovirion-based neutralization assays, with the luminescence-based assay showing higher sensitivity for FVU samples, while the fluorescence microscopy-based assay exhibited better specificity for serum and overall higher reproducibility. High Spearman correlation values were calculated between HPV16-IgG and HPV16-neutralizing antibodies for both protocols (rs: 0.54-0.94, p < .001). Significant Spearman correlations between FVU and serum concentrations were also established for all assays (rs: 0.44-0.91, p < .01). This study demonstrates the continued neutralizing ability of antibodies captured with FVU, supporting the hypothesis that HPV vaccination may reduce autoinoculation and transmission risk to the sexual partner. Although further protocol optimizations are warranted, these findings provide a foundation for future research and larger cohort studies that could have implications for the optimal design, evaluation, and implementation of HPV vaccination programs.

Multiplex immunoassay to measure antibody response to nine HPV vaccine types

Well-characterized HPV serology assays are required to evaluate performance of biosimilar candidate vaccines, reduced dosing schedules and novel administration methods. We report characterization of an expanded assay, M9ELISA, that detects antibodies to HPV virus-like particles (VLP) of nine types using direct IgG ELISA on the Meso Scale Discovery (MSD) electrochemiluminescence platform. The method is based on the previously published M4ELISA which detects antibodies to HPV6,11,16, and 18. It has been modified to add detection of antibodies to HPV31,33,45,52 and 58, and to streamline assay and reduce background. The M9ELISA plates were prepared with purified type specific L1 + L2 VLPs coated on 10-spot/well standard MSD microplates. Results of ELISA on three serial dilutions of serum were read on MSD imager, and titers calculated using the parallel line method. Evaluations included dynamic range, assay reproducibility, and stability over time. We compared M9ELISA results to those from a pseudovirion-based neutralization assay in sera from a mixed cohort of unvaccinated and vaccinated individuals (n = ~116) and to competitive Luminex immunoassay (cLIA) results in sera from a predominantly unvaccinated cohort (n = 4426). The linear range of the assay extended over 5 logs, with inter-assay reproducibility coefficient of variation ≤25% for all types. The pre-coated plates were stable for at least 2 years. Spearman correlation of antibody titers showed excellent correlation with PBNA (r = 0.86-0.97) and moderate correlation (r = 0.52-0.68) with cLIA. Thus, the M9ELISA can serve as a useful platform for high-throughput, sensitive and simultaneous quantitation of the antibody responses to nine HPV vaccine types.

Immune surveillance for vaccine-preventable diseases

INTRODUCTION

Immunesurveillance is an important tool to monitor the protection of the population against vaccine-preventable diseases, which is currently mostly based on the detection of specific serum antibodies. However, the landscape of immune surveillance is changing, driven by emerging and evolving pathogens, changes in the age distribution of the population and scientific understanding of protective immunity, necessitating a comprehensive review.

AREAS COVERED

To anticipate these changes, reliable and high-throughput detection of antibody levels is desired to enable screening in larger population settings. Antibody levels alone do not always equate with protection and may require additional functional testing of the antibodies or immune cell-based assays. In addition, the location (systemic or locally mucosal) of the infection and whether the antibodies are induced through infection or vaccination have implications for both immune protection and assessing immune status.

EXPERT COMMENTARY

In order to perform multicenter studies on many samples for multiple antigens, more validated reference materials and wider adoption of high-throughput techniques are needed. The field of serosurveillance will also benefit from better correlates of protection and understanding of (local) mechanisms of protection. Here we give an overview of the current state-of-the-art of serosurveillance and how the field could move forward.

Persisting Antibody Response 9 Years After Bivalent Human Papillomavirus (HPV) Vaccination in a Cohort of Dutch Women: Immune Response and the Relation to Genital HPV Infections

The bivalent human papillomavirus (HPV) vaccine is highly effective and induces robust serological responses. Using a Dutch prospective cohort initiated in 2009, including 744 vaccinated and 294 unvaccinated girls (1993–1994) who provide a vaginal self-swab sample, serum sample, and questionnaire yearly, we report a high, persisting antibody response up to 9 years after vaccination for vaccine types HPV-16 or HPV-18. Antibodies against nonvaccine HPV types 31, 33, 45, 52, and 58 were lower but still significantly higher than in unvaccinated individuals. This was also reflected in the seroprevalence. We compared participant characteristics and antibody levels between vaccinated women with and those without HPV infections 1 year before infection (204 incident and 64 persistent infections), but we observed no consistent difference in type-specific antibody levels. Having a high-risk HPV infection was associated with sexual risk behavior and smoking 1 year before infection. Although high antibody levels are necessary for protection, our study suggests that on the individual level other factors such as HPV exposure or antibody avidity could be important.

Investigating the aetiology of adverse events following HPV vaccination with systems vaccinology

In contrast to the insidious and poorly immunogenic human papillomavirus (HPV) infections, vaccination with the HPV virus-like particles (vlps) is non-infectious and stimulates a strong neutralizing-antibody response that protects HPV-naïve vaccinees from viral infection and associated cancers. However, controversy about alleged adverse events following immunization (AEFI) with the vlps have led to extensive reductions in vaccine acceptance, with countries like Japan dropping it altogether. The AEFIs are grouped into chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). In this review, we present a hypothesis that the AEFIs might arise from malfunctions within the immune system when confronted with the unusual antigen. In addition, we outline how the pathophysiology of the AEFIs can be cost-effectively investigated with the holistic principles of systems vaccinology in a two-step process. First, comprehensive immunological profiles of HPV vaccinees exhibiting the AEFIs are generated by integrating the data derived from serological profiling for prominent HPV antibodies and serum cytokines, with data from serum metabolomics, peripheral white blood cells transcriptomics and gut microbiome profiling. Next, the immunological profiles are compared with corresponding profiles generated for matched (a) HPV vaccinees without AEFIs; (b) non-HPV-vaccinated individuals with CFS/ME-like symptoms; and (c) non-HPV-vaccinated individuals without CFS/ME. In these comparisons, any causal links between HPV vaccine and the AEFIs, as well as the underlying molecular basis for the links will be revealed. Such a study should provide an objective basis for evaluating HPV vaccine safety and for identifying biomarkers for individuals at risk of developing AEFI with HPV vaccination.

Human papillomavirus first and second generation vaccines-current status and future directions

It has been more than 10 years that the first prophylactic papillomavirus vaccine became available, although distribution has been mainly limited to the more affluent countries. The first two vaccines have been a great success, hundreds of millions of women and a much smaller number of men have been vaccinated ever since. In a few countries with high vaccination coverage, in particular Australia but also parts of Great Britain and others, clinical impact of vaccination programs is already visible and there are indications for herd immunity as well. Vaccine efficacy is higher than originally estimated and the vaccines have an excellent safety profile. Gardasil9 is a second generation HPV virus-like particle vaccine that was licensed in 2015 and there are more to come in the near future. Currently, burning questions in respect to HPV vaccination are the duration of protection - especially in regard to cross-protection - reduction of the three-dose regimen and its impact on cross-protection; and duration of response, as well as protection against oropharyngeal HPV infections. Furthermore, researchers are seeking to overcome limitations of the VLP vaccines, namely low thermal stability, cost, invasive administration, limited coverage of non-vaccine HPV types, and lack of therapeutic efficacy. In this review we summarize the current status of licensed VLP vaccines and address questions related to second and third generation HPV vaccines.

HPV SEROSTATUS PRE- AND POST-VACCINATION IN A RANDOMIZED PHASE II PREPAREDNESS TRIAL AMONG YOUNG WESTERN CAPE, SOUTH AFRICAN WOMEN: THE EVRI TRIAL

Background

HPV antibodies are a marker of past exposure to the virus. Our objective was to assess HPV serostatus pre- and post-vaccination among HIV-negative women.

Methods

Women aged 16–24 years old were randomized in a placebo controlled trial utilizing the 4-valent HPV (4vHPV) vaccine (NCT01489527, clinicaltrials.gov). Participants (n=389) received the 4vHPV vaccine or placebo following a three dose schedule. Sera were collected at Day 1 and Month 7 for assessment of HPV 6, 11, 16, and 18 neutralizing antibody levels using a multiplex competitive Luminex immunoassay (Merck) based on detecting the L1 capsid antigen for each HPV type.

Results

Seroprevalence was 73% for HPV6, 47% for HPV11, 33% for HPV16, and 44% for HPV18. Seroprevalence for any HPV type did not significantly differ by age or lifetime number of partners. The majority of participants (64%) had two or more 4vHPV antibodies present at enrollment and 12% had antibodies to all four. Among women in the vaccine arm, those that were seropositive for HPV16 at enrollment had higher titers at month 7 compared to women that were seronegative for HPV16 at enrollment; this trend holds for the other HPV types as well. Seroconversion among baseline seronegative participants in the placebo group ranged from 5% for HPV16 to 23% for HPV6.

Conclusion

HPV seroprevalence was high in this population, emphasizing the need to vaccinate prior to sexual debut.

Human Papillomavirus (HPV) L1 Serum Antibodies and the Risk of Subsequent Oral HPV Acquisition in Men: The HIM Study

The role of antibody-mediated immunity in preventing newly acquired oral human papillomavirus (HPV) is not well understood. Among 1618 men participating in the HPV Infection in Men (HIM) Study, we evaluated oral rinses for HPV DNA and baseline sera for HPV-6, -11, -16, and -18 L1 antibodies. Thirty percent of men (486) were seropositive for ≥1 HPV type, and 25 men developed incident oral HPV infection (HPV-6 was detected in 7, HPV-11 in 0, HPV-16 in 17, and HPV-18 in 1). Cox models revealed that men with circulating antibodies to HPV-6, -11, -16, or -18 were not less likely to acquire type-specific oral HPV than men without antibodies (hazard ratio for the risk of acquiring HPV-6, -11, -16, or -18, 1.63; 95% confidence interval, .56-4.76).

HPV prophylactic vaccines: lessons learned from 10 years experience

When HPV vaccines were registered in 2006/2007, it was unclear whether these new and type-specific prophylactic vaccines would be accepted by the community for cancer prevention. With an optimal vaccination age of early adolescence, three vaccine doses required, HPV a sexually transmitted infection, and secondary prevention already available in the form of cervical screening, considerable potential challenges were faced. At the time of licensing, vaccine efficacy in males and duration of immunity were not yet unknown. Almost a decade later, with over 230 million doses of the vaccines distributed worldwide and national HPV vaccination programs in place in many countries, it is timely to reflect on current knowledge about the vaccines and some of the lessons learned during implementation.

EUROGIN 2014 roadmap: differences in human papillomavirus infection natural history, transmission and human papillomavirus-related cancer incidence by gender and anatomic site of infection

Human papillomaviruses (HPVs) cause cancer at multiple anatomic sites in men and women, including cervical, oropharyngeal, anal, vulvar and vaginal cancers in women and oropharyngeal, anal and penile cancers in men. In this EUROGIN 2014 roadmap, differences in HPV-related cancer and infection burden by gender and anatomic site are reviewed. The proportion of cancers attributable to HPV varies by anatomic site, with nearly 100% of cervical, 88% of anal and <50% of lower genital tract and oropharyngeal cancers attributable to HPV, depending on world region and prevalence of tobacco use. Often, mirroring cancer incidence rates, HPV prevalence and infection natural history varies by gender and anatomic site of infection. Oral HPV infection is rare and significantly differs by gender; yet, HPV-related cancer incidence at this site is several-fold higher than at either the anal canal or the penile epithelium. HPV seroprevalence is significantly higher among women compared to men, likely explaining the differences in age-specific HPV prevalence and incidence patterns observed by gender. Correspondingly, among heterosexual partners, HPV transmission appears higher from women to men. More research is needed to characterize HPV natural history at each anatomic site where HPV causes cancer in men and women, information that is critical to inform the basic science of HPV natural history and the development of future infection and cancer prevention efforts.

Comparisons of VLP-Based ELISA, Neutralization Assays with Native HPV, and Neutralization Assays with PsV in Detecting HPV Antibody Responses in HIV-Infected Women

OBJECTIVE

Human papillomavirus (HPV)-associated cancers are important public health problems in HIV-infected people. Assays based on HPV virus-like particles (VLP) and pseudoviruses (PsV) are commonly used to examine HPV antibody responses in HIV-infected people, but neutralization assays with native HPV have not been utilized and a comparison of these three assays is lacking. We evaluated the agreement of assays using VLP, native HPV and PsV in detecting HPV16 and 18 antibodies in HIV-infected women.

METHODS

The VLP-based ELISA (VLP-ELISA) was used to detect antibody responses to HPV16 and 18 and cottontail rabbit papillomavirus (CRPV) VLP antigens. Neutralization assays with native HPV (NA-HPV) and with PsV (NA-PsV) were conducted to examine HPV16 or 18 neutralizing antibodies. Intra class correlation coefficients (ICC) and kappa coefficients were used to assess the agreements of seropositivity between the assays.

RESULTS

The seroprevalence detected by the VLP-ELISA, NA-HPV and NA-PsV in 94 HIV-infected women was 35%, 51% and 27% for HPV16 and 14%, 44% and 21% for HPV18. Cross-reactivity between HPV16 and HPV18 was 0.35, 0.04 and 0.33 (kappa coefficients) for the VLP-ELISA, NA-HPV and NA-PsV. The agreements of seropositivity between the three assays were low. Six women who were HPV16 DNA positive were seropositive by the NA-HPV but only two were HPV16 seropositive by the VLP-ELISA or NA-PsV. One HPV18 DNA positive woman was seropositive by all three assays. Repeated tests indicated excellent reproducibility of the NA-HPV.

CONCLUSION

HPV serology results vary across different assays. The NA-HPV appears to be a sensitive and reliable approach in detecting natural HPV antibodies in HIV-infected women. The NA-HPV can be applied in both HPV natural history studies and vaccine studies in HIV-infected people.

Development and evaluation of multiplexed immunoassay for detection of antibodies to HPV vaccine types

Reliable antibody based-assays are needed to evaluate the immunogenicity of current vaccines, impact of altered dosing schemes or of new vaccine formulations. An ideal assay platform would allow multiplex type-specific detection with minimal sample requirement. We used the Meso Scale Discovery (MSD) electrochemiluminescence based detection platform to develop a multiplex direct virus-like particle (VLP) ELISA to detect antibodies to HPV 6, 11, 16, and 18 with a protocol developed for detection using the SI 6000 imager (M4ELISA). MSD prepared the plates in the 7-spot/well format, using the purified VLPs (4 spots) and PBS+BSA pH7.4 (3 blank spots). Three-point titrations and the parallel line method were used to calculate antibody levels. Dynamic range, precision, and stability of pre-printed plates were determined using a panel of previously characterized sera. Cut-off values using children's sera were established using 99% RLU limits based on the 4-parameter Johnson Su best fit curve. Results of the M4ELISA were compared to competitive Luminex Immunoassay (cLIA) on n = 4454 sera from a predominantly unvaccinated cohort. Using a VLP coating concentration of 80 μg/ml with BSA provided the most robust RLU signal for all types. The dynamic range of the assay was about 1000 fold, with assay variability under 25% for each of the four vaccine types. Long-term stability of the plates extended to about 7 months from the time plates was received in the laboratory after printing. There was moderate agreement (κ = 0.38-0.54) between M4ELISA and cLIA, with antibody detection for each of the 4 types more frequent with M4ELISA. Quantitative analysis however showed a good correlation between concordant samples by both assays (ρ ≥ 0.6). The MSD platform shows promise for simultaneous quantitation of the antibody responses to four HPV vaccine types in a high-throughput manner.

HPV seroconversion following anal and penile HPV infection in HIV-negative and HIV-infected MSM

BACKGROUND

We assessed human papillomavirus (HPV) seroconversion following anal and penile HPV infection in HIV-negative and HIV-infected men who have sex with men (MSM).

METHODS

MSM aged ≥18 years were recruited in Amsterdam, the Netherlands (2010-2011), and followed up semiannually. Antibodies against 7 high-risk HPV types in baseline and 12-month serum samples were tested using a multiplex immunoassay. Baseline, 6-, and 12-month anal and penile samples were tested for HPV DNA using the SPF10-PCR DEIA/LiPA25 system. Statistical analyses were performed using logistic regression with generalized estimating equations.

RESULTS

Of 644 MSM included in the analysis, 245 (38%) were HIV-infected. Median age was 38 years for HIV-negative and 47 years for HIV-infected MSM (P < 0.001). Seroconversion against ≥1 of the 7 HPV types was observed in 74 of 396 (19%) HIV-negative and 52 of 223 (23%) HIV-infected MSM at risk (P = 0.2). Incident [adjusted OR (aOR) 2.0; 95% confidence interval (CI), 1.1-3.4] and persistent (aOR 3.7; 95% CI, 1.5-9.5) anal HPV infections were independently associated with type-specific seroconversion in HIV-negative MSM. In HIV-infected MSM, there was a nonsignificant positive association between penile HPV infection at any time point and seroconversion (aOR 1.7; 95% CI, 0.9-3.2).

CONCLUSIONS

Incident or persistent anal HPV infection was an independent determinant of seroconversion in HIV-negative MSM.

IMPACT

Our data support that seroresponse may vary per anatomic site and that persistent HPV infections are more likely to elicit a detectable humoral immune response.

Glutathione S-transferase L1 multiplex serology as a measure of cumulative infection with human papillomavirus

BACKGROUND

Several assays are used to measure type-specific serological responses to human papillomavirus (HPV), including the bead-based glutathione S-transferase (GST)-L1 multiplex serology assay and virus-like particle (VLP)-based ELISA. We evaluated the high-throughput GST-L1, which is increasingly used in epidemiologic research, as a measure of cumulative HPV infection and future immune protection among HPV-unvaccinated women.

METHODS

We tested enrollment sera from participants in the control arm of the Costa Rica Vaccine Trial (n = 488) for HPV16 and HPV18 using GST-L1, VLP-ELISA, and two assays that measure neutralizing antibodies (cLIA and SEAP-NA). With statistical adjustment for sampling, we compared GST-L1 serostatus to established HPV seropositivity correlates and incident cervical HPV infection using odds ratios. We further compared GST-L1 to VLP-ELISA using pair-wise agreement statistics and by defining alternate assay cutoffs.

RESULTS

Odds of HPV16 GST-L1 seropositivity increased with enrollment age (OR = 1.20 per year, 95%CI 1.03-1.40) and lifetime number of sexual partners (OR = 2.06 per partner, 95%CI 1.49-2.83), with similar results for HPV18. GST-L1 seropositivity did not indicate protection from incident infection over 4 years of follow-up (HPV16 adjusted OR = 1.72, 95%CI 0.95-3.13; HPV18 adjusted OR = 0.38, 95%CI 0.12-1.23). Seroprevalence by GST-L1 (HPV16 and HPV18, respectively) was 5.0% and 5.2%, compared to 19.4% and 23.8% by VLP-ELISA, giving positive agreement of 39.2% and 20.8%. Lowering GST-L1 seropositivity cutoffs improved GST-L1/VLP-ELISA positive agreement to 68.6% (HPV16) and 61.5% (HPV18).

CONCLUSIONS

Our data support GST-L1 as a marker of cumulative HPV infection, but not immune protection. At lower seropositivity cutoffs, GST-L1 better approximates VLP-ELISA.