Immunogenicity of HPV prophylactic vaccines: Serology assays and their use in HPV vaccine evaluation and development

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.

Is syphilis infection a risk factor for cervicovaginal HPV occurrence? A case-control study

BACKGROUND

Syphilis and human papillomavirus (HPV) are sexually transmitted infections affecting women in the same risk group. Thus, the main objective of the present study was to investigate the prevalence of HPV in a population of women with and without syphilis and observe the characteristics of HPV cervical lesions when coinfection occurs. Sociodemographic factors associated with coinfection were also evaluated.

METHODS

This case-control study was conducted at a Brazilian HIV/STD testing and training center. Study groups were composed of women with (case) and without syphilis (control), paired by age. The presence of HPV, HPV subtype, and lesion severity were investigated. All women were subjected to a sociodemographic interview, clinical data collection, cell collection for cytopathological analysis, and a hybrid capture test for HPV diagnosis. The chi-square test was used for statistical analysis.

RESULTS

The sample consisted of 176 women, 88 in each group. The prevalence of HPV was 14.8 % in the case (n = 13) and 18.1 % in the control group (n = 16), and there was no statistically significant difference between them. Illiterate individuals were more prevalent in the control group (p = 0.023). Considering women with suggestive signs of STIs, 30 % (6) of the patients and controls had high-risk HPV, and 15 % (3) had coinfection. The cytopathological assessment showed no differences between the groups concerning cellular atypia. However, ASC-US and ASC-H (atypical squamous cells of undetermined significance and high-grade) were only found in women with coinfections, with 75 % of these patients testing positive for high-risk HPV. Considering the distribution of lesions on the cervix, the HSIL (high-grade intraepithelial lesion) was assessed in high-risk HPV patients, both cases and controls.

CONCLUSIONS

The prevalence of HPV was not increased in patients infected with syphilis. In addition, coinfection does not seem to be an aggravating factor for the presence of precursor lesions of cervical cancer.

Empirical sample-specific approaches to define HPV16 and HPV18 seropositivity in unvaccinated, young, sexually active women

Given low seroconversion rates following human papillomavirus (HPV) infection, fixed external cutoffs may lead to errors in estimating HPV seroprevalence. We evaluated finite mixture modeling (FMM) and group-based trajectory modeling (GBTM) among unvaccinated, sexually active, HPV-exposed women to determine study-specific HPV16 and HPV18 seropositivity thresholds. We included 399 women (aged 18-24 years) enrolled in the HPV Infection and Transmission Among Couples Through Heterosexual Activity (HITCH) cohort study between 2005 and 2011 in Montreal, Canada. Participants' blood samples from up to six visits spanning 2 years were tested by multiplex serology for antibodies [median fluorescence intensity (MFI)] specific to bacterially expressed HPV16 and HPV18 L1 glutathione S-transferase fusion proteins. We applied FMM and GBTM to baseline and longitudinal antibody titer measurements, respectively, to define HPV type-specific seronegative and seropositive distributions. Study-specific thresholds were generated as five standard deviations above the mean seronegative antibody titers, mimicking cutoffs (HPV16: 422 MFI; HPV18: 394 MFI) derived from an external population of sexually inactive, HPV DNA-negative Korean women (aged 15-29 years). Agreement (kappa) of study-specific thresholds was evaluated against external cutoffs. Seroprevalence estimates using FMM (HPV16: 27.5%-43.2%; HPV18: 21.7%-49.5%) and GBTM (HPV16: 11.8%-11.8%; HPV18: 9.9%-13.4%) thresholds exceeded those of external cutoffs (HPV: 10.2%; HPV18: 9.7%). FMM thresholds showed slight-to-moderate agreement with external cutoffs (HPV16: 0.26%-0.46%; HPV18: 0.20%-0.56%), while GBTM thresholds exhibited high agreement (HPV16: 0.92%-0.92%; HPV18: 0.82%-0.99%). Kappa values suggest that GBTM, used for longitudinal serological data, and otherwise FMM, for cross-sectional data, are robust methods for determining the HPV serostatus without prior classification rules.IMPORTANCEWhile human papillomavirus (HPV) seropositivity has been employed as an epidemiologic determinant of the natural history of genital HPV infections, only a fraction of women incidentally infected with HPV respond by developing significant antibody levels. HPV seropositivity is often determined by a dichotomous fixed cutoff based on the seroreactivity of an external population of women presumed as seronegative, given the lack of evidence of HPV exposure. However, considering the variable nature of seroreactivity upon HPV infection, which arguably varies across populations, such externally defined cutoffs may lack specificity to the population of interest, causing inappropriate assessment of HPV seroprevalence and related epidemiologic uses of that information. This study demonstrates that finite mixture modeling (FMM) and group-based trajectory modeling (GBTM) can be used to independently estimate seroprevalence or serve as the basis for defining study-specific seropositivity thresholds without requiring prior subjective assumptions, consequently providing a more apt internally valid discrimination of seropositive from seronegative individuals.

Development of a human papillomavirus (HPV) multiplex immunoassay to profile HPV antibodies

Neutralizing antibodies (NAbs) are considered the primary mechanism of vaccine-mediated protection against human papillomaviruses (HPV), the causative agent of cervical cancer. However, the minimum level of NAb needed for protection is currently unknown. The HPV pseudovirion-based neutralization assay (PBNA) is the gold standard method for assessing HPV antibody responses but is time-consuming and labor-intensive. With the development of higher valency HPV vaccines, alternative serological assays with the capacity for multiplexing would improve efficiency and output. Here we describe a multiplex bead-based immunoassay to characterize the antibody responses to the seven oncogenic HPV types (HPV16/18/31/33/45/52/58) contained in the current licensed nonavalent HPV vaccine. This assay can measure antibody isotypes and subclasses (total IgG, IgM, IgA1-2, IgG1-4), and can be adapted to measure other antibody features (e.g., Fc receptors) that contribute to vaccine immunity. When tested with serum samples from unvaccinated and vaccinated individuals, we found high concordance between HPV-specific IgG using this multiplex assay and NAbs measured with PBNA. Overall, this assay is high-throughput, sample-sparing, and time-saving, providing an alternative to existing assays for the measurement and characterization of HPV antibody responses.

The potential use of therapeutics and prophylactic mRNA vaccines in human papillomavirus (HPV)

Cervical cancer (CC) and other malignant malignancies are acknowledged to be primarily caused by persistent human papillomavirus (HPV) infection. Historically, vaccinations against viruses that produce neutralizing antibodies unique to the virus have been an affordable way to manage viral diseases. CC risk is decreased, but not eliminated, by HPV vaccinations. Since vaccinations have been made available globally, almost 90% of HPV infections have been successfully avoided. On the lesions and diseases that are already present, however, no discernible treatment benefit has been shown. As a result, therapeutic vaccines that elicit immune responses mediated by cells are necessary for the treatment of established infections and cancers. mRNA vaccines possess remarkable potential in combating viral diseases and malignancy as a result of their superior industrial production, safety, and efficacy. Furthermore, considering the expeditiousness of production, the mRNA vaccine exhibits promise as a therapeutic approach targeting HPV. Given that the HPV-encoded early proteins, including oncoproteins E6 and E7, are consistently present in HPV-related cancers and pre-cancerous lesions and have crucial functions in the progression and persistence of HPV-related diseases, they serve as ideal targets for therapeutic HPV vaccines. The action mechanism of HPV and HPV-related cancer mRNA vaccines, their recent advancements in clinical trials, and the potential for their therapeutic applications are highlighted in this study, which also offers a quick summary of the present state of mRNA vaccines. Lastly, we highlight a few difficulties with mRNA HPV vaccination clinical practice and provide our thoughts on further advancements in this quickly changing sector. It is expected that mRNA vaccines will soon be produced quickly for clinical HPV prevention and treatment.

Cervical cancer: Part I human papilloma virus vaccination in Taiwan

A significant decline in both incidence and prevalence of cervical cancers after widespread-introducing cervical screening strategy by Papanicolau test (Pap test) has been found in the world, but cervical cancer is still one of the most common female cancers, reporting the fourth prevalence and also one of the leading causes to result in main women-associated morbidity and mortality, particularly for those women living in low- and middle-income countries. Cervical cancer is one of the most important health concerns directly destroying the global health-care system, partly because of not only increasing the disability either secondary to diseases themselves of victims or mediated by treatment-related adverse events to the survivors but also acting as a leading cause of death of diseased patients worldwide, alarming the urgent need to do something to minimize the catastrophic diseases-related heavy socioeconomic burden. It is fortunate that cervical cancer is a preventable disease, based on its strong association with human papillomavirus (HPV) infection (more than 95%), particularly for those high-risk HPV (HR-HPV) and its high possibility by detecting HPV infection before the development of cervical cancer as well as an effective prevention by HPV vaccination. That is why WHO (World Health Organization) considers cervical cancer as a public problem and attempts to accelerate the elimination of cervical cancer program by three-pillar approach (90:70:90% targets), including (1) 90% of girls are fully vaccinated with HPV vaccine by 15 years of age; (2) 70% of women are screened with a high-performance test by 35 and 45 years of age and precancerous lesions are treated early; and (3) 90% of women identified with cervical diseases receive appropriate and adequate treatment. Herein, this review focuses on the HPV vaccination as Part I, including global recommendations and Taiwan government's policy for HPV vaccination.

Designing a Novel Multiepitope Vaccine from the Human Papilloma Virus E1 and E2 Proteins for Indonesia with Immunoinformatics and Molecular Dynamics Approaches

One of the deadliest malignant cancer in women globally is cervical cancer. Specifically, cervical cancer is the second most common type of cancer in Indonesia. The main infectious agent of cervical cancer is the human papilloma virus (HPV). Although licensed prophylactic vaccines are available, cervical cancer cases are on the rise. Therapy using multiepitope-based vaccines is a very promising therapy for cervical cancer. This study aimed to develop a multiepitope vaccine based on the E1 and E2 proteins of HPV 16, 18, 45, and 52 using in silico. In this study, we develop a novel multiepitope vaccine candidate using an immunoinformatic approach. We predicted the epitopes of the cytotoxic T lymphocyte (CTL) and helper T lymphocyte (HTL) and evaluated their immunogenic properties. Population coverage analysis of qualified epitopes was conducted to determine the successful use of the vaccine worldwide. The epitopes were constructed into a multiepitope vaccine by using AAY linkers between the CTL epitopes and GPGPG linkers between the HTL epitopes. The tertiary structure of the multiepitope vaccine was modeled with AlphaFold and was evaluated by Prosa-web. The results of vaccine construction were analyzed for B-cell epitope prediction, molecular docking with Toll like receptor-4 (TLR4), and molecular dynamics simulation. The results of epitope prediction obtained 4 CTL epitopes and 7 HTL epitopes that are eligible for construction of multiepitope vaccines. Prediction of the physicochemical properties of multiepitope vaccines obtained good results for recombinant protein production. The interaction showed that the interaction of the multiepitope vaccine-TLR4 complex is stable based on the binding free energy value -106.5 kcal/mol. The results of the immune response simulation show that multiepitope vaccine candidates could activate the adaptive and humoral immune systems and generate long-term B-cell memory. According to these results, the development of a multiepitope vaccine with a reverse vaccinology approach is a breakthrough to develop potential cervical cancer therapeutic vaccines.

Global evaluation of lineage-specific human papillomavirus capsid antigenicity using antibodies elicited by natural infection

Human Papillomavirus (HPV) type variants have been classified into lineages and sublineages based upon their whole genome sequence. Here we have examined the specificity of antibodies generated following natural infection with lineage variants of oncogenic types (HPV16, 18, 31, 33, 45, 52 and 58) by testing serum samples assembled from existing archives from women residing in Africa, The Americas, Asia or Europe against representative lineage-specific pseudoviruses for each genotype. We have subjected the resulting neutralizing antibody data to antigenic clustering methods and created relational antigenic profiles for each genotype to inform the delineation of lineage-specific serotypes. For most genotypes, there was evidence of differential recognition of lineage-specific antigens and in some cases of a sufficient magnitude to suggest that some lineages should be considered antigenically distinct within their respective genotypes. These data provide compelling evidence for a degree of lineage specificity within the humoral immune response following natural infection with oncogenic HPV.

HPV vaccination for prevention of head and neck cancer among men

ABSTRACT

The incidence of human papillomavirus (HPV)-associated head and neck cancer (HNC) has been rapidly increasing in developed countries, with HPV-associated HNC now accounting for 70% of all HNC cases. An increased incidence has been noted particularly among males. The disparities in HPV vaccine uptake rates and the increasing number of individuals with HPV-associated HNC suggest a lack of public awareness of both HPV sequelae and prevention options. This review highlights the importance of prophylactic HPV vaccination for preventing HPV-associated HNC, particularly in males. Current evidence substantiates the need for gender-neutral HPV vaccination programs and reinforces the recommendations made by the CDC. This article raises awareness of the association between HPV and HNC as well as the effectiveness of HPV vaccination in HNC prevention.

HPV16/18 Antibody Responses After a Single Dose of Nonavalent HPV Vaccine

OBJECTIVES

A single dose of human papillomavirus (HPV) vaccine would simplify logistics and reduce costs of vaccination programs worldwide. We conducted a phase IIa trial to determine the stability of HPV type-specific antibody responses after a single dose of the nonavalent HPV vaccine, Gardasil9.

METHODS

Two hundred-and-one healthy 9 to 11-year-old girls and boys were enrolled at 2 centers in the United States to receive a prime dose of the nonavalent vaccine at baseline, a delayed dose at month 24, and an optional third dose at month 30. Blood samples were collected to measure HPV type-specific antibodies at baseline and at 6, 12, 18, 24, and 30 months after the prime dose. The primary outcomes were serum HPV16 and HPV18 antibody responses.

RESULTS

In both girls and boys, geometric mean concentrations of HPV16 and HPV18 antibodies increased at 6 months, declined between months 6 to 12, and then remained stable and high (at 20- and 10-times those at baseline for HPV16 and HPV18, respectively) throughout months 12, 18, and 24 (prebooster) visits. Both HPV16 and HPV18 antibody responses demonstrated anamnestic boosting effect at 30-months after the delayed (24-month) booster dose.

CONCLUSIONS

A single dose of the nonavalent HPV vaccine induced persistent and stable HPV16 and HPV18 antibody responses up to 24 months. This study contributes important immunogenicity data to inform feasibility of the single dose HPV vaccination paradigm. Further research is needed to assess the long-term antibody stability and individual clinical and public health benefit of the single dose schedule.

Assay Harmonization Study To Measure Immune Response to SARS-CoV-2 Infection and Vaccines: a Serology Methods Study

The Coronavirus disease 2019 (COVID-19) pandemic presented the scientific community with an immediate need for accurate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serology assays, resulting in an expansion of assay development, some without following a rigorous quality control and validation, and with a wide range of performance characteristics. Vast amounts of data have been gathered on SARS-CoV-2 antibody response; however, performance and ability to compare the results have been challenging. This study seeks to analyze the reliability, sensitivity, specificity, and reproducibility of a set of widely used commercial, in-house, and neutralization serology assays, as well as provide evidence for the feasibility of using the World Health Organization (WHO) International Standard (IS) as a harmonization tool. This study also seeks to demonstrate that binding immunoassays may serve as a practical alternative for the serological study of large sample sets in lieu of expensive, complex, and less reproducible neutralization assays. In this study, commercial assays demonstrated the highest specificity, while in-house assays excelled in antibody sensitivity. As expected, neutralization assays demonstrated high levels of variability but overall good correlations with binding immunoassays, suggesting that binding may be reasonably accurate as well as practical for the study of SARS-CoV-2 serology. All three assay types performed well after WHO IS standardization. The results of this study demonstrate there are high performing serology assays available to the scientific community to rigorously dissect antibody responses to infection and vaccination. IMPORTANCE Previous studies have shown significant variability in SARS-CoV-2 antibody serology assays, highlighting the need for evaluation and comparison of these assays using the same set of samples covering a wide range of antibody responses induced by infection or vaccination. This study demonstrated that there are high performing assays that can be used reliably to evaluate immune responses to SARS-CoV-2 in the context of infection and vaccination. This study also demonstrated the feasibility of harmonizing these assays against the International Standard and provided evidence that the binding immunoassays may have high enough correlation with the neutralization assays to serve as a practical proxy. These results represent an important step in standardizing and harmonizing the many different serological assays used to evaluate COVID-19 immune responses in the population.

Efficacy and Durability of Immune Response after Receipt of HPV Vaccines in People Living with HIV

People living with HIV (PLH) experience higher rates of HPV infection as well as an increased risk of HPV-related disease, including malignancies. Although they are considered a high-priority group for HPV vaccination, there are limited data regarding the long-term immunogenicity and efficacy of HPV vaccines in this population. Seroconversion rates and geometric mean titers elicited by vaccination are lower in PLH compared to immunocompetent participants, especially in individuals with CD4 counts below 200 cells/mm³ and a detectable viral load. The significance of these differences is still unclear, as a correlate of protection has not been identified. Few studies have focused on demonstrating vaccine efficacy in PLH, with variable results depending on the age at vaccination and baseline seropositivity. Although waning humoral immunity for HPV seems to be more rapid in this population, there is evidence that suggests that seropositivity lasts at least 2-4 years following vaccination. Further research is needed to determine the differences between vaccine formulations and the impact of administrating additional doses on durability of immune protection.

Precision and correlation of ED50 and endpoint titer method in measuring HPV vaccine immunogenicity

Cervical cancer, the second leading cause of cancer-related deaths among women, is caused by human papillomavirus (HPV), a sexually transmitted virus. Vaccination is an effective preventive measure against viral infections and subsequent development of cervical cancer. Enzyme-linked immunosorbent assay (ELISA) is commonly used to measure specific binding antibody titers and assess the immunogenicity of test vaccines in preclinical models or clinical volunteers. Two methods of deriving titers, the endpoint titer (ET) and the effective dilution producing a median maximal effective fold of dilution (ED50) with a cut-off value, are widely used. For HPV, a pseudovirion-based neutralization assay (PBNA) is used to measure functional antibody titers. The ELISA binding titers and functional PBNA titers were found to be well-correlated for all nine HPV types tested in the vaccine, consistent with previous studies on HPV 16/18. Comparing the PBNA results with the two titration methods, the ED50 method showed higher precision and a closer correlation with PBNA results, both for individual types and pooled data analysis for all nine types. When comparing the titration results of the ET method based on a cut-off value with the ED50 method using all the data points across the dilution series, the ED50 method demonstrated better precision and a stronger correlation with PBNA results.

The Tumor-Specific Immune Landscape in HPV+ Head and Neck Cancer

Human papillomaviruses (HPVs) are the causative agent of several anogenital cancers as well as head and neck cancers, with HPV+ head and neck squamous cell carcinoma (HNSCC) becoming a rapidly growing public health issue in the Western world. Due its viral etiology and potentially its subanatomical location, HPV+ HNSCC exhibits an immune microenvironment which is more inflamed and thus distinct from HPV-negative HNSCC. Notably, the antigenic landscape in most HPV+ HNSCC tumors extends beyond the classical HPV oncoproteins E6/7 and is extensively targeted by both the humoral and cellular arms of the adaptive immune system. Here, we provide a comprehensive overview of HPV-specific immune responses in patients with HPV+ HNSCC. We highlight the localization, antigen specificity, and differentiation states of humoral and cellular immune responses, and discuss their similarities and differences. Finally, we review currently pursued immunotherapeutic treatment modalities that attempt to harness HPV-specific immune responses for improving clinical outcomes in patients with HPV+ HNSCC.

Serologic Response to Human Papillomavirus Genotypes Among Unvaccinated Women: Findings From the HITCH Cohort Study

BACKGROUND

Humoral immune responses may be critical for preventing, controlling, and/or eliminating human papillomavirus (HPV) infection. We analyzed humoral response to natural HPV infection considering phylogenetic relatedness among unvaccinated women.

METHODS

We included 399 young women attending university/college in Montreal, Canada who were participants of the HITCH cohort. Participants provided blood samples at baseline and 5 follow-up visits. Antibody response to bacterially expressed L1 and E6 glutathione S-transferase (GST) fusion proteins, and virus-like particles (VLP-L1) of Alphapapillomavirus types were measured using multiplex serology. We assessed correlations and associations between HPV types at baseline using Pearson correlation coefficients (r) and univariable linear regressions.

RESULTS

At baseline, > 40% were seropositive for GST-L1 antibodies of at least 1 HPV type. Strong correlations between GST-L1 were observed for α9 HPV types: 58-52 (r = 0.86), 58-33 (r = 0.75), 33-52 (r = 0.72), and between GST-E6: 52-11 (r = 0.84), 52-18 (r = 0.79), 58-33 (r = 0.78), 35-11 (r = 0.76). HPV16 VLP-L1 moderately explained variability in HPV16 GST-L1 (regression coefficient [b] = 0.38, R2 = 43.1%), and HPV45 GST-L1 in HPV18 GST-L1 (b = 0.68, R2 = 42.8%). GST-E6 antibodies accounted for a low to moderate proportion of variability in HPV16 and HPV18 GST-E6 (R2 = 6.4%-62.2%).

CONCLUSIONS

Associations between naturally induced HPV-specific antibodies depend on phylogenetic relatedness.

Differences in HPV-specific antibody Fc-effector functions following Gardasil® and Cervarix® vaccination

Gardasil® (Merck) and Cervarix® (GlaxoSmithKline) both provide protection against infection with Human Papillomavirus 16 (HPV16) and Human Papillomavirus 18 (HPV18), that account for around 70% of cervical cancers. Both vaccines have been shown to induce high levels of neutralizing antibodies and are known to protect against progression beyond cervical intraepithelial neoplasia grade 2 (CIN2+), although Cervarix® has been linked to enhanced protection from progression. However, beyond the transmission-blocking activity of neutralizing antibodies against HPV, no clear correlate of protection has been defined that may explain persistent control and clearance elicited by HPV vaccines. Beyond blocking, antibodies contribute to antiviral activity via the recruitment of the cytotoxic and opsonophagocytic power of the immune system. Thus, here, we used systems serology to comprehensively profile Gardasil®- and Cervarix®- induced antibody subclass, isotype, Fc-receptor binding, and Fc-effector functions against the HPV16 and HPV18 major capsid protein (L1). Overall, both vaccines induced robust functional humoral immune responses against both HPV16 and HPV18. However, Cervarix® elicited higher IgG3 and antibody-dependent complement activating responses, and an overall more coordinated response between HPV16 and 18 compared to Gardasil®, potentially related to the distinct adjuvants delivered with the vaccines. Thus, these data point to robust Fc-effector functions induced by both Gardasil® and Cervarix®, albeit with enhanced coordination observed with Cervarix®, potentially underlying immunological correlates of post-infection control of HPV.

Human papillomavirus-specific antibody status among unvaccinated subjects in the region of Vojvodina, Serbia

OBJECTIVES

The aim of the study was to evaluate the immune status of young people from the Vojvodina province, Serbia, through the detection of IgG antibodies specific for the L1 protein of HPV types 6, 11, 16, and 18 contained in quadrivalent vaccine.

METHODS

The study enrolled 514 healthy persons of both genders, aged between 18 and 30 years. All potential participants were informed about the project's aims by trained interviewers before venous blood collection. Also, participants completed a specially designed anonymous questionnaire to identify socio-demographic characteristics and individual behaviours associated with HPV seroprevalence. VPL HPV L1-specific IgG antibodies were measured using a semi-quantitative HPV IgG ELISA kit (Dia.Pro, Italy).

RESULTS

A total of 472 (91.8%) young subjects had no detectable antibodies against high- and low-risk HPV types covered by the quadrivalent vaccine. A slightly higher number of seropositive individuals were detected in the age group of 26-30 years compared to younger than 25. Multivariate analysis showed that the number of lifetime sexual partners was the most powerful predictor of HPV seropositivity (OR = 3.483, 95% CI: 1.294-9.379).

CONCLUSIONS

Obtained data point out low levels of naturally induced HPV-specific serum antibodies among the target population in the Vojvodina province. The present work highlights the significance and potential benefits of HPV vaccination. Routine HPV vaccination should be the public health priority in our country and should be included in the national immunization programme as soon as possible.

Single-dose HPV vaccine immunity: is there a role for non-neutralizing antibodies?

A single dose of human papillomavirus (HPV) vaccine against HPV infection (prerequisite for cervical cancer) appears to be as efficacious as two or three doses, despite inducing lower antibody titers. Neutralizing antibodies are thought to be the primary mediator of protection, but the threshold for protection is unknown. Antibody functions beyond neutralization have not been explored for HPV vaccines. Here, we discuss the immune mechanisms of HPV vaccines, with a focus on non-neutralizing antibody effector functions. In the context of single-dose HPV vaccination where antibody is limiting, we propose that non-neutralizing antibody functions may contribute to preventing HPV infection. Understanding the immunological basis of protection for single-dose HPV vaccination will provide a rationale for implementing single-dose HPV vaccine regimens.

Optimization of a protocol for the evaluation of antibody responses to human papillomavirus (HPV) vaccination in low-resource settings

Introduction

Available human papillomavirus (HPV) vaccines could have an important primary role in cervical cancer prevention once their long-term immunogenicity and safety are evaluated at the population level. The aim of this study was to optimize an assay to be used in evaluating the long-term durability of HPV vaccine response following a pilot vaccination of adolescent girls in Ghana.

Methods

A rapid, high-throughput, indirect enzyme-linked immunosorbent assay (ELISA) was optimized for the detection and quantitation of anti-HPV L1 (late expression protein: types 6, 11, 16 and 18) immunoglobulin G (IgG) in human serum (n = 89). The utility of the assay was demonstrated using serum collected from a cohort of pre-adolescent girls (n = 49) previously vaccinated with a quadrivalent vaccine and non-immune serum obtained from age-matched controls (n = 40).

Results

The assay showed good discrimination of antibody levels between cases and control sera: seroprevalence of anti-HPV IgG antibodies was significantly higher among vaccinated than unvaccinated girls for both HPV-16 (63.3% vs. 12.5%; p < 0.001) and HPV-18 (34.7% vs. 20.0%; p = 0.042), respectively. Thirty-six months after receiving the third dose of vaccine, significantly higher mean anti-HPV-16 (0.618 vs. 0.145), anti-HPV-18 (0.323 vs. 0.309), and anti-HPV-6 (1.371 vs. 0.981) antibody levels were measured, compared to unvaccinated girls (all p < 0.05). A correlation between optical density and antibody activity indicated assay sensitivity to increasing levels of antibody activity.

Conclusion

We have successfully optimized and implemented a robust and sensitive assay for the evaluation of antibody responses among immunized adolescent girls for monitoring future large-scale HPV vaccination studies in low-income settings. Our results demonstrated greater immunoglobulin G antibody activity within serum drawn from adolescent girls immunized 36 months prior.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12905-022-01821-y.

Outcomes After Human Papillomavirus Vaccination in Patients With Recurrent Respiratory Papillomatosis: A Nonrandomized Clinical Trial

Importance

Recurrent respiratory papillomatosis (RRP) is a rare benign chronic disease of the larynx etiologically linked with the infection of low-risk human papillomavirus (HPV). Combination of surgical and immunomodulatory therapy has limited success. Possible use of prophylactic HPV vaccine that includes HPV-6 and HPV-11 antigens has been studied.

Objective

To evaluate if the HPV vaccination is associated with a lower number of recurrences requiring surgical intervention in patients with new and recurrent RRP.

Design, Setting, and Participants

This was a non-placebo-controlled intervention study. Enrollment data were collected from October 2011 to August 2013. The patients were followed up at 1 month, 12 months, and 5 years after the third dose of the vaccine and clinically monitored until December 31, 2018. Data were analyzed from 2019 to 2021. Altogether, 50 adults with active RRP were enrolled and followed up in referral centers. For the final outcome, follow-up data for 42 patients were available. Eight patients who did not fulfill the protocol were excluded.

Interventions

All patients received HPV vaccine as an adjuvant treatment and were clinically followed up. When RRP progression or a significant recurrent lesion was detected, surgical removal via direct laryngoscopy was indicated. No adjuvant therapy with antiviral or biological agents was used.

Main Outcomes and Measures

This study compared the prevaccination and postvaccination positivity for HPV-specific antibodies. The main outcome was the difference in the frequency of RRP recurrences in the prevaccination and postvaccination period.

Results

A total of 50 patients with RRP were enrolled (median [SD] age, 41.5 [12.3] years [range, 21-73 years]; 39 [78%] men and 11 [22%] women). After HPV vaccination, patients with previously no HPV-specific antibodies showed seroconversion, and all patients developed 100-fold higher levels of HPV vaccine type-specific antibodies compared with the prevaccination period. In patients with recurrent RRP, decreased frequency of recurrences requiring surgical treatment was present after vaccination (from 0.85 to 0.36 recurrences/y). No difference in postvaccination recurrences was found between patients with newly diagnosed and recurrent RRP.

Conclusions and Relevance

In this nonrandomized clinical trial, the frequency of RRP recurrences was significantly lower after HPV vaccination, and patients with RRP thus had a reduced burden of disease. Because no difference was detected in the frequency of recurrent postvaccination lesions in patients with new and recurrent disease, it appears that both groups showed equal benefit following HPV vaccination. These findings suggest that the earlier that patients with RRP receive HPV vaccine, the sooner they may show reduced burden of disease.

Trial Registration

EudraCT Identifier: 2011-002667-14; ClinicalTrials.gov Identifier: NCT01375868.

Adherence to the Recommended HPV Vaccine Dosing Schedule among Adolescents Aged 13 to 17 Years: Findings from the National Immunization Survey-Teen, 2019–2020

The 9-valent human papillomavirus (9-vHPV) vaccine uptake rate among adolescents has improved over the years; however, little is known about the adherence to the recommended dosing schedule. This study examines the prevalence and factors associated with adherence to the recommended 9vHPV vaccination dosing schedule among adolescents aged 13 to 17 years. The cross-sectional study was conducted using the 2019–2020 National Immunization Survey-Teen. The parents of 34,619 adolescents were included in our analyses. The overall up-to-date (UTD) prevalence was 57.1%. The UTD prevalence was 60.0% among females and 54.2% among males. Adolescents aged 16 years had the highest UTD prevalence of 63.0%. The UTD prevalence was 61.6% among Hispanics and 54.7% among non-Hispanic Whites. Overall, compared to females, males had 14% lower odds of UTD. The odds of UTD were 1.91 times, 2.08 times, and 1.98 times higher among adolescents aged 15–17 years, respectively, compared to those aged 13 years. Moreover, region, poverty, insurance status, mothers’ educational level, and provider recommendation were associated with UTD. Our findings show that adherence to the recommended 9vHPV vaccine schedule is low in the US. Targeted public health efforts are needed to improve the rates of adherence to the recommended 9vHPV dose schedule.

Homologous and Heterologous Anti-COVID-19 Vaccination Does Not Induce New-Onset Formation of Autoantibodies Typically Accompanying Lupus Erythematodes, Rheumatoid Arthritis, Celiac Disease and Antiphospholipid Syndrome

The COVID-19 pandemics has caused the death of almost six million people worldwide. In order to establish collective immunity, the first vaccines that were approved in Germany were the vector virus-based vaccine Vaxzevria and the mRNA vaccines Comirnaty and Spikevax, respectively. As it was reported that SARS-CoV-2 can trigger autoimmunity, it is of significant interest to investigate whether COVID-19 vaccines evoke the formation of autoantibodies and subsequent autoimmunity. Here, we analyzed immune responses after different vaccination regimens (mRNA/mRNA, Vector/Vector or Vector/mRNA) with respect to anti-SARS-CoV-2-specific immunity and the development of autoantibodies well known for their appearance in distinct autoimmune diseases. We found that anti-SARS-CoV-2 antibody levels were 90% lower after Vector/Vector vaccination compared to the other vaccinations and that Vector/mRNA vaccination was more effective than mRNA/mRNA vaccination in terms of IgM and IgA responses. However, until 4 months after booster vaccination we only detected increases in autoantibodies in participants with already pre-existing autoantibodies whereas vaccinees showing no autoantibody formation before vaccination did not respond with sustained autoantibody production. Taken together, our study suggests that all used COVID-19 vaccines do not significantly foster the appearance of autoantibodies commonly associated with lupus erythematodes, rheumatoid arthritis, Celiac disease and antiphospholipid-syndrome but provide immunity to SARS-CoV-2.

Impact of one and two human papillomavirus (HPV) vaccine doses on community-level HPV prevalence in South African adolescent girls: study protocol and rationale for a pragmatic before-after design

INTRODUCTION

Vaccines against human papillomavirus (HPV) are the key to controlling cervical cancer in low/middle-income countries (LMICs) where incidence is highest, but there have been limited data from these settings on programme impact on HPV prevalence, and none in a population with endemic HIV infection. Furthermore, for many LMICs, the currently recommended two-dose schedule is difficult to deliver at scale, so there is mounting interest in a single-dose schedule.

METHODS AND ANALYSIS

The Human Papillomavirus One and Two-Dose Population Effectiveness Study is a hybrid impact evaluation of the national South African HPV vaccination programme, which has targeted grade 4 girls aged at least 9 years in public schools with two doses of vaccine since 2014, and a single-dose vaccine 'catch-up' programme delivered in one district in 2019. Impacts of both schedules on the prevalence of type-specific HPV infection will be measured using repeat cross-sectional surveys in adolescent girls and young women aged 17-18 years recruited at primary healthcare clinics in the four provinces. A baseline survey in 2019 measured HPV prevalence in the cohort who were ineligible for vaccination because they were already above the target age or grade under either the national programme or the single-dose programme in the selected district. HPV prevalence surveys are repeated in 2021 in the selected district, and in 2023 in all four provinces. We will calculate prevalence ratios to compare the prevalence of HPV types 16 and 18 in the single-dose (2021) and two-dose (2023) cohorts, with the vaccine-ineligible (2019) cohort.

ETHICS AND DISSEMINATION

The project was approved by the University of the Witwatersrand Human Research Ethics Committee (HREC #181005), and the University of New South Wales HREC (#181-005). Findings will be disseminated through peer-reviewed journals, scientific meetings, reports and community forums.

Maternal HPV-antibodies and seroconversion to HPV in children during the first 3 years of life

To assess the dynamics of human papillomavirus (HPV) serology, we analyzed HPV6-,11-,16-,18-, and 45 antibodies in infants during the first 36 months of their life. Serial serum samples of 276/327 mother–child pairs were collected at baseline (mothers) and at months 1, 2, 6, 12, 24 and 36 (offspring), and tested for HPVL1-antibodies using the GST-L1 assay. Concordance between maternal and infant HPV-antibody levels remained high until month-6 (p <  = 0.001), indicating maternal antibody transfer. At 1 month, 40–62% of the infants tested seropositive to any of the 5 HPV-types. Between 1–3 years of age, 53% (58/109) of the children born to HPV-seronegative mothers tested HPV-seropositive. Times to positive seroconversion varied between13.4 and 18.7 months, and times to negative seroconversion (decay) between 8.5 and 9.9 months. Significant independent predictors of infants’ seroconversion to LR-HPV were hand warts and mother’s history of oral warts and seroconversion to LR-HPV. No predictors of seroconversion to HR-HPV were identified. Maternal HPV-IgG-antibodies are transferred to her offspring and remain detectable for 6 months, corroborating the IgG molecule’s half-life. Seroconversion to HPV-genotypes 6, 11, 16 and 18 was confirmed among children born to HPV-seronegative mothers, implicating an immune response to these HPV-genotypes during early infancy.

Multiplex Human Papillomavirus L1L2 virus-like particle antibody binding assay

A variety of in vitro techniques are available to estimate the level of antibodies present in human serum samples. Such tests are highly specific and are used to determine prior exposure to a pathogen or to estimate the magnitude, breadth and durability of individual and population level vaccine immunity. Multiplex (or multi-analyte) platforms are increasingly being used to evaluate immune responses against multiple antigens at the same time, usually at reduced per sample cost and a more efficient use of available samples. Consequently, multiplex serology is an essential component of a wide range of public health programmes. Human papillomavirus (HPV) serology is limited to a small number of academic, public health and vaccine manufacturer laboratories globally. Such platforms include indirect binding to the major (L1) capsid protein virus-like particles (VLP), monoclonal antibody competition against L1 VLP and indirect binding to L1 and L2 (minor capsid protein) VLP on multiplex (Luminex®, Meso Scale Discovery®) and standard (ELISA) platforms. The methodology described here utilizes a common multi-analyte platform and L1L2-based VLP expressed in house, which allows the simultaneous detection and quantification of antibody responses against nine vaccine-relevant HPV genotypes.

Serological Response to SARS-CoV-2 Messenger RNA Vaccine: Real-World Evidence from Italian Adult Population

BACKGROUND

This study aims to investigate the extent of the BNT162b2 mRNA vaccine-induced antibodies against SARS-CoV-2 in a large cohort of Italian subjects belonging to the early vaccinated cohort in Italy.

METHODS

A prospective study was conducted between December 2020 and May 2021. Three blood samples were collected for each participant: one at the time of the first vaccine dose (T0), one at the time of the second vaccine dose, (T1) and the third 30 days after this last dose (T2).

RESULTS

We enrolled 2591 fully vaccinated subjects; 16.5% were frail subjects, and 9.8% were over 80 years old. Overall, 98.1% of subjects were seropositive when tested at T2, and 76.3% developed an anti-S IgG titer ≥4160 AU/mL, which is adequate to develop viral neutralizing antibodies. Seronegative subjects at T1 were more likely to remain seronegative at T2 or to develop a low-intermediate anti-S IgG titer (51-4159 AU/mL).

CONCLUSIONS

In summary, vaccination leads to detectable anti-S IgG titer in nearly all vaccine recipients. Stratification of the seroconversion level could be useful to promptly identify high-risk groups who may not develop a viral neutralizing response, even in the presence of seroconversion, and therefore may remain at higher risk of infection, despite vaccination.

Human Papillomavirus Vaccine Efficacy and Effectiveness against Cancer

Human papillomavirus (HPV) is the most common sexually transmitted infection, with 15 HPV types related to cervical, anal, oropharyngeal, penile, vulvar, and vaginal cancers. However, cervical cancer remains one of the most common cancers in women, especially in developing countries. Three HPV vaccines have been licensed: bivalent (Cervarix, GSK, Rixensart, Belgium), quadrivalent (Merck, Sharp & Dome (Merck & Co, Whitehouse Station, NJ, USA)), and nonavalent (Merck, Sharp & Dome (Merck & Co, Whitehouse Station, NJ, USA)). The current HPV vaccine recommendations apply to 9 years old and above through the age of 26 years and adults aged 27–45 years who might be at risk of new HPV infection and benefit from vaccination. The primary target population for HPV vaccination recommended by the WHO is girls aged 9–14 years, prior to their becoming sexually active, to undergo a two-dose schedule and girls ≥ 15 years of age, to undergo a three-dose schedule. Safety data for HPV vaccines have indicated that they are safe. The most common adverse side-effect was local symptoms. HPV vaccines are highly immunogenic. The efficacy and effectiveness of vaccines has been remarkably high among young women who were HPV seronegative before vaccination. Vaccine efficacy was lower among women regardless of HPV DNA when vaccinated and among adult women. Comparisons of the efficacy of bivalent, quadrivalent, and nonavalent vaccines against HPV 16/18 showed that they are similar. However, the nonavalent vaccine can provide additional protection against HPV 31/33/45/52/58. In a real-world setting, the notable decrease of HPV 6/11/16/18 among vaccinated women compared with unvaccinated women shows the vaccine to be highly effective. Moreover, the direct effect of the nonavalent vaccine with the cross-protection of bivalent and quadrivalent vaccines results in the reduction of HPV 6/11/16/18/31/33/45/52/58. HPV vaccination has been shown to provide herd protection as well. Two-dose HPV vaccine schedules showed no difference in seroconversion from three-dose schedules. However, the use of a single-dose HPV vaccination schedule remains controversial. For males, the quadrivalent HPV vaccine possibly reduces the incidence of external genital lesions and persistent infection with HPV 6/11/16/18. Evidence regarding the efficacy and risk of HPV vaccination and HIV infection remains limited. HPV vaccination has been shown to be highly effective against oral HPV type 16/18 infection, with a significant percentage of participants developing IgG antibodies in the oral fluid post vaccination. However, the vaccines’ effectiveness in reducing the incidence of and mortality rates from HPV-related head and neck cancers should be observed in the long term. In anal infections and anal intraepithelial neoplasia, the vaccines demonstrate high efficacy. While HPV vaccines are very effective, screening for related cancers, as per guidelines, is still recommended.

The Role of Serology Testing in the Context of Immunization Policies for COVID-19 in Latin American Countries

This review aims to explore the role and value of serology testing in the context of COVID-19 immunization policies in Latin American countries and the barriers and challenges to the adequate use and uptake of this tool. It builds on a review of the academic literature, evidence, and existing policies, and includes a multistage process of discussion and feedback by a group of five experts. Regional and country-level evidence and resources from five focus countries-Argentina, Brazil, Chile, Colombia, and Mexico-were collected and analyzed. This review contains an overview of (1) the impact of the SARS-CoV-2 pandemic, the variants of concern and current testing strategies, (2) the introduction of COVID-19 vaccination, (3) the potential use of serology testing to support immunization initiatives, (4) the current frameworks for the use of serology testing in the region, and (5) the barriers and challenges to implementing serology testing in the context of COVID-19 immunization policies, including a discussion on the potential actions required to address these barriers and facilitate the uptake of this strategy in the region. Stakeholders can use elements of this document to guide timely decision-making, raise awareness, and inspire further studies.

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.

Review of long-term immunogenicity following HPV vaccination: Gaps in current knowledge

The licensed HPV vaccines are highly efficacious and induce high levels of neutralizing antibody levels, the assumed mediators of protection. However, a correlate of protection against HPV is lacking, and the evidence is still limited as to long-term persistence of antibodies, especially following reduced dosing schedules. The World Health Organization (WHO) urges immunization of young girls as part of the strategy to eliminate cervical cancer, thus long-lasting protection is required. The current review describes long-term follow-up regarding vaccine-induced seropositivity and antibody level development following the different vaccines and dosing schedules. Implications and opportunities of long-term vaccine-induced immune responses are discussed, such as the gaps in monitoring of long-term immunogenicity, the possibilities of reduced dosing schedules, and the importance of evidence for durable immunity.

Immunogenicity of 2 and 3 Doses of the Quadrivalent Human Papillomavirus Vaccine up to 120 Months Postvaccination: Follow-up of a Randomized Clinical Trial

Background

Several countries have implemented a 2-dose (2D) human papillomavirus (HPV) vaccination schedule for adolescents based on immunobridging studies. We compared immunogenicity of 2D vs 3-dose (3D) schedules of the quadrivalent vaccine (4vHPV) up to 10 years after the first dose.

Methods

Girls aged 9–13 years were randomized to receive 2D or 3D and were compared with women aged 16–26 receiving 3D at day 1 and months 7, 24, and 120 after the first dose. Antibody levels for HPV6/11/16/18 were evaluated using the competitive Luminex immunoassay (cLIA) and total immunoglobulin G assay. Geometric mean titers (GMTs) and seropositivity rates were compared between the different groups at different time points. Noninferiority of GMT ratios was defined as the lower bound of the 2-sided 95% confidence interval (CI) being greater than 0.5. Kinetics of antibody titers over time among study groups were examined.

Results

At 120 months, data from 35 2D girls, 38 3D girls, and 30 3D women were used for analyses. cLIA seropositivity rates were above 95% for all HPV vaccine types and all schedules, except HPV18, with the lowest seropositivity observed among 3D women (60.0%; 95% CI, 40.6%–77.3%). GMT ratios (cLIA) for both 2D and 3D girls were noninferior to 3 doses in women for HPV6/11/16/18. Trends were comparable between assays.

Conclusions

GMTs for HPV6/11/16/18 after 2D or 3D of 4vHPV in girls were noninferior to 3D in adult women up to 120 months postvaccination. This study demonstrates long-term immunogenicity of the 2D HPV vaccine schedule.

High Prevalence of Cervical High-Risk Human Papillomavirus Harboring Atypical Genotypes in Human Immunodeficiency Virus -Infected and -Uninfected First-Generation Adult Immigrant Women Originating from Sub-Saharan Africa and Living in France

Human papillomavirus (HPV)-related cervical lesions in first-generation immigrant African women in France should reflect the epidemiology of high-risk (HR)-human papillomavirus (HPV) infection in sub-Saharan Africa. First-generation immigrant African women attending the Centre Hospitalier Régional of Orléans, France, were prospectively subjected to endocervical swabs for HPV DNA PCR and Pap smear. Fifty women (mean age, 41.7 years) living in France (mean stay, 10.7 years) were enrolled, including 26.0% of HIV-negative women from general population and 74.0% of women with known HIV infection. Cervical HPV prevalence was 68.0%, with 56.0% of HR-HPV. HR-HPV -68 and -58 were the predominant genotypes (20.0% and 14.0%, respectively). HR-HPV-16 and HR-HPV-18 were infrequently detected. HIV-infected women showed a trend to be more frequently infected by HPV than HIV-negative women (70.3% versus 61.5%). Most women (84.0%) showed normal cytology, while the remaining (16.0%) exhibited cervical abnormalities and were frequently HIV-infected (87.5%). These observations highlight the unsuspected high burden of cervical HR-HPV infections mostly associated with atypical genotypes, HIV infection and cervical abnormalities in first-generation immigrant African women living in France.

Systematic review and meta-analysis of HPV vaccination in women with systemic lupus erythematosus (SLE)

OBJECTIVE

We conducted a systematic review and meta-analysis to access HPV vaccines' safety and immunogenicity in Systemic Lupus Erythematosus (SLE) women.

METHODS

The search was conducted in the most relevant databases. Meta-analyses to evaluate seroconversion rates for each HPV vaccine type and SLE flare rates after vaccination were performed.

RESULTS

We identified 3,467 articles; six papers referring to SLE population were included. Five articles that evaluated vaccine immunogenicity at 7th month after enrollment were included in the meta-analysis. Overall seroconversion rates among SLE participants were 89.3% (95%CI, 0.76-1.00) for HPV6; 92.4% (95%CI, 0.82-1.00) for HPV11; 96.4% (95%CI, 0.93-1.00) for HPV16; and 91.8% (95%CI, 0.85-1.00) for HPV18. Five studies were included in the qualitative analysis of vaccines safety. Pain at the injection site was the most common adverse event (AE). Just one study reported serious AE not related to the vaccine. Flare rate after HPV vaccination was 12,6% (95% CI, 0.04-0.21).

CONCLUSION

Few studies, small sample size, evaluated HPV vaccines in SLE women. Seroconversion rates in SLE women were like healthy women, but anti-HPV geometric mean titers (GMT) were slightly lower in SLE women. HPV vaccines were safe in this population.

Worldwide genetic variations in high-risk human papillomaviruses capsid L1 gene and their impact on vaccine efficiency

BACKGROUND

Human papillomavirus is the most common sexually transmitted infection. It is associated with different cancers, mainly cervical cancer, which remains the fourth most frequent cancer among women worldwide; it is also related to anogenital (anus, vulvar, vagina, and penis) and oropharyngeal cancers. Vaccination against HPV infection is the major way of prevention, and it has demonstrated impressive efficacy in reducing cervical cancer incidence. Nowadays, all the licensed HPV recombinant vaccines were designed based on HPV major capsid L1 protein. However, some variations in the HPV L1 gene sequence may induce structural changes within the L1 protein, which may alter the affinity and interaction of monoclonal antibodies (MAbs) with L1 protein epitopes, and influence host immune response and recognition. Hence, the importance of accuracy in delineating epitopes relevant to vaccine design and defining genetic variations within antigenic regions in the L1 gene to predict its impact on prophylactic vaccine efficiency. The present review reports the sequence variations in HR-HPV L1 gene isolates from different countries around the world, which may help to understand the effect of HPV L1 gene variations on vaccine efficiency.

METHODS

Research studies were retrieved from PubMed, Google Scholar, Science direct, and the National Center for Biotechnology Information (NCBI) database. A total of 31 articles describing genetic variations within the major capsid L1 gene and conducted in Africa, Europe, America and Asia were found. Only 26 studies conducted on HPV16, 18, 31, 33, 58, 45 and 52 which are the targets of HPV prophylactic vaccines, and which reported genetic variations within the L1 gene, were selected and evaluated in this review.

FINDINGS

We found a total of 87, 49, 11, 7, 22, 3, and 17 non-synonymous single nucleotide polymorphisms (SNPs) within HPV16, HPV18, HPV31, HPV58, HPV45, and HPV52 L1 gene, respectively. Four mutations were frequently observed in HPV16 L1 sequences: T353P in the HI loop, H228D in the EF loop, T266A in the FG loop, and T292A in the FG loop. Two mutations in HPV58 L1 sequences: T375N in the HI loop and L150F in the DE loop. Three mutations in HPV33 L1 sequences: T56N in the BC loop, G133S in the DE loop, T266K in the FG loop. Other mutations were found in HPV18, HPV45, and HPV52 L1 sequences. Some were found in different countries, and others were specific to a given population. Furthermore, some variations were located on peptide binding epitopes and lead to a modification of epitopes, which may influence MAbs interactions. Others need further investigations due to the lack of studies.

CONCLUSION

This study investigated the major capsid L1 genetic diversity of HPV16, 18, 31, 33, 58, 45, and 52 circulating in different populations around the world. Further investigations should be conducted to confirm their effect on immunogenicity and prophylactic vaccine efficiency.

Measurement of Human Papillomavirus-Specific Antibodies Using a Pseudovirion-Based ELISA Method

Human papillomavirus (HPV) vaccines are safe and effective in preventing HPV infection and cervical precancers. Neutralizing antibodies are thought to be the primary mechanism of protection for HPV vaccines, although the exact level required for protection has not been identified. Three common serological assays used in clinical trials to measure HPV antibodies are HPV pseudovirion-based neutralization assay (PBNA), competitive or total Luminex immunoassays (cLIA or LIA) and VLP-based enzyme linked immunosorbent assays (ELISA). While PBNA is the gold-standard for measuring neutralizing antibodies (NAb), it is labor intensive. Luminex immunoassay and VLP-ELISA are rapid and high throughput, but their reagents and equipment can be difficult to source. Nevertheless, data generated from these assays generally correlate well with PBNA. Here, we described a simplified high-throughput PsV-based ELISA for HPV antibody measurement, to circumvent some of the limitations of existing assays. Using this assay, we were able to differentiate HPV-specific IgG and IgM, and found a strong correlation between HPV-specific IgG and NAb levels, as previously determined by PBNA. This assay platform is simpler and less time-consuming than PBNA. In addition, the materials can be readily produced and obtained commercially. This assay can be used as an alternative method to measure HPV antibodies.

Cross-Protective IgG and IgA Antibodies against Oncogenic and Non-Oncogenic HPV Genotypes

OBJECTIVE

The aim of the study was to describe the course of IgG/IgA immune response in women immunized with bivalent vaccine and in women non-vaccinated with HPV infection, as well as evaluating the cross-protection against non-vaccine HPV types.

METHODS

Serum and cervical mucus samples were collected from infected and vaccinated women for HPV detection/genotyping and for detection of IgG/IgA anti-HPV/VLP (Virus-like Particles) by ELISA.

RESULTS

The median absorbance detected in serum samples for anti-HPV-IgG antibodies was higher in vaccinated women when compared to HPV infected women (p <0.01), however, the median absorbance in cervical mucus samples for anti-HPV-IgA was higher in infected women when compared to vaccinated women (p <0.01). Additionally, our analyses also provided additional evidence for cross-protective efficacy of the HPV-16/18 vaccine against HPV-82, -6, -11, -13, -61, -72 and -74.

CONCLUSION

The IgG antibodies were significantly more detected in the serum of vaccinated women, while the IgA was found in greater quantities in cervical samples from those infected by the virus. In addition, there is evidence that the bivalent vaccine provides cross-protection against other non-oncogenic viral subtypes.
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Evaluation of serological assays to monitor antibody responses to single-dose HPV vaccines

INTRODUCTION

Whether existing serological assays are sufficiently robust to measure the lower antibody levels expected following single-dose HPV vaccination is unknown.

METHODS

We evaluated seven assays measuring HPV-16/18 immunological responses overall and by number of doses in 530 serum samples from participants receiving varying doses of Cervarix or Gardasil up to 36-months post-vaccination. Serum was evaluated by simplex (HPV-16 ELISA, HPV-18 ELISA), multiplex (LIA-4, VLP-MIA, M9ELISA, GST-L1), and high-throughput pseudovirion-based neutralization assays (HT-PBNA), and results were compared to the gold standard HPV-16/18 secreted alkaline phosphatase neutralization assay (SEAP-NA). Reproducibility was assessed by the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Percent agreement, Pearson correlation, and weighted-kappa were used to assess validity. Determinants of seronegativity were evaluated by chi-squared test.

RESULTS

HPV-16: Seropositivity range was 97.1-99.5% for single dose and 98.8-99.8% overall. CV range was 4.0-18.0% for single dose and 2.9-19.5% overall. ICC range was 0.77-0.99 for single dose and 0.74-0.99 overall. Correlation with SEAP-NA range was 0.43-0.85 for single dose and 0.51-0.90 overall. Weighted-kappa range was 0.34-0.82 for single dose and 0.45-0.84 overall. HPV-18: Seropositivity range was 63.9-94.7% for single dose and 86.2-97.9% overall. CV range was 8.1-18.2% for single dose and 4.6-18.6% overall. ICC range was 0.75-0.99 for single dose and 0.83-0.99 overall. Correlation with SEAP-NA range was 0.31-0.99 for single dose and 0.27-0.96 overall. Weighted-kappa range was 0.35-0.83 for single dose and 0.45-0.84 overall. HPV-16 seronegativity was <5% for all assays. HPV-18 seronegativity range was 5.5-17.3%. For LIA-4 and GST-L1 where the proportion of seronegativity was >10%, the strongest correlates of seronegativity were receiving a single vaccine dose and receiving Gardasil.

CONCLUSIONS

These results support the utility of existing serological assays to monitor antibody responses following single-dose HPV vaccination.

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.

Serum and cervicovaginal IgG immune responses against α7 and α9 HPV in non-vaccinated women at risk for cervical cancer: Implication for catch-up prophylactic HPV vaccination

BACKGROUND

Cervical cancer associated with high risk-human papillomavirus (HR-HPV) infection is becoming the one of the most common female cancer in many sub-Saharan African countries. First-generation immigrant African women living in Europe are at-risk for cervical cancer, in a context of social vulnerability, with frequent lack of cervical cancer screening and HPV vaccination.

OBJECTIVE

Our objective was to address immunologically the issue of catch-up prophylactic HPV vaccination in first-generation African immigrant women living in France.

METHODS

IgG immune responses and cross-reactivities to α7 (HPV-18, -45 and -68) and α9 (HPV-16, -31, -33, -35, -52 and -58) HPV types, including 7 HR-HPV targeted by the Gardasil-9® prophylactic vaccine, were evaluated in paired serum and cervicovaginal secretions (CVS) by HPV L1-virus-like particles-based ELISA. Genital HPV were detected by multiplex real time PCR (Seegene, Seoul, South Korea).

RESULTS

Fifty-one immigrant women (mean age, 41.7 years; 72.5% HIV-infected) were prospectively included. More than two-third (68.6%) of them carried genital HPV (group I) while 31.4% were negative (group II). The majority (90.2%) exhibited serum IgG to at least one α7/α9 HR-HPV. Serum HPV-specific IgG were more frequently detected in group I than group II (100% versus 68.7%; P = 0.002). The distribution of serum and genital HPV-specific IgG was similar, but mean number of IgG reactivities to α7/α9 HR-HPV was higher in serum than CVS (5.6 IgG per woman in serum versus 3.2 in CVS; P<0.001). Rates of IgG cross-reactivities against HPV different from detected cervicovaginal HPV were higher in serum and CVS in group I than group II. Finally, the majority of groups I and II women (68.6% and 68.7%, respectively) exhibited serum or cervicovaginal IgG to Gardasil-9® HR-HPV, with higher mean rates in group I than group II (6.1 Gardasil-9® HR-HPV per woman versus 1.4; P<0.01). One-third (31.2%) of group II women did not show any serum and genital HPV-specific IgG.

CONCLUSIONS

Around two-third of first-generation African immigrant women living in France showed frequent ongoing genital HPV infection and high rates of circulating and genital IgG to α7/α9 HPV, generally cross-reacting, avoiding the possibility of catch-up vaccination. Nevertheless, about one-third of women had no evidence of previous HPV infection, or showed only low levels of genital and circulating HR-HPV-specific IgG and could therefore be eligible for catch-up vaccination.

Natural and vaccine-induced B cell-derived systemic and mucosal humoral immunity to human papillomavirus

Introduction: Human papillomavirus (HPV) are the causative agent of mucosal neoplasia. Both cervical, anal and oropharyngeal cancers incidence is constantly increasing, making the HPV infection, a significant worldwide concern. Together, the CD8+ T cytotoxic cell-mediated response and the HPV-specific antibody response control most of the HPV infections before the development of cancers.Areas covered: We searched the MEDLINE and EMBASE databases and identified 228 eligible studies from 1987 to 2019 which examines both naturally acquired and vaccine induced humoral immunity against HPV infection in female and male subjects from worldwide origin. Herein, we synthesize current knowledge on the features of systemic and mucosal humoral immunity against HPV. We discuss the issues of the balance between the viral clearance or the escape to the host immune response, the differences between natural and vaccine-induced HPV-specific antibodies and their neutralizing capability. We also discuss the protection afforded after natural infection or following prophylactic vaccination.Expert opinion: Understanding the antibody response induced by HPV infection has led to the design of first-generation prophylactic vaccines. Now, prophylactic vaccination induces protective and long-lasting antibody response which would also strengthened the natural moderate humoral response in people previously exposed to the virus.

Prophylactic human papillomavirus vaccination to prevent recurrence of cervical intraepithelial neoplasia: a meta-analysis

Objective

The aim of this systematic review and meta-analysis was to review evidence supporting the use of prophylactic human papillomavirus (HPV) vaccines to influence the risk of recurrence of cervical intraepithelial neoplasia after surgical treatment.

Methods

A systematic literature search was performed for publications reporting risk of recurrence of cervical intraepithelial neoplasia after surgical treatment in patients receiving HPV vaccination (either in the prophylactic or adjuvant setting). Comprehensive searches of six electronic databases (MEDLINE, Embase, Web of Science, PubMed, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, and references of identified studies) from their inceptions were performed (English language only), and hand search reference lists were performed. Two independent reviewers applied inclusion and exclusion criteria to select manuscripts, with differences discussed and agreed by consensus. The literature search was performed using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Results were reported as mean differences or pooled odds ratios (OR) with 95% confidence intervals (95% CI).

Results

A total of 5744 citations were reviewed; 5 studies comprising 2912 patients were selected for the analysis. There were 1338 patients in the vaccinated group and 1574 in the placebo or unvaccinated group. The incidence of histologically confirmed cervical intraepithelial neoplasia 2+ was reduced in the vaccinated compared to the unvaccinated group (OR 0.34, 95% CI 0.21–0.54, p=< 0.00001). The number needed to treat to prevent one recurrence was 27. Both pre-treatment vaccination (OR 0.40, 95% CI 0.21–0.78, p=0.007, number needed to treat – 37) and adjuvant vaccination (OR 0.28, 95% CI 0.14–0.56, p=0.0003, number needed to treat – 30) reduced recurrence rates.

Conclusion

Prophylactic or adjuvant HPV vaccination reduces the risk of recurrent cervical intraepithelial neoplasia 2+. These data support further investigation of its role as an adjuvant to surgical treatment.

Integrating measures of viral prevalence and seroprevalence: a mechanistic modelling approach to explaining cohort patterns of human papillomavirus in women in the USA

Incidence of human papillomavirus (HPV) related cancers is increasing, generating substantial interest in understanding how trends in population prevalence of HPV infection are changing. However, there are no direct, population-scale measurements of HPV prevalence prior to 2003. Previous work using models to reconstruct historical trends have focused only on genital infection or seroprevalence (prevalence of antibodies) separately, and the results of these single-measure studies have been hard to reconcile. Here, we develop a mechanistic disease model fit jointly to cervicogential prevalence and seroprevalence in unvaccinated women in the USA using National Health and Nutrition Examination Survey data (2003-2010) and compare it to fits of statistical age-cohort models. We find that including a latent HPV state in our model significantly improves model fit and that antibody waning may be an important contributor to observed patterns of seroprevalence. Moreover, we find that the mechanistic model outperforms the statistical model and that the joint analysis prevents the inconsistencies that arise when estimating historical cohort trends in infection from genital prevalence and seroprevalence separately. Our analysis suggests that while there is substantial uncertainty associated with the estimation of historic HPV trends, there has likely been an increase in the force of infection for more recent birth cohorts. This article is part of the theme issue 'Silent cancer agents: multi-disciplinary modelling of human DNA oncoviruses'.

Peak neutralizing and cross-neutralizing antibody levels to human papillomavirus types 6/16/18/31/33/45/52/58 induced by bivalent and quadrivalent HPV vaccines

We performed an independent comparison of neutralizing and cross-neutralizing antibody (ab) levels seven months after initiation of three-dose, six-month vaccination schedules with the bivalent and quadrivalent human papillomavirus (HPV) vaccines in adolescent Finnish and Indian females, respectively. We used a semi-automated Pseudovirion-Based Neutralization Assay and observed significantly higher HPV16/18 peak ab-levels in bivalent as compared to quadrivalent vaccine recipients. Bivalent vaccine induced cross-neutralizing HPV31/33/45/52/58 antibodies significantly more frequently and to higher levels than the quadrivalent vaccine. The correlation of bivalent vaccine-induced HPV45 ab-levels with HPV16/18 ab-levels was stronger than that of corresponding quadrivalent vaccine-induced ab-levels, suggesting a qualitatively different cross-reactive response. Our findings on the comparison of the immunogenicity of two HPV vaccine tested in two different populations indicate that further head-to-head studies are warranted.

Efficacy and immunogenicity of a single dose of human papillomavirus vaccine compared to no vaccination or standard three and two-dose vaccination regimens: A systematic review of evidence from clinical trials

OBJECTIVES

This study aimed to systematically review the literature on the efficacy and immunogenicity of single-dose HPV vaccination compared to no vaccination or multi-dose schedules among vaccine trial participants.

METHODS

Medline, EMBASE, Global Health Database and Cochrane Central Register of Controlled Trials were searched for publications and conference abstracts (dated January 1999-August 2018) using MeSH and non-MeSH terms for human papillomavirus AND vaccines AND (immunogenicity OR efficacy/effectiveness) AND dosage. Search results were screened against pre-specified eligibility criteria. Data were extracted from included articles, and a narrative synthesis conducted on efficacy against HPV16/18 infection and humoral immunogenicity.

RESULTS

Seven of 6,523 unique records identified were included in the review. Six were nested observational studies of participants randomised to receive two or three doses in three large HPV vaccine trials, in which some participants did not complete their allocated schedules. One small pilot study prospectively allocated participants to receive one or no vaccine dose. Frequency of HPV16/18 infection was low (e.g. <1% for 12-month-persistent infection) in all vaccinated participants up to seven years post vaccination and did not significantly differ by number of doses (p > 0.05 in all cases). Frequency of infection was significantly lower in one-dose recipients compared to unvaccinated controls (p < 0.01 for all infection endpoints in each study). HPV16/18 seropositivity rates were high in all HPV vaccine recipients (100% in three of four studies reporting this endpoint), though antibody levels were lower with one compared to two or three doses.

CONCLUSIONS

This review supports the premise that one HPV vaccine dose may be as effective in preventing HPV infection as multi-dose schedules in healthy young women. However, it also highlights the paucity of available evidence from purpose-designed, prospectively-randomised trials. Results from ongoing clinical trials assessing the efficacy and immunogenicity of single-dose HPV vaccination compared to currently-recommended schedules are awaited.

Prophylactic Hepatitis E Vaccines: Antigenic Analysis and Serological Evaluation

Hepatitis E virus (HEV) infection causes sporadic outbreaks of acute hepatitis worldwide. HEV was previously considered to be restricted to resource-limited countries with poor sanitary conditions, but increasing evidence implies that HEV is also a public health problem in developed countries and regions. Fortunately, several vaccine candidates based on virus-like particles (VLPs) have progressed into the clinical development stage, and one of them has been approved in China. This review provides an overview of the current HEV vaccine pipeline and future development with the emphasis on defining the critical quality attributes for the well-characterized vaccines. The presence of clinically relevant epitopes on the VLP surface is critical for eliciting functional antibodies against HEV infection, which is the key to the mechanism of action of the prophylactic vaccines against viral infections. Therefore, the epitope-specific immunochemical assays based on monoclonal antibodies (mAbs) for HEV vaccine antigen are critical methods in the toolbox for epitope characterization and for in vitro potency assessment. Moreover, serological evaluation methods after immunization are also discussed as biomarkers for clinical performance. The vaccine efficacy surrogate assays are critical in the preclinical and clinical stages of VLP-based vaccine development.

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.

Updates on immunologic correlates of vaccine-induced protection

Correlates of protection (CoPs) are increasingly important in the development and licensure of vaccines. Although the study of CoPs was initially directed at identifying a single immune function that could explain vaccine efficacy, it has become increasingly clear that there are often multiple functions responsible for efficacy. This review is meant to supplement prior articles on the subject, illustrating both simple and complex CoPs.

Infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions. A review of the literature

Background

Human papillomavirus (HPV) infects and propagates in the cervical mucosal epithelium. Hence, in addition to assessing systemic immunity, the accurate measurement of cervical immunity is important to evaluate local immune responses to HPV infection and vaccination. This review discusses studies that investigated the presence of infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions (CVS).

Methods

We searched the two main health sciences databases, PubMed and the ISI Web of Science, from the earliest dates available to March 2019. From the eligible publications, information was extracted regarding: (i) study design, (ii) the reported HPV-specific antibody concentrations in CVS (and the associated serum levels, when provided), (iii) the CVS collection method, and (iv) the immunoassays used.

Results

The systematic search and selection process yielded 44 articles. The evidence of HPV-specific antibodies in CVS after natural infection (26/44) and HPV vaccination (18/44) is discussed. Many studies indicate that HPV-specific antibody detection in CVS is variable but feasible with a variety of collection methods and immunoassays. Most CVS samples were collected by cervicovaginal washing or wicks, and antibody presence was mostly determined by VLP-based ELISAs. The moderate to strong correlation between vaccine-induced antibody levels in serum and in CVS indicates that HPV vaccines generate antibodies that transudate through the cervical mucosal epithelium.

Conclusion

Although HPV-specific antibodies have lower titres in CVS than in serum samples, studies have shown that their detection in CVS is feasible. Nevertheless, the high variability of published observations and the lack of a strictly uniform, well-validated method for the collection, isolation and quantification of antibodies indicates a need for specific methods to improve and standardize the detection of HPV-specific antibodies in CVS.

Altered antigenicity and immunogenicity of human papillomavirus virus-like particles in the presence of thimerosal

Thimerosal has been widely used as a preservative in human vaccines for decades. Thimerosal, a thiol capping agent with ethyl mercury being the active degradant, could have impacts on the vaccine potency due to potential thiol modification. The effects on the antigenicity and immunogenicity of human papillomavirus (HPV) virus-like particles (VLPs) in the presence of thimerosal was studied. In general, reduced binding activity was observed between HPV antigens and monoclonal antibodies (mAbs) upon thimerosal treatment, accompanied by reduced protein conformational stability. The immunogenicity of a pentavalent vaccine formulation (HPV6, HPV11, HPV16, HPV18 and hepatitis E virus) with or without thimerosal was studied in mice. The functional antibody titres, as well as the binding titres, were determined, showing a substantial decrease for vaccine formulations containing thimerosal for HPV16/18. Similarly, epitope-specific competition assays using specific and functional mAbs as tracers also showed a significant reduction in immunogenicity for HPV16/18 in the presence of thimerosal. Structural alterations in the capsid protein for HPV18 were observed with cryo-electron microscopy and 3-dimensional reconstruction in the comparative structural analysis. The results should alert scientists in formulation development field on the choice for vaccine preservatives, in particular for thiol-containing antigens.