Optimization and validation of a multiplexed luminex assay to quantify antibodies to neutralizing epitopes on human papillomaviruses 6, 11, 16, and 18

Prevalence and risk factors for HPV seropositivity and anogenital DNA positivity among men who have sex with men: a repeated cross-sectional study

OBJECTIVES

This study aimed to assess associations of potential risk factors with human papillomavirus (HPV) seropositivity among men who have sex with men (MSM) and compare these to risk factors for anal and penile (HPV) deoxyribonucleic acid (DNA)-positivity in the same study population.

METHODS

Seropositivity and anal and penile HPV DNA-positivity were determined for seven high-risk HPV genotypes for MSM aged 16-24 years participating in Papillomavirus Surveillance among STI clinic Youngsters in the Netherlands (PASSYON) 2009-2021. Logistic regression models were conducted to assess risk factors for seropositivity, anal and penile HPV DNA-positivity.

RESULTS

Overall, 1019 MSM were included. HPV-16 and -18 were most common for serology, and anal and penile HPV DNA-positivity. Although no clear similarities were observed for most risk factors for HPV seropositivity and anal or penile DNA positivity, receptive anal intercourse (RAI) was the strongest associated risk factor for both seropositivity ('RAI ever' adjusted odds ratio [aOR] 3.50, 95% confidence interval [CI] 1.56-7.88; 'RAI previous 6 months' aOR 2.17, 95% CI 1.44-3.26) and anal DNA-positivity ('RAI previous 6 months' aOR 1.67, 95% CI 1.09-2.56).

CONCLUSIONS

Our study is suggestive of site-specific immune response after HPV infection; RAI might lead to anal HPV infections and consequently to seroconversion. Finally, as the two genotypes that are most oncogenic and preventable by all HPV vaccines were most common, our results underline the importance of gender-neutral vaccination.

Validation of Luminex immunological and competitive Luminex immunological assays for clinical immunogenicity assessment of a 14-valent recombinant human papillomavirus vaccine

A novel virus-like particle (VLP)-based multivalent recombinant human papillomavirus (HPV) vaccine was developed and evaluated in human, including 14 HPV-type specific VLP antigens (HPV6, 11, 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, and 59). The pseudovirus-based neutralizing assay (PBNA) method is widely used for immunogenicity assessment of HPV vaccine in clinical trials. However, as many as 14 antigen-specific antibody levels need be determined, PBNA is, for many reasons, challenging and time-consuming. In this study, we developed a Luminex immunological assay (LIA) and a competitive Luminex immunological assay (cLIA). These methods increase the throughput, reproducibility and precision, as well as reduce the complexity. All assay parameters showed good characteristics in the validation of both methods, benefiting from highly purified and structurally correct VLPs, high specific antibodies, standard VLP-microspheres and PE-mAbs conjugating process, adequate assay development and stable system. Validation data support the use of both methods for immunogenicity assessment in clinical trials. LIA showed higher sensitivity than cLIA, and due to limited epitopes of mAb, cLIA detected lower antibody responses, and therefore, fewer antibodies. This work not only supports clinical trials of 14-valent HPV vaccines more efficiently and reliably, but also provides a set of validation strategies and usable standards for general vaccine immunogenicity testing.

RDE Treatment Prevents Non-Specific Detection of SARS-CoV-2- and Influenza-Specific IgG Antibodies in Heat-Inactivated Serum Samples

Assessing the levels of serum IgG antibodies is widely used to measure immunity to influenza and the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after natural infection or vaccination with specific vaccines, as well as to study immune responses to these viruses in animal models. For safety reasons, sometimes serum specimens collected from infected individuals are subjected to heat inactivation at 56 °C to reduce the risk of infecting personnel during serological studies. However, this procedure may affect the level of virus-specific antibodies, making the results of antibody immunoassays uninterpretable. Here, we evaluated the effect of the heat inactivation of human, ferret and hamster serum samples on the binding of IgG antibodies to the influenza and SARS-CoV-2 antigens. For this, serum samples of naive and immune hosts were analyzed in three variants: (i) untreated sera, (ii) heated at 56 °C for 1 h, and (iii) treated with receptor-destroying enzyme (RDE). The samples were studied through an in-house enzyme-linked immunosorbent assay (ELISA) using whole influenza virus or recombinant proteins corresponding to nucleocapsid (N) protein and the receptor-binding domain of SARS-CoV-2 Spike (RBD) as antigens. We demonstrated that the heat inactivation of the naive serum samples of various hosts can lead to false-positive results, while RDE treatment abolished the effect of the non-specific binding of IgG antibodies to the viral antigens. Furthermore, RDE also significantly decreased the level of virus-specific IgG antibodies in SARS-CoV-2 and influenza-immune sera of humans and animals, although it is unknown whether it actually removes true virus-specific IgG antibodies or only non-specifically binding artifacts. Nevertheless, we suggest that the RDE treatment of human and animal sera may be useful in preventing false-positive results in various immunoassays, while also neutralizing infectious virus, since the standard protocol for the use of RDE also includes heating the sample at 56 °C.

Development and Validation of Two Optimized Multiplexed Serologic Assays for the 9-Valent Human Papillomavirus Vaccine Types

Two multiplex immunoassays are routinely used to assess antibody responses in clinical trials of the 9-valent human papillomavirus (9vHPV) vaccine. The HPV6/11/16/18/31/33/45/52/58 competitive Luminex immunoassay (HPV-9 cLIA) and HPV6/11/16/18/31/33/45/52/58 total immunoglobulin G Luminex immunoassay are used for measurements of immunogenicity. Following their initial validation in 2010, both assays were redeveloped, and several parameters were optimized, including the coating concentration of virus-like particles, type of Luminex microspheres, serum sample and reference standard diluent, reference standard starting dilution and titration series, and vendor and concentration of the phycoerythrin-labeled antibodies. Validation studies evaluated the assay performance parameters, including the intra-assay precision (repeatability), intermediate precision, linearity, relative accuracy, and limits of quantitation. In addition, since maintaining a link to the original assays that were used in trials supporting vaccine licensure is critical, the assays were formally bridged to the previous assay versions by using individual patient sera from a 9vHPV vaccine clinical trial (n = 150 day 1 [prevaccination] samples; n = 100 month 7 [1 month post-last vaccine dose] and n = 100 month 36 [30 months post-last vaccine dose; antibody persistence] samples). The results of the validation studies indicate that both optimized assays are accurate, specific, and precise over their respective quantifiable ranges. There was a strong linear association between the new and previous versions of both assays. Assay serostatus cutoffs for the redeveloped assays were established based on the bridging studies and, for the HPV-9 cLIA, further refined, based on additional data from HPV vaccine clinical studies so as to align the seropositivity rates between assay versions. IMPORTANCE Assay modernization is a key aspect of vaccine life cycle management. Thus, new, reoptimized versions of two 9vHPV immunoassays have been developed and validated for use in ongoing and future HPV vaccine clinical trials. These assays are suitable for use in high-throughput testing for HPV antibodies in serum samples. Bridging to previous versions of the assays allows for the continuous monitoring of immune responses across assay versions, including in immunogenicity studies that involve new populations as well as long-term follow-up studies.

Immunogenicity and safety of quadrivalent and 9-valent human papillomavirus vaccines in Indian clinical trial participants

The quadrivalent human papillomavirus (qHPV; HPV6/11/16/18) and 9-valent HPV (9vHPV; HPV6/11/16/18/31/33/45/52/58) vaccines have demonstrated efficacy, immunogenicity, and safety in international clinical trials. We report outcomes from three completed clinical trials in India: a single-arm study (V501-029 [NCT00380367]) in Indian girls (aged 9-15 years; N = 110) evaluating qHPV vaccine immunogenicity and safety; a subgroup analysis (n = 225) of Indian girls/boys (9-15 years) and women (16-26 years) from a global study (V503-002 [NCT00943722]) evaluating 9vHPV vaccine immunogenicity and safety; and a qHPV vaccine post-marketing safety surveillance study (V501-125) in Indian females (aged 9-45 years; N = 188) vaccinated during routine care. In V501-029 and V503-002, HPV vaccines were administered as 3 doses (Day 1, Month 2, Month 6). Serum HPV antibodies were evaluated by competitive Luminex immunoassays at Day 1 and Month 7 (both studies) and Months 12, 24, and 36 (V503-002 only). Adverse events (AEs) were collected by Vaccination Report Card. In V501-125, participants were actively surveilled for serious AEs (SAEs) within 30 days post-qHPV vaccination. In per-protocol analyses, qHPV and 9vHPV vaccines induced robust anti-HPV6/11/16/18 (V501-029) and HPV6/11/16/18/31/33/45/52/58 (V503-002) responses, respectively; ≥97% of participants seroconverted at Month 7 for each vaccine HPV type in both studies, and antibody responses persisted through 36 months in V503-002. The most common AEs were injection-site-associated. Most AEs were mild/moderate; no deaths, vaccine-related SAEs, or discontinuations due to AEs were reported. In V501-125, no SAE was reported. Overall, the qHPV and 9vHPV vaccines elicited robust antibody responses and were generally well tolerated in Indian participants.

Effectiveness, immunogenicity, and safety of the quadrivalent HPV vaccine in women and men aged 27–45 years

Among women aged 27–45 years, the quadrivalent human papillomavirus (qHPV; HPV6/11/16/18) vaccine was generally well tolerated, efficacious, and immunogenic in the placebo-controlled FUTURE III study (NCT00090220; n = 3253). The qHPV vaccine was also generally well tolerated and highly immunogenic in men aged 27–45 years who participated in the single-cohort mid-adult male (MAM) study (NCT01432574; n = 150). Here, we report results of a long-term follow up (LTFU) extension of FUTURE III with up to 10 years follow-up. To understand the relevance of the mid-adult women LTFU study in the context of mid-adult men vaccination, we report results from post-hoc, cross-study immunogenicity analyses conducted to compare immunogenicity (geometric mean titers; GMTs) at 1-month post-qHPV vaccine dose 3 in women and men aged 27–45 years versus women and men aged 16–26 years from prior efficacy studies. The qHPV vaccine demonstrated durable protection against the combined endpoint of HPV6/11/16/18-related high-grade cervical dysplasia and genital warts up to 10 years (median 8.9) post-dose 3 and sustained HPV6/11/16/18 antibody responses through approximately 10 years in women aged 27–45 years. Efficacy of qHPV vaccine in men aged 27–45 years was inferred based on the cross-study analysis of qHPV vaccine immunogenicity demonstrating non-inferior HPV6/11/16/18 antibody responses in men aged 27–45 years versus 16–26 years. In conclusion, durable effectiveness of the qHPV vaccine was demonstrated in women 27–45 years of age, and vaccine efficacy was inferred in men 27–45 years of age based on the serological results.

Contribution of Surface-Exposed Loops on the HPV16 Capsid to Antigenic Domains Recognized by Vaccine or Natural Infection Induced Neutralizing Antibodies

Human papillomavirus (HPV) is the causative agent of cervical and other cancers and represents a significant global health burden. HPV vaccines demonstrate excellent efficacy in clinical trials and effectiveness in national immunization programmes against the most prevalent genotype, HPV16. It is unclear whether the greater protection conferred by vaccine-induced antibodies, compared to natural infection antibodies, is due to differences in antibody magnitude and/or specificity. We explore the contribution of the surface-exposed loops of the major capsid protein to antigenic domains recognized by vaccine and natural infection neutralizing antibodies. Chimeric pseudoviruses incorporating individual (BC, DE, EF, FG, HI) or combined (All: BC/DE/EF/FG/HI) loop swaps between the target (HPV16) and control (HPV35) genotypes were generated, purified by ultracentrifugation and characterized by SDS-PAGE and electron microscopy. Neutralizing antibody data were subjected to hierarchical clustering and outcomes modeled on the HPV16 capsomer crystal model. Vaccine antibodies exhibited an FG loop preference followed by the EF and HI loops while natural infection antibodies displayed a more diverse pattern, most frequently against the EF loop followed by BC and FG. Both vaccine and natural infection antibodies demonstrated a clear requirement for multiple loops. Crystal modeling of these neutralizing antibody patterns suggested natural infection antibodies typically target the outer rim of the capsomer while vaccine antibodies target the central ring around the capsomer lumen. Chimeric pseudoviruses are useful tools for probing vaccine and natural infection antibody specificity. These data add to the evidence base for the effectiveness of an important public health intervention. IMPORTANCE The human papillomavirus type 16 (HPV16) major virus coat (capsid) protein is a target for antibodies induced by both natural infection and vaccination. Vaccine-induced immunity is highly protective against HPV16-related infection and disease while natural infection associated immunity significantly less so. For this study, we created chimeric functional pseudoviruses based upon an antigenically distant HPV genotype (HPV35) resistant to HPV16-specific antibodies with inserted capsid surface fragments (external loops) from HPV16. By using these chimeric pseudoviruses in functional neutralization assays we were able to highlight specific and distinct areas on the capsid surface recognized by both natural infection and vaccine induced antibodies. These data improve our understanding of the difference between natural infection and vaccine induced HPV16-specific immunity.

Development of functionally relevant potency assays for monovalent and multivalent vaccines delivered by evolving technologies

A potency or potency-indicating assay is a regulatory requirement for the release of every lot of a vaccine. Potency is a critical quality attribute that is also monitored as a stability indicator of a vaccine product. In essence, a potency measurement is a test of the functional integrity of the antigen and is intended to ensure that the antigen retains immunocompetence, i.e., the ability to stimulate the desired immune response, in its final formulation. Despite its central importance, there is incomplete clarity about the definition and expectation of a potency assay. This article provides a perspective on the purpose, value, and challenges associated with potency testing for vaccines produced by new technologies. The focus is on messenger RNA vaccines in the light of experience gained with recombinant protein-based vaccines, which offer the opportunity to directly correlate in vitro antigenicity with in vivo immunogenicity. The challenges with developing immunologically relevant in vitro assays are discussed especially for multivalent vaccine products, the importance of which has been reinforced by the ongoing emergence of SARS-CoV-2 variants of concern. Immunoassay-based release of multivalent vaccine products, such as those containing multiple antigens from different variants or serotypes of the same virus, require antibodies that are selective for each antigen and do not significantly cross-react with the others. In the absence of such exclusively specific antibodies, alternative functional assays with demonstrable correlation to immunogenicity may be acceptable. Initiatives for geographically distributed vaccine technology facilities should include establishing these assay capabilities to enable rapid delivery of vaccines globally.

Development of HPV58 type-specific antibodies and detection kit

Currently, human papillomavirus (HPV) vaccines are in short supply, so the development of HPV vaccines has a broad market prospect. The 3-, 9-, and 15-valent HPV vaccines developed by ourselves all contain HPV58-derived antigen components. It is important to detect HPV 58 during vaccine production. Here, we introduced a development process of HPV58 type-specific antibodies and a detection kit. Briefly, HPV58 L1-Virus Like Particles (VLPs) were used as antigens to immunize mice, followed by extraction of the ascites to prepare hybridoma cells. After culturing, the supernatants containing secreted antibodies were harvested, purified, and screened to obtain monoclonal antibodies (mAbs). In the pool of attained monoclonal antibodies, we selected 2F7 and 2G7 to evaluate their subtypes, specificity, neutralizing activity, serum competition, binding affinity and gene sequencing. Finally, an enzyme-linked immunosorbent assay (ELISA) detection kit was assembled with 2F7 and 2G7 mAbs which possessed high specificity to HPV58 L1-VLPs. The detection kit developed by 2F7 and 2G7 could be adopted to specifically detect HPV58 L1 protein with good linearity and detection range, which could be widely used in clinical testing and quality control in the production of HPV vaccines.Abbreviations: BSA: Bovine serum albumin; CDRs: Complementarity-determining regions; CV: Coefficient of variation; DTT: Dithiothreitol; ELISA: Enzyme-linked immunosorbent assay; HAT: Hypoxanthine-aminopterin-thymidine; HPV: Human Papillomavirus; IC₅₀: 50% inhibition rate; IC₉₀: 90% inhibition rate; mAbs: Monoclonal antibodies; VLP: Virus-like particle.

Development and evaluation of a new non-competitive Luminex immunoassay detecting antibodies against human papillomavirus types 6, 11, 16 and 18

Serum antibody levels can be used to measure the humoral immune response against human papillomaviruses (HPV). We developed and validated a rapid, technically simple and relatively inexpensive multiplex non-competitive Luminex-based immunoassay (ncLIA) to measure total IgG antibody levels against four HPV types. For the assay's solid phase, virus-like particles (VLPs) of HPV6, 11, 16 and 18 were bound to heparin-coated beads. HPV serum antibody levels binding to the VLPs were quantified using a phycoerithrin-conjugated secondary polyclonal donkey anti-human IgG antibody. Standardization and validation of the ncLIA were performed using 96 paired serum and genital samples from participants in the HITCH cohort study, including young women (aged 18-24 years) and their male sexual partners (aged 18+) in Montreal, Canada. Results from the ncLIA were compared to a validated Luminex immunoassay from PPD laboratories using Pearson's correlation coefficients, receiver operating characteristic curves and logistic regression. Our assay had good inter- and intra-assay variability. The correlation of serum antibody levels between the ncLIA and validation assay was highest for HPV16 and HPV11 (r=0.90), followed by HPV6 (r=0.86) and HPV18 (r=0.67). The ncLIA was better able to predict HPV DNA positivity in genital samples than the validation assay for HPV16 [area under the curve (AUC) 0.65 versus 0.52, P=0.001] and HPV18 [AUC 0.71 versus 0.57, P=0.024]. AUCs for HPV6 and HPV11 were similar between the two assays (0.70 versus 0.71, P=0.59, and 0.88 versus 0.96, P=0.08, respectively). The developed ncLIA is useful for measuring total IgG antibody response following natural infection or vaccination against four HPV VLPs included in the quadrivalent vaccine.

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.

Comprehensive Assessment of the Antigenic Impact of Human Papillomavirus Lineage Variation on Recognition by Neutralizing Monoclonal Antibodies Raised against Lineage A Major Capsid Proteins of Vaccine-Related Genotypes

Human papillomavirus (HPV) is the causative agent of cervical and other epithelial cancers. Naturally occurring variants of HPV have been classified into lineages and sublineages based on their whole-genome sequences, but little is known about the impact of this diversity on the structure and function of viral gene products. The HPV capsid is an icosahedral lattice comprising 72 pentamers of the major capsid protein (L1) and the associated minor capsid protein (L2). We investigated the potential impact of this genome variation on the capsid antigenicity of lineage and sublineage variants of seven vaccine-relevant, oncogenic HPV genotypes by using a large panel of monoclonal antibodies (MAbs) raised against the L1 proteins of lineage A antigens. Each genotype had at least one variant that displayed a ≥4-fold reduced neutralizing antibody sensitivity against at least one MAb, demonstrating that naturally occurring variation can affect one or more functional antigenic determinants on the HPV capsid. For HPV16, HPV18, HPV31, and HPV45, the overall impact was of a low magnitude. For HPV33 (sublineages A2 and A3 and lineages B and C), HPV52 (lineage D), and HPV58 (lineage C), however, variant residues in the indicated lineages and sublineages reduced their sensitivity to neutralization by all MAbs by up to 1,000-fold, suggesting the presence of key antigenic determinants on the surface of these capsids. These determinants were resolved further by site-directed mutagenesis. These data improve our understanding of the impact of naturally occurring variation on the antigenicity of the HPV capsid of vaccine-relevant oncogenic HPV genotypes.IMPORTANCE Human papillomavirus (HPV) is the causative agent of cervical and some other epithelial cancers. HPV vaccines generate functional (neutralizing) antibodies that target the virus particles (or capsids) of the most common HPV cancer-causing genotypes. Each genotype comprises variant forms that have arisen over millennia and which include changes within the capsid proteins. In this study, we explored the potential for these naturally occurring variant capsids to impact recognition by neutralizing monoclonal antibodies. All genotypes included at least one variant form that exhibited reduced recognition by at least one antibody, with some genotypes affected more than others. These data highlight the impact of naturally occurring variation on the structure of the HPV capsid proteins of vaccine-relevant oncogenic HPV genotypes.

Human Papillomavirus Antibody Levels and Quadrivalent Vaccine Clinical Effectiveness in Perinatally Human Immunodeficiency Virus-infected and Exposed, Uninfected Youth

BACKGROUND

Persons who are infected with human immunodeficiency virus (HIV) are at high risk of human papillomavirus (HPV)-associated cancers. The objectives are to compare antibody titers to HPV 6, 11, 16, and 18 and rate of abnormal cytology between perinatally HIV-infected (PHIV) and perinatally HIV-exposed, uninfected (PHEU) youth.

METHODS

This is a prospective observational cohort study of HPV4 vaccinated youth performed as part of the multicenter Pediatric HIV/AIDS Cohort Study Adolescent Master Protocol. Seroconversion and geometric mean titer (GMT) against HPV types 6, 11, 16, and 18 were calculated. Vaccine effectiveness included rates of abnormal cervical cytology and genital warts.

RESULTS

Seroconversion to HPV 6, 11, 16, and 18 occurred in 83%, 84%, 90%, and 62% of 310 vaccinated PHIV youth compared to 94%, 96%, 99%, and 87% of 148 vaccinated PHEU youth, respectively (P < .05 for all comparisons). GMTs were lower in the PHIV vs PHEU within each category of HPV4 doses received. Higher GMTs were associated with younger age, lower HIV type 1 RNA viral load, and higher CD4% at first HPV4 vaccination, as well as shorter duration between last vaccine dose and antibody specimen. Abnormal cytology occurred in 33 of 56 PHIV and 1 of 7 PHEU sexually active vaccinated females, yielding incidence rates per 100 person-years of 15.0 (10.9 to 20.6) and 2.9 (0.4 to 22.3), respectively.

CONCLUSION

Antibody titers to HPV4 were lower for all serotypes in PHIV compared to PHEU youth. Protection against abnormal cytology was also diminished in sexually active PHIV females.

Seroprevalence of Human Papillomavirus 6/11/16/18 Among Self-identified Gay/Bisexual Men Who Have Sex With Men, Men Who Have Sex With Women, and Females, United States, 2003-2010

BACKGROUND

Differences in human papillomavirus (HPV) seroprevalence by sex have been observed, likely due to differences in the anatomic site of HPV exposure. Seroconversion may be more likely after exposure at nonkeratinized (mucosal) compared to keratinized epithelium. We compared seroprevalence among self-identified gay/bisexual men who have sex with men (MSM) and females, 2 groups more likely exposed at mucosal epithelium, and men who only have sex with women (MSW), a group likely exposed primarily at keratinized epithelium, using data from the National Health and Nutrition Examination Survey from 2003 to 2010.

METHODS

HPV 6/11/16/18 serum antibody was detected using a multiplexed, competitive luminex immunoassay. Weighted seroprevalence was estimated among unvaccinated, sexually experienced 18-59 year-old MSM, MSW, and females, overall and by demographic and sexual behavior characteristics. Seroprevalences were compared using prevalence ratios adjusted for sexual behavior (aPRs).

RESULTS

Overall, seroprevalence in MSM, MSW, and females was 42.6%, 13.2%, and 37.1%, respectively. Seroprevalence in MSM was comparable to females (aPR: 0.85, 95% confidence interval [CI]: 0.68-1.08) and higher than MSW (aPR: 2.72, 95% CI: 2.19-3.38). MSW had a significantly lower seroprevalence than females (aPR: 0.31, 95% CI: 0.28-0.34). Similar associations were seen in all sociodemographic subgroups. Seroprevalence increased with number of lifetime sex partners in all groups.

CONCLUSIONS

In this population-based survey, HPV seroprevalence among groups likely exposed at mucosal epithelium (MSM, females) was comparable; seroprevalence in both groups was higher than in MSW. Future research could explore whether differences in seropositivity following infection result in differential protection from future infection.

Transmission reduction and prevention with HPV vaccination (TRAP-HPV) study protocol: a randomised controlled trial of the efficacy of HPV vaccination in preventing transmission of HPV infection in heterosexual couples

INTRODUCTION

Human papillomavirus (HPV) is a causal agent of malignancies including cervical, vulvar, vaginal, penile, anal and oropharyngeal cancer, as well as benign conditions such as anogenital warts. HPV vaccination protects individuals against infections with the target HPV types and their clinical outcomes. However, little is known about the protection an immunised individual confers to their sexual partner or its impact on HPV transmission dynamics. In this context, the Transmission Reduction and Prevention with HPV vaccination (TRAP-HPV) study was designed to determine the efficacy of an HPV vaccine in reducing transmission of genital and oral HPV infection in sexual partners of vaccinated individuals.

METHODS AND ANALYSIS

The TRAP-HPV study is an ongoing randomised controlled trial among heterosexual couples living in Montreal, Canada. Sexually active couples, aged between 18 and 45 years, who have been in a relationship no longer than 6 months are considered eligible. Participants are independently randomised to receive either the intervention HPV vaccine, Gardasil 9, or a placebo hepatitis A vaccine, Avaxim, creating four vaccination groups among couples: intervention-intervention, intervention-placebo, placebo-intervention and the placebo-placebo. Participants provide genital (vaginal/penile) and oral samples at baseline and five follow-up visits over a 1-year duration. Linear Array HPV genotyping is used to detect 36 HPV types. Cox proportional hazard regression models will be used to estimate the effect of vaccination on HPV transmission.

ETHICS AND DISSEMINATION

The TRAP-HPV study received ethical approval by institutional review boards McGill University, Concordia University and Centre Hospitalier de l'Université de Montréal. Before enrolment, all participants provide informed written consent. Results will be published in peer-reviewed journals and presented at national and international conferences. The generated empirical evidence could be used in mathematical models of vaccination to inform policymakers in Canada and elsewhere.

TRIAL REGISTRATION NUMBER

NCT01824537.

Impact of heat-inactivation on the detection of SARS-CoV-2 IgM and IgG antibody by ELISA

BACKGROUND

To establish a safe and accurate method for detecting SARS-CoV-2 IgM and IgG, we assessed the impact of sera after heat-inactivation on the SARS-CoV-2 IgM and IgG levels measured by ELISA-immunoassay.

METHODS

The serum samples of 62 patients with COVID-19 and 18 healthy controls were collected in Hankou's Hospital of Wuhan from February 27 to March 6, 2020. Before and after the samples were inactivated, the levels of IgM and IgG antibodies were measured.

RESULTS

The indexes of antibodies after inactivated were significantly higher than those in fresh sera, while the positive rates in all participants or in patients with COVID-19 did not change. The positive coincidence rate, negative coincidence rate and total coincidence rate of IgM antibodies before and after inactivation were 100.00% (55/55), 96.00% (24/25) and 98.75% (79/80), respectively (κ = 0.971, P < 0.001), while those for IgG antibodies were 98.21% (55/56), 91.67% (22/24) and 98.75% (79/80) respectively (κ = 0.910, P < 0.001). These results showed a good consistency.

CONCLUSIONS

Heating-activation does not decrease the diagnostic efficacy of SARS-CoV-2 IgM or IgG antibodies. Sera inactivated by heating at 56 °C for 30 min should be recommended to minimize the risk of virus contamination of laboratory staff.

Final analysis of a 14-year long-term follow-up study of the effectiveness and immunogenicity of the quadrivalent human papillomavirus vaccine in women from four nordic countries

BACKGROUND

The quadrivalent human papillomavirus (qHPV) vaccine prevented vaccine HPV type-related infection and disease in young women in the 4-year FUTURE II efficacy study (NCT00092534). We report long-term effectiveness and immunogenicity at the end of 14 years of follow-up after enrollment in FUTURE II.

METHODS

Young women (16-23 years of age) from Denmark, Iceland, Norway, and Sweden who received three qHPV vaccine doses during the randomized, double-blind, placebo-controlled FUTURE II base study were followed for effectiveness for an additional ≥10 years through national registries. Tissue samples including but not limited to those collected during organized cervical cancer screening programs were obtained from regional biobanks to be adjudicated for histopathology diagnosis and tested for HPV DNA. The observed incidence of HPV16/18-related high-grade cervical dysplasia (primary outcome) was compared with recent historical background incidence rates in an unvaccinated population. Serum was collected at years 9 and 14 to assess antibody responses.

FINDINGS

No cases of HPV16/18-related high-grade cervical dysplasia were observed in the per-protocol effectiveness population (N = 2121; 24,099·0 person-years of follow-up) during the entire study. Vaccine effectiveness of 100% (95% CI 94·7-100) was demonstrated for ≥12 years, with a trend toward continued protection through 14 years post-vaccination. Seropositivity rates at study conclusion were >90% (HPV6/11/16) and 52% (HPV18) using competitive Luminex immunoassay, and >90% (all four HPV types) using the more sensitive IgG Luminex immunoassay.

INTERPRETATION

Vaccination of young women with qHPV vaccine offers durable protection against HPV16/18-related high-grade cervical dysplasia for ≥12 years, with a trend toward continued protection through 14 years post-vaccination, and induces sustained HPV6/11/16/18 antibody responses for up to 14 years post-vaccination. There was no evidence of waning immunity, suggesting no need for a booster dose during that period.

FUNDING

Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.

In RRP, serologic response to HPV is frequently absent and slow to develop

Background

Recurrent respiratory papillomatosis (RRP) is characterized by repeated formation of papillomas in the respiratory tract and is caused by human papillomavirus (HPV) types 6 and 11. Women with genital HPV infection are slow to develop weak humoral immunity, but respond robustly to the HPV vaccine. We wondered if people with RRP had a similar immune response.

Methods

A convenience cross-sectional sample of patients with RRP were recruited into one of four groups: 1) adults and adolescents with active RRP, 2) children with active RRP, 3) RRP patients who had undergone HPV vaccination prior to enrollment and, 4) people with RRP who were in remission. Anti-HPV6 and HPV11 serology was determined by cLIA on a single blood draw.

Results

Of the 70 subjects enrolled, 36, 16, 8, and 10, were in groups 1, 2, 3, and 4, respectively. 47% of participants aged >11 years and 81% aged ≤11 years possessed no antibodies against HPV6 or HPV11 (ie. double seronegative). 61% of patients in remission were double seronegative. All participants who had received HPV vaccine previously were seropositive to at least one of these low risk HPV types (ie none of them were double seronegative). Among patients who had active RRP and never had HPV vaccination (n = 52) there was an association between duration of symptoms and seropositivity. Of those who were seropositive, the geometric mean duration of symptoms was 11 years compared to 4.7 years for those who were seronegative (p = 0.001).

Conclusion

People with RRP are capable of developing a humoral response to HPV6 and HPV11. That response appears to be robust when initiated by the HPV vaccine, but either nonexistent or slow to develop in response to infection. Most in remission do not have demonstrable antibody levels against HPV6 or HPV11.

Impact of quadrivalent HPV vaccine dose spacing on immunologic response in women living with HIV

HPV vaccination schedules have changed as evidence has supported reduced dosing and extended intervals. Women living with HIV (WLWH) represent an important population with no data on alternative dosing. Girls and WLWH received quadrivalent HPV (qHPV) vaccine in a pan-Canadian study of immunogenicity and efficacy. Serology was performed at months 0/2/7/12/18/24. Medical and sexual history was collected throughout. Linear regression was used to determine if spacing of doses was associated with peak antibody titer. Multivariable analyses demonstrated significant relationships between peak antibody titer and time to blood draw post last vaccine dose, naivety to the relevant HPV type, and HIV viral load for all qHPV types. There was a significant relationship between peak HPV16/18 antibody titer and age. Taking age, time to serology, CD4 cell count, CD4 nadir, HIV viral load, and HPV naivety into account, spacing of the three qHPV vaccine doses did not significantly impact peak antibody titers.

Trypanosoma cruzi Virulence Factors for the Diagnosis of Chagas' Disease

trans-Sialidase and cruzipain are important virulence factors from Trypanosoma cruzi, the etiological agent of Chagas disease, that have highly antigenic domains in their structure and were reported as potential tools for diagnosis of the illness. The aim of the present study is to assess the possibility of using cruzipain and the catalytic domain of trans-sialidase in a Surface Plasmon Resonance-based immunosensor for the diagnosis of chronic Chagas disease. Immunoassays carried out with canine sera verified that cruzipain allows the detection of anti-Trypanosoma cruzi antibodies whereas recombinant trans-sialidase did not yield specific detections, due to the high dilutions of serum used in the immunoassays that hinder the possibility to sense the specific low titer antibodies. The developed cruzipain-based biosensor, whose price per assay is comparable to a commercial enzyme-linked immunosorbent assay (ELISA), was successfully applied for the rapid quantification of specific antibodies against Trypanosoma cruzi in fresh human sera showing an excellent agreement with ELISA.

Is there evidence for efficacy of human papillomavirus vaccination in solid organ transplant recipients?

Human papillomavirus (HPV) infection is one of the most common sexually transmitted infections worldwide and is associated with precancerous lesions and cancers of the cervix, vulva, vagina, penis, anus, tonsils and base of the tongue. Several studies show an increased risk of HPV-associated cancers in solid organ transplant recipients (SOTR). The aims of this review are to investigate the evidence of efficacy for the HPV vaccination in transplant recipients and to discuss the known national guidelines. A systematic literature search has been conducted to identify studies where SOTR received the HPV vaccination to evaluate the efficacy of the HPV vaccine on this population. The primary outcome was antibody response against the HPV genotypes included in the vaccines and the secondary outcome was national guidelines recommending HPV vaccination of SOTR. Three cohort studies evaluated immunogenicity. Two studies found suboptimal effect of the HPV vaccine, while an early terminated study detected 100% seropositivity. We have identified four national guidelines in the following countries; United States of America, Canada, Australia and Ireland, along with a recommendation from the World Health Organization (WHO).

The results from the three studies were inconclusive due to the small sample sizes and the diverging results. Recommendations of HPV vaccination of SOTR is based on the knowledge about safety and efficiency in the general population and the safety of other inactivated (not live) vaccines in SOTR. Theoretically, the nonavalent vaccine should be recommended as the first choice in SOTR without age- or sex restrictions.

A Randomized, Placebo-Controlled Trial of the Quadrivalent Human Papillomavirus Vaccine in Human Immunodeficiency Virus-Infected Adults Aged 27 Years or Older: AIDS Clinical Trials Group Protocol A5298

Background

Adults living with human immunodeficiency virus (HIV) are at increased risk for anal and oropharyngeal cancer caused by human papillomavirus (HPV). The efficacy of HPV vaccines in this population is unknown.

Methods

In this phase 3, double-blind, randomized, controlled trial, we assigned HIV-infected adults aged ≥27 years to the quadrivalent HPV (types 6, 11, 16, 18) vaccine or placebo (1:1) stratified by sex and presence of anal high-grade squamous intraepithelial lesions on biopsy (bHSIL). The primary endpoint was vaccine efficacy against incident persistent anal infection with quadrivalent vaccine types or single detection at the final visit that were not present at baseline. Secondary endpoints included vaccine efficacy for anal bHSIL after week 52, persistent oral HPV infection.

Results

A total of 575 participants were randomized. The Data and Safety Monitoring Board stopped the study early due to futility. Vaccine efficacy was 22% (95.1% confidence interval [CI], -31%, 53%) for prevention of persistent anal infection or single detection at the final visit, 0% (95% CI -44%, 31%) for improving bHSIL outcomes and 88% (95.1% CI 2%, 98%) for preventing persistent oral HPV infection, but was 32% (95.1% CI -80%, 74%) for 6-month persistent oral HPV infection or single detection at the final visit.

Conclusions

These results do not support HPV vaccination of HIV-infected adults aged ≥27 years to prevent new anal HPV infections or to improve anal HSIL outcomes. However, our data suggest a role for prevention of oral HPV infections, but this finding should be confirmed in future studies.

Clinical Trials Registration

NCT01461096.

Immunogenicity of a Quadrivalent Human Papillomavirus Vaccine When Co-Administered with Tetanus-Reduced Diphtheria-Acellular Pertussis and Quadrivalent Meningococcal Conjugate Vaccines in Healthy Adolescents: Results from a Randomized, Observer-Blind, Controlled Trial

Introduction

Vaccines against human papillomavirus (HPV), tetanus, diphtheria, pertussis (Tdap) and Neisseria meningitidis are widely recommended in adolescents. A phase-4 observer-blind study was performed to investigate the impact of concomitant administration of a quadrivalent HPV (HPV4) and Tdap vaccine with a quadrivalent meningococcal CRM₁₉₇-conjugate vaccine (MenACWY-CRM) in terms of immunogenicity against the different vaccine antigens and overall safety profile. Previous results showed that concomitant administration of the three vaccines did not impact the immunogenicity of Tdap and MenACWY, or safety. This article presents recently released HPV immunogenicity results.

Methods

Healthy adolescents aged 11–18 years (801) were randomized to receive either HPV4 + Tdap + MenACWY or HPV4 + Tdap + Placebo and two additional doses of HPV4 at 2 and 6 months after the first dose. Antibody responses to HPV types (HPV-6, -11, -16 and -18) were assessed at baseline and at 1 month post-full vaccination.

Results

Post-third HPV4 dose, non-inferiority of immune responses to HPV4 + Tdap + MenACWY vs. HPV4 + Tdap + Placebo was demonstrated; the lower limits of two-sided 95% CIs of the between-group differences in seroconversion rates were > − 5% (non-inferiority margin) against each HPV type tested. Seroconversion rates ranged between 98.0% (HPV-6) and 99.7% (HPV-11 and HPV-18) in group HPV4 + Tdap + MenACWY and from 99.0% (HPV-11 and HPV-16) to 99.7% (HPV-6 and HPV-18) in group HPV4 + Tdap + Placebo.

Conclusion

Overall, these data support the concomitant administration of HPV4, Tdap and MenACWY-CRM in adolescents.

Funding

Novartis Vaccines and Diagnostics Inc., now part of the GSK group of companies.

Trial Registration

ClinicalTrials.gov identifier, NCT01424644.

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.

Establishment of xMAP for the simultaneous detection of antibodies to Newcastle disease virus and avian influenza virus

Using Luminex xMAP (x = analyte, MAP = multi-analyte profiling) technology, a serological method for the simultaneous detection of antibodies to Newcastle disease virus (NDV) and avian influenza virus (AIV) was established. Nano-magnetic beads coated with purified NDV protein and AIV nucleoprotein were incubated with serum samples. Using biotinylated rabbit anti-chicken IgY and streptavidin-R-phycoerythrin, the optical signals measured by a Luminex 200 detection system indicated the quantification of NDV or AIV antibodies in the serum. Specific pathogen-free (SPF) chicken serum was used as a negative control. The Luminex xMAP assay developed in this study demonstrated high specificity as there was no cross-reaction with antibodies to infectious laryngotracheitis virus, infectious bronchitis virus, infectious bursal disease virus, avian leukosis virus, and Marek's disease virus. The results from reproducibility experiments showed that intra-coefficients of variation were 3.36 and 9.23% and inter-coefficients of variation were 6.50 and 7.66% for NDV and AIV, respectively. The results also indicated that the Luminex xMAP assay was 16 times more sensitive for NDV antibody detection and 1,024 times more sensitive for AIV antibody detection compared to the enzyme-linked immunosorbent assay (ELISA). A total of 300 chicken serum samples were subjected to both Luminex xMAP assay and ELISA, showing the coincidence rates of 98.67 and 98% for NDV and AIV antibody detection, respectively. This study provides a new method for the simultaneous detection NDV and AIV antibodies in the serum with high specificity and sensitivity.

The effect of a booster dose of HPV tetravalent vaccine after 51 months: implications for extended vaccination schedules

OBJECTIVE

To asses the non-inferiority between two differ- ent vaccination schedules one month after the administration of the third dose.

MATERIALS AND METHODS

We evaluated the anti-HPV 16/18 antibody titers induced by quadrivalent HPV vaccine administered using two different schedules in girls 9 to 10-year-old girls: a traditional (0-2-6) and an alterna- tive (0-6-50). Blood samples were collected at month 7, 21 and 51.

RESULTS

The antibody geometric mean titer ratios one month after the application of the third dose -month 51 for the alternative and month 7 for the traditional- were 1.55 for HPV16 (95%CI, 1.15-2.08) and 1.53 for HPV18 (95%CI, 1.12-2.09). The seropositive rate was above 99% in both groups.

CONCLUSIONS

The application of an alternative 3-dose schedule in 9 to 10-year-old girls induces a non-inferior immune response compared to the standard one month after the last dose. Further research is needed to understand the minimal number of doses and their timing to provide the best coverage for HPV infection.

Development and validation of a robust multiplex serological assay to quantify antibodies specific to pertussis antigens

Despite wide spread vaccination, the public health burden of pertussis remains substantial. Current acellular pertussis vaccines comprise upto five Bordetella pertussis (Bp) antigens. Performing an ELISA to quantify antibody for each antigen is laborious and challenging to apply to pediatric samples where serum volume may be limited. We developed a microsphere based multiplex antibody capture assay (MMACA) to quantify antibodies to five pertussis antigens; pertussis toxin, pertactin, filamentous hemagglutinin and fimbrial antigens 2/3, and adenylate cyclase toxin in a single reaction (5-plex) with a calibrated reference standard, QC reagents and SAS^® based data analysis program. The goodness of fit (R²) of the standard curves for five analytes was ≥0.99, LLOQ 0.04-0.15 IU or AU/mL, accuracy 1.9%-23.8% (%E), dilutional linearity slopes 0.93-1.02 and regression coefficients r² = 0.91-0.99. MMACA had acceptable precision within a median CV of 16.0%-22.8%. Critical reagents, antigen conjugated microsphere and reporter antibody exhibited acceptable (<12.3%) lot-lot variation. MMACA can be completed in <3 h, requires low serum volume (5μL/multiplex assay) and has fast data turnaround time (<1 min). MMACA has been successfully developed and validated as a sensitive, specific, robust and rugged method suitable for simultaneous quantification of anti-Bp antibodies in serum, plasma and DBS.

Quadrivalent HPV vaccine in HIV-1-infected early adolescent girls and boys in Kenya: Month 7 and 12 post vaccine immunogenicity and correlation with immune status

INTRODUCTION

In sub-Saharan Africa, a generation of HIV-1-infected children is approaching the age of sexual debut and becoming at risk for HPV infection and its sequelae. We assessed safety and immunogenicity of the quadrivalent HPV (qHPV) vaccine in HIV-1-infected adolescents.

METHODS

In an open-label trial among Kenyan, HIV-1-infected adolescents aged 9-14 years, we administered the qHPV vaccine at 0, 2 and 6 months and measured antibody titers to HPV-16, 18, 6 and 11 at month 7 and 12 post-vaccination. Measures of immunogenic response from HIV-1-negative historical cohorts from Africa and HIV-1 positive adolescent cohorts from the USA were used for comparison.

RESULTS

We enrolled 100 girls and 80 boys with a median age of 12 years and median baseline CD4 cell count of 684 (IQR 478, 935) cells/µL. One hundred and fifty four (86%) were receiving antiretroviral therapy for a median of 4.5 (IQR 2.3, 6.3) years; 110 (71%) had <400 copies of plasma HIV-1 RNA/mL. Of 189 enrolled children, 179 received all three doses. Two hundred and eighty five (64%) of 445 adverse events were injection site reactions; none were greater than grade 2. Of 6 Serious Adverse Events (SAEs), none were considered vaccine related. Seroconversion to HPV-18, 16, 11, 6 at month 7 occurred in 93.3%, 98.3%, 97.2% and 99.6% of vaccine recipients; similar rates have been reported in historical controls. The mean log₁₀ HPV antibody titer measured at month 7 increased with each log₁₀ increase in CD4 by 1.4 (95% CI: 1.1-1.7) for HPV-18; 1.2 (0.9-1.4) for HPV-16; 1.1 (0.8-1.3) for HPV-11; 0.7 (0.5-1.0) for HPV-6 (all p < 0.0001).

CONCLUSION

Almost all Kenyan HIV-1-infected adolescents mounted an immune response comparable to other immunized populations. HPV antibody titers were higher in those with preserved CD4 cell counts. Longer term-follow up will determine sustainability of the immune response. ClinicalTrials.gov number, NCT00557245.

Development of a sensitive and specific xMAP assay for detection of antibodies against infectious laryngotracheitis and bronchitis viruses

BACKGROUND

A serological method to simultaneously detect antibodies against infectious laryngotracheitis virus (ILTV) and infectious bronchitis virus (IBV) is imperative for the differential diagnosis and evaluation of antibodies titers after vaccination.

METHOD

The microspheres coated with purified recombinant glycoprotein D (gD) of ILTV or nucleocapsid (N) protein of IBV were incubated with serum samples. The simultaneous quantification of ILTV and IBV antibodies were achieved through the interrogation of microspheres by Luminex 200 detection system. .

RESULTS

This xMAP detection demonstrated no nonspecific reactions with avian influenza virus (AIV), avian leukosis virus (ALV), newcastle disease virus (NDV), and Marek's disease virus (MDV). The results also demonstrated that the xMAP assay was four times more sensitive than the enzyme-linked immunosorbent assay (ELISA) for ILTV detection and two times more sensitive for IBV detection. A total of 90 chicken serum samples from a chicken farm were tested by xMAP and ELISA assays. The results showed that the coincidence rates were 84.44 and 100% for ILTV and IBV detection, respectively.

CONCLUSION

This study exhibited an opportunity for the differential diagnosis through simultaneous detection of multiplex antibodies in serum and can be used for the multiplex antibodies evaluation after vaccination.

Development and characterization of an HPV18 detection kit using two novel HPV18 type-specific monoclonal antibodies

Background

HPV 18 is one of the most prevalent oncogenic types, only second to HPV 16, and included in the licensed vaccines on the market. In this study, we describe the production and characterization of a panel of monoclonal antibodies (mAb) to HPV18.

Methods

The immunocompetence of 1B1 and 4C2 mAbs for HPV L1 protein was evaluated by SDS-PAGE analysis, neutralization assays, affinity identification, and ELISA. The 1B1 and 4C2 genes were sequenced and analyzed. Finally, the detection kit with the two mAbs was assessed for linearity, repeatability and specificity.

Results

Both mAbs specifically recognized HPV18 L1 and virus-like particles (VLPs). These mAbs are conformation-neutralizing antibodies that have high affinity and type specificity. Based on these characteristics of these mAbs, we developed an ELISA kit for specifically detecting HPV 18 antigen. We showed that this kit displayed good linearity, repeatability and sensitivity for detecting HPV18 L1 pentamer and HPV18 VLP.

Conclusions

We characterized two monoclonal neutralizing antibodies for HPV L1 protein, and developed an ELISA kit for specifically detecting HPV 18 antigen. This newly developed kit can be used to monitor the potency of HPV vaccines throughout the entire production process as well as preliminary analysis of HPV18 infections.

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

When administered as standard three-dose schedules, the licensed HPV prophylactic vaccines have demonstrated extraordinary immunogenicity and efficacy. We summarize the immunogenicity of these licensed vaccines and the most commonly used serology assays, with a focus on key considerations for one-dose vaccine schedules. Although immune correlates of protection against infection are not entirely clear, both preclinical and clinical evidence point to neutralizing antibodies as the principal mechanism of protection. Thus, immunogenicity assessments in vaccine trials have focused on measurements of antibody responses to the vaccine. Non-inferiority of antibody responses after two doses of HPV vaccines separated by 6 months has been demonstrated and this evidence supported the recent WHO recommendations for two-dose vaccination schedules in both boys and girls 9-14 years of age. There is also some evidence suggesting that one dose of HPV vaccines may provide protection similar to the currently recommended two-dose regimens but robust data on efficacy and immunogenicity of one-dose vaccine schedules are lacking. In addition, immunogenicity has been assessed and reported using different methods, precluding direct comparison of results between different studies and vaccines. New head-to-head vaccine trials evaluating one-dose immunogenicity and efficacy have been initiated and an increase in the number of trials relying on immunobridging is anticipated. Therefore, standardized measurement and reporting of immunogenicity for the up to nine HPV types targeted by the current vaccines is now critical. Building on previous HPV serology assay standardization and harmonization efforts initiated by the WHO HPV LabNet in 2006, new secondary standards, critical reference reagents and testing guidelines will be generated as part of a new partnership to facilitate harmonization of the immunogenicity testing in new HPV vaccine trials.

Generalized ROC methods for immunogenicity data analysis of vaccine phase I studies in a seropositive population

Immunogenicity data from phase 1 vaccine studies can be difficult to interpret, especially in seropositive populations and when multiple assays are used. We developed 3 statistical methods (Youden index [YI] threshold, receiver-operating characteristic relative to baseline [ROC-B], and ROC of postdose levels [ROC-P]) to characterize complex immunogenicity data by assessing the proportion of a study population that achieved values above thresholds. The YI method calculates a single threshold per assay. Both ROC methods construct ROC curves for individual assays and surfaces for assay combinations to assess degree of separation of postdose values from a reference distribution; the ROC-B method uses overall predose values as the reference distribution and the ROC-P method uses pooled postdose values. All methods are applicable to a seropositive population with overlapping distributions of baseline and postdose measurements and can evaluate results of multiple assays jointly. The ROC-P method is also applicable when postdose levels are fully separated from baseline levels, as is common in a seronegative population. These methods were demonstrated using data from a phase 1a study of respiratory syncytial virus vaccines formulated with and without an adjuvant in a seropositive population of adults aged ≥60 years. All 3 methods provided a comprehensive assessment of vaccine immunogenicity effects with results presented in easily interpretable formats. In the example data, the methods demonstrated antigen dose response trend and contribution of adjuvant to response in multiple assays individually and jointly where optimal responses in assay combinations (humoral and cellular) are important.

L1 Recombinant Proteins of HPV Tested for Antibody Forming Using Sera of HPV Quadrivalent Vaccine

Virus-like particles (VLPs) derived from human papillomavirus (HPV) L1 capsid proteins were used for HPV quadrivalent recombinant vaccine. The HPV quadrivalent vaccine is administrated in a 3-dose regimen of initial injection followed by subsequent doses at 2 and 6 months to prevent cervical cancer, vulvar, and vaginal cancers. The type 6, 11, 16, or 18 of HPV infection is associated with precancerous lesions and genital warts in adolescents and young women. The HPV vaccine is composed of viral L1 capsid proteins are produced in eukaryotic expression systems and purified in the form of VLPs. Four different the L1 protein of 3 different subtypes of HPV: HPV11, HPV16, and HPV18 were expressed in Escherichia coli divided into 2 fragments as N- and C-terminal of each protein in order to examine the efficacy of HPV vaccine. Vaccinated sera failed to recognize N-terminal L1 HPV type 16 and type 18 by western blot while they detected N-terminal L1 protein of HPV type 11. Moreover, the recombinant C-terminal L1 proteins of type 16 was non-specifically recognized by the secondary antibody conjugated with horseradish peroxidase. This expression and purification system may provide simple method to obtain robust recombinant L1 protein of HPV subtypes to improve biochemical analysis of antigens with immunized sera.

Population-Level Herd Protection of Males From a Female Human Papillomavirus Vaccination Program: Evidence from Australian Serosurveillance

Background

Australia instituted funded female human papillomavirus (HPV) immunization in 2007, followed by a targeted male vaccination program in 2013. To date, Australia is one of only several countries with a funded male HPV immunization program. In 2012-2013, we conducted a survey of HPV seroprevalence in males to assess whether or not a herd impact of female vaccination could be observed.

Methods

We conducted a cross-sectional study of de-identified residual diagnostic test serum samples from males aged 15-39 years from laboratories in 3 Australian states and calculated the proportion seropositive to HPV types 6, 11, 16, and 18. We compared type-specific results by age group against those from a baseline 2005 Australian HPV serosurvey.

Results

There were decreases in proportion seropositive for every HPV type across all age groups, many statistically significant. The largest decrease was observed for HPV-11, with decreases of 8- and 9-fold for ages 20-29 and 30-39 years, respectively. Despite substantial reductions in seroprevalence, at least 9% of males were seropositive for at least 1 of the 4 HPV types.

Conclusions

This is the first serosurvey confirming broad population-level impact in males from female HPV vaccination. Our research may assist policy makers considering implementing HPV vaccination programs.

Evaluation on the persistence of anti-HPV immune responses to the quadrivalent HPV vaccine in Chinese females and males: Up to 3.5 years of follow-up

BACKGROUND

This was an extension study of a randomized, double-blind, placebo-controlled immunogenicity and safety study of the quadrivalent human papillomavirus (qHPV) (HPV 6, 11, 16, and 18) vaccine conducted in Chinese female subjects aged 9-45 years and male subjects aged 9-15 years. To investigate the persistence of anti-HPV 6, -11, -16, and -18 responses among Chinese subjects, subjects enrolled in the base study were followed up at around month 42 (approximately 3.5 years after vaccination).

METHODS

Among 600 subjects enrolled in the base study, a total of 468 subjects consented for participation in the extension study. Anti-HPV 6, -11, -16, and -18 antibodies were detected by the competitive Luminex immunoassay (cLIA) and total IgG Luminex immunoassay (IgG LIA).

RESULTS

Among the female subjects who received the qHPV vaccine, the proportions of subjects remained seropositive were high with both the cLIA and IgG LIA for HPV type 6, 11, and 16 through approximately 42 months following the first dose vaccination. For HPV 18, the seropositivity rate remained high as 82.0% with the IgG LIA, while it decreased to 53.6% with the cLIA, which was similar to the findings observed in other studies. The seropositivity rates remained high at month 42 for all qHPV types with both the cLIA and IgG LIA among the male subjects.

CONCLUSIONS

Administration of a 3-dose regimen of qHPV vaccine induces durable anti-HPV 6, anti-HPV 11, anti-HPV 16, and anti-HPV 18 responses among Chinese subjects for at least 3.5 years after vaccination. ClinicalTrials.gov registry:NCT01427777.

Photocleavage-based affinity purification of biomarkers from serum: Application to multiplex allergy testing

Multiplex serological immunoassays, such as implemented on microarray or microsphere-based platforms, provide greater information content and higher throughput, while lowering the cost and blood volume required. These features are particularly attractive in pediatric food allergy testing to facilitate high throughput multi-allergen analysis from finger- or heel-stick collected blood. However, the miniaturization and microfluidics necessary for creating multiplex assays make them highly susceptible to the “matrix effect” caused by interference from non-target agents in serum and other biofluids. Such interference can result in lower sensitivity, specificity, reproducibility and quantitative accuracy. These problems have in large part prevented wide-spread implementation of multiplex immunoassays in clinical laboratories. We report the development of a novel method to eliminate the matrix effect by utilizing photocleavable capture antibodies to purify and concentrate blood-based biomarkers (a process termed PC-PURE) prior to detection in a multiplex immunoassay. To evaluate this approach, it was applied to blood-based allergy testing. Patient total IgE was purified and enriched using PC-PURE followed by multiplex microsphere-based detection of allergen-specific IgEs (termed the AllerBead assay). AllerBead was formatted to detect the eight most common pediatric food allergens: milk, soy, wheat, egg, peanuts, tree nuts, fin fish and shellfish, which account for >90% of all pediatric food allergies. 205 serum samples obtained from Boston Children’s Hospital were evaluated. When PC-PURE was employed with AllerBead, excellent agreement was obtained with the standard, non-multiplex, ImmunoCAP^® assay (average sensitivity above published negative predictive cutoffs = 96% and average Pearson r = 0.90; average specificity = 97%). In contrast, poor ImmunoCAP^®-correlation was observed when PC-PURE was not utilized (average sensitivity above published negative predictive cutoffs = 59% and average Pearson r = 0.61; average specificity = 97%). This approach should be adaptable to improve a wide range of multiplex immunoassays such as in cancer, infectious disease and autoimmune disease.

9-Valent human papillomavirus vaccine: a review of the clinical development program

INTRODUCTION

The 9-valent human papillomavirus (9vHPV) vaccine covers the same HPV types (6/11/16/18) as the quadrivalent HPV (qHPV) vaccine and 5 additional cancer-causing types (31/33/45/52/58). Epidemiological studies indicate that the 9vHPV vaccine could prevent approximately 90% of cervical cancers, 70-85% of high-grade cervical dysplasia (precancers), 85-95% of HPV-related vulvar, vaginal, and anal cancers, and 90% of genital warts. Areas covered: Study design features and key findings from the 9vHPV vaccine clinical development program are reviewed. In particular, 9vHPV vaccine efficacy was established in a Phase III study in young women age 16-26 years. Efficacy results in young women were extrapolated to pre- and young adolescent girls and boys and young men by immunological bridging (i.e., demonstration of non-inferior immunogenicity in these groups versus young women). Expert commentary: The development of the 9vHPV vaccine is the outcome of 20 years of continuous clinical research. Broad vaccination programs could help substantially decrease the incidence of HPV-related disease.

Expanded strain coverage for a highly successful public health tool: Prophylactic 9-valent human papillomavirus vaccine

Human papillomavirus is considered the causative factor for cervical cancer, which accounts for approximately 5% of the global cancer burden and more than 600,000 new cases annually that are attributable to HPV infection worldwide. The first-generation prophylactic HPV vaccines, Gardasil® and Cervarix®, were licensed approximately a decade ago. Both vaccines contain the most prevalent high-risk types, HPV16 and 18, which are associated with 70% of cervical cancer. To further increase the type coverage, 5 additional oncogenic HPV types (31, 33, 45, 52 and 58) were added to the existing Gardasil-4 to develop a 9-valent HPV vaccine (9vHPV), Gardasil 9®, increasing the potential level of protection from ∼70% to ∼90%. The efficacy of the vaccine lies primarily in its ability to elicit type-specific and neutralizing antibodies to fend off the viral infection. Therefore, type-specific and neutralizing murine monoclonal antibodies (mAbs) were used to quantitate the antigenicity of the individual vaccine antigens and to measure the antibody levels in the serum samples from vaccinees in a type- and epitope-specific manner in a competitive immunoassay. Assays for 9vHPV are extended from the proven platform used for 4vHPV by developing and adding new mAbs against the additional types. In Phase III clinical trials, comparable safety profile and immunogenicity against the original 4 types were demonstrated for the 9vHPV vaccine, and these were comparable to the 4vHPV vaccine. The efficacy of the 9vHPV vaccine was established in trials with young women. Immunobridging for younger boys and girls was performed, and the results showed higher immunogenicity in the younger age group. In a subsequent clinical trial, the 2-dose regimen of the 9vHPV vaccine used among girls and boys aged 9-14 y showed non-inferior immunogenicity to the regular 3-dose regimen for young women (aged 16-26 years). Overall, the clinical data and cost-effectiveness analysis for the 9vHPV vaccine support its widespread use to maximize the impact of this important, life-saving vaccine.

Brief Report: Antibody Responses to Quadrivalent HPV Vaccination in HIV-Infected Young Women as Measured by Total IgG and Competitive Luminex Immunoassay

We compared antibody responses of HIV-infected young women to the human papillomavirus (HPV) 6, 11, 16, and 18 vaccine using total immunoglobulin (Ig) G Luminex immunoassay (LIA) and competitive Luminex immunoassay (cLIA) assays. HPV18 seropositivity after HPV vaccination as measured with IgG LIA remained high (98%) 48 weeks after vaccination, in contrast with seropositivity as measured with cLIA (73%). Seropositivity rates at week 48 as measured by both IgG LIA and cLIA remained high for HPV6, 11, and 16 (93.5%-100%). These results suggest that the lower rate of seropositivity to HPV18 when cLIA vs. IgG LIA is used is a function of the assay and does not imply lower vaccine immunogenicity.

Top-down fabrication meets bottom-up synthesis for nanoelectronic barcoding of microparticles

Traditional optical and plasmonic techniques for barcoding of micro-particles for multiplexed bioassays are generally high in throughput, however bulky instrumentation is often required for performing readout. Electrical impedance based detection allows for ultra-compact instrumentation footprint necessary for wearable devices, however to date, the lack of ability to electronically barcode micro-particles has been a long standing bottleneck towards enabling multiplexed electronic biomarker assays. Nanoelectronic barcoding, which to the best of our knowledge is the first impedance based solution for micro-particle barcoding, works by forming tunable nano-capacitors on the surface of micro-spheres, effectively modulating the frequency dependent dielectric properties of the spheres allowing one bead barcode to be distinguished from another. Nanoelectronic barcoding uses a well-known, but unexplored electromagnetic phenomenon of micro-particles: the Clausius-Mossotti (CM) factor spectrum of a Janus particle (JP) shifts depending on the zeta (wall) potential of the metallic half of the microsphere, and the fact that the complex impedance spectrum of a particle directly corresponds to the CM factor spectrum. A one-to-one correspondence will be established between each biomarker and the corresponding engineered microsphere. This transformative new method for barcoding will enable a new class of handheld and wearable biosensors capable of multiplexed continuous temporal bio-monitoring. The proposed nano-electronically barcoded particles utilize both bottom-up synthesis and top-down fabrication to enable precisely engineered frequency dependent dielectric signatures. Multi-frequency lock-in measurements of the complex impedance, in conjunction with multi-variate analysis of impedance data, allows for particle differentiation using a fully functional ultra-compact electronic detector.

Four-year persistence of type-specific immunity after quadrivalent human papillomavirus vaccination in HIV-infected children: Effect of a fourth dose of vaccine

OBJECTIVE

Although HIV-infected children are recommended to receive quadrivalent human papillomavirus vaccine (QHPV) there is limited information on their response to QHPV. This study in HIV-infected children, evaluated the magnitude and duration of immune responses to QHPV. This report describes type-specific serum antibody responses over a 4-to-5year period after either 3 or 4 doses of QHPV.

DESIGN/METHODS

HIV-infected children, ages 7-to-11years, received 3 doses of QHPV (n=96) or placebo (n=30). At 72weeks QHPV recipients received a fourth dose (n=84), while placebo recipients began the 3-dose QHPV schedule (n=27). HPV serotype-specific antibody was determined, by competitive Luminex immunoassay (cLIA) and IgG Luminex immunoassay, at 2, 3.5, and 4-to-5years after the last dose of QHPV in each treatment arm.

RESULTS

At 4-to-5years after the last dose of QHPV, antibody titers were significantly higher in 4-dose than in 3-dose group. However, the proportion of vaccinees with a seroresponse in the cLIA assay was not different between the two groups (86-93% for HPV types 6, 11, and 16, and 64% for HPV type 18). These results were very similar to the seroresponse rate in these HIV-infected children at 1month after completing vaccination.

CONCLUSIONS

Children with well-controlled HIV infection who receive 3 doses of the QHPV vaccine maintain seropositivity and antibody levels that are generally similar to children of the same age who are not HIV-infected. Antibody titer correlated strongly with low log HIV RNA, low CD8%, and high CD4%. Additionally, a fourth dose of vaccine in HIV-infected children produces a marked rise in antibody characteristic of an anamnestic response and persistence of high antibody levels. Study identification: IMPAACT P1085 (V501-021). CLINICALTRIALS.GOV identifier: NCT01206556.

Prevalence of HPV 16 and 18 and attitudes toward HPV vaccination trials in patients with cervical cancer in Mali

Background

Cervical cancer is one of the most common and lethal cancers in West Africa. Even though vaccines that protect against the most common Human papillomavirus (HPV) strains, 16 and 18, are currently in use in developed countries, the implementation of these vaccines in developing countries has been painfully slow, considering the pre-eminence of HPV-associated cervical cancer among women in those countries.

Aim

We performed serological and PCR-based assessment of blood and tissue specimens obtained from women undergoing cervical cancer-related surgery at a major urban hospital in Bamako. Since several therapeutic HPV vaccines are currently in clinical trials, we also assessed willingness to participate in HPV cancer vaccine trials.

Methods

Blood and biopsy samples of 240 women were evaluated for HPV types 16 and 18 by serology and PCR. Knowledge regarding the HPV vaccine and autonomy to decide to vaccinate their own child was assessed with a standardized questionnaire.

Results

HPV 16 and 18 were identified in 137/166 (82.5%) cervical cancer biopsy samples by PCR. Co-infection with both HPV 16 and 18 was significantly more frequent in women over 50 years of age than in younger women (63.0% vs. 37.0%). 44% of study participants said they would be willing to vaccinate their child with HPV vaccine. Only 39% of women participating in this study reported that they would be able to make an autonomous decision to receive HPV vaccination. Permission from a male spouse or head of household was identified as important for participation by 59% of the women.

Conclusion

This study provides strong support for the introduction of currently available HPV vaccines in Mali, and also provides key information about conditions for obtaining informed consent for HPV vaccine trials and HPV vaccination in Mali.

Enhancement of humoral and cell mediated immune response to HPV16 L1-derived peptides subsequent to vaccination with prophylactic bivalent HPV L1 virus-like particle vaccine in healthy females

Currently prophylactic HPV16/18 L1 virus-like particle (VLP) vaccines are employed with great success for the prevention of HPV infection. However, limited information is available regarding the immune responses against human papillomavirus (HPV) 16/18 L1 subsequent to HPV16/18 L1 VLP vaccination, primarily due to the lack of widely used assays for immune monitoring. The aim of the present study was to identify HPV16 L1-derived B and T cell epitopes for monitoring the immune responses after HPV16/18 L1 VLP vaccination in healthy females. The levels of immunoglobulin G (IgG), IgE, IgA and IgM reactive to HPV16 L1-derived peptides were measured by multiplex bead suspension assay. Following detailed B cell epitope mapping, T cell responses specific to HPV16 L1-derived peptides were evaluated by an IFN-γ ELISPOT assay. The levels of IgG, IgM and IgA reactive to 20-mer peptides (PTPSGSMVTSDAQIFNKPYW) at positions 293-312 and 300-319 of HPV16 L1 were significantly increased in the plasma after 2, 7, and 12 months after first vaccination. Detailed epitope mapping identified the amino acid sequence (TSDAQIFNKP) at position 301-310 of HPV16 L1 as an immunogenic B cell epitope. In addition, T cell responses to an HLA-A2- and HLA-A24-restricted epitope (QIFNKPYWL) at position 305-313 of HPV16 L1 were increased following immunization, suggesting that the HPV16/18 L1-VLP vaccination as able to induce specific immune responses in T and B cells simultaneously. The identified B and T cell epitopes may be useful as a biomarker for monitoring the immune responses subsequent to HPV16/18 L1 VLP vaccination. Thus, the present study may provide novel information to improve the understanding of the immune responses to HPV16 L1.

Decreased HHV-6 IgG in Alzheimer's Disease

Human herpesviruses have previously been implicated in the pathogenesis of Alzheimer's disease (AD) but whether they are causal, facilitating, or confounding factors is yet to be established. A total of 50 AD subjects and 52 non-demented (ND) controls were analyzed in a multiplex assay for IgG reactivity toward herpes simplex virus (HSV), varicella zoster virus (VZV), cytomegalovirus (CMV), and human herpesvirus 6 (HHV-6). The HHV-6 IgG reactivity was significantly lower in AD subjects compared to ND controls, whereas there were no differences in HSV, VZV, or CMV antibody levels between the groups. Analysis of peripheral blood mononuclear cells with a subtype-specific HHV-6 PCR revealed no signs of reactivation, as AD and ND subjects presented with comparable HHV-6 DNA levels in PBMCs, and all positive samples were of subtype B. Whether HHV-6 is a factor in AD remains to be elucidated in future studies.