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

Scientific approaches to defining HPV vaccine-induced protective immunity

Seventeen years after the licensure of prophylactic human papillomavirus (HPV) L1 virus-like-particle vaccines, a defined antibody level that correlates with vaccine-induced protection against HPV infections and associated neoplasia is missing. In contrast, correlates of protection have been defined for many viral vaccines, including for the hepatitis B virus (HBV) vaccine. This review includes lessons learned from vaccination against HBV and the use of an established protective HBV surface antigen antibody level: 10 mIU/mL, an overview of HPV infection-induced and HPV vaccine-induced antibody responses, successful efforts to establish international standardization of serological reagents and associated tools, and 15-year vigilance of HPV vaccine-induced antibody levels in a vaccination cohort against breakthrough infections. This report identifies progress but also gaps on the journey toward the definition of a HPV vaccine-induced correlate of protection.

Engineered thermoswitch in the baculovirus expression vector system for production of virus-like particle vaccines with minimized baculovirus contaminants

The baculovirus expression vector system (BEVS) is commercially used for producing recombinant (glyco)proteins, gene therapy vectors, and virus-like particles (VLPs) in insect cells. A major challenge in VLP downstream processing (DSP) is the removal of similarly sized baculovirus particle contaminants. Herein we engineered a genetic ON/OFF thermoswitch in the baculovirus vector by mutating the essential gp41 gene. This temperature-sensitive (ts) baculovirus expression system (BacFreets) produces high baculovirus titers at 27°C, while contaminating baculovirus production switches off at elevated temperatures. We demonstrate scalable VLP production for chikungunya virus (CHIKV), West Nile virus (WNV), coxsackievirus A6, and foot-and-mouth disease virus (FMDV) at 33°C, concomitant with baculovirus particle reduction up to 99.97%. However, elevated temperature moderately affected the yield of two out of four VLP designs. BacFreets is compatible with commonly used insect cells and scalable infection strategies. BacFreets effectively reduces baculovirus contaminants in the upstream VLP production phase, which will facilitate DSP of human and veterinary VLP-based vaccines.

Systems serology analysis shows IgG1 and IgG3 memory responses six years after one dose of quadrivalent HPV vaccine

The WHO has given a permissive recommendation for an off-label one-dose human papillomavirus (HPV) vaccine schedule to prevent cervical cancer, based on evidence of comparable protection to two or three doses of vaccine. While neutralizing antibodies are thought to be the primary mechanism of protection, the persistence of immunity and whether other antibody-mediated mechanisms of protection are involved is unclear. Using systems serology, we investigated HPV antibody responses in serum from Fijian girls who were unvaccinated or received one, two or three doses of quadrivalent HPV vaccine six years earlier. We also evaluated their HPV antibody responses 28 days following a dose of bivalent HPV vaccine. After six years, one dose induced lower antibody concentrations but similar antibody profiles and phagocytic function as two or three doses. Following bivalent vaccine, antibody concentrations, particularly IgG1/IgG3, antibody profiles and phagocytic function were similar between previously vaccinated girls, indicating immune memory after one dose. Cross-reactive antibody responses against non-vaccine genotypes (HPV31/33/45/52/58) were lower following one dose than two or three doses. These findings provide novel insights into serological immunity and recall responses following one-dose HPV vaccination.

Combination adjuvant improves influenza virus immunity by downregulation of immune homeostasis genes in lymphocytes

Adjuvants play a central role in enhancing the immunogenicity of otherwise poorly immunogenic vaccine antigens. Combining adjuvants has the potential to enhance vaccine immunogenicity compared with single adjuvants, although the cellular and molecular mechanisms of combination adjuvants are not well understood. Using the influenza virus hemagglutinin H5 antigen, we define the immunological landscape of combining CpG and MPLA (TLR-9 and TLR-4 agonists, respectively) with a squalene nanoemulsion (AddaVax) using immunologic and transcriptomic profiling. Mice immunized and boosted with recombinant H5 in AddaVax, CpG+MPLA, or AddaVax plus CpG+MPLA (IVAX-1) produced comparable levels of neutralizing antibodies and were equally well protected against the H5N1 challenge. However, after challenge with H5N1 virus, H5/IVAX-1-immunized mice had 100- to 300-fold lower virus lung titers than mice receiving H5 in AddaVax or CpG+MPLA separately. Consistent with enhanced viral clearance, unsupervised expression analysis of draining lymph node cells revealed the combination adjuvant IVAX-1 significantly downregulated immune homeostasis genes, and induced higher numbers of antibody-producing plasmablasts than either AddaVax or CpG+MPLA. IVAX-1 was also more effective after single-dose administration than either AddaVax or CpG+MPLA. These data reveal a novel molecular framework for understanding the mechanisms of combination adjuvants, such as IVAX-1, and highlight their potential for the development of more effective vaccines against respiratory viruses.

Unveiling the seroprevalence of human papillomavirus in Guangdong, China: Implications for vaccination strategies

Seroepidemiological characteristics of human papillomavirus (HPV) in community residents reflect natural infection and can guide the reform of vaccination programs. A population-based serological survey was conducted in Guangdong Province. Serum anti-HPV IgG antibody levels were determined by an ELISA. Neutralizing antibodies against HPV6, 11, 16, and 18 were detected via a pseudovirus-based neutralization assay (PBNA). A total of 5122 serum samples were collected from community residents, including 1989 males and 3133 females, in three cities of Guangdong Province. The rate of HPV IgG antibody positivity in females was 5.39% (95% CI: 4.6-6.2), which was greater than that in males (2.36%; 95% CI: 1.7-3.1). HPV IgG antibodies were more frequently detected in females aged 51-60 years (11.30%; 95% CI: 7.6-16.0), whereas in males, the detection increased with age and reached 4.94% (95% CI: 2.8-6.9) in the group aged ≥71 years. The seropositivity of neutralizing antibodies against HPV6 and 11 was greater than that against HPV16 and 18. The serum neutralizing antibody titers in individuals who received three doses of a vaccine were 7- to 12-fold greater than those in individuals who did not receive the vaccine. The neutralizing antibody titers slightly decreased within 40 months and ranged from 0.038 to 0.057 log ED50 per month. A moderate consistency between the HPV ELISA and PBNA results was observed (Kappa score = 0.49, r = 0.249, 0.635, 0.382, and 0.466 for HPV6, 11, 16, and 18, respectively). The HPV seropositivity rate among healthy residents of Guangdong Province was found to be low among children and adolescents and to increase with age. The serum neutralizing antibody titers were significantly greater in the vaccine group than that in the control group, and this difference persisted over time, which indicated promising protection against HPV infection.

The Clinical Effectiveness of Single-Dose Human Papillomavirus Vaccination

The human papillomavirus (HPV) vaccine was initially approved for a three-dose regimen. Due to resource limitations, budget constraints, low acceptance, and poor adherence, global vaccination coverage is only 15%. A single-dose regimen could simplify logistics, reduce costs, and improve accessibility. However, its clinical effectiveness remains debatable. This review systematically searched PubMed, Embase, and Cochrane Library, including 42 clinical studies, to assess the effectiveness of a single-dose HPV vaccination for preventing HPV infections, cervical abnormalities, and genital warts. We summarized the effectiveness of bivalent, quadrivalent, and nonavalent vaccines across different age groups and buffer periods, and analyzed the factors contributing to the inconsistency of results. The review also provides insights into designing robust future research to inform single-dose HPV vaccination policies and guidelines, highlighting the need for further research to refine vaccination strategies.

Lack of detectable HPV18 antibodies in 14% of quadrivalent vaccinees in a longitudinal cohort study

Although HPV vaccines are highly efficacious, a notable proportion of quadrivalent vaccinees are HPV18 seronegative post-vaccination. We have investigated this findings' validity by comparing vaccine-induced antibody responses using two different immunoassays. 6558 16-17-year-old females participated in the FUTURE II (NCT00092534) and PATRICIA (NCT00122681) trials in 2002-2004. Both the quadrivalent and bivalent vaccine recipients (QVR and BVR) received three doses. Twelve-year follow-up for 648 vaccinees was conducted by the Finnish Maternity Cohort. The presence of neutralising and binding HPV antibodies was analysed via HPV pseudovirion-based neutralisation and pseudovirion-binding assays. Four percent and 14.3% of the QVRs were seronegative for neutralising and binding antibodies to HPV16 and HPV18, respectively. No BVRs were HPV16/18 seronegative post-vaccination. The antibody titres were strongly correlated between the assays, Pearson's correlation coefficient, r[HPV16] = 0.92 and 0.85, and r[HPV18] = 0.91 and 0.86 among the QVRs and BVRs respectively. Fourteen percent of QVRs lacked detectable HPV18 antibodies in long-term follow-up.

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.

Beyond bNAbs: Uses, Risks, and Opportunities for Therapeutic Application of Non-Neutralising Antibodies in Viral Infection

The vast majority of antibodies generated against a virus will be non-neutralising. However, this does not denote an absence of protective capacity. Yet, within the field, there is typically a large focus on antibodies capable of directly blocking infection (neutralising antibodies, NAbs) of either specific viral strains or multiple viral strains (broadly-neutralising antibodies, bNAbs). More recently, a focus on non-neutralising antibodies (nNAbs), or neutralisation-independent effects of NAbs, has emerged. These can have additive effects on protection or, in some cases, be a major correlate of protection. As their name suggests, nNAbs do not directly neutralise infection but instead, through their Fc domains, may mediate interaction with other immune effectors to induce clearance of viral particles or virally infected cells. nNAbs may also interrupt viral replication within infected cells. Developing technologies of antibody modification and functionalisation may lead to innovative biologics that harness the activities of nNAbs for antiviral prophylaxis and therapeutics. In this review, we discuss specific examples of nNAb actions in viral infections where they have known importance. We also discuss the potential detrimental effects of such responses. Finally, we explore new technologies for nNAb functionalisation to increase efficacy or introduce favourable characteristics for their therapeutic applications.

Unravelling the Impact of Human Papillomavirus (HPV): A Comprehensive Exploration of its Role in Cancer Progression and Global Health Challenges

HPV represents a large group of double stranded DNA viruses that are highly involved with different types of human cancers. This synopsis describes the complexities surrounding HPV virology, classifications, and genomic variation, especially focusing on high-risk strains such as HPV16 and HPV18, the main causative factors for cervical cancers. The International Committee on Taxonomy of Viruses specifies more than 200 HPV types each associated with a respective disease and indicated in Table 1. HPV spread is mostly due to direct skin-to-skin contact between individuals’ sex organs causing infections on the mucous membrane and keratinized epithelial cells. Although majority of the infections are asymptomatic, some chronic HRHPV infections may progress into cancers because of oncoproteins E6 and E7. The high-risk variants of HPV lead to cervical, anal, and oropharyngeal cancers whereas the low-risk types cause harmless genital warts. While integrating HPV DNA into the host genome, orchestrated by oncoproteins E6 and E7 disrupts the cell regulatory mechanism; this leads to abnormal control over cell multiplication–one of the major elements of the process that develops to HPV induced cancer. A classic case is cervical cancer that has been extensively investigated as one of the highly documented HPV associated malignancies. Pap smears and HPV DNA tests are among the screening means that lower the incidents and deaths associated with cervical cancers. HPV-associated cancers of the head and neck, anus, penis, vulva, and vagina all show a characteristic profile in terms of the pathogen aetiology and risks involved. HPV-related head and neck cancers affect non-smokers and show good response to standard therapies. HPV poses increased anal cancer risk for immunocompromised individuals highlighting the complexity of interdependence of immunity and cancer development. Penile cancer results from poor hygiene and non-circumcision. Vulvar and virginal cancer mostly affects women, and the risk factors involve HPV infection and smoking. Therefore, various types of multidisciplinary approach that may include surgeries, radiotherapy, and chemotherapy are necessary to ensure proper treatment. Certain cancers are strongly associated with some high-risk HPV genotypes, such as HPV-16 and HPV-18; thus, vaccination is important. HPV infection outcomes are determined by the immune response as well as clearance of HPV infection. Screening and immunological understanding for early detection of HPV related health risks is fundamental. However, this encompassing review highlights the multi-dimensional impact of HPV encompassing virology of HPV, cancer specific presentation of HPV and control including prevention of HPV infection, screening, and research on cancer attributable by HPV and strategies towards mitigation of this global health problem.

Head-to-head immunogenicity comparison of an Escherichia coli-produced 9-valent human papillomavirus vaccine and Gardasil 9 in women aged 18-26 years in China: a randomised blinded clinical trial

BACKGROUND

An Escherichia coli-produced human papillomavirus (HPV) 16 and 18 bivalent vaccine (Cecolin) was prequalified by WHO in 2021. This study aimed to compare the immunogenicity of the E coli-produced HPV 9-valent vaccine Cecolin 9 (against HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58) with Gardasil 9.

METHODS

This was a randomised, single-blind trial conducted in China. Healthy non-pregnant women aged 18-26 years, who were not breastfeeding and with no HPV vaccination history, were enrolled in the Ganyu Centre for Disease Control and Prevention (Lianyungang City, Jiangsu Province, China). Women were stratified by age (18-22 years and 23-26 years) and randomly assigned (1:1) using a permutated block size of eight to receive three doses of Cecolin 9 or Gardasil 9 at day 0, day 45, and month 6. All participants, as well as study personnel without access to the vaccines, were masked. Neutralising antibodies were measured by a triple-colour pseudovirion-based neutralisation assay. The primary outcomes, seroconversion rates and geometric mean concentrations (GMCs) at month 7, were analysed in the per-protocol set for immunogenicity (PPS-I). Non-inferiority was identified for the lower limit of the 95% CI of the GMC ratio (Cecolin 9 vs Gardasil 9) at a margin of 0·5 and a seroconversion rate difference (Cecolin 9-Gardasil 9) at a margin of -5%. This study was registered at ClinicalTrials.gov (NCT04782895) and is completed.

FINDINGS

From March 14 to 18, 2021, a total of 553 potential participants were screened, of which 244 received at least one dose of Cecolin 9 and 243 received at least one dose of Gardasil 9. The seroconversion rates for all HPV types in both groups were 100% in the PPS-I, with the values of the lower limits of 95% CIs for seroconversion rate differences ranging between -1·8% and -1·7%. The GMC ratios of five types were higher than 1·0, with the highest ratio, for HPV 58, at 1·65 (95% CI 1·38-1·97), and those of four types were lower than 1·0, with the lowest ratio, for HPV 11, at 0·79 (0·68-0·93). The incidence of adverse reactions in both groups was similar (43% [104/244] vs 47% [115/243]).

INTERPRETATION

Cecolin 9 induced non-inferior HPV type-specific immune responses compared with Gardasil 9 and is a potential candidate to accelerate the elimination of cervical cancer by allowing for global accessibility to 9-valent HPV vaccinations, especially in low-income and middle-income countries.

FUNDING

National Natural Science Foundation, Fujian Provincial Natural Science Foundation, Xiamen Science and Technology Plan Project, Fundamental Research Funds for the Central Universities, CAMS Innovation Fund for Medical Sciences of China, and Xiamen Innovax.

Immunogenicity and safety of an Escherichia coli-produced human papillomavirus (types 6/11/16/18/31/33/45/52/58) L1 virus-like-particle vaccine: a phase 2 double-blind, randomized, controlled trial

The Escherichia coli-produced human papillomavirus (HPV) 16/18 bivalent vaccine (Cecolin) has received prequalification by the World Health Organization based on its high efficacy and good safety profile. We aimed to evaluate the immunogenicity and safety of the second-generation nonavalent HPV 6/11/16/18/31/33/45/52/58 vaccine (Cecolin 9) through the randomized, blinded phase 2 clinical trial. Eligible healthy women aged 18-45 years were randomly (1:1) allocated to receive three doses of 1.0 mL (270 µg) of Cecolin 9 or placebo with a 0-1-6-month schedule. The primary endpoint was the seroconversion rate and geometric mean titer of neutralizing antibodies (nAbs) one month after the full vaccination course (month 7). The secondary endpoint was the safety profile including solicited adverse reactions occurring within 7 d, adverse events (AEs) occurring within 30 d after each dose, and serious adverse events (SAEs) occurring during the 7-month follow-up period. In total, 627 volunteers were enrolled and randomly assigned to Cecolin 9 (n = 313) or placebo (n = 314) group in Jiangsu Province, China. Almost all participants in the per-protocol set for immunogenicity (PPS-I) seroconverted for nAbs against all the nine HPV types at month 7, while two failed to seroconvert for HPV 11 and one did not seroconvert for HPV 52. The incidence rates of total AEs in the Cecolin 9 and placebo groups were 80.8% and 72.9%, respectively, with the majority of them being mild and recovering shortly. None of the SAEs were considered related to vaccination. In conclusion, the E. coli-produced 9-valent HPV (9vHPV) vaccine candidate was well tolerated and immunogenic, which warrants further efficacy studies in larger populations.

Polyfunctional antibodies: a path towards precision vaccines for vulnerable populations

Vaccine efficacy determined within the controlled environment of a clinical trial is usually substantially greater than real-world vaccine effectiveness. Typically, this results from reduced protection of immunologically vulnerable populations, such as children, elderly individuals and people with chronic comorbidities. Consequently, these high-risk groups are frequently recommended tailored immunisation schedules to boost responses. In addition, diverse groups of healthy adults may also be variably protected by the same vaccine regimen. Current population-based vaccination strategies that consider basic clinical parameters offer a glimpse into what may be achievable if more nuanced aspects of the immune response are considered in vaccine design. To date, vaccine development has been largely empirical. However, next-generation approaches require more rational strategies. We foresee a generation of precision vaccines that consider the mechanistic basis of vaccine response variations associated with both immunogenetic and baseline health differences. Recent efforts have highlighted the importance of balanced and diverse extra-neutralising antibody functions for vaccine-induced protection. However, in immunologically vulnerable populations, significant modulation of polyfunctional antibody responses that mediate both neutralisation and effector functions has been observed. Here, we review the current understanding of key genetic and inflammatory modulators of antibody polyfunctionality that affect vaccination outcomes and consider how this knowledge may be harnessed to tailor vaccine design for improved public health.

Human Papillomavirus Epidemiology and Prevention: Is There Still a Gender Gap?

BACKGROUND AND AIM

Human papillomavirus (HPV) is sexually transmitted, one of the three most common sexually transmitted infections (STIs) in both males and females, and the most common viral STI. A crucial public health strategy to protect people against HPV is vaccination, which has shown its effectiveness in preventing HPV-related diseases. Presently, three types of vaccines are available (bivalent, quadrivalent, and nonvalent), and they all target the two most oncogenic virus genotypes (HPV 16 and 18). In recent years, the need to implement vaccination programmes that include all genders has been discussed in order to achieve herd immunity against HPV. To date, only a few countries have included young males in their vaccination programmes. Thus, our objective with this review is to provide an overview of the epidemiology of HPV and HPV prevention strategies and report the latest findings from the scientific literature.