Martine Wettendorff

Cross-Protection against Lethal H5N1 Challenge in Ferrets with an Adjuvanted Pandemic Influenza Vaccine

Background Unprecedented spread between birds and mammals of highly pathogenic avian influenza viruses (HPAI) of the H5N1 subtype has resulted in hundreds of human infections with a high fatality rate. This has highlighted the urgent need for the development of H5N1 vaccines that can be produced rapidly and in sufficient quantities. Potential pandemic inactivated vaccines will ideally induce substantial intra-subtypic cross-protection in humans to warrant the option of use, either prior to or just after the start of a pandemic outbreak. In the present study, we evaluated a split H5N1 A/H5N1/Vietnam/1194/04, clade 1 candidate vaccine, adjuvanted with a proprietary oil-in- water emulsion based Adjuvant System proven to be well-tolerated and highly immunogenic in the human (Leroux-Roels et al. (2007) The Lancet 370:580–589), for its ability to induce intra-subtypic cross-protection against clade 2 H5N1/A/Indonesia/5/05 challenge in ferrets. Methodology and Principal Findings All ferrets in control groups receiving non-adjuvanted vaccine or adjuvant alone failed to develop specific or cross-reactive neutralizing antibodies and all died or had to be euthanized within four days of virus challenge. Two doses of adjuvanted split H5N1 vaccine containing ≥1.7 µg HA induced neutralizing antibodies in the majority of ferrets to both clade 1 (17/23 (74%) responders) and clade 2 viruses (14/23 (61%) responders), and 96% (22/23) of vaccinees survived the lethal challenge. Furthermore lung virus loads and viral shedding in the upper respiratory tract were reduced in vaccinated animals relative to controls suggesting that vaccination might also confer a reduced risk of viral transmission. Conclusion These protection data in a stringent challenge model in association with an excellent clinical profile highlight the potential of this adjuvanted H5N1 candidate vaccine as an effective tool in pandemic preparedness.

Correlation between direct ELISA, single epitope-based inhibition ELISA and Pseudovirion-based neutralization assay for measuring anti-HPV-16 and anti-HPV-18 antibody response after vaccination with the AS04-adjuvanted HPV-16/18 cervical cancer vaccine

To monitor immune status during clinical trials and after vaccine registration, several assays have been developed to measure type-specific human papillomavirus (HPV) serum antibody levels. These include neutralization assays, single epitope-based inhibition immunoassays, and direct enzyme-linked immunosorbent assays (ELISAs). Neutralization assays based on multiple epitopes and independent of vaccine material are considered the ‘gold standard’ for unbiased assessment of the protective potential of vaccine-induced antibodies. However, their use in large clinical trials is challenging. Here, we compare both the direct ELISA and the single epitope-based inhibition ELISA with the pseudovirion-based neutralization assay (PBNA) for HPV-16/18 antibody responses in vaccinated women enrolled in trials of Cervarix™, GSKs cervical cancer vaccine. The direct ELISA, which is based on multiple epitopes, was shown to have a higher degree of sensitivity and correlation with the PBNA when compared with the single epitope-based inhibition ELISA. Among double-positive results, high correlations were observed between the PBNA and the direct ELISA (0.70-0.88 for HPV-16 and 0.82-0.94 for HPV-18) and also with the single epitope-based inhibition ELISA (0.60-0.89 for HPV-16 and 0.57-0.96 for HPV-18) in women aged 15-25 years. The correlation persisted up to 6.4 years after primary vaccination. Similar levels of correlation were observed for adolescents aged 10-14 years and women aged 46-55 years. Therefore, the direct ELISA appears to be an excellent surrogate for neutralizing activity and can be used to evaluate antibody response induced by L1 VLP-based cervical cancer vaccines, regardless of time elapsed after vaccination (up to 6.4 years) and the age of the vaccine recipient.

Randomized controlled trial of an adjuvanted human papillomavirus (HPV) type 6 L2E7 vaccine: infection of external anogenital warts with multiple HPV types and failure of therapeutic vaccination.

BACKGROUND Cellular immunity is involved in spontaneous clearance of anogenital warts caused, most typically, by human papillomavirus (HPV) type 6 or 11, supporting the concept of therapeutic vaccination. A therapeutic vaccine composed of HPV-6 L2E7 fusion protein and AS02A adjuvant was evaluated in conjunction with conventional therapies in subjects with anogenital warts. METHODS A total of 457 subjects with anogenital warts were screened, of which 320 with HPV-6 and/or HPV-11 infection were enrolled into 2 double-blind, placebo-controlled substudies. Three doses of vaccine or placebo were administered along with either ablative therapy or podophyllotoxin. RESULTS Although a positive trend toward clearance was seen in patients infected with only HPV-6, in neither substudy did the vaccine significantly increase the efficacy of conventional therapies, despite induction of adequate immune responses. Extensive HPV typing by polymerase chain reaction demonstrated that a majority of screened subjects (73.7%) were infected with HPV-6 and/or HPV-11 and that a large proportion (40.1%) were infected with multiple HPV types. HPV types that put subjects at high risk of development of cervical cancer were detected in 39.8% of subjects. CONCLUSIONS Infection with multiple HPV types, including high-risk types, is common in anogenital wart disease. Therapeutic vaccination failed to increase the efficacy of conventional therapies.

Development of an AS04-Adjuvanted HPV Vaccine with the Adjuvant System Approach

A novel human papillomavirus (HPV) vaccine has been formulated with virus-like particles of the L1 protein of HPV-16 and HPV-18, and the Adjuvant System 04 (AS04). AS04 is a combination of the toll-like receptor 4 agonist monophosphoryl lipid A (MPL) and aluminum hydroxide. The AS04-adjuvanted HPV vaccine induces a high and sustained immune response against HPV, including high levels of neutralizing antibodies at the cervical mucosa in women aged 15–55 years. Recently, the mechanism of action of AS04 has been evaluated in vitro in human cells and in vivo in mice and the data provide evidence for the molecular and cellular basis of the observed immunogenicity, efficacy, and safety profile of this formulation.In this review, we discuss how the results of GlaxoSmithKline’s clinical studies on immunogenicity, protection, and reactogenicity with the AS04-adjuvanted HPV vaccine are supported by the observed mechanism of action for the adjuvant.The adjuvant activity of AS04, as measured by enhanced antibody response to HPV antigens, was found to be strictly dependent on AS04 and the HPV antigens being injected at the same intramuscular site within 24 hours of each other. The addition of MPL to aluminum salt enhances humoral and cell-mediated response by rapidly triggering a local and transient cytokine response that leads to an increased activation of antigen-presenting cells and results in an improved presentation of antigen to CD4+ T cells.The added value of MPL in AS04 for an HPV vaccine was demonstrated in clinical studies by high vaccine-elicited antibody responses and the induction of high levels of memory B cells. The vaccine elicits cross protection against some other oncogenic HPV types (specifically HPV-31, -33, and -45) not contained in the vaccine. The localized and transient nature of the innate immune response supports the acceptable safety profile observed in clinical studies.

Role of AS04 in human papillomavirus vaccine: mode of action and clinical profile

Introduction: Understanding the mode of action of adjuvants is important for the interpretation of clinical studies. Areas covered: This paper discusses how the results of GSKs clinical studies with an AS04-adjuvanted human papillomavirus (HPV) vaccine are supported by the mode of action of AS04. AS04 and antigens must be injected at the same intramuscular site together or within 24 h of each other. AS04 induces local cytokine production leading to increased recruitment of dendritic cells and monocytes and raised numbers of antigen presenting cells in the draining lymph node. The localized and transient nature of the innate immune response supports the acceptable safety profile observed in clinical studies. The readers will gain a comprehensive understanding of the mode of action of AS04 and how it relates to results of clinical studies. Expert opinion: The AS04-adjuvanted HPV vaccine has an acceptable safety profile and induces an enhanced and sustained immune response and high protection against HPV types 16/18. Cross-protection against oncogenic HPV types 31/33/45 not contained in the vaccine is also observed. The mode of action of AS04 supports the clinical profile of the AS04-adjuvanted HPV vaccine.

10 – Development and evaluation of AS04, a novel and improved adjuvant system containing MPL and aluminum salt

Publisher Summary Vaccines represent one of the safest and most cost-saving medical products that have ever been developed for healthcare. They have allowed the eradication of an infectious disease, smallpox, and dramatically reduced morbidity and mortality due to other infectious diseases over the past two centuries. Until recently, aluminum salts are the only adjuvants approved for use in humans. Adjuvants based on aluminum hydroxide and aluminum phosphate are the most commonly used compounds and are recognized to enhance antibody response and to stimulate a type II cellular response. Particulate antigens are inherently more immunogenic than soluble molecules and facilitate antigen targeting and uptake by antigen-presenting cells (APC). The use of an adjuvant in vaccine formulations can facilitate the induction of humoral and cellular immune responses which are of more rapid onset, increased magnitude, and prolonged duration compared with the unadjuvanted antigen. While aluminum salts are known to improve humoral immune responses, monophosphoryl lipid (MPL) is considered to foster Thl-type cellular immunity, and a combination of both potentially enhances both cellular and humoral immune response, depending on the vaccine antigen.

Glycoprotein B (gB) vaccines adjuvanted with AS01 or AS02 protect female guinea pigs against cytomegalovirus (CMV) viremia and offspring mortality in a CMV-challenge model

The transmission of cytomegalovirus (CMV) from mother to fetus can give rise to severe neurodevelopment defects in newborns. One strategy to prevent these congenital defects is prophylactic vaccination in young women. A candidate vaccine antigen is glycoprotein B (gB). This antigen is abundant on the virion surface and is a major target of neutralization responses in human infections. Here, we have evaluated in a challenge model of congenital guinea pig CMV (GPCMV) infection, GPCMV-gB vaccines formulated with the clinically relevant Adjuvant Systems AS01B and AS02V, or with Freunds adjuvant (FA). Fifty-two GPCMV-seronegative female guinea pigs were administered three vaccine doses before being mated. GPCMV-challenge was performed at Day 45 of pregnancy (of an estimated 65 day gestation). Pup mortality rates in the gB/AS01B, gB/AS02V, and gB/FA groups were 24% (8/34), 10% (4/39) and 36% (12/33), respectively, and in the unvaccinated control group was 65% (37/57). Hence, efficacies against pup mortality were estimated at 64%, 84% and 44% for gB/AS01B (p<0.001), gB/AS02V (p<0.001) and gB/FA (p=0.014), respectively. Efficacies against GPCMV viremia (i.e. DNAemia, detected by PCR) were estimated at 88%, 68% and 25% for the same vaccines, respectively, but were only significant for gB/AS01B (p<0.001), and gB/AS02V (p=0.002). In dams with viremia, viral load was approximately 6-fold lower with vaccination than without. All vaccines were highly immunogenic after two and three doses. In light of these results and of other results of AS01-adjuvanted vaccines in clinical development, vaccine immunogenicity was further explored using human CMV-derived gB antigen adjuvanted with either AS01B or the related formulation AS01E. Both adjuvanted vaccines were highly immunogenic after two doses, in contrast to the lower immunogenicity of the unadjuvanted vaccine. In conclusion, the protective efficacy and immunogenicity of adjuvanted vaccines in this guinea pig model are supportive of investigating gB/AS01 and gB/AS02 in the clinic.

Narcolepsy and A(H1N1)pdm09 vaccination: Shaping the research on the observed signal

Epidemiological data from several European countries suggested an increased risk of the chronic sleep disorder narcolepsy following vaccination with Pandemrix™, an AS03-adjuvanted, pandemic A(H1N1)pdm09 influenza vaccine. Further research to investigate potential associations between Pandemrix™ vaccination, A(H1N1)pdm09 influenza infection and narcolepsy is required. Narcolepsy is most commonly caused by a reduction or absence of hypocretin produced by hypocretin-secreting neurons in the hypothalamus, and is tightly associated with HLA-II DQB1*06:02. Consequently, research focusing on CD4+ T-cell responses, building on the hypothesis that for disease development, T cells specific for antigen(s) from hypocretin neurons must be activated or reactivated, is considered essential. Therefore, the following key areas of research can be identified, (1) characterization of hypothetical narcolepsy-specific auto-immune CD4+ T cells, (2) mapping epitopes of such T cells, and (3) evaluating potential mechanisms that would enable such cells to gain access to the hypothalamus. Addressing these questions could further our understanding of the potential links between narcolepsy and A(H1N1)pdm09 vaccination and/or infection. Of particular interest is that any evidence of a mimicry-based mechanism could also explain the association between narcolepsy and A(H1N1)pdm09 influenza infection.

Seeking Help: B Cells Adapting to Flu Variability

CD4 T cell help, potentially driven by adjuvantation, increases B cell adaptability by driving the plasticity and evolution of B cells and, consequently, the antibody response to influenza antigens. The study of influenza vaccines has revealed potential interactions between preexisting immunological memory and antigenic context and/or adjuvantation. In the face of antigenic diversity, the process of generating B cell adaptability is driven by cross-reactive CD4 memory cells, such as T follicular helper cells from previous infections or vaccinations. Although such “helped” B cells are capable of adapting to variant antigens, lack of CD4 help could lead to a suboptimal antibody response. Collectively, this indicates an interplay between CD4 T cells, adjuvant, and B cell adaptability.