Benoît Baras

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.

A vaccine manufacturer’s approach to address medical needs related to seasonal and pandemic influenza viruses

Abstract Vaccination is considered to be one of the most effective tools to decrease morbidity as well as mortality caused by influenza viruses.

Pandemic H1N1 vaccine requires the use of an adjuvant to protect against challenge in naïve ferrets

In the context of an A/H1N1 influenza pandemic situation, this study demonstrates that heterologous vaccination with an AS03-adjuvanted 2008/2009 seasonal trivalent and pandemic H5N1 monovalent split vaccine conferred partial protection in influenza-naïve ferrets after challenge with the influenza pandemic H1N1 A/The Netherlands/602/09 virus. Further, unlike saline control and non-adjuvanted vaccine, it was shown that immunization of naïve ferrets with an AS03-adjuvanted pandemic H1N1 A/California/7/09 influenza split vaccine induced increased antibody response and enhanced protection against the challenge strain, including significant reduction in viral shedding in the upper respiratory tract and reduced lung pathology post-challenge. These results show the need for vaccination with the adjuvanted vaccine to fully protect against viral replication and influenza disease in unprimed ferrets.

Immunogenicity and Protective Efficacy in Mice and Hamsters of a β-Propiolactone Inactivated Whole Virus SARS-CoV Vaccine

The immunogenicity and efficacy of β-propiolactone (BPL) inactivated whole virion SARS-CoV (WI-SARS) vaccine was evaluated in BALB/c mice and golden Syrian hamsters. The vaccine preparation was tested with or without adjuvants. Adjuvant Systems AS01(B) and AS03(A) were selected and tested for their capacity to elicit high humoral and cellular immune responses to WI-SARS vaccine. We evaluated the effect of vaccine dose and each adjuvant on immunogenicity and efficacy in mice, and the effect of vaccine dose with or without the AS01(B) adjuvant on the immunogenicity and efficacy in hamsters. Efficacy was evaluated by challenge with wild-type virus at early and late time points (4 and 18 wk post-vaccination). A single dose of vaccine with or without adjuvant was poorly immunogenic in mice; a second dose resulted in a significant boost in antibody levels, even in the absence of adjuvant. The use of adjuvants resulted in higher antibody titers, with the AS01(B)-adjuvanted vaccine being slightly more immunogenic than the AS03(A)-adjuvanted vaccine. Two doses of WI-SARS with and without Adjuvant Systems were highly efficacious in mice. In hamsters, two doses of WI-SARS with and without AS01(B) were immunogenic, and two doses of 2 μg of WI-SARS with and without the adjuvant provided complete protection from early challenge. Although antibody titers had declined in all groups of vaccinated hamsters 18 wk after the second dose, the vaccinated hamsters were still partially protected from wild-type virus challenge. Vaccine with adjuvant provided better protection than non-adjuvanted WI-SARS vaccine at this later time point. Enhanced disease was not observed in the lungs or liver of hamsters following SARS-CoV challenge, regardless of the level of serum neutralizing antibodies.

Longevity of the protective immune response induced after vaccination with one or two doses of AS03A-adjuvanted split H5N1 vaccine in ferrets

It is crucial that a safe and effective pandemic vaccine be rapidly available to combat a new pandemic threat. In this study we investigated the magnitude and persistence of the protective efficacy induced by one or two doses (3.75 μg HA/dose) of AS03(A)-adjuvanted H5N1 A/Indonesia/5/05 split vaccine in a lethal ferret challenge model. All ferrets that received at least one dose of adjuvanted vaccine 4 weeks before homologous challenge survived and showed reduced or undetectable virus replication in the lungs and the upper airways. Ferrets receiving two doses of adjuvanted vaccine 19 and 16 weeks before the challenge also showed high level of protection from replication in the lungs and the upper airways, albeit with only 83% survival. Animals in the control groups (non-adjuvanted vaccine or saline) and animals immunized with one dose of adjuvanted vaccine administered 10 or 16 weeks before challenge showed only 17-33% survival rate after challenge. In conclusion, our observations support the possibility that a single dose of AS03(A)-adjuvanted H5N1 split vaccine can offer a rapid and short term but partial protection against disease. A second dose of the adjuvanted vaccine, which can be given with a flexible injection schedule, was shown to be essential to induce appreciable levels of antibodies and long-term protection.

AS03-adjuvanted H7N1 detergent-split virion vaccine is highly immunogenic in unprimed mice and induces cross-reactive antibodies to emerged H7N9 and additional H7 subtypes.

Avian H7 is one of several influenza A virus subtypes that have the potential to cause pandemics. Herein we describe preclinical results following administration of an investigational H7N1 inactivated detergent-split virion vaccine adjuvanted with the AS03 Adjuvant System. The adjuvanted H7N1 vaccine was highly immunogenic compared to the non-adjuvanted H7N1 vaccine in unprimed mice with less than 100ng of hemagglutinin antigen per dose. In addition, compared to the non-adjuvanted vaccine, the AS03-adjuvanted H7N1 vaccine also induced robust HI and VN antibody responses that cross-reacted with other H7 subtypes, including recently emerged H7N9 virus. These H7 data from the preclinical mouse model add to the existing H5 data to suggest that AS03 adjuvant technology may be generally effective for formulating antigen-sparing detergent-split virion vaccines against intrinsically sub-immunogenic avian influenza A virus subtypes.

Efficacy of an AS03A-adjuvanted split H5N1 influenza vaccine against an antigenically distinct low pathogenic H5N1 virus in pigs

We used the pig model of influenza to examine the efficacy of an AS03(A)-adjuvanted split H5N1 (A/Indonesia/05/2005) vaccine against challenge with a low pathogenic (LP) H5N1 avian influenza (AI) virus (duck/Minnesota/1525/1981) with only 85% amino acid homology in its HA1. Influenza seronegative pigs were vaccinated twice intramuscularly with adjuvanted vaccine at 3 antigen doses, unadjuvanted vaccine or placebo. All pigs were challenged 4 weeks after the second vaccination and euthanized 2 days later. After 2 vaccinations, all pigs in the adjuvanted vaccine groups had high hemagglutination inhibiting (HI) antibody titers to the vaccine strain (160-640), and lower antibody titers to the A/Vietnam/1194/04 H5N1 strain and to 2 LP H5 viruses with 90-91% amino acid homology to the vaccine strain (20-160). Eight out of 12 pigs had HI titers (10-20) to the challenge virus immediately before challenge. Neuraminidase inhibiting antibodies to the challenge virus were detected in most pigs (7/12) and virus neutralizing antibodies in all pigs. There was no antigen-dose dependent effect on the antibody response among the pigs immunized with adjuvanted H5N1 vaccines. After challenge, these pigs showed a complete clinical protection, reduced lung lesions and a significant protection against virus replication in the respiratory tract. Though the challenge virus showed only moderate replication efficiency in pigs, our study suggests that AS03(A)-adjuvanted H5N1 vaccine may confer a broader protection than generally assumed. The pros and cons of the pig as an H5N1 challenge model are also discussed.