ABSTRACT
The highly pathogenic avian influenza (HPAI) H5N1 virus remains to be one of the world's largest pandemic threats due to the emergence of new variants. The rapid evolution of new sub-lineages is currently the greatest challenge in vaccine development. In this study, we developed an epitope modified non-pathogenic H5N3 (A/duck/Singapore/97) vaccine for broad protection against influenza H5 subtype. H5N3 hemagglutinin (HA) mutant reassortant viruses with A/Puerto Rico/8/34 (PR8) backbone were generated by mutating amino acids at the 140th loop and 190th α-helix of hemagglutinin. The cross-neutralizing efficacy of reverse genetics-derived H5N3HA (RG-H5N3HA) mutants was confirmed by testing reactivity with reference chicken anti-H5N1 clade 2 virus sera. Furthermore, RG-H5N3HA mutant immunized mice induced cross-neutralizing antibodies and cross-protection against distinct H5N1 viral infection. Our findings suggest that the use of non-pathogenic H5 viruses antigenically related to HPAI-H5N1 allows for the development of broadly protective vaccines and reduces the need for biosafety level 3 (BSL3) containment facilities.
Subject(s)
Cross Protection/immunology , Epitopes/genetics , Epitopes/immunology , Immunogenicity, Vaccine/immunology , Influenza A Virus, H5N1 Subtype/immunology , Influenza Vaccines/immunology , Influenza in Birds/immunology , Amino Acid Substitution , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Chickens , Dogs , Female , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Hemagglutinin Glycoproteins, Influenza Virus/immunology , Influenza Vaccines/administration & dosage , Influenza in Birds/prevention & control , Influenza in Birds/virology , Alphainfluenzavirus/classification , Alphainfluenzavirus/immunology , Madin Darby Canine Kidney Cells , Mice , Mice, Inbred BALB C , Reassortant Viruses/genetics , Reassortant Viruses/immunology , Vaccines, Inactivated/administration & dosage , Vaccines, Inactivated/immunologyABSTRACT
H5N1 HPAI virus continues to be a severe threat for public health, as well as for the poultry industry, due to its high mortality and antigenic drift rate. There is no monovalent vaccine available which provides broad protection against those major circulating strains. In the present study, a monovalent H5 vaccine strain was developed with antigenic sequence analysis and epitope mutations. H5 from Indonesia strain (A/Indonesia/CDC669/2006) was used as backbone sequence. Three amino acids were mutated to express immunogenic epitopes from other circulating H5N1s in the backbone. RG influenza virus expressing the epitope-chimeric H5 can react in HI with multiple H5 monoclonal antibodies which fail to neutralize wild type CDC669. High titers in HI and virus neutralization against different clades H5N1s (clade 1, 2, 4 and 7) were detected using sera from mice immunized with the epitope-chimeric H5N1. The monovalent vaccine with RG-epitope-chimeric H5N1 protected mice from lethal challenge with H5N1s of different clades, including clade 1.0, 2.1, 2.2 and 2.3. This study indicates that the broad immune response elicited by this single H5N1 virus allows it to be a promising candidate for a monovalent H5 universal vaccine.
Subject(s)
Cross Protection , Epitopes/immunology , Hemagglutinin Glycoproteins, Influenza Virus/immunology , Influenza A Virus, H5N1 Subtype/immunology , Influenza Vaccines/immunology , Orthomyxoviridae Infections/prevention & control , Animals , Antibodies, Neutralizing/blood , Antibodies, Neutralizing/immunology , Antibodies, Viral/blood , Antibodies, Viral/immunology , Disease Models, Animal , Epitopes/genetics , Female , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Influenza A Virus, H5N1 Subtype/genetics , Influenza Vaccines/administration & dosage , Influenza Vaccines/genetics , Mice, Inbred BALB C , Orthomyxoviridae Infections/immunology , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Survival Analysis , Vaccines, Subunit/administration & dosage , Vaccines, Subunit/genetics , Vaccines, Subunit/immunology , Vaccines, Synthetic/administration & dosage , Vaccines, Synthetic/genetics , Vaccines, Synthetic/immunologyABSTRACT
BACKGROUND: Avian influenza A H7N7 virus poses a pandemic threat to human health because of its ability for direct transmission from domestic poultry to humans and from human to human. The wide zoonotic potential of H7N7 combined with an antiviral immunity inhibition similar to pandemic 1918 H1N1 and 2009 H1N1 influenza viruses is disconcerting and increases the risk of a putative H7N7 pandemic in the future, underlining the urgent need for vaccine development against this virus. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we developed a recombinant vaccine by expressing the H7N7-HA protein on the surface of baculovirus (Bac-HA). The protective efficacy of the live Bac-HA vaccine construct was evaluated in a mouse model by challenging mice immunized intranasally (i.n.) or subcutaneously (s.c.) with high pathogenic mouse adapted H7N7 reassorted strain. Although s.c. injection of live Bac-HA induced higher specific IgG than i.n. immunization, the later resulted in an elevated neutralization titer. Interestingly, 100% protection from the lethal viral challenge was only observed for the mice immunized intranasally with live Bac-HA, whereas no protection was achieved in any other s.c. or i.n. immunized mice groups. In addition, we also observed higher mucosal IgA as well as increased IFN-γ and IL-4 responses in the splenocytes of the surviving mice coupled with a reduced viral titer and diminished histopathological signs in the lungs. CONCLUSION: Our results indicated that protection from high pathogenic H7N7 (NL/219/03) virus requires both mucosal and systemic immune responses in mice. The balance between Th1 and Th2 cytokines is also required for the protection against the H7N7 pathogen. Intranasal administration of live Bac-HA induced all these immune responses and protected the mice from lethal viral challenge. Therefore, live Bac-HA is an effective vaccine candidate against H7N7 viral infections.
