Live, Attenuated Influenza A H5N1 Candidate Vaccines Provide Broad Cross-Protection in Mice and Ferrets

Abstract

BackgroundRecent outbreaks of highly pathogenic influenza A H5N1 viruses in humans and avian species that began in Asia and have spread to other continents underscore an urgent need to develop vaccines that would protect the human population in the event of a pandemic.Methods and FindingsLive, attenuated candidate vaccines possessing genes encoding a modified H5 hemagglutinin (HA) and a wild-type (wt) N1 neuraminidase from influenza A H5N1 viruses isolated in Hong Kong and Vietnam in 1997, 2003, and 2004, and remaining gene segments derived from the cold-adapted (ca) influenza A vaccine donor strain, influenza A/Ann Arbor/6/60 ca (H2N2), were generated by reverse genetics. The H5N1 ca vaccine viruses required trypsin for efficient growth in vitro, as predicted by the modification engineered in the gene encoding the HA, and possessed the temperature-sensitive and attenuation phenotypes specified by the internal protein genes of the ca vaccine donor strain. More importantly, the candidate vaccines were immunogenic in mice. Four weeks after receiving a single dose of 106 50% tissue culture infectious doses of intranasally administered vaccines, mice were fully protected from lethality following challenge with homologous and antigenically distinct heterologous wt H5N1 viruses from different genetic sublineages (clades 1, 2, and 3) that were isolated in Asia between 1997 and 2005. Four weeks after receiving two doses of the vaccines, mice and ferrets were fully protected against pulmonary replication of homologous and heterologous wt H5N1 viruses.ConclusionsThe promising findings in these preclinical studies of safety, immunogenicity, and efficacy of the H5N1 ca vaccines against antigenically diverse H5N1 vaccines provide support for their careful evaluation in Phase 1 clinical trials in humans.

Cell culture (Vero) derived whole virus (H5N1) vaccine based on wild-type virus strain induces cross-protective immune responses

“…Using live, attenuated influenza H5N1 candidate vaccines broad cross-protection in mice and ferrets could be demonstrated. Mice were protected following challenge with H5N1 viruses from clades 1, 2 and 3 [34]. Our studies demonstrate full protection against the homologous strain challenge at doses as low as 30 ng HA with the VN1203 clade 1 vaccine using a two dose regimen in CD1 mice.…”

Reverse genetic platform for inactivated and live-attenuated influenza vaccine

“…In part of testing the utility of the present reverse genetic system and its practical application for vaccine production, we generated rgX-31ca-ΔH5N1 and rgX-31ca-H9N2 reassortant viruses that have 6 internal genes of X-31ca and the two haemagglutinin and neuraminidase surface antigens derived from A/ Chicken/Korea/MS96/96 and A/Indonesia/5/2005. Highly pathogenic H5N1 viruses carry multi-basic amino acids at the cleavage site of haemagglutinin gene (Cinatl et al, 2007), and the deletion of the amino acids usually leads to attenuation of virulence (Suguitan et al, 2006). For this purpose, we removed the multi-basic amino acids of haemagglutinin gene at the cleavage site of A/Indonesia/5/ 2005 (PQRESRRKKRG→PQREKRG).…”

Response of BALB/c mice to a monovalent influenza A (H1N1) 2009 split vaccine

“…10 Briefly, Madin-Darby canine kidney (MDCK) cells were seeded at 1310 6 cells/well in 96-well plates and cultured at 37 uC to form a monolayer. Serial twofold dilutions of heatinactivated (56 uC for 45 min) sera were then mixed separately with 100 TCID 50 of the H1N1 strain and incubated at room temperature for 1 h. Next, the mixture was added to a monolayer of MDCK cells in triplicate.…”