Evaluation of live avian-human reassortant influenza A H3N2 and H1N1 virus vaccines in seronegative adult volunteers.
An avian-human reassortant influenza A virus deriving its genes coding for the hemagglutinin and neuraminidase from the human influenza A/Washington/897/80 (H3N2) virus and its six "internal" genes from the avian influenza A/Mallard/NY/6750/78 (H2N2) virus (i.e., a six-gene reassortant) was previously shown to be safe, infectious, nontransmissible, and immunogenic as a live virus vaccine in adult humans. Two additional six-gene avian-human reassortant influenza viruses derived from the mating of wild-type human influenza A/California/10/78 (H1N1) and A/Korea/1/82 (H3N2) viruses with the avian influenza A/Mallard/NY/78 virus were evaluated in seronegative (hemagglutination inhibition titer, less than or equal to 1:8) adult volunteers for safety, infectivity, and immunogenicity to determine whether human influenza A viruses can be reproducibly attenuated by the transfer of the six internal genes of the avian influenza A/Mallard/NY/78 virus. The 50% human infectious dose was 10(4.9) 50% tissue culture infectious doses for the H1N1 reassortant virus and 10(5.4) 50% tissue culture infectious doses for the H3N2 reassortant virus. Both reassortants were satisfactorily attenuated with only 5% (H1N1) and 2% (H3N2) of infected vaccines receiving less than 400 50% human infectious doses developing illness. Consistent with this level of attenuation, the magnitude of viral shedding after inoculation was reduced 100-fold (H1N1) to 10,000-fold (H3N2) compared with that produced by wild-type virus. The duration of virus shedding by vaccines was one-third that of controls receiving wild-type virus. At 40 to 100 50% human infectious doses, virus-specific immune responses were seen in 77 to 93% of volunteers. When vaccinees who has received 10(7.5) 50% tissue culture infectious doses of the H3N2 vaccine were experimentally challenged with a homologous wild-type human virus only 2 of 19 (11%) vaccinees became ill compared with 7 of 14 (50%) unvaccinated seronegative controls ( P < 0.025; protective efficacy, 79%). Thus, three different virulent human influenza A viruses have been satisfactorily attenuated by the acquisition of the six internal genes of the avian influenza A/Mallard/NY/78 virus. The observation that this donor virus can reproducibly attenuate human influenza A viruses indicates that avian-human influenza A reassortants should be further studied as potential live influenza A virus vaccines.
Snyder
M H
MH
Clements
M L
ML
Betts
R F
RF
Dolin
R
R
Buckler-White
A J
AJ
Tierney
E L
EL
Murphy
B R
BR
D000328:Adult; D000914:Antibodies, Viral / Q000096:biosynthesis; D006389:Hemagglutinins, Viral / Q000276:immunology*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D009980:Influenza A virus / Q000254:growth & development / Q000276:immunology*; D009439:Neuraminidase / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*; D014779:Virus Replication
D000914:Antibodies, Viral; D006389:Hemagglutinins, Viral; D014765:Viral Vaccines; D009439:Neuraminidase