RESUMEN
To examine the effects of the NS1 and NEP genes of avian influenza viruses (AIVs) on pathogenicity in mice, we generated recombinant PR8 viruses containing 3 different NS genes of AIVs. In contrast to the reverse genetics-generated PR8 (rPR8) strain and other recombinant viruses, the recombinant virus rPR8-NS(0028), which contained the NS gene of A/chicken/KBNP-0028/2000 (H9N2) (0028), was non-pathogenic to mice. The novel single mutations of 0028 NS1 to corresponding amino acid of PR8 NS1, G139D and S151T increased the pathogenicity of rPR8-NS(0028). The replacement of the PL motifs (EPEV or RSEV) of pathogenic recombinant viruses with that of 0028 (GSEV) did not reduce the pathogenicity of the viruses. However, a recombinant virus with an EPEV-grafted 0028 NS gene was more pathogenic than rPR8-NS(0028) but less than rPR8. The lower pathogenicity of rPR8-NS(0028) might be associated with the lower virus titer and IFN-ß level in the lungs of infected mice, and be attributed to G139, S151 and GSEV-PL motif of NS1 gene of 0028. In conclusion we defined new amino acid residues of NS1 related to mice pathogenicity and the presence of pathogenic NS genes among low pathogenic AIVs may encourage continuous monitoring of their mammalian pathogenicity.
Asunto(s)
Pollos/virología , Subtipo H9N2 del Virus de la Influenza A/genética , Subtipo H9N2 del Virus de la Influenza A/patogenicidad , Gripe Aviar/virología , Proteínas no Estructurales Virales/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Femenino , Gripe Aviar/inmunología , Interferón beta/metabolismo , Pulmón/virología , Ratones , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Mutación , Filogenia , Análisis de Secuencia de ADN , Carga Viral , VirulenciaRESUMEN
We generated reassorted PR8 viruses containing six different combinations of avian influenza virus (AIV) polymerase genes from A/chicken/Korea/01310/2001 (H9N2) (01310) and A/chicken/Korea/KBNP-0028/2000 (H9N2) (0028) to examine the effects of the AIV polymerase genes PB1, PB2, and PA on replication efficiency in different host cells and pathogenicity in mice. The virus titers of the reassorted viruses possessing 01310 [rPR8-PB2(01310)] and 0028 [rPR8-PB2(0028)] PB2 genes were significantly higher than those of the others except the rPR8 virus in embryonated chicken eggs at 37°C, and those of avian polymerase reassorted viruses were significantly less than rPR8 in MDCK cells at 32 and 37°C. rPR8-PB2(01310), rPR8-PB2(0028), and rPR8-PA(0028) caused no body weight loss in BALB/c mice but rPR8-PA(01310), rPR8-PB1(01310), and rPR8-PB1(0028) caused mortality and significantly different body weight loss compared to those in the mock treatment. In contrast to rPR8-PB2(0028) and rPR8-PA(0028), rPR8-PB2(01310) was not isolated from infected mice, and rPR8-PB1(0028) was less pathogenic than rPR8-PB1(01310). We determined the amino acid residues that were specific to the less pathogenic polymerases. A comparison with those of pandemic 2009 H1N1, human fatal H5N1 and H7N9, and pathogenic AIVs to mice without adaptation revealed that they possessed the mammalian pathogenic constellation of polymerases. Thus, the novel polymerase genes and amino acid residues may be useful to understand the host-barrier overcome of AIVs in mice and to develop safer and efficacious vaccines.