RESUMEN
Studies carried out on cell permissivity are of great interest to understand virus replication and pathogenicity. We described the results of a comparative analysis of replication efficiency of two naturally occurring influenza A H9N2 variants isolated from poultry and wild birds, differing by only two substitutions Q226L and T384N, in the receptor-binding site of haemagglutinin and the 380 loop region of NA proteins, respectively. Considering the overall growth of both viruses, lung cultures ensured the most efficient growth of TUN12L226N384 strain with titres up to 10(9) TCID50/ml whereas small intestine culture was highly susceptible to the TUN51Q226T384 virus reaching a titre of 10(6) TCID50/ml. The lowest replication was shown in liver cells. The addition of trypsin was essential for the replication of either virus in primary fibroblasts, but it had a marginal positive effect on virus replication in the four other culture types with maximum titres of 10(8) TCID50/ml. This means that in chicken, the proteolytic activation of the H9N2 viruses with the cleavage motif RSSR may be mediated by other endoproteases than trypsin. Further investigations should concentrate on the production of the appropriate set of viruses by a reverse genetics approach and the examination of cellular protease expression in chicken tissues. This would lead to a more complete understanding of the tropism of low-pathogenic Influenza A viruses.
Asunto(s)
Pollos/virología , Subtipo H9N2 del Virus de la Influenza A/fisiología , Gripe Aviar/virología , Replicación Viral , Secuencias de Aminoácidos , Sustitución de Aminoácidos , Animales , Aves , Células Cultivadas , Embrión de Pollo , Femenino , Glicoproteínas Hemaglutininas del Virus de la Influenza/genética , Subtipo H9N2 del Virus de la Influenza A/patogenicidad , Mutación , Neuraminidasa/genética , Organismos Libres de Patógenos Específicos , TropismoRESUMEN
BACKGROUND: Among the surface antigens of Mycoplasma hominis, the P120' protein was previously shown to elicit a subtle antibody response and appears to be relatively conserved. To get better insight into the evolution of this protein, we analysed the genetic variability of its surface exposed region in 27 M. hominis isolates recovered from the genital tract of Tunisian patients with infertility disorders. METHODS: All specimens were processed for culture and PCR amplification of the N-terminal surface exposed region of p120' gene. PCR products were sequenced to evaluate the genetic variability, to test for adaptive selection, and to infer the phylogenetic relationship of the M. hominis isolates. RESULTS: Sequence analysis showed a total of 25 single nucleotide polymorphisms distributed through 23 polymorphic sites, yielding 13 haplotypes. All but one mutation were confined within three distinct regions. Analysis of the amino acid-based phylogenetic tree showed a predominant group of 17 closely related isolates while the remaining appear to have significantly diverged. CONCLUSION: By analysing a larger sample of M. hominis recovered from patients with urogenital infections, we show here that the P120' protein undergoes substantial level of genetic variability at its surface exposed region.