RESUMO
Objective To investigate the effects of original antigenic sin caused by previous expo-sure to influenza A virus subtype H1N1 on the immune response to inactivated H5N1 vaccine. Methods In this study, the BALB/c mice were first infected with A/PR8 (H1N1) virus or immunized with inactivated vaccine to induce immune responses against the A/PR8 virus. Then they were injected once with inactivated H5N1 vaccine at dosages of 0. 01μg, 0. 1μg and 1μg, respectively. The levels of IgG and neutralizing an-tibodies in serum samples were detected after immunization. Four weeks after immunization, the mice were challenged with a lethal dose of H5N1 virus. Some indicators including the survival rate, body weight loss and residue virus titer in lung were recorded for further evaluation. Results The pre-existing anti-A/PR8 antibodies in mice didn′t alleviate the immune responses to inactivated H5N1 vaccine. Conclusion This study indicates that the original antigenic sin associated with the previous exposure to A/PR8 virus has no significant effect on the immune efficacy of H5N1 vaccine.
RESUMO
Highly Pathogenic Avian Influenza (HPAI) H5N1 virus is a threat to animal and public health worldwide. Till date, the H5N1 virus has claimed 402 human lives, with a mortality rate of 58% and has caused the death or culling of millions of poultry since 2003. In this study, we have designed three siRNAs (PB2-2235, PB2-479 and NP-865) targeting PB2 and NP genes of avian influenza virus and evaluated their potential, measured by hemagglutination (HA), plaque reduction and Real time RT-PCR assay, in inhibiting H5N1 virus (A/chicken/Navapur/7972/2006) replication in MDCK cells. The siRNAs caused 8- to 16-fold reduction in virus HA titers at 24 h after challenged with 100TCID50 of virus. Among these siRNAs, PB2-2235 offered the highest inhibition of virus replication with 16-fold reduction in virus HA titer, 80% reduction in viral plaque counts and 94% inhibition in expression of specific RNA at 24 h. The other two siRNAs had 68–73% and 87–88% reduction in viral plaque counts and RNA copy number, respectively. The effect of siRNA on H5N1 virus replication continued till 48h (maximum observation period). These findings suggest that PB2-2235 could efficiently inhibit HPAI H5N1 virus replication.
RESUMO
Objective: To study the anti-influenza A virus effect of theaflavin derivatives which contain theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3'-gallate (TF2B), and theaflavin-3, 3'-digallate (TF3) and to investigate the mechanism. Methods: The inhibition of theaflavin derivatives on A/Thailand/Kan353/2004 H5N1 pseudovirus was investigated using pseudotype H5N1 virus system. Hemagglutination inhibition assay and neuraminidase (NA) inhibition assay were used to investigate the mechanism for their anti-influenza activities. The inhibition of theaflavin derivatives on influenza A virus FM_1 was observed by H1N1 FM_1 system. Cytotoxicity of theaflavin derivatives on MDCK cells was determined by MTT assay. Results: Theaflavin derivatives could significantly inhibit the infection of pseudovirus H5N1 with IC50 of (151.88 ± 18.95) μg/mL. It had no inhibition on HA1 subunit. Theaflavin derivatives had the inhibition on NA with IC50 of (129.09 ± 1.33) μg/mL. Theaflavin derivatives showed a significant inhibitory activity on FM_1 influenza virus strain in MDCK cells. Theaflavin derivatives showed the low cytotoxicity on MDCK cells with CC50 of (879.89 ± 4.54) μg/mL. Conclusion: Theaflavin derivatives could inhibit the infection of avian influenza virus through the combination with hemagglutinin (HA) HA2 subunit and inhibit the activity of viral NA to some extent, which indicates that the anti-H5N1 avian influenza virus of theaflavin derivatives may be through multi-targets.