Genetic characteristics of 2009 pandemic H1N1 influenza a viruses isolated from Mainland China

Antiviral and anti-inflammatory activity of arbidol hydrochloride in influenza A (H1N1) virus infection

AIM

To investigate the effects of arbidol hydrochloride (ARB), a widely used antiviral agent, on the inflammation induced by influenza virus.

METHODS

MDCK cells were infected with seasonal influenza A/FM/1/47 (H1N1) or pandemic influenza A/Hubei/71/2009 (H1N1). In vitro cytotoxicity and antiviral activity of ARB was determined using MTT assay. BALB/c mice were infected with A/FM/1/47 (H1N1). Four hours later the mice were administered ARB (45, 90, and 180 mg·kg(-1)·d(-1)) or the neuraminidase inhibitor oseltamivir (22.5 mg·kg(-1)·d(-1)) via oral gavage once a day for 5 d. Body-weight, median survival time, viral titer, and lung index of the mice were measured. The levels of inflammatory cytokines were examined using real-time RT-PCR and ELISA.

RESULTS

Both H1N1 stains were equally sensitive to ARB as tested in vitro. In the infected mice, ARB (90 and 180 mg·kg(-1)·d(-1)) significantly decreased the mortality, alleviated virus-induced lung lesions and viral titers. Furthermore, ARB suppressed the levels of IL-1β, IL-6, IL-12, and TNF-α, and elevated the level of IL-10 in the bronchoalveolar lavage fluids and lung tissues. However, ARB did not significantly affect the levels of IFN-α and IFN-γ, but reduced the level of IFN-β1 in lung tissues at 5 dpi. In peritoneal macrophages challenged with A/FM/1/47 (H1N1) or poly I:C, ARB (20 μmol/L) suppressed the levels of IL-1β, IL-6, IL-12, and TNF-α, and elevated the level of IL-10. Oseltamivir produced comparable alleviation of virus-induced lung lesions with more reduction in the viral titers, but less effective modulation of the inflammatory cytokines.

CONCLUSION

ARB efficiently inhibits both H1N1 stains and diminishes both viral replication and acute inflammation through modulating the expression of inflammatory cytokines.

Whole genome characterization, phylogenetic and genome signature analysis of human pandemic H1N1 virus in Thailand, 2009-2012

BACKGROUND

Three waves of human pandemic influenza occurred in Thailand in 2009-2012. The genome signature features and evolution of pH1N1 need to be characterized to elucidate the aspects responsible for the multiple waves of pandemic.

METHODOLOGY/FINDINGS

Forty whole genome sequences and 584 partial sequences of pH1N1 circulating in Thailand, divided into 1(st), 2(nd) and 3(rd) wave and post-pandemic were characterized and 77 genome signatures were analyzed. Phylogenetic trees of concatenated whole genome and HA gene sequences were constructed calculating substitution rate and d(N)/d(S) of each gene. Phylogenetic analysis showed a distinct pattern of pH1N1 circulation in Thailand, with the first two isolates from May, 2009 belonging to clade 5 while clades 5, 6 and 7 co-circulated during the first wave of pH1N1 pandemic in Thailand. Clade 8 predominated during the second wave and different proportions of the pH1N1 viruses circulating during the third wave and post pandemic period belonged to clades 8, 11.1 and 11.2. The mutation analysis of pH1N1 revealed many adaptive mutations which have become the signature of each clade and may be responsible for the multiple pandemic waves in Thailand, especially with regard to clades 11.1 and 11.2 as evidenced with V731I, G154D of PB1 gene, PA I330V, HA A214T S160G and S202T. The substitution rate of pH1N1 in Thailand ranged from 2.53×10(-3)±0.02 (M2 genes) to 5.27×10(-3)±0.03 per site per year (NA gene).

CONCLUSIONS

All results suggested that this virus is still adaptive, maybe to evade the host's immune response and tends to remain in the human host although the d(N)/d(S) were under purifying selection in all 8 genes. Due to the gradual evolution of pH1N1 in Thailand, continuous monitoring is essential for evaluation and surveillance to be prepared for and able to control future influenza activities.