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Objective@#To isolate the cross-reactive antibodies against hemagglutinin of influenza virus and identify its biological function.@*Methods@#The antibodies gene reservoir of cross-reactive and H5N1 pseudotype particles neutralizing B cell circulating in peripheral blood of a human H5N1 case was recovered by in vitro B cell culture, screening, RT-PCR and expression vector cloning techniques. The Ab gene pairing was screened by transient transfection of human kidney 293T cells and detected using ELISA and neutralization test. The heterosubtypic antibodies were prepared and characterized.@*Results@#We discovered the VH1-2-based heterosubtypic antibodies from two B cell lineages could neutralize GX-H5N1 pseudotype particles and have broader binding with Group 1 (including H1, H5, H6 and H9) and H7 subtype.@*Conclusions@#Cross-reactive antibodies can be induced by H5N1 infection.
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Objective@#To understand the contamination status of avian influenza virus H5, H7, and H9 in environmental samples in Gansu province during 2015, and provide scientific guidance for the prevention and control of human infection with AIV in the province.@*Methods@#We detected the AIV nucleic acid of 2015 environmental samples with real-time PCR; the samples were collected from all of the monitoring points in the whole province, then we analyzed the result of environmental monitoring of pathogens in the province.@*Results@#The detection rates of FluA, H5, H7 and H9 were 19.90%, 0.05%, 0 and 19.65% respectively. The sample specific detection rate of FluA was the highest in wipe specimen of the board surface of slaughtering or placing poultry (31.09%) and the lowest in stool specimens (13.85%). FluA detection rate was the highest in December and the lowest in June and July(8.59% and 8.66%). The detection rate of Dingxi city and Longnan city of nucleic acid of avian influenza virus FluA and H9 were significantly higher than those in other cities in the province(χ2=4.523~88.059, P<0.05).@*Conclusions@#The main AIV pollution of the external environment in Gansu province in 2015 were the H9 subtype, and there was no H7N9 positive, we should strengthen the monitoring and early warning for avian influenza.
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Objective@#To develop the monoclonal antibody (mAb) against neuraminidase of H7N9 subtype influenza A virus and identify its biological function.@*Methods@#Female 8 week-old BALB/c mice were immunized and the splenocytes of the mice were fused with Sp2/0 myeloma cells. Indirect ELISA was used to screen hybridoma and the positive clones were subject to be subcloned. Positive clones were identified and the monoclonal antibodies(mAbs) were obtained by purifying the ascetic fluid of mice injected with the hybridoma. The NA-binding as well as neuraminidase-inhibition activity of these mAbs were determined.@*Results@#Three mAbs against neuraminidase of H7N9 subtype influenza A virus, 1G8, 3C4 and 4E8, were obtained. They demonstrated different epitop-recognizing. 3C4 and 4E8 exhibited neuraminidase inhibitory activity, with a IC50 of 1.45 μg/ml and 8.65 μg/ml, respectively.@*Conclusions@#The results suggested that mAbs specific to neuraminidase of H7N9 subtype influenza A virus were developed, providing an useful tool in control and preventing the novel H7N9 influenza A virus.
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<p><b>OBJECTIVE</b>To investigate the pathogenesis and immunogenicity of H9N2 influenza virus A/Guangzhou/333/99 (a reassortant of G1 and G9 viruses isolated from a female patient in 1999) in a mouse model of infection.</p><p><b>METHODS</b>Mice were infected with increasing virus titers. Viral load in the lungs and trachea was determined by EID50 assay. Pulmonary histopathology was assessed by hematoxylin-eosin staining. Anti-HI antibody titers and T-cell responses to viral HA were determined by ELISPOT and confirmed by flow cytometry.</p><p><b>RESULTS</b>Mice presented a mild syndrome after intranasal infection with A/Guangzhou/333/99 (H9N2) influenza virus. Virus was detected in the trachea and lungs of mice harvested on days 3, 6, and 9 post-infection. A T-cell response to viral HA was detected on day 6 and H9 HA-specific CD(4+) T-cells predominated. Seroconversion was detected after 14 days and antibody persisted for at least 28 weeks.</p><p><b>CONCLUSION</b>Our results suggest that H9N2 (A/Guangzhou/333/99) can replicate in the murine respiratory tract without prior adaptation, and both humoral and cell-mediated immunity play an important role in the immune response.</p>