| H9N2 avian influenza virus(AIV)has spread widely in poultry worldwide,causing significant loss to the poultry industry.With its increased human-receptor binding profile and increased droplet transmissibility among mammals,H9N2 has been considered to have the potential to cause the next influenza pandemic.After being isolated from turkeys in the United States for the first time in 1966,a case of human infected with H9N2 AIV was first identified in Guangdong,China in 1999.Since then,sporadic human infection with H9N2 have continuously been reported.H9N2 infections could cause egg reduction and weight loss in poultry,while the clinical symptoms of infected people are often mild or asymptomatic.Antigenic cross reactions between H9N2 and different subtypes of influenza A viruses circulating among human and animal have been observed.A previous study on 174 Spanish elderly people vaccinated with seasonal influenza from 2007 to 2011 found that the vaccine could induce a 10.9%cross-protection rate of heterotypic antibody against H9N2.However,no study on the cross-protection antibody in serum from seasonal influenza vaccinated population against H9N2 has documented in China.In addition,when handling the H9N2 viruses in the laboratory,it is of note importance to protect the operator for the maintenance of laboratory biological safety.Therefore,our study focused on the virus inactivation of H9N2 subtype AIV in laboratory,and the cross-reaction antibodies in the human serum post seasonal influenza vaccinations against H9N2 AIVs.Our study evaluated the inactivation effect of different temperature,ultraviolet light and three disinfectants(10%84 sanitizer,75%ethanol,1%Virkon solution)on H9N2 AIVs.The results showed that the virus titer decreased by 4.02 lgTCID50 when the H9N2 virus was treated at 56℃ for 15 minutes,and the virus activity decreased below the detection level after treatment for 30 minutes;After heat inactivation at 60℃ and 65℃ for more than 10 minutes,the virus activity decreased below detection level.After 20 minutes of UV irradiation,the activity of H9N2 virus decreased by 5.67 lgTCID50,and the virus decreased below the detection level after 70 minutes of exposure.Virus proliferation was not detected after 3 minutes exposure of 10%84 sanitizer,75%ethanol and 1%Virkon.In order to assess the level of cross-protective antibody against H9N2 induced by seasonal influenza vaccine,397 pairs(794 tubes)sera of pre or post seasonal influenza vaccine shot were recruited from Yunnan Province and Xinjiang Uygur Autonomous Region from 2015～2019.Each serum was tested with 3 different lineages/strains of H9N2.The results showed that the serological prevalence rate of H9N2 during 2015～2019 in Yunnan and Xinjiang was 3.36%(40/1191).In addition,after immunized by seasonal influenza vaccine,the protection rate against H9N2 viruses was 3.53%(42/1191).Comparing the antibody titer levels of pre-vaccination,it was found that the antibody titer changes against H9N2 post the seasonal influenza vaccination campaign was statistically different(Z=-5.406,p<0.01).The result showed although at a low level of 3.53%,the vaccination of seasonal influenza vaccines in humans could induce a heterotypic antibodies against H9N2 AIV.With the increased surveillance of highly pathogenic avian influenza viruses including H5N1 and H7N9 viruses,H9N2 subtype influenza virus has been increasingly identified and isolated from influenza-like cases.The symptoms of H9N2 infection are similar to seasonal influenza infections with mild clinical features.Besides of humans,H9N2 can also infect a variety of animals,including chickens,ducks,wild birds and pigs.The prevalence of H9N2 viruses in these animals increased the resorted possibilities of the viruses with other co-circulated influenza viruses,and thus would generate the variants with pandemic potential.Therefore,strengthening the genetic and serological surveillance on H9N2 AIV are of great significance for the viral prevention and control. |
PDF Full Text Request