Genetic Evolution Analysis And Studies On Pathogenicity Of H6 Subtype Avian Influenza Virus

Avian influenza have caused serious harm to poultry industry and is a kind of zoonosises which have an important public health significance,avian influenza virus serum subtype is numerous,is easier to mutation,H5 and H7 subtypes of highly pathogenic AIV can directly infect poultry and cause serious morbidity,mortality,low pathogenic AIV such as H9 subtype viruses often make some poultry immune suppression or mixed/secondary infection,and cause serious losses to the poultry industry.To understand live poultry market in poultry H6 subtype of low pathogenic AIV poisoned condition and its biological characteristics,throat and anal swabs were collected and identified for 4 strains of H6 subtype AIV from live animal markets in this study,the biological characteristics of four strains of the virus were studied by the analysis of whole genome sequencing and pathogenicity test,the results are as follows.4 strains of H6 subtype AIV which included A/duck/Guangdong/XX88/2016?H6N6??named XX88?,A/goose/Guangdong/QY173/2016?H6N6??named QY173?,A/goose/Gua ngdong/QY204/2016?H6N2??named QY204?and A/chicken/Guangdong/FS249/2016?H6N2??named FS249?Sequence and genetic evolution analysis results showed that the cleavage site of HA gene is"PQIETR?GLF",which have only one basic amino acid is a Characteristics of LPAIV.The results of highest homologous comparison showed that the genes of NA,PB1,PB2 and PA of the isolated strain have recombinanted with some genes of H5 and H9 subtype AIV.The analysises of potential glycosylation sites found that there were multiple sites which may cause abnormal function of the process of expressing proteins.The results of genetic evolution analysis showed that most of the H6 subtypes HA gene are belonged to the large branches of GIII HN573-Llik and GI ST339-like.The above results indicate that H6 subtype AIV is highly likely to undergo internal gene recombination with H5 and H9 subtype AIV.The results showed that the mean dead time?MDT?of XX88,QY173,QY204 and FS249 AIV was 93.3 h,95.4 h,97.6 h and 91.7 h respectively.In H6 subtype AIV the pathogenicity test of SPF?Specific pathogen free?chickens,the experimental group?8young chickens of 28 days old?were inoculated with H6 subtype AIV by injection at 0.2ml 10⁶.0.0 50%embryo infective dosed/0.2 Milliliter(EID₅₀/0.2 mL).The test results showed that experimental groupand cohabitation group have no obvious clinical symptoms.However,the virus can be detected in the throat and anal swab of the attack group at 3⁵ d,the throat and anal swab of XX88 and QY204 cohabitation group can also detect the virus.The serum HI antibody of the attack group was positive.The results of histopathological examination showed a small amount of inflammatory cells infiltration in the chicken lungs,other groups have no obvious pathological changes.The pathogenicity test of SPF chickens show that poison attack 4 strains of H6 subtype AIV have low copy ability and low pathogenicity in chicken body.4 strains of the virus were infected with BALB/c mice by nasal drops with a dose of10⁶.0.0 EID₅₀/0.1ml,and the results showed that the mice in the attack group showed a phenomenon of weight loss or slow growth within 1⁶ d after the attack;Virus can only be detected in the nasal bones and lungs,and the virus content of the lung is significantly higher than that of the turbinate.,mice serum HI antibody detection revealed not turn positive;It showed that the four H6 subtype AIVs had certain replication ability and pathogenicity in BALB/c mice.