2015-2020年FAdV-4安徽流行株全基因组测序分析及不同感染途径的致病性研究

为探讨血清4型禽腺病毒（FAdV-4）安徽流行株的基因组遗传变异特征及其感染途径与致病性的关系，选择2015-2020年6株FAdV-4安徽分离株进行全基因组测序与分析，并以CH/AHMC/2015株对10日龄SPF鸡进行不同感染途径（皮下注射、口服、点眼、滴鼻及其分别同群混养）的致病性试验。结果显示，6株FAdV-4安徽分离株的基因组全长均为43 719～43 723 nt，其核苷酸同源性达99.97%，与国内FAdV-4主要流行株同源性为99.56%～100%，与国外经典毒株ON1、KR5、MX-SHP95同源性为98.45%～98.78%；6株病毒与国内代表株HB1510具有13个核苷酸位点差异，并导致5个位点氨基酸变化，与国外经典毒株存在特征性差异。氨基酸分析显示，Hexon蛋白aa188、Fiber-2蛋白aa219和aa380 3个氨基酸位点存在一定的特征性，致病株主要为R、D、T，非致病株主要为I/V、G、A。进化分析显示，国内FAdV-4流行株与巴基斯坦、印度分离株的遗传关系最近。感染试验显示，皮下注射、口服、点眼、滴鼻4 组人工感染鸡的发病率和死亡率分别为100%、55%、50%、60%和90%、20%、40%、50%，各组同群混养鸡的发病率为20%～40%，仅皮下注射组混养鸡出现死亡，死亡率为20%。结果表明，2015-2020年FAdV-4安徽省流行株具有国内主要流行致病株特征，其不同感染途径的结果进一步揭示该病的临床流行特点，为该病防制提供科学依据。

Sequence Analysis of Complete Genome of Epidemic Strain FAdV-4 in Anhui Province from 2015 to 2020 and Pathogenicity from Different Infection Routes

To investigate the genomic genetic variation characteristics of the epidemic strain fowl adenovirus serotype 4(FAdV-4) found in Anhui province of China and the relationship between its route of infection and pathogenicity.Six isolates of FAdV-4 in this area were chosen for whole genome sequencing(WGS) from 2015 to 2020.And 10-day-old SPF chickens were infected with CH/AHMC/2015 strain through different routes of infection(subcutaneous injection, oral administration, ocular, intranasal and co-feeding in each group).The results showed that the genomes of the six isolates of FAdV-4 ranged from 43 719 to 43 723 nt.And its nucleotide homology was 99.97%, compared with 99.56% to 100% for the main epidemic strain of FAdV-4 in other areas of China and 98.45%- 98.78% for the main foreign ON1, KR5 and MX-SHP95 strains.There were 13 different nucleotide sites between the 6 strains and the domestic epidemic strain HB1510, and amino acid in 5 sites changed.Besides, there were characteristic differences between the 6 strains and the epidemic strains abroad. Analysis of amino acid showed that the certain characteristics among Hexon protein AA188 and Fibre-2 protein AA219 and AA380 were found on 3 sites of amino acid.And the pathogenic strains were mainly R, D and T, while the non-pathogenic strains were mainly I/V, G and A.Evolutionary analysis showed that the domestic FAdV-4 strain was genetically related to the Pakistan and Indian isolates.Infection tests showed that the morbidity and mortality rates in the four groups of chickens infected by subcutaneous injection, oral administration, ocular, intranasal were 100%, 55%, 50%, 60% and 90%, 20%, 40%, 50%, respectively.And the morbidity rate of chickens kept together in each group ranged from 20% to 40%, and only the chickens infected by subcutaneous injection died, with mortality rate of 20%.The results indicated that the epidemic strain FAdV-4 found in Anhui province from 2015 to 2020 shared the characteristics of the main causative strain in China.And the different infection routes further revealed the clinical epidemiological characteristics of the disease and provided a scientific basis for its prevention and control.