Analysis of adenovirus strains isolated from poultry in Poland

The study describes successful isolation of 96 fowl adenovirus (FAdV) strains from 789 chickens from 95 flocks. PCR specific for hexon gene encoding L1 loop was conducted. Amplicons were subjected to sequence analysis. The sequences were analysed by the software: BLAST, Geneious 6.0, and MEGA 5, then aligned with different adenovirus strain reference sequences accessible in GenBank database. The examined strains belong to the particular groups and serotypes. The sequences of all adenoviruses were classified into five species (FAdV A–E) and eight serotypes (FAdV-1, FAdV-2, FAdV-4, FAdV-5, FAdV-7, FAdV-8a, FAdV- 8b, and FAdV-11). Key words: chickens, aviadenoviruses, PCR, phylogenetic analysis, Poland. Introduction Adenoviral infections are widely prevalent among birds including poultry and wild species in almost every country in the world (7). Each year in Poland, the number of cases of adenovirus infections in birds is increasing. The pathogenic role of the aviadenoviruses is not clear enough. They can be isolated from both sick birds, and birds without any signs of illness (12, 16). The role of adenoviruses as the opportunistic factors is indicated (7). They can cause asymptomatic infections, but also they are an aetiological agent of diseases such as inclusion body hepatitis – IBH (6), hydropericardium hepatitis syndrome – HHS (7), gizzard erosion and ulceration (GEU) (20), and pancreatitis (24). Adenoviruses can be one of the reasons of immunodeficiency. Aviadenoviruses are icosahedral in shape and non-enveloped dsDNA viruses with capsid size about 70-100 nm in diameter, which consists of 252 capsomers surrounding the core (13, 16). Hexon is the main protein of the adenovirus capsid, encoded by 2800-2900 bp long fragment, with molecular weight of 106,7 kDa, (1, 4). The protein consists of conservative components P1 and P2, which build the basis of the particle and allow to form trimmers. The variable fragment of the hexon protein forms the loops L1, L2, and, L4 (21). The L1 loop (Hyper Variable Region, HVR) is 130 aa long and flanked by the P1 region (8). There are four HVRs located in loop L1, two HVRs in loop L2, and one in loop L4. The type-specific antigenic determinant „e” is encoded by HVR region of L1 and L2 loops (21), while the sequence of L1 loop of adenovirus genome is specific for 12 serotypes of adenovirus (21). This protein is responsible for the antigenic activity of the virus. Adenoviruses existing in poultry were divided into five species (FAdV A–E) and 12 serotypes (FAdV-1–8a, 8b–11) (5, 16, 23). The aim of this study was the molecular analysis of fowl adenovirus strains on the basis of L1 DNA sequences of hexon gene.