Combination of H120 and 1/96 avian infectious bronchitis virus vaccine strains protect chickens against challenge with IS/1494/06 (variant 2)-like infectious bronchitis virus.

Avian infectious bronchitis (IB) is a worldwide chicken disease, caused by avian infectious bronchitis virus (IBV) which infects all commercial poultry lines. The present study was done to evaluate protection caused by two different serotype vaccines (Massachusetts and 793/B) in order to evaluate protection against challenge with IS/1494/06-like virus (variant 2-like virus), which is prevalent in the Middle East. SPF chickens were divided into four groups (n = 20). First and second group as negative control group and non-vaccinated-challenged group received no vaccine. Groups 3 and 4 received H120-H120 and H120-1/96 IBV vaccine strains at the 1st and 14th day, respectively. Twenty one days after last vaccination, non-vaccinated-challenged group and vaccinated group were challenged using variant 2-like IBV. Serum samples were collected before challenge to measure humoral immune response of chickens. Five days after challenge, the tissue samples from the trachea, lungs and kidneys were taken to evaluate cilliary activity, viral load (quantitative real-time RT-PCR), and histopathological evaluation. Clinical sign scores were also recorded after challenge. Overall, the results showed a protective efficacy of the used vaccination program. Best cross protection (69.2%) was obtained in the H120-1/96 vaccinated group. Virus replication of the challenged virus in H120-1/96 group compared with H120-H120 group showed a significant reduction of viral load in trachea (1.5×103 compared to 503) and kidneys. Clinical sign scores of the challenged groups showed significant effect of the vaccination program to reduce clinical signs. The trachea pathological scores and histopathological findings in the lungs and kidneys also confirmed better protective efficacy of vaccinated groups. In conclusion, using combination of heterologous IBV vaccine serotypes (Massachusetts and 793/B) would be a better strategy to control variant 2-like viruses, but more evaluation is needed using other circulating isolates to find the best combination of vaccines.

Phylogenetic study on nonstructural (NS) gene of H9N2 isolated from broilers in Iran during 1998-2007.

Since 1998, H9N2 AI outbreaks have been one of the major problems in Iranian poultry industry. The association of high mortality and case report of H5N1 and H9N2 influenza virus in wild birds in recent years raised the specter of a possible new genetic modified AI virus. In this study, we do phylogenetic analysis on Full- length Nonstructural (NS) genes of seven H9N2 Isolates from Broilers in Iran, Tehran province during 1998-2007. Phylogenetic analysis clearly shows that Iranian H9N2 isolates gene pools, corresponding to just NS allele A. Comparison of nucleotide sequences of isolated viruses revealed a substantial number of silent mutations, which results in high degree of homology in amino acid sequences. In addition, the cluster of Iranian H9N2 isolates could be subdivided into two subgroups, which matched their times of isolation especially around 2006 time line. The high degree of similarity between the NS genes of the Iranian H9N2 isolates supports the hypothesis that these genes originated from a single predecessor. Present result provides useful molecular epidemiological data to understand the dynamics of H9N2 evolution during 9 years in Iran and support earlier phylogenetic observations.