Isolation of a Chlamydia Strain from Lung Tissue Samples in Healthy Chickens Exhibiting Antagonistic Effects on Avian Infectious Bronchitis Virus

To assess the feasibility of isolating Chlamydia strains with antiviral activity against avian infectious bronchitis virus (IBV) from healthy chickens in farms, 58 Chlamydia strains were obtained from 160 lung tissue samples collected across ten chicken farms, yielding an overall isolation rate of 36.25%. SPF chickens co-infected with Chlamydia and IBV were employed for verification, leading to the identification of eight strains (Bi [&ge;] 0.800) with potent antiviral effects against IBV, accounting for 13.79% of the total isolated strains. The top-performing strain, Y17 Chlamydia strain, was selected and subjected to cell co-culture and U-tube experiments with IBV. Results demonstrated that the Y17 Chlamydia strain significantly impeded IBV replication in chicken tracheal epithelial cells (P<0.01) and did not secrete or induce host cells to secrete extracellular metabolites with antagonistic effects on IBV infection in U-tube experiments (P>0.05), suggesting that its antiviral activity was cell-autonomous. Our research highlights the feasibility of isolating Chlamydia strains with antiviral activity against IBV from healthy chickens and suggests that antiviral strains could be widespread, even though their efficacy against viruses is strain-specific. The presence of broad-spectrum antiviral Chlamydia strains may also be possible. Considering the prevalence of Chlamydia strains in vertebrate hosts, along with the fact that some strains are either non-pathogenic or display low toxicity, our findings could offer a fresh perspective on the prevention and treatment of viral infections in vertebrates.