Effect of CPG ODN on infectious bronchitis virus replication in trachea and kidneys of chicken embryos

Toll like receptors (TLRs) are a major class of innate immune pattern recognition receptors that play a key role in the immune response and defense against infections. TLRs are essential for initiation of the innate immune responses and development of the adaptive immune responses. The immunomodulatory property of TLR agonists has led to their exploitation as both prophylactic agents to enhance host immunity to pathogens and adjuvants to induce robust immune response against vaccine antigens. The CpG DNA is the most widely used TLR agonist as an adjuvant in several infectious diseases of chicken such as fowl cholera, avian influenza and pathogenic E. coli. The present study was conducted on the hypothesis that the pre-treatment of specific pathogen free (SPF) embryonated chicken eggs (ECEs) with CpG ODN may reduce the viral load of infectious bronchitis virus (IBV) in the trachea and kidneys of ECEs. The antiviral activity of CpG ODN was tested in SPF ECEs. The CpG ODN was administered in 18 days old ECEs through allantoic route. The Dulbecco’s phosphate buffered saline was given in the control group. The trachea and kidneys were collected after 24 and 72 h of IBV infection and quantification of IBV was done in the trachea and kidneys. The results revealed that the CpG ODN significantly reduced the IBV titer in trachea and kidneys of the treated group as compared to the control group. In conclusion, the CpG ODN may act as a good antiviral agent and an adjuvant for improvement and development of in ovo vaccines against IBV.

• TLRs are innate immune pattern recognition receptors (PRRs) that play a key role in the immune response and defense against infections

• The CpG DNA is the most widely used TLR agonist as an adjuvant in several infectious diseases of chicken

• CpG ODN significantly reduced IBV load in trachea and kidneys of chicken embryos