Research on expression patterns of endogenous OASL and IFN-α in duck embryos infected with DHAV-3.

An animal body's immune response to viruses might vary depending on various factors. The relationship between 2'-5'-oligoadenylate synthetase like (OASL), interferon alpha (IFN-α), and duck hepatitis A virus type 3 (DHAV-3) virus genome copy number in duck embryo tissues was studied to investigate duck's natural antiviral immunity mechanism. 15-day-old SPF duck embryos were infected with DHAV-3 and their organs and tissues were collected at various times after inoculation. RT real-time PCR was used to determine OASL and IFNA mRNA expression levels and the DHAV-3 copy number. Compared with that at 0 hours, liver OASL transcription increased significantly at 24 hours, and extremely significantly in the liver, heart, gizzard, small intestine, and muscle at 48 hours. The heart had the highest expression level, followed by the liver, with lower expression in the other tissues. There was no significant difference in IFNA expression between the heart and liver at 12 hours, but it started to rise at 24 hours, reaching its maximum at 48 hours. Although IFNA expression increased in the gizzards, small intestines, and muscles, its relative expression levels were lower than those in the heart and liver. In the tissues, the virus genome copy number peaked at 24 hours, and then decreased. The liver had the highest virus genome copy number, followed by the heart. The results implied that the differences in OASL transcription in the tested tissues were similar to those of IFNA. Thus, the immune response (OASL and IFN-α levels) of duck embryos to DHAV-3 shows tissue differences, especially in the liver and heart.