Identification, cloning, and characterization of Cherry Valley duck CD4 and its antiviral immune responses

CD4 protein is a single chain transmembrane glycoprotein and has a broad functionality beyond cell-mediated immunity. In this study, we cloned the full-length coding sequence (CDS) of duck CD4 (duCD4) and analyzed its sequence and structure, and expression levels in several tissues. It consists of 1,449 nucleotides and encodes a 482 amino acid protein. The putative protein of duCD4 consisted of an N-terminal signal peptide, three immunoglobulins and one immunoglobulins-like domain in its central, one terminal trans membrane region, and a C-terminal domain of the CD4 T cell receptor. The duCD4 also has the typical signature CXC of CD4s. The multiple sequence alignment suggests duCD4 has four potential N-glycosylation sites and the phylogenetic analysis suggests duCD4 shares greater similarity with avian than other vertebrates. Quantitative real-time PCR analysis showed that duCD4 mRNA transcripts are widely distributed in the healthy Cherry Valley duck, and the highest level in the thymus. During the virus infection, the obvious change of duCD4 expression was observed in the spleen, lung and brain, which suggesting that duCD4 could be involved in the host's immune response to multiple types of viruses. Our research studied the characterization, tissue distribution, and antiviral immune responses of duCD4.

Automated summary

The duCD4 protein is a transmembrane glycoprotein with broad functionality in immune responses. Its unique sequence and structure suggest potential involvement in host immune responses to various viruses. Tissue-specific expression of duCD4 in healthy and virus-infected ducks indicates its role in antiviral immunity.