Expression of polymeric immunoglobulin receptor (pIgR) and immunoglobulin (IgM) gene in mucosal-associated lymphoid tissues (MALT) of Labeo rohita fingerlings immunized with pDNA (pGPD-IFN) vaccine

Abstract

Polymeric immunoglobulin receptor (pIgR) is a protein that transports Immunoglobulins (Igs) from epithelial cells into the external secretion system of the animal. In the present study, we characterized the partial pIgR gene from Labeo rohita and analyzed its expression in response to the pDNA (pGPD-IFN) vaccine, and studied its correlation with the expression of IgM, in the mucosal-associated lymphoid tissues (MALT). The significant (p < 0.05) up-regulation of pIgR mRNA was observed in the mucosal tissues of vaccinated fish by qRT-PCR. The highest expression of the gene was detected in gill tissue at 15 days post-vaccination (dpv) followed by skin and gut at 30 dpv. The expression of IgM also showed a similar pattern and indicated a direct correlation of pIgR expression in all the tested tissues. The protective immune response of the DNA vaccine was measured as the relative percentage of survival (RPS) by challenging vaccinated fish with live Edwardsiella tarda (1 × 105 CFU/Fish). The result showed a significantly high relative percentage survival (RPS) in the vaccinated group (47.05%) compared to the control group. Many factors contributing to the immune response of the vaccine. One of the most critical aspects is the rise in IgM level in local tissues. In other higher vertebrates, pIgR is reported to act as the transporter of IgM. The positive correlation in the expression of pIgR and IgM observed in the present study demonstrated the possible role of pIgR as the transporter of IgM in L. rohita. The study suggests the possibility of the secretory nature of IgM in fish.