Expression of Toll-like receptors (TLR), in lymphoid organ of black tiger shrimp (Penaeus monodon) in response to Vibrio harveyi infection

•qPCR expression of the TLR gene in healthy and V. harveyi infected shrimp.•Significant upregulation of TLRs was observed at 24h post infection.•Post V. harveyi infection of immunostimulated shrimp showed significant up regulation of TLR gene.•TLR is an immune inducing protein that confers protection to the shrimp. The Toll-like receptors (TLR), being pattern recognition molecules, are a powerful first line of defense in response to pathogen invasion. They are known to play a crucial role in detecting and binding to the microbial molecule and triggering a non-specific immune response. Quantitative real time PCR (qPCR) expression of the TLR gene was studied in healthy and Vibrio harveyi infected black tiger shrimp (Penaeus monodon). Lymphoid tissue expression of TLR in V. harveyi infected animals 24h post injection showed statistically significant up regulation of the gene as compared to the control animals sham injected with phosphate buffered saline (PBS). The qPCR expression pattern of TLR at different time points in shrimp administered with the immunostimulant glucan for 6 days by oral feeding followed by challenge with V. harveyi showed statistically significant level at 48h post bacterial challenge as compared to the control (immunostimulant treated) animals sham injected with PBS. The novelty of the study is that it elicits the role of TLRs as important response proteins of the innate immune system in the shrimp.