Lysozyme gene expression by hemocytes of Pacific white shrimp, Litopenaeus vannamei, after injection with Vibrio.

The purpose of this study was to quantify the gene expression of lysozyme, an important antibacterial protein produced by shrimp hemocytes, within tissues of Litopenaeus vannamei Boone in response to a pathogen challenge. We quantified lysozyme transcripts with a real-time PCR method and used these data, along with total hemocyte counts, to infer patterns of hemocyte trafficking during the immune response. Transcript expression was detected by in situ hybridization of mRNA in circulating hemocytes, and within tissues with high hemocyte concentrations. Lysozyme gene expression was monitored in 5 tissues and in circulating hemocytes for 48 h following challenge with the shrimp pathogen Vibrio campbellii Baumann. The results suggest that lysozyme is expressed in most if not all hemocytes in circulation and in peripheral tissues. Injection with V. campbellii produced a significant decrease in transcriptional signal in circulating hemocytes and peripheral tissues 4 h after injection. Over the same early time period lysozyme signal increased significantly in the muscle at the site of injection and remained high for the duration of the time-course, suggesting that hemocytes are recruited to the site of injection early during the course of the immune response. After 4 h, lysozyme signal increased in circulating hemocytes and tissues, with a return to control levels noted for all tissues except the muscle at the site of injection.