Panaeus monodon and their immune- related genes.

A review of: Soonthornchai, W, et al. 2009. Experession of immune- related genes in the digestive organ of shrimp, Panaeus monodon after an oral infection by Vibrio harveyi.

Production of the cultivated shrimp Panaeus monodon has increased massively over the past 3 decades. This rapid increase has seen an increasing problem with disease outbreaks. Vibrios is the most common bacterial disease that cause mass moralities of shrimp world wide. Shrimp are exposed constantly to a variety of bacteria and viruses, and hence the defence mechanisms they employ.
Most of the immune response knowledge known to date has been obtained through the direct injection of bacteria into the body cavity or tissues of the organism. this approach has shown to be effective in identifying host mechanisms. But it bypasses the natural entry route of infections and the subsequent paths within the organism. This study instead used an immersion technique. This is a more natural technique of simulating an infection.

Panaeus monodon juveniles (3-4 Months) were obtained from Thailand and an immersion technique was conducted using Vibrio harveyi 1526 (vh). Control shrimp were also used during the course of this experiment. RNA isolation of each sample was conducted. RNA was extracted using Trireagent. Reverse transcription PCR was then conducted, and the immune related genes were isolated. To confirm changes in the expression of immune-related genes such as penaidin, crustin and C-lectin, quantitative real time PCR analysis was conducted. The six genes that showed the biggest effect after bacterial infection were selected to determine the tissue distribution. Tissue samples of the digestive system were studied for immune gene expression following bacterial infection. All samples were then fixed in R-F fixative. paraffin embedded tissues were sectioned, stained and analyses under a light microscopy.
During the experiment fifteen immune-related genes were discovered, throughout the entire experiment all of these genes continued to be expressed in high levels. Only six of these genes were known to be effected by the bacterial infection.VH uses sophisticated strategies to counteract immune responses in the gut, their persistence usually results in colonization and rapid multiplication in the shrimps gut. The epithelium is damaged as the bacteria attempt to gain entry into the immune system. The natural method of simulating an infection used in this study proved useful in establishing the shrimps natural genetic defences against VH. In previous studies where direct injection of the bacteria was used the gene expression did not increase drastically in comparison to the heightened expression of genes using the immersion technique.