Real-time RT-PCR determination of viral copy number in Penaeus vannamei experimentally infected with Taura syndrome virus

摘要

This study examined the viral copy number as determined by real-time RT-PCR, in different tissue samples from Penaeus vannamei exposed to Taura syndrome virus (TSV). Two routes of exposure, injection and per os, were investigated. Six different body parts from each shrimp were assessed for viral copy numbers. Eight shrimp were analyzed per treatment. In addition, eight specific pathogen free (SPF) P vannamei were analyzed and served as a negative control. The tissue samples examined included: whole tail muscle, tail muscle (shell removed), gills, pleopods, head (cephalothorax with the hepatopancreas included) and tail fan. The results from these experiments showed a significant level of difference between the SPF and the injection treatments. As was expected, there was also a significant difference between the negative control and the per os treatment groups. There was no significant difference between the viral copy number contained in different body parts from the injection experiment. These results contrasted to the per os results, in which there was a statistically significant difference between tail/gills, tail/head, tail/tail fan, whole tail/tail fan and pleopods/tail fan. The tail samples had the lower viral copy numbers, as did the whole tail and pleopods when compared to the tail fan. The mean viral copy number per nanogram of total RNA ((x) over bar cng tRNA) extracted in the injection study ranged from 1.4 x 10(5) in the gills to 2.3 x 10(5) in the whole tail. In the per os experiment, the (x) over bar cng of extracted tRNA ranged from 2.5 x 10(4) in the tail muscle to 4.3 x 10(5) in the head. When these values are converted to mean viral copy number per gram ((x) over bar cn/g) of tissue, the values increased in range. In the injection study, the (x) over bar cn/g of tissue ranged from 1.2 x 10(9) in the tail fan to 7.4 x 10(9) in the head. These values contrast to the (x) over bar cn/g of tissue in the per os study in that the lowest value of 1.7 x 10(8) was in the tail muscle and the highest (x) over bar, 1.7 x 10(10), was in the head