Immune gene expression studies in Oreochromis niloticus (Linnaeus,1758) experimentally infected with Tilapia lake virus (TiLV)
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Date
2020
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Fisheries College and Research Institute, Thoothukudi, Tamilnadu Dr.J.Jayalalitha Fisheries University
Abstract
Tilapia being the largest farmed fish species after carps worldwide, contributes largely to food security as an inexpensive dietary protein in the developing world. Intensification and diversification thus leads to the emergence of the infectious diseases and Tilapia Lake Virus (TiLV) gaining widespread attention due to its pervasive occurrence and devastating effect on tilapia stocks. The pre-isolated TiLV was made for the expression of the innate immune-related genes IPS-1 and TLR-7 in brain, kidney, liver and spleen using quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR).
The TiLV grew well in both Epithelia pappilosum of carp (EPC) and striped snakehead (SSN1) cell lines at 27°C. The virus induced cytopathic effects such as focal area clearance, granulation of cells and rounding of cells within 3-4 days post-inoculation. A complete destruction of the monolayer with cell detahmnet was found within 6-7 days. Subsequent passage of SSN1 cell line showed a good CPE. The quantification of virus was done using TCID50 and was found to be 105-106/ml.
The experimental infection study of tilapia fingerlings with Intra-peritoneal injection of the Virus supernatant showed clinical signs typical to TiLV infection with abnormal swimming, skin and scale loss, skin discolouration and open ulcers, fin rot, abdominal swelling and bilateral exophthalmia. Mortality also reported among the experimental infected fishes.
mRNA expression patterns of the genes IPS-1 and TLR-7 were examined post infection at six different time intervals at 12, 24, 36, 48, 72 and 96h in four tissues namely brain, kidney, liver and spleen. These studies revealed that both brain and liver give highest up-regulation patterns followed by kidney and spleen. The expression profile of IPS-1 and TLR-7 threw insight that the virus follows both TLR and RLR pathways. The highest expression obtained in brain and liver concludes with the primary target organ organs of TiLV infection in tilapia. Further research should stress on the molecular mechanisms followed in the virus-host interactions leading to the development of vaccine.