T .SURESHNIDHI, D. C.,2023-12-272023-12-272022https://krishikosh.egranth.ac.in/handle/1/5810204680Diseases are one of the major constraints in aquaculture and are also the limiting factor for economic and socio-economic development. Emerging viral diseases like Red sea bream iridovirus (RSIV) are known to cause huge economical loss in wild and cultured fish. The virus mainly targets the spleen and kidney of the host and wears out the immune system, making host susceptible for secondary infections. In the present study SISS cell lines was used for virus propagation. Significant cytopathic effect (CPE) like multiple vacuolation, rounding of cells was observed in SISS-infected cells. Virus concentration in culture supernatant collected from infected cell lines was tested by virus titration and yielded viral titres of 106 TCID50/ml. These results indicate the suitability of the SISS cell lines for RSIV propagation. Further, quantitive real-time PCR (qRT-PCR) was carried out to analyze the host defense response in Asian sea bass (Lates calcarifer) challenged with RSIV. Major immune related genes encoding pattern recognition receptors like TLR-3, pro inflammatory cytokines (IFNγ1, TNFα, Casp-1 and IL-8), anti-inflammatory gene (IL-10) and antiviral proteins (MxA, viperin and perforin) were analyzed. There was an up regulation of all immune genes analyzed against RSIV infection at different time intervals in head kidney and spleen. The results revealed varying expression profiles and clear transcriptional activation of these immune related genes in kidney and spleen, which will contribute to better understand the pathogenesis and host defensive system in RSIV invasion.EnglishThesis