Viral DNA sequences of genes encoding the ATPase and the major capsid protein of tropical iridovirus isolates which are pathogenic to fishes in Japan, South China Sea and Southeast Asian countries

Abstract

Tropical iridovirus infection causes severe epizootic resulting in mass mortalities and large economic losses in freshwater ornamental fishes cultured in Southeast Asian countries, in wild fish seedlings captured in South China Sea, and in marine fishes farmed in Japan, Singapore, and Thailand. All of tropical iridovirus-infected fishes histopathologically showed the systemic formation of inclusion body-bearing cells and necrosis of virus-infected splenocytes and hematopoietic cells. We designed primer sets for the ATPase gene and the major capsid protein (MCP) gene and sequenced the PCR products derived from 5 iridovirus isolates from sea bass in South China Sea, red sea bream in Japan, brown-spotted grouper with a grouper sleepy disease in Thailand, dwarf gourami from Malaysia and African lampeye from Sumatra Island, Indonesia. The ATPase gene and the MCP gene of these 5 viral isolates were highly homologous (> 95.8%, > 94.9% identity, respectively) and the deduced amino acid sequences of the ATPase and the MCP were also highly identical (> 98.1%, > 97.2% identity, respectively). Based on the high homology, these 5 isolates of tropical iridovirus from various fishes in geographically different regions were determined to have a single origin and to be native to Southeast Asian regions. However, these sequences were far different from those of members of the genera Ranavirus, Lymphocystivirus and Iridovirus in the Family Iridoviridae. We propose a new genus "Tropivirus" for tropical iridovirus in the Family Iridoviridae.

Histological, ultrastructural, and in situ hybridization study on enlarged cells in grouper Epinephelus hybrids infected by grouper iridovirus in Taiwan (TGIV)

“…High similarity was observed between cells infected by TGIV and those infected by tropical iridoviruses. However, in contrast to tropical iridovirus-infected cells, in TGIV-infected cells there is no apparent slit or membranous structure separating the viromatrix from the cytoplasm as sometimes seen in tropical virus infections (Sudthongkong et al 2002b). The nuclei of TGIV-infected cells disintegrated before the viromatrix was fully established in the cytoplasm; however, the nuclei was displaced to one side in tropical iridovirus-infected cells, even when the inclusion bodies occupied most of the cytoplasm , Sudthongkong et al 2002a.…”

“…He et al (2001) compared ATPase, DNA polymerase and RNA polymerase genes of selected members of Iridoviridae and suggested that RSIV, SBIV, ALIV, GIV and ISKNV may belong to a new genus, and tentatively referred to them as 'cell hypertrophy iridoviruses'. A research group led by T. Miyazaki also proposed the definition tropical iridovirus or 'Tropivirus' for these viruses (Sudthongkong et al 2002b). In 2003, V. G. Chinchar et al (pers.…”

Characterization of an iridovirus detected from cultured turbot Scophthalmus maximus in Korea

“…Recently, Sudthongkong et al (2002) proposed a new genus, Tropivirus, in this family for tropical iridoviruses including RSIV, SBIV, GSDIV, ALIV and DGIV based on nucleotide sequencing of the MCP and ATPase genes. We found that sequence homology in the MCP gene of TBIV was high (> 93.75%) with the MCP genes of these viruses and low with the MCP genes of the genera Ranavirus (FV3; 56.35%, GIV; 52.06%) and Lymphocystivirus (LCDV-1; 53.06%), suggesting that TBIV is similar to the tentatively proposed genus Tropivirus.…”

“…The nucleotide sequence of the partial MCP gene of turbot iridovirus (TBIV) was submitted to GenBank (accession number AB166788). The TBIV MCP gene was compared with the MCP genes of 2 genera of iridoviruses - (1) Sudthongkong et al 2002] and African lampeye iridovirus [ALIV; AY285745, Sudthongkong et al 2002]). …”

Cloning of a new fibroblast cell line from an early primary culture from mandarin fish (Siniperca chuatsi) fry for efficient proliferation of megalocytiviruses

“…An early molecular epidemiologic investigation showed that RSIV infects over 30 marine-cultured fish in Japan (Kawakami and Nakajima 2002;Matsuoka et al 1996). Simultaneously, RSIV-like viral agents associated with mass mortality of finfish were also described from Australia (Anderson et al 1993), Singapore (Chua et al 1994), Chinese Taiwan (Chou et al 1998), mainland China (He et al 2000), South Korea (Jung and Oh 2000), and other Southeast Asian countries (Sudthongkong et al 2002). Most recently, natural outbreaks of megalocytivirus-associated diseases were firstly reported emerging in North America (Marcos-López et al 2011).…”