White tail disease of the giant freshwater prawn, Macrobrachium rosenbergii: separation of the associated virions and characterization of MrNV as a new type of nodavirus

Abstract

White tail disease of the farmed freshwater prawn, Macrobrachium rosenbergii, is the cause of mortalities in the French West Indies, China and India. Two different sized particles, both developing in the cytoplasm of target cells, are found associated with diseased animals. These two viruses were separated, purified and subsequently characterized. The larger one, called MrNV, is icosahedral in shape and 27 nm in diameter. Its genome is composed of two fragments of linear single-stranded RNA (ss-RNA), of 2.9 and 1.3 kb, respectively and its capsids exhibited a single polypeptide of 43 kDa. These characteristics and the partial sequence of a cloned fragment of RNA-1 suggest this agent is a member of the family Nodaviridae, but with differences from both the genera Alphanodavirus and Betanodavirus. The smaller virus, named XSV, is icosahedral in shape, 15 nm in diameter, possesses a linear ss-RNA genome of about 0.9 kb, and its capsid exhibits two polypeptides of 16 and 17 kDa, respectively. The relationships between these two viruses remain unknown.

White Tail Disease of Freshwater Prawn, Macrobrachium rosenbergii

“…Amino acid sequencing of CP-17 and CP-16 clearly indicated that both polypeptides were encoded by the same reading frame and that CP-16 was a truncated form of CP-17, lacking the first 11N-terminal amino acids and it is worthwhile mentioning that the N-terminal end of both polypeptides is methionine. CP-16 was not a degraded form of CP-17 as both polypeptides were found in equimolar ratio and analysis was carried out by directly dissolving the virus particles in Laemmli buffer [2]. Besides, the ATG codon of CP-16 is localized in a favorable Kozak context as the ATG codon of CP-17 (7 out of 11 nucleotides matching with the Kozak consensus sequence).…”

“…Two viruses namely Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus-like particle (XSV) are responsible for WTD [2]. MrNV is a small, icosahedral, non-enveloped particle, 26-27 nm in diameter (Fig.…”

Immunological-based assays for specific detection of shrimp viruses

“…MrNV is a nonenveloped, icosahedral virus with a diameter of 26-27 nm and a genome comprised of two pieces of positive-sense ssRNA. RNA 1 is 3202 bp in length and encodes the RdRp, whereas RNA 2 is 1175 bp in length and encodes a viral capsid protein of 43 kDa [96,101] . Extra small virus (XSV) is usually associated with MrNV.…”

Production and Application of Polyclonal Antibodies Against Recombinant Capsid Protein of Extra Small Virus of Macrobrachium rosenbergii

“…Its genome is composed of two fragments of linear single-stranded RNA (ss-RNA), of 2.9 and 1.3 kb, respectively and its capsid is made up of a single polypeptide of 43 kDa [2]. MrNV is associated with a small virus, XSV, a non-enveloped icosahedral virus, 15 nm in diameter [10].…”

“…The genome is in sense orientation, with a short poly (A) tail at the 3 0 -end. The genome has an ORF of 522 nucleotides coding for a 174 amino acid polypeptide of 17 kDa and a truncated protein of 16 kDa lacking the first 11 N-terminal amino acids [2,10].…”