A complete cDNA sequence is reported for LRV2-1, the first Leishmania RNA virus known to infect an Old World parasite, Leishmania major. Sequence analyses show that LRV2-1 differs significantly from members of the LRV1 genus which infect New World parasites. The data support a view that transmission of LRV is strictly vertical and suggest that LRV predate the divergence of Old and New World parasites. As a consequence of this divergence, conserved features can be identified for the first time in Leishmaniavirus proteins. A finding that the virus capsid and polymerase genes do not overlap is unique among the known Totiviridae and infers that a gag-pol fusion protein cannot be produced simply via tRNA slippage in LRV2-1.

No abstract

Leishmaniavirus is a double-stranded RNA virus that persistently infects some strains of the protozoan parasite Leishmania. There is considerable interest in the possibility that the presence of this virus alters parasite phenotype and may affect disease pathogenesis. If so, the virus marker could provide a valuable prognostic indicator for human leishmaniasis, particularly in those cases caused by New World parasite strains. The virus has been detected in cultured L. braziliensis, L. b. guyanensis, and L. major. To date there has been no information as to the extent of infection in samples prior to culturing in the laboratory. This study demonstrates, through the reverse transcriptionpolymerase chain reaction, that Leishmaniavirus exists in human biopsy samples of leishmaniasis prior to manipulation in culture.

Double-stranded Leishmania RNA virus 1-4 (LRV 1-4) has at least four open reading frames (ORFs). The two small ORFs located near its 5' terminus, ORF1 and ORFx, could encode 34- and 60-amino acid polypeptides, respectively. ORF2 encodes an 82-kDa major capsid protein, and ORF3 encodes a 98-kDa polypeptide which contains the consensus sequence for RNA-dependent RNA polymerases of plus-strand and double-stranded RNA viruses. The complete sequence of LRV 1-4 shows that ORF2 and ORF3 overlap by 71 nucleotides, and that ORF3 lacks a potential translation initiation site, suggesting that the viral polymerase may be synthesized as a 180-kDa fusion protein with the virus capsid. In this report, we present evidence for the synthesis of a fusion protein through a ribosomal frameshift. In vitro-translation experiments and immunostudies involving antiserum against the viral capsid protein demonstrated that the overlapping 71 nucleotides of ORF2 and ORF3 are contained in a region which promotes translational frameshifting. Computer analysis of the putative frameshift region revealed a potential pseudoknot structure located within the overlapping 71 nucleotide sequence.