Identification and molecular characterization of 18 paramyxoviruses isolated from snakes

Abstract

Viral agents from 18 different snake species (families Colubridae, Viperidae, and Crotalidae) showing respiratory symptoms and neuronal disease were identified as paramyxoviruses by typical cytopathogenic effect (CPE), electron microscopy, and hemagglutination inhibition. Detailed molecular characterization of the viruses was performed by partial l- and f-gene-specific reverse transcription polymerase chain reaction (RT-PCR) and sequencing, nucleotide and amino acid sequence alignment, and phylogenetic analysis (PHYLIP). RT-PCR of the partial l-gene (566 nt) was successful for all 18 viruses; amplicons of the partial F-gene (918 nt) could be obtained in 16 cases. f- and l-sequence alignment revealed similarities to Fer de Lance virus (FDLV) ranging from 79 to 88% on a nucleotide basis, and 94 to 99% on an amino acid basis. Phylogenetic analysis of the ophidian paramyxoviruses resulted in three clusters for the l-gene sequence and corresponding clusters for the f-gene sequence, indicating no species specificity. We analyzed the f-protein of the snake paramyxoviruses, which proved to have an identical conserved motif of heptad repeat A and predicted a furin cleavage site. This uniformity distinguishes the snake virus group from the other type species of the subfamily Paramyxovirinae. For further classification, we aligned the sequences of the ophidian paramyxoviruses and members of the Paramyxoviridae, such as Sendai virus (genus Respirovirus), mumps virus (genus Rubulavirus), measles virus (genus Morbillivirus), human respiratory syncytial virus (genus Pneumovirus) ( Van Regenmortel and 10 co-authors, 2000) and Hendra virus, which have recently been suggested as type species of the genus Henipavirus ( Wang et al., 2000). Maximum sequence similarity was found to the partial l-gene of Sendai virus, with 56% nucleotide and 61% amino acid identity. The FDLV and Sendai virus cluster in the phylogenetic analysis of l- and f-protein regarding the Paramyxovirus type species and Hendra virus and show the closest relationship. Regarding the biological properties, the antigenic distance, and particularly the low homology of available sequences, we propose a new genus for the reptilian paramyxoviruses within the Paramyxoviridae.