Rabies virus (RABV) is a single stranded RNA genome virus that encodes five proteins: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and RNA dependent polymerase (L). However, RABV seem to be remarkably stable antigenic and genomic differences among isolates from different species have been recognized for many years. Analysis of RABV isolates from different natural reservoirs reveals antigenic variants and/or genetic lineages with specific characteristics, suggesting selection and adaptation of viruses to each of the particular species. Such selections and adaptations are so specific that they allow for the identification of the natural reservoir of origin of a determined isolate. This work was conducted to investigate the genomic and antigenic stability of four different genetic lineages of RABV, originated from different host species, following successive passages in mice. Four RABV isolates (IP4005/10, IP964/06, IP3629/11 and IP4871/11) were inoculated intracerebrally into 3-4 weeks-old mice. After each passage, the viruses were examined in their antigenic profile with a panel of monoclonal antibodies to rabies virus antigens. Viral RNA was extracted from the 1st, 5th and 10th passages and submitted to reverse transcription (RT) followed by polymerase chain reaction (RT-PCR), sequencing and phylogenetic analyses. Antigenic profile of the isolates did not reveal any recognizable alteration throughout. No nucleotide substitutions were noticed in the final sequences in any of genes sequenced from the four RABV isolates, with the exception of one nonsynonymous substitution in the putative protein P in position of amino-acid 222 in the isolate of non-hematophagous bat origin. These findings highlight the high antigenic and genetic stability of RABV, as opposed to the alleged high genomic variability of viruses with RNA genomes. On the other hand, it seems that different isolates may present different degrees of genetic stability, what may be related to the degree of adaptations of the isolate to the reservoir.
Keywords:Rabies, Successive passages, Reservoirs.