Genetic characterization and phylogenetic analysis of host-range genes of Camelpox virus isolates from India

Abstract

Camelpox virus (CMLV), a close variant of variola virus (VARV) infects camels worldwide. The zoonotic infections reported from India signify the need to study the host-range genes—responsible for host tropism. We report sequence and phylogenetic analysis of five hostrange genes: cytokine response modifier B (crmB), chemokine binding protein (ckbp), viral schlafen-like (v-slfn), myxomavirus T4-like (M-T4-like) and b5r of CMLVs isolated from outbreaks in India. Comparative analysis revealed that these genes are conserved among CMLVs and shared 94.5–100 % identity at both nucleotide (nt) and amino acid (aa) levels. All genes showed identity (59.3–98.4 %) with cowpox virus (CPXV) while three genes—crmB, ckbp and b5r showed similarity (92–96.5 %) with VARVs at both nt and aa levels. Interestingly, three consecutive serine residue insertions were observed in CKBP protein of CMLV-Delhi09 isolate which was similar to CPXV-BR and VACVs, besides five point mutations (K53Q, N67I, F84S, A127T and E182G) were also similar to zoonotic OPXVs. Further, few inconsistent point mutation(s) were also observed in other gene(s) among Indian CMLVs. These indicate that different strains of CMLVs are circulating in India and these mutations could play an important role in adaptation of CMLVs in humans. The phylogeny revealed clustering of all CMLVs together except CMLV-Delhi09 which grouped separately due to the presence of specific point mutations. However, the topology of the concatenated phylogeny showed close evolutionary relationship of CMLV with VARV and TATV followed by CPXV-RatGer09/1 from Germany. The availability of this genetic information will be useful in unveiling new strategies to control emerging zoonotic poxvirus infections.