Host-specific Genotype Patterns of Orf Virus as Revealed from Genetic Analysis of GM-CSF/IL-2 Inhibition Factor (GIF) Gene

Abstract

Contagious Ecthyma (CE), commonly referred to as Orf or scabby mouth, is a viral disease that mostly affects sheep and goats, caused by the Orf virus. In addition to sheep and goats, it also affects domestic and wild ruminants, as well as humans, highlighting its zoonotic importance. This study aims to characterize ORFV strain circulating in Tamil Nadu. In the present study, the partial GM-CSF/IL-2 inhibition factor (GIF) gene of ORFV was amplified from nine ORFV-positive clinical material/isolates recovered from nine different outbreaks over five years (2012 to 2016) from Tamil Nadu State, India. Further GIF gene-specific PCR-RFLP analysis was carried out with Hae III and sequence analysis was carried out to identify the strain variation among ORFV strain. In PCR all the nine-samples yielded 408 bp GIF-gene specific PCR amplicons.  RFLP analysis identified three distinct genotyping patterns (I, II and III) among ORFV strains infecting sheep and goats. All sheep-associated ORFV strains belonged to a single genotype, while two additional genotypes were detected among the goat-associated strains. Moreover, the nucleic acid and deduced amino acid sequence analyses revealed the presence of distinct genotyping patterns among the ORFV affecting sheep. On phylogenetic analysis, the GIF gene phylogenetic tree revealed the distinct clustering of sheep and goat ORFV. The presence of host-specific molecular signatures and the heterogeneity among ORFV strains among species circulating in the field necessitates thorough investigation of the prevalent genotypes and/or molecular patterns biased towards the particular preferred host, the importance of cross-immunity across the heterologous host, and the use of universal or host-specific vaccine strains for effective disease prevention.