Genomic and biological characterization of Pigeon Paramyxovirus Type-1 isolated from Indian pigeons: First report on the six nucleotide insertion in the non-coding region of nucleoprotein gene

Abstract

Genotypic analysis of Pigeon Paramyxovirus Type-1 (PPMV-1) virus, in corroboration with pathotyping, underpins the knowledge on the occurrence of PPMV-1 mediated Newcastle disease in poultry. In the present study, two PPMV-1 isolates, namely D167 and D168, obtained from feral pigeons of India in the year 2014 were analysed for their genotypic and pathotypic characteristics. Phylogenetic analysis of Fusion (F) gene grouped D167 and D168 under sub-genotypes VI.2.2.2. and VI.2.1.1.2.2. respectively. The separate positioning of these isolates within genotype VI is corroborated with the variation in restriction enzyme sites analysed through virtual restriction mapping. Analysis of FPCS region showed that both D167 and D168 possessed 112RRQKRF117 amino-acid pattern. Intra-cerebral pathogenicity index (ICPI) of D167 and D168 was 1.57 and 1.3, and mean death time (MDT) was 48 and 70 hrs respectively, designating D168 as a mesogenic pathotype, and D167 as a velogenic pathotype. Histopathological analysis of proventriculus, intestine, lungs and spleen of chickens infected with D167 and D168 isolates through intramuscular (I/M), subcutaneous (S/C) and oculo-nasal/oral (O/N) routes of inoculation showed similar severity of tissue damage. This study shows that PPMV-1 isolates belonging to two different sub-genotypes without a common ancestor, can occur together in a particular geographical region. It also shows that PPMV-1 gains virulence in chickens, which needs to be addressed in order to avoid emergence of PPMV-1 as new velogenic variant causing Newcastle disease in chickens.