Detection of closely related Picobirnaviruses among diarrhoeic children in Kolkata: evidence of zoonoses?

The genus, Picobirnavirus (PBV), Spanish 'pico'='small', birna for 'bipartite RNA' genome, belongs to the family Picobirnaviridae under the proposed order Diplornavirales. PBV infections have been reported from diarrhoeic animal species and humans as well as from asymptomatic cases. The detection of Picobirnaviruses (PBVs) in diarrhoeic faecal specimens from children aged <5 years, suggestive of zoonotic transmission is being reported. 23 Picobirnavirus positive faecal specimens were detected by polyacrylamide gel electrophoresis (PAGE) and silver staining from a set of 1112 faecal specimens collected from an urban slum community in Kolkata between July and October 2007. The Picobirnaviruses showed either large profile (n=22) or small profile (n=1) for their bisegmented genomic double-stranded RNA (dsRNA). 13/23 positives were amplified by reverse transcription polymerase chain reaction (RT-PCR) as 201bp amplicon with genogroup I primers [PicoB25(+) and PicoB43(-) specific for RNA dependent RNA polymerase (RdRp) gene fragment encoded by genomic segment 2] and seven amplicons were sequenced [GPBV1-5, 7 and 8]. Sequence analyses showed that four PBV strains [GPBV1-3 and 8] resembled different clones of porcine PBV strains (D4, D6 and C10) reported in 2008 from Hungary and two PBV strains [GPBV4 and 7] resembled human PBV strains (P597, Kolkata and 2-GA-91, USA) with the maximum nucleotide (nt) identity ranging from 78% to 92%. One strain GPBV5 clustered with human PBVs and porcine PBVs that were reported from Hungary, Venezuela and Argentina showing close homology to human-like PBVs. Therefore, the close monitoring of their global spread as well as in-depth molecular characterization is essential for better understanding of emerging PBV strains.