Coinfection kinetics of goatpox virus and peste-des-petits-ruminants virus in Vero cells.

Goatpox, sheeppox, and peste-des-petits-ruminants (PPR) are economically important virus diseases affecting goats and sheep, which often cause coinfection/comorbidities in the field. Coinfection with these viruses leads to enhanced infection in natural scenarios in terms of morbidities and mortalities. Currently, individual live attenuated vaccines are being used to mitigate these diseases and research on combination vaccines for these diseases is encouraging. For the preparation of combination vaccines, vaccine strains of the peste-des-petits-ruminants virus (PPRV), goatpox virus (GTPV), and sheeppox virus (SPPV) are grown separately and GTPV + PPRV are mixed for vaccination of goats, and PPRV + SPPV for sheep. Growing capripox and PPRV strains in the same cells simultaneously without the titer loss will save the time and cost of production. In the current study, we have evaluated the coinfection kinetics of capripox virus and a PPRV using a candidate GTPV vaccine strain (originally caused infection in both goats and sheep in the field) and PPRV/Sungri/96 (vaccine strain) in Vero cells. At high multiplicity of infection (MOI), PPRV was excluded from coinfection by GTPV, whereas at a low multiplicity coexistence/accommodation was observed between PPRV and GTPV without loss of the titer. The results shed light on the possibility of the production of two vaccine strains in the same cells using the coinfection model economically.

Genetic studies of terminal regions of vaccine and field isolates of capripoxviruses.

Sheeppox and goatpox are two of the most important diseases associated with significant economic loss and impact on animal trade. In spite of the use of vaccines, outbreaks are being reported on several occasions. Therefore, deciphering the host specificity and virulence of sheeppox virus (SPPV) and goatpox virus (GTPV) is important in developing effective vaccines. It is opined that genes located in the terminal regions play a major role in determining host range and/or virulence. In the present study, nine isolates (6 GTPV and 3 SPPV; included both vaccine and virulent viruses) were genetically characterized by targeting 11 genes (7 host-range and 4 virulence genes) which are located in the terminal regions of capripoxviruses. In the genetic analyses, it was observed that there are several nucleotide and amino acid signatures which are specific for either SPPV or GTPV. However, surprisingly, none of the 11 genes could be able to differentiate the vaccine and field viruses of GTPV and SPPV. Our study indicates that the genes of the terminal regions may have a role in determining the host-specificity but the involvemet in determinatin of virulence/attenuation is not certain at least for the isolates used in the current study. Therefore, it is likely that some other genes located in terminal/central regions may also play a role in determination of virulence and pathogenesis which needs to be confirmed by whole-genome sequencing of several vaccine and virulent viruses.