We have achieved this by deleting an essential gene from the PPRV genome and providing the required protein in trans in a helper cell line. We have therefore sought to create a biosafe system to produce virus-like particles (VLPs) which would appear as virus in diagnostic tests and which could be produced in good yield. The H protein requires mammalian glycosylation for proper folding, so baculovirus-expressed protein is not adequate. For larger scale and simplified production of antigen for ELISA, it would be useful to be able to prepare a suitable antigen without the need for actual virus. In many countries, this requires a containment laboratory for the virus culture, and continued application of biosecurity restrictions, including restrictions on the transport of the ELISA kits, even if the virus preparation is subsequently inactivated, e.g. The latter system presents a problem in the need to grow and purify live virus, even if it is only a vaccine strain of the virus. Although there are still laboratories using agarose gel immunodiffusion (AGID) techniques, the primary method of testing for anti-PPRV antibodies is competition ELISA (cELISA), and the antibodies tested for are either those recognising the viral nucleocapsid protein (N), in which the ELISA antigen is a bacterially expressed protein, or those recognising the viral surface glycoprotein H, where whole virus is used as the ELISA antigen. In addition, vaccination programs are increasingly being supported by post-vaccination serum surveillance to measure the effectiveness of the local vaccination process. The most commonly used laboratory tests are those for anti-PPRV antibodies, partly on cost grounds, and partly because a lot of the effort in infected countries is still on tracking the prevalence of disease through identifying flocks/herd which have been exposed to the virus, rather than acute response diagnostics on animals showing clinical signs. Several alternative DIVA vaccines have been proposed based on recombinant viruses, but none is yet in field use. All the vaccines currently in use are attenuated strains of PPRV these vaccines are effective, though they do not provide a DIVA (Distinguishing Infected from Vaccinated Animals) capability, since they provide what is essentially a totally subclinical infection with PPRV, and the antibody signatures of vaccinated and previously-infected animals are identical. ĭisease control is mostly achieved through the use of clinical or laboratory-based diagnosis coupled with vaccination. Control of this disease has recently become a major international goal, marked by the adoption in 2014 of a resolution by the World Organisation for Animal Health (OIE) to establish a control programme with a view to eventual eradication of the disease. The disease is caused by a virus, PPR virus (PPRV), which is a morbillivirus, related to the human pathogen measles virus (MV), as well as other animal pathogens such as canine distemper virus (CDV) and the now-eradicated rinderpest virus (RPV). Peste des petits ruminants (PPR) is a severe disease of sheep and goats which has been spreading extensively over the past two decades, and is now found widely distributed through large parts of Africa, the Middle East and Asia it poses an increasing threat to poor livestock keepers, primarily in developing countries.
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