Investigation of T-cell responses and viral mRNA persistence in lymph nodes of pigs infected with porcine rubulavirus.

Selected lymphocyte subpopulations were studied and the distribution of viral mRNA were investigated during acute and persistent porcine rubulavirus (PoRV-LPMV) infection in Vietnamese pot-bellied pigs. Six pigs infected with PoRV-LPMV at 17 days of age exhibited clinical signs 7-10 days post-inoculation (pi). One infected piglet died 11 days pi while the other five recovered around day 13 pi and survived until euthanasia on day 277 pi. Increased numbers of CD8+, CD4+ and CD2+ T cells were detected during the acute phase of infection while CD8+ cells were elevated throughout the infection, including during the persistent stage. Specific antibodies against the haemagglutinin-neuraminidase protein of PoRV-LPMV were detected during persistent infection. Although infectious virus could not be recovered from tissues from any of the infected pigs at necropsy 277 days pi, PoRV-LPMV mRNA was detected in lymph nodes, pancreas and central nervous system using a nested polymerase chain reaction technique. Continued lymphocyte interaction with viral RNA may be an important factor in promoting cellular and humoral responses during persistent PoRV-LPMV infection.