Construction and characterization of a recombinant pseudorabies virus expressing porcine reproductive and respiratory syndrome virus GP5.

The GP5 gene of porcine reproductive and respiratory syndrome virus (PRRSV) was integrated into the TK gene locus of pseudorabies virus (PRV) vaccine strain Bartha-K61, resulting in a TK- and gE- negative recombinant PRV harboring GP5 gene, designated as rPRV-GP5. The in vitro expression of the GP5 by rPRV-GP5-infected cells was analyzed by single-step growth analysis,Western blot,and indirect immunofluorescence test. It was shown that GP5 gene can be expressed authentically in the cytoplasm of rPRV-GP5-infected cells. Compared to its parental virus, rPRV-GP5 showed no obvious difference regarding viral replication and cytopathogenic effects in several cell cultures. Four PRV-negative sheep immunized intramuscularly with 10(6.0) PFU of rPRV-GP5 were fully protected from challenge with 10(3) LD50 of highly virulent PRV S strain of porcine origin. Ten PRV- and PRRSV-negative piglets given intranasally with 10(7.0) PFU of rPRV-GP5 and challenged intranasally with 10(5.0) TCID50 of virulent PRRSV CH-1a strain at day 63 post-inoculation developed antibodies against PRRSV 3, 5, 14 days post-challenge, as revealed by indirect immunofluorescence test, enzyme-linked immunosorbent assay and virus neutralization test. The results suggest that rPRV-GP5 is capable of inducing anamnestic immune response to PRRS in inoculated animals.