Role of viral proteins and concanavalin A in in vitro replication of pseudorabies virus in porcine peripheral blood mononuclear cells.

We examined the capability of pseudorabies virus (PRV) to replicate in vitro in porcine peripheral blood mononuclear cells (PBMC) and characterized the phenotype of infected cells. In addition, we investigated whether inactivation of various PRV proteins or the expression of a foreign gene affected this replication. Finally, we studied the replication of PRV strains in concanavalin A (Con A)-stimulated lymphocytes. The replication of PRV mutants with inactivated glycoproteins gE or gG, thymidine kinase (TK), ribonucleotide reductase (RR) or US3-encoded protein kinase (PK), and the replication of PRV vector strains expressing the envelope glycoprotein E1 of hog cholera virus (HCV) were studied. By adherence of PBMC to plastic, monocytes and lymphocytes were largely separated. Infected monocytes were analysed with an immunostaining monolayer assay and infected lymphocytes were analysed with immunofluorescence staining and flow cytometry. We found that the wild-type NIA-3 virus replicated in both lymphocyte and monocyte cultures. NIA-3 infected relatively more monocytes (> 90%) than non-adherent B cells (46-65%) and T cells (17-28%); approximately equal numbers of CD4+ and CD8+ T cells were infected. Although E1 is probably involved in adsorption of HCV to host cells, the expression of E1 by PRV vector strains did not change the level of replication. Inactivation of TK and RR, but not inactivation of gE, gG or PK, severely affected the replication in both monocytes and lymphocytes. Con A stimulation of lymphocytes restored the reduced replication of the TK mutant, but not of the RR mutant. Moreover, Con A stimulation of lymphocytes reduced the replication of the wild-type NIA-3 virus. We concluded that both viral TK and RR activity are important for efficient replication of PRV in resting lymphocytes. Furthermore, Con A-stimulated lymphocytes can restore the viral TK defect and PRV replication can also be influenced by cellular metabolism.