Prokaryotic expression and immune effect evaluation of PRRSV nonstructural protein NSP1

Abstract:

Objective To express the recombinant nonstructural protein NSP1 of the porcine reproductive and respiratory syndrome virus (PRRSV) strain NADC 30, evaluate its immune effect in mice, and explore the potential value of the nonstructural proteins of PRRSV as vaccine antigens.Methods The prokaryotic expression system was used to express NSP1 of NADC30. After purification, the expression and antibody reactivity of NSP1 in vitro were identified by Western blotting. After mice were immunized with NSP1, the levels of cellular and humoral immunity induced by NSP1 were measured. The level of neutralizing antibody induced by NSP1 was evaluated by the virus neutralization assay.Results The target gene of NSP1 was connected to the Escherichia coli pET-28a vector for prokaryotic expression. Western blotting identified that the recombinant protein NSP1 was correctly expressed and had antibody reactivity. After mice were immunized with the confirmed recombinant protein NSP1, the levels of interferon (IFN)-γ and tumor necrosis factor (TNF)-α in the spleen lymphocytes of mice were elevated, and cellular immunity was stimulated. At the same time, the recombinant protein NSP1 significantly improved the proliferation of spleen lymphocytes in mice. ELISA results suggested that the level of specific antibodies in the serum rose after immunization. Further analysis of the specific antibody subtypes (IgG2a and IgG1) produced showed that the type of immunity stimulated by recombinant NSP1 was biased to Th2 humoral immunity. In addition, the virus neutralization assay showed that the recombinant protein NSP1 had a good virus neutralization ability, with the neutralization titer of 1:37 on day 28 and 1:31 on day 42, which were significantly higher than those of the PBS control group and had no difference from those of the commercial vaccine group.Conclusion The recombinant nonstructural protein NSP1 of PRRSV can stimulate cellular and humoral immunity in mice and has a good virus neutralization ability, which provides a new idea for the development of next-generation PRRSV vaccines.