Immunoprotective Analysis of the NFA49590 Protein from Nocardia farcinica IFM 10152 Demonstrates Its Potential as a Vaccine Candidate.

Nocardia is emerging as a serious and easily neglected pathogen in clinical practice with multidrug resistance that extends the treatment period for months or even years. This has led to the investigation of a vaccine approach to prevent Nocardia infections. However, studies on the protective proteins of Nocardia have not yet been carried out. In the present work, over 500 proteins in the supernatant of N. farcinica IFM10152 were identified by LC−MS/MS. In silico analysis of these proteins with a high content (score > 2000) predicted that NFA49590 was one of the conserved proteins in N. farcinica strains with potential antigenicity. After the rNFA49590 protein was cloned and expressed in E. coli (DE3) and purified using a Ni-NTA column, its good antigenicity was confirmed with sera from mice immunized with different Nocardia species by Western blot. Then we confirmed its ability to activate innate immunity by examining the phosphorylation status of ERK1/2, JNK, p38, and p65 and the cytokine levels of IL-6, TNF-α, and IL-10. Finally, we evaluated its immunoprotective effect in BALB/c mice, and we found that mice immunized with rNFA49590 protein exhibited high antibody titers, enhanced bacterial clearance ability, and generated robust protective effects from the N. farcinica challenge. These results offer strong support for the use of NFA49590 protein as a vaccine candidate and open the possibilities for the exploration of a large array of immunoprotective proteins.