Secreted protein NFA47630 from Nocardia farcinica IFM10152 induces immunoprotective effects in mice

Nocardia is emerging as a common and easily neglected cause of both healthcare- and occupation-associated infections worldwide, however, human vaccines for Nocardia prevention are not yet available. In this study, we aimed to evaluate the immunoprotective effect of the NFA47630 protein, a secreted protein abundant in the N. farcinica IFM10152 supernatant.

Conservation and characteristics of nfa47630 were analyzed by PCR and bioinformatics. Then recombinant NFA47630 protein was cloned, expressed and purified for further antigenicity analysis. Subsequently, the ability to activate innate immunity was evaluated by examining the phosphorylation status of the MAPK signaling pathway and cytokine levels. Finally, the protective effect was evaluated on rNFA47630-immunized mice.

nfa47630 was conserved in N. farcinica strains with good antigenicity. The rNFA47630 protein was expressed under the optimal conditions of 0.2 mM IPTG, 28 °C, and it can be recognized by anti-N. farcinica and anti-N. cyriacigeorgica sera, but not anti-N. asteroids, anti-N. brasiliensis, anti-N. nova and anti-Mycobacterium bovis sera. It can upregulate the phosphorylation status of ERK, JNK, P38 and the cytokine levels of TNF-α, IL-10, IL-12, and IFN-γ. In addition, mice immunized with rNFA47630 protein exhibited higher antibody titers, greater bacterial clearance ability, milder organ infection, and higher survival rates than PBS-immunized mice.

Our data demonstrate that NFA47630 is a potential vaccine candidate for defending against N. farcinica infection.