Protection against filarial infection by 45-49 kDa molecules of Brugia malayi via IFN-γ-mediated iNOS induction

Nitric oxide (NO) mediated mechanisms have been implicated in killing of some life-stages of Brugia malayi/Wuchereria bancrofti and protect the host through type 1 responses and IFN-γ stimulated toxic mediators' release. However, the identity of NO stimulating molecules of the parasites is not known. Three predominantly NO-stimulating SDS-PAGE resolved fractions F8 (45.24-48.64 kDa), F11 (33.44-38.44 kDa) and F12 (28.44-33.44 kDa) from B. malayi were identified and their proteins were analyzed by 2-DE and MALDI-TOF/TOF. Tropomyosin, calponin and de novo peptides were identified by 2-DE and MALDI-TOF/TOF in F8 and immunization with F8 conferred most significant protection against L3-initiated infection in Mastomys coucha. Immunized animals showed upregulated F8-induced NO, IFN-γ, TNF-α, IL-1β, IL-10, TGF-β release, cellular proliferative responses and specific IgG and IgG1. Anti-IFN-γ, anti-TNF-α, and anti-IL-1β significantly reduced F8-mediated NO generation and iNOS induction at protein levels. Anti-IFN-γ treated cells showed maximum reduction (>74%) in NO generation suggesting a predominant role of IFN-γ in iNOS induction. In conclusion, the findings suggest that F8 which contains tropomyosin, calponin and de novo peptides protects the host via IFN-γ mediated iNOS induction and may hold promise as vaccine candidate(s). This is also the first report of identification of tropomyosin and calponin in B. malayi.