Crucial epitopes of Wuchereria bancrofti abundant larval transcript recognized in natural infection

Abstract

Lymphatic filariasis is a tropical disease, with over 40 million people seriously incapacitated due to lymphangitis and elephantiasis. Over 99% of infections are caused by the nematode Wuchereria bancrofti. Expressed sequence tag (EST) analysis of filarial genome identified novel infective larval (L3) stage-specific antigen, abundant larval transcript (ALT-2), which was shown to be highly essential for parasite establishment and survival in the host. The unique structural features and immunological characteristics of ALT-2 indicate the presence of critical motifs that needs to be explored in natural human infection for understanding and management of the disease. In order to dissect the epitopes of ALT protein recognized in humans, eight peptides spanning the entire protein sequence were selected based on in-silico epitope prediction and synthesized. Analysis of the reactivity of W. bancrofti ALT-2 synthetic peptides with clinical sera (n = 40) from endemic areas identified epitopes recognized by putatively immune sera, of which two comprise the highly variable acidic domain (21-60). Interestingly, our study also revealed crucial epitopes recognized by microfilaremic (MF) sera with significantly high IgG4 isotype (p < 0.001), implicated in immunomodulation. The epitope peptides identified were highly specific for MF sera and, thus, have the potential to be exploited as diagnostic markers.

Chimeric Epitope Vaccine from Multistage Antigens for Lymphatic Filariasis

“…Among them, the antibody level was significantly ( P < 0.0001) high for the epitope regions TRX P1 & TRX P2 , followed by ALT‐2 P1, P7 and P8. ALT‐2 P2 and P3 showed significant ( P < 0.05) levels of antibody response except TGA P1 which confirms the peptides contain immunodominant B epitopes reported earlier . The antisera of TGA P1 did not show significant reactivity with its corresponding epitope in FEP.…”

“…The reactivity of FEP with peptide {PC1 (TRX P1 –TRX P2 , conjugate), TGA P1, ALT P1, P2, P3, P7 and P8 which have been screened in previous study and antisera were raised for the same in mice} antisera was carried out to check whether antipeptide antibodies were capable of recognizing the epitopes present in the whole protein (FEP) by ELISA. The results showed that antibodies induced by individual peptides were recognized by epitopes of FEP indicating the presence of corresponding peptide regions in the chimeric protein (Fig.…”

“…The reactivity of antisera raised against respective peptides {which have been screened in previous study } in mice that are present in the FEP construct was performed with FEP by indirect ELISA. The plates coated with FEP (optimum concentration 100 ng/well) were incubated with optimal dilutions (1:1000) of peptide antisera at 37 ο C for 2 h. Similarly, reactivity of FEP antisera with individual peptides was also performed, in which ELISA plates were coated with peptides (500 ng/well) and incubated with FEP antisera at 1:1000 dilution.…”

“…The epitopic regions that are identical to host proteins were reported to cause autoimmune diseases . In another study from our group, the entire B and T cell epitopes of the L3 stage‐specific ALT‐2 were mapped using systematic B and T cell assays in mice models and human samples ; also, it focused on the specific regions that contribute to the immunomodulatory functions of ALT‐2 protein, located on the immunodominant epitopes (1–50 aa and 90–128 aa) and immunosuppressive domains (55–68 aa and 73–91 aa). In this study, the immunodominant epitopes were recognized by putative immune individuals (endemic normal) and also proved to be protective in mice model, whereas the immunosuppressive domains were identified through their specific reactivity to IgG4 isotype in MF (microfilaraemics) individuals .…”

“…Based on these results of epitope mapping , a synthetic gene designated as filarial epitope protein (FEP) that encodes the B and T cell epitopes identified from three (TRX, TGA and ALT‐2) antigens, but non‐homologous to human proteins and non‐host immunosuppressive, was constructed by artificial gene synthesis. Here, we report the in vitro immunoprophylactic efficacy studies of FEP using human sera samples and the in vivo studies on filarial animal model jird.…”