Exploring the homolog of a novel proinflammatory microfilarial sheath protein (MfP) of Wuchereria bancrofti in the adult-stage bovine filarial parasite Setaria cervi

Immune targeting of filarial glutaredoxin through a multi-epitope peptide-based vaccine: A reverse vaccinology approach

Despite the efforts of global programme to eliminate lymphatic filariasis (GPELF), the threat of lymphatic filariasis (LF) still looms over humanity in terms of long-term disabilities, and morbidities across the globe. In light of this situation, investigators have chosen to focus on the development of immunotherapeutics targeting the physiologically important filarial-specific proteins. Glutaredoxin (16.43 kDa) plays a pivotal role in filarial redox biology, serving as a vital contributor. In the context of the intra-host survival of filarial parasites, this antioxidant helps in mitigating the oxidative stress imposed by the host immune system. Given its significant contribution, the development of a vaccine targeting glutaredoxin holds promise as a new avenue for achieving a filaria-free world. Herein, multi-epitope-based vaccine was designed using advanced immunoinformatics approach. Initially, 4B-cell epitopes and 6 T-cell epitopes (4 MHC I and 2 MHC II) were identified from the 146 amino acid long sequence of glutaredoxin of the human filarid, Wuchereria bancrofti. Subsequent clustering of these epitopes with linker peptides finalized the vaccine structure. To boost TLR-mediated innate immunity, TLR-specific adjuvants were incorporated into the designed vaccine. After that, experimental analyses confirm the designed vaccine, Vac4 as anefficient ligand of human TLR5 to elicit protective innate immunity against filarial glutaredoxin. Immune simulation further demonstrated abundant levels of IgG and IgM as crucial contributors in triggering vaccine-induced adaptive responses in the recipients. Hence, to facilitate the validation of immunogenicity of the designed vaccine, Vac4 was cloned in silico in pET28a(+) expression vector for recombinant production. Taken together, our findings suggest that vaccine-mediated targeting of filarial glutaredoxin could be a future option for intervening LF on a global scale.

In-silico evidences on filarial cystatin as a putative ligand of human TLR4

Cystatin is a small molecular weight immunomodulatory protein of filarial parasite that plays a pivotal role in downregulating the host immune response to prolong the survival of the parasite inside the host body. Hitherto, this protein is familiar as an inhibitor of human proteases. However, growing evidences on the role of cystatin in regulating inflammatory homeostasis prompted us to investigate the molecular reasons behind the explicit anti-inflammatory trait of this protein. We have explored molecular docking and molecular dynamics simulation approaches to explore the interaction of cystatin of Wuchereria bancrofti (causative parasite of human filariasis) with human Toll-like receptors (TLRs). TLRs are the most crucial component of frontline host defence against pathogenic infections including filarial infection. Our in-silico data clearly revealed that cystatin strongly interacts with the extracellular domain of TLR4 (binding energy=-93.5 ± 10 kJ/mol) and this biophysical interaction is mediated by hydrogen bonding and hydrophobic interaction. Molecular dynamics simulation analysis revealed excellent stability of the cystatin-TLR4 complex. Taken together, our data indicated that cystatin appears to be a ligand of TLR4 and we hypothesize that cystatin-TLR4 interaction most likely to play a key role in activating the alternative activation pathways to establish an anti-inflammatory milieu. Thus, the study provokes the development of chemotherapeutics and/or vaccines for targeting the cystatin-TLR4 interaction to disrupt the pathological attributes of human lymphatic filariasis. Our findings are expected to provide a novel dimension to the existing knowledge on filarial immunopathogenesis and it will encourage the scientific communities for experimental validation of the present investigation. Communicated by Ramaswamy H. Sarma.

Therapeutic Efficacy of Anti-Bestrophin Antibodies against Experimental Filariasis: Immunological, Immune-Informatics and Immune Simulation Investigations

Lymphatic filariasis (LF) is a debilitating parasitic disease caused by filarial parasites and it is prevalent across the underprivileged population throughout the globe. The inadequate efficacy of the existing treatment options has provoked the conception of alternative strategies, among which immunotherapy is steadily emerging as a promising option. Herein, we demonstrate the efficacy of an antibody-based immunotherapeutic approach in an experimental model of filariasis, i.e., Wistar rat infected with Setaria cervi (a model filarial parasite). The polyclonal antibodies were raised against filarial surface antigen bestrophin protein (FSAg) in mice using the purified Wuchereria bancrofti FSAg. The adoptive transfer of anti-FSAg antibody-containing serum resulted in the significant reduction of parasite burden in filaria-infected rats. Intriguingly, anti-FSAg sera-treated animals also displayed a reduction in the level of proinflammatory cytokines as compared to the infected but untreated group. Furthermore, our in silico immunoinformatics data revealed eight B-cell epitopes and several T-cell epitopes in FSAg and these epitopes were linked to form a refined antigen in silico. The immune simulation suggested IgM and IgG1 as the predominant immunoglobulins induced in response to FSAg. Taken together, our experimental and simulation data collectively indicated a therapeutic potential of anti-FSAg sera against LF.

Wuchereria bancrofti filaria activates human dendritic cells and polarizes T helper 1 and regulatory T cells via toll-like receptor 4

Interaction between innate immune cells and parasite plays a key role in the immunopathogenesis of lymphatic filariasis. Despite being professional antigen presenting cells critical for the pathogen recognition, processing and presenting the antigens for mounting T cell responses, the dendritic cell response and its role in initiating CD4+ T cell response to filaria, in particular Wuchereria bancrofti, the most prevalent microfilaria is still not clear. Herein, we demonstrate that a 70 kDa phosphorylcholine-binding W. bancrofti sheath antigen induces human dendritic cell maturation and secretion of several pro-inflammatory cytokines. Further, microfilarial sheath antigen-stimulated dendritic cells drive predominantly Th1 and regulatory T cell responses while Th17 and Th2 responses are marginal. Mechanistically, sheath antigen-induced dendritic cell maturation, and Th1 and regulatory T cell responses are mediated via toll-like receptor 4 signaling. Our data suggest that W. bancrofti sheath antigen exploits dendritic cells to mediate distinct CD4+ T cell responses and immunopathogenesis of lymphatic filariasis.