Cloning and characterization of a novel immunogenic protein 3 (NIP3) from Brugia malayi by immuno screening of a phage-display cDNA expression library

Immunization with Brugia malayi Calreticulin Protein Generates Robust Antiparasitic Immunity and Offers Protection during Experimental Lymphatic Filariasis

Lymphatic filariasis causes permanent and long-term disability worldwide. Lack of potent adulticidal drugs, the emergence of drug resistance, and the nonavailability of effective vaccines are the major drawbacks toward LF elimination. However, immunomodulatory proteins present in the parasite secretome are capable of providing good protection against LF and thus offer hope in designing new vaccines against LF. Here, we evaluated the immunogenicity and protective efficacy of B. malayi calreticulin protein (BmCRT) using in vitro and in vivo approaches. Stimulation with recombinant BmCRT (rBmCRT) significantly upregulated Th1 cytokine production in mouse splenocytes, mesenteric lymph nodes (mLNs), and splenic and peritoneal macrophages (PMΦs). Heightened NO release, ROS generation, increased lymphocyte proliferation, and increased antigen uptake were also observed after rBmCRT exposure. Mice immunized with rBmCRT responded with increased Th1 and Th2 cytokine secretion and exhibited highly elevated titers of anti-BmCRT specific IgG at day 14 and day 28 postimmunization while splenocytes and mLNs from immunized mice showed a robust recall response on restimulation with rBmCRT. Infective larvae (L3) challenge and protection studies undertaken in Mastomys coucha, a permissive model for LF, showed that rBmCRT-immunized animals mounted a robust humoral immune response as evident by elevated levels of total IgG, IgG1, IgG2a, IgG2b, and IgG3 in their serum even 150 days after L3 challenge, which led to significantly reduced microfilariae and worm burden in infected animals. BmCRT is highly immunogenic and generates robust antiparasitic immunity in immunized animals and should therefore be explored further as a putative vaccine candidate against LF.

Comparative analysis of the secretome from a model filarial nematode (Litomosoides sigmodontis) reveals maximal diversity in gravid female parasites

Filarial nematodes (superfamily Filarioidea) are responsible for an annual global health burden of ∼6.3 million disability-adjusted life-years, which represents the greatest single component of morbidity attributable to helminths affecting humans. No vaccine exists for the major filarial diseases, lymphatic filariasis and onchocerciasis; in part because research on protective immunity against filariae has been constrained by the inability of the human-parasitic species to complete their lifecycles in laboratory mice. However, the rodent filaria Litomosoides sigmodontis has become a popular experimental model, as BALB/c mice are fully permissive for its development and reproduction. Here, we provide a comprehensive analysis of excretory-secretory products from L. sigmodontis across five lifecycle stages and identifications of host proteins associated with first-stage larvae (microfilariae) in the blood. Applying intensity-based quantification, we determined the abundance of 302 unique excretory-secretory proteins, of which 64.6% were present in quantifiable amounts only from gravid adult female nematodes. This lifecycle stage, together with immature microfilariae, released four proteins that have not previously been evaluated as vaccine candidates: a predicted 28.5 kDa filaria-specific protein, a zonadhesin and SCO-spondin-like protein, a vitellogenin, and a protein containing six metridin-like ShK toxin domains. Female nematodes also released two proteins derived from the obligate Wolbachia symbiont. Notably, excretory-secretory products from all parasite stages contained several uncharacterized members of the transthyretin-like protein family. Furthermore, biotin labeling revealed that redox proteins and enzymes involved in purinergic signaling were enriched on the adult nematode cuticle. Comparison of the L. sigmodontis adult secretome with that of the human-infective filarial nematode Brugia malayi (reported previously in three independent published studies) identified differences that suggest a considerable underlying diversity of potential immunomodulators. The molecules identified in L. sigmodontis excretory-secretory products show promise not only for vaccination against filarial infections, but for the amelioration of allergy and autoimmune diseases.

IgG subclass responses to proinflammatory fraction of Brugia malayi in human filariasis

BACKGROUND & OBJECTIVES

Earlier we demonstrated that immunization with F6, a proinflammatory molecular fraction isolated from the human filarial parasite Brugia malayi, protected the host and eliminated the infection in Mastomys coucha by a Th1/Th2 response including IgG2a antibody response. Whether F6 molecules become accessible to human host during natural course of infection and elicit similar response is not known. The present study was undertaken to determine the profile of IgG subclasses specifically reactive to F6 in different categories of bancroftian filariasis cases to infer any relationship between the levels of a particular F6-specific IgG subclass and the infection or disease status.

METHODS

Serum samples of normal individuals from filariasis non-endemic regions of India like Jammu & Kashmir, Uttarakhand, and Chandigarh [(NEN-W; n=10), healthy subjects from USA (NEN-U; n=10) and three categories of bancroftian filariasis cases from endemic areas: endemic normals (EN; n=10) with no symptoms and no microfilariae, asymptomatic microfilaremics (ASM; n=10) and chronic symptomatic amicrofilaremics (CL; n=10) were assayed for F6-specific IgG1, IgG2, IgG3 and IgG4 by ELISA using SDS-PAGE-isolated F6 fraction of B. malayi adult worms.

RESULTS

Significantly high levels of F6-specific IgG1, IgG2 and IgG3 were found in CL (P<0.001) and EN (P<0.01-0.001) bancroftian filariasis cases compared to NEN-U. Significant levels of F6-specific IgG1 (P<0.01) and IgG2 (P<0.01) but not IgG3 were found in ASM cases compared to NEN-U. The most abundant was IgG2 which when compared to NEN-U, was significantly high in CL (P<0.001) and EN cases (P<0.001), followed by ASM (P<0.01). F6-specific IgG4 response in EN, ASM and CL subjects was not significantly different from the levels of NEN-U. Among the non-endemic normals, the NEN-W subjects showed significant reactivity with IgG2 (P<0.001) but not with IgG1, IgG3 and IgG4 as compared to NEN-U subjects. IgG subclass levels were different in different categories.

INTERPRETATION & CONCLUSIONS

The high levels of F6 reactive IgG1, IgG2 and IgG3 in endemic normals and chronic symptomatic bancroftian patients, and IgG1 and IgG2 in asymptomatic microfilaraemics, suggest that F6 molecules of parasite are accessible in these subjects for IgG subclass-specific immune response and IgG2 may be related to pathogenesis. Studies using individual F6 molecules will be done to identify the molecule(s) involved in infection and protective immunity.

Selection of high affinity peptide ligands for detection of circulating antibodies in neurocysticercosis

Neurocysticercosis (NC), caused by Taenia solium, is the most common infection caused by helminthes of the human central nervous system. In this study, a random peptide phage display library was used to isolate peptide ligands as potential markers for neurocysticercosis diagnosis, because occurrence of cross-reactions with other helminthes species in the current used markers. We selected different peptides using IgG purified from pooled sera of neurocysticercosis patients. To investigate the diagnostic potential of recombinant peptides, we have tested different panels of serum samples by Phage-ELISA, and 10 phage clones strongly bound to the anti-T. solium IgGs in NC sera, with an accuracy range from 84.2% to 95%. The phage clones, NC(4)1 and NC(2)8, presented the highest sensitivity and specificity (100%), respectively, and most important, some phage clones did not react with patients' sera from Echinococcus granulosus infected patients. The validation with a competitive ELISA assay demonstrated that the selected phages could mimic T. solium epitopes and bind specifically to the pool of NC sera. Finally, the two recombinant antigens may become potential biomarkers for serodiagnosis of NC, and the Phage-ELISA demonstrated to be a very good assay, being reproducible, simple, fast, and low-cost due to its production through Escherichia coli culture, allowing a high throughput screening of NC.