Molecular Definition Of Filarial And Related Nonfilarial Genes And Proteins

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

In the past year based on long-read sequencing, we have chromosome level assemblies and telomere-to-telemere genomic data for L. loa, W. bancrofti, S. stercoralis, and close to fully annotated genomes for Baylisascaris procyonis, Toxocara cati and Toxocara canis. Additional sequencing of Trichinella spp (T1 and T7) has been done to better understand their biology. We have utilized the genomic data as the backdrop for performing a large number of proteomic and transcriptomic studies. We have exploited informatic pipelines to identify tandomly and/or interspersed repeats within the genomes of Angiostrongylus cantonensis, L. loa, W. bancrofti, S. stercoralis, Trypanosoma cruzi, various Schistoma spp and more recently T. cati, T. canis, B. procyonis. We have configured qPCR assays for each of these identified targets and have improved the limits of detection in validated assays. In addition we have been able to improve the diagnostic sensitivity of detecting human leishmania infections and developed a pan-leishmania qPCR assay. Most of these have been shown to be useful for the diagnosis of these infections in appropriate patient samples and for following response to therapy. We recently characterized the N-linked and glycosphingolipid derived glycans of the parasitic nematode Brugia malayi and revealed the presence of various antigenic structures that triggered immunoglobulin G (IgG) responses in infected individuals. We assessed the specificity of IgG binding to these glycan antigens and identified a restricted subset of cross-reactive glycans across the filarial infections. Interestingly, in Brugia malayi infected individuals, we observed a marked reduction in particular in IgG2 to parasite glycans post-treatment with anthelminthic, suggesting a promising potential for diagnostic applications. Unraveling cross-reactivity of anti-glycan IgG responses in filarial nematode infections. Interleukin (IL)-10 is the primary cytokine driving the modulation of the host response in filarial infections. We identified a short sequence - Bm5339, that has structural similarities to the human IL-10 functional dimer. Sequence comparisons revealed that other filarial parasites possess Bm5539 orthologues. Using recombinant Bm5539 in a modified Luciferase Immunoprecipitation System assay, we confirmed that both the truncated and full-length forms of the protein can bind to human IL-10R1. Truncated Bm5539 could inhibit human IL-10-driven phosphorylation of STAT3, thereby demonstrating that Bm5539 acts as an IL-10 antagonist, most likely through competitive binding to the receptor. We provide a structural basis for these observations using computational modeling and simulations. This parasite-encoded cytokine receptor antagonist provides an additional lens through which parasite-induced modulation of the host immune response can be examined. We have previously identified 3 proteins derived from O. volvulus, that are present in detectable amounts in sera/plasma of patients with onchocerciasis. Polyclonal and monoclonal antibodies to each of these proteins have been raised and used to configure sandwich immunoassays for their detection in patient samples. These immunoassays have been sent to laboratories around the world for validation prior to commercialization. A single W. bancrofti antigen (termed Wb5) was identified in a screen to provide additional sensitivity to already extant immunoassays based on Wb123 IgG4 detection. While each protein showed greater than 99% specificity, their sensitivity ranged between 50-70%. When combined, their sensitivity for active infection was 85%. This should allow for potential widespread use for post MDA surveillance around the world.