Comparative Analysis of the Secretome from a Model Filarial Nematode (Litomosoides sigmodontis) Reveals Maximal Diversity in Gravid Female Parasites

Abstract

Filarial nematodes (superfamily Filarioidea) are responsible for an annual global health burden of ϳ6.3 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 humaninfective 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. Molecular & Cellular

Extracellular vesicles induce protective immunity against Trichuris muris

“…Vitellogenin proteins isolated from the ES of gravid adult female Litomosoides sigmodontis, a filarial nematode of rodents, and Ostertagia ostertagi, an intestinal nematode of cattle, have been identified as novel vaccine candidates using immunoscreening and proteomics approaches . Vitellogenin proteins have also been identified as potential vaccine candidates for ectoparasites, such as ticks and mites .…”

“…Eichenberger and colleagues also identified these proteins within T. muris EVs. 23 Although antibody responses may not reflect protection, the therapeutic value of related proteins has been demonstrated in other helminths, [34][35][36][37][38][39][40][41] suggesting that these proteins are major candidates for protective antigens.…”

“…Ostertagia ostertagi, an intestinal nematode of cattle, have been identified as novel vaccine candidates using immunoscreening and proteomics approaches. 38,39 Vitellogenin proteins have also been identified as potential vaccine candidates for ectoparasites, such as ticks and mites. [40][41][42][43] tigens before pregnancy induced protective immunity in pups, resulting in fewer brain cysts and lower mortality following congenital exposure.…”

Cervicovaginal microbiome dysbiosis is associated with proteome changes related to alterations of the cervicovaginal mucosal barrier

“…Further sample processing was performed as previously described with minor modifications. 48 In brief, protein pellets were resuspended in 25 mM ammonium bicarbonate, 0.05% (w/v) rapigest (Waters, Elstree, UK), reduced, and alkylated. Digestion was performed with proteomic-grade trypsin (Sigma-Aldrich, St Louis, MO) at a protein:trypsin ratio of 50:1.…”

Perusal of parasitic nematode ‘omics in the post-genomic era

“…An RNAseq dataset exists but has not been extensively interrogated [59]. Proteomics data across several life stages reveal transthyretin-like proteins in all developmental stages examined, as well as the identification of 302 ESP—4 of which may be novel vaccine candidates [60]. …”