CD4+ Th immunogenicity of the Ascaris spp. secreted products

Abstract

Ascaris spp. is a major health problem of humans and animals alike, and understanding the immunogenicity of its antigens is required for developing urgently needed vaccines. The parasite-secreted products represent the most relevant, yet complex (>250 proteins) antigens of Ascaris spp. as defining the pathogen-host interplay. We applied an in vitro antigen processing system coupled to quantitative proteomics to identify potential CD4 + T h cell epitopes in Ascaris-secreted products. This approach considerably restricts the theoretical list of epitopes using conventional CD4 + T h cell epitope prediction tools. We demonstrate the specificity and utility of our approach on two sets of candidate lists, allowing us identifying hits excluded by either one or both computational methods. More importantly, one of the candidates identified experimentally, clearly demonstrates the presence of pathogenreactive T cells in healthy human individuals against these antigens. Thus, our work pipeline identifies the first human T cell epitope against Ascaris spp. and represents an easily adaptable platform for characterization of complex antigens, in particular for those pathogens that are not easily amenable for in vivo experimental validation.

A reverse vaccinology approach identifies putative vaccination targets in the zoonotic nematode Ascaris

“…Our reverse vaccinology analysis used all the proteins predicted in the three Ascaris proteomes. Previous in silico studies on vaccine candidate prediction in Ascaris focused exclusively on secreted proteins (Ebner et al, 2020). The workflow applied in this study allows the testing of all the proteins predicted from a genome analysis, without automatically excluding non-secreted proteins.…”

“…In a recent study, an A. lumbricoides multi-epitope vaccine candidate was developed using in silico methodology and proteins were selected based on their binding to the HLA-DRB1*07:01 and HLA-DRB1*15:01 MHC-II alleles (Kaur et al, 2021). Although these MHC-II alleles are known to recognise Ascaris antigens in humans, they only cover up to 15% of the human population in areas where human ascariasis is endemic (Ebner et al, 2020). This might prove detrimental in in vivo studies that cover population that do not have these MHC-II alleles, limiting its usefulness.…”

“…Each of the three genomes included in the analysis were predicted to have over 5,000 proteins that could be further investigated as good vaccine targets according to Vacceed, which corresponds to 25-29% of all the proteins present. As the number of secreted proteins in Ascaris is predicted to be 254 proteins (Ebner et al, 2020), this suggests that the number of potential vaccination targets might be vastly superior to the ones that are usually investigated in these species and other helminths. The final candidates are all predicted to be non-secreted proteins.…”

“…This role makes the discovery of epitopes that bind to these molecules a priority for the design of multi-epitope/subunit-based vaccines. The MHCII-IEDB tool was chosen for this purpose as it was used in selecting epitopes for vaccination assays against other nematodes and is one of the most accurate tools available (Ebner et al, 2020; Zawawi et al, 2020). A reference set of 27 different alleles was chosen due to the fact that heterogenicity throughout the human population leads to different immune responses(Ebner et al, 2020).…”

“…The MHCII-IEDB tool was chosen for this purpose as it was used in selecting epitopes for vaccination assays against other nematodes and is one of the most accurate tools available (Ebner et al, 2020; Zawawi et al, 2020). A reference set of 27 different alleles was chosen due to the fact that heterogenicity throughout the human population leads to different immune responses(Ebner et al, 2020). Thus, we wanted to selected proteins that would be able to induce a helpful immune reaction in a large portion of the population, and not just focus on one specific allele.…”