PT - JOURNAL ARTICLE AU - Friederike Ebner AU - Eliot Morrison AU - Miriam Bertazzon AU - Ankur Midha AU - Susanne Hartmann AU - Christian Freund AU - Miguel Álvaro-Benito TI - CD4<sup>+</sup> T<sub>h</sub> immunogenicity of the <em>Ascaris spp</em>. secreted products AID - 10.1101/699231 DP - 2019 Jan 01 TA - bioRxiv PG - 699231 4099 - http://biorxiv.org/content/early/2019/07/14/699231.short 4100 - http://biorxiv.org/content/early/2019/07/14/699231.full AB - 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 highly complex (&gt;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+ Th cell epitopes in Ascaris suum-secreted products. This approach restricts the theoretical list of epitopes, based on affinity prediction, by a factor of ∼1200. More importantly, selection of 2 candidate peptides based on experimental evidence demonstrated the presence of epitope-reactive T cells in Ascaris-specific T cell lines generated from healthy human individuals. Thus, this stringent work pipeline identifies a human haplotype-specific T cell epitope of a major human pathogen. The methodology described represents an easily adaptable platform for characterization of highly complex pathogenic antigens and their MHCII-restriction.