A Systematic Analysis of Pollen Transcriptomes from Plant Allergens Reveals Conserved Targets of Immune Responses

Abstract

We have recently identified a set of novel antigens in Timothy grass (TG) pollen using an unbiased, integrated transcriptomic and proteomic analysis, and have shown that these antigens are prominent targets of T-cell responses. Here we determined the degree of conservation of these epitopes across multiple plant species that could be targets of cross-reactive T-cells. This would make them potential candidates for pan-pollen immunotherapy approaches. RNA was extracted and sequenced from nine plant allergens (4-grass, 2-weed, and 3-tree pollens). Peptides from TG were examined for conservation across these pollens using sequence alignments, and conservation was correlated with immunogenicity. T-cell epitope cross-reactivity was determined by generating short term mono-specific T-cell lines and assessing their response across the panel of pollen extracts in IL-5 ELISPOT assays. We find that conservation of a peptide across pollens based on transcriptomic analysis correlates with the likelihood that it will elicit Th2 responses in allergic donors. Furthermore, If TG extract elicited high responses after culture with peptide, so did those extracts in which the peptide is conserved. Substitutions of 3 or more residues in the peptide greatly reduced the response. Thus, conserved peptides (with 2 or less substitutions) are capable of inducing cross-reactive T-cell immune responses. We have identified peptides that are significantly conserved across multiple plant allergen species and stimulate cross-reactive T-cells. It is possible that inducing tolerance against these peptides may modulate the allergic immune response against a broad range of grass and pollen allergens.