Giardia duodenalis Assemblage B Proteome

Giardia duodenalis a species-complex of common gastrointestinal protists of major medical and veterinary importance. This complex is currently subclassifed as ‘Assemblages’, with Assemblage A and B infective to humans. To date, post-genomic proteomics are derived exclusively from Assemblage A, biasing understanding of these parasites’ biology. This bias is particularly notable, as Assemble B is the more prevalent cause of human infections. To address this gap, we quantitatively analysed proteomes of the intestinal ‘trophozoite’ stage of three Assemblage B isolates, including the genome reference (GS/M) and two clinical isolates (BRIS/91/HEPU/1279 and BRIS/92/HEPU/1487), during in vitro axenic culture. We used spectrum-to-peptide matching metrics to infer currently unknown intra-assemblage variation. We identified and quantified over 3000 proteins in the GS isolate, but demonstrated significant isolate-dependent losses in peptide and protein identifications in non-reference isolates, suggesting significant intra-assemblage variation. We also explore differential protein expression between in vitro cultured subpopulations enriched for dividing relative to feeding cells. This data is an important proteomic baseline for Assemblage B, and highlights unique differences heretofore avoided in post-genomic Giardia proteomics.