Binding of the WC1 Hybrid Co-Receptor/PRR to Mycobacterium spp and Leptospira spp.​

Presenter: Lan Nguyen

Group Members: Matthew Zenon Gil

Faculty Sponsor: Janice C. Telfer

School: UMass Amherst

Research Area: Animal Science

Session: Poster Session 4, 2:15 PM - 3:00 PM, Auditorium, A88

ABSTRACT

Gamma Delta (γδ) T cells are critical mediators of immunity against numerous zoonotic pathogens for which effective vaccines remain limited. In ruminants, γδ T cells constitute a major population of circulating and tissue-resident lymphocytes and coordinate downstream immune responses upon activation. WC1, a multigenic receptor array expressed on ruminant γδ T cells, functions as a hybrid pattern recognition receptor (PRR) and T cell co-receptor. In cattle, thirteen WC1 genes (WC1-1 to WC1-13) encode proteins containing 6–11 scavenger receptor cysteine-rich (SRCR) domains capable of binding unprocessed antigen. We hypothesized that diversification within the WC1 multigenic array reflects pathogen-driven co-evolution and sought to characterize SRCR domain binding specificity toward Mycobacterium spp. and Leptospira spp.

SRCR-encoding sequences from bovine WC1 genes were cloned into a mammalian expression vector and transiently expressed in suspension HEK293F cells. Recombinant SRCR proteins were purified and quantified prior to functional analysis. Binding interactions were assessed using ELISA and whole-cell bacterial pull-down assays with fractionated or fixed Mycobacterium spp. and Leptospira spp.

Distinct SRCR domains demonstrated pathogen-specific binding profiles. Multiple btWC1-12 domains exhibited high-affinity binding to Mycobacterium spp., whereas btWC1-3 preferentially bound Leptospira spp. Protease K treatment of Mycobacterium bovis BCG Danish and Pasteur strains did not reduce btWC1-12 binding, suggesting that the ligand recognized by these SRCR domains is likely non-proteinaceous. These findings support selective pathogen recognition by WC1 SRCR domains and reinforce their role as hybrid co-receptors and PRRs in γδ T cell-mediated immunity.

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