P-1559. Investigating the Effect of HLA-DRB1 Variants on T cell Response as a Contributing Risk Factor for Staphylococcus aureus Bacteremia

TL;DR

This study explores how genetic variations in HLA-DRB1 affect T cell responses to Staphylococcus aureus, potentially influencing the risk of bloodstream infection.

Contribution

The study provides in vitro evidence that HLA-DRB1 variants influence CD4+ T cell activation in response to S. aureus.

Findings

HLA-DRB1*07:01 showed higher CD4+ T cell activation compared to HLA-DRB1*04:01 and 03:01 across S. aureus concentrations.

Cytokine responses varied among HLA-DRB1 variants, though differences did not reach statistical significance.

HLA-DRB1 variation in peptide presentation may explain associations between certain alleles and S. aureus bacteremia risk.

Abstract

The impact of host genetic variability on Staphylococcus aureus bacteremia (SAB) risk is unknown. In genome-wide association studies, we identified specific HLA-class II variants associated with higher risk (HLA-DRB1*04:01 [OR = 1.121 (0.952, 1.321)] & 03:01 [OR = 1.103 (0.960, 1.269)] or lower risk (HLA-DRB1*07:01) of SAB. The aim of this study is to determine how HLA-DRB1 variants, which differ in S. aureus peptide presentation, may also differ in their ability to activate T cells and therefore protective immunity.Fig. 2Cytokine production by MOI and HLA-DRB1 variants

Cytokine production by MOI and HLA-DRB1 variants

To measure differential CD4+ T cell responses elicited by HLA-class II variation, CD4 T cells isolated from healthy donor HLA-DRB1 heterozygous peripheral blood mononuclear cells were split and separately co-cultured for 72 hrs with homozygous HLA-DRB1 matched B- lymphoblastoid cell lines that were unchallenged or pulsed overnight with dead S. aureus (USA 300) across a range of concentrations (multiplicity of infection [MOI = 0.5, 5, 50]). CD4 T cell activation (CD69+ CD25+) was assessed by flow cytometry (BD Fortessa & FlowJo) using monoclonal antibodies specific for CD4 PerCP-Cy5.5, CD69-PE, and CD25-APC and expressed as mean and standard deviation (Prism). Culture supernatants were collected for cytokine quantification (ProcartaPlex) using the Luminex 200 analyzer (xPONENT). Comparisons between MOI and HLA-DRB1 allele were determined with a two-way ANOVA (Prism).

We observed variable T cell responses to S. aureus across different HLA-DRB1 alleles. HLA-DRB1*07:01 elicited a greater fold change in CD4+ T cell activation (MOI 0.5= 2.84 ±1.5; MOI 5= 6.65 ±3.6; MOI 50= 7.96 ±4.1) compared to HLA-DRB1*04:01 (MOI 0.5= 1.48 ±0.27; MOI 5= 3.15 ±0.77; MOI 50= 4.96 ±1.7) or 03:01 (MOI 0.5 =1.95 ±0.66; MOI 5= 2.56 ±0.81; MOI 50= 2.42 ±0.86) across S. aureus concentrations. Variable CD4 T cell cytokine response to recognition of S. aureus peptide was also observed across HLA-DRB1*04:01, 03:01, and 07:01 variants. Cytokines associated with Th1 response and T cell proliferation are shown, but these markers did not reach statistical significance.

We provide in vitro evidence to suggest that HLA-DRB1 variation in S. aureus peptide presentation impacts CD4+ T cell activation and may explain the association between certain HLA-DRB1 haplotypes and SAB.

Vance G. Fowler, MD, MHS, Affinergy, Janssen, Contrafect: Advisor/Consultant|AstraZeneca; EDE; Basilea: Grant/Research Support|Debiopharm, GSK; Affinium, Basilea,: Advisor/Consultant|Destiny, Amphliphi, Armata, Akagera: Advisor/Consultant|Merck; Contrafect; Karius; Janssen: Grant/Research Support|UpToDate: Royalties|Valanbio: Stock options

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