The genetically-engineered secretory B27/Q10 chimeric molecule inhibits HLA-B27 restricted alloreactive T-lymphocytes

Intracellularly persisting bacterial infections and high association with HLA-B27 are the hallmarks of reactive arthritis. Soluble HLA-B27 molecules are induced by bacterial infection; however their biological role in arthritis is unknown. It was the aim of this study to generate soluble HLA-B27 molecule and to analyze its effect on cytotoxic HLA-B27 alloreactive CD8+ T-lymphocytes in order to better understand potential functional links between persistent infection and HLA-B27 association.

Using PCR Exons 1 through 4 of HLA-B*2705 were fused to Exon 5 of the soluble murine MHC class I variant Q10 and stably transfected into Hela-cells. Transfectants were analyzed using specific PCR, RT-PCR and intracellular and extracellular staining with anti-HLA-B27 monoclonal antibody ME1. Secretion of B27Q10 in the supernatant was examined by isoelectric focusing (IEF). The effect of B27Q10 on T-cells was analyzed using either HLA-B27- or HLA-A2-restricted alloreactive T-cells in a standard 51Cr-release assay.

PCR and RT-PCR demonstrated the DNA and mRNA of B27Q10 in the transfectants. By intracellular and extracellular staining with ME1 B27Q10-molecule was detected intracellularly but was not expressed in the cell membrane. Using IEF soluble B27Q10-molecules were found in supernatants of transfectants in a concentration of up to 1.342 microg/ml. Soluble B27QJO-molecule inhibited specifically the cytotoxicity of HLA-B27-restricted alloreactive T-cells by about 30%.

The secretory non-membrane-expressed molecule B27Q10 inhibits HLA-B27 specific T-cells. The inhibition of cytotoxic T-cells by bacteria induced soluble HLA-B27 may thus enable bacterial persistence.