Tegument-specific, virus-reactive CD4 T cells localize to the cornea in herpes simplex virus interstitial keratitis in humans

Abstract

Herpes stromal keratitis (HSK) is a prevalent and frequently vision-threatening disease associated with herpes simplex virus type 1 (HSV-1) infection. In mice, HSK progression occurs after viral clearance and requires T cells and neutrophils. One model implicates Th1-like CD4 T cells with cross-reactivity between the HSV-1 protein UL6 and a corneal autoantigen. HSK can be prevented by establishing specific immunological tolerance. However, HSK can also occur in T-cell receptor-transgenic X SCID mice lacking HSV-specific T cells. To study the pathogenesis of HSK in the natural host species, we measured local HSV-specific T-cell responses in HSK corneas removed at transplant surgery (n = 5) or control corneas (n = 2). HSV-1 DNA was detected by PCR in two specimens. HSV-specific CD4 T cells were enriched in three of the five HSK specimens and were not detectable in the control specimens. Reactivity with peptide epitopes within the tegument proteins UL21 and UL49 was documented. Responses to HSV-1 UL6 were not detected. Diverse HLA DR and DP alleles restricted these local responses. Most clones secreted gamma interferon, but not interleukin-5, in response to antigen. HSV-specific CD8 cells were also recovered. Some clones had cytotoxic-T-lymphocyte activity. The diverse specificities and HLA-restricting alleles of local virus-specific T cells in HSK are consistent with their contribution to HSK by a proinflammatory effect.

FIG. 1

Validation of HSV-2 protein preparations as antigens capable of driving proliferative responses by CD4 T-cell clones. The responses measured are [³H]thymidine incorporation by HSV-specific CD4 T-cell clones derived from genital HSV-2 lesions as described in Materials and Methods and previously shown to be specific for the indicated proteins. Antigen preparations made by transient transfection of Cos-7 cells with HSV gene-containing or empty vector were used at a final concentration of 1:100. UV-treated mock virus or HSV-2 was used at a final concentration of 1:100.

FIG. 2

Proliferative responses of cornea-derived CD4 T-cell clones from subject 9447 to defined HSV antigens. The measures are means of triplicate net [³H]thymidine incorporation compared to control antigen. (Top) Clone 9447.72 responds to full-length UL21 of HSV-2. Truncated proteins allow localization of the epitope to approximately amino acids 250 to 300. Synthetic peptides localize the epitope to amino acids 283 to 293. (Bottom) Clone 9447.28 responds to full-length UL49 of HSV-2. The epitope is localized to amino acids 199 to 211, corresponding to amino acids 198 to 210 of UL49 of HSV-1.

FIG. 3

Dose-response curves for proliferative responses of cornea-derived CD4 T-cell clone 9447.28 to peptide UL49 (HSV-2) 199 to 211 and clone 9447.72 to UL21 (HSV-2) 283 to 302.