Modulation of HLA-A*0201-Restricted T Cell Responses by Natural Polymorphism in the IE1315–324 Epitope of Human Cytomegalovirus

Abstract

Cytotoxic T lymphocytes play a central role in the control of persistent human CMV (HCMV) infection and reactivation. In healthy virus carriers, the specific CD8+ CTL response is almost entirely directed against the virion tegument protein pp65 and/or the 72-kDa major immediate early protein, IE1. Studies that included a large panel of HCMV+ donors suggested that immunorelevance of pp65 and IE1 was directly related with individual HLA haplotype difference. Nevertheless, there are no data on the incidence of HCMV natural polymorphism on virus-specific CTL responses. To assess the impact of IE1 polymorphism on CTL response, we have sequenced in 103 clinical isolates the DNA region corresponding to IE1315–324, an immunodominant epitope presented by HLA-A*0201 molecules. Seven peptidic variants were found with extensive difference in their frequencies. The response of four HLA-A*0201-restricted anti-IE1 T lymphocyte clones, which were previously generated from one donor against autologous B lymphoblastoid cells expressing a recombinant clinical variant of IE1, was then evaluated using target cells loaded with mutant synthetic peptides or expressing rIE1 variants. One of four clones, which have been sorted 19 times among 22 clones targeted against IE1315–324, recognized six of the seven tested variant epitopes. All three other clones showed distinct reactivity patterns to target cells loaded with the different mutant peptides or expressing IE1 variants. Therefore, in the HLA-A2 context, clonal expansions of anti-IE1 memory CTLs may confer a protection against HCMV successive infections and reactivations by killing cells presenting most of the naturally occurring IE1315–324 epitope variants.

T Cell Recognition Patterns of Immunodominant Cytomegalovirus Antigens in Primary and Persistent Infection

“…The apparently lower immunogenicity of IE-1 may be explained by sequence variation between natural strains of virus in each donor and the AD169 encoded IE-1 peptides used in this study. Several T cell epitopes of IE-1 contain polymorphic amino acids (29,30). Indeed in some donors there appears to be a preference for certain residues within these epitopes (such as HLA-B8-restricted ELR) with lack of recognition for others, suggesting that IE-1 responses may be underestimated in our study (unpublished observations).…”

Attenuated poxviruses generate clinically relevant frequencies of CMV-specific T cells

“…56 Exon 4 is the largest domain of IE1, and it contains most of the defined CTL epitopes. 15,17,57 The expression of IE4 protein from both IE4-MVA and UbRIE4-MVA was found to be abundant by WB analysis ( Figure 1B). Presentation of the IE4 proteins expressed in MVA was tested using an IE1 316-324 -specific T-cell clone (C.L.R.…”

Refinement of strategies for the development of a human cytomegalovirus dense body vaccine

“…1d). The C-terminal part of pp65 was chosen to fuse either the IE1 TMY determinant (IE1 (297-304) , TMYGG-ISLL) [38] or the IE1 VLE determinant (IE1 (316-324) , VLEETSVML) [39,40]. The single nonamer peptides were extended by Xanking amino acids (IE1 (288-309) and IE1 (309)(310)(311)(312)(313)(314)(315)(316)(317)(318)(319)(320)(321)(322)(323)(324)(325)(326)(327)(328) ) to ensure proper proteolytic processing.…”