38 Abstracts

B-3.2 #63

DIVERSITY OF TCR V~6 UTILIZED BY HLA IDENTICAL SIBLINGS. S G Rodriquez, HA Araujo, AH Johnson and CK Hurley, Departments of Microbiology and Pediatrics, Georgetown University Medical School, Washington DC

The MHC plays an important role in shaping the TCR repertoire during T cell thymic maturation. Indeed, studies in human have suggested that HLA genes are important in determining TCR V~ repertoire in circulating T cells; however, the effect of HLA genes on TCR repertoire util ized in antigen driven immune responses is s t i l l poorly understood. To study the contribution of HLA genes in determining the specificity of T cells in an antigen driven immune response, we have analyzed the V~-D~-J~ diversity of the utilized TCR V~6 in two tetanus toxin (t t)-specif ic T cell lines (TCL) derived from two HLA identical siblings. Although the TCL ut i l ize several TCR V~ segments, we chose V~6 for sequence analysis since i t was one of the predominant V~ segments util ized by both t t-specif ic TCL (1627 and 1628) and i t is the largest V~ subfamily. We have cloned and sequenced V~6 expressing TCR from two independent cDNA/PCR products from each TCL. Twenty four bacterial colonies from TCL 1628 were sequenced, at least 20 of them bear V~6.7a; 15/20 share the CDR3 and J~i.2 sequences (A); and 5/20 bear a second CDR3 plus J~2.5 sequence (B). The B sequence was also obtained in the other TCL (1627) in 26/31 bacterial colonies analyzed. Although the TCR V~ repertoire uti l ized by t t TCL di f fer between the two HLA identical siblings, sequence analysis of the util ized V~6 subfamily demonstrates that their corresponding V regions including CDR3 are very focused.

B-3.2 #64

HUMAN T CELL RESPONSE TO CYTOMEGALOVIRUS ANTIGENS: IMMUNOGENETIC CONSIDERATIONS. H He, CR Rinaldo and PA Morel, Departments of Medicine and Pathology, University of Pittsburgh Pittsburgh PA.

HCMV infection is a major problem in immunocompromised individuals particularly following transplantation. Present work on the HCMV vaccine is concentrating on the development of a subunit vaccine consisting of a single protein (gB). We have studied the CD4+ T cell response to selected HCMV proteins which have been shown to be immunologically relevant and have attempted to correlate this to the HLA type of the individual. The proteins studied were the two immediate early proteins (IE1 and IE2), gB, pp71 and the MHC class I homologue (UL18). Maltose binding protein fusion proteins were generated for all 5 of these proteins. Results showed that all of the fusion proteins were successfully made and could stimulate proliferative responses. T cell proliferative responses to these HCMV proteins were studied in 31 seropositive and 6 seronegative individuals. Responses were considered positive if the Acpm obtained was greater than 3SD above the mean obtained in the 6 seronegative individuals, who did not respond to any of the proteins. Of the 31 seropositive individuals, 6 responded to all 5 proteins, 21 responded to 1-4 proteins and 4 responded to none of the proteins. The most commonly recognized proteins were gB (21/31, 68%) and IE2 (22/31, 71%). IE1 and pp71 were recognized by 13/31 (42%) and the UL18 stimulated responses in 10/23 (43%). All individuals were typed for HLA-DR and DQ using DNA typing techniques. No overall associations were observed with responsiveness or unresponsiveness to any of the proteins. These results would suggest that a subunit vaccine consisting of only the gB protein would not induce protective immunity in all individuals. If one were to include the IE2 protein the response rate would rise to 87% as all of our responding subjects responded to either gB or IE2. When considering subunit vaccines it is important therefore to consider the immunogenetic background of the host.