Specific cytolytic T-cell responses to human CEA from patients immunized with recombinant avipox-CEA vaccine

Avipox viruses are replication-defective members of the poxvirus family. Av ipox-derived vectors such as ALVAC (canarypox) and fowlpox have the ability to infect mammalian cells, including human cells, but do not replicate. Th e first clinical trial of an avipox recombinant vaccine for patients with a dvanced carcinomas has recently been conducted using the ALVAC vector and t he human carcinoembryonic antigen (CEA) transgene (designated ALVAC-CEA; J. L. Marshall et al., J. Clin. Oncol., 17: 332-337, 1999), The T-cell respons es elicited by patients before and after vaccination with the ALVAC-CEA rec ombinants are characterized in this report. Pre- and postvaccination periph eral blood mononuclear cells (PMBCs) of the eight patients positive for HLA -class I A2 allele, were incubated with the HLA-AZ-CEA peptide CAP-1 and in terleukin 2, In no cases using prevaccination PMBCs could cultures be estab lished that had the ability to lyse C1R-A2 target cells pulsed with the CAP -1 peptide. However, T-cell cultures from seven of eight of these same pati ents, obtained from PBMCs after ALVAC-CEA vaccination, were shown to lyse C 1R-A2 cells only when pulsed with CAP-I, Moreover, all seven of these T-cel l cultures were shown to lyse allogeneic human carcinoma cell lines (SW1463 and SW480) that were both A2(+) and expressed CEA; an allogeneic tumor cel l line (LS174T) expressing CEA that was negative for A2 expression was not lysed. HLA-A2(+) and CEA(+) autologous tumor cells were also capable of bei ng lysed by CEA-specific T cells from this patient. Analysis of this CTL li ne also revealed the expression of several homing and adhesion-associated m olecules. Fluorescence-activated cell sorter analysis of the T-cell lines e stablished from patients after ALVAC-CEA vaccination revealed that most wer e CD8(+)/CD4(-), but many also had a CD8(+)/CD4(+) component. Analyses of T -cell receptor V beta usage of several of the CEA specific CTL lines showed a relatively diverse V beta pattern. These studies demonstrate for the fir st time the ability to vaccinate cancer patients with an avipox recombinant and derive T cells that are capable of lysing allogeneic and autologous tu mor cells in a MHC-restricted manner. These studies thus form the rationale to use such replication-deficient recombinant vaccines in future cancer va ccine trials.