A mouse model for study of tumor immunology

Mice transgenic for neu, the rat homologue of human erbB-2, under the control of the mouse mammary tumor virus (MMTV) promoter, spontaneously develop mammary neoplasms expressing high levels of the p185neu protein. Intramuscular injection of DNA expression vectors encoding the full length neu cDNA (pNeuN) or truncated neu cDNA could induce protective immunity in FVB/N mice (H-2q) against adoptive transfer of Tg1-1 cells, a syngenic neu-expressing tumor cell line. Co-injection of a plasmid encoding interleukin-2 (designated pIL-2) augmented the efficacy for inducing protective immunity. However, intramuscular injection of pNeu N with or without co-injection of pIL-2 did not induce protective immunity against Tg1-1 cells in FVB/N c-neu transgenic mice (H-2q).;Intradermal injection of DNA expression vectors induced significantly stronger antibody response compared to intramuscular injection and studies in H-2 congenic mice revealed that animals with the H-2d haplotype generated higher titers of specific antibodies against p185erbB-2 after pErbB-2 (a DNA expression vector encoding the full length human erbB-2 cDNA) immunization than animals with the H-2q haplotype. F 1 mice (H-2qxd) of FVB/N c-neu transgenic mice (H-2 q) crossed with BALB/c (H-2d) mice not only generated anti-p185c-erbB-2 antibodies but also autoantibodies against self p185neu protein when immunized in dermis with pErbB-2. In contrast, immunization with pNeuN did not induce anti-p185 neu antibodies. These results indicate that the major histocompatibility complex can influence the relative immune response to a specific antigen. Also, plasmids encoding heterologous antigens may be better suited than plasmids encoding self proteins for inducing autoimmunity. However, the anti-p185 neu antibodies induced in F1 c-neu transgenic mice was not sufficient to prevent or delay spontaneous mammary tumor development.;Cytotoxic T lymphocytes (CTL) use two pathways to destroy target cells, the Fas-mediated pathway and the granule-mediated pathway. Reduction in mitochondrial transmembrane potential is found to be an early, irreversible step in Fas-independent killing of target cells by CD8+ cytotoxic T lymphocytes (CTL). Reduction in DeltaPsim and cytoplasmic protein release in Fas-independent CTL-killing are inhibited by the lamin protease inhibitor N-carbobenzoxy-Ala-Pro-Phe chloromethyl ketone (z-APF-cmk), but not by caspase inhibitors, such as N-carbobenzoxy-Val-Ala-Asp fluoromethyl ketone (z-VAD-fmk) or N-carbobenzoxy-Asp-Glu-Val-Asp fluoromethyl ketone (z-DEVD-fmk), respectively. This contrasts with Fas-mediated apoptosis, in which the reduction in DeltaPsim can be inhibited by z-VAD-fmk or z-DEVD-fmk. Monitoring for target-cell DeltaPsim can provide for a sensitive and rapid assay for CTL activity.