Cytotoxic T lymphocyte and antibody responses generated in rhesus monkeys immunized with retroviral vector-transduced fibroblasts expressing human immunodeficiency virus type-1 IIIB ENV/REV proteins.

The immune response against human immunodeficiency virus type-1 (HIV-1) is believed to play a role in controlling the early stages of disease progression. The cellular immune response, in particular cytotoxic T lymphocyte (CTL) activity, may be important for eliminating virally infected cells in HIV-1-infected individuals. Genetic immunization using retroviral vectors provides an effective means of introducing antigens into the antigen presentation pathways for T cell stimulation. A nonreplicating, amphotropic murine retroviral vector containing the HIV-1 IIIB env gene has been used to transduce primary rhesus monkey fibroblasts for the expression of HIV-1 antigenic determinants. Rhesus monkeys were immunized with four doses of either vector-transduced autologous fibroblasts (VTAF) expressing the HIV-1 IIIB ENV/REV proteins or nontransduced autologous fibroblasts (NTAF) administered at 2-week intervals. The animals were evaluated for both the induction of HIV-1-specific immune responses and potential toxicity associated with this ex vivo treatment. The VTAF-immunized monkeys generated CTL responses specific for HIV-1 ENV/REV expressing autologous target cells, whereas, NTAF-immunized monkeys showed negligible CTL activity. The cytotoxic activity was mediated by CD8+, major histocompatibility complex (MHC)-restricted CTL. In addition, antibody responses directed against the HIV-1 gp120 protein were also detected in the sera of VTAF-immunized monkeys. Clinical and histopathological evaluation of immunized monkeys showed no evidence of significant adverse events. Several animals that received either VTAF or NTAF had detectable anti-cytoplasmic antibodies, but were not positive for anti-nuclear antibodies or rheumatoid factor. Subsequent evaluation of renal, synovial, and hepatic tissue samples from these monkeys revealed no autoimmune disease-associated lesions. This study demonstrates the safety and ability of autologous retroviral vector-transduced cells expressing HIV-1 IIIB ENV/REV proteins to stimulate immune responses in a non-human primate model, and provides a basis for this form of genetic immunization in HIV-infected humans.

A new murine CD4+ T cell subset with an unrestricted cytokine profile.

CD4+ T cell clones were derived from mice immunized to keyhole limpet hemocyanin to characterize the cytokine profiles of newly isolated clones. Surprisingly, several of the clones had an unrestricted profile, producing IL-2, IL-3, IL-4, IFN-gamma, and TNF after either Con A or Ag stimulation. The coproduction of IL-2 and IL-4 was confirmed at the mRNA level. Subclones were derived which contained RNA transcripts for, as well as secreted, both IL-2 and IL-4 thus confirming the clonality of the original T cell clones. CD4+ T cell clones that expressed an unrestricted cytokine profile upon Con A stimulation were also isolated from mice immunized to other Ag (hen egg lysozyme, OVA, or type II collagen). These data indicate that CD4+ T cell clones newly isolated from immunized mice do not necessarily segregate into the Th1 and Th2 subsets. We propose this new murine CD4+ cell subset with an unrestricted pattern of cytokine production be called Th0.