Adoptive immunotherapy of feline immunodeficiency virus with autologous ex vivo-stimulated lymphoid cells modulates virus and T-cell subsets in blood.

The potential of immunotherapy with autologous virus-specific T cells to affect the course of feline immunodeficiency virus (FIV) infection was explored in a group of specific-pathogen-free cats infected with FIV a minimum of 10 months earlier. Popliteal lymph node cells were stimulated by cocultivation with UV-inactivated autologous fibroblasts infected with recombinant vaccinia viruses expressing either FIV gag or env gene products, followed by expansion in interleukin-2. One or two infusions of both Gag- and Env-stimulated cells resulted in a slow increase in FIV-specific gamma interferon-secreting T cells in the circulation of cats. In the same animals, viral set points fluctuated widely during the first 2 to 3 weeks after adoptive transfer and then returned to pretreatment levels. The preexisting viral quasispecies was also found to be modulated, whereas no novel viral variants were detected. Circulating CD4(+) counts underwent a dramatic decline early after treatment. CD4/CD8 ratios remained instead essentially unchanged and eventually improved in some animals. In contrast, a single infusion of Gag-stimulated cells alone produced no apparent modulations of infection.

AIDS vaccination studies using an ex vivo feline immunodeficiency virus model: protection from an intraclade challenge administered systemically or mucosally by an attenuated vaccine.

Feline immunodeficiency virus (FIV) infection of domestic cats represents a valuable system through which to investigate criteria for antilentiviral vaccines in a natural host species. Here, we examined whether vaccination with a strain of FIV attenuated as a result of prolonged growth in vitro could protect against a fully virulent, highly heterologous intraclade challenge. The results indicated that the vaccine virus produced a low-grade infection with no detectable pathological effects and afforded a long-lasting sterilizing immunity if the challenge was delivered intraperitoneally as cell-free virus but not against a cell-associated intravaginal challenge. In the latter case, however, the replication and pathological consequences of the challenge virus were markedly suppressed. Together with similar results obtained in rhesus monkey models, these findings should give impulse to the development of attenuated FIV vaccines to be tested in controlled studies in field cats. Field studies may provide answers to some of the existing safety concerns surrounding attenuated AIDS vaccines in humans.

Bcl2-negative MCF7 cells overexpress p53: implications for the cell cycle and sensitivity to cytotoxic drugs.

PURPOSE: Bcl2 is a mitochondrial protein endowed with cytostatic and antiapoptotic activities. In this work we studied the effects of the lack of Bcl2 in MCF7 cells. METHODS: The breast cancer cell line MCF7 (Bcl2-positive) and its derivative MCF7/50B (Bcl2-negative) were compared in terms of the level of p53 expression, doubling time and distribution of cells among the cycle phases. Sensitivities to the proapoptotic drugs cisplatinum and staurosporine were measured using a clonogenic assay and the contribution of apoptosis to cytotoxicity was determined with a mitochondrial membrane potential-sensitive dye. RESULTS: Relative to MCF7, MCF7/50B cells overexpressed p53 and slowly proliferated with a significant accumulation at G(0)/G(1) and depletion in S phase. The cytotoxicity of the DNA-damaging agent cisplatinum was decreased, while that of the protein kinase inhibitor staurosporine was increased. The induced cytotoxicity was essentially due to apoptosis and necrosis, respectively. CONCLUSIONS: These results suggest that the lack of Bcl2 accompanied by p53 overexpression affects the distribution of cells among the cell cycle phases and modifies the sensitivity to cytotoxic drugs and the type of cell death.

AIDS vaccination studies using an ex vivo feline immunodeficiency virus model: failure to protect and possible enhancement of challenge infection by four cell-based vaccines prepared with autologous lymphoblasts.

Immunogenicity and protective activity of four cell-based feline immunodeficiency virus (FIV) vaccines prepared with autologous lymphoblasts were investigated. One vaccine was composed of FIV-infected cells that were paraformaldehyde fixed at the peak of viral expression. The other vaccines were attempts to maximize the expression of protective epitopes that might become exposed as a result of virion binding to cells and essentially consisted of cells mildly fixed after saturation of their surface with adsorbed, internally inactivated FIV particles. The levels of FIV-specific lymphoproliferation exhibited by the vaccinees were comparable to the ones previously observed in vaccine-protected cats, but antibodies were largely directed to cell-derived constituents rather than to truly viral epitopes and had very poor FIV-neutralizing activity. Moreover, under one condition of testing, some vaccine sera enhanced FIV replication in vitro. As a further limit, the vaccines proved inefficient at priming animals for anamnestic immune responses. Two months after completion of primary immunization, the animals were challenged with a low dose of homologous ex vivo FIV. Collectively, 8 of 20 vaccinees developed infection versus one of nine animals mock immunized with fixed uninfected autologous lymphoblasts. After a boosting and rechallenge with a higher virus dose, all remaining animals became infected, thus confirming their lack of protection.