Human Peripheral Blood T Cells, Monocytes, and Macrophages Secrete Macrophage Inflammatory Proteins 1α and 1β following Stimulation with Heat-InactivatedBrucella abortus

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Abstract
Heat-killedBrucella abortus(HBa) has been proposed as a carrier for therapeutic vaccines for individuals with immunodeficiency, due to its abilities to induce interleukin-2 (IL-2) and gamma interferon (IFN-γ) in both CD4+and CD8+T cells and to upregulate antigen-presenting cell functions (including IL-12 production). In the current study, we investigated the ability of HBa or lipopolysaccharide isolated from HBa (LPS-Ba) to elicit β-chemokines, known to bind to the human immunodeficiency virus type 1 (HIV-1) coreceptor CCR5 and to block viral cell entry. It was found that human peripheral blood mononuclear cells secreted β-chemokines following stimulation with HBa, and this effect could not be blocked by anti-IFN-γ neutralizing antibodies. Among purified T cells, macrophage inflammatory protein 1α and 1β (MIP-1α and MIP-1β, respectively) secretion was observed primarily in human CD8+T cells. The kinetics of β-chemokine induction in T cells were slow (3 to 4 days). The majority of β-chemokine-producing CD8+T cells also produced IFN-γ following HBa stimulation, as determined by triple-color intracellular staining. A significant number of CD8+T cells contained stored MIP-1β that was released after HBa stimulation. Both HBa and LPS-Ba stimulated high levels of MIP-1α and MIP-1β production in elutriated monocytes and even higher levels in macrophages. In these cells, β-chemokine mRNA was upregulated within 30 min and proteins were secreted within 4 h of stimulation. The monocyte- and macrophage-derived β-chemokines were sufficient to block CCR5-dependent HIV-1 envelope-mediated cell fusion. These data suggest that, in addition to the ability of HBa to elicit antigen-specific humoral and cellular immune responses, HBa-conjugated HIV-1 proteins or peptides would also generate innate chemokines with antiviral activity that could limit local viral spread during vaccination in vivo.