Host factors and the pathogenesis of HIV-induced disease

100

Opportunistic infections are common in HIV-infected patients; they activate HIV replication and contribute to disease progression. In the present study we examined the role of Toll-like receptor 2 (TLR2) and TLR9 in HIV-long terminal repeat (HIV-LTR) trans-activation and assessed whether TLR4 synergized with TLR2 or TLR9 to induce HIV replication. Soluble Mycobacterium tuberculosis factor (STF) and phenol-soluble modulin from Staphylococcus epidermidis induced HIV-LTR trans-activation in human microvessel endothelial cells cotransfected with TLR2 cDNA. Stimulation of ex vivo spleen cells from HIV-1 transgenic mice with TLR4, TLR2, and TLR9 ligands (LPS, STF, and CpG DNA, respectively) induced p24 Ag production in a dose-dependent manner. Costimulation of HIV-1 transgenic mice spleen cells with LPS and STF or CpG DNA induced TNF-α and IFN-γ production in a synergistic manner and p24 production in an additive fashion. In the THP-1 human monocytic cell line stably expressing the HIV-LTR-luciferase construct, LPS and STF also induced HIV-LTR trans-activation in an additive manner. This is the first time that TLR2 and TLR9 and costimulation of TLRs have been shown to induce HIV replication. Together these results underscore the importance of TLRs in bacterial Ag- and CpG DNA-induced HIV-LTR trans-activation and HIV replication. These observations may be important in understanding the role of the innate immune system and the molecular mechanisms involved in the increased HIV replication and HIV disease progression associated with multiple opportunistic infections.

Section: Discussionmentioning

confidence: 99%

Toll-Like Receptor 2 (TLR2) and TLR9 Signaling Results in HIV-Long Terminal RepeatTrans-Activation and HIV Replication in HIV-1 Transgenic Mouse Spleen Cells: Implications of Simultaneous Activation of TLRs on HIV Replication

Equils

Schito

Karahashi

et al. 2003

100

“…1). One component of host defense, the chemokine system, has been appreciated to have a major role in HIV disease, following the discoveries that CCL3, CCL4, and CCL5 could suppress infection by some strains of HIV-1 and that CXCR4 and CCR5 were the major coreceptors that, along with CD4, are necessary for HIV-1 to enter cells (reviewed in Ref.…”

mentioning

confidence: 99%

Roles for CXC Chemokine Ligands 10 and 11 in Recruiting CD4+ T Cells to HIV-1-Infected Monocyte-Derived Macrophages, Dendritic Cells, and Lymph Nodes

Foley

Solow

et al. 2005

We investigated roles for chemoattractants in dissemination of HIV-1 by examining the induction of T cell-active chemokines in HIV-1-infected human monocyte-derived macrophages and dendritic cells. Of the 12 chemokines analyzed, mRNAs for two, CXCL10 and CXCL11, ligands for the chemokine receptor CXCR3, were up-regulated in both cell types upon infection by HIV-1. Induction of these chemokine genes in infected cultures was dependent on both viral entry and reverse transcriptase activity, but not on the HIV-1 envelope glycoprotein. Conditioned medium from infected cells was chemotactic for freshly isolated human CD4+ T cells, and chemotaxis was abolished by pretreatment with an Ab against CXCR3. A lymph node from an HIV-1-infected individual expressed CXCL10 and CXCL11 mRNAs in the paracortex, including venules, as detected by in situ hybridization, whereas neither mRNA was detected after highly active antiretroviral therapy. Because CCR5 on CD4+ T cells is found predominantly on cells that also express CXCR3, these data implicate CXCL10 and CXCL11 in the recruitment of susceptible T cells to HIV-1-infected lymph nodes, macrophages, and dendritic cells. This recruitment might enhance the sequestration of T cells in infected lymphoid organs and the spread of infection between cells, contributing to the immunopathology of AIDS.

“…The opposite is conceivable as well, that long-lived memory cells specific, e.g., for tetanus toxoid (TT) or purified protein derivative of Mycobacterium tuberculosis (PPD) expand clonally under the influence of bystander cytokine during such infections (11)(12)(13). Furthermore, to understand the various states of T cell immunodeficiency, it is critical to know whether they are the result of reduced numbers of Ag-specific memory cells (frequencies), impaired function of these cells (reduced cytokine output per cell), a change in memory cell function (Th1/Th2 switch), or possibly a combination of these (14). Cytokine ELIS-POT analysis (15) might provide a unique tool with which to address these questions.…”

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confidence: 99%

Direct Visualization of Cytokine-Producing Recall Antigen-Specific CD4 Memory T Cells in Healthy Individuals and HIV Patients

Helms

Boehm

Asaad

et al. 2000

121

We have used computer-assisted cytokine ELISA spot analysis to measure the frequencies, the type of cytokine, and the amount of cytokine produced by individual recall Ag-specific CD4 memory cells in freshly isolated blood. We studied the memory cells specific for tetanus toxoid and purified protein derivative in 18 healthy individuals and in 22 HIV-infected patients on highly active antiretroviral therapy (HAART). In healthy individuals, the frequency, cytokine signature, and cytokine production per cell of these memory cells were stable over time. Although it is presently unclear whether the maintenance of the memory T cell pool depends upon Ag persistence, cross-reactive Ag stimulation, or cytokine-driven bystander stimulations and expansions, our data strongly argue for a stable memory cell pool in healthy individuals. In HIV patients, however, the frequency of these memory cells was a function of the viral load. The decreased numbers of functional memory cells in patients with high viral loads might provide one mechanism behind the immunodeficient state. Although the cytokine output per cell was unaffected in most patients (20 of 24), in some patients (4 of 24) it was >100-fold reduced, which might provide an additional mechanism to account for the reduced immunocompetence of these patients. The ability to visualize directly and quantify the cytokine produced by the low frequency memory cells in freshly isolated blood that have been physiologically stimulated by Ag should aid comprehensive studies of the Ag-specific memory cell pool in vivo, in health and disease.