Envelope glycoprotein (gp120) from HIV-1 enhances Mycobacterium avium growth in human bronchoalveolar macrophages; an effect mediated by enhanced prostaglandin synthesis

Impact of human immunodeficiency virus on pulmonary vascular disease

With the advent of anti-retroviral therapy, non-AIDS-related comorbidities have increased in people living with HIV. Among these comorbidities, pulmonary hypertension (PH) is one of the most common causes of morbidity and mortality. Although chronic HIV-1 infection is independently associated with the development of pulmonary arterial hypertension, PH in people living with HIV may also be the outcome of various co-morbidities commonly observed in these individuals including chronic obstructive pulmonary disease, left heart disease and co-infections. In addition, the association of these co-morbidities and other risk factors, such as illicit drug use, can exacerbate the development of pulmonary vascular disease. This review will focus on these complex interactions contributing to PH development and exacerbation in HIV patients. We also examine the interactions of HIV proteins, including Nef, Tat, and gp120 in the pulmonary vasculature and how these proteins alter the endothelial and smooth muscle function by transforming them into susceptible PH phenotype. The review also discusses the available infectious and non-infectious animal models to study HIV-associated PAH, highlighting the advantages and disadvantages of each model, along with their ability to mimic the clinical manifestations of HIV-PAH.

Immunomodulatory effects of the HIV-1 gp120 protein on antigen presenting cells: implications for AIDS pathogenesis

Antigen presenting cell (APC) function is central to the development of an effective anti-viral immune response. Among APC, monocytes, macrophages and dendritic cells (DC) form the principal non-T cell compartment involved in in vivo HIV infection, and these cells play important and well-established roles in multiple aspects of viral pathogenesis. HIV infection may result in APC defects, which could ultimately contribute to the loss of CD4+ T cell responses observed early in HIV infection, when the CD4+ T cell number is still within the normal range. Extensive in vitro studies have demonstrated that the envelope glycoproteins of HIV-1 exert profound influences on various cell populations of the immune system, including hematopoietic progenitors, T and B lymphocytes, monocytes/ macrophages and DC, as well as on neuronal cells. The demonstration of the presence of envelope proteins both free in the circulation and bound to the surface of CD4+ cells suggests that gp120 interactions with non-infected cells can influence cellular functions in vivo, thus contributing to the immunopathogenesis of AIDS. This paper provides an overview of the present knowledge on gp120 binding, signal transduction triggering and interference with macrophage and DC functions and it highlights the importance of this interaction in the pathogenesis of AIDS.

Toll-like receptor 2 and mitogen- and stress-activated kinase 1 are effectors of Mycobacterium avium-induced cyclooxygenase-2 expression in macrophages

Understanding how pathogenic mycobacteria subvert the protective immune response is crucial to the development of strategies aimed at controlling mycobacterial infections. Prostaglandin E(2) exerts an immunosuppressive function in the context of mycobacterial infection. Because cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostaglandin biosynthesis, there is a need to delineate the mechanisms through which pathogenic mycobacteria regulate COX-2 expression in macrophages. Our studies demonstrate that the NF-kappaB and CRE elements of the COX-2 promoter are critical to Mycobacterium avium-induced COX-2 gene expression. M. avium-triggered signaling originates at the Toll-like receptor 2 (TLR2). Ras associates with TLR2 and activates the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK), whereas tumor necrosis factor receptor-associated factor 6 (TRAF6)/transforming growth factor beta-activated kinase 1 (TAK1)-dependent signaling activates p38 MAPK. Both ERK and p38 MAPK activation converge to regulate the activation of mitogen- and stress-activated kinase 1 (MSK1). MSK1 mediates the phosphorylation of the transcription factor CREB accounting for its stimulatory effect on CRE-dependent gene expression. M. avium-triggered cytoplasmic NF-kappaB activation following IkappaB phosphorylation is necessary but not sufficient for COX-2 promoter-driven gene expression. MSK1 activation is also essential for M. avium-triggered NF-kappaB-dependent gene expression, presumably mediating nucleosomal modifications. These studies demonstrate that the nuclear kinase MSK1 is necessary in regulating the pathogen-driven expression of a gene by controlling two transcription factors. The attenuation of MSK1 may therefore have potential benefit in restricting survival of pathogenic mycobacteria in macrophages.

Peroxisome proliferator-activated receptor gamma agonists inhibit HIV-1 replication in macrophages by transcriptional and post-transcriptional effects

Previous studies have demonstrated that cyclopentenone prostaglandins (cyPG) inhibit human immunodeficiency virus type 1 (HIV-1) replication in various cell types. We investigated the role of PG in the replication of HIV-1 in primary macrophages. The cyPG, PGA(1) and PGA(2), inhibited HIV-1 replication in acutely infected human monocyte-derived macrophages (MDM). Because PGA(1) and PGA(2) have previously been shown to be peroxisome proliferator-activated receptor gamma (PPARgamma) agonists, we examined the effect of synthetic PPARgamma agonists on HIV replication. The PPARgamma agonist ciglitazone inhibited HIV-1 replication in a dose-dependent manner in acutely infected human MDM. In addition, cyPG and ciglitazone reduced HIV replication in latently infected and viral entry-independent U1 cells, suggesting an effect at the level of HIV gene expression. Ciglitazone also suppressed HIV-1 mRNA levels as measured by reverse transcriptase PCR, in parallel with the decrease in reverse transcriptase activity. Co-transfection of PPARgamma wild type vectors and treatment with PPARgamma agonists inhibited HIV-1 promoter activity in U937 cells. Activation of PPARgamma also decreased HIV-1 mRNA stability following actinomycin D treatment. In summary, our experimental findings implicate PPARgamma as an important factor in the suppression of HIV-1 gene expression in MDM by cyPG. Thus natural and synthetic PPARgamma agonists may play a role in controlling HIV-1 infection in macrophages.

Induction of disseminated Mycobacterium avium in simian AIDS is dependent upon simian immunodeficiency virus strain and defective granuloma formation

Mycobacterium avium complex (MAC) is the most common disseminated bacterial disease in patients infected by the human immunodeficiency virus. Although murine models of disseminated MAC exist, they are primarily based on underlying genetic susceptibilities and cannot adequately address the complex interactions that occur between host, mycobacteria, and immunosuppressive lentivirus. To address this problem we have developed an experimental system to co-inoculate rhesus macaques with the simian immunodeficiency virus (SIV) and a clinical M. avium isolate that results in a disease virtually identical to that observed in human cases. Using this experimental system we have found that the development of disseminated MAC is dependent on viral strain. Animals co-infected with SIVmac251 and M. avium developed progressive disease, whereas control animals and animals inoculated with closely related viruses (SIVmac239 and SIVmac239MER) developed self-limiting infections. The ability of animals infected with SIVmac239 or SIVmac239MER to eliminate mycobacterial disease was independent of viral load and CD4 T-cell number but was correlated with the size and composition of microgranulomas. This work establishes a novel primate model of disseminated MAC in the context of immunosuppressive lentiviral infection and advances our understanding of why human immunodeficiency virus-infected patients are remarkably sensitive to the development of mycobacterial disease.

HIV type 1 envelope glycoprotein gp120 induces development of a T helper type 2 response to Cryptococcus neoformans

OBJECTIVE

To analyse the contribution of HIV type 1 envelope glycoprotein gp120 to regulation of a T-cell response to Cryptococcus neoformans.

DESIGN

Monocytes treated with recombinant gp120 and exposed to C. neoformans were used as antigen presenting cells (APC) in coculture with autologous T lymphocytes.

METHODS

Costimulatory and major histocompatibility complex class II molecules were evaluated on APC by flow cytometry analysis. T-cell proliferation was determined as 3H thymidine incorporation. Cytokine production was analysed by enzyme-linked immunosorbent assay.

RESULTS

gp120 had multiple effects on APC and the T-cell response including: (i) up-regulation of major histocompatibility complex class II antigens on the APC surface resulting from both redistribution of molecules from the intracellular pool and synthesis of new molecules; (ii) up-regulation of B7-2 molecules on the APC surface; (iii) altered T-cell proliferation; and (iv) promotion of interleukin-4 and inhibition of interferon-gamma synthesis and release.

CONCLUSIONS

These data indicate that gp120 alters the normal T-cell response to C. neoformans, promoting a T-helper type 2 response. The altered T-cell response produced by gp120 may play an important role in the pathogenesis of cryptococcosis in the patient with AIDS.

Phenotypic changes of monocytes induced by HIV-1 gp120 molecule and its fragments

Several phenotypic and functional changes of monocytes (M phi) have been described in HIV-1+ subjects and AIDS patients. Some of these changes that are pertinent for immunopathogenesis of the disease may be induced by HIV-1 envelope glycoprotein 120 (gp120). In the present study the effect of recombinant full length gp120 (FLgp120) and its two fragments: rp120cd (aa 410-511) and rp120 (aa 446-511) on the expression of the surface molecules of M phi cultured in vitro was determined. The FLgp120 and rp120cd caused upregulation of CD14 and CD44. The rp120cd peptide significantly increased the expression of CD16 (Fc gamma receptor type III) and TNF receptor type II. In contrast, the rp120 downregulated HLA-DR, CD64 (Fc gamma RI), interferon gamma receptor and induced IL-10 production by M phi. This study indicates that gp120 molecule and its fragments may induce several phenotypic changes of M phi in particular the increased proportion of CD14+CD16+ cells that is observed in the blood of AIDS patients. These results provide further evidence for variable response of M phi to gp120 which may explain the variability of phenotypic changes and heterogeneity of M phi subsets seen in HIV-1 disease.

Soluble factor of transformed B lymphocytes in patients with HIV infection stimulates monocytes to produce PGE2

Prostaglandins of the E series (PGE) were measured in the culture supernatants of peripheral blood mono-nuclear cells (PBMC) obtained from patients with human immunodeficiency virus (HIV) infection. Cell culture supernatants from 6 patients with acquired immunodeficiency disease (AIDS) and 11 patients with AIDS-related complex contained significantly higher concentrations of PGE than those from a group of 6 healthy HIV-negative male homosexual control subjects. The PGE producer cells were among the population of plastic-adherent PBMC. Transformed B lymphocyte cell lines spontaneously derived from the blood of patients with AIDS secrete a factor that stimulates normal donor adherent PBMC to produce PGE. The HIV permissive H9 cell line stimulated a significantly lower level of PGE production, which was not associated with HIV infection.