Slow turnover of HIV-1 receptors on quiescent CD4+ T cells causes prolonged surface retention of gp120 immune complexes in vivo

Temsavir blocks the immunomodulatory activities of HIV-1 soluble gp120

While HIV-1-mediated CD4 downregulation protects infected cells from antibody-dependent cellular cytotoxicity (ADCC), shed gp120 binds to CD4 on uninfected bystander CD4+ T cells, sensitizing them to ADCC mediated by HIV+ plasma. Soluble gp120-CD4 interaction on multiple immune cells also triggers a cytokine burst. The small molecule temsavir acts as an HIV-1 attachment inhibitor by preventing envelope glycoprotein (Env)-CD4 interaction and alters the overall antigenicity of Env by affecting its processing and glycosylation. Here we show that temsavir also blocks the immunomodulatory activities of shed gp120. Temsavir prevents shed gp120 from interacting with uninfected bystander CD4+ cells, protecting them from ADCC responses and preventing a cytokine burst. Mechanistically, this depends on temsavir's capacity to prevent soluble gp120-CD4 interaction, to reduce gp120 shedding, and to alter gp120 antigenicity. This suggests that the clinical benefits provided by temsavir could extend beyond blocking viral entry.

Pathogenesis, clinical course, and recent issues in HIV-1-infected Japanese hemophiliacs: a three-decade follow-up

Nearly 30% of Japanese hemophiliacs were infected with HIV-1 in the early 1980s. They have unique characteristics compared to HIV-1-infected individuals through other routes, including date of infection of 1986 or earlier, mean age of nearly 50 years, and common co-infection with hepatitis C, but rarely with other sexually transmitted diseases. Antiretroviral therapy (ART) was introduced in Japan in 1997. The clinical courses before and after 1997 were quite different. Careful analysis of the pre-1997 clinical data allowed expansion of our knowledge about the natural course and pathogenesis of the disease. Switching to the second receptor agents proved critical in subsequent disease progression. HIV-1 continued to escape immune pressure, pushing disease progression faster. In contrast, ART was effective enough to overcome the natural course. Prognosis improved dramatically and cause of death changed from AIDS-related opportunistic infections and malignancies before 1997, to hepatitis C virus-related cirrhosis and hepatocellular carcinoma (HCC) around 2010, and again to non-AIDS defining malignancies recently. In most cases, hepatitis C was cured with direct acting antiviral therapy. However, HCV progressed to cirrhosis in some cases and risk of HCC is still high among these patients. Together with improvement in anticoagulants and aging of the patients, risk of myocardial infarction has increased recently. In addition, the numbers of patients with life-style related co-morbidities, such as diabetes mellitus, hypertension, and chronic kidney disease have been also increasing. Finally, stigma is still an important barrier to a better life in HIV-1-positive individuals.

Small CD4 Mimetics Prevent HIV-1 Uninfected Bystander CD4 + T Cell Killing Mediated by Antibody-dependent Cell-mediated Cytotoxicity

Human immunodeficiency virus type 1 (HIV-1) infection causes a progressive depletion of CD4 + T cells. Despite its importance for HIV-1 pathogenesis, the precise mechanisms underlying CD4 + T-cell depletion remain incompletely understood. Here we make the surprising observation that antibody-dependent cell-mediated cytotoxicity (ADCC) mediates the death of uninfected bystander CD4 + T cells in cultures of HIV-1-infected cells. While HIV-1-infected cells are protected from ADCC by the action of the viral Vpu and Nef proteins, uninfected bystander CD4 + T cells bind gp120 shed from productively infected cells and are efficiently recognized by ADCC-mediating antibodies. Thus, gp120 shedding represents a viral mechanism to divert ADCC responses towards uninfected bystander CD4 + T cells. Importantly, CD4-mimetic molecules redirect ADCC responses from uninfected bystander cells to HIV-1-infected cells; therefore, CD4-mimetic compounds might have therapeutic utility in new strategies aimed at specifically eliminating HIV-1-infected cells.

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Gp120 shed from productively-infected cells binds to bystander CD4 + T cells.

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Gp120-coated bystander cells are highly sensitivity to ADCC responses mediated by CD4-induced antibodies.

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Small-molecule CD4-mimetics redirect CD4-induced antibodies to HIV-1-infected cells.

The hallmark of human immunodeficiency virus type 1 (HIV-1) infection is the progressive depletion of CD4 + T cells. Using cultures of HIV-1-infected cells, we observed that a part of the machinery that the virus uses to infect cells (gp120) binds to uninfected cells. Antibodies elicited during the course of the infection against the gp120 can recognize uninfected cells and redirect an immune response to them that results in their elimination. Importantly, this phenomenon can be blocked with a small CD4-mimetic compound that abrogates the binding of gp120 to uninfected cells and redirects the immune system to infected cells.

The orientation of HIV-1 gp120 binding to the CD4 receptor differentially modulates CD4+ T cell activation

Progressive quantitative and qualitative decline of CD4(+) T cell responses is one hallmark of HIV-1 infection and likely depends on several factors, including a possible contribution by the HIV-1 envelope glycoprotein gp120, which binds with high affinity to the CD4 receptor. Besides virion-associated and cell-expressed gp120, considerable amounts of soluble gp120 are found in plasma or lymphoid tissue, predominantly in the form of gp120-anti-gp120 immune complexes (ICs). Because the functional consequences of gp120 binding to CD4(+) T cells are controversially discussed, we investigated how gp120 affects TCR-mediated activation of human CD4(+) T cells by agonistic anti-CD3 mAb or by HLA class II-presented peptide Ags. We show that the spatial orientation of gp120-CD4 receptor binding relative to the site of TCR engagement differentially affects TCR signaling efficiency and hence CD4(+) T cell activation. Whereas spatially and temporally linked CD4 and TCR triggering at a defined site promotes CD4(+) T cell activation by exceeding local thresholds for signaling propagation, CD4 receptor engagement by gp120-containing ICs all around the CD4(+) T cell undermine its capacity in supporting proximal TCR signaling. In vitro, gp120 ICs are efficiently captured by CD4(+) T cells and thereby render them hyporesponsive to TCR stimulation. Consistent with these in vitro results we show that CD4(+) T cells isolated from HIV(+) individuals are covered with ICs, which at least partially contain gp120, and suggest that IC binding to CD4 receptors might contribute to the progressive decline of CD4(+) T cell function during HIV-1 infection.