The interaction of CD2 with its LFA-3 ligand expressed by autologous erythrocytes results in enhancement of B cell responses

The addition of autologous erythrocytes to unfractionated human mononuclear cell cultures results in enhancement of B cell responses to antigens and mitogens. This costimulating effect of red cells is abrogated by their preincubation with anti-LFA-3 monoclonal antibody. Preincubation of mononuclear cells with anti-CD2 monoclonal antibodies (anti-Leu 5b, OKT11, used singly) has a down-regulating effect on B cell activation and no enhancement of B cell responses is seen when red cells are added to anti-CD2-treated cultures. These results demonstrate a functional effect on B cells of the interaction between the CD2 molecule on T lymphocytes and its natural ligand, LFA-3. The precise mechanism by which this costimulating effect on B lymphocytes takes place is unclear. The study of T cell populations and T cell activation markers shows that the addition of erythrocytes causes a small but reproducible increase in the number of cells expressing the IL-2 receptor and the addition of IL-2 enhances the response of mononuclear cells to antigenic stimulation in the presence of erythrocytes. However, the supernatants of mononuclear cell cultures stimulated with pokeweed mitogen in the presence of autologous erythrocytes show decreased levels of IL-2, compared to supernatants of cells stimulated with pokeweed mitogen alone. The same supernatants show increased levels of interferon-gamma, but the addition of this lymphokine to cultures stimulated with pokeweed mitogen has no potentiating effect. It is possible that the effect of erythrocytes is mediated by other growth and/or differentiation factors, and additional studies will be required to clarify this point.     

Incomplete Normalization of Regulatory T-Cell Frequency in the Gut Mucosa of Colombian HIV-Infected Patients Receiving Long-Term Antiretroviral Treatment

Introduction

To evaluate the effect of late initiation of HAART and poor immune reconstitution on the frequency of regulatory T-cells (Treg) in the peripheral blood and gut of HIV-infected patients, we studied Colombian HIV-infected patients who had been on suppressive HAART for at least one year. They had undetectable viremia but were either immunological responders (HIR); (CD4 counts >500 cells/µl) or non-immunological responders (NIR); (CD4 T-cell count <300 cells/µl). Untreated HIV-infected patients and uninfected controls from the same region were also evaluated.

Methods

Frequency and phenotype of regulatory T-cells (Treg) were analyzed in gut biopsies and blood samples. The functional effect of Treg depletion on CMV and HIV responses was determined. Markers of immune activation and circulating LPS levels were quantified.

Results

Untreated patients exhibited high Treg frequency in PBMC and gut, and their Treg express high levels of CTLA-4 and PD-1. Although HAART significantly decreased mucosal Treg frequency, it did not normalize it in any of the treated groups (HIR and NIR patients). Treg normalization was observed in the blood of HIR patients following HAART, but did not occur in NIR patients. Treg from HIV-infected patients (treated or not) suppressed HIV and hCMV-specific T-cells from gut and blood. Plasma LPS levels and percentage of HLA-DR+CD38+ T-cells were significantly elevated in all infected groups compared to controls.

Conclusions

These findings suggest that control of viral replication is not sufficient to normalize gut Treg frequency in patients, independent of their response to HAART. Furthermore, persistence of functional Treg in the gut appears to be associated with the failure of HAART to repair mucosal damage.     

Treatment with apolipoprotein A-1 mimetic peptide reduces lupus-like manifestations in a murine lupus model of accelerated atherosclerosis

Introduction

The purpose of this study was to evaluate the effects of L-4F, an apolipoprotein A-1 mimetic peptide, alone or with pravastatin, in apoE^-/-Fas^-/-C57BL/6 mice that spontaneously develop immunoglobulin G (IgG) autoantibodies, glomerulonephritis, osteopenia, and atherosclerotic lesions on a normal chow diet.

Methods

Female mice, starting at eight to nine weeks of age, were treated for 27 weeks with 1) pravastatin, 2) L-4F, 3) L-4F plus pravastatin, or 4) vehicle control, followed by disease phenotype assessment.

Results

In preliminary studies, dysfunctional, proinflammatory high-density lipoproteins (piHDL) were decreased six hours after a single L-4F, but not scrambled L-4F, injection in eight- to nine-week old mice. After 35 weeks, L-4F-treated mice, in the absence/presence of pravastatin, had significantly smaller lymph nodes and glomerular tufts (P_{L, LP} < 0.05), lower serum levels of IgG antibodies to double stranded DNA (dsDNA) (P_L < 0.05) and oxidized phospholipids (oxPLs) (P_{L, LP} < 0.005), and elevated total and vertebral bone mineral density (P_{L, LP} < 0.01) compared to vehicle controls. Although all treatment groups presented larger aortic root lesions compared to vehicle controls, enlarged atheromas in combination treatment mice had significantly less infiltrated CD68⁺ macrophages (P_LP < 0.01), significantly increased mean α-actin stained area (P_LP < 0.05), and significantly lower levels of circulating markers for atherosclerosis progression, CCL19 (P_{L, LP} < 0.0005) and VCAM-1 (P_L < 0.0002).

Conclusions

L-4F treatment, alone or with pravastatin, significantly reduced IgG anti-dsDNA and IgG anti-oxPLs, proteinuria, glomerulonephritis, and osteopenia in a murine lupus model of accelerated atherosclerosis. Despite enlarged aortic lesions, increased smooth muscle content, decreased macrophage infiltration, and decreased pro-atherogenic chemokines in L-4F plus pravastatin treated mice suggest protective mechanisms not only on lupus-like disease, but also on potential plaque remodeling in a murine model of systemic lupus erythematosus (SLE) and accelerated atherosclerosis.     

Molecular architecture of the ribosome‐bound Hepatitis C Virus internal ribosomal entry site RNA

Internal ribosomal entry sites (IRESs) are structured cis‐acting RNAs that drive an alternative, cap‐independent translation initiation pathway. They are used by many viruses to hijack the translational machinery of the host cell. IRESs facilitate translation initiation by recruiting and actively manipulating the eukaryotic ribosome using only a subset of canonical initiation factor and IRES transacting factors. Here we present cryo‐EM reconstructions of the ribosome 80S‐ and 40S‐bound Hepatitis C Virus (HCV) IRES. The presence of four subpopulations for the 80S•HCV IRES complex reveals dynamic conformational modes of the complex. At a global resolution of 3.9 Å for the most stable complex, a derived atomic model reveals a complex fold of the IRES RNA and molecular details of its interaction with the ribosome. The comparison of obtained structures explains how a modular architecture facilitates mRNA loading and tRNA binding to the P‐site. This information provides the structural foundation for understanding the mechanism of HCV IRES RNA‐driven translation initiation.     

Soluble factors with inhibitory activity against type 1 Human Immunodeficiency Virus

Soluble factors with inhibitory activity against type 1 Human Immunodeficiency Virus The pathogenesis of HIV-1 infection is a complex process that depends on multiple factors, including viral and host immune and genetic characteristics. This leads to a variable pattern of disease progression among those HIV-1-exposed individuals who become infected, while there are a number of individuals who remain healthy and HIV-1 seronegative despite being serially exposed to HIV-1. These variable outcomes of HIV-1 exposure suggest that there are mechanisms of natural resistance to HIV-1 infection. Although several genetic and adaptive immune mechanisms of resistance have been reported in some exposed seronegative and long-term non-progressor individuals, the mechanisms involved in controlling the establishment and progression of HIV-1 infection are not fully understood. Several soluble factors, such as defensins, chemokines, interferons and ribonucleases, among others, produced by cells of the immune system and epithelial tissues, have a broad anti-viral activity that might play a role as protective mechanisms during HIV-1 exposure. A better understanding of the mechanisms and role of these soluble factors during the natural resistance to HIV-1 infection may have important implications for the design of novel therapeutic strategies to combat the morbidity and mortality associated with the HIV-1 pandemic.     

Hormone-regulated expression and distribution of versican in mouse uterine tissues

Background  

Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination.