It has been known since 1986 that CD8 T lymphocytes from certain HIV-1-infected individuals who are immunologically stable secrete a soluble factor, termed CAF, that suppresses HIV-1 replication. However, the identity of CAF remained elusive despite an extensive search. By means of a protein-chip technology, we identified a cluster of proteins that were secreted when CD8 T cells from long-term nonprogressors with HIV-1 infection were stimulated. These proteins were identified as alpha-defensin 1, 2, and 3 on the basis of specific antibody recognition and amino acid sequencing. CAF activity was eliminated or neutralized by an antibody specific for human alpha-defensins. Synthetic and purified preparations of alpha-defensins also inhibited the replication of HIV-1 isolates in vitro. Taken together, our results indicate that alpha-defensin 1, 2, and 3 collectively account for much of the anti-HIV-1 activity of CAF that is not attributable to beta-chemokines.

BackgroundDuring acute and early HIV-1 infection (AEI), up to 60% of CD4+ T cells in the lamina propria of the lower gastrointestinal (GI) tract are lost as early as 2–4 wk after infection. Reconstitution in the peripheral blood during therapy with highly active antiretroviral therapy (HAART) is well established. However, the extent of immune reconstitution in the GI tract is unknown.Methods and FindingsFifty-four AEI patients and 18 uninfected control participants underwent colonic biopsy. Forty of the 54 AEI patients were followed after initiation of antiretroviral therapy (18 were studied longitudinally with sequential biopsies over a 3-y period after beginning HAART, and 22 were studied cross sectionally after 1–7 y of uninterrupted therapy). Lymphocyte subsets, markers of immune activation and memory in the peripheral blood and GI tract were determined by flow cytometry and immunohistochemistry. In situ hybridization was performed in order to identify persistent HIV-1 RNA expression. Of the patients studied, 70% maintained, on average, a 50%–60% depletion of lamina propria lymphocytes despite 1–7 y of HAART. Lymphocytes expressing CCR5 and both CCR5 and CXCR4 were persistently and preferentially depleted. Levels of immune activation in the memory cell population, CD45RO+ HLA-DR+, returned to levels seen in the uninfected control participants in the peripheral blood, but were elevated in the GI tract of patients with persistent CD4+ T cell depletion despite therapy. Rare HIV-1 RNA–expressing cells were detected by in situ hybridization.ConclusionsApparently suppressive treatment with HAART during acute and early infection does not lead to complete immune reconstitution in the GI mucosa in the majority of patients studied, despite immune reconstitution in the peripheral blood. Though the mechanism remains obscure, the data suggest that there is either viral or immune-mediated accelerated T cell destruction or, possibly, alterations in T cell homing to the GI tract. Although clinically silent over the short term, the long-term consequences of the persistence of this lesion may emerge as the HIV-1–infected population survives longer owing to the benefits of HAART.

Hematopoietic cells differentiate in steps marked by the acquisition or loss of specific phenotypic characteristics. Human bone marrow cells that were responsive to the early-acting cytokines Kit ligand and interleukin-3 were forced to a metabolic death. The subfraction remaining represented 1 in 10(5) bone marrow mononuclear cells, were determined to be quiescent by cell cycle analysis, and had a stem cell immunophenotype. The cells were highly enriched for long-term culture-initiating cells, were capable of secondary colony formation, and produced both myeloid and lymphoid progeny. Thus, this technically simple strategy led to the efficient purification of cells with characteristics of hematopoietic stem cells.

The familial Alzheimer's disease gene product amyloid ␤ precursor protein (APP) is sequentially processed by ␤-and ␥-secretases to generate the A␤ peptide. The biochemical pathway leading to A␤ formation has been extensively studied since extracellular aggregates of A␤ peptides are considered the culprit of Alzheimer's disease. Aside from its pathological relevance, the biological role of APP processing is unknown. Cleavage of APP by ␥-secretase releases, together with A␤, a COOH-terminal APP intracellular domain, termed AID. This peptide has recently been identified in brain tissue of normal control and patients with sporadic Alzheimer's disease. We have previously shown that AID acts as a positive regulator of apoptosis. Nevertheless, the molecular mechanism by which AID regulates this process remains unknown. Hoping to gain clues about the function of APP, we used the yeast two-hybrid system to identify interaction between the AID region of APP and JNK-interacting protein-1 (JIP1). This molecular interaction is confirmed in vitro, in vivo by fluorescence resonance energy transfer (FRET), and in mouse brain lysates. These data provide a link between APP and its processing by ␥-secretase, and stress kinase signaling pathways. These pathways are known regulators of apoptosis and may be involved in the pathogenesis of Alzheimer's disease. The amyloid ␤ (A␤)1 peptide is the principal component of amyloid plaques in the brain of Alzheimer's disease (AD) patients (1-3). A␤ is derived from APP by two sequential proteolytic events, one in the extracellular domain (␤-secretase cleavage) (4) and one in the transmembrane domain (␥-secretase cleavage) (5). APP processing has become firmly associated with the pathogenesis of AD with the identification of missense mutations in three genes associated with familial forms of AD (FAD). The FAD mutations identified to date are found in APP itself, and in two highly homologous genes now known as presenilin 1 and presenilin 2 (PS1, PS2) (6 -9). Presenilins are a key component of a multimolecular complex with ␥-secretase activity that contains at least one other recently identified protein named nicastrin (10 -16). A common feature of all FAD mutations is that they increase the generation of A␤ peptides (especially the A␤42 form, considered to be more pathogenic than the A␤40 peptide) by accelerating the rate of APP processing by either ␤-or ␥-secretase (5, 18 -20). In addition to the A␤ peptide which is mostly released from the cell, another peptide, AID, is released into the cytoplasm as a result of the ␥-secretase cleavage. Although the role of the A␤ peptide in the pathogenesis of AD has been extensively studied, only recently have there been reports as to the role of AID. AID-like peptides have recently been identified in human brains from normal controls and cases of sporadic AD (21). AID has also been implicated in the pathology of AD by data indicating that it can independently trigger apoptosis or enhance other apoptotic stimuli (21). This may represent the mechanism by wh...

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During acute and early human immunodeficiency virus type 1 (HIV-1) infection (AEI) more than 50% of CD4؉ T cells are preferentially depleted from the gastrointestinal (GI) lamina propria. To better understand the underlying mechanisms, we studied virological and immunological events within the peripheral blood (PB) and GI tract during AEI. A total of 32 AEI subjects and 18 uninfected controls underwent colonic biopsy. HIV-1 viral DNA and RNA levels were quantified in CD4 ؉ T cells derived from the GI tract and PB by using real-time PCR. The phenotype of infected cells was characterized by using combinations of immunohistochemistry and in situ hybridization. Markers of immunological memory, activation, and proliferation were examined by flow cytometry and immunohistochemistry, and the hostderived cytotoxic cellular response was examined by using immunohistochemistry. GI CD4 ؉ T cells harbored, on average, 13-fold higher HIV-1 viral DNA levels and 10-fold higher HIV-1 RNA levels than PB CD4 ؉ T cells during AEI. HIV-1 RNA was detected in both "activated" and "nonactivated" mucosal CD4

The ␤-amyloid precursor protein (APP) and the Notch receptor undergo intramembranous proteolysis by the Presenilin-dependent ␥-secretase.

The human genome encodes several hundred microRNA (miRNA) genes that produce small (21-23n) single strand regulatory RNA molecules. Although abnormal expression of miRNAs has been linked to cancer progression, the mechanisms of this dysregulation are poorly understood. Malignant mesothelioma (MM) of pleura is an aggressive and highly lethal cancer resistant to conventional therapies. We and others previously linked loss of the 9p21.3 chromosome in MM with short time to tumor recurrence. In this study, we report that MM cell lines derived from patients with more aggressive disease fail to express miR-31, a microRNA recently linked with suppression of breast cancer metastases. We further demonstrate that this loss is due to homozygous deletion of the miR-31-encoding gene that resides in 9p21.3. Functional assessment of miR-31 activity revealed its ability to inhibit proliferation, migration, invasion, and clonogenicity of MM cells. Re-introduction of miR-31 suppressed the cell cycle and inhibited expression of multiple factors involved in cooperative maintenance of DNA replication and cell cycle progression, including pro-survival phosphatase PPP6C, which was previously associated with chemotherapy and radiation therapy resistance, and maintenance of chromosomal stability. PPP6C, whose mRNA is distinguished with three miR-31-binding sites in its 3-untranslated region, was consistently down-regulated by miR-31 introduction and upregulated in clinical MM specimens as compared with matched normal tissues. Taken together, our data suggest that tumorsuppressive propensity of miR-31 can be used for development of new therapies against mesothelioma and other cancers that show loss of the 9p21.3 chromosome.