Victor Pena-Cruz

CD1a-autoreactive T cells are a normal component of the human αβ T cell repertoire

CD1 activates T cells, but the function and size of the possible human T cell repertoires that recognize each of the CD1 antigen-presenting molecules remain unknown. Using an experimental system that bypasses major histocompatibility complex (MHC) restriction and the requirement for defined antigens, we show that polyclonal T cells responded at higher rates to cells expressing CD1a than to those expressing CD1b, CD1c or CD1d. Unlike the repertoire of invariant natural killer T (NKT) cells, the CD1a-autoreactive repertoire contained diverse T cell antigen receptors (TCRs). Functionally, many CD1a-autoreactive T cells homed to skin, where they produced interleukin 22 (IL-22) in response to CD1a on Langerhans cells. The strong and frequent responses among genetically diverse donors define CD1a-autoreactive cells as a normal part of the human T cell repertoire and CD1a as a target of the TH22 subset of helper T cells.

Interaction of human PD-L1 and B7-1.

Numerous studies have pointed to the role of programmed death-1 ligand 1 (PD-L1) in regulating tolerance, chronic infection, and tumor immunity. Recently, we have identified murine B7-1 as a new binding partner for murine PD-L1. Human and mouse B7-1 share only 46% identity, leading us to question whether human B7-1 and PD-L1 can participate in a similar interaction. Here we show that human B7-1 can interact with human PD-L1 with affinity greater than that of B7-1 with CD28, but less than that of B7-1 with CTLA-4 or of PD-L1 with PD-1. We characterize a series of anti-human PD-L1 monoclonal antibodies and identify antibodies that can block interactions of PD-L1 with B7-1, PD-1, or both. Since PD-L1 and CD28 on T cells may compete for B7-1 as a binding partner and CD8 T cells may express high or low levels of CD28, we examined when PD-L1 and CD28 are co-expressed on CD8 T cells. We compared the time-course and extent of PD-L1 induction on CD8 CD28high versus CD28low T cells following stimulation with anti-CD3. We show that PD-L1 is induced to a higher level on CD28high T cells than on CD28low T cells upon activation. These results suggest that PD-L1 may play an important and undervalued role on human T cells.

BCL9 Promotes Tumor Progression by Conferring Enhanced Proliferative, Metastatic, and Angiogenic Properties to Cancer Cells

Several components of the Wnt signaling cascade have been shown to function either as tumor suppressor proteins or as oncogenes in multiple human cancers, underscoring the relevance of this pathway in oncogenesis and the need for further investigation of Wnt signaling components as potential targets for cancer therapy. Here, using expression profiling analysis as well as in vitro and in vivo functional studies, we show that the Wnt pathway component BCL9 is a novel oncogene that is aberrantly expressed in human multiple myeloma as well as colon carcinoma. We show that BCL9 enhances beta-catenin-mediated transcriptional activity regardless of the mutational status of the Wnt signaling components and increases cell proliferation, migration, invasion, and the metastatic potential of tumor cells by promoting loss of epithelial and gain of mesenchymal-like phenotype. Most importantly, BCL9 knockdown significantly increased the survival of xenograft mouse models of cancer by reducing tumor load, metastasis, and host angiogenesis through down-regulation of c-Myc, cyclin D1, CD44, and vascular endothelial growth factor expression by tumor cells. Together, these findings suggest that deregulation of BCL9 is an important contributing factor to tumor progression. The pleiotropic roles of BCL9 reported in this study underscore its value as a drug target for therapeutic intervention in several malignancies associated with aberrant Wnt signaling.

CD1a-autoreactive T cells recognize natural skin oils that function as headless antigens

T cells autoreactive to the antigen-presenting molecule CD1a are common in human blood and skin, but the search for natural autoantigens has been confounded by background T cell responses to CD1 proteins and self lipids. After capturing CD1a-lipid complexes, we gently eluted ligands while preserving non–ligand-bound CD1a for testing lipids from tissues. CD1a released hundreds of ligands of two types. Inhibitory ligands were ubiquitous membrane lipids with polar head groups, whereas stimulatory compounds were apolar oils. We identified squalene and wax esters, which naturally accumulate in epidermis and sebum, as autoantigens presented by CD1a. The activation of T cells by skin oils suggested that headless mini-antigens nest within CD1a and displace non-antigenic resident lipids with large head groups. Oily autoantigens naturally coat the surface of the skin; thus, this points to a previously unknown mechanism of barrier immunity.

A comparative study of virus isolation, polymerase chain reaction, and antigen detection in children of mothers infected with human immunodeficiency virus

We report on an investigation designed to compare the polymerase chain reaction (PCR) with culture and p24 measurement for the diagnosis of human immunodeficiency virus (HIV) infection in infants and children. Forty-five children born of mothers with antibodies to HIV type 1 were studied; P24 antigen was measured in plasma, and HIV-1 proviral DNA was sought in peripheral blood mononuclear cells after amplification by PCR. In 26 cases, blood specimens were cultured for HIV; in all but two instances cultures were established at the same time that the PCR test was performed. Primer pairs in three regions of the proviral genome were used for the PCR test. There was good agreement between the results obtained from PCR tests and from cultures; of 24 children in whom both tests were done at the same time, 10 had positive results on both the culture and the PCR test, 1 had positive results on the PCR test but negative culture results, and 13 had negative results on both tests (concordance 96%). Measurement of p24 antigen in plasma was, in contrast, an insensitive marker of infection: 6 of 12 infants with positive cultures had positive p24 test results, and 8 of 18 infants had positive PCR test results. Sixteen children with subsequent seronegativity for HIV-1 had negative PCR results. This study provides further evidence that the PCR test is a valid alternative to viral culture for the diagnosis of pediatric HIV infection.

Host and Viral Factors Affecting the Decreased Immunogenicity of Sabin Type 3 Vaccine after Administration of Trivalent Oral Polio Vaccine to Rural Mayan Children

Abstract Factors affecting immunogenicity of the first 2 doses of oral poliovirus vaccine (OPV) among unimmunized Mayan infants were prospectively evaluated. The relative impact of multiple variables, including mass or routine vaccination, concurrent enteric bacterial (salmonella, shigella, and campylobacter) and viral (adenovirus 40/41, astrovirus, nonpolio enteroviruses, and rotavirus) infections, interference among Sabin vaccine viruses, and preexisting poliovirus antibodies were studied. Sera were available from 181 infants after 2 OPV doses. Seroresponses were 86% to Sabin type 1, 97% to Sabin type 2, and 61% to Sabin type 3 vaccines. Mass versus routine vaccination and preexisting poliovirus antibodies did not affect immunogenicity. By multiple logistic regression analysis, fecal shedding of homologous Sabin strains was associated with increased seroresponses to all Sabin types, especially to Sabin type 3. Decreased OPV immunogenicity was primarily attributable to interference of Sabin type 3 by Sabin type 2. OPV formulations with higher doses of Sabin type 3 could improve immunogenicity among infants in developing countries.

Borrelia burgdorferi infection regulates CD1 expression in human cells and tissues via IL1-β.

The appearance of group 1 CD1 proteins (CD1a, CD1b and CD1c) on maturing myeloid DC is a key event that converts myeloid DC to effective lipid APC. Here, we show that Borrelia burgdorferi, the causative agent of Lyme disease, triggers appearance of group 1 CD1 proteins at high density on the surface of human myeloid DC during infection. Within human skin, CD1b and CD1c expression was low or absent prior to infection, but increased significantly after experimental infections and in erythema migrans lesions from Lyme disease patients. The induction of CD1 was initiated by borrelial lipids acting through TLR‐2 within minutes, but required 3 days for maximum effect. The delay in CD1 protein appearance involved a multi‐step process whereby TLR‐2 stimulated cells release soluble factors, which are sufficient to transfer the CD1‐inducing effect in trans to other cells. Analysis of these soluble factors identified IL‐1β as a previously unknown pathway leading to group 1 CD1 protein function. This study establishes that upregulation of group 1 CD1 proteins is an early event in B. burgdorferi infection and suggests a stepwise mechanism whereby bacterial cell walls, TLR activation and cytokine release cause DC precursors to express group 1 CD1 proteins.

Extraction of human Langerhans cells: a method for isolation of epidermis-resident dendritic cells

Langerhans cells (LCs) are immature dendritic cells in the epidermis that play a central role in T-lymphocyte mediated skin immunity. Upon activation with antigenic stimuli, they differentiate drastically into mature dendritic cells while migrating from the epidermis to regional lymph nodes. Thus, in order to study biological details of immature LCs, it is crucial to isolate epidermis-resident, immature LCs without dermal dendritic cell contamination. Methods for extracting LCs from human skin as well as in vitro derivation of LC-like cells from hematopoietic progenitor cells have been described previously, but the cell preparations can potentially contain a significant number of dendritic cells that are not identical to epidermal LCs. Here, we describe a technique by which purely epidermis-resident LCs are extracted from human skin. Following digestion of human skin with dispase, the epidermis was separated mechanically without any attached dermal component. The trypsinized epidermal cells were then fractionated by centrifugation with a discontinuous density gradient composed of bovine albumin and sodium metrizoate. The LC-enriched preparation thus obtained contained 80% to >90% CD1a+, E-cadherin+ cells that expressed Birbeck granules and the Lag protein. Consistent with their being at an immature stage, the freshly isolated LCs lacked the expression of CD83, a marker for mature dendritic cells. The purified LCs were able to activate allogeneic T cells, indicating that the cells retained T-cell stimulation ability even after extraction. Thus, the present work offers an opportunity for precise in vitro studies of epidermal LCs.

β-catenin is dynamically stored and cleared in multiple myeloma by the proteasome–aggresome–autophagosome–lysosome pathway

β-catenin is dynamically stored and cleared in multiple myeloma by the proteasome–aggresome–autophagosome–lysosome pathway

Early infection HIV-1 envelope V1-V2 genotypes do not enhance binding or replication in cells expressing high levels of α4β7 integrin.

Abstract:It has been postulated that HIV-1 envelope properties, such as shorter and less-glycosylated V1-V2 loops commonly observed among non–subtype B early-transmitted viruses, promote utilization of the gut homing integrin &agr;4&bgr;7. This property potentially confers an advantage to some HIV-1 variants early after acquisition. We found that replication-competent recombinant viruses incorporating HIV-1 subtype A compact and less-glycosylated early versus chronic phase V1-V2 loops demonstrated no significant difference in binding to &agr;4&bgr;7 high CD8+ T cells or replication in &agr;4&bgr;7 high CD4+ T cells. Integrin &agr;4&bgr;7 usage does not select for shorter less-glycosylated envelopes during transmission.