The continuing HIV epidemic among men who have sex with men and transgender women in the ASEAN region: implications for HIV policy and service programming.

Men who have sex with men (MSM) in Western urban areas have seen substantive decreases in new diagnoses of HIV infection. This paper explores whether such declines are present among MSM and transgender women (TGW) in Southeast Asia and discusses implications for HIV policies and programming. A scoping review was conducted of scientific publications and selected documents regarding the spread of HIV infection among MSM and TGW in major urban centres of the Association of Southeast Asian Nations (ASEAN) region. Continued high HIV prevalence and incidence among MSM are found in integrated behavioural and biological surveillance (IBBS) and research studies. HIV prevalence among MSM under IBBS decreased only in Bangkok from 28.6% in 2014 to 10.3% in 2018, whereas it was increasing in Kuala Lumpur, Ho Chi Minh City, Vientiane, and Phnom Penh. HIV/AIDS case reports regarding new HIV infection diagnoses among MSM have started to decrease in Singapore since 2011 and have been plateauing in Metropolitan Manila since 2017. Where data were available, it was found that HIV prevalence among TGW was high and if IBBS was conducted, it was increasing. HIV prevalence among TGW under IBBS in Jakarta had risen to 34.0% (2015) and 14.0% (2019) in Phnom Penh. These findings suggest that most ASEAN member states have so far failed to effectively implement and scale-up scientifically proven biomedical HIV prevention measures and counter stigma and discrimination that impedes access to appropriate HIV prevention and treatment services for MSM and TGW.

Prevalence, determinants of positivity, and clinical utility of cryptococcal antigenemia in Cambodian HIV-infected patients.

OBJECTIVES: To determine the prevalence, determinants ofpositivity, and clinical utility of serum cryptococcal polysaccharide (CPS) antigen testing among HIV-infected patients in 2004 in Cambodia, an area highly endemic for cryptococcosis. METHODS: All HIV-infected patients with a CD4+ count <200 cells/mm3 attending 1 of 2 Phnom Penh hospitals for the first time were systematically screened for serum CPS. Patients with positive test results were further investigated to identify those with cryptococcal meningitis (CM), pulmonary cryptococcosis, or isolated positive cryptococcal antigenemia (IPCA). RESULTS: The median (interquartile range [IQR]) CD4+ count of 327 enrolled patients was 24 (IQR: 8 to 65) cells/mm3. The prevalence of cryptococcal infection was 59 (18.0%) of 327 cases, of which 41 were CM and 10 were IPCA. In the absence of serum CPS detection, 17 (28.8%) of 59 cryptococcal infections would have been missed on the day of consultation. In patients with no specific symptoms of meningoencephalitis, the prevalence of positive serum CPS detection was 32 (10.8%) of 295 cases. Countryside residence (adjusted odds ratio [AOR] = 3.6), headache (AOR = 3.2), body mass index <15.4 kg/m2 (AOR = 3.4), CD4+ count <50 cells/mm3 (AOR = 4.0), and male gender (marginally, AOR = 2.1) were all independently associated with a positive test results. CONCLUSION: Serum CPS screening among AIDS patients with a CD4+ count <100 cells/mm3 is useful in areas highly endemic for cryptococcosis, allowing early diagnosis and treatment of this opportunistic infection.

Detection of low-frequency human antigen-specific CD4(+) T cells using MHC class II multimer bead sorting and immunoscope analysis.

MHC class II tetramers are attractive tools to study antigen-specific CD4(+) T cell responses in various clinical situations in humans. HLA-DRA1*0101/DRB1*0401 MHC class II heterodimers were produced as empty molecules using the Drosophila melanogaster expression system. Peptide binding experiments revealed that these molecules could be loaded efficiently with appropriate MHC class II tumor epitopes. Interestingly, MHC class II tetramer staining was influenced by modifications in membrane lipid rafts, and could in itself induce activation changes of stained CD4(+) T cells at 37 degrees C. In order to increase the threshold of detection of poorly represented peripheral antigen-specific CD4(+) T cells, we combined cell sorting using MHC class II multimer beads together with TCR analysis using the immunoscope technology. This strategy greatly increased the sensitivity of detection of specific CD4(+) T cells to frequencies as low as 4 x 10(-6) among peripheral blood mononuclear cells. Such a combined approach may have promising applications in the immunomonitoring of patients under vaccination protocols to tightly follow induced antigen-specific CD4(+) T cells expressing previously identified TCR.

Foxp3 expressing CD4+CD25(high) regulatory T cells are overrepresented in human metastatic melanoma lymph nodes and inhibit the function of infiltrating T cells.

Dominant tolerance is mediated by regulatory T cells (T(reg)) that control harmful autoimmune T cells in the periphery. In this study, we investigate the implication of T(reg) in modulating infiltrating T lymphocytes in human metastatic melanoma. We found that CD4(+)CD25(high) T cells are overrepresented in metastatic lymph nodes (LNs) with a 2-fold increased frequency compared with both tumor-free LNs and autologous PBMCs. These cells express the Foxp3 transcription factor, display an activated phenotype, and display a polyclonal TCR Vbeta chain repertoire. They inhibit in vitro the proliferation and cytokine production of infiltrating CD4(+)CD25(-) and CD8(+) T cells (IL-2, IFN-gamma) through a cell-contact-dependent mechanism, thus behaving as T(reg). In some cases, the presence of T(reg) type 1/Th3-like lymphocytes could also be demonstrated. Thus, T(reg) are a major component of the immunosuppressive microenvironment of metastatic melanoma LNs. This could explain the poor clinical response of cancer patients under immunotherapeutic protocols, and provides a new basis for future immunotherapeutic strategies counteracting in vivo T(reg) to reinforce local antitumor immune responses.

Selective accumulation of mature DC-Lamp+ dendritic cells in tumor sites is associated with efficient T-cell-mediated antitumor response and control of metastatic dissemination in melanoma.

The clinical relevance of dendritic cells (DCs) at the tumor site remains a matter of debate concerning their role in the generation of effective antitumor immunity in human cancers. We performed a comprehensive immunohistochemical analysis using a panel of DC-specific antibodies on regressing tumor lesions and sentinel lymph nodes (SLNs) in melanoma patients. Here we show in a case report involving spontaneous regression of metastatic melanoma that the accumulation of DC-Lamp+ DCs, clustered with tumor cells and lymphocytes, is associated with local expansion of antigen-specific memory effector CTLs. These findings were extended in a series of 19 melanoma-positive SLNs and demonstrated a significant correlation between the density of DC-Lamp+ DC infiltrates in SLNs with the absence of metastasis in downstream lymph nodes. This study, albeit performed in a limited series of patients, points to a pivotal role of mature DCs in the local expansion of efficient antitumor T-cell-mediated immune responses at the initial sites of metastasis and may have important implications regarding the prognosis, staging, and immunotherapy of melanoma patients.

Phage-displayed libraries of peptide/major histocompatibility complexes.

Characterizing peptide epitopes targeted by major histocompatibility complex (MHC)-restricted T cells of unknown specificity would have broad implications. In this article we introduce and validate an original phage-displayed library of noncovalent complexes of peptide and MHC (P/MHC). We show that soluble MHC molecules associate with peptides presented by a phage, thereby resulting in the formation of multivalent P/MHC phages. Complex formation is stabilized by the interaction of the soluble partner (MHC) with two components, peptide and beta2-microglobulin, both of which are covalently linked to the phage. As proof of concept, we have used this strategy to express peptide libraries in the context of H-2K(b). Using monoclonal antibody 25D (specific for ovalbumin/H-2K(b)) as a template to screen the library, we were able to select a variant epitope functionally and structurally related to the wild-type peptide. Interaction studies between monoclonal antibody 25D and cells suggest that the variant peptide has been selected on the basis of a decreased dissociation rate between the peptide/H-2K(b) complex and its ligand. A weak agonist of the N15 TCR (vesicular stomatitis virus/H-2K(b)-specific) was also isolated from another P/MHC library. This strategy opens up new perspectives for antigen discovery and the manipulation of T cell responses.

Characterization of antigen-specific repertoire diversity following in vitro restimulation by a recombinant adenovirus expressing human cytomegalovirus pp65.

Human cytomegalovirus (HCMV) and adenovirus cause significant morbidity and mortality in immunocompromised hosts undergoing allogeneic stem cell transplantation. We have previously established a procedure for the generation of polyclonal CTL with specificity against adenovirus and HCMV using a recombinant adenovirus encoding the HCMV pp65 protein (RAdpp65). However, specific CTL expanded after in vitro culture steps were subjected to several in vitro restimulations and, depending on the protocol adopted, this could lead to a selection bias, compromising the clinical benefit. To determine which part of the memory repertoire is selected after in vitro restimulation, we have followed the specificity and clonal composition of pp65-peptide-specific CD8(+) T cells in HLA-A*201 individuals before and after repeated in vitro restimulation of cells with RAdpp65, combining HLA tetrameric complexes and immunoscope analysis. Tetramer staining showed that, after in vitro restimulation, up to 60% of CD8(+) T cells were virus-specific. Immunoscope analysis showed that the predominant TCRBV diversity of pp65-specific clones was conserved, demonstrating that the memory repertoire was preserved all along the procedure. Altogether, these results suggest that the use of RAdpp65 to induce CMV- and adenovirus-specific CTL maybe appropriate for immunotherapy.

Combination of MHC-peptide multimer-based T cell sorting with the Immunoscope permits sensitive ex vivo quantitation and follow-up of human CD8+ T cell immune responses.

Identification of MHC-restricted antigens and progress in the induction and control of adaptive cytotoxic immune responses have led to renewed interest in immunotherapy as a treatment for severe pathologies such as cancer and autoimmune diseases. Reliable procedures for detecting and monitoring T cell responses induced by the treatment throughout a clinical trial are needed in order to design rational protocols with increased efficiency. We have attempted to develop such a procedure by combining T cell sorting using HLA-peptide complexes multimerized on magnetic beads together with the quantitative Immunoscope approach. Once a recruited patient has been typed for HLA and target antigens, relevant HLA--peptide multimers can be selected and used for sorting specific peripheral T cells prior to any treatment and at the peak of the expected response to treatment. Clonotypic primers specific for the TCR rearrangements of the specific T cell clones can then be designed and used for measuring the frequency of their TCR transcripts by quantitative PCR on blood samples or T cell subsets throughout the trial. In reconstruction experiments as well as in samples from one rheumatoid arthritis patient, we were readily able to detect and follow several T cell clones with a frequency as low as 10(-5) among CD8+ T cells. The main advantages of this procedure over other currently available assays are that it does not require any assumptions on the functional status of the specific T cells and it permits the monitoring of individual T cell clones whose phenotypic shift can thus be evaluated.