Nesrina Imami

Loss of CD4+ T Cell Proliferative Ability but Not Loss of Human Immunodeficiency Virus Type 1 Specificity Equates with Progression to Disease

In this study, we compared human immunodeficiency virus (HIV) type 1-specific proliferative responses with HIV-1-induced intracellular cytokine production in a cohort of clinically nonprogressing patients and individuals with progressive HIV-1 infection. We found strong HIV-1-specific proliferative responses in the clinical nonprogressor cohort that correlated with significant numbers of circulating HIV-1-specific CD4(+) T cells. In contrast, HIV-1-specific proliferative responses were absent in most individuals with progressive HIV-1 infection, even though interferon-gamma-producing HIV-1-specific CD4(+) T cells were detectable by flow cytometry. The implication of these data is that the important dysfunction seen in most HIV-positive patients from very early in disease may be an inability of HIV-1-specific CD4(+) memory T cells to proliferate in response to HIV antigens rather than an absolute loss of circulating virus-specific CD4(+) T cells.

Both age and gender affect thymic output: more recent thymic migrants in females than males as they age

The thymus undergoes age‐associated involution, with studies showing thymic size decreasing from birth at a rate of approximately 3% per year until middle age, and at a rate of 1% per year thereafter. The aim of this study was to determine the effect of thymic atrophy on T‐lymphocyte production by the thymus, and to clarify the ongoing uncertainty regarding gender differences in thymic function. We quantified recent thymic emigrants (RTEs) in blood through the measurement of signal joint T‐cell receptor rearrangement excision circles (sjTRECs), and showed that the decline in the number of RTEs in the blood with increasing age is gender‐linked. Peripheral blood from females contained significantly higher levels of sjTRECs per CD3+ T cell than blood from males (P = 0·002), despite there being no significant gender difference in the absolute number of CD3+ T cells in the populations analysed (P > 0·10). Our findings suggest better thymic function in females compared with males, providing females with a higher number of recent thymic emigrants for longer periods of life. Such a finding provides a plausible explanation for the immunological gender differences observed in previous studies and possibly, for the general longer life expectancy in females compared with males.

Identification of Kaposi's Sarcoma-Associated Herpesvirus (KSHV)-Specific Cytotoxic T-Lymphocyte Epitopes and Evaluation of Reconstitution of KSHV-Specific Responses in Human Immunodeficiency Virus Type 1-Infected Patients Receiving Highly Active Antiretroviral Therapy

ABSTRACT Following the introduction of highly active antiretroviral therapy (HAART), the incidence of Kaposis sarcoma (KS) has significantly declined in human immunodeficiency virus type 1 (HIV-1)-positive (HIV-1+) individuals and clinical remission is often observed. We hypothesize that these effects are partly due to anti-KS-associated herpesvirus (KSHV) immune restoration. Here, 15-mer overlapping peptides from proteins K12 and K8.1 were used to identify novel KSHV-specific cytotoxic T-lymphocyte epitopes. Three immunogenic peptides, two lytic and one latent, were subsequently used to monitor the anti-KSHV CD8+ T-cell responses in a cohort of 19 HIV-1+ KSHV+/− KS+/− individuals during 52 weeks of HAART. KSHV and HIV-1 loads, KSHV antibody titers, and both CD4+ and CD8+ T-lymphocyte counts were enumerated. Prior to HAART, the total number of spot-forming cells (SFC) for all three peptides correlated with both CD4+ and CD8+ T-lymphocyte counts (P ≤ 0.05) in the KSHV-positive KS-positive cohort (n = 11). Following 52 weeks of HAART, significant decreases in HIV-1 and KSHV loads were associated with significant increases in CD4+ T-lymphocyte counts and number of SFC for the three KSHV-specific peptides. Although these increases were modest in comparison to the number of SFC observed with the HIV-1 gag peptide SLYNTVATL, they represented a fourfold increase from the baseline, continuing an upward trend to week 52.

A Balanced Type 1/Type 2 Response Is Associated with Long-Term Nonprogressive Human Immunodeficiency Virus Type 1 Infection

ABSTRACT Previous reports have emphasized the requirements for strong type 1 cell-mediated responses in the control of human immunodeficiency virus type 1 (HIV-1). HIV-1 Gag p24-specific CD4 helper T-lymphocyte (HTL) responses have been shown to inversely correlate with viral burden in HIV-1-infected individuals. In this study, peripheral blood mononuclear cells from 70 individuals with chronic progressive HIV-1 infection (clinical progressors), 10 clinical nonprogressors, and 3 immunologically discordant progressors were assessed for HTL proliferation and type 1/type 2 cytokine production. Clinical progressors lacked functional HIV-1-specific HTLs with proliferative and cytokine-producing capacity. Clinical nonprogressors were found to respond to a wide range of HIV-1 antigens from different clades, producing both type 1 and type 2 cytokines. Immunologically discordant progressors responded strongly to clade B Gag p24 with a type 1 cytokine profile but not to other antigens. Thus, in contrast to clinical nonprogressors, neither progressors nor immunologically discordant progressors secreted interleukin-4 (IL-4) in response to HIV-1 antigens. Both clinical nonprogressors and immunologically discordant progressors responded broadly to B clade Gag p24-overlapping peptides. However, IL-4 production in the nonprogressors was restricted to a limited number of p24 peptides. No HIV-1-specific T-cell responses were seen in 20 seronegative controls. Additionally, we observed a rapid type 1 to type 2 shift in the response of one immunologically discordant progressor upon onset of clinical symptoms. These results suggest that a balanced type 1/type 2 profile correlates with successful long-term control of HIV-1.

Assessment of type 1 and type 2 cytokines in HIV type 1-infected individuals : Impact of highly active antiretroviral therapy

Although the effect of highly active antiretroviral therapy (HAART) on HIV-1 replication has been established, the mechanisms involved in restoration of immune responses and reconstitution remain unknown. This study provides evidence of changes in expression of type 1 and type 2 cytokine-specific mRNA occurring during HIV-1 infection, before and after initiation of HAART. Unstimulated PBMCs from nine HIV-1-infected individuals obtained at different time intervals before and after the initiation of HAART were assessed for specific IFN-gamma, IL-2, IL-4, and IL-10 mRNA expression, using RT-PCR. Correlation with CD4+ T cell counts and viral load was also carried out. Before initiation of HAART, in all patients, little expression of specific IFN-gamma and IL-2 (type 1 cytokine) mRNA was noted. In contrast, expression of specific IL-4 and/or IL-10 (type 2) mRNA was readily detectable in the majority of patients. After initiation of HAART there was a continuous increase in IFN-gamma and IL-2 mRNA expression, although the latter occurred in lower amounts. This paralleled a dramatic reduction in viral load and increase in CD4+ T cell counts. Type 2 cytokine-specific mRNA expression fell to undetectable levels and in some cases reappeared later in the course of HAART. Predominant expression of type 2 cytokine mRNA, before initiation of HAART, concurs with previous findings of a dominant antiproliferative, type 2 cytokine profile during HIV-1 infection. Reversion of the cytokine profile, after HAART, to a strong type 1 profile suggests that in addition to suppressing virus replication directly the immune system may be given a chance to recover.

Effects of combination chemotherapy and highly active antiretroviral therapy on immune parameters in HIV-1 associated lymphoma.

Objective To measure the effects of combined chemotherapy and highly active antiretroviral therapy (HAART) on immune cell counts and plasma HIV-1 RNA loads in patients with AIDS-related lymphoma (ARL) to determine the implications for opportunistic infection prophylaxis and medium-term immune function. Design and methods Peripheral blood total lymphocyte count, CD4 T-cell count, CD8 T-cell count, CD19 B-cell count, CD16/CD56 natural killer cell count and plasma HIV-1 RNA load were prospectively measured at ARL diagnosis, at 1 and 3 months during and 1, 3 and 6 months after chemotherapy in twenty patients receiving HAART. Results Significant declines in T-helper cell (CD4) count, natural killer cell (CD16/CD56) and B lymphocyte count (CD19 cells) occurred during the first 3 months of chemotherapy. There was no significant alteration in the T-cytotoxic cell (CD8) count, CD4 percentage or HIV-1 RNA load during the study period. The T-helper cell and natural killer cell counts recovered to pre-treatment levels within 1 month of finishing chemotherapy. The recovery of B-cells was slower with pre-treatment levels only being achieved after 3 months. The recovery of CD4 T-cell count following completion of chemotherapy was more rapid than described for ARL patients who were not receiving concomitant HAART. Conclusions By combining chemotherapy with HAART, immune function is better maintained in the medium term. The CD4 T-cell count falls by 50% during chemotherapy and this will help to identify patients who require opportunistic infection prophylaxis during chemotherapy.

Toll-like Receptor 4 Mediates Innate Immunity to Kaposi Sarcoma Herpesvirus

The involvement of Toll-like receptor 4 (TLR4) in immunity against human herpesviruses has not been previously demonstrated. We show that infection of endothelial cells with Kaposi sarcoma herpesvirus (KSHV), a human oncogenic virus, leads to rapid suppression of TLR4 expression. This is a mechanism of immune escape as TLR4 mediates innate immunity against KSHV. In vitro, cells lacking TLR4 are more susceptible to KSHV infection, whereas activation of TLR4 protects cells from infection. In vivo, HIV-1-infected individuals carrying a mutant TLR4 allele appear more likely to have multicentric Castlemans disease, a lymphoproliferation associated with enhanced KSHV replication. ERK activation by KSHV structural proteins and the KSHV-encoded vGPCR plays a key role in the TLR4 downregulation, whereas the KSHV vIRF1 also contributes to this effect. Our findings reveal a role for TLR4 in innate immunity against herpesviruses and suggest the potential use of TLR4 agonists for the treatment of KSHV-related neoplasms.

Switch from inhibitory to activating NKG2 receptor expression in HIV-1 infection: lack of reversion with highly active antiretroviral therapy.

Background:HIV-1 infection is characterized by increase in inhibitory receptors and loss of activating receptors on natural killer (NK) cells, resulting in loss of cell activity. Exceptionally, for an inhibitory receptor, the proportion of NK cells bearing CD94-NKG2A decreases during HIV-1 infection. It is not understood whether HIV-1 itself or other concomitant infections drive these changes. Objectives:To investigate the relationship between HIV-1 viraemia and changes in C-type lectin-like receptor expression in NK cells and to investigate the effect of highly active antiretroviral therapy (HAART) on these changes. Methods:Three cohorts of patients were studied: (1) before, during and after treatment interruption in aviraemic and viraemic patients receiving HAART (n = 15); (2) HIV-1-positive treatment-naive individuals (n = 13); and (3) HIV-1-positive individuals receiving successful HAART for a minimum of 1 year without interruption (n = 11). Flow cytometry was used to study the expression of NKG2A before and after treatment interruption and to define expanded populations of NK cells in untreated and treated HIV-1-positive individuals. Assays were performed in vitro to assess the cytotoxicity of the expanded populations. Results:Increases in plasma HIV-1 RNA during treatment interruption in aviraemic HAART-treated individuals did not influence the proportion of NK cells carrying the complex CD94-NKG2A. Loss of NKG2A NK cells corresponded to the dramatic expansion of a distinct population of cells expressing a functional activating CD94-NKG2C receptor with skewed expression of killer cell immunoglobulin-like receptor family and natural cytotoxicity receptors. Conclusion:Changes in the NK cell repertoire during HIV-1 infection were not a result of HIV-1 viraemia alone but resembled those associated with concomitant infections.

Molecular quantitation of thymic output in mice and the effect of IL-7

Aging of the murine thymus is accompanied by a measurable loss of weight and cellularity and a marked reduction in its output of T lymphocytes. This study employs a molecular approach to determine changes in the output of the murine thymus using a novel assay system based on the detection and quantitation of the excised TCRδ DNA locus from within the TCRα chain genes. In α β+ T cells such δ excision circles (δEC) are present at higher levels in naive T cells as compared with memory T cell populations, are non‐replicating, and diluted within the total peripheral α β+ T cell pool with advancing age. This assay permits the assessment of thymic output in older animals where previous analysis was hampered by the transient nature ofthe naive T cell surface phenotype, and so allows the assessment of the efficacy of IL‐7 as an agent to reverse thymic atrophy. Treatment of old mice with IL‐7 although producing no overall change in the total number of α β+ T cells in the peripheral T cell pool altered the component subsets. Mice treated with IL‐7 showed increases in the number of α β+TCR cells possessing δEC commensurate with improved thymic output, and the splenic T cells from IL‐7‐treated mice performed significantly better in in vitro functional assays compared to those from age‐matched saline‐treated controls.

Kaposi's Sarcoma-Associated Herpesvirus Cytotoxic T Lymphocytes Recognize and Target Darwinian Positively Selected Autologous K1 Epitopes

ABSTRACT Kaposis sarcoma-associated herpesvirus (KSHV) is the infectious cause of Kaposis sarcoma (KS) and certain lymphoproliferations particularly in the context of human immunodeficiency virus (HIV) type 1-induced immunosuppression. The introduction of effective therapies to treat HIV has led to a decline in the incidence of KS, suggesting that immune responses may play a role in controlling KSHV infection and pathogenesis. Cytotoxic-T-lymphocyte (CTL) activity against KSHV proteins has been demonstrated; however, the identification of KSHV CTL epitopes remains elusive and problematic. Although the herpesvirus genomic layout is generally conserved, KSHV encodes a unique hypervariable protein, K1, with intense biological selection pressure at specific amino acid sites. To investigate whether this variability is partly driven by cellular immunity, we designed K1 peptides that match only the unique viral sequence for every individual studied here (autologous peptides). We identified functional CTL epitopes within K1s most variable areas, and we show that a given individual responds only to autologous peptides and not to peptides from other individuals. Furthermore, these epitopes are highly conserved sequences within KSHV isolates from a specific strain but are not conserved between different strains. We conclude that CTL recognition contributes to K1, and therefore to KSHV, evolution.