Immune-profiling of innate and adaptive immunity following three vaccinations of the MERS vaccine candidate MVA-MERS-S

Middle East Respiratory Syndrome (MERS) is a respiratory disease caused by MERS coronavirus (MERS-CoV). In follow-up to a phase 1 trial, we performed a longitudinal analysis of immune responses following immunization with the Modified Vaccinia virus Ankara (MVA)-based vaccine MVA-MERS-S encoding MERS-CoV-spike protein. Three homologous intramuscular immunizations were administered on days 0 and 28 with a late booster vaccination at 12±4 months. Vaccination with MVA-MERS-S revealed a benign safety profile. No serious or severe adverse events were reported. Here, we analyzed innate and adaptive immune responses to the MVA-MERS-S in ten vaccinees. For this approach, blood samples were collected frequently for a period of about three years. Serum, plasma and PBMCs were analyzed at multiple time points using different techniques, which allowed an in-depth characterization of immune responses elicited by MVA-MERS-S. Please click Download on the upper right corner to see the full abstract

CD8+ T lymphocyte responses target functionally important regions of Protease and Integrase in HIV-1 infected subjects

BACKGROUND: CD8+ T cell responses are known to be important to the control of HIV-1 infection. While responses to reverse transcriptase and most structural and accessory proteins have been extensively studied, CD8 T cell responses specifically directed to the HIV-1 enzymes Protease and Integrase have not been well characterized, and few epitopes have been described in detail. METHODS: We assessed comprehensively the CD8 T cell responses to synthetic peptides spanning Protease and Integrase in 56 HIV-1 infected subjects with acute, chronic, or controlled infection using IFN-γ-Elispot assays and intracellular cytokine staining. Fine-characterization of novel CTL epitopes was performed on peptide-specific CTL lines in Elispot and (51)Chromium-release assays. RESULTS: Thirteen (23%) and 38 (68%) of the 56 subjects had detectable responses to Protease and Integrase, respectively, and together these targeted most regions within both proteins. Sequence variability analysis confirmed that responses cluster largely around conserved regions of Integrase, but responses against a large, highly conserved region of the N-terminal DNA-binding domain of Integrase were not readily detected. CD8 T cell responses targeted regions of Protease that contain known Protease inhibitor mutation residues, but strong Protease-specific CD8 T cell responses were rare. Fine-mapping of targeted epitopes allowed the identification of three novel, HLA class I-restricted, frequently-targeted optimal epitopes. There were no significant correlations between CD8 T cell responses to Protease and Integrase and clinical disease category in the study subjects, nor was there a correlation with viral load. CONCLUSIONS: These findings confirm that CD8 T cell responses directed against HIV-1 include potentially important functional regions of Protease and Integrase, and that pharmacologic targeting of these enzymes will place them under both drug and immune selection pressure

Identification of a Spike-Specific CD8⁺ T-Cell Epitope Following Vaccination Against the Middle East Respiratory Syndrome Coronavirus in Humans

Licensed vaccines against the Middle East respiratory syndrome coronavirus (MERS-CoV), an emerging pathogen of concern, are lacking. The modified vaccinia virus Ankara vector-based vaccine MVA-MERS-S, expressing the MERS-CoV-spike glycoprotein (MERS-S), is one of 3 candidate vaccines in clinical development and elicits robust humoral and cellular immunity. Here, we identified for the first time a MERS-S-specific CD8+ T-cell epitope in an HLA-A∗03:01/HLA-B∗35:01-positive vaccinee using a screening assay, intracellular cytokine staining, and in silico epitope prediction. As evidence from MERS-CoV infection suggests a protective role of long-lasting CD8+ T-cell responses, the identification of epitopes will facilitate longitudinal analyses of vaccine-induced T-cell immunity.</p

Lack of Detectable HIV-1–Specific CD8+ T Cell Responses in Zambian HIV-1–Exposed Seronegative Partners of HIV-1–Positive Individuals

Human immunodeficiency virus type 1 (HIV-1)–specific T cell responses were characterized in a blinded study involving infected individuals and their seronegative exposed uninfected (EU) partners from Lusaka, Zambia. HIV-1–specific T cell responses were detected ex vivo in all infected individuals and amplified, on average, 27-fold following in vitro expansion. In contrast, no HIV-1–specific T cell responses were detected in any of the EU partners ex vivo or following in vitro expansion. These data demonstrate that the detection of HIV-1–specific T cell immunity in EU individuals is not universal and that alternative mechanisms may account for protection in these individuals

Limited Durability of Viral Control following Treated Acute HIV Infection

BACKGROUND: Early treatment of acute HIV infection with highly active antiretroviral therapy, followed by supervised treatment interruption (STI), has been associated with at least transient control of viremia. However, the durability of such control remains unclear. Here we present longitudinal follow-up of a single-arm, open-label study assessing the impact of STI in the setting of acute HIV-1 infection. METHODS AND FINDINGS: Fourteen patients were treated during acute HIV-1 infection and subsequently subjected to an STI protocol that required retreatment if viral load exceeded 50,000 RNA copies/ml plasma or remained above 5,000 copies/ml for more than three consecutive weeks. Eleven of 14 (79%) patients were able to achieve viral loads of less than 5,000 RNA copies/ml for at least 90 d following one, two, or three interruptions of treatment. However, a gradual increase in viremia and decline in CD4+ T cell counts was observed in most individuals. By an intention-to-treat analysis, eight (57%), six (43%), and three (21%) of 14 patients achieved a maximal period of control of 180, 360, and 720 d, respectively, despite augmentation of HIV-specific CD4+ and CD8+ T cell responses. The magnitude of HIV-1-specific cellular immune responses before treatment interruption did not predict duration of viremia control. The small sample size and lack of concurrent untreated controls preclude assessment of possible clinical benefit despite failure to control viremia by study criteria. CONCLUSIONS: These data indicate that despite initial control of viremia, durable viral control to less than 5,000 RNA copies/ml plasma in patients following treated acute HIV-1 infection occurs infrequently. Determination of whether early treatment leads to overall clinical benefit will require a larger and randomized clinical trial. These data may be relevant to current efforts to develop an HIV-1 vaccine designed to retard disease progression rather than prevent infection since they indicate that durable maintenance of low-level viremia may be difficult to achieve

Loss of HIV-1–specific CD8+ T Cell Proliferation after Acute HIV-1 Infection and Restoration by Vaccine-induced HIV-1–specific CD4+ T Cells

Virus-specific CD8+ T cells are associated with declining viremia in acute human immunodeficiency virus (HIV)1 infection, but do not correlate with control of viremia in chronic infection, suggesting a progressive functional defect not measured by interferon γ assays presently used. Here, we demonstrate that HIV-1–specific CD8+ T cells proliferate rapidly upon encounter with cognate antigen in acute infection, but lose this capacity with ongoing viral replication. This functional defect can be induced in vitro by depletion of CD4+ T cells or addition of interleukin 2–neutralizing antibodies, and can be corrected in chronic infection in vitro by addition of autologous CD4+ T cells isolated during acute infection and in vivo by vaccine-mediated induction of HIV-1–specific CD4+ T helper cell responses. These data demonstrate a loss of HIV-1–specific CD8+ T cell function that not only correlates with progressive infection, but also can be restored in chronic infection by augmentation of HIV-1–specific T helper cell function. This identification of a reversible defect in cell-mediated immunity in chronic HIV-1 infection has important implications for immunotherapeutic interventions