Multiple T-cell responses to human immunodeficiency virus type 1 are enhanced by dendritic cells

Gag-Specific CD4 T Cell Proliferation, Plasmacytoid Dendritic Cells, and Ethnicity in Perinatally HIV-1-Infected Youths: The ANRS-EP38-IMMIP Study

In perinatally HIV-1-infected youths living in France, we previously reported that Gag-specific CD4 and CD8 T cell proliferation is more frequently detected in patients of black ethnicity than in those of other ethnicities. We observed that black patients had higher levels of dendritic cells (DCs) than other patients. We aimed at studying the association of DC levels with Gag-specific T cell proliferation. The ANRS-EP38-IMMIP study is an observational study of youths aged between 15 and 24 years who were perinatally infected with HIV. A single blood sample was drawn for virological and immunological assays. Data from cART-treated 53 youths with undetectable plasma HIV RNA were analyzed. Gag-specific T cell proliferation was assessed by using a CFSE-based test. Peripheral blood myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs) were phenotyped by flow cytometry. Plasma markers were quantified by ELISA or multiplex assays. Logistic regression was used for univariate and multivariate analyses. Patients with Gag-specific CD4 T cell proliferative responses had significantly higher percentages and absolute counts of mDCs and pDCs in the peripheral blood than nonresponding patients. Gag-specific CD4 and CD8 T cell proliferation was associated with lower plasma sCD14 levels. Plasma levels of IFN-α, TRAIL, and chemokines involved in T cell migration to secondary lymphoid organs were not associated with T cell proliferation. Multivariate analysis confirmed the association between Gag-specific CD4 T cell proliferation and pDC levels. In conclusion, DC levels are a robust correlate of the presence of Gag-specific T cell proliferation in successfully treated youths.

Effective Cytotoxic T Lymphocyte Targeting of Persistent HIV-1 during Antiretroviral Therapy Requires Priming of Naive CD8+ T Cells

Curing HIV-1 infection will require elimination of persistent cellular reservoirs that harbor latent virus in the face of combination antiretroviral therapy (cART). Proposed immunotherapeutic strategies to cure HIV-1 infection include enhancing lysis of these infected cells by cytotoxic T lymphocytes (CTL). A major challenge in this strategy is overcoming viral immune escape variants that have evaded host immune control. Here we report that naive CD8⁺ T cells from chronic HIV-1-infected participants on long-term cART can be primed by dendritic cells (DC). These DC must be mature, produce high levels of interleukin 12p70 (IL-12p70), be responsive to CD40 ligand (CD40L), and be loaded with inactivated, autologous HIV-1. These DC-primed CD8⁺ T cell responders produced high levels of gamma interferon (IFN-γ) in response to a broad range of both conserved and variable regions of Gag and effectively killed CD4⁺ T cell targets that were either infected with the autologous latent reservoir-associated virus or loaded with autologous Gag peptides. In contrast, HIV-1-specific memory CD8⁺ T cells stimulated with autologous HIV-1-loaded DC produced IFN-γ in response to a narrow range of conserved and variable Gag peptides compared to the primed T cells and most notably, displayed significantly lower cytolytic function. Our findings highlight the need to selectively induce new HIV-1-specific CTL from naive precursors while avoiding activation of existing, dysfunctional memory T cells in potential curative immunotherapeutic strategies for HIV-1 infection.

Current immunotherapeutic approaches aim to enhance antiviral immunity against the HIV-1 reservoir; however, it has yet to be shown whether T cells from persons on cART can recognize and eliminate virus-infected cells. We show that in persons on cART a personalized medicine approach using their dendritic cells to stimulate their naive T cells induces potent effector CTL in vitro that recognize and eradicate HIV-1-infected CD4⁺ T cells. Additionally, we show that the same stimulation of existing memory T cells results in cytokine secretion but limited effector function. Our study demonstrates that the naive T cell repertoire can recognize persistent HIV-1 during cART and supports immunotherapy strategies for an HIV-1 cure that targets naive T cells, rather than existing, dysfunctional, memory T cells.

Programming T cell Killers for an HIV Cure: Teach the New Dogs New Tricks and Let the Sleeping Dogs Lie

Despite the success of combination antiretroviral therapy (cART), a latent viral reservoir persists in HIV-1-infected persons. Unfortunately, endogenous cytotoxic T lymphocytes (CTLs) are unable to control viral rebound when patients are removed from cART. A "kick and kill" strategy has been proposed to eradicate this reservoir, whereby infected T cells are induced to express viral proteins via latency-inducing drugs followed by their elimination by CTLs. It has yet to be determined if stimulation of existing HIV-1-specific CTL will be sufficient, or if new CTLs should be primed from naïve T cells. In this review, we propose that dendritic cells (DCs), the most potent antigen presenting cells, act as dog trainers and can induce T cells (the dogs) to do magnificent tricks. We propose the hypothesis that an HIV-1 cure will require targeting of naïve T cells and will necessitate "teaching new dogs new tricks" while avoiding activation of potentially dysfunctional endogenous memory CTLs (letting the sleeping dogs lie).

Rapid generation of clinical-grade antiviral T cells: selection of suitable T-cell donors and GMP-compliant manufacturing of antiviral T cells

Background

The adoptive transfer of allogeneic antiviral T lymphocytes derived from seropositive donors can safely and effectively reduce or prevent the clinical manifestation of viral infections or reactivations in immunocompromised recipients after hematopoietic stem cell (HSCT) or solid organ transplantation (SOT). Allogeneic third party T-cell donors offer an alternative option for patients receiving an allogeneic cord blood transplant or a transplant from a virus-seronegative donor and since donor blood is generally not available for solid organ recipients. Therefore we established a registry of potential third-party T-cell donors (allogeneic cell registry, alloCELL) providing detailed data on the assessment of a specific individual memory T-cell repertoire in response to antigens of cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus (ADV), and human herpesvirus (HHV) 6.

Methods

To obtain a manufacturing license according to the German Medicinal Products Act, the enrichment of clinical-grade CMV-specific T cells from three healthy CMV-seropositive donors was performed aseptically under GMP conditions using the CliniMACS cytokine capture system (CCS) after restimulation with an overlapping peptide pool of the immunodominant CMVpp65 antigen. Potential T-cell donors were selected from alloCELL and defined as eligible for clinical-grade antiviral T-cell generation if the peripheral fraction of IFN-γ⁺ T cells exceeded 0.03% of CD3⁺ lymphocytes as determined by IFN-γ cytokine secretion assay.

Results

Starting with low concentration of IFN-γ⁺ T cells (0.07-1.11%) we achieved 81.2%, 19.2%, and 63.1% IFN-γ⁺CD3⁺ T cells (1.42 × 10⁶, 0.05 × 10⁶, and 1.15 × 10⁶) after enrichment. Using the CMVpp65 peptide pool for restimulation resulted in the activation of more CMV-specific CD8⁺ than CD4⁺ memory T cells, both of which were effectively enriched to a total of 81.0% CD8⁺IFN-γ⁺ and 38.4% CD4⁺IFN-γ⁺ T cells. In addition to T cells and NKT cells, all preparations contained acceptably low percentages of contaminating B cells, granulocytes, monocytes, and NK cells. The enriched T-cell products were stable over 72 h with respect to viability and ratio of T lymphocytes.

Conclusions

The generation of antiviral CD4⁺ and CD8⁺ T cells by CliniMACS CCS can be extended to a broad spectrum of common pathogen-derived peptide pools in single or multiple applications to facilitate and enhance the efficacy of adoptive T-cell immunotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0336-5) contains supplementary material, which is available to authorized users.

Dendritic cells restore CD8+ T cell reactivity to autologous HIV-1

Recall T cell responses to HIV-1 antigens are used as a surrogate for endogenous cellular immune responses generated during infection. Current methods of identifying antigen-specific T cell reactivity in HIV-1 infection use bulk peripheral blood mononuclear cells (PBMC) yet ignore professional antigen-presenting cells (APC) that could reveal otherwise hidden responses. In the present study, peptides representing autologous variants of major histocompatibility complex (MHC) class I-restricted epitopes from HIV-1 Gag and Env were used as antigens in gamma interferon (IFN-γ) enzyme-linked immunosorbent spot (ELISpot) and polyfunctional cytokine assays. Here we show that dendritic cells (DC) enhanced T cell reactivity at all stages of disease progression but specifically restored T cell reactivity after combination antiretroviral therapy (cART) to early infection levels. Type 1 cytokine secretion was also enhanced by DC and was most apparent late post-cART. We additionally show that DC reveal polyfunctional T cell responses after many years of treatment, when potential immunotherapies would be implemented. These data underscore the potential efficacy of DC immunotherapy that aims to awaken a dormant, autologous, HIV-1-specific CD8+ T cell response.

IMPORTANCE

Assessment of endogenous HIV-1-specific T cell responses is critical for generating immunotherapies for subjects on cART. Current assays ignore the ability of dendritic cells to reveal these responses and may therefore underestimate the breadth and magnitude of T cell reactivity. As DC do not prime new responses in these assays, it can be assumed that the observed responses are not detected without appropriate stimulation. This is important because dogma states that HIV-1 mutates to evade host recognition and that CD8+ cytotoxic T lymphocyte (CTL) failure is due to the inability of T cells to recognize the autologous virus. The results presented here indicate that responses to autologous virus are generated during infection but may need additional stimulation to be effective. Detecting the breadth and magnitude of HIV-1-specific T cell reactivity generated in vivo is of the utmost importance for generating effective DC immunotherapies.

Retrocyclin RC-101 blocks HIV-1 transmission across cervical mucosa in an organ culture

BACKGROUND

Cervical tissue-based organ cultures have been used successfully to evaluate microbicides for toxicity and antiviral activity. The antimicrobial peptide retrocyclin RC-101 has been shown to have potent anti-HIV activity in cell culture.

OBJECTIVE

To evaluate RC-101 in organ culture for toxicity and its ability to block HIV-1 transmission across cervical mucosa.

METHODS

A cervical tissue-based organ culture was used to measure antiviral activity of RC-101. Cytotoxicity in tissues was determined by immunostaining of cellular proteins and by measuring inflammatory cytokines using real-time reverse transcriptase-polymerase chain reaction and Luminex technology.

RESULTS

RC-101 blocked transmission of both R5 and X4 HIV-1 across cervical mucosa in this organ culture model. Furthermore, film-formulated RC-101 exhibited potent antiviral activity in organ culture. Such antiviral activity of RC-101 was retained in the presence of semen and vaginal fluid. RC-101 showed no cytotoxicity in cervical tissue. Furthermore, RC-101 did not induce proinflammatory cytokine response in tissues. RC-101 also did not have any effect on natural killer cell activity and proliferation of CD4 and CD8 cells and did not show chemotactic activity.

CONCLUSIONS

Therefore, because of strong antiviral activity and low cytotoxicity in cervical tissues, RC-101 should be considered as an excellent microbicide candidate against HIV-1.

Dendritic cells reveal a broad range of MHC class I epitopes for HIV-1 in persons with suppressed viral load on antiretroviral therapy

Background

HIV-1 remains sequestered during antiretroviral therapy (ART) and can resume high-level replication upon cessation of ART or development of drug resistance. Reactivity of memory CD8⁺ T lymphocytes to HIV-1 could potentially inhibit this residual viral replication, but is largely muted by ART in relation to suppression of viral antigen burden. Dendritic cells (DC) are important for MHC class I processing and presentation of peptide epitopes to memory CD8⁺ T cells, and could potentially be targeted to activate memory CD8⁺ T cells to a broad array of HIV-1 epitopes during ART.

Principal Findings

We show for the first time that HIV-1 peptide-loaded, CD40L-matured DC from HIV-1 infected persons on ART induce IFN gamma production by CD8⁺ T cells specific for a much broader range and magnitude of Gag and Nef epitopes than do peptides without DC. The DC also reveal novel, MHC class I restricted, Gag and Nef epitopes that are able to induce polyfunctional T cells producing various combinations of IFN gamma, interleukin 2, tumor necrosis factor alpha, macrophage inhibitory protein 1 beta and the cytotoxic de-granulation molecule CD107a.

Significance

There is an underlying, broad antigenic spectrum of anti-HIV-1, memory CD8⁺ T cell reactivity in persons on ART that is revealed by DC. This supports the use of DC-based immunotherapy for HIV-1 infection.

Monofunctional and polyfunctional CD8+ T cell responses to human herpesvirus 8 lytic and latency proteins

Human herpesvirus 8 (HHV-8) is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. It is postulated that CD8(+) T cell responses play an important role in controlling HHV-8 infection and preventing development of disease. In this study, we investigated monofunctional and polyfunctional CD8(+) T cell responses to HHV-8 lytic proteins gB (glycoprotein B) and K8.1 and latency proteins LANA-1 (latency-associated nuclear antigen-1) and K12. On the basis of our previous findings that dendritic cells (DC) reveal major histocompatibility complex (MHC) class I epitopes in gB, we used a DC-based system to identify 2 novel epitopes in gB, 2 in K8.1, 5 in LANA-1, and 1 in K12. These new HHV-8 epitopes activated monofunctional and polyfunctional CD8(+) T cells that produced various combinations of gamma interferon, interleukin 2, tumor necrosis factor alpha, macrophage inhibitory protein 1β, and cytotoxic degranulation marker CD107a in healthy HHV-8-seropositive individuals. We were also able to detect HHV-8-specific CD8(+) T cells in peripheral blood samples using HLA A*0201 pentamer complexes for one gB epitope, one K8.1 epitope, two LANA-1 epitopes, and one K12 epitope. These immunogenic regions of viral lytic and latency proteins could be important in T cell control of HHV-8 infection.

Regulatory T cell suppression of Gag-specific CD8 T cell polyfunctional response after therapeutic vaccination of HIV-1-infected patients on ART

We tested the hypothesis that therapeutic vaccination against HIV-1 can increase the frequency and suppressive function of regulatory, CD4⁺ T cells (Treg), thereby masking enhancement of HIV-1-specific CD8⁺ T cell response. HIV-1-infected subjects on antiretroviral therapy (N = 17) enrolled in a phase I therapeutic vaccine trial received 2 doses of autologous dendritic cells (DC) loaded with HIV-1 peptides. The frequency of CD4⁺CD25^hiFOXP3⁺ Treg in blood was determined prior to and after vaccination in subjects and normal controls. Polyfunctional CD8⁺ T cell responses were determined pre- and post-vaccine (N = 7) for 5 immune mediators after in vitro stimulation with Gag peptide, staphylococcal enterotoxin B (SEB), or medium alone. Total vaccine response (post-vaccine–pre-vaccine) was compared in the Treg(+) and Treg-depleted (Treg-) sets. After vaccination, 12/17 subjects showed a trend of increased Treg frequency (P = 0.06) from 0.74% to 1.2%. The increased frequency did not correlate with CD8⁺ T cell vaccine response by enzyme linked immunosorbent assay for interferon γ production. Although there was no significant change in CD8⁺ T cell polyfunctional response after vaccination, Treg depletion increased the polyfunctionality of the total vaccine response (P = 0.029), with a >2-fold increase in the percentage of CD8⁺ T cells producing multiple immune mediators. In contrast, depletion of Treg did not enhance polyfunctional T cell response to SEB, implying specificity of suppression to HIV-1 Gag. Therapeutic immunization with a DC-based vaccine against HIV-1 caused a modest increase in Treg frequency and a significant increase in HIV-1-specific, Treg suppressive function. The Treg suppressive effect masked an increase in the vaccine-induced anti-HIV-1-specific polyfunctional response. The role of Treg should be considered in immunotherapeutic trials of HIV-1 infection.