Cristiana Cairo

Lack of CD27-CD45RA-V gamma 9V delta 2+ T cell effectors in immunocompromised hosts and during active pulmonary tuberculosis.

In humans, the circulating pool of mycobacteria-reactive Vγ9Vδ2+ T cells is expanded with age and may contribute to Mycobacterium tuberculosis immunosurveillance. We observed that two subsets of Vγ9Vδ2+ T cells could be identified on the basis of CD27 expression in immunocompetent adults, showing that functionally differentiated γδ T cells have lost CD27 expression. In contrast, the CD27−CD45RA−Vγ9Vδ2+ T cell subset of effector cells was absent in cord blood cells from healthy newborns and lacking in the peripheral blood from HIV-infected patients. Moreover, circulating Vγ9Vδ2+ T cell effectors were significantly reduced in patients with acute pulmonary tuberculosis, resulting in a reduced frequency of IFN-γ-producing cells after stimulation with nonpeptidic mycobacterial ligands. These observations indicate that monitoring and boosting γδ T cell effectors could be clinically relevant both in immunocompromised hosts and during active tuberculosis disease.

Safety, immunogenicity, and efficacy of the ML29 reassortant vaccine for Lassa fever in small non-human primates

A single injection of ML29 reassortant vaccine for Lassa fever induces low, transient viremia, and low or moderate levels of ML29 replication in tissues of common marmosets depending on the dose of the vaccination. The vaccination elicits specific immune responses and completely protects marmosets against fatal disease by induction of sterilizing cell-mediated immunity. DNA array analysis of human peripheral blood mononuclear cells from healthy donors exposed to ML29 revealed that gene expression patterns in ML29-exposed PBMC and control, media-exposed PBMC, clustered together confirming safety profile of the ML29 in non-human primates. The ML29 reassortant is a promising vaccine candidate for Lassa fever.

Gamma Interferon Secretion by Human Vγ2Vδ2 T Cells after Stimulation with Antibody against the T-Cell Receptor plus the Toll-Like Receptor 2 Agonist Pam3Cys

ABSTRACT Circulating Vγ2Vδ2 T-cell populations in healthy human beings are poised for rapid responses to bacterial or viral pathogens. We asked whether Vγ2Vδ2 T cells use the Toll-like receptor (TLR) family to recognize pathogen-associated molecular pattern molecules and to regulate cell functions. Analysis of expanded Vγ2Vδ2 T-cell lines showed the abundant presence of TLR2 mRNA, implying that these receptors are important for cell differentiation or function. However, multiple efforts to detect TLR2 protein on the cell surface or in cytoplasmic compartments gave inconsistent results. Functional assays confirmed that human Vγ2Vδ2 T cells could respond to the TLR2 agonist (S)-(2,3-bis(palmitoyloxy)-(2RS)-propyl)-N-palmitoyl-(R)-Cys-(S)-Ser(S)-Lys4-OH trihydrochloride (Pam3Cys), but the response required coincident stimulation through the γδ T-cell receptor (TCR). Dually stimulated cells produced higher levels of cytoplasmic or cell-free gamma interferon and showed increased expression of the lysosome-associated membrane protein CD107a on the cell surface. A functional TLR2 that requires coincident TCR stimulation may increase the initial potency of Vγ2Vδ2 T-cell responses at the site of infection and promote the rapid development of subsequent acquired antipathogen immunity.

Natural viral suppressors of HIV-1 have a unique capacity to maintain γδ T cells

Objective:To evaluate Vγ2Vδ2 T cells in a group of HIV-infected patients who suppress HIV replication without antiretroviral therapy (natural viral suppressors, NVSs). Design:It is a cross-sectional study. Methods:We compared Vγ2Vδ2 T-cell frequency, T-cell repertoire, and responses to isopentenyl pyrophosphate stimulation between NVSs (n = 21) and HIV-uninfected controls (n = 27) and between NVSs and HIV-infected patients taking HAART with suppressed viral replication (HIV-P; n = 25). Results:NVSs had a mean frequency of 1.06 ± 0.82% CD3+Vδ2+ cells among total lymphocytes, which was significantly higher than both control groups (HIV-negative: 0.50 ± 0.53%, P = 0.042; HIV-P: 0.34 ± 0.37%, P = 0.002). The proportion of Vγ2 chains correlating with the Vγ2-Jγ1.2 rearrangement was reduced among NVSs compared with HIV-negative controls (0.57 ± 0.06 vs. 0.32 ± 0.04; P = 0.016) but was increased compared with HIV-P patients (0.32 ± 0.04 vs. 0.22 ± 0.03; P = 0.03). NVSs had a similar baseline frequency of CD27−/CD45RA− effector cells (19.6 ± 4.2%) compared with HIV-negative controls (20.8 ± 12.9%; P = 0.35). Conclusion:The altered γδ T-cell receptor repertoire among NVS was consistent with the known effect of HIV-1 on these cells. Uniquely among all HIV-infected groups, NVS reconstituted the γδ T-cell population, eventually reaching levels significantly above controls. This capacity to recover γδ T-cell numbers and function distinguishes individuals who control HIV-1 with and without HAART.

γδ T Cells in HIV Disease: Past, Present, and Future

Human immunodeficiency virus (HIV) type 1 dysregulates γδ T cells as part of an immune evasion mechanism. Nearly three decades of research defined the effects of HIV on γδ T cells and how this impacts disease. With highly effective antiretroviral therapy providing virus suppression and longer survival, we expected a return to normal for γδ T cells. This is not the case. Even in patients with CD4 T cell reconstitution, normal γδ T cell levels and function are not recovered. The durable damage to Vδ2 T cells is paralleled by defects in NK, CD8 T cells, and dendritic cells. Whether these consequences of HIV stem from similar or distinct mechanisms are not known and effective means for recovering the full range of cellular immunity have not been discovered. These unanswered questions receive too little attention in the overall program of efforts to cure HIV this disease. Approved drugs capable of increasing Vδ2 T cell function are being tested in clinical trials for cancer and hold promise for restoring normal function in patients with HIV disease. The impetus for conducting clinical trials will come from understanding the significance of γδ T cells in HIV disease and what might be gained from targeted immunotherapy. This review traces the history and current progress of AIDS-related research on γδ T cells. We emphasize the damage to γδ T cells that persists despite effective virus suppression. These chronic immune deficits may be linked to the comorbidities of AIDS (cancer, cardiovascular disease, metabolic disease, and others) and will hinder efforts to eradicate HIV by cytotoxic T or NK cell killing. Here, we focus on one subset of T cells that may be critical in the pathogenesis of HIV and an attractive target for new immune-based therapies.

Impact of age, gender, and race on circulating γδ T cells

A major subset of human peripheral blood γδ T cells expresses the Vγ2Vδ2 T cell receptor and responds to malignant or infectious diseases. We noted significant differences in the numbers of Vγ2Vδ2 T cells in blood samples from healthy Caucasian CA or African American (AA) donors. On average, CA donors had 3.71% ± 4.37% Vδ2 cells (as a percentage of total lymphocytes) compared with 1.18% ± 2.14% Vδ2 cells for AA donors (p < 0.0001). Age and race had the greatest impact on Vδ2 cell levels; the effect of age was similar for both racial groups. The Vδ2 cell population was dominated, for both donor groups, by cells expressing the Vγ2-Jγ1.2 Vδ2 T cell receptor, an apparent result of strong positive selection and there was substantial overlap in the public Vγ2 clonotypes from both racial groups. Mechanisms for selection and amplification of Vδ2 cells are nearly identical for both groups, despite the significant difference in baseline levels. These data show that appropriate controls, matched for age and race, may be required for clinical studies of Vγ2Vδ2 T cells in infectious disease or cancer and raise important questions about the mechanisms regulating the levels of circulating Vδ2 cells.

Impacts of HIV infection on Vγ2Vδ2 T cell phenotype and function: a mechanism for reduced tumor immunity in AIDS

HIV infection causes rapid and lasting defects in the population of Vγ2Vδ2 T cells. To fully describe the impact of HIV, we examined PBMC samples from HIV+ patients receiving highly active antiretroviral therapy, who had displayed prolonged viral control and CD4 counts above 300 cells/mm3. We observed lower frequencies of CD27–/CD45RA– Vγ2Vδ2 cells in HIV+ individuals when compared with controls, coupled with an increased proportion of CD45RA+ cells. These changes were common among 24 HIV+ patients and were not related to CD4 cell count or viral RNA burden. Vγ2 cells from HIV+ individuals had lower expression of Granzyme B and displayed reduced cytotoxicity against Daudi targets after in vitro stimulation. There was increased expression of FasR (CD95) on Vγ2 cells from HIV+ PBMC that may be a mechanism for depletion of Vγ2 cells during disease. In addition to the well‐characterized defects in the Vγ2 repertoire and functional responses to phosphoantigen, the proportion of CD27–/CD45RA– Vγ2Vδ2 T cells after isopentenyl pyrophosphate stimulation was reduced sharply in HIV+ donors versus controls. Thus, HIV infection has multiple impacts on the circulating Vγ2Vδ2 T cell population that combine to reduce the potential effector activity in terms of tumor cytotoxicity. Changes in Vγ2Vδ2 T cells, along with concomitant effects on NK and NKT cells that also contribute to tumor surveillance, may be important factors for elevating the risk of malignancy during AIDS.

Failure to restore the Vγ2-Jγ1.2 repertoire in HIV-infected men receiving highly active antiretroviral therapy (HAART)

Gammadelta (gammadelta) T cells expressing the Vgamma2-Jgamma1.2Vdelta2 (Vgamma9-JPVdelta2, alternate nomenclature) T cell receptor (TCR) constitute the major peripheral blood population of gammadelta T cells in adult humans and are specifically depleted during human immunodeficiency virus (HIV) disease. Vgamma2-Jgamma1.2Vdelta2 T cells provide a convenient model for assessing the impact of antiretroviral therapy on cell populations that are not susceptible to direct infection because they do not express CD4 and depletion occurs by indirect mechanisms. We obtained longitudinal PBMC samples from 16 HIV-infected individuals who enrolled in the Multicenter AIDS Cohort Study (MACS) and were starting highly active antiretroviral therapy (HAART). Vgamma2-Jgamma1.2Vdelta2 T cells were depleted in these individuals as a result of HIV infection. Despite evidence for clinical benefits of HAART, the Vgamma2-Jgamma1.2Vdelta2 T cell repertoire did not recover after HAART initiation irrespective of treatment duration. These studies highlight important defects among cell subsets lost due to indirect effects of HIV.

Individual Vγ2-Jγ1.2+ T cells respond to both isopentenyl pyrophosphate and Daudi cell stimulation: generating tumor effectors with low molecular weight phosphoantigens

Human Vγ2Vδ2 T cells exhibit T cell receptor-dependent, MHC-unrestricted recognition of antigen and play important roles in tumor and pathogen immunity. To characterize antigen recognition by the Vγ2Vδ2 TCR, we used the combined approach of spectratyping and CDR3 sequence analysis that measures changes in the TCR repertoire before and after stimulation with a phosphoantigen (isopentenyl pyrophosphate) or an irradiated tumor cell line (Daudi B lymphoma). Here we describe common Vγ2 chains that are substantially involved in the response to both phosphoantigens and tumor cells. The recognition properties of common Vγ2 chains explains the observation that Vγ2Vδ2 T cells expanded by phosphoantigen stimulation specifically recognize and kill some but not all tumor cell lines. Our studies further justify efforts to stimulate tumor immunity by administering low molecular weight phosphoantigens and boosting the frequency and tumor effector functions of circulating Vγ2Vδ2 T cells.

Control of CD56 expression and tumor cell cytotoxicity in human Vγ2Vδ2 T cells

BackgroundIn lymphocyte subsets, expression of CD56 (neural cell adhesion molecule-1) correlates with cytotoxic effector activity. For cells bearing the Vγ2Vδ2 T cell receptor, isoprenoid pyrophosphate stimulation leads to uniform activation and proliferation, but only a fraction of cells express CD56 and display potent cytotoxic activity against tumor cells. Our goal was to show whether CD56 expression was regulated stochastically, similar to conventional activation antigens, or whether CD56 defined a lineage of cells committed to the cytotoxic phenotype.ResultsTracking individual cell clones defined by their Vγ2 chain CDR3 region sequences, we found that CD56 was expressed on precursor cytotoxic T cells already present in the population irrespective of their capacity to proliferate after antigen stimulation. Public T cell receptor sequences found in the CD56+ subset from one individual might appear in the CD56- subset of another donor. The commitment of individual clones to CD56+ or CD56- lineages was stable for each donor over a 1 year interval.ConclusionThe ability to express CD56 was not predicted by TCR sequence or by the strength of signal received by the TCR. For γδ T cells, cytotoxic effector function is acquired when cytotoxic precursors within the population are stimulated to proliferate and express CD56. Expression of CD56 defines a committed lineage to the cytotoxic phenotype.