Adenosine deaminase (ADA), a protein whose deficit leads to severe combined immunodeficiency, binds to the cell surface by means of either CD26, A₁adenosine receptors, or A_2Badenosine receptors. The physiological role of these interactions is not well understood. Our results show that by a 3-fold reduction in the EC₅₀for the antigen, ADA potentiated T cell proliferation in autologous cocultures with antigen-pulsed immature or mature dendritic cells. Costimulation was not due to the enzymatic activity but to the interaction of ADA–CD26 complexes in T cells with an ADA-anchoring protein in dendritic cells. From colocalization studies, it is deduced that ADA colocalizing with adenosine receptors on dendritic cells interact with CD26 expressed on lymphocytes. This costimulatory signal in the immunological synapse leads to a marked increase (3- to 34-fold) in the production of the T helper 1 and proimmflamatory cytokines IFN-γ, TNF-α, and IL-6.

Combination antiretroviral therapy (cART) greatly improves survival and quality of life of HIV-1–infected patients; however, cART must be continued indefinitely to prevent viral rebound and associated disease progression. Inducing HIV-1–specific immune responses with a therapeutic immunization has been proposed to control viral replication after discontinuation of cART as an alternative to “cART for life.” We report safety, tolerability, and immunogenicity results associated with a control of viral replication for a therapeutic vaccine using autologous monocyte-derived dendritic cells (MD-DCs) pulsed with autologous heat-inactivated whole HIV. Patients on cART with CD4⁺ >450 cells/mm³ were randomized to receive three immunizations with MD-DCs or with nonpulsed MD-DCs. Vaccination was feasible, safe, and well tolerated and shifted the virus/host balance. At weeks 12 and 24 after cART interruption, a decrease of plasma viral load setpoint ≥1 log was observed in 12 of 22 (55%) versus 1 of 11 (9%) and in 7 of 20 (35%) versus 0 of 10 (0%) patients in the DC–HIV-1 and DC-control groups, respectively. This significant decrease in plasma viral load observed in immunized recipients was associated with a consistent increase in HIV-1–specific T cell responses. These data suggest that HIV-1–specific immune responses elicited by therapeutic DC vaccines could significantly change plasma viral load setpoint after cART interruption in chronic HIV-1–infected patients treated in early stages. This proof of concept supports further investigation of new candidates and/or new optimized strategies of vaccination with the final objective of obtaining a functional cure as an alternative to cART for life.

Background and Purpose— Monocytes participate in adaptive and innate immune responses. Monocyte numbers increase in patients with stroke associated infection (SAI) or severe stroke. Whether changes in monocytes are related to specific effects, or simply mark brain damage, remains unsettled. Methods— We used flow cytometry in 45 consecutive strokes and 12 healthy controls to assess the time course of monocytes, their phenotype, and the production of cytokines after stimulation. Cortisol, TNF-α, IFN-γ, and IL-10 were measured in serum and metanephrine in plasma. The effects of humoral and cellular parameters on the risk of SAI and poor outcome were tested in multivariate analyses adjusted for confounders (NIHSS score, age, and tube feeding). Results— Surface expression of human leukocyte antigen-DR, Toll-like receptor-2, and production of TNF-α in monocytes were independently associated with stroke. Distinct immune mechanisms were related with functional outcome and the risk of SAI; the signature of SAI included an increase of cortisol, metanephrine, and IL-10 in serum, and reduced production of TNF-α in monocytes; poor outcome was associated with increased expression of Toll-like receptor-4 in monocytes (OR, 9.61; 95% CI, 1.27–72.47). SAI did not predict poor outcome (OR, 5.63; 95% CI, 0.45–70.42; P =0.18). Conclusions— In human stroke, poor outcome is associated to innate responses mediated by Toll-like receptor-4 in monocytes. SAI may result from the immunosuppressive and antiinflammatory effects of corticoids, catecholamines, IL-10, and deactivated monocytes. Early treated SAI does not contribute significantly to additional brain damage. These findings encourage the exploration of strategies aimed to inhibit Toll-like receptor-4 signaling in acute stroke.

Adaptive immune responses begin after productive immunosynaptic contacts formation established in secondary lymphoid organs by dendritic cells (DC) presenting the Ag to T lymphocytes. Despite its resemblance to the neurosynapse, the participation of soluble small nonpeptidic mediators in the intercellular cross-talk taking place during T cell–DC interactions remains poorly studied. In this study, we show that human DC undergoing maturation and in contact with T cells release significant amounts of glutamate, which is the main excitatory neurotransmitter in mammalians. The release of glutamate is nonvesicular and mediated by the DC-expressed X_c⁻ cystine/glutamate antiporter. DC-derived glutamate stimulating the constitutively expressed metabotropic glutamate receptor 5 impairs T cell activation. However, after productive Ag presentation, metabotropic glutamate receptor 1 is expressed in T cells to mediate enhanced T cell proliferation and secretion of Th1 and proinflammatory cytokines. These data suggest that, during T cell–DC interaction, glutamate is a novel and highly effective regulator in the initiation of T cell-mediated immune responses.

Therapeutic immunization with autologous monocyte-derived dendritic cells (DCs) loaded with heat-inactivated autologous human immunodeficiency virus

A double-blinded, controlled study of vaccination of untreated patients with chronic human immunodeficiency virus type 1 (HIV-1) infection with 3 doses of autologous monocyte-derived dendritic cells (MD-DCs) pulsed with heat inactivated autologous HIV-1 was performed. Therapeutic vaccinations were feasible, safe, and well tolerated. At week 24 after first vaccination (primary end point), a modest significant decrease in plasma viral load was observed in vaccine recipients, compared with control subjects (P = .03). In addition, the change in plasma viral load after vaccination tended to be inversely associated with the increase in HIV-specific T cell responses in vaccinated patients but tended to be directly correlated with HIV-specific T cell responses in control subjects. Clinical trial.gov NCT00402142