Interleukin-7 (IL-7), the principal cytokine implicated in thymopoiesis and peripheral T-cell homeostasis, is presently under evaluation in human diseases characterized by persistent lymphopenia. Unexpectedly, before the eventual IL-7-driven T-cell expansion, all treated patients showed a profound T-cell depletion 24 hours after injection. The current study uses the rhesus macaque model to investigate the mechanisms involved in this IL-7-induced T-cell depletion. We identify a new critical function of IL-7 that induces massive and rapid T-cell migration from the blood into various organs, including lymph nodes, parts of the intestine, and the skin. This homing process was initiated after the induction of chemokine receptor expression by circulating T cells and the production of corresponding chemokines in target organs. Finally, we demonstrate that the IL-7-induced cell cycling is initiated within these organs before T cells migrate back into the bloodstream, indicating that T-cell homing is required for in vivo IL-7 function. (Blood. 2009;114:816-825)

Universal CAR T-cell therapies are poised to revolutionize cancer treatment and to improve patient outcomes. However, realizing these advantages in an allogeneic setting requires universal CAR T-cells that can kill target tumor cells, avoid depletion by the host immune system, and proliferate without attacking host tissues. Here, we describe the development of a novel immune-evasive universal CAR T-cells scaffold using precise TALEN-mediated gene editing and DNA matrices vectorized by recombinant adeno-associated virus 6. We simultaneously disrupt and repurpose the endogenous TRAC and B2M loci to generate TCRαβ- and HLA-ABC-deficient T-cells expressing the CAR construct and the NK-inhibitor named HLA-E. This highly efficient gene editing process enables the engineered T-cells to evade NK cell and alloresponsive T-cell attacks and extend their persistence and antitumor activity in the presence of cytotoxic levels of NK cell in vivo and in vitro, respectively. This scaffold could enable the broad use of universal CAR T-cells in allogeneic settings and holds great promise for clinical applications.

Thymopoiesis is deeply impacted from the first days of SIV infection. Reduced thymocyte proliferation - a time-consuming process - together with modified chemokine networks is consistent with thymocyte differentiation speed-up. This may transiently enhance thymic output, thus increasing naive T-cell counts and diversity and the immune competence of the host. Nonetheless, long-lasting modification of thymic physiology may lead to thymic exhaustion, as observed in late primary HIV infection.

Interferon-␣ (IFN-␣)-based therapy ispresently the standard treatment for hepatitis C virus (HCV)-infected patients. Despite good effectiveness, this cytokine is associated with major side effects, including significant lymphopenia, that limits its use for HIV/HCV-coinfected patients. Interleukin-7 (IL-7) has recently shown therapeutic potential and safety in several clinical trials designed to demonstrate T-cell restoration in immunodeficient patients. The purpose of this study was to evaluate, in simian immunodeficiency virus-infected rhesus macaques, the relevance of IL-7 therapy as a means to overcoming IFN-␣-induced lymphopenia. We showed that low-dose IFN-␣ treatment induced strong lymphopenia in chronically infected monkeys. In contrast, high-dose IFN-␣ treatment stimulated IL-7 production, leading to increased circulating T-cell counts. Moreover, IL-7 therapy more than abrogated the lymphopenic effect of low-dose IFN-␣. Indeed, the association of both cytokines resulted in increased circulating T-cell IntroductionCoinfection with HIV and hepatitis C virus (HCV) has become an increasingly common occurrence, with an estimated 25% to 30% of HIV ϩ patients also being HCV ϩ . 1 As a consequence, since the appearance of highly active antiretroviral therapy (HAART), chronic liver disease has become one of the most common causes of morbidity and mortality in HIV patients. 2,3 Although the effectiveness of standard HCV treatment, based on interferon-␣ (IFN-␣) injections, is known to decrease the longer a patient has been infected with the virus, HCV patients are not systematically put under treatment. Rather, initiation of treatment depends on the state of the patient's liver (fibrosis markers, serum aminotransferases, HCV RNA, hepatitis B virus status) and other parameters, which in turn are used to determine whether the potential benefits of therapy outweigh the risks of treatment-related toxicity. 4 For HIV-HCV-coinfected patients, some of these parameters are: the assessment of HIV disease status, such as current and past opportunistic infections, HIV-associated malignancies, CD4 count, HIV viral load, and details of HAART therapy, with CD4 count being one of the main criteria. Unfortunately, coinfected patients are poor responders to standard treatment as a sustained viral response occurs in only 27% to 40% of these patients, approximately half the rate seen in HCV-monoinfected patients. [5][6][7] The main reason for this difference can be attributed to exhaustion of the immune system. In addition, IFN-␣ treatment causes a leukopenia, including a decrease of lymphocyte numbers and thus of CD4 count, often leading to premature treatment interruption. [8][9][10][11][12] Therefore, to enhance the efficiency of anti-HVC therapy in coinfected patients, it is critically important to develop an alternative treatment that limits the lymphopenic effect of IFN-␣ therapy.Interleukin 7 (IL-7), a cytokine that promotes precursor B-and T-cell maturation [13][14][15] and supports peripheral T-cell homeostasis, [16][17][18...

We demonstrated that RTEs are effectively HIV infected. The similar infection rate observed in RTEs and other naive T cells, its relationship with plasma IL-7 levels, together with the lack of correlation between RTE infection and either thymic or peripheral proliferation, strongly suggests that RTE infection occurs either late during thymopoiesis or early on during their extrathymic maturation.

Interferon alpha (IFNα) therapy, despite good efficacy in curing HCV infection, leads to major side effects, in particular inducement of a strong peripheral T-cell lymphocytopenia. We here analyze the early consequences of IFNα therapy on both thymic function and peripheral T-cell homeostasis in patients in the acute or chronic phase of HCV-infection as well as in HIV/HCV co-infected patients. The evolution of T-cell subsets and T-cell homeostasis were estimated by flow cytometry while thymic function was measured through quantification of T-cell receptor excision circles (TREC) and estimation of intrathymic precursor T-cell proliferation during the first four months following the initiation of IFNα therapy. Beginning with the first month of therapy, a profound lymphocytopenia was observed for all T-cell subsets, including naïve T-cells and recent thymic emigrants (RTE), associated with inhibition of intrathymic precursor T-cell proliferation. Interleukin (IL)-7 plasma concentration rapidly dropped while lymphocytopenia progressed. This was neither a consequence of higher consumption of the cytokine nor due to its neutralization by soluble CD127. Decrease in IL-7 plasma concentration under IFNα therapy correlated with the decline in HCV viral load, thymic activity and RTE concentration in blood. These data demonstrate that IFNα-based therapy rapidly impacts on thymopoiesis and, consequently, perturbs T-cell homeostasis. Such a side effect might be detrimental for the continuation of IFNα therapy and may lead to an increased level of infectious risk, in particular in HIV/HCV co-infected patients. Altogether, this study suggests the therapeutic potential of IL-7 in the maintenance of peripheral T-cell homeostasis in IFNα-treated patients.

rhIL-7 treatment initially drives an expansion of HIV reservoir in PIR patients by D28. This expansion is probably not only because of infected cell proliferation, but also to possible enhanced neoinfection, despite highly active antiretroviral therapy. In contrast, subsequent reduction in HIV-DNA load per CD4 T-cell argues for partial elimination of infected cells between D28 and M3.

A metabolic thymic activity is detectable in c-ART naive and correlates with indirect phenotypic and molecular markers of thymic output. This activity may participate to the pool of peripheral naive CD4+ T cells and predicts the magnitude of T-cell reconstitution under treatment.