Daniel Scott-Algara

Cutting Edge: Increased NK Cell Activity in HIV-1-Exposed but Uninfected Vietnamese Intravascular Drug Users

We addressed the role of innate immunity in the protection against HIV-1 infection by studying NK cell function in 37 Vietnamese intravascular drug users (IDUs), who appeared to remain HIV-1 uninfected despite many years of high-risk exposure (exposed uninfected, EU), 10 IDUs who underwent seroconversion and 28 unexposed blood donors. Main results were: NK cell lytic activities against both the NK-susceptible K562 cell line and the NK-resistant Daudi cell line were significantly augmented in EU IDUs compared with either controls or seroconverters before or after seroconversion; NK cells producing the cytokines IFN-γ and TNF-α and the β chemokines CCL3, CCL4, and CCL5 were also increased in the EU IDUs, either after in vitro activation or without stimulation. The finding of an enhanced NK cell function in EU IDUs, especially compared with IDUs who became HIV-1 infected, supports the hypothesis that NK cells contribute to the protection against HIV-1 infection.

Preserved Central Memory and Activated Effector Memory CD4+ T-Cell Subsets in Human Immunodeficiency Virus Controllers: an ANRS EP36 Study

ABSTRACT Human immunodeficiency virus (HIV) controllers are rare individuals who spontaneously control HIV type 1 replication for 10 years or more in the absence of antiretroviral treatment. In the present study, HIV controllers (n = 11) maintained potent HIV-specific CD4 responses in spite of very low antigenic loads. Their CD4+ central memory T (TCM) cells were characterized by near-normal numbers and preserved interleukin-2 (IL-2) secretion in response to HIV antigens and uniformly high expression of the survival receptor IL-7 receptor α (IL-7Rα). Controllers expressed CCR7 at higher levels than uninfected controls, suggesting differences in TCM-cell homing patterns. CD4+ effector memory T (TEM)-cell responses were polyfunctional in HIV controllers, while IL-2 secretion was lost in viremic patients. Cytokine production was three times higher in controllers than in treated patients with undetectable viral loads, suggesting an intrinsically more efficient response in the former group. The total CD4+ TEM-cell pool underwent immune activation in controllers, as indicated by increased HLA-DR expression, decreased IL-7Rα expression, a bias towards gamma interferon production upon polyclonal stimulation, and increased macrophage inflammatory protein 1β secretion associated with chronic CCR5 down-regulation. Thus, HIV controllers showed a preserved CD4+ TCM-cell compartment and signs of potent functional activation in the CD4+ TEM-cell compartment. While controllers did not show the generalized immune activation pattern associated with disease progression, they had signs of immune activation restricted to the effector compartment. These findings suggest the induction of an efficient, nondetrimental type of immune activation in patients who spontaneously control HIV.

Induction or expansion of T-cell responses by a hepatitis B DNA vaccine administered to chronic HBV carriers

Despite the availability of effective hepatitis B vaccines for many years, over 370 million people remain persistently infected with hepatitis B virus (HBV). Viral persistence is thought to be related to poor HBV‐specific T‐cell responses. A phase I clinical trial was performed in chronic HBV carriers to investigate whether HBV DNA vaccination could restore T‐cell responsiveness. Ten patients with chronic active hepatitis B nonresponder to approved treatments for HBV infection were given 4 intramuscular injections of 1 mg of a DNA vaccine encoding HBV envelope proteins. HBV‐specific T‐cell responses were assessed by proliferation, ELISpot assays, and tetramer staining. Secondary end points included safety and the monitoring of HBV viraemia and serological markers. Proliferative responses to hepatitis B surface antigen were detected in two patients after DNA injections. Few HBV‐specific interferon γ–secreting T cells were detectable before immunization, but the frequency of such responses was significantly increased by 3 DNA injections. Immunization was well tolerated. Serum HBV DNA levels decreased in 5 patients after 3 vaccine injections, and complete clearance was observed in 1 patient. In conclusion, this study provides evidence that HBV DNA vaccination is safe and immunologically effective. We demonstrate that DNA vaccination can specifically but transiently activate T‐cell responses in some chronic HBV carriers who do not respond to current antiviral therapies. Supplementary material for this article can be found on the HEPATOLOGYwebsite (http://interscience.wiley.com/jpages/0270‐9139/suppmat/index.html). (HEPATOLOGY 2004;40:874–882.)

Implication of natural killer T cells in atherosclerosis development during a LPS-induced chronic inflammation

Atherosclerosis has many features of a chronic inflammatory disease. To evaluate the role of lipopolysaccharide (LPS), mimicking a systemic infection, we administered the endotoxin to apolipoprotein E (apoE)‐deficient mice. LPS injections increase the atherosclerotic lesion size and the titer of plasma autoantibodies directed against oxidized low‐density lipoprotein. We found that Th1 and Th2 T cells help the activation of B cells in the autoimmune response. The number of interleukin‐4 producing natural killer T cells is highly increased in peripheral blood, liver, spleen and thymus cells, as well as in the atherosclerotic plaque of the LPS‐treated mice. Finally, an important adventitial infiltrate of activated lymphocytes, sign of an advanced atherosclerosis, is observed only in the LPS‐treated mice. Our results demonstrate that LPS administration aggravates atherosclerosis in apoE‐deficient mice. LPS‐injected apoE‐deficient mice appear to be an excellent animal model to analyze the implementation of new therapeutic approaches in the treatment of atherosclerosis by manipulating immunological effectors.

Antiinflammatory and Antiatherogenic Effects of the NF-κB Inhibitor Acetyl-11-Keto-β-Boswellic Acid in LPS-Challenged ApoE−/− Mice

Objective—In this article, we studied the effect of acetyl-11-keto-β-boswellic acid (AKβBA), a natural inhibitor of the proinflammatory transcription factor NF-&kgr;B on the development of atherosclerotic lesions in apolipoprotein E–deficient (apoE−/−) mice. Methods and Results—Atherosclerotic lesions were induced by weekly LPS injection in apoE−/− mice. LPS alone increased atherosclerotic lesion size by ≈100%, and treatment with AKβBA significantly reduced it by ≈50%. Moreover, the activity of NF-&kgr;B was also reduced in the atherosclerotic plaques of LPS-injected apoE−/− mice treated with AKβBA. As a consequence, AKβBA treatment led to a significant downregulation of several NF-&kgr;B–dependent genes such as MCP-1, MCP-3, IL-1α, MIP-2, VEGF, and TF. By contrast, AKβBA did not affect the plasma concentrations of triglycerides, total cholesterol, antioxidized LDL antibodies, and various subsets of lymphocyte-derived cytokines. Moreover, AKβBA potently inhibited the I&kgr;B kinase (IKK) activity immunoprecipitated from LPS-stimulated mouse macrophages and mononuclear cells leading to decreased phosphorylation of I&kgr;Bα and inhibition of p65/NF-&kgr;B activation. Comparable AKβBA-mediated inhibition was also observed in LPS-stimulated human macrophages. Conclusion—The inhibition of NF-&kgr;B activity by plant resins from species of the Boswellia family might represent an alternative for classical medicine treatments for chronic inflammatory diseases such as atherosclerosis. (Arterioscler Thromb Vasc Biol. 2008;28:272-277)

Reduced CD4 T cell activation and in vitro susceptibility to HIV-1 infection in exposed uninfected Central Africans

BackgroundEnvironmentally driven immune activation was suggested to contribute to high rates of HIV-1 infection in Africa. We report here a study of immune activation markers and susceptibility to HIV-1 infection in vitro of forty-five highly exposed uninfected partners (EUs) of HIV-1 infected individuals in Central African Republic, in comparison with forty-four low-risk blood donors (UCs).ResultsAnalysis of T lymphocyte subsets and activation markers in whole blood showed that the absolute values and the percentage of HLA-DR+CD4 T cells and of CCR5+CD4 T cells were lower in the EUs than in the UCs (p = 0.0001). Mutations in the CCR5 coding region were not found in either group. Susceptibility to in vitro infection of unstimulated peripheral blood mononuclear cells, prior of PHA activation, was decreased in EUs compared to UCs, either using a CXCR4-tropic or a CCR5-tropic HIV-1 strain (p = 0.02 and p = 0.05, respectively). Levels of MIP-1β, but not of MIP-1α or RANTES, in the supernatants of PHA-activated PBMC, were higher in the EUs than in the UCs (p = 0.007).ConclusionWe found low levels of CD4 T cell activation and reduced PBMC susceptibility to HIV-1 infection in Central African EUs, indicating that both may contribute to the resistance to HIV-1 infection.

Human Apolipoprotein A-IV Reduces Secretion of Proinflammatory Cytokines and Atherosclerotic Effects of a Chronic Infection Mimicked by Lipopolysaccharide

Objective—Expression of human apolipoprotein (h-apo) A-IV in apoE-deficient (apoE0) mice (h-apoA-IV/E0) reduces susceptibility to atherosclerosis. Chronic infection mimicked by exposure to lipopolysaccharide (LPS) increases the size of atherosclerosis lesions in apoE0 mice. Thus, we used h-apoA-IV/E0 mice to determine whether h-apoA-IV plays a protective role after LPS administration. Methods and Results—We injected apoE0, h-apoA-IV/E0, and C57Bl/6 (wild-type) mice intraperitoneally with either LPS or phosphate-buffered saline (PBS) every week for 10 weeks. Atherosclerotic lesions were significantly smaller in h-apoA-IV/E0 mice treated with LPS than in their apoE0 counterparts. The titers of IgG2a and IgG2b autoantibodies to oxidized low-density lipoprotein (LDL) were higher in the LPS-group of h-apoA-IV/E0 mice than in apoE0 mice, suggesting that the Th1 response is stronger in the presence of h-apoA-IV. Lymphocytes from the blood, liver, spleen, and thymus of h-apoA-IV/E0 mice treated with LPS produced less IL-4, INF-&ggr;, and TNF-&agr; proinflammatory cytokines than their apoE0 counterparts. Furthermore, we demonstrated that recombinant h-apoA-IV blocks the LPS-induced stimulation of monocytes. Conclusions—The expression of h-apoA-IV in apoE0 mice reduces the susceptibility to atherogenesis and decreases the secretion of proinflammatory cytokines after LPS administration.

The Th17/Treg Ratio, IL-1RA and sCD14 Levels in Primary HIV Infection Predict the T-cell Activation Set Point in the Absence of Systemic Microbial Translocation

Impairment of the intestinal barrier and subsequent microbial translocation (MT) may be involved in chronic immune activation, which plays a central role in HIV pathogenesis. Th17 cells are critical to prevent MT. The aim of the study was to investigate, in patients with primary HIV infection (PHI), the early relationship between the Th17/Treg ratio, monocyte activation and MT and their impact on the T-cell activation set point, which is known to predict disease progression. 27 patients with early PHI were included in a prospective longitudinal study and followed-up for 6 months. At baseline, the Th17/Treg ratio strongly negatively correlated with the proportion of activated CD8 T cells expressing CD38/HLA-DR or Ki-67. Also, the Th17/Treg ratio was negatively related to viral load and plasma levels of sCD14 and IL-1RA, two markers of monocyte activation. In untreated patients, the Th17/Treg ratio at baseline negatively correlated with CD8 T-cell activation at month 6 defining the T-cell activation set point (% HLA-DR+CD38+ and %Ki-67+). Soluble CD14 and IL-1RA plasma levels also predicted the T-cell activation set point. Levels of I-FABP, a marker of mucosal damages, were similar to healthy controls at baseline but increased at month 6. No decrease in anti-endotoxin core antibody (EndoCAb) and no peptidoglycan were detected during PHI. In addition, 16S rDNA was only detected at low levels in 2 out 27 patients at baseline and in one additional patient at M6. Altogether, data support the hypothesis that T-cell and monocyte activation in PHI are not primarily driven by systemic MT but rather by viral replication. Moreover, the “innate immune set point” defined by the early levels of sCD14 and IL-1RA might be powerful early surrogate markers for disease progression and should be considered for use in clinical practice.

The Shigella flexneri Type Three Secretion System Effector IpgD Inhibits T Cell Migration by Manipulating Host Phosphoinositide Metabolism

Shigella, the Gram-negative enteroinvasive bacterium that causes shigellosis, relies on its type III secretion system (TTSS) and injected effectors to modulate host cell functions. However, consequences of the interaction between Shigella and lymphocytes have not been investigated. We show that Shigella invades activated human CD4(+) T lymphocytes. Invasion requires a functional TTSS and results in inhibition of chemokine-induced T cell migration, an effect mediated by the TTSS effector IpgD, a phosphoinositide 4-phosphatase. Remarkably, IpgD injection into bystander T cells can occur in the absence of cell invasion. Upon IpgD-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)), the pool of PIP(2) at the plasma membrane is reduced, leading to dephosphorylation of the ERM proteins and their inability to relocalize at one T cell pole upon chemokine stimulus, likely affecting the formation of the polarized edge required for cell migration. These results reveal a bacterial TTSS effector-mediated strategy to impair T cell function.

Anti-HBV DNA vaccination does not prevent relapse after discontinuation of analogues in the treatment of chronic hepatitis B: a randomised trial—ANRS HB02 VAC-ADN

Objective The antiviral efficacy of nucleos(t)ide analogues whose main limitation is relapse after discontinuation requires long-term therapy. To overcome the risk of relapse and virological breakthrough during long-term therapy, we performed a phase I/II, open, prospective, multicentre trial using a HBV envelope-expressing DNA vaccine. Design 70 patients treated effectively with nucleos(t)ide analogues for a median of 3 years (HBV DNA <12 IU/mL for at least 12 months) were randomised into two groups: one received five intramuscular injections of vaccine (weeks 0, 8, 16, 40 and 44) and one did not receive the vaccine. Analogues were stopped after an additional 48 weeks of treatment in patients who maintained HBV DNA <12 IU/mL with no clinical progression and monthly HBV DNA for 6 months. The primary endpoint was defined as viral reactivation at week 72 (HBV DNA >120 IU/mL) or impossibility of stopping treatment at week 48. Results Reactivation occurred in 97% of each group after a median 28 days without liver failure but with an HBV DNA <2000 IU/mL in 33%; 99% of adverse reactions were mild to moderate. Immune responses were evaluated by enzyme-linked immunosorbent spot and proliferation assays: there was no difference in the percentage of patients with interferon-γ secreting cells and a specific T-cell proliferation to HBcAg but not to HBsAg after reactivation in each group. Conclusions Although it is fairly well tolerated, the HBV DNA vaccine does not decrease the risk of relapse in HBV-treated patients or the rate of virological breakthrough, and does not restore the anti-HBV immune response despite effective viral suppression by analogues. Trial registration number NCT00536627.