Gerrit Ahrenstorf

Negative Checkpoint Regulatory Molecule 2B4 (CD244) Upregulation Is Associated with Invariant Natural Killer T Cell Alterations and Human Immunodeficiency Virus Disease Progression

The CD1d-restricted invariant natural killer T (iNKT) cells are implicated in innate immune responses against human immunodeficiency virus (HIV). However, the determinants of cellular dysfunction across the iNKT cells subsets are seldom defined in HIV disease. Herein, we provide evidence for the involvement of the negative checkpoint regulator (NCR) 2B4 in iNKT cell alteration in a well-defined cohort of HIV-seropositive anti-retroviral therapy (ART) naïve, ART-treated, and elite controllers (ECs). We report on exaggerated 2B4 expression on iNKT cells of HIV-infected treatment-naïve individuals. In sharp contrast to CD4−iNKT cells, 2B4 expression was significantly higher on CD4+ iNKT cell subset. Notably, an increased level of 2B4 on iNKT cells was strongly correlated with parameters associated with HIV disease progression. Further, iNKT cells from ART-naïve individuals were defective in their ability to produce intracellular IFN-γ. Together, our results suggest that the levels of 2B4 expression and the downstream co-inhibitory signaling events may contribute to impaired iNKT cell responses.

Absence of chronic hepatitis E in a German cohort of common variable immunodeficiency patients

Cases of chronic or prolonged hepatitis E virus (HEV) infections have been described in solid organ transplant recipients, HIV infected patients and in patients with malignancies or idiopathic CD4+ T lymphopenia. It is unknown if HEV infection also takes chronic courses in patients with common variable immunodeficiency (CVID). We studied a cohort of 73 CVID patients recruited in a low endemic Central European country. None of the subjects tested positive for HEV RNA or anti-HEV IgG. Immunoglobulin transfusions (n=10) tested negative for HEV RNA but all were anti-HEV positive. To verify that such pooled blood products contain anti-HEV protective antibodies we measured the anti-HEV IgG optical density (OD) values in patients before and after transfusion. Anti-HEV OD values increased after infusion but did not reach the cut-off considered as positive. Thus, chronic HEV infections seem to be rare events in CVID patients in Germany. Commercially available immunoglobulin infusions contain anti HEV antibodies and may contribute to protection from HEV infection.

Norovirus outbreaks in german refugee camps in 2015

Purpose Refugees often live in confined housing conditions with shared kitchen and sanitary facilities, rendering susceptible to communicable diseases. We here describe the outbreak, spread and self-limiting nature of a norovirus outbreak in a German refugee camp in the winter of 2015. Methods During a norovirus outbreak, data on clinical symptoms, nationality and living conditions was obtained in a refugee camp in northern Germany in the winter of 2015. Furthermore secondary data on norovirus outbreaks in 2015 was assessed. Results Amongst n = 982 refugees, n = 36 patients (3.7 %) presented with acute norovirus gastroenteritis. The vast majority of cases were children, only the first patient was admitted to the hospital. Intensified hygiene measures were implemented on day 2 of the outbreak, but new cases peaked on day 21 and occurred until one month after the first case. Different cultural backgrounds, eating habits and hygiene standards amongst the refugees made it particularly challenging to implement stringent isolation and hygiene measures. Despite these predisposing factors, only minor norovirus outbreaks were reported in refugee camps in 2015. Conclusion Adults refugees had a low attack rate of symptomatic norovirus infection, while small children are at high risk. Infection spreads despite hygiene measures and camp sites and staff should be prepared for the particular challenges of such situations with a particular focus on cultural-background specific implementation of hygiene measures.

TLR8 regulation of LILRA3 in monocytes is abrogated in human immunodeficiency virus infection and correlates to CD4 counts and virus loads

BackgroundLILRA3 is an immunostimulatory molecule which can conditionally induce the proliferation of cytotoxic cells. LILRA3 has a deletion genotype which is associated with multiple immune disorders. In this study, we wanted to analyze the regulation of LILRA3 and its significance in the context of HIV infection.ResultsWe analyzed a panel of TLR agonists and found that ssRNA40, a TLR8 agonist, is a potent inducer of LILRA3 in healthy individuals. However, this regulation is much diminished in HIV. Comparison of TLR8 to TLR4 induction of LILRA3 indicated that LPS induces less LILRA3 than ssRNA40 among healthy controls, but not HIV patients. Levels of LILRA3 induction correlated to virus load and CD4 counts in untreated patients. Recombinant LILRA3 can induce a host of proinflammatory genes which include IL-6 and IL-1α, as well as alter the expression of MHC and costimulatory molecules in monocytes and B-cells.ConclusionOur experiments point towards a beneficial role for LILRA3 in virus infections, especially in ssRNA viruses, like HIV, that engage TLR8. However, the potentially beneficial role of LILRA3 is abrogated during a HIV infection. We believe that more work has to be done to study the role of LILRA3 in infectious diseases and that there is a potential for exploring the use of LILRA3 in the treatment of virus infections.

IL-1β limits the extent of human 6-sulfo LacNAc dendritic cell (slanDC)-mediated NK cell activation and regulates CD95-induced apoptosis.

To function optimally, human blood natural killer (NK) cells need to communicate with other immune cells. Previously, it has been shown that NK cells communicate with 6-sulfo LacNAc dendritic cells (slanDCs), which are able to stimulate NK cells in vitro. In this study, we investigated how slanDCs regulate the level of NK cell activation. The secretion of interleukin (IL)-1β by slanDCs during coculture with NK cells increased as a result of signaling via intercellular adhesion molecule-1 on slanDCs following its interaction with lymphocyte function-associated antigen-1 on NK cells. IL-1β induced the expression of Fas receptor (CD95) on NK cells. The binding of Fas ligand (CD178) to CD95 induced the apoptosis of activated NK cells. Moreover, IL-1β also induced increased cyclooxygenase-2 expression in slanDCs, which in turn enabled the cells to secrete prostaglandin (PG)-E2. Consequently, PGE2 acted as a suppressing agent, tuning down the activation level of NK cells. In summary, IL-1β limits the level of NK cell activation by inducing apoptosis and suppression as a homeostatic regulatory function.

Evidence of inflammasome activation and formation of monocyte-derived apoptosis-associated speck-like protein containing a caspase-recruitment domain specks in HIV-1 positive patients

Objective: The formation of large intracellular protein aggregates of the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a caspase-recruitment domain; also know as PYCARD) is a hallmark of inflammasome activation. ASC speck-forming cells release the highly proinflammatory cytokine IL-1&bgr; in addition to ASC specks into the extracellular space during pyroptotic cell death. There ASC specks can propagate inflammation to other nonactivated cells or tissues. HIV-1 retroviral infection triggers inflammasome activation of abortively infected CD4+ T cells in secondary lymphatic tissues. However, if pyroptosis occurs in other peripheral blood mononuclear cells (PBMCs) of HIV-1-infected patients is currently unknown. We investigated if ASC speck positive cells are present in the circulation of HIV-1-infected patients. Design and methods: PBMCs or plasma of HIV-1 infected, antiretroviral therapy-naive patients were analyzed for the presence of ASC speck+ cells or extracellular ASC and compared with healthy controls. Intracellular staining for ASC was employed to detect ASC speck+ cells within PBMCs by flow cytometry, and ELISA to detect free ASC in the plasma. ASC multimerization was confirmed by immunoblot. Results: Peripheral blood CD14++CD16− monocytes were ASC speck+ in HIV patients, but not in healthy controls. In the subgroup analysis, HIV patients with lower CD4+ T-cell counts and higher viral load had significantly more ASC speck+ monocytes. ASC speck formation did not correlate with Gag expression, coinfection, lactate dehydrogenase or C-reactive protein. Conclusion: Our findings suggest that pyroptotic CD14++CD16− classical monocytes of HIV-1-infected patients release ASC specks into the blood stream, a phenomenon that may contribute to HIV-1 induced inflammation and immune activation.

LILRA3 deletion is a genetic risk factor of HIV infection

Objective: The aim of this study is to analyse the influence of LILRA3 and the genetic leukocyte immunoglobulin-like receptor 3 (LILRA3) deletion on transmission and clinical course of HIV infection. Design: Case and control study. Methods: LILRA3 genotypes were determined by PCR. HIV patients were categorized into short-term progressors, normal progressors and long-term nonprogressors according to the clinical course. Functional studies were performed using real-time PCR, intracellular flow cytometry and ELISA. Results: The prevalence of the homozygous LILRA3 deletion was higher in HIV-positive individuals (n = 439) than in controls (n = 651) (P = 0.02). The disease progression was faster in homozygously deleted patients with more short-term progressors than in heterozygous (P = 0.03) and homozygously positive (P = 0.002) individuals. These results have been confirmed in a seroconverter cohort (n = 288). The frequency of the homozygous deletion in the confirmation cohort was higher than in controls (P = 0.04). Combining both cohorts, the proportion of homozygously LILRA3-deleted individuals was 6.2% in HIV-infected patients (n = 727) vs. 3.2% in controls (P = 0.01). Functional analysis revealed an upregulation of the LILRA3 gene in real-time PCR in treated patients when compared with untreated patients (P = 0.007) and controls (P = 0.02) resulting in a higher LILRA3 expression in CD4+ (P = 0.008) and CD14+ (P = 0.02) cells of untreated patients in intracellular flow cytometry. LILRA 3 concentrations in the sera were similar between the groups, in untreated patients a correlation between viral load and LILRA3 concentration was found. Conclusion: The homozygous LILRA3 deletion is associated with a higher susceptibility for HIV disease and with a faster disease progression.

Brief Report: HIV-1 Infection Results in Increased Frequency of Active and Inflammatory SlanDCs that Produce High Level of IL-1β.

Abstract:HIV infection is marked by phenotypic and functional alterations of immune cells. Different studies have shown both numerical and functional deterioration of dendritic cells in HIV-1–infected patients. In this study, we report an increase of inflammatory 6-sulfo LacNAc dendritic cells (slanDCs) that are more activated and produce higher amounts of interleukin (IL)-1&bgr; during HIV-1 infection as compared with healthy controls. IL-1&bgr; plays a regulatory role in chronic inflammatory disorders. Therefore, our findings might reveal a compensatory regulatory function of slanDCs during HIV-1 infection.