Behavior of soluble HLA class I antigens in patients with chronic hepatitis C during interferon therapy: An early predictor marker of response?

Soluble HLA class I antigens (sHLA-I), ₂-microglobulin ( ₂-.) and alanine aminotransferase (ALT) serum levels have been evaluated in 16 patients affected by chronic hepatitis C treated for six months with recombinant interferon- (rIFN-, 3 MU three times a week). The predictor role of sHLA-I and ALT modifications with respect to the response to rIFN- therapy was also evaluated. Six patients responded (group 1), five patients relapsed following an initial response (group 2), and five did not respond to rIFN- treatment (group 3). The baseline serum levels of sHLA-I and ₂- were significantly higher in all three groups of HCV-positive patients with respect to HCV-negative controls (P<0.05). A significant increase of sHLA-I serum level with respect to baseline value (P<0.001) was observed in group 1 patients after two weeks of rIFN- treatment. sHLA-I serum level then decreased, although remaining steadily and significantly increased with respect to baseline (P values ranging from 0.05 to 0.01) in the following five months and then returned to baseline one month after the end of rIFN- administration. No significant variations of ₂- serum levels were detected throughout the observation period. In group 1 patients ALT serum levels significantly decreased after two weeks of rIFN- treatment (P<0.001) and then remained in the normal range throughout the observation period. In the other two groups of patients no relevant variations of sHLA-I and ₂- serum levels were found during and after rIFN- therapy. The modifications of sHLA-I serum levels discriminate, as a single marker, group 1 patients from group 2 and 3 patients after two weeks of rIFN- treatment (P<0.003). The association of sHLA-I and ALT modifications improves the discriminant power and leads to a complete differentiation of the three groups of patients after four weeks of rIFN- treatment (P<0.0001). If confirmed in a larger series of patients, these results will provide a useful marker to predict which patients affected by chronic hepatitis C will respond to treatment and will help to avoid their ineffective treatment with an expensive and potentially harmful drug.     

Soluble HLA class I antigens in chronic hepatitis C: a disease-associated manifestation or molecules modulating immunoresponsiveness?

The occurrence of high levels of soluble human leukocyte class I antigens (sHLA-I) represents an usual finding during the course of different clinical conditions, such as viral infections and autoimmune disorders. On the other hand, the well known property of sHLA-I to modulate T cell responsiveness could be taken as an advantage to improve long-term allograft acceptance. Recent data have pointed out that subjects with chronic hepatitis C virus (HCV) infection exhibit high amounts of sHLA-I, a pattern which has also been used for monitoring host responsiveness to interferon alpha (IFN-alpha) therapy. However, the lack of correlation between lymphocyte infiltration at liver site and disease biological activity suggests a potential role for sHLA-I in T cell dysfunction during chronic hepatitis C. sHLA-I antigens may, in fact, either interact with T cell receptor delivering an inhibitory signal or trigger cytotoxic T lymphocyte apoptosis by inducing CD95 ligand expression. Both events seem to favour HCV replication and liver tissue damage progression. Alltogether, these findings indicate that, besides viral variant generation and HCV core-mediated immunosuppression, sHLA-I may contribute to the imbalance of immunoresponsiveness during chronic HCV infection.     

Parenchymal microglia of naïve adult C57BL/6J mice express high levels of B7.1, B7.2, and MHC class II

In this study, we addressed B7.1, B7.2, and MHC class II expression on microglia of normal adult C57BL/6J mice, which are susceptible to MOG35-55 peptide-induced experimental autoimmune encephalomyelitis (EAE). We showed that there are two distinct major populations of CD11b(+) cells in the central nervous system (CNS) of na?ve mice: CD45 low (CD45(lo); parenchymal microglia) and CD45 intermediate (CD45(int); CNS-associated macrophages). These two populations compose CNS microglia. There is a rare CD45 high (CD45(hi)) population. By contrast, splenic CD11b(+) cells (macrophages) are CD45(int) and CD45(hi), but rarely CD45(lo). CD45(lo)CD11b(+) cells constitutively express much higher levels of B7.1, B7.2, and MHC class II compared to CD45(int) CD11b(+) cells. A shift of CD11b(+) cells from CD45(lo) to CD45(int) was observed in the CNS of EAE mice. Our study provides evidence that (1) CD45(lo) and CD45(hi), but not CD45(int), could be unique markers to differentiate parenchymal microglia from infiltrating macrophages in EAE; (2) the level of CD45 expression on parenchymal microglia (CD45(lo)) was upregulated in EAE; and (3) parenchymal microglia in normal CNS could be potent APCs by expressing high levels of B7.1, B7.2, and MHC class II molecules and could therefore play an important role in inflammation and autoimmunity in the CNS.     

Association of HLA class I antigens with Behçet disease in South Tunisia

Purpose

To study antigen HLA class I association with different clinical forms of Behçet's disease in South Tunisian population.

Patients and methods

We retrospectively reviewed 129 clinical case patients. All of the patients fulfilled the criteria of the international study group for Behçet's disease, and were followed at the department of internal medicine of the university hospital of Sfax. HLA class I phenotyping was performed by microlymphocytotoxicity complement dependent for our 129 patients and for 123 healthy controls. We used the program SPSS 11.0 to analyse clinical data and to compare HLA class I antigen distribution between these two populations.

Results

The study group concerned a total of 129 patients (81 males and 48 females). The mean age at disease onset was of 32 years. HLA-B51 antigen was the only antigen significantly more frequent among patients (24.81%) than controls (9.76%, p = 0.002). HLA-B44 was significantly more frequent among patients having familial history of recurrent buccal aphthosis or Behçet disease. HLA-A11 antigen was associated with early disease onset, and HLA-A1 was negatively associated with severe form of the disease (neurological, vascular or ocular manifestations).

Conclusion

Our study confirmed the HLA-B51 association with Behçet disease. Nevertheless, B51 frequency in South Tunisian patients was lower than that found in other studies regardless of the clinical manifestation.     

Serum HLA class I antigens: markers and modulators of an immune response?

HLA class I antigens circulate in the serum in soluble form. This article discusses the clinical significance of levels of serum HLA class I antigens, both in patients with viral diseases and following organ transplantation, as well as the potential involvement of such antigens in the immune response.     

γδT-cell function in sepsis is modulated by C5a receptor signalling

We previously showed that γδT cells are involved in the pathogenesis of sepsis, but, the underlying mechanisms remained unclear. The present study demonstrates, for the first time, that γδT cells express the complement C5a receptor (C5aR, CD88) and that CD88 expression in γδT cells was up-regulated in mice following sepsis both at protein and mRNA levels. Complement C5a itself contributed to the regulation of C5aR expression on γδT cells, as (i) neutralization of C5a in vivo prevented the expression of C5aR on γδT cells in septic mice and (ii) incubation of mouse spleen cells or purified γδT cells with recombinant C5a in vitro increased CD88 expression by γδT cells at both protein and mRNA levels. C5a receptor on γδT cells also mediates increased interleukin-17 (IL-17) expression as incubation of mouse spleen cells or purified γδT cells with recombinant C5a promotes the IL-17 expression by γδT cells. Ligation of the C5aR on γδT cells activated the phosphoinositide 3-kinase (PI3K)/Akt signalling pathway, which enhances CD88 expression and promotes IL-17 secretion. These results demonstrate that C5a acts directly on the C5aR expressed on γδT cells, resulting in cell activation, and subsequently enhances their capacity for IL-17 production. The up-regulation of the PI3K/Akt pathway following C5a stimulation contributes to up-regulation of γδT-cell function.     

Proteolytic cleavage of MHC class I by complement C1-esterases—an overlooked mechanism?

The complement Cl-esterases have been shown to cleave the MHC class I molecules, which are important participants in the activation of T lymphocytes, between the α₂- and the α₃-domain of the heavy chain. The possible involvement of the Cl-esterases in the regulation of peripheral self-tolerance is discussed. It is hypothesized that the C1-esterase-mediated cleavage of the MHC class I molecules either induces: a soluble fragment of the outer two domains of the MHC class I molecule, in association with β₂-microglobulin, to bind to the T cell receptors and prevent the cells from being activated, or produces a change in the exposure of the α₃-domain that remain on the cell surface, acting as mediator of a ‘veto signal’ that prevents these cells from being activated.     

N2pc is modulated by stimulus–stimulus,but not by stimulus–response incompatibilities

Studies of the N2pc in Simon-type tasks have revealed inconsistent results. That is, N2pc was only modulated when a stimulus–stimulus (S-S) overlap covaries with the stimulus–response (S-R) overlap. The present study aimed to establish whether N2pc is modulated by the S-R or by the S-S overlap. Therefore, we designed a Simon task requiring response to a colour stimulus (an arrow) with two irrelevant dimensions (position and direction). The following conditions were thus generated: compatible direction–compatible position (CDCP); incompatible direction–compatible position (IDCP); compatible direction–incompatible position (CDIP); and incompatible direction–incompatible position (IDIP). In IDCP and CDIP, both irrelevant dimensions conveyed contradictory spatial information (S-S incompatibility), while compatibility between both irrelevant dimensions occurred in CDCP and IDIP (the direction indicated was compatible with stimulus position). The N2pc amplitude was smaller in IDCP and CDIP than in CDCP and IDIP, what suggests that N2pc was modulated by S-S incompatibility and not by S-R incompatibilities.     

MDA5 is SUMOylated by PIAS2β in the upregulation of type I interferon signaling

Retinoic acid-inducible protein I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are cytosolic viral RNA sensors that induce type I interferon production (IFN). In this study, we found that MDA5 undergoes inducible SUMOylation by small ubiquitin-like modifier-1 (SUMO-1) in response to polyI:C stimulation. Enhanced SUMOylation of MDA5 by exogenously expressed SUMO-conjugating enzyme Ubc9 correlated with upregulation of IFN expression and repressed virus replication. Conversely, overexpression of a SUMOylation-deficient mutant of Ubc9 or knockdown of endogenous Ubc9 reduced IFN production. Furthermore, we showed that PIAS2β, a SUMOylation E3 ligase, could specifically interact with and enhance the SUMOylation of MDA5. Consequently, PIAS2β knockdown reduced the SUMOylation of MDA5 and the IFN production. Collectively, these findings suggest that SUMO-1 modification of MDA5 possibly via PIAS2β may play a role in the MDA5-mediated IFN response to viral infections.     

Inhibition of lung colonization of mouse colon 26 adenocarcinoma by recombinant mouse interferon β through a modification of platelet function

Recombinant murine interferon (MuIFN-) given i.v. efficiently inhibited both pulmonary arrest and formation of lung colonies of NL-17, a highly metastatic variant of mouse colon adenocarcinoma 26. NL-17 was rather resistant to MuIFN- in vitro and was highly resistant to natural killer cells of mice even though they were treated in vivo with MuIFN-. Platelets isolated from MuIFN--treated mice showed reduced aggregating activity induced by NL-17. Since lung colonization by NL-17 is influenced by platelet aggregation, the inhibition of colonization by MuIFN- could be partly mediated through modification of platelet function in vivo. The effect of MuIFN- on platelet function and its subsequent inhibition of lung colony formation give new insights into the action of recombinant MuIFN-.     

Regulation of Phospholipase C-γ2 and Phosphoinositide 3-Kinase Pathways by Adaptor Proteins In B Lymphocytes

The importance of phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC)-γ2 in B cell function and development has been highlighted by gene targeting experiments in mice. In fact, these knockout mice exhibit a profound inhibition of proliferative responses upon B cell receptor (BCR) engagement. The molecular connections between these effectors and upstream tyrosine kinases such as Syk have been studied intensively in the past few years. This mechanism involves the action of cytoplasmic adaptor molecules, which participate in forming multicomponent signaling complexes, thereby directing the appropriate subcellular localization of effector enzymes. In addition to these cytoplasmic adaptor proteins, cell surface coreceptors can be viewed as transmembrane adaptor proteins, because coreceptors can also change the localization of effector enzymes, which in turn modulates the BCR-initiated signals.     

Enterotoxigenic Escherichia coli Prevents Host NF-κB Activation by Targeting IκBα Polyubiquitination

The NF-κB pathway regulates innate immune responses to infection. NF-κB is activated after pathogen-associated molecular patterns are detected, leading to the induction of proinflammatory host responses. As a countermeasure, bacterial pathogens have evolved mechanisms to subvert NF-κB signaling. Enterotoxigenic Escherichia coli (ETEC) causes diarrheal disease and significant morbidity and mortality for humans in developing nations. The extent to which this important pathogen subverts innate immune responses by directly targeting the NF-κB pathway is an understudied topic. Here we report that ETEC secretes a heat-stable, proteinaceous factor that blocks NF-κB signaling normally induced by tumor necrosis factor (TNF), interleukin-1β, and flagellin. Pretreating intestinal epithelial cells with ETEC supernatant significantly blocked the degradation of the NF-κB inhibitor IκBα without affecting IκBα phosphorylation. Data from immunoprecipitation experiments suggest that the ETEC factor functions by preventing IκBα polyubiquitination. Inhibiting clathrin function blocked the activity of the secreted ETEC factor, suggesting that this yet-uncharacterized activity may utilize clathrin-dependent endocytosis to enter host cells. These data suggest that ETEC evades the host innate immune response by directly modulating NF-κB signaling.     

Icaritin inhibits PD-L1 expression by Targeting Protein IκB Kinase α

Icaritin, a small molecule currently being investigated in phase III clinical trials in China (NCT03236636 and NCT03236649) for treatment of advanced hepatocellular carcinoma (HCC), is a prenylflavonoid derivative obtained from the Epimedium genus. Previously, it was found that Icaritin decreased the expression of PD-L1, but its direct molecular targets and the underlying mechanisms have not been identified. In this study, we report the identification of IKK-α as the protein target of Icaritin by biotin-based affinity binding assay. The further mutagenesis assay has provided evidence that C46 and C178 in IKK-α were essential amino acids for Icaritin binding to IKK-α, revealing the binding sites of Icaritin to IKK-α for the first time. Functionally, Icaritin inhibited the NF-κB signalling pathway by blocking IKK complex formation, which led to decreased nuclear translocation of NF-κB p65, and subsequent downregulation of PD-L1 expression in a dose–dependent manner. More importantly, PD-L1-positive patients exhibited longer overall survival upon Icaritin therapy. Finally, Icaritin in combination with checkpoints antibodies, such as α-PD-1, has demonstrated much better efficacy than any single therapy in animal models. This is the first report that anticancer effects of Icaritin are mediated, at least in part, by impairing functions of IKK-α.     

Incubation of whole blood at 39°C augments gamma interferon (IFN-γ)-induced protein 10 and IFN-γ responses to Mycobacterium tuberculosis antigens

A rarely challenged dogma in cell-mediated immune (CMI) assays is the incubation temperature, 37°C. Fever augments proinflammatory immune responses in vivo, and the aim of this study was to explore whether incubation at fever-range temperature could increase antigen-specific biomarker responses. We compared CMI responses following incubation of whole blood at 37°C and 39°C. Whole blood was obtained from (i) 34 healthy subjects whose blood was incubated with TB10.4 antigen, present in the Mycobacterium bovis bacillus Calmette-Guérin vaccine and many environmental mycobacteria; (ii) 8 TB patients and 8 controls incubated with Mycobacterium tuberculosis-specific antigens in the QuantiFERON-TB Gold test (QFT-IT); and (iii) from both groups incubated with a T cell mitogen. T cell responses (gamma interferon [IFN-γ]) and responses from antigen-presenting cells (IFN-γ-induced protein 10 [IP-10]) were determined. We further evaluated the effect of adding interleukin-7 (IL-7) and blocking IL-10 during incubation. In TB patients, IFN-γ and IP-10 levels were increased 4.1- and 3.4-fold, respectively, at 39°C incubation (P < 0.001). Similar results were seen after mitogen stimulation. In subjects responding to TB10.4, the effects were less pronounced and significant only for IP-10. Incubation at 39°C increased IP-10 and IFN-γ responsiveness to both antigens and mitogen in persons with baseline or initial low responses. Adding IL-7 and blocking IL-10 augmented the effects in synergy with fever-range temperature. Incubation at fever-range temperature vividly increases CMI responsiveness to antigen stimulation in vitro in tuberculosis patients and may increase the sensitivity of CMI assays.