Natural truncation of the chemokine MIP-1 beta /CCL4 affects receptor specificity but not anti-HIV-1 activity

Assessment of Human SARS CoV-2-Specific T-Cell Responses Elicited In Vitro by New Computationally Designed mRNA Immunogens (COVARNA)

The COVID-19 pandemic has brought significant changes and advances in the field of vaccination, including the implementation and widespread use of encapsidated mRNA vaccines in general healthcare practice. Here, we present two new mRNAs expressing antigenic parts of the SARS-CoV-2 spike protein and provide data supporting their functionality. The first mRNA, called RBD-mRNA, encodes a trimeric form of the virus spike protein receptor binding domain (RBD). The other mRNA, termed T-mRNA, codes for the relevant HLA I and II spike epitopes. The two mRNAs (COVARNA mRNAs) were designed to be used for delivery to cells in combination, with the RBD-mRNA being the primary source of antigen and the T-mRNA working as an enhancer of immunogenicity by supporting CD4 and CD8 T-cell activation. This innovative approach substantially differs from other available mRNA vaccines, which are largely directed to antibody production by the entire spike protein. In this study, we first show that both mRNAs are functionally transfected into human antigen-presenting cells (APCs). We obtained peripheral blood mononuclear cell (PBMC) samples from three groups of voluntary donors differing in their immunity against SARS-CoV-2: non-infected (naïve), infected-recovered (convalescent), and vaccinated. Using an established method of co-culturing autologous human dendritic cells (hDCs) with T-cells, we detected proliferation and cytokine secretion, thus demonstrating the ability of the COVARNA mRNAs to activate T-cells in an antigen-specific way. Interestingly, important differences in the intensity of the response between the infected-recovered (convalescent) and vaccinated donors were observed, with the levels of T-cell proliferation and cytokine secretion (IFNγ, IL-2R, and IL-13) being higher in the vaccinated group. In summary, our data support the further study of these mRNAs as a combined approach for future use as a vaccine.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

A Novel Resolution of Diabetes: C-C Chemokine Motif Ligand 4 Is a Common Target in Different Types of Diabetes by Protecting Pancreatic Islet Cell and Modulating Inflammation

Systemic inflammation is related to hyperglycemia in diabetes mellitus (DM). C-C chemokine motif ligand (CCL) 4 is upregulated in type 1 & type 2 DM patients. This study aimed to investigate if CCL4 could be a potential target to improve blood sugar control in different experimental DM models. Streptozotocin-induced diabetic mice, Leprdb /JNarl diabetic mice, and C57BL/6 mice fed a high fat diet were used as the type 1 DM, type 2 DM, and metabolic syndrome model individually. Mice were randomly assigned to receive an anti-CCL4 neutralizing monoclonal antibody. The pancreatic β-cells were treated with streptozotocin for in vitro experiments. In streptozotocin-induced diabetic mice, inhibition of CCL4 controlled blood sugar, increased serum insulin levels, increased islet cell proliferation and decreased pancreatic interleukin (IL)-6 expression. In the type 2 diabetes and metabolic syndrome models, CCL4 inhibition retarded the progression of hyperglycemia, reduced serum tumor necrosis factor (TNF)-α and IL-6 levels, and improved insulin resistance via reducing the phosphorylation of insulin receptor substrate-1 in skeletal muscle and liver tissues. CCL4 inhibition directly protected pancreatic β-cells from streptozotocin stimulation. Furthermore, CCL4-induced IL-6 and TNF-α expressions could be abolished by siRNA of CCR2/CCR5. In summary, direct inhibition of CCL4 protected pancreatic islet cells, improved insulin resistance and retarded the progression of hyperglycemia in different experimental models, suggesting the critical role of CCL4-related inflammation in the progression of DM. Future experiments may investigate if CCL4 could be a potential target for blood sugar control in clinical DM.

GPCRs as an emerging host-directed therapeutic target against mycobacterial infection: From notion to reality

Mycobacterium tuberculosis (M. tb) is one of the successful pathogens and claim millions of deaths across the globe. The emergence of drug resistance in M. tb has created new hurdles in the tuberculosis elimination programme worldwide. Hence, there is an unmet medical need for alternative therapy, which could be achieved by targeting the host's critical signalling pathways that are compromised during M. tb infection. In this review, we have summarized some of the findings involving the modulation of host GPCRs in the regulation of the mycobacterial infection. Understanding the role of these GPCRs not only unravels signalling pathways during infection but also provides clues for targeting critical signalling intermediates for the development of GPCR-based host-directive therapy.

CCL4 Inhibition in Atherosclerosis: Effects on Plaque Stability, Endothelial Cell Adhesiveness, and Macrophages Activation

Atherosclerosis is an arterial inflammatory disease. The circulating level of the C-C chemokine ligand (CCL4) is increased in atherosclerotic patients. This study aimed to investigate whether CCL4 inhibition could retard the progression of atherosclerosis. In ApoE knockout mice, CCL4 antibody treatment reduced circulating interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α levels and improved lipid profiles accompanied with upregulation of the liver X receptor. CCL4 inhibition reduced the atheroma areas and modified the progression of atheroma plaques, which consisted of a thicker fibrous cap with a reduced macrophage content and lower matrix metalloproteinase-2 and -9 expressions, suggesting the stabilization of atheroma plaques. Human coronary endothelial cells (HCAECs) and macrophages were stimulated with TNF-α or oxidized LDL (ox-LDL). The induced expression of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were attenuated by the CCL4 antibody or CCL4 si-RNA. CCL4 inhibition reduced the adhesiveness of HCAECs, which is an early sign of atherogenesis. CCL4 blockade reduced the activity of metalloproteinase-2 and -9 and the production of TNF-α and IL-6 in stimulated macrophages. The effects of CCL4 inhibition on down-regulating adhesion and inflammation proteins were obtained through the nuclear factor kappa B (NFκB) signaling pathway. The direct inhibition of CCL4 stabilized atheroma and reduced endothelial and macrophage activation. CCL4 may be a novel therapeutic target for modulating atherosclerosis.

Selective Allosteric Modulation of N-Terminally Cleaved, but Not Full Length CCL3 in CCR1

Chemokines undergo post-translational modification such as N-terminal truncations. Here, we describe how N-terminal truncation of full length CCL3^(1-70) affects its activity at CCR1. Truncated CCL3^(5-70) has 10-fold higher potency and enhanced efficacy in β-arrestin recruitment, but less than 2-fold increased potencies in G protein signaling determined by calcium release, cAMP and IP₃ formation. Small positive ago-allosteric ligands modulate the two CCL3 variants differently as the metal ion chelator bipyridine in complex with zinc (ZnBip) enhances the binding of truncated, but not full length CCL3, while a size-increase of the chelator to a chloro-substituted terpyridine (ZnClTerp), eliminates its allosteric, but not agonistic action. By employing a series of receptor mutants and in silico modeling we describe residues of importance for chemokine and small molecule binding. Notably, the chemokine receptor-conserved Glu287^7.39 interacts with the N-terminal amine of truncated CCL3^(5-70) and with Zn²⁺ of ZnBip, thereby bridging their binding sites and enabling the positive allosteric effect. Our study emphasizes that small allosteric molecules may act differently toward chemokine variants and thus selectively modulate interactions of specific chemokine subsets with their cognate receptors.

Inhibition of macrophage inflammatory protein-1β improves endothelial progenitor cell function and ischemia-induced angiogenesis in diabetes

Systemic inflammation might contribute to the impairment of neovasculogenesis and endothelial progenitor cell (EPC) function in clinical diabetes mellitus (DM). Macrophage inflammatory protein-1β (MIP-1β) is an inflammatory chemokine that may be up-regulated in clinical DM. Its role in diabetic vasculopathy was not clarified. This study aimed to investigate the role of MIP-1β in human EPCs and in neovasculogenesis in different diabetic animal models with hindlimb ischemia. EPCs chamber assay and in vitro tube formation assay were used to estimate the degree of EPC migration and tube formation abilities. Lepr^db/JNarl mice, C57BL/6 mice fed a high-fat diet, and streptozotocin-induced diabetic mice were used as different diabetic animal models. Laser Doppler imaging and flow cytometry were used to evaluate the degree of neovasculogenesis and the circulating levels of EPCs, respectively. MIP-1β impaired human EPC function for angiogenesis in vitro. Plasma MIP-1β levels were up-regulated in type 2 DM patients. MIP-1β inhibition enhanced the function and the C-X-C chemokine receptor type 4 expression of EPCs from type 2 diabetic patients, and improved EPC homing for ischemia-induced neovasculogenesis in different types of diabetic animals. MIP-1β directly impaired human EPC function. Inhibition of MIP-1β improved in vitro EPC function, and enhanced in vivo EPC homing and ischemia-induced neovasculogenesis, suggesting the critical role of MIP-1β for vasculopathy in the presence of DM.

CCL4 enhances preosteoclast migration and its receptor CCR5 downregulation by RANKL promotes osteoclastogenesis

Chemokine CCL4 (MIP-1β) is released from osteoblast cells to restore the homeostasis of hematopoietic stem cells during the activation of bone marrow. In this study, we investigated the function of CCL4 and its receptor CCR5 during osteoclastogenesis. CCL4 promoted the migration and viability of preosteoclast cells. However, CCL4 had no direct effect on the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation in mouse preosteoclast cells. In addition, CCR5 expression was rapidly reduced by RANKL treatment, which was recovered by IFN-γ during osteoclastogenesis. CCR5 downregulation by RANKL was mediated by MEK and JNK in preosteoclast cells and promoted osteoclastogenesis. These results suggest that CCL4 can enhance the recruitment of preosteoclasts to bone in the early stage, and the reduction of CCR5 promotes osteoclastogenesis when RANKL is prevalent.

Gene expression analysis for pneumonia caused by Gram-positive bacterial infection

Gram-positive bacteria are an important pathogenic factor for bacterial pneumonia. The aim of the present study was to identify the differentially expressed genes (DEGs) and to explore their associated pathways or expression patterns. Expression profiling of gene arrays from two independent datasets, GSE6269 and GSE35716, were downloaded from the Gene Expression Omnibus. The DEGs between peripheral blood samples from healthy controls and patients with bacterial pneumonia were identified. The Functional Annotation Tool in the Database for Annotation, Visualization and Integrated Discovery was used to annotate and analyze the DEGs in Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Multiple proteins were used to generate a protein-protein interaction (PPI) network. A total of 624 (621 annotated) were identified in the GSE6269 dataset and 398 (295 annotated) DEGs were identified in the GSE35716 dataset between pneumonia and healthy samples. A total of 40 common DEGs were identified between the 2 datasets, including 4 downregulated and 32 upregulated DEGs. In the GO category cellular component, melanosome was highly enriched among 11 genes; in the category biological process, the three most enriched items were regulation of ruffle assembly, negative regulation of calcium ion transport and necroptotic process. In the KEGG terms, only the nuclear factor-κB signaling pathway (Homo sapiens 04064) was significantly enriched. In the PPI network, five genes (CCL4, TIMP metallopeptidase inhibitor 1, intercellular adhesion molecule 1, plasminogen activator, urokinase receptor and cathepsin B) were identified to have a high degree of interaction with other DEGs. In conclusion, these five genes may represent key genes associated with pneumonia caused by Gram-positive bacteria. All of these results provide primary information and basic knowledge to understand the mechanisms of the pathogenesis.

HIV-Specific CD8 T Cells Producing CCL-4 Are Associated With Worse Immune Reconstitution During Chronic Infection

BACKGROUND

Immunological nonresponse represents the Achilles heel in the combination antiretroviral therapy (cART) effectiveness, and increases risk of clinical events and death. CD8 T cells play a crucial role in controlling HIV replication, and polyfunctional HIV-specific CD8 T cells have been associated with nonprogressive HIV infection. However, the possible role of polyfunctional CD8 T cells in predicting posttreatment immune reconstitution has not yet been explored. The aim of this study was to identify functional markers predictive of immunological response to cART in chronic HIV-infected patients.

METHODS

A cohort of chronic HIV-infected individuals naive to cART were enrolled in the ALPHA study. CD4/CD8 T-cell subsets, their differentiation/activation, as well as susceptibility to apoptosis were analyzed before and after 12 months of cART. Moreover, CD8 T cells polyfunctional response after HIV antigenic stimulation was also assessed.

RESULTS

Results showed a significant correlation between worse CD4 T-cell restoration and low frequency of naive CD4 T cells, high frequency of effector memory CD4 T cells, and high susceptibility to apoptosis of CD4 T cells all before cART. Moreover, CD8 functional subsets expressing total C-C motif chemokine ligand 4 (CCL-4) or in combination with CD107a and interferon gamma (IFNγ) were negatively associated with immune reconstitution.

CONCLUSIONS

In conclusion, our study shows that a more differentiated phenotype of CD4 T cells and CCL-4-producing CD8 T cells could represent valuable predictors of worse immune reconstitution. These parameters may be used as tools for identifying patients at risk of immunological failure during cART and eventually represent the basis for innovative therapeutic strategies.

Human Neutrophils Produce CCL23 in Response to Various TLR-Agonists and TNFα

CCL23, also known as myeloid progenitor inhibitory factor (MPIF)-1, macrophage inflammatory protein (MIP)-3, or CKβ8, is a member of the CC chemokine subfamily exerting its effects via CCR1 binding. By doing so, CCL23 selectively recruits resting T lymphocytes and monocytes, inhibits proliferation of myeloid progenitor cells and promotes angiogenesis. Previously, we and other groups have reported that human neutrophils are able to produce chemokines upon appropriate activation, including CCR1-binding CCL2, CCL3, and CCL4. Herein, we demonstrate that human neutrophils display the capacity to also express and release CCL23 when stimulated by R848 and, to a lesser extent, by other pro-inflammatory agonists, including LPS, Pam3CSK4, and TNFα. Notably, we show that, on a per cell basis, R848-activated neutrophils produce higher levels of CCL23 than autologous CD14⁺-monocytes activated under similar experimental conditions. By contrast, we found that, unlike CD14⁺-monocytes, neutrophils do not produce CCL23 in response to IL-4, thus indicating that they express CCL23 in a stimulus-specific fashion. Finally, we show that the production of CCL23 by R848-stimulated neutrophils is negatively modulated by IFNα, which instead enhances that of CCL2. Together, data extend our knowledge on the chemokines potentially produced by neutrophils. The ability of human neutrophils to produce CCL23 further supports the notion on the neutrophil capacity of orchestrating the recruitment of different cell types to the inflamed sites, in turn contributing to the control of the immune response.

Regulation of Chemokine Activity - A Focus on the Role of Dipeptidyl Peptidase IV/CD26

Chemokines are small, chemotactic proteins that play a crucial role in leukocyte migration and are, therefore, essential for proper functioning of the immune system. Chemokines exert their chemotactic effect by activation of chemokine receptors, which are G protein-coupled receptors (GPCRs), and interaction with glycosaminoglycans (GAGs). Furthermore, the exact chemokine function is modulated at the level of posttranslational modifications. Among the different types of posttranslational modifications that were found to occur in vitro and in vivo, i.e., proteolysis, citrullination, glycosylation, and nitration, NH₂-terminal proteolysis of chemokines has been described most intensively. Since the NH₂-terminal chemokine domain mediates receptor interaction, NH₂-terminal modification by limited proteolysis or amino acid side chain modification can drastically affect their biological activity. An enzyme that has been shown to provoke NH₂-terminal proteolysis of various chemokines is dipeptidyl peptidase IV or CD26. This multifunctional protein is a serine protease that preferably cleaves dipeptides from the NH₂-terminal region of peptides and proteins with a proline or alanine residue in the penultimate position. Various chemokines possess such a proline or alanine residue, and CD26-truncated forms of these chemokines have been identified in cell culture supernatant as well as in body fluids. The effects of CD26-mediated proteolysis in the context of chemokines turned out to be highly complex. Depending on the chemokine ligand, loss of these two NH₂-terminal amino acids can result in either an increased or a decreased biological activity, enhanced receptor specificity, inactivation of the chemokine ligand, or generation of receptor antagonists. Since chemokines direct leukocyte migration in homeostatic as well as pathophysiologic conditions, CD26-mediated proteolytic processing of these chemotactic proteins may have significant consequences for appropriate functioning of the immune system. After introducing the chemokine family together with the GPCRs and GAGs, as main interaction partners of chemokines, and discussing the different forms of posttranslational modifications, this review will focus on the intriguing relationship of chemokines with the serine protease CD26.

CD84 mediates CLL-microenvironment interactions

Chronic lymphocytic leukemia (CLL) is a malignant disease of small mature lymphocytes. Signals from the CLL microenvironment promote progression of the disease and induce drug resistance. This phenomenon is largely dependent on direct contact between the malignant B cells and stromal cells. CD84 belongs to the signaling lymphocyte activation molecule family of immunoreceptors, which self-associates, forming an orthogonal homophilic dimer. We therefore hypothesized that CD84 may bridge between CLL cells and their microenvironment, promoting cell survival. Our in vitro results show that CD84 expressed on CLL cells interact with CD84 expressed on cells in their microenvironment, inducing cell survival in both sides. Blocking CD84 in vitro and in vivo disrupt the interaction of CLL cells with their microenvironment, resulting in induced cell death. Thus, our findings suggest novel therapeutic strategies based on the blockade of this CD84-dependent survival pathway.

Profound Anti-HIV-1 Activity of DAPTA in Monocytes/macrophages and Inhibition of CCR5-mediated Apoptosis in Neuronal Cells

Monocytes/macrophages (M/M) are strategic reservoirs of HIV-1, spreading the virus to other cells and inducing apoptosis in T-lymphocytes, astrocytes and neurons. M/M are commonly infected by R5 HIV-1 strains, which use the chemokine receptor CCR5. D-Ala-peptide T-amide (DAPTA), or Peptide T, named for its high threonine content (ASTTTNYT), is a synthetic peptide comprised of eight amino acids (185–192) of the gp120 V2 region and functions as a viral entry inhibitor by targeting selectively CCR5. The anti-HIV-1 activity of DAPTA was evaluated in M/M infected with R5 HIV-1 strains. DAPTA at 10−9M inhibited HIV-1 replication in M/M by >90%. PCR analysis of viral cDNA in M/M showed that DAPTA blocks HIV entry and in this way prevents HIV-1 infection. Moreover, DAPTA acts as a strong inhibitor and was more active than the non-peptidic CCR5 antagonist TAK-779 in inhibiting apoptosis (mediated by R5 HIV-1 strains produced and released by infected M/M) on a neuroblastoma cell line. Our results suggest that antiviral compounds which interfere with receptor mechanisms such as CCR5 could be important, either alone or in combination with other antiretroviral treatments, in preventing HIV infection in the central nervous system and the consequential neuronal damage that leads to neuronal AIDS.

Effects of Combined CCR5/Integrase Inhibitors-Based Regimen on Mucosal Immunity in HIV-Infected Patients Naïve to Antiretroviral Therapy: A Pilot Randomized Trial

Whether initiation of antiretroviral therapy (ART) regimens aimed at achieving greater concentrations within gut associated lymphoid tissue (GALT) impacts the level of mucosal immune reconstitution, inflammatory markers and the viral reservoir remains unknown. We included 12 HIV- controls and 32 ART-naïve HIV patients who were randomized to efavirenz, maraviroc or maraviroc+raltegravir, each with fixed-dose tenofovir disoproxil fumarate/emtricitabine. Rectal and duodenal biopsies were obtained at baseline and at 9 months of ART. We performed a comprehensive assay of T-cell subsets by flow cytometry, T-cell density in intestinal biopsies, plasma and tissue concentrations of antiretroviral drugs by high-performance liquid chromatography/mass spectroscopy, and plasma interleukin-6 (IL-6), lipoteichoic acid (LTA), soluble CD14 (sCD14) and zonulin-1 each measured by ELISA. Total cell-associated HIV DNA was measured in PBMC and rectal and duodenal mononuclear cells. Twenty-six HIV-infected patients completed the follow-up. In the duodenum, the quadruple regimen resulted in greater CD8+ T-cell density decline, greater normalization of mucosal CCR5+CD4+ T-cells and increase of the naïve/memory CD8+ T-cell ratio, and a greater decline of sCD14 levels and duodenal HIV DNA levels (P = 0.004 and P = 0.067, respectively), with no changes in HIV RNA in plasma or tissue. Maraviroc showed the highest drug distribution to the gut tissue, and duodenal concentrations correlated well with other T-cell markers in duodenum, i.e., the CD4/CD8 ratio, %CD4+ and %CD8+ HLA-DR+CD38+ T-cells. Maraviroc use elicited greater activation of the mucosal naïve CD8+ T-cell subset, ameliorated the distribution of the CD8+ T-cell maturational subsets and induced higher improvement of zonulin-1 levels. These data suggest that combined CCR5 and integrase inhibitor based combination therapy in ART treatment naïve patients might more effectively reconstitute duodenal immunity, decrease inflammatory markers and impact on HIV persistence by cell-dependent mechanisms, and show unique effects of MVC in duodenal immunity driven by higher drug tissue penetration and possibly by class-dependent effects.

CD26/dipeptidylpeptidase IV-chemokine interactions: double-edged regulation of inflammation and tumor biology

Review of how chemokine processing by CD26/DPP IV regulates leukocyte trafficking.

Post‐translational modification of chemokines is an essential regulatory mechanism to enhance or dampen the inflammatory response. CD26/dipeptidylpeptidase IV, ubiquitously expressed in tissues and blood, removes NH₂‐terminal dipeptides from proteins with a penultimate Pro or Ala. A large number of human chemokines, including CXCL2, CXCL6, CXCL9, CXCL10, CXCL11, CXCL12, CCL3L1, CCL4, CCL5, CCL11, CCL14, and CCL22, are cleaved by CD26; however, the efficiency is clearly influenced by the amino acids surrounding the cleavage site and although not yet proven, potentially affected by the chemokine concentration and interactions with third molecules. NH₂‐terminal cleavage of chemokines by CD26 has prominent effects on their receptor binding, signaling, and hence, in vitro and in vivo biologic activities. However, rather than having a similar result, the outcome of NH₂‐terminal truncation is highly diverse. Either no difference in activity or drastic alterations in receptor recognition/specificity and hence, chemotactic activity are observed. Analogously, chemokine‐dependent inhibition of HIV infection is enhanced (for CCL3L1 and CCL5) or decreased (for CXCL12) by CD26 cleavage. The occurrence of CD26‐processed chemokine isoforms in plasma underscores the importance of the in vitro‐observed CD26 cleavages. Through modulation of chemokine activity, CD26 regulates leukocyte/tumor cell migration and progenitor cell release from the bone marrow, as shown by use of mice treated with CD26 inhibitors or CD26 knockout mice. As chemokine processing by CD26 has a significant impact on physiologic and pathologic processes, application of CD26 inhibitors to affect chemokine function is currently explored, e.g., as add‐on therapy in viral infection and cancer.

High MIP-1β Levels in Plasma Predict Long-Term Immunological Nonresponse to Suppressive Antiretroviral Therapy in HIV Infection

BACKGROUND

HIV-infected patients who fail to reconstitute their CD4 T-cell counts during suppressive antiretroviral therapy (ART) have increased risk of both AIDS-related and non-AIDS-related morbidity and mortality. Improved understanding of immunological nonresponse (INR) is necessary to enable earlier clinical intervention.

METHODS

In a cohort of 112 HIV-infected patients starting ART, we performed a serial analysis of 32 plasma-soluble markers, assessed by multiplex cytokine and enzyme immunoassay. Samples were drawn pre-ART and during the first 3 years of treatment, with a final observation time of 8.4 years (interquartile range, 7.0-10.7 years) on ART. Long-term INR (LT-INR) was defined as failure to reach a CD4 T-cell count >350 cells per microliter. Marker stability was evaluated by parallel analysis of samples from ART-naïve and HIV-seronegative controls.

RESULTS

Baseline CD4 T-cell counts predicted subsequent LT-INR (n = 15) [odds ratio, 1.10 (95% confidence interval: 1.01 to 1.19) pr. 10 cells/μL reduction in CD4 count, P = 0.030] in the cohort as a whole, but not in patients with baseline CD4 counts <200 cells per microliter (n = 78). LT-INR was best characterized by elevated plasma levels of the CC chemokine macrophage inflammatory protein 1β (MIP-1β), both at baseline (pre-ART) and during ART. In patients with baseline CD4 counts <200 cells per microliter, baseline MIP-1β predicted LT-INR [odds ratio 1.23 (95% confidence interval: 1.02 to 1.47) per 10 pg/mL increase in MIP-1β, P = 0.029].

CONCLUSIONS

Elevated pre-ART levels of MIP-1β identified LT-INR patients who started ART at CD4 counts <200. INR was characterized by persistently high MIP-1β during suppressive ART. Thus, MIP-1β may be of use for early identification of LT-INR.

Modulating the Innate Immune Response to Influenza A Virus: Potential Therapeutic Use of Anti-Inflammatory Drugs

Infection by influenza A viruses (IAV) is frequently characterized by robust inflammation that is usually more pronounced in the case of avian influenza. It is becoming clearer that the morbidity and pathogenesis caused by IAV are consequences of this inflammatory response, with several components of the innate immune system acting as the main players. It has been postulated that using a therapeutic approach to limit the innate immune response in combination with antiviral drugs has the potential to diminish symptoms and tissue damage caused by IAV infection. Indeed, some anti-inflammatory agents have been shown to be effective in animal models in reducing IAV pathology as a proof of principle. The main challenge in developing such therapies is to selectively modulate signaling pathways that contribute to lung injury while maintaining the ability of the host cells to mount an antiviral response to control virus replication. However, the dissection of those pathways is very complex given the numerous components regulated by the same factors (i.e., NF kappa B transcription factors) and the large number of players involved in this regulation, some of which may be undescribed or unknown. This article provides a comprehensive review of the current knowledge regarding the innate immune responses associated with tissue damage by IAV infection, the understanding of which is essential for the development of effective immunomodulatory drugs. Furthermore, we summarize the recent advances on the development and evaluation of such drugs as well as the lessons learned from those studies.

Transplantation and inflammation: implications for the modification of chemokine function

Oxidative stress is a major and recurring cause of damage during inflammation, especially following organ transplantation. Initial ischaemia–reperfusion injury causes the production of many reactive oxygen and nitrogen species, and subsequent recruitment and activation of inflammatory cells can lead to further oxidative stress. This stress is well known to cause damage at the cellular level, for example by induction of senescence leading to the production of a characteristic senescence-associated secretory phenotype. Chemokines are an important component of the senescence-associated secretory phenotype, recruiting further leucocytes and reinforcing the stress and senescence responses. As well as inducing the production of proteins, including chemokines, oxidative stress can alter proteins themselves, both directly and by induction of enzymes capable of modification. These alterations can lead to important modifications to their biological activity and also alter detection by some antibodies, potentially limiting the biological relevance of some immunochemical and proteomic biomarkers. Peroxynitrite, a reactive nitrogen species generated during inflammation and ischaemia, can cause such modifications by nitrating chemokines. Matrix metalloproteinases, released by many stressed cells, can cleave chemokines, altering function, while peptidylarginine deiminases can inactivate certain chemokines by citrullination. This review discusses the relationship between inflammation and post-translational modification, focusing on the functional modulation of transplant-relevant pro-inflammatory chemokines.

HIV cure research: advances and prospects

Thirty years after the identification of HIV, a cure for HIV infection is still to be achieved. Advances of combined antiretroviral therapy (cART) in recent years have transformed HIV infection into a chronic disease when treatment is available. However, in spite of the favorable outcomes provided by the newer therapies, cART is not curative and patients are at risk of developing HIV-associated disorders. Moreover, universal access to antiretroviral treatment is restricted by financial obstacles. This review discusses the most recent strategies that have been developed in the search for an HIV cure and to improve life quality of people living with HIV.

The immunologic effects of maraviroc intensification in treated HIV-infected individuals with incomplete CD4+ T-cell recovery: a randomized trial

The CCR5 inhibitor maraviroc has been hypothesized to decrease T-cell activation in HIV-infected individuals, but its independent immunologic effects have not been established in a placebo-controlled trial. We randomized 45 HIV-infected subjects with CD4 counts <350 cells per mm(3) and plasma HIV RNA levels <48 copies per mL on antiretroviral therapy (ART) to add maraviroc vs placebo to their regimen for 24 weeks followed by 12 weeks on ART alone. Compared with placebo-treated subjects, maraviroc-treated subjects unexpectedly experienced a greater median increase in % CD38+HLA-DR+ peripheral blood CD8+ T cells at week 24 (+2.2% vs -0.7%, P = .014), and less of a decline in activated CD4+ T cells (P < .001). The % CD38+HLA-DR+ CD4+ and CD8+ T cells increased nearly twofold in rectal tissue (both P < .001), and plasma CC chemokine receptor type 5 (CCR5) ligand (macrophage-inflammatory protein 1β) levels increased 2.4-fold during maraviroc intensification (P < .001). During maraviroc intensification, plasma lipopolysaccharide declined, whereas sCD14 levels and neutrophils tended to increase in blood and rectal tissue. Although the mechanisms explaining these findings remain unclear, CCR5 ligand-mediated activation of T cells, macrophages, and neutrophils via alternative chemokine receptors should be explored. These results may have relevance for trials of maraviroc for HIV preexposure prophylaxis and graft-versus-host disease. This trial was registered at www.clinicaltrials.gov as #NCT00735072.

CC chemokine receptors and chronic inflammation--therapeutic opportunities and pharmacological challenges

Chemokines are a family of low molecular weight proteins with an essential role in leukocyte trafficking during both homeostasis and inflammation. The CC class of chemokines consists of at least 28 members (CCL1-28) that signal through 10 known chemokine receptors (CCR1-10). CC chemokine receptors are expressed predominantly by T cells and monocyte-macrophages, cell types associated predominantly with chronic inflammation occurring over weeks or years. Chronic inflammatory diseases including rheumatoid arthritis, atherosclerosis, and metabolic syndrome are characterized by continued leukocyte infiltration into the inflammatory site, driven in large part by excessive chemokine production. Over years or decades, persistent inflammation may lead to loss of tissue architecture and function, causing severe disability or, in the case of atherosclerosis, fatal outcomes such as myocardial infarction or stroke. Despite the existence of several clinical strategies for targeting chronic inflammation, these diseases remain significant causes of morbidity and mortality globally, with a concomitant economic impact. Thus, the development of novel therapeutic agents for the treatment of chronic inflammatory disease continues to be a priority. In this review we introduce CC chemokine receptors as critical mediators of chronic inflammatory responses and explore their potential role as pharmacological targets. We discuss functions of individual CC chemokine receptors based on in vitro pharmacological data as well as transgenic animal studies. Focusing on three key forms of chronic inflammation--rheumatoid arthritis, atherosclerosis, and metabolic syndrome--we describe the pathologic function of CC chemokine receptors and their possible relevance as therapeutic targets.

Chemokine oligomerization in cell signaling and migration

Chemokines are small proteins best known for their role in controlling the migration of diverse cells, particularly leukocytes. Upon binding to their G-protein-coupled receptors on the leukocytes, chemokines stimulate the signaling events that cause cytoskeletal rearrangements involved in cell movement, and migration of the cells along chemokine gradients. Depending on the cell type, chemokines also induce many other types of cellular responses including those related to defense mechanisms, cell proliferation, survival, and development. Historically, most research efforts have focused on the interaction of chemokines with their receptors, where monomeric forms of the ligands are the functionally relevant state. More recently, however, the importance of chemokine interactions with cell surface glycosaminoglycans has come to light, and in most cases appears to involve oligomeric chemokine structures. This review summarizes existing knowledge relating to the structure and function of chemokine oligomers, and emerging methodology for determining structures of complex chemokine assemblies in the future.

T cells from indolent CLL patients prevent apoptosis of leukemic B cells in vitro and have altered gene expression profile

T cells may have a role in sustaining the leukemic clone in chronic lymphocytic leukemia (CLL). In this study, we have examined the ability of T cells from CLL patients to support the survival of the leukemic B cells in vitro. Additionally, we compared global gene expression of T cells from indolent CLL patients with healthy individuals and multiple myeloma (MM) patients. Apoptosis of purified leukemic B cells was inhibited in vitro when co-cultured with increasing numbers of autologous T cells (p < 0.01) but not autologous B and T cells of normal donors. The anti-apoptotic effect exceeded that of the anti-apoptotic cytokine IL-4 (p = 0.002) and was greater with CD8+ cells (p = 0.02) than with CD4+ cells (p = 0.05). The effect was depended mainly on cell-cell contact although a significant effect was also observed in transwell experiments (p = 0.05). About 356 genes involved in different cellular pathways were deregulated in T cells of CLL patients compared to healthy individuals and MM patients. The results of gene expression profiling were verified for 6 genes (CCL4, CCL5 (RANTES), XCL1, XCL2, KLF6, and TRAF1) using qRT-PCR and immunoblotting. Our results demonstrate that CLL-derived T cells can prevent apoptosis of leukemic B cells and have altered expression of genes that may facilitate the survival of the leukemic clone.

A novel highly potent therapeutic antibody neutralizes multiple human chemokines and mimics viral immune modulation

Chemokines play a key role in leukocyte recruitment during inflammation and are implicated in the pathogenesis of a number of autoimmune diseases. As such, inhibiting chemokine signaling has been of keen interest for the development of therapeutic agents. This endeavor, however, has been hampered due to complexities in the chemokine system. Many chemokines have been shown to signal through multiple receptors and, conversely, most chemokine receptors bind to more than one chemokine. One approach to overcoming this complexity is to develop a single therapeutic agent that binds and inactivates multiple chemokines, similar to an immune evasion strategy utilized by a number of viruses. Here, we describe the development and characterization of a novel therapeutic antibody that targets a subset of human CC chemokines, specifically CCL3, CCL4, and CCL5, involved in chronic inflammatory diseases. Using a sequential immunization approach, followed by humanization and phage display affinity maturation, a therapeutic antibody was developed that displays high binding affinity towards the three targeted chemokines. In vitro, this antibody potently inhibits chemotaxis and chemokine-mediated signaling through CCR1 and CCR5, primary chemokine receptors for the targeted chemokines. Furthermore, we have demonstrated in vivo efficacy of the antibody in a SCID-hu mouse model of skin leukocyte migration, thus confirming its potential as a novel therapeutic chemokine antagonist. We anticipate that this antibody will have broad therapeutic utility in the treatment of a number of autoimmune diseases due to its ability to simultaneously neutralize multiple chemokines implicated in disease pathogenesis.

Macrophage inflammatory protein-1β and fibrinogen are synergistic predictive markers of prognosis of intermediate coronary artery lesions

OBJECTIVE

We tested the hypothesis that the plasma levels of fibrinogen and macrophage inflammatory protein (MIP)-1β are synergistic predictive markers of the prognosis of intermediate coronary artery lesions.

METHODS

A prospective study was performed on 670 patients with intermediate coronary artery lesions. Fibrinogen and MIP-1β were measured. Major adverse cardiac event (MACE) was defined as a composite of cardiovascular death, nonfatal myocardial infarction, revascularization and readmission due to angina pectoris.

RESULTS

During follow-up, 72 events occurred; 5 patients died, 7 patients suffered a nonfatal myocardial infarction, 11 patients underwent revascularization and 49 patients were readmitted for angina pectoris. In patients with above-median levels of MIP-1β, a 2.62-fold risk of a MACE [95% confidence interval (CI) 1.53-4.48] was predicted compared with patients with below-median levels of MIP-1β. However, the strongest risk prediction was achieved by assessing MIP-1β and fibrinogen together. After adjusting for traditional risk factors, a multivariate Cox proportional hazards analysis showed that patients with both MIP-1β and fibrinogen above the median had a 4.37-fold risk of a MACE (95% CI 1.89-10.11).

CONCLUSION

MIP-1β accurately predicted MACEs. Considering MIP-1β and fibrinogen together may improve long-term risk assessment. These two biomarkers have a synergistic effect for assessing long-term risk in patients with intermediate coronary artery lesions.

Genetic variations and heterosexual HIV-1 infection: analysis of clustered genes encoding CC-motif chemokine ligands

Several CC-motif chemokine ligands (CCLs) can block HIV-1-binding sites on CC-motif chemokine receptor 5 (CCR5) and inhibit viral entry. We studied single-nucleotide polymorphisms (SNPs) in genes encoding three CCR5 ligands (CCL3 (MIP-1a), CCL4 (MIP-1b)and CCL5 (RANTES)) along with an adjacent gene encoding a CCR2ligand (CCL2 (MCP-1)) to identify candidate markers for HIV-1 infection and pathogenesis. Analyses of 567 HIV-1 serodiscordant Zambian couples revealed that rs5029410C (in CCL3 intron 2) was associated with lower viral load (VL) in seroconverters, adjusted for gender and age (regression β=-0.57 log(10), P=4x10(-6)). Inaddition, rs34171309A in CCL3 exon 3 was associated with increased risk of HIV-1 acquisition in exposed seronegatives(hazard ratio=1.52, P=0.006 when adjusted for VL of the initially seropositive partner and genital ulcer/inflammation). SNPrs34171309 encodes a conservative Glu-to-Asp substitution. Fiven eighboring SNPs in tight linkage disequilibrium with rs34171309all showed similar associations with HIV-1 acquisition. How these multiple CCL3 SNPs may alter the occurrence or course of HIV-1 infection remains to be determined [corrected].

Copy number variation in chemokine superfamily: the complex scene of CCL3L-CCL4L genes in health and disease

Genome copy number changes (copy number variations: CNVs) include inherited, de novo and somatically acquired deviations from a diploid state within a particular chromosomal segment. CNVs are frequent in higher eukaryotes and associated with a substantial portion of inherited and acquired risk for various human diseases. CNVs are distributed widely in the genomes of apparently healthy individuals and thus constitute significant amounts of population-based genomic variation. Human CNV loci are enriched for immune genes and one of the most striking examples of CNV in humans involves a genomic region containing the chemokine genes CCL3L and CCL4L. The CCL3L-CCL4L copy number variable region (CNVR) shows extensive architectural complexity, with smaller CNVs within the larger ones and with interindividual variation in breakpoints. Furthermore, the individual genes embedded in this CNVR account for an additional level of genetic and mRNA complexity: CCL4L1 and CCL4L2 have identical exonic sequences but produce a different pattern of mRNAs. CCL3L2 was considered previously as a CCL3L1 pseudogene, but is actually transcribed. Since 2005, CCL3L-CCL4L CNV has been associated extensively with various human immunodeficiency virus-related outcomes, but some recent studies called these associations into question. This controversy may be due in part to the differences in alternative methods for quantifying gene copy number and differentiating the individual genes. This review summarizes and discusses the current knowledge about CCL3L-CCL4L CNV and points out that elucidating their complete phenotypic impact requires dissecting the combinatorial genomic complexity posed by various proportions of distinct CCL3L and CCL4L genes among individuals.

The role of chemokines as inflammatory mediators in chronic hepatitis C virus infection

Hepatitis C virus (HCV) is a leading cause of chronic liver disease that can progress to cirrhosis and/or hepatocellular carcinoma. Intrahepatic inflammation and liver cell injury are defining features of chronic HCV infection. Chemokines, chemotactic cytokines that attract leucocytes to inflammatory sites, may be important in the development of intrahepatic inflammation. As T-helper (Th)1 inflammatory cells, characterized by interferon (IFN)-gamma and interleukin (IL)-2 secretion, predominate in the liver during chronic HCV infection, chemokines that attract these cells might be particularly important in disease progression. In this review, we focus on the role of Th1 chemokines, which are all members of the CXC or CC subfamilies. Among the CXC chemokines, the non-ELR group comprised of IFN-gamma-inducible protein 10 (IP-10), monokine induced by IFN-gamma (Mig) and IFN-inducible T-cell-alpha chemoattractant (I-TAC), attract Th1 cells through the interaction with their receptor, CXCR3. Among the CC subfamily, Th1-associated chemokines include regulated upon activation, normal T-cell expressed and secreted (RANTES) and macrophage inflammatory proteins (MIP)1alpha and beta. These chemokines attract cells through an interaction with their receptor, CCR5. While peripheral blood and intrahepatic levels of all of these chemokines are elevated in chronic hepatitis C patients, only select chemokines have been found to be correlated with hepatic inflammation. Among the six chemokines, IP-10 has uniquely been shown to have prognostic utility as a marker of treatment outcome. In the future, chemokines might be used to monitor the natural course and progression of HCV-associated liver disease, to identify patients with a high likelihood of achieving a therapeutic response, and they may even have potential as therapeutic targets.

Chemokine: receptor structure, interactions, and antagonism

Chemokines are critical mediators of cell migration during routine immune surveillance, inflammation, and development. Chemokines bind to G protein-coupled receptors and cause conformational changes that trigger intracellular signaling pathways involved in cell movement and activation. Although chemokines evolved to benefit the host, inappropriate regulation or utilization of these proteins can contribute to or cause many diseases. Specific chemokine receptors provide the portals for HIV to get into cells, and others contribute to inflammatory diseases and cancer. Thus, there is significant interest in developing receptor antagonists. To this end, the structures of ligands coupled with mutagenesis studies have revealed mechanisms for antagonism based on modified proteins. Although little direct structural information is available on the receptors, binding of small molecules to mutant receptors has allowed the identification of key residues involved in the receptor-binding pockets. In this review, we discuss the current knowledge of chemokine:receptor structure and function, and its contribution to drug discovery.

Resolvins and protectins in the termination program of acute inflammation

The physiological resolution of a well-orchestrated inflammatory response is essential to maintain homeostasis. Therefore, gaining a comprehensive understanding in molecular terms of the events that direct the termination of acute inflammation is imperative. Recently, new families of local-acting mediators were discovered that are biosynthesized from the essential fatty acids eicosapentaenoic acid and docosahexaenoic acid. These new chemical mediators are endogenously generated in inflammatory exudates collected during the resolution phase, and were termed resolvins and protectins because specific members of these families control the magnitude and duration of inflammation in animals. In addition, recent results indicate novel actions of resolvins and protectins in removing chemokines ferried from the tissue by apoptotic neutrophils and T cells during resolution. Here, we review recent advances on the biosynthesis and actions of these novel anti-inflammatory and proresolving mediators.

Apoptotic neutrophils and T cells sequester chemokines during immune response resolution through modulation of CCR5 expression

During the resolution phase of inflammation, the 'corpses' of apoptotic leukocytes are gradually cleared by macrophages. Here we report that during the resolution of peritonitis, the CCR5 chemokine receptor ligands CCL3 and CCL5 persisted in CCR5-deficient mice. CCR5 expression on apoptotic neutrophils and activated apoptotic T cells sequestered and effectively cleared CCL3 and CCL5 from sites of inflammation. CCR5 expression on late apoptotic human polymorphonuclear cells was downregulated by proinflammatory stimuli, including tumor necrosis factor, and was upregulated by 'proresolution' lipid mediators, including lipoxin A4, resolvin E1 and protectin D1. Our results suggest that CCR5+ apoptotic leukocytes act as 'terminators' of chemokine signaling during the resolution of inflammation.

N-terminal proteolytic processing by cathepsin G converts RANTES/CCL5 and related analogs into a truncated 4-68 variant

N-terminal proteolytic processing modulates the biological activity and receptor specificity of RANTES/CCL5. Previously, we showed that an unidentified protease associated with monocytes and neutrophils digests RANTES into a variant lacking three N-terminal residues (4-68 RANTES). This variant binds CCR5 but exhibits lower chemotactic and antiviral activities than unprocessed RANTES. In this study, we characterize cathepsin G as the enzyme responsible for this processing. Cell-mediated production of the 4-68 variant was abrogated by Eglin C, a leukocyte elastase and cathepsin G inhibitor, but not by the elastase inhibitor elastatinal. Further, anti-cathepsin G antibodies abrogated RANTES digestion in neutrophil cultures. In accordance, reagent cathepsin G specifically digested recombinant RANTES into the 4-68 variant. AOP-RANTES and Met-RANTES were also converted into the 4-68 variant upon exposure to cathepsin G or neutrophils, while PSC-RANTES was resistant to such cleavage. Similarly, macaque cervicovaginal lavage samples digested Met-RANTES and AOP-RANTES, but not PSC-RANTES, into the 4-68 variant and this processing was also inhibited by anti-cathepsin G antibodies. These findings suggest that cathepsin G mediates a novel pathway for regulating RANTES activity and may be relevant to the role of RANTES and its analogs in preventing HIV infection.

Multiple pathways of amino terminal processing produce two truncated variants of RANTES/CCL5

The CC chemokine regulated on activation, normal T cell expressed and secreted (RANTES)/CC chemokine ligand 5 (CCL5) is expressed by macrophages, endothelial cells, keratinocytes, and T cells during a wide variety of immune responses. Post-translational proteolysis is expected to play an important role in regulating such broad-based expression; however, the rates and modes of RANTES processing by primary cell systems remain poorly understood. Here, we show that peripheral blood mononuclear cells (PBMC) secrete RANTES as an intact molecule that is subject to three post-translational processing pathways. One occurs in the presence of serum or plasma and rapidly generates a RANTES variant lacking two N-terminal residues (3-68 RANTES). Such processing is mainly attributable to soluble CD26. A second pathway, which is evident in the absence of serum or plasma, generates 3-68 RANTES in concert with the expression of cell-surface CD26. The third pathway is unique and generates a novel variant lacking three N-terminal residues (4-68 RANTES). This variant binds CC chemokine receptor 5, exhibits reduced chemotactic and human immunodeficiency virus (HIV)-suppressive activity compared with 1-68 and 3-68 RANTES, and is generated by an unidentified enzyme associated with monocytes and neutrophils. Overall, these results indicate that the production of RANTES by primary cells is regulated by multiple processing pathways which produce two variants with different functional properties. Such findings have important implications for understanding the immunological and HIV-suppressive activities of native RANTES.

Multiple Products Derived from Two CCL4 Loci: High Incidence of a New Polymorphism in HIV+Patients

Human CCL4/macrophage inflammatory protein (MIP)-1beta and CCL3/MIP-1alpha are two highly related molecules that belong to a cluster of inflammatory CC chemokines located in chromosome 17. CCL4 and CCL3 were formed by duplication of a common ancestral gene, generating the SCYA4 and SCYA3 genes which, in turn, present a variable number of additional non-allelic copies (SCYA4L and SCYA3L1). In this study, we show that both CCL4 loci (SCYA4 and SCYA4L) are expressed and alternatively generate spliced variants lacking the second exon. In addition, we found that the SCYA4L locus is polymorphic and displays a second allelic variant (hereinafter SCYA4L2) with a nucleotide change in the intron 2 acceptor splice site compared with the one described originally (hereinafter SCYA4L1). Therefore, the pattern of SCYA4L2 transcripts is completely different from that of SCYA4L1, since SCYA4L2 uses several new acceptor splice sites and generates nine new mRNAs. Furthermore, we analyzed the contribution of each locus (SCYA4 and SCYA4L1/L2) to total CCL4 expression in human CD8 T cells by RT-amplified fragment length polymorphism and real-time PCR, and we found that L2 homozygous individuals (L2L2) only express half the levels of CCL4 compared with L1L1 individuals. The analysis of transcripts from the SCYA4L locus showed a lower level in L2 homozygous compared with L1 homozygous individuals (12% vs 52% of total CCL4 transcripts). A possible clinical relevance of these CCL4 allelic variants was suggested by the higher frequency of the L2 allele in a group of HIV(+) individuals (n = 175) when compared with controls (n = 220, 28.6% vs 16.6% (p = 0.00016)).

Macrophage inflammatory protein-1

Macrophage inflammatory protein (MIP)-1alpha was identified 15 years ago as the first of now four members of the MIP-1 CC chemokine subfamily. These proteins termed CCL3 (MIP-1alpha), CCL4 (MIP-1beta), CCL9/10 (MIP-1delta), and CCL15 (MIP-1gamma) according to the revised nomenclature for chemokines are produced by many cells, particularly macrophages, dendritic cells, and lymphocytes. MIP-1 proteins, which act via G-protein-coupled cell surface receptors (CCR1, 3, 5), e.g. expressed by lymphocytes and monocytes/macrophages (MPhi), are best known for their chemotactic and proinflammatory effects but can also promote homoeostasis. The encouraging results of preclinical studies in murine models of inflammation, i.e. asthma, arthritis, or multiple sclerosis, have led to the development of potent CCR3 and 5 antagonists, some of which are currently being tested in first clinical trials.

Post-translational control of chemokines: a role for decoy receptors?

It is well-established that chemokines play a critical role in the orchestration of inflammation and immunity. Interactions between chemokines and their receptors are essential for the homing of specific subsets of leukocytes to their functional microenvironments. They also influence other diverse biological processes such as development, leukocyte activation, Th1/Th2 polarisation, tumour metastasis, angiogenesis, and HIV pathogenesis. However, despite their importance, only now are we beginning to understand the complex regulation brought to bear on these molecules. In this review, we discuss a number of these key chemokine regulators that exert their influence once these proteins have been synthesised. We examine (i) chemokine storage, release, and presentation, (ii) protease regulation, (iii) viral manipulation of host chemokines, and (iv) natural mammalian receptor antagonists. Principally, the growing evidence for a role for decoy receptors in the chemokine system is discussed. In particular, the potential decoy function of the 'silent' pro-inflammatory chemokine receptor D6 is described alongside two other candidate decoy receptor molecules, DARC, and CCX-CKR. Dissecting the biological and pathological function of these chemokine controllers will lead to a deeper understanding of chemokine regulation, and may reveal novel strategies to therapeutically modify the chemokine system.

Chemokine-protease interactions in cancer

Solid tumour and leukemic cells expressing chemokine receptors, metastasize to chemokine-secreting organs. Chemokines indirectly affect tumour development by attracting immunocompetent cells with pro- or anti-tumoral activities. Various membrane-associated and soluble proteases selectively cleave specific chemokines. Precursor plasma chemokines (CXCL7, CCL14) need to be proteolytically processed to obtain receptor affinity. Angiogenic CXC chemokines (CXCL1, CXCL8) have increased CXCR1/CXCR2 affinity after limited NH2-terminal processing, whereas truncated angiostatic chemokines (CXCL10) show lower CXCR3 affinity without loss of angiostatic potential. NH2-terminally cleaved monocyte chemotactic proteins (CCL2, CCL7, CCL8) have impaired capacity to attract tumour-associated macrophages and function as receptor antagonists for intact CC chemokines. Migration of Th1/CCR5+ and Th2/CCR4+ effector lymphocytes toward CCR5 (CCL5, CCL3L1) and CCR4 (CCL22) ligands is affected by cleavage. Although proteolytical processing of chemokines is well studied in vitro, the direct or indirect effects on tumour invasion and metastasis are only poorly evaluated.

Functional redundancy of the human CCL4 and CCL4L1 chemokine genes

CCL4 and CCL4L1 are two CC chemokine genes located at chromosome 17q21 whose mature proteins differ at only a single amino acid. Abundant functional information exists for CCL4, however, CCL4L1 has only recently been recognized as a distinct gene, thus information describing it is wanting. The CCL4L1 protein was synthesized in Escherichia coli and compared with the CCL4 protein. Competitive binding studies using HEK-293/CCR5 cells produced comparable EC50 values for the two proteins. Similarly, chemotaxis assays with cells expressing CCR1, CCR3, or CCR5 revealed no substantial differences. CCL4L1 was somewhat more effective at inhibiting HIV-1 replication in PBMCs than was CCL4, however the difference was not statistically significant. These data combined with the observation of individual variation in CCL4L1 gene copy number [Eur. J. Immunol. 32 (2002) 3016, Genomics 83 (2004) 735] support the contention that the CCL4 and CCL4L1 proteins have redundant functions.

Amino-terminal processing of MIP-1?/CCL4 by CD26/dipeptidyl-peptidase IV

CD26 is a membrane-bound ectopeptidase with dipeptidyl peptidase IV (DPPIV) activity that has diverse functional properties in T cell physiology and in regulation of bioactive peptides. We have previously reported that activated human peripheral lymphocytes (PBL) secrete an amino-terminal truncated form of macrophage inflammatory protein (MIP)-1beta/(3-69) with novel functional specificity for CCR1, 2, and 5. In this report, we show that the full length MIP-1beta is processed by CD26/DPPIV to the truncated form and that cleavage can be blocked by DPPIV inhibitory peptides derived from HIV Tat(1-9) or the thromboxane A2 receptor, TAX2-R(1-9). Addition of Tat(1-9) or TAX2-R(1-9) peptides to PBL cultures partially blocks endogenous MIP-1beta processing. The kinetics of conversion of MIP-1beta from intact to MIP-1beta(3-69) in activated PBLs correlates with cell surface expression of CD26. Our results suggest that NH2-terminal processing of MIP-1beta and possibly other chemokines may depend on the balance between CD26/DPPIV enzymatic activity and cellular and viral proteins that modulate enzyme function.

Dipeptidyl-peptidase IV from bench to bedside: an update on structural properties, functions, and clinical aspects of the enzyme DPP IV

Dipeptidyl-peptidase IV/CD26 (DPP IV) is a cell-surface protease belonging to the prolyloligopeptidase family. It selectively removes the N-terminal dipeptide from peptides with proline or alanine in the second position. Apart from its catalytic activity, it interacts with several proteins, for instance, adenosine deaminase, the HIV gp120 protein, fibronectin, collagen, the chemokine receptor CXCR4, and the tyrosine phosphatase CD45. DPP IV is expressed on a specific set of T lymphocytes, where it is up-regulated after activation. It is also expressed in a variety of tissues, primarily on endothelial and epithelial cells. A soluble form is present in plasma and other body fluids. DPP IV has been proposed as a diagnostic or prognostic marker for various tumors, hematological malignancies, immunological, inflammatory, psychoneuroendocrine disorders, and viral infections. DPP IV truncates many bioactive peptides of medical importance. It plays a role in glucose homeostasis through proteolytic inactivation of the incretins. DPP IV inhibitors improve glucose tolerance and pancreatic islet cell function in animal models of type 2 diabetes and in diabetic patients. The role of DPP IV/ CD26 within the immune system is a combination of its exopeptidase activity and its interactions with different molecules. This enables DPP IV/CD26 to serve as a co-stimulatory molecule to influence T cell activity and to modulate chemotaxis. DPP IV is also implicated in HIV-1 entry, malignant transformation, and tumor invasion.

Macrophage inflammatory protein-1

Macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta are highly related members of the CC chemokine subfamily. Despite their structural similarities, MIP-1alpha and MIP-1beta show diverging signaling capacities. Depending on the MIP-1 subtype and its NH(2)-terminal processing, one or more of the CC chemokine receptors CCR1, CCR2, CCR3 and CCR5 are recognized. Since both human MIP-1alpha subtypes (LD78alpha and LD78beta) and MIP-1beta signal through CCR5, the major co-receptor for M-tropic HIV-1 strains, these chemokines are capable of inhibiting HIV-1 infection in susceptible cells. In this review, different aspects of human and mouse MIP-1alpha and MIP-1beta are discussed, including their protein and gene structures, their regulated production, their receptor usage and biological activities and their role in several pathologies including HIV-1 infection.