The virus-encoded chemokine vMIP-II inhibits virus-induced Tc1-driven inflammation

CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

Inflammation, immunity and potential target therapy of SARS-COV-2: A total scale analysis review

Coronavirus disease-19 (COVID-19) is a complex disease that causes illness ranging from mild to severe respiratory problems. It is caused by a novel coronavirus SARS-CoV-2 (Severe acute respiratory syndrome coronavirus-2) that is an enveloped positive-sense single-stranded RNA (+ssRNA) virus belongs to coronavirus CoV family. It has a fast-spreading potential worldwide, which leads to high mortality regardless of lows death rates. Now some vaccines or a specific drug are approved but not available for every country for disease prevention and/or treatment. Therefore, it is a high demand to identify the known drugs and test them as a possible therapeutic approach. In this critical situation, one or more of these drugs may represent the only option to treat or reduce the severity of the disease, until some specific drugs or vaccines will be developed and/or approved for everyone in this pandemic. In this updated review, the available repurpose immunotherapeutic treatment strategies are highlighted, elucidating the crosstalk between the immune system and SARS-CoV-2. Despite the reasonable data availability, the effectiveness and safety of these drugs against SARS-CoV-2 needs further studies and validations aiming for a better clinical outcome.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of Receptors CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 Ligands

CC chemokines (or β-chemokines) are 28 chemotactic cytokines with an N-terminal CC domain that play an important role in immune system cells, such as CD4⁺ and CD8⁺ lymphocytes, dendritic cells, eosinophils, macrophages, monocytes, and NK cells, as well in neoplasia. In this review, we discuss human CC motif chemokine ligands: CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 (CC motif chemokine receptor CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 ligands). We present their functioning in human physiology and in neoplasia, including their role in the proliferation, apoptosis resistance, drug resistance, migration, and invasion of cancer cells. We discuss the significance of chemokine receptors in organ-specific metastasis, as well as the influence of each chemokine on the recruitment of various cells to the tumor niche, such as cancer-associated fibroblasts (CAF), Kupffer cells, myeloid-derived suppressor cells (MDSC), osteoclasts, tumor-associated macrophages (TAM), tumor-infiltrating lymphocytes (TIL), and regulatory T cells (T_reg). Finally, we show how the effect of the chemokines on vascular endothelial cells and lymphatic endothelial cells leads to angiogenesis and lymphangiogenesis.

Novel Bivalent and D-Peptide Ligands of CXCR4 Mobilize Hematopoietic Progenitor Cells to the Blood in C3H/HeJ Mice

The interaction of SDF-1α (also known as CXCL12) with the CXCR4 receptor plays a critical role in the retention of hematopoietic stem cells (HSCs) in bone marrow. The viral macrophage inflammatory protein-II (vMIP-II), a human herpesvirus-8 (HHV-8)-encoded viral chemokine, can bind the CXCR4 receptor and inhibit endogenous ligand-induced calcium responses and cell migration. Previously, we used the bivalent ligand approach to link synthetically two unnatural D-amino acid peptides derived from the N-terminus of vMIP-II (DV1 and DV3, respectively) to generate a dimeric peptide, DV1-K-(DV3) (also named HC4319), which shows very high affinity for CXCR4. Here, we studied the biological effects of this dimeric peptide, HC4319, and its monomeric counterpart, DV1, on SDF-1α-induced signaling in CXCR4- or CXCR7-transfected Chinese hamster ovary cells and mobilization of hematopoietic progenitor cells (HPCs) in C3H/HeJ mice using an HPC assay. HC4319 and DV1 inhibited significantly the phosphorylation of Akt and Erk, known to be downstream signaling events of CXCR4. This in vivo study in C3H/HeJ mice showed that HC4319 and DV-1 strongly induced rapid mobilization of granulocyte-macrophage colony-forming units (CFUs), erythrocyte burst-forming units, and granulocyte-erythrocyte-monocyte-megakaryocyte CFUs from the bone marrow to the blood. These results provide the first reported experimental evidence that bivalent and D-amino acid peptides derived from the N-terminus of vMIP-II are potent mobilizers of HPCs in C3H/HeJ mice and support the further development of such agents for clinical application.

Chemokines encoded by herpesviruses

Viruses use diverse strategies to elude the immune system, including copying and repurposing host cytokine and cytokine receptor genes. For herpesviruses, the chemokine system of chemotactic cytokines and receptors is a common source of copied genes. Here, we review the current state of knowledge about herpesvirus-encoded chemokines and discuss their possible roles in viral pathogenesis, as well as their clinical potential as novel anti-inflammatory agents or targets for new antiviral strategies.

Kaposi sarcoma-associated herpesvirus: immunobiology, oncogenesis, and therapy

Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8, is the etiologic agent underlying Kaposi sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. This human gammaherpesvirus was discovered in 1994 by Drs. Yuan Chang and Patrick Moore. Today, there are over five thousand publications on KSHV and its associated malignancies. In this article, we review recent and ongoing developments in the KSHV field, including molecular mechanisms of KSHV pathogenesis, clinical aspects of KSHV-associated diseases, and current treatments for cancers associated with this virus.

Mimicry of cytokine pathways by human herpesviruses

ABSTRACT 

Viruses have evolved to subvert host cell pathways to enable their replication and persistence. In particular, virus-encoded gene products target the host's immune system to evade elimination by antiviral immune defenses. Cytokines are soluble, secreted proteins, which regulate many aspects of immune responses, by providing signals through cell surface receptors on target cells. Cytokine pathways are therefore attractive targets for modulation by viruses during their replication cycle. This review deals with modulation of cytokine pathways by the human herpesvirus, a family of viruses that are capable of life-long persistence in the host and cause severe disease particularly in immunocompromised individuals.

The herpesvirus 8 encoded chemokines vCCL2 (vMIP-II) and vCCL3 (vMIP-III) target the human but not the murine lymphotactin receptor

Background

Large DNA-viruses such as herpesvirus and poxvirus encode proteins that target and exploit the chemokine system of their host. The Kaposi sarcoma- associated herpes virus (KSHV) encodes three chemokines. Two of these, vCCL2 and vCCL3, target the human lymphotactin receptor as an antagonist and a selective agonist, respectively. Therefore these virally endcoded chemokines have the potential to be used as tools in the study of lymphotactin receptor pathways in murine models.

Results

The activities of vCCL2, vCCL3, human lymphotactin (XCL1) and murine lymphotactin (mXCL1) were probed in parallel on the human and murine lymphotactin receptor (XCR1 and mXCR1) using a phosphatidyl-inositol assay. On the human XCR1, vCCL3, mXCL1 and XCL1 acted as agonists. In contrast, only mXCL1 was able to activate the murine lymphotactin receptor. Using the same assay, vCCL2 was able to block the response using any of the three agonists on the humane lymphotactin receptor with IC₅₀s of 2–3 nM. However, vCCL2 was unable to block the response of mXCL1 through the murine lymphotactin receptor.

Conclusion

This study shows that vCCL2 and vCCL3 cannot be used to investigate lymphotactin receptor pathways in murine models. These results also add vCCL2 and vCCL3 to a growing list of viral chemokines with known human chemokine receptor targets, which do not target the corresponding murine receptors. This fits with the observation that viral and endogenous ligands for the same human chemokine receptor tend to have relatively divergent amino-acid sequences, suggesting that these viruses have fine-tuned the design of their chemokines such that the action of the viral encoded chemokines cannot be expected to cross species barriers.

Tumor immune escape by the loss of homeostatic chemokine expression

The novel keratinocyte-specific chemokine CCL27 plays a critical role in the organization of skin-associated immune responses by regulating T cell homing under homeostatic and inflammatory conditions. Here we demonstrate that human keratinocyte-derived skin tumors may evade T cell-mediated antitumor immune responses by down-regulating the expression of CCL27 through the activation of epidermal growth factor receptor (EGFR)-Ras-MAPK-signaling pathways. Compared with healthy skin, CCL27 mRNA and protein expression was progressively lost in transformed keratinocytes of actinic keratoses and basal and squamous cell carcinomas. In vivo, precancerous skin lesions as well as cutaneous carcinomas showed significantly elevated levels of phosphorylated ERK compared with normal skin, suggesting the activation of EGFR-Ras signaling pathways in keratinocyte-derived malignancies. In vitro, exogenous stimulation of the EGFR-Ras signaling pathway through EGF or transfection of the dominant-active form of the Ras oncogene (H-RasV12) suppressed whereas an EGFR tyrosine kinase inhibitor increased CCL27 mRNA and protein production in keratinocytes. In mice, neutralization of CCL27 led to decreased leukocyte recruitment to cutaneous tumor sites and significantly enhanced primary tumor growth. Collectively, our data identify a mechanism of skin tumors to evade host antitumor immune responses.

CCR5 and CXCR3 are dispensable for liver infiltration, but CCR5 protects against virus-induced T-cell-mediated hepatic steatosis

CCR5 and CXCR3 are important molecules in regulating the migration of activated lymphocytes. Thus, the majority of tissue-infiltrating T cells found in the context of autoimmune conditions and viral infections express CCR5 and CXCR3, and the principal chemokine ligands are expressed within inflamed tissues. Accordingly, intervention studies have pointed to nonredundant roles of these receptors in models of allograft rejection, viral infection, and autoimmunity. In spite of this, considerable controversy exists, with many studies failing to support a role for CCR5 or CXCR3 in disease pathogenesis. One possible explanation is that different chemokine receptors may take over in the absence of any individual receptor, thus rendering individual receptors redundant. We have attempted to address this issue by analyzing CCR5(-/-), CXCR3(-/-), and CCR5/CXCR3(-/-) mice with regard to virus-induced liver inflammation, generation and recruitment of effector cells, virus control, and immunopathology. Our results indicate that CCR5 and CXCR3 are largely dispensable for tissue infiltration and virus control. In contrast, the T-cell response is accelerated in CCR5(-/-) and CCR5/CXCR3(-/-) mice and the absence of CCR5 is associated with the induction of CD8(+) T-cell-mediated immunopathology consisting of marked hepatic microvesicular steatosis.

Virus-encoded chemokines, chemokine receptors and chemokine-binding proteins: new paradigms for future therapy

Over millions of years of coevolution with their hosts, viruses have learned the finest artifices of the immune system defense mechanisms and developed a variety of strategies for evading them. The chemokine system has been a primary target of these viral efforts because of the critical role it plays in the development of effective immune responses. Not only do chemokines control cellular recruitment at the site of infection, they also regulate the magnitude and character of the immune responses. Several viruses, and large DNA viruses in particular, have exploited the chemokine system by hijacking and reprogramming chemokine or chemokine-receptor genes, and/or secreting chemokine-binding proteins. In the past few years there has been intense investigation in this area, driven not only by the prospect of gaining a better understanding of viral-immune evasion mechanisms, but also by the possibility of targeting these molecules as part of future antiviral therapeutic approaches, as well as exploiting viral strategies of chemokine interference as novel therapies for inflammatory or neoplastic diseases.

Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen 1 mimics Epstein-Barr virus EBNA1 immune evasion through central repeat domain effects on protein processing

Kaposi's sarcoma-associated herpesvirus (KSHV/human herpesvirus 8 [HHV8]) and Epstein-Barr virus (EBV/HHV4) are distantly related gammaherpesviruses causing tumors in humans. KSHV latency-associated nuclear antigen 1 (LANA1) is functionally similar to the EBV nuclear antigen-1 (EBNA1) protein expressed during viral latency, although they have no amino acid similarities. EBNA1 escapes cytotoxic lymphocyte (CTL) antigen processing by inhibiting its own proteosomal degradation and retarding its own synthesis to reduce defective ribosomal product processing. We show here that the LANA1 QED-rich central repeat (CR) region, particularly the CR2CR3 subdomain, also retards LANA1 synthesis and markedly enhances LANA1 stability in vitro and in vivo. LANA1 isoforms have half-lives greater than 24 h, and fusion of the LANA1 CR2CR3 domain to a destabilized heterologous protein markedly decreases protein turnover. Unlike EBNA1, the LANA1 CR2CR3 subdomain retards translation regardless of whether it is fused to the 5' or 3' end of a heterologous gene construct. Manipulation of sequence order, orientation, and composition of the CR2 and CR3 subdomains suggests that specific peptide sequences rather than RNA structures are responsible for synthesis retardation. Although mechanistic differences exist between LANA1 and EBNA1, the primary structures of both proteins have evolved to minimize provoking CTL immune responses. Simple strategies to eliminate these viral inhibitory regions may markedly improve vaccine effectiveness by maximizing CTL responses.

Kaposi sarcoma-associated herpes virus targets the lymphotactin receptor with both a broad spectrum antagonist vCCL2 and a highly selective and potent agonist vCCL3

Large DNA viruses such as herpesvirus and poxvirus encode proteins that target and exploit the chemokine system of their host. These proteins have the potential to block or change the orchestrated recruitment of leukocytes to sites of viral infection. The genome of Kaposi sarcoma-associated herpes virus (KSHV) encodes three chemokine-like proteins named vCCL1, vCCL2, and vCCL3. In this study vCCL3 was probed in parallel with vCCL1 and vCCL2 against a panel of the 18 classified human chemokine receptors. In calcium mobilization assays vCCL1 acted as a selective CCR8 agonist, whereas vCCL2 was found to act as a broad spectrum chemokine antagonist of human chemokine receptors, including the lymphotactin receptor. In contrast vCCL3 was found to be a highly selective agonist for the human lymphotactin receptor XCR1. The potency of vCCL3 was found to be 10-fold higher than the endogenous human XCL1 chemokine in respect to phosphatidylinositol turnover and calcium mobilization as well as chemotaxis. High expression of XCR1 was found in placenta and neutrophils by real-time PCR. These data are consistent with reports of different expression profiles for vCCL2 and vCCL3 during the life cycle of KSHV, indicate a novel, sophisticated exploitation by the virus of specifically the lymphotactin receptor by both agonist and antagonist mechanisms, and suggest a unique physiological importance of this (somewhat overlooked) chemokine receptor.

Eukaryotic expression of the broad-spectrum chemokine receptor antagonist vMIP-II and its effects on T-cell function in vitro and in vivo

Pro-inflammatory chemokines and their receptors exhibit elementary functions in cell migration and in Th1-driven inflammatory conditions. One therapeutic strategy to prevent accumulation of pro-inflammatory immune cells is the use of specific chemokine receptor antagonists. An interesting and promising candidate in this context is the viral antagonist MIP-II (vMIP-II) that acts on a broad spectrum of chemokine receptors. To study the in vitro and in vivo effects of vMIP-II on pro-inflammatory chemokine receptor function, we further characterized an ovalbumin-specific murine central memory Th1IF12 clone by using RT-PCR, cDNA array and cytometry. Using in vitro chemotaxis assays we show that eukaryotically generated vMIP-II strongly inhibited migration of CCL2- or CCL5-stimulated Th1 IF12 cells. Using intravital microscopy, we observed that CCL5 induced rolling of Th1 cells in the ear vasculature of C57Bl/6 mice. Pre-treatment with vMIP-II significantly reduced CCL5-induced rolling of Th1 cells to basal levels, indicating, that vMIP-II is also active in vivo (proportion of rolling cells: 19.4 +/- 3.8%, 39.8 +/- 2.9% and 26.1 +/- 3.2%). In addition, investigating the anti-inflammatory action of vMIP-II in adoptive transfer of immunity and dinitrofluorobenzene-induced cutaneous hypersensitivity reaction using C57Bl/6 mice, we show a direct inhibitory effect of vMIP-II on the sensitization phase [Delta ear swelling 62 and 37 cm x 10(-3) for controls and vMIP-II treated mice (2.5 mg/kg), respectively] and effector phase (Delta ear swelling 14.8 and 3.6 cm x 10(-3) for controls and vMIP-II treated mice (2.5 mg/kg), respectively) of cutaneous hypersensitivity. These data indicate that vMIP-II is a promising agent to interfere with chronic inflammatory (skin) diseases.

Human gammaherpesvirus cytokines and chemokine receptors

Most herpesviruses of the beta and gamma subfamilies encode homologues of cytokines and chemokine receptor- related G protein-coupled receptors (GPCRs). The roles of these proteins during normal virus replication in the infected host have not been defined in most cases, but the available data and extrapolation from what is known about the properties and functions of their cellular counterparts indicate that they play primary roles in immune evasion or in activating cellular signaling cascades that enhance virus productive replication. Cytokines and chemokine receptors specified by the two human gammaherpesviruses, human herpesvirus 8 (HHV-8) and Epstein-Barr virus (EBV), are the subject of this review. HHV-8 encodes three chemokines, a homologue of interleukin-6, and a CXCR2-related chemokine receptor, while EBV encodes a distinct GPCR and a homologue of interleukin-10. While these viral cytokines and chemokine receptors no doubt contribute to virus biology, their properties indicate that they may also be involved in virus-induced neoplasia. This review discusses the properties, functions, and likely roles of HHV-8 and EBV cytokines and chemokine receptors in relation to both virus biology and virus-associated disease.

Opposing Effects of CXCR3 and CCR5 Deficiency on CD8+ T Cell-Mediated Inflammation in the Central Nervous System of Virus-Infected Mice

T cells play a key role in the control of viral infection in the CNS but may also contribute to immune-mediated cell damage. To study the redundancy of the chemokine receptors CXCR3 and CCR5 in regulating virus-induced CD8+ T cell-mediated inflammation in the brain, CXCR3/CCR5 double-deficient mice were generated and infected intracerebrally with noncytolytic lymphocytic choriomeningitis virus. Because these chemokine receptors are mostly expressed by overlapping subsets of activated CD8+ T cells, it was expected that absence of both receptors would synergistically impair effector T cell invasion and therefore protect mice against the otherwise fatal CD8+ T cell-mediated immune attack. Contrary to expectations, the accumulation of mononuclear cells in cerebrospinal fluid was only slightly delayed compared with mice with normal expression of both receptors. Even more surprising, CXCR3/CCR5 double-deficient mice were more susceptible to intracerebral infection than CXCR3-deficient mice. Analysis of effector T cell generation revealed an accelerated antiviral CD8+ T cell response in CXCR3/CCR5 double-deficient mice. Furthermore, while the accumulation of CD8+ T cells in the neural parenchyma was significantly delayed in both CXCR3- and CXCR3/CCR5-deficient mice, more CD8+ T cells were found in the parenchyma of double-deficient mice when these were analyzed around the time when the difference in clinical outcome becomes manifest. Taken together, these results indicate that while CXCR3 plays an important role in controlling CNS inflammation, other receptors but not CCR5 also contribute significantly. Additionally, our results suggest that CCR5 primarily functions as a negative regulator of the antiviral CD8+ T cell response.

Immune evasion by gamma-herpesviruses

Persistent viruses, such as herpesviruses, transmit infection by evading cytotoxic T cells during lytic replication. The gamma-herpesviruses additionally evade T cells during the proliferation of latently infected lymphocytes to establish a persistent viral reservoir. Lytic gene expression in sites of lymphoproliferation appears to make a vital contribution to this latent immune evasion. Lytic antigens may therefore be a key immune target. Investigations into a murine gamma-herpesvirus have now provided evidence that vaccination with apathogenic, latency-deficient mutants can largely protect against subsequent wild-type gamma-herpesvirus latency establishment.

Viral macrophage-inflammatory protein-II: a viral chemokine that differentially affects adaptive mucosal immunity compared with its mammalian counterparts

Chemokines play a profound role in leukocyte trafficking and the development of adaptive immune responses. Perhaps due to their importance in host defense, viruses have adopted many of the hallmarks displayed by chemokines. In particular, viral MIP-II (vMIP-II) is a human chemokine homologue that is encoded by human herpes virus 8. vMIP-II is angiogenic, selectively chemotactic for Th2 lymphocytes, and a homologue of human I-309 and mouse TCA-3, which also differentially attracts Th2 cells. To better understand the effect of viral chemokines on mucosal immunity, we compared the affects of vMIP-II, I-309, and TCA-3 on cellular and humoral immune responses after nasal immunization with OVA. These CCR8 ligands significantly enhanced Ag-specific serum and mucosal Abs through increasing Th2 cytokine secretion by CD4+ T cells. These alterations in adaptive humoral and cellular responses were preceded (12 h after immunization) by an increase in CD4+ T and B cells in nasal tracts with decreases of these leukocyte populations in the lung. Interestingly, vMIP-II increased neutrophil infiltration in the lung and Ag-specific IL-10-secreting CD4+ T cells after immunization. Although I-309 increased the number of CD28-, CD40L-, and CD30-positive, Ag-stimulated naive CD4+ T cells, vMIP-II and TCA-3 decreased the number of CD28-, CD40L-, and CD30-positive, resting naive CD4+ T cells. Taken together, these studies suggest that CCR8 ligands direct host Th2 responses, and vMIP-II up-regulates IL-10 responses and limits costimulatory molecule expression to mitigate host immunity.

Secreted Immunomodulatory Viral Proteins as Novel Biotherapeutics

Many viruses have learned to evade or subvert the host antiviral immune responses by encoding and expressing immunomodulatory proteins that protect the virus from attack by elements of the innate and acquired immune systems. Some of these viral anti-immune regulators are expressed as secreted proteins that engage specific host immune targets in the extracellular environment, where they exhibit potent anti-immune properties. We review here viral immunomodulatory proteins that have been tested as anti-inflammatory reagents in animal models of disease caused by excessive inflammation or hyperactivated immune pathways. The potential for such viral molecules for the development of novel drugs to treat immune-based or inflammatory disorders is discussed.

Efficient T-cell surveillance of the CNS requires expression of the CXC chemokine receptor 3

T-cells play an important role in controlling viral infections inside the CNS. To study the role of the chemokine receptor CXCR3 in the migration and positioning of virus-specific effector T-cells within the brain, CXCR3-deficient mice were infected intracerebrally with lymphocytic choriomeningitis virus (LCMV). Analysis of the induction phase of the antiviral CD8+ T-cell response did not reveal any immune defects in CXCR3-deficient mice. Yet, when mice were challenged with LCMV intracerebrally, most CXCR3-deficient mice survived the infection, whereas wild-type mice invariably died from CD8+ T-cell-mediated immunopathology. Quantitative analysis of the cellular infiltrate in CSF of infected mice revealed modest, if any, decrease in the number of mononuclear cells recruited to the meninges in the absence of CXCR3. However, immunohistological analysis disclosed a striking impairment of CD8+ T-cells from CXCR3-deficient mice to migrate from the meninges into the outer layers of the brain parenchyma despite similar localization of virus-infected target cells. Reconstitution of CXCR3-deficient mice with wild-type CD8+ T-cells completely restored susceptibility to LCMV-induced meningitis. Thus, taken together, our results strongly point to a critical role for CXCR3 in the positioning of effector T-cells at sites of viral inflammation in the brain.

I-TAC/CXCL11 is a natural antagonist for CCR5

The selective CXC chemokine receptor 3 (CXCR3) agonists, monokine induced by interferon-gamma (IFN- gamma)/CXC chemokine ligand 9 (CXCL9), IFN-inducible protein 10/CXCL10, and IFN-inducible T cell alpha chemoattractant (I-TAC)/CXCL11, attract CXCR3+ cells such as CD45RO+ T lymphocytes, B cells, and natural killer cells. Further, all three chemokines are potent, natural antagonists for chemokine receptor 3 (CCR3) and feature defensin-like, antimicrobial activities. In this study, we show that I-TAC, in addition to these effects, acts as an antagonist for CCR5. I-TAC inhibited the binding of macrophage-inflammatory protein-1alpha (MIP-1alpha)/CC chemokine ligand 3 (CCL3) to cells transfected with CCR5 and to monocytes. Furthermore, cell migration evoked by regulated on activation, normal T expressed and secreted (RANTES)/CCL5 and MIP-1beta/CCL4, the selective agonist of CCR5, was inhibited in transfected cells and monocytes, respectively. In two other functional assays, namely the release of free intracellular calcium and actin polymerization, I-TAC reduced CCR5 activities to minimal levels. Sequence and structure analyses indicate a potential role for K17, K49, and Q51 of I-TAC in CCR5 binding. Our results expand on the potential role of I-TAC as a negative modulator in leukocyte migration and activation, as I-TAC would specifically counteract the responses mediated by many "classical," inflammatory chemokines that act not only via CCR3 but via CCR5 as well.

Eotaxin-3/CCL26 is a natural antagonist for CC chemokine receptors 1 and 5. A human chemokine with a regulatory role

Eotaxin-3 (CCL26), like eotaxin (CCL11) and eotaxin-2 (CCL24), has long been considered a specific agonist for CC chemokine receptor 3 (CCR3), attracting and activating eosinophils, basophils, and Th2 type T lymphocytes. Although not characterized extensively yet, its expression profile coincides with a potential role in allergic inflammation. We recently reported that eotaxin-3 is an antagonist for CCR2 (Ogilvie, P., Paoletti, S., Clark-Lewis, I., and Uguccioni, M. (2003) Blood 102, 789-784). In the present report, we provide evidence that eotaxin-3 acts as a natural antagonist on CCR1 and -5 as well. Eotaxin-3 bound to cells transfected with either CCR1 or -5 as well as to monocytes expressing both receptors. Further, it inhibited chemotaxis, the release of free intracellular calcium, and actin polymerization when cells were stimulated with known agonists of CCR1 and -5. An analysis of its three-dimensional structure indicated the presence of two distinct epitopes that may be involved in specific binding to CCR1, -2, -3, and -5. Taken together, our data thus indicate eotaxin-3 to be the first human chemokine that features broadband antagonistic activities, suggesting that it may have a modulatory rather than an inflammatory function. Further, eotaxin-3 may play an unrecognized role in the polarization of cellular recruitment by attracting Th2 lymphocytes as well as eosinophils and basophils via CCR3, while concomitantly blocking the recruitment of Th1 lymphocytes and monocytes via CCR1, -2, and -5.

Role of macrophage inflammatory protein-1alpha in T-cell-mediated immunity to viral infection

The immune response to lymphocytic choriomeningitis virus in mice lacking macrophage inflammatory protein-1alpha (MIP-1alpha) was evaluated. Generation of virus-specific effector T cells is unimpaired in MIP-1alpha-deficient mice. Furthermore, MIP-1alpha is not required for T-cell-mediated virus control or virus-induced T-cell-dependent inflammation. Thus, MIP-1alpha is not mandatory for T-cell-mediated antiviral immunity.