CCRL2 Expression by Specialized Lung Capillary Endothelial Cells Controls NK-cell Homing in Lung Cancer

Patterns of receptors for chemotactic factors regulate the homing of leukocytes to tissues. Here we report that the CCRL2/chemerin/CMKLR1 axis represents a selective pathway for the homing of natural killer (NK) cells to the lung. C-C motif chemokine receptor-like 2 (CCRL2) is a nonsignaling seven-transmembrane domain receptor able to control lung tumor growth. CCRL2 constitutive or conditional endothelial cell targeted ablation, or deletion of its ligand chemerin, were found to promote tumor progression in a Kras/p53Flox lung cancer cell model. This phenotype was dependent on the reduced recruitment of CD27- CD11b+ mature NK cells. Other chemotactic receptors identified in lung-infiltrating NK cells by single-cell RNA sequencing (scRNA-seq), such as Cxcr3, Cx3cr1, and S1pr5, were found to be dispensable in the regulation of NK-cell infiltration of the lung and lung tumor growth. scRNA-seq identified CCRL2 as the hallmark of general alveolar lung capillary endothelial cells. CCRL2 expression was epigenetically regulated in lung endothelium and it was upregulated by the demethylating agent 5-aza-2'-deoxycytidine (5-Aza). In vivo administration of low doses of 5-Aza induced CCRL2 upregulation, increased recruitment of NK cells, and reduced lung tumor growth. These results identify CCRL2 as an NK-cell lung homing molecule that has the potential to be exploited to promote NK cell-mediated lung immune surveillance.

Chemokine receptor CCR9 suppresses the differentiation of CD4+CD8αα+ intraepithelial T cells in the gut

The chemokine receptor CCR9 equips T cells with the ability to respond to CCL25, a chemokine that is highly expressed in the thymus and the small intestine (SI). Notably, CCR9 is mostly expressed on CD8 but not on CD4 lineage T cells, thus imposing distinct tissue tropism on CD4 and CD8 T cells. The molecular basis and the consequences for such a dichotomy, however, have not been fully examined and explained. Here, we demonstrate that the forced expression of CCR9 interferes with the tissue trafficking and differentiation of CD4 T cells in SI intraepithelial tissues. While CCR9 overexpression did not alter CD4 T cell generation in the thymus, the forced expression of CCR9 was detrimental for the proper tissue distribution of CD4 T cells in the periphery, and strikingly also for their terminal differentiation in the gut epithelium. Specifically, the differentiation of SI epithelial CD4 T cells into immunoregulatory CD4+CD8αα+ T cells was impaired by overexpression of CCR9 and conversely increased by the genetic deletion of CCR9. Collectively, our results reveal a previously unappreciated role for CCR9 in the tissue homeostasis and effector function of CD4 T cells in the gut.

COVID-19 genetic risk variants are associated with expression of multiple genes in diverse immune cell types

Common genetic polymorphisms associated with COVID-19 illness can be utilized for discovering molecular pathways and cell types driving disease pathogenesis. Given the importance of immune cells in the pathogenesis of COVID-19 illness, here we assessed the effects of COVID-19-risk variants on gene expression in a wide range of immune cell types. Transcriptome-wide association study and colocalization analysis revealed putative causal genes and the specific immune cell types where gene expression is most influenced by COVID-19-risk variants. Notable examples include OAS1 in non-classical monocytes, DTX1 in B cells, IL10RB in NK cells, CXCR6 in follicular helper T cells, CCR9 in regulatory T cells and ARL17A in TH2 cells. By analysis of transposase accessible chromatin and H3K27ac-based chromatin-interaction maps of immune cell types, we prioritized potentially functional COVID-19-risk variants. Our study highlights the potential of COVID-19 genetic risk variants to impact the function of diverse immune cell types and influence severe disease manifestations.

The CC and CXC chemokine receptors in turbot (Scophthalmus maximus L.) and their response to Aeromonas salmonicida infection

Chemokines are crucial regulators of cell mobilization for development, homeostasis, and immunity. Chemokines signal through binding to chemokine receptors, a superfamily of seven-transmembrane domain G-coupled receptors. In the present study, eleven CC chemokine receptors (CCRs) and seven CXC chemokine receptors (CXCRs) were identified from turbot genome. Phylogenetic and syntenic analyses were performed to annotate these genes, indicating the closest relationship between the turbot chemokine receptors and their counterparts of Japanese flounders (Paralichthys olivaceus). Evolutionary analyses revealed that the tandem duplications of CCR8 and CXCR3, the whole genome duplications of CCR6, CCR9, CCR12, and CXCR4, and the teleost-specific CCR12 led to the expansion of turbot chemokine receptors. In addition, turbot chemokine receptors were ubiquitously expressed in nine examined healthy tissues, with high expression levels observed in spleen, gill, and head kidney. Moreover, most turbot chemokine receptors were significantly differentially expressed in spleen and gill after Aeromonas salmonicida infection, and exhibited general down-regulations at early time points and then gradually up-regulated. Finally, protein-protein interaction network (PPI) analyses indicated that chemokine receptors interacted with a few immune-related genes such as interleukins, Grk genes, CD genes, etc. These results should be valuable for comparative immunological studies and provide insights for further functional characterization of chemokine receptors in turbots.

The relation between ACKR4 and CCR7 genes expression and breast cancer metastasis

AIMS

Breast cancer is the most severe malignant tumor in women. Chemokines and their receptors appear to be implicated in tumorigenesis and metastatic pattern. Also the scavenger atypical chemokine receptors are emerging as crucial regulators for the availability of chemokines. Therefore the aim of the present study is to evaluate the expression of CCR7, ACKR4 and their ligand; CCL21 in human breast cancer.

MAIN METHODS

In this study, RT-PCR was done to detect the expression of CCR7 and ACKR4 in 50 non-metastatic and 30 metastatic breast cancer tissue. Also CCL21 level in the serum of study group was detected by ELISA. The expression of all markers is compared to 80 control healthy individual.

KEY FINDINGS

Our results revealed the increase in expression of CCR7 and CCL21 level in metastatic group compared to non-metastatic and control groups while ACKR4 expression is significantly increased in breast tissues of non-metastatic patients compared to both control and metastatic groups. Also there was significant positive correlation between CCR7 expression and CCL21 level in cancer patients and significant negative correlation between ACKR4 and both CCR-7 and CCL21 in both non-metastatic and metastatic cancer groups.

SIGNIFICANCE

Thus, it might be elucidating that ACKR4 and CCR7 could be a novel target for tumor therapy as targeting the chemokine-receptors axis might represent a powerful tool to prevent infiltration and metastasis and consequently improve cancer prognosis and treatment.

C-C motif chemokine receptor 9 regulates obesity-induced insulin resistance via inflammation of the small intestine in mice

AIMS/HYPOTHESIS

Accumulation of adipose tissue macrophages is considered pivotal in the development of obesity-associated inflammation and insulin resistance. In addition, recent studies suggest an involvement of the intestine as the primary organ in inducing hyperglycaemia and insulin resistance. We have reported that the C-C motif chemokine receptor (CCR) CCR9 is associated with intestinal immunity and has a pathogenic role in various liver diseases. However, its contribution to type 2 diabetes is unknown. In the current study, we aimed to clarify the involvement of CCR9 in the pathology of type 2 diabetes and the potential underlying mechanisms.

METHODS

To elucidate how CCR9 affects the development of metabolic phenotypes, we examined the impact of CCR9 deficiency on the pathogenesis of type 2 diabetes using male C57BL/6J (wild-type [WT]) and CCR9-deficient (CCR9 knockout [KO]) mice fed a 60% high-fat diet (HFD) for 12 weeks.

RESULTS

WT and Ccr9KO mice fed an HFD exhibited a comparable weight gain; however, glucose tolerance and insulin resistance were significantly improved in Ccr9KO mice. Moreover, visceral adipose tissue (VAT) and the liver of Ccr9KO mice presented with less inflammation and increased expression of glucose metabolism-related genes than WT mice. Ccr9 and Ccl25 expression were specifically higher in the small intestine but was not altered by HFD feeding and type 2 diabetes development. Accumulation of IFN-γ-producing CD4+ T lymphocytes and increased intestinal permeability in the small intestine was observed in WT mice following HFD feeding, but these changes were suppressed in HFD-fed Ccr9KO mice. Adoptive transfer of gut-tropic CCR9-expressing T lymphocytes partially reversed the favourable glucose tolerance found in Ccr9KO mice via exacerbated inflammation in the small intestine and VAT.

CONCLUSIONS/INTERPRETATION

CCR9 plays a central role in the pathogenesis of type 2 diabetes by inducing an inflammatory shift in the small intestine. Our findings support CCR9 as a new therapeutic target for type 2 diabetes via the gut-VAT-liver axis.

Impaired CCR9/CCL25 signalling induced by inefficient dendritic cells contributes to intestinal immune imbalance in nonalcoholic steatohepatitis

Abnormal crosstalk between gut immune and the liver was involved in nonalcoholic steatohepatitis (NASH). Mice with methionine choline-deficient (MCD) diet-induced NASH presented an imbalance of pro-(IL-6 and IFN-γ) and anti-inflammatory cytokines (IL-10) in the intestine. We also clarified that the ratio of CD4+ T cells and found that the NASH mesenteric lymph node (MLN) presents decreased numbers of CD4+Th17 cells but increased numbers of CD4+CD8+FoxP3+ regulatory T cells (Tregs). Furthermore, the intestinal immune imbalance in NASH was attributed to impaired gut chemokine receptor 9 (CCR9)/chemokine ligand 25 (CCL25) signalling, which is a crucial pathway for immune cell homing in the gut. We also demonstrated that CD4+CCR9+ T cell homing was dependent on CCL25 and that the numbers and migration abilities of CD4+CCR9+ T cells were reduced in NASH. Interestingly, the analysis of dendritic cell (DC) subsets showed that the numbers and retinal dehydrogenase (RALDH) activity of CD103+CD11b+ DCs were decreased and that the ability of these cells to upregulate CD4+ T cell CCR9 expression was damaged in NASH. Taken together, impaired intestinal CCR9/CCL25 signalling induced by CD103+CD11b+ DC dysfunction contributes to the gut immune imbalance observed in NASH.

High-Dose Neonatal Vitamin A Supplementation to Bangladeshi Infants Increases the Percentage of CCR9-Positive Treg Cells in Infants with Lower Birthweight in Early Infancy, and Decreases Plasma sCD14 Concentration and the Prevalence of Vitamin A Deficiency at Two Years of Age

BACKGROUND

Vitamin A (VA) stores are low in early infancy and may impair development of the immune system.

OBJECTIVE

This study determined if neonatal VA supplementation (VAS) affects the following: 1) development of regulatory T (Treg) cells; 2) chemokine receptor 9 (CCR9) expression, which directs mucosal targeting of immune cells; and 3) systemic endotoxin exposure as indicated by changed plasma concentrations of soluble CD14 (sCD14). Secondarily, VA status, growth, and systemic inflammation were investigated.

METHODS

In total, 306 Bangladeshi infants were randomly assigned to receive 50,000 IU VA or placebo (PL) within 48 h of birth, and immune function was assessed at 6 wk, 15 wk, and 2 y. Primary outcomes included the following: 1) peripheral blood Treg cells; 2) percentage of Treg, T, and B cells expressing CCR9; and 3) plasma sCD14. Secondary outcomes included the following: 4) VA status measured using the modified relative dose-response (MRDR) test and plasma retinol; 5) infant growth; and 6) plasma C-reactive protein (CRP). Statistical analysis identified group differences and interactions with sex and birthweight.

RESULTS

VAS increased (P = 0.004) the percentage of CCR9+ Treg cells (13.2 ± 1.37%) relative to PL (9.17 ± 1.15%) in children below the median birthweight but had the opposite effect (P = 0.04) in those with higher birthweight (VA, 9.13 ± 0.89; PL, 12.1 ± 1.31%) at 6 and 15 wk (values are combined mean ± SE). VAS decreased (P = 0.003) plasma sCD14 (1.56 ± 0.025 mg/L) relative to PL (1.67 ± 0.032 mg/L) and decreased (P = 0.034) the prevalence of VA deficiency (2.3%) relative to PL (9.2%) at 2 y.

CONCLUSIONS

Neonatal VAS enhanced mucosal targeting of Treg cells in low-birthweight infants. The decreased systemic exposure to endotoxin and improved VA status at 2 y may have been due to VA-mediated improvements in gut development resulting in improved barrier function and nutrient absorption. This trial was registered at clinicaltrials.gov as NCT01583972 and NCT02027610.

Single-cell mapping reveals new markers and functions of lymphatic endothelial cells in lymph nodes

Lymph nodes (LNs) are highly organized secondary lymphoid organs that mediate adaptive immune responses to antigens delivered via afferent lymphatic vessels. Lymphatic endothelial cells (LECs) line intranodal lymphatic sinuses and organize lymph and antigen distribution. LECs also directly regulate T cells, mediating peripheral tolerance to self-antigens, and play a major role in many diseases, including cancer metastasis. However, little is known about the phenotypic and functional heterogeneity of LN LECs. Using single-cell RNA sequencing, we comprehensively defined the transcriptome of LECs in murine skin-draining LNs and identified new markers and functions of distinct LEC subpopulations. We found that LECs residing in the subcapsular sinus (SCS) have an unanticipated function in scavenging of modified low-density lipoprotein (LDL) and also identified a specific cortical LEC subtype implicated in rapid lymphocyte egress from LNs. Our data provide new, to our knowledge, insights into the diversity of LECs in murine LNs and a rich resource for future studies into the regulation of immune responses by LN LECs.

Intratumoral delivery of CCL25 enhances immunotherapy against triple-negative breast cancer by recruiting CCR9+ T cells

CCR9⁺ T cells have an increased potential to be activated and therefore may mediate strong antitumor responses. Here, we found, however, that CCL25, the only chemokine for CCR9⁺ cells, is not expressed in human or murine triple-negative breast cancers (TNBCs), raising a hypothesis that intratumoral delivery of CCL25 may enhance antitumor immunotherapy in TNBCs. We first determined whether this approach can enhance CD47-targeted immunotherapy using a tumor acidity-responsive nanoparticle delivery system (NP-siCD47/CCL25) to sequentially release CCL25 protein and CD47 small interfering RNA in tumor. NP-siCD47/CCL25 significantly increased infiltration of CCR9⁺CD8⁺ T cells and down-regulated CD47 expression in tumor, resulting in inhibition of tumor growth and metastasis through a T cell-dependent immunity. Furthermore, the antitumor effect of NP-siCD47/CCL25 was synergistically enhanced when used in combination with programmed cell death protein-1/programmed death ligand-1 blockades. This study offers a strategy to enhance immunotherapy by promoting CCR9⁺CD8⁺ T cell tumor infiltration.

The impact of genetic adaptation on chimpanzee subspecies differentiation

Chimpanzees, humans' closest relatives, are in danger of extinction. Aside from direct human impacts such as hunting and habitat destruction, a key threat is transmissible disease. As humans continue to encroach upon their habitats, which shrink in size and grow in density, the risk of inter-population and cross-species viral transmission increases, a point dramatically made in the reverse with the global HIV/AIDS pandemic. Inhabiting central Africa, the four subspecies of chimpanzees differ in demographic history and geographical range, and are likely differentially adapted to their particular local environments. To quantitatively explore genetic adaptation, we investigated the genic enrichment for SNPs highly differentiated between chimpanzee subspecies. Previous analyses of such patterns in human populations exhibited limited evidence of adaptation. In contrast, chimpanzees show evidence of recent positive selection, with differences among subspecies. Specifically, we observe strong evidence of recent selection in eastern chimpanzees, with highly differentiated SNPs being uniquely enriched in genic sites in a way that is expected under recent adaptation but not under neutral evolution or background selection. These sites are enriched for genes involved in immune responses to pathogens, and for genes inferred to differentiate the immune response to infection by simian immunodeficiency virus (SIV) in natural vs. non-natural host species. Conversely, central chimpanzees exhibit an enrichment of signatures of positive selection only at cytokine receptors, due to selective sweeps in CCR3, CCR9 and CXCR6 -paralogs of CCR5 and CXCR4, the two major receptors utilized by HIV to enter human cells. Thus, our results suggest that positive selection has contributed to the genetic and phenotypic differentiation of chimpanzee subspecies, and that viruses likely play a predominate role in this differentiation, with SIV being a likely selective agent. Interestingly, our results suggest that SIV has elicited distinctive adaptive responses in these two chimpanzee subspecies.

Chemokine Receptor Redundancy and Specificity Are Context Dependent

Currently, we lack an understanding of the individual and combinatorial roles for chemokine receptors in the inflammatory process. We report studies on mice with a compound deletion of Ccr1, Ccr2, Ccr3, and Ccr5, which together control monocytic and eosinophilic recruitment to resting and inflamed sites. Analysis of resting tissues from these mice, and mice deficient in each individual receptor, provides clear evidence for redundant use of these receptors in establishing tissue-resident monocytic cell populations. In contrast, analysis of cellular recruitment to inflamed sites provides evidence of specificity of receptor use for distinct leukocyte subtypes and no indication of comprehensive redundancy. We find no evidence of involvement of any of these receptors in the recruitment of neutrophils or lymphocytes to resting or acutely inflamed tissues. Our data shed important light on combinatorial inflammatory chemokine receptor function and highlight Ccr2 as the primary driver of myelomonocytic cell recruitment in acutely inflamed contexts.

The CC and CXC chemokine receptors in channel catfish (Ictalurus punctatus) and their involvement in disease and hypoxia responses

Chemokines are vital regulators of cell mobilization for immune surveillance, inflammation, and development. Chemokines signal through binding to their receptors that are a superfamily of seven-transmembrane domain G-coupled receptors. Recently, a complete repertoire of both CC and CXC chemokines have been identified in channel catfish, but nothing is known about their receptors. In this study, a set of 29 CC chemokine receptor (CCR) genes and 8 CXC chemokine receptor (CXCR) genes were identified and annotated from the channel catfish genome. Extensive phylogenetic and comparative genomic analyses were conducted to annotate these genes, revealing fish-specific CC chemokine receptors, and lineage-specific tandem duplications of chemokine receptors in the teleost genomes. With 29 genes, the channel catfish genome harbors the largest numbers of CC chemokine receptors among all the genomes characterized. Analysis of gene expression after bacterial infections indicated that the chemokine receptors were regulated in a gene-specific manner. Most differentially expressed chemokine receptors were up-regulated after Edwardsiella ictaluri and Flavobacterium columnare infection. Among which, CXCR3 and CXCR4 were observed to participate in immune responses to both bacterial infections, indicating their potential roles in catfish immune activities. In addition, CXCR3.2 was significantly up-regulated in ESC-susceptible fish, and CXCR4b was mildly induced in ESC-resistant fish, further supporting the significant roles of CXCR3 and CXCR4 in catfish immune responses. CXCR4b and CCR9a were both up-regulated not only after bacterial infection, but also after hypoxia stress, providing the linkage between bacterial infection and low oxygen stresses. These results should be valuable for comparative immunological studies and provide insights into their roles in disease and stress responses.

Molecular characterization and expression analysis of four fish-specific CC chemokine receptors CCR4La, CCR4Lc1, CCR4Lc2 and CCR11 in rainbow trout (Oncorhynchus mykiss)

The chemokine and chemokine receptor networks regulate leukocyte trafficking, inflammation, immune cell differentiation, cancer and other biological processes. Comparative immunological studies have revealed that both chemokines and their receptors have expanded greatly in a species/lineage specific way. Of the 10 human CC chemokine receptors (CCR1-10) that bind CC chemokines, orthologues only to CCR6, 7, 9 and 10 are present in teleost fish. In this study, four fish-specific CCRs, termed as CCR4La, CCR4Lc1, CCR4Lc2 and CCR11, with a close link to human CCR1-5 and 8, in terms of amino acid homology and syntenic conservation, have been identified and characterized in rainbow trout (Oncorhynchus mykiss). These CCRs were found to possess the conserved features of the G protein-linked receptor family, including an extracellular N-terminal, seven TM domains, three extracellular loops and three intracellular loops, and a cytoplasmic carboxyl tail with multiple potential serine/threonine phosphorylation sites. Four cysteine residues known to be involved in forming two disulfide bonds are present in the extracellular domains and a DRY motif is present in the second intracellular loop. Signaling mediated by these receptors might be regulated by N-glycosylation, tyrosine sulfation, S-palmitoylation, a PDZ ligand motif and di-leucine motifs. Studies of intron/exon structure revealed distinct fish-specific CCR gene organization in different fish species/lineages that might contribute to the diversification of the chemokine ligand-receptor networks in different fish lineages. Fish-specific trout CCRs are highly expressed in immune tissues/organs, such as thymus, spleen, head kidney and gills. Their expression can be induced by the pro-inflammatory cytokines, IL-1β, IL-6 and IFNγ, by the pathogen associated molecular patterns, PolyIC and peptidoglycan, and by bacterial infection. These data suggest that fish-specific CCRs are likely to have an important role in immune regulation in fish.

Intestinal Dendritic Cells Are Altered in Number, Maturity and Chemotactic Ability in Fulminant Hepatic Failure

Fulminant hepatic failure (FHF) is defined as rapid acute liver injury, often complicated with spontaneous bacterial peritonitis (SBP). The precise onset of FHF with SBP is still unknown, but it is thought that SBP closely correlates with a weakened intestinal barrier. Dendritic cells (DCs) play a crucial role in forming the intestinal immune barrier, therefore the number, maturity and chemotactic ability of intestinal DCs were studied in FHF. Mouse intestinal and spleen DCs were isolated by magnetic-activated cell sorting (MACS) and surface markers of DCs, namely CD11c, CD74, CD83 and CD86, were identified using flow cytometry. Immunohistochemistry and Western blotting were performed to detect the distribution and expression of CC-chemokine receptor 7 (CCR7) and CC-chemokine receptor 9 (CCR9), as well as their ligands-CC-chemokine ligand 21 (CCL21) and CC-chemokine ligand 25 (CCL25). Real-time PCR was used to detect CCR7 and CCR9 mRNA, along with their ligands-CCL21 and CCL25 mRNA. Flow cytometry analysis showed that the markers CD74, CD83 and CD86 of CD11c+DCs were lower in the D-galactosamine (D-GalN) group and were significantly decreased in the FHF group, while there were no significant changes in the expression of these markers in the lipopolysaccharide (LPS) group. Immunohistochemistry results showed that staining for CCR7 and CCR9, as well as their ligands CCL21 and CCL25, was significantly weaker in the D-GalN and FHF groups compared with the normal saline (NS) group or the LPS group; the FHF group even showed completely unstained parts. Protein expression of CCR7 and CCR9, as well as their ligands- CCL21 and CCL25, was also lower in the D-GalN group and decreased even more significantly in the FHF group. At the gene level, CCR7 and CCR9, along with CCL21 and CCL25 mRNA expression, was lower in the D-GalN group and significantly decreased in the FHF group compared to the NS and LPS groups, consisting with the protein expression. Our study indicated that intestinal DCs were decreased in number, maturity and chemotactic ability in FHF and might contribute to a decreased function of the intestinal immune barrier in FHF.

Oral Vaccination with Attenuated Salmonella typhimurium-Delivered TsPmy DNA Vaccine Elicits Protective Immunity against Trichinella spiralis in BALB/c Mice

Background

Our previous studies showed that Trichinella spiralis paramyosin (TsPmy) is an immunomodulatory protein that inhibits complement C1q and C8/C9 to evade host complement attack. Vaccination with recombinant TsPmy protein induced protective immunity against T. spiralis larval challenge. Due to the difficulty in producing TsPmy as a soluble recombinant protein, we prepared a DNA vaccine as an alternative approach in order to elicit a robust immunity against Trichinella infection.

Methods and Findings

The full-length TsPmy coding DNA was cloned into the eukaryotic expression plasmid pVAX1, and the recombinant pVAX1/TsPmy was transformed into attenuated Salmonella typhimurium strain SL7207. Oral vaccination of mice with this attenuated Salmonella-delivered TsPmy DNA vaccine elicited a significant mucosal sIgA response in the intestine and a systemic IgG antibody response with IgG2a as the predominant subclass. Cytokine analysis also showed a significant increase in the Th1 (IFN-γ, IL-2) and Th2 (IL-4, 5, 6, 10) responses in lymphocytes from the spleen and MLNs of immunized mice upon stimulation with TsPmy protein. The expression of the homing receptors CCR9/CCR10 on antibody secreting B cells may be related to the translocation of IgA-secreted B cells to local intestinal mucosa. The mice immunized with Salmonella-delivered TsPmy DNA vaccine produced a significant 44.8% reduction in adult worm and a 46.6% reduction in muscle larvae after challenge with T. spiralis larvae.

Conclusion

Our results demonstrated that oral vaccination with TsPmy DNA delivered by live attenuated S. typhimurium elicited a significant local IgA response and a mixed Th1/Th2 immune response that elicited a significant protection against T. spiralis infection in mice.

Trichinellosis is one of the most important food-borne parasitic zoonoses, and a serious public health issue worldwide. Developing a vaccine is an alternative approach to control the disease. TsPmy is a paramyosin expressed by Trichinella spiralis to bind and neutralize human complement and a vaccine antigen. We made a DNA vaccine of TsPmy orally delivered by attenuated Salmonella typhimurium that elicited a robust Th1/Th2 and mucosa IgA responses, and protected mice against T. spiralis infection with significant worm reduction against larval challenge. The attenuated Salmonella-delivered TsPmy DNA vaccine provides a feasible and promising approach for controlling trichinellosis in human and domestic animals.

Intestinal CCL25 expression is increased in colitis and correlates with inflammatory activity

CCL25-mediated activation of CCR9 is critical for mucosal lymphocyte recruitment to the intestine. In immune-mediated liver injury complicating inflammatory bowel disease, intrahepatic activation of this pathway allows mucosal lymphocytes to be recruited to the liver, driving hepatobiliary destruction in primary sclerosing cholangitis (PSC). However, in mice and healthy humans CCL25 expression is restricted to the small bowel, whereas few data exist on activation of this pathway in the inflamed colon despite the vast majority of PSC patients having ulcerative colitis. Herein, we show that colonic CCL25 expression is not only upregulated in patients with active colitis, but strongly correlates with endoscopic Mayo score and mucosal TNFα expression. Moreover, approximately 90% (CD4(+)) and 30% (CD8(+)) of tissue-infiltrating T-cells in colitis were identified as CCR9(+) effector lymphocytes, compared to <10% of T-cells being CCR9(+) in normal colon. Sorted CCR9(+) lymphocytes also demonstrated enhanced cellular adhesion to stimulated hepatic sinusoidal endothelium compared with their CCR9(-) counterparts when under flow. Collectively, these results suggest that CCR9/CCL25 interactions are not only involved in colitis pathogenesis but also correlate with colonic inflammatory burden; further supporting the existence of overlapping mucosal lymphocyte recruitment pathways between the inflamed colon and liver.

The lymph nodes draining the small intestine and colon are anatomically separate and immunologically distinct

Dendritic cells (DCs) in the small intestine (SI) and colon are fundamental to direct intestinal immune responses; they migrate to the mesenteric lymph nodes (MLNs) and prime T cells. We demonstrate anatomical segregation of lymphatic drainage from the intestine, specifically that DCs from the SI and colon migrate to different nodes within the MLN, here called the sMLN and cMLN. As a consequence, different frequencies of DC subsets observed in the SI and colon are reflected among the DCs in the sMLN and cMLN. Consistent with the SI's function in absorbing food, fed antigen is presented in the sMLN, but not in the cMLN. Furthermore, the levels of expression of CCR9 and α4β7 are increased on T cells in the sMLN compared with the cMLN. DCs from the cMLN and colon are unable to metabolize vitamin A to retinoic acid (RA); thus, DCs may contribute to the differential expression of tissue homing markers observed in the sMLN and cMLN. In summary, the sMLN and cMLN, and the DCs that migrate to these LNs are anatomically and immunologically separate. This segregation allows immune responses in the SI and colon to be controlled independently.

Unexpected Regulatory Role of CCR9 in Regulatory T Cell Development

T cells reactive to microbiota regulate the pathogenesis of inflammatory bowel disease (IBD). As T cell trafficking to intestines is regulated through interactions between highly specific chemokine-chemokine receptors, efforts have been made to develop intestine-specific immunosuppression based on blocking these key processes. CCR9, a gut-trophic chemokine receptor expressed by lymphocytes and dendritic cells, has been implicated in the regulation of IBD through mediating recruitment of T cells to inflamed sites. However, the role of CCR9 in inducing and sustaining inflammation in the context of IBD is poorly understood. In this study, we demonstrate that CCR9 deficiency in effector T cells and Tregs does not affect the development of colitis in a microbiota antigen-specific, T cell-mediated model. However, Treg cells express higher levels of CCR9 compared to those in effector T cells. Interestingly, CCR9 inhibits Treg cell development, in that CCR9-/- mice demonstrate a high level of Foxp3+ Tregs, and ligation of CCR9 by its ligand CCL25 inhibits Treg cell differentiation in vitro. Collectively, our data indicate that in addition to acting as a gut-homing molecule, CCR9 signaling shapes immune responses by inhibiting Treg cell development.

CCR9-CCL25 interaction suppresses apoptosis of lung cancer cells by activating the PI3K/Akt pathway

CC chemokine receptor-9 (CCR9) is highly expressed in non-small cell lung cancer (NSCLC) tissues and cell lines. However, the biological functions and the signals elicited by the interaction between CCR9 and its natural ligand CCL25 in NSCLC are unknown. Here, we selectively depleted CCR9 and inhibited CCR9-CCL25 interaction in NSCLC cells using small recombinant lentivirus-mediated miRNA, and investigated the tumorigenic effects in vitro and in vivo. Compromised CCR9-CCL25 interaction promoted apoptosis in NSCLC cells by activating phosphoinositide 3-kinase (PI3K)/Akt in vitro. In addition, we showed that CCR9-CCL25 interaction mediated the activation of the PI3K/Akt pathway in NSCLC cells, resulting in the up-regulation of anti-apoptotic proteins, as well as the down-regulation of apoptotic proteins in a PI3K-/Akt-dependent manner. These CCR9-CCL25-mediated effects were abrogated in the presence of a PI3K inhibitor (wortmannin 10 nM) or by inhibiting the CCR9-CCL25 interaction through CCR9 silencing, which also suggested that the biological function of CCR9-CCL25 was mainly regulated by PI3K. In vivo studies also demonstrated a significantly lower tumor burden in mice receiving CCR9-silence cells than those in mice receiving control cells. Together, these data suggested that CCR9-CCL25 interaction induced tumorigenesis of NSCLC cells and that this induction might be accomplished through the activation of the PI3K/Akt pathway. These findings may lead to a better understanding of the biological effects of CCR9-CCL25 interaction and provide clues for identifying novel therapeutic and preventive molecular markers for NSCLC.

[Chemokine CC receptors in the nervous system]

Chemoattractant cytokines (chemokines) are traditionally known as the important mediators of inflammatory processes, however, recently, is also given to their other functions in the body. Acting through specific receptors belonging to the G proteins they regulate immune processes in the body. About 20 chemokine receptors have been identified so far, and 10 of them bind chemokines CC, i.e. having in amino-terminal domain 2 adjacent molecules of cysteins. An increasing number of data indicates that chemokines and their receptors play an important role in the nervous system by acting as trophic factors, increasing the neurons survival, neural migration and synaptic transmission. Special role chemokine receptors play primarily in the diseases of the nervous system, because due to damage of the blood-brain barrier and the blood cerebrospinal fluid barrier, infiltration of leukocytes results in development of inflammation. Chemokine CC receptors has been shown to participate in Alzheimer's disease, multiple sclerosis, dementia associated with HIV infection, stroke or some type of cancers.

CCL25/CCR9 interactions regulate the function of iNKT cells in oxazolone-induced colitis in mice

BACKGROUND

Natural killer T (NKT) cells share phenotypic and functional properties with both conventional natural killer cells and T cells. These cells might have an important role in the pathogenesis of ulcerative colitis (UC). The interaction of chemokine ligand 25 (CCL25) with chemokine receptor 9 (CCR9) is involved in gut-specific migration of leukocytes and induces regulatory T cells (Tregs) to migrate to the intestine in chronic ileitis.

METHODOLOGY/FINDINGS

In UC patients, NKT receptor CD161, CCL25, and CCR9 expression levels were evaluated by qRT-PCR. A murine model of oxazolone-induced colitis was induced in BALB/c mice. The mRNA levels of NK1.1, CCL25 and CCR9, and pro-inflammatory cytokines in mice were evaluated. The CCR9 expression on Type I or invariant NKT (iNKT) cells, and the iNKT cells chemotaxis are observed according to flow cytometry. NKT receptor CD161, CCL25 and CCR9 expression levels were significantly increased in UC patients. And, the mRNA expression levels of NK1.1, CCL25 and CCR9 were increased in oxazolone-induced colitis in mice. The production of pro-inflammatory cytokines was significantly increased, especially interleukin 4 (IL-4), IL-10 and IL-13. We observed significantly increased CCR9 expression on iNKT cells. Furthermore, we found an increased iNKT population and enhanced chemotaxis during oxazolone-induced colitis.

CONCLUSIONS/SIGNIFICANCE

Our study suggests that CCL25/CCR9 interactions may promote the induction and function of iNKT cells during oxazolone-induced colitis. These findings may have important implications for UC treatment and suggest a role for CCR9 inhibitors.

Laparoscopic sleeve gastrectomy ameliorates mRNA expression of inflammation-related genes in subcutaneous adipose tissue but not in peripheral monocytes of obese patients

Low-grade inflammation links obesity, insulin resistance, and cardiovascular diseases. We investigated the effects of laparoscopic sleeve gastrectomy (LSG) on expression profile of genes involved in inflammatory pathways in subcutaneous adipose tissue (SCAT) and peripheral monocytes (PM). At baseline, obese group had significantly increased mRNA expression of proinflammatory chemokines (CCL-3, -17, -22), chemokine receptor CCR1 and cytokines (IL-10, IL-18) in SCAT and chemokine and other proinflammatory receptors (CCR-1, -2, -3, TLR-2, -4) in PM relative to control group. LSG decreased body weight, improved metabolic profile and reduced mRNA expression of up-regulated chemokine receptors, chemokines and cytokines in SCAT. In contrast, expression profiles in PM were largely unaffected by LSG. We conclude that LSG improved proinflammatory profile in subcutaneous fat but not in peripheral monocytes. The sustained proinflammatory and chemotactic profile in PM even 2 years after LSG may contribute to partial persistence of metabolic complications in obese patients after metabolic surgery.

Quercetin suppresses MIP-1α-induced adipose inflammation by downregulating its receptors CCR1/CCR5 and inhibiting inflammatory signaling

Obesity-induced inflammation is characterized by recruitment of adipose tissue macrophages that release inflammatory cytokines and chemokines. MIP-1α (macrophage inflammatory protein 1α)/CCL3, a CC chemokine, induces monocyte/macrophage infiltration and thus is implicated in obesity-induced adipose inflammation. Quercetin has been shown to modulate obesity-induced inflammation, but the mechanism of its action remains unclear. Here we demonstrate that quercetin decreases MIP-1α release from adipocytes and macrophages and from cocultured adipocytes/macrophages; it also opposes MIP-1α-induced macrophage infiltration and activation. The inhibitory action of quercetin on the MIP-1α-induced inflammatory responses of macrophages is mediated by downregulation of CCR1/CCR5, and inhibition of activation of JNK, p38 mitogen-activated-protein kinase (MAPK), and IKK as well as IκBα degradation. These findings suggest that quercetin may be a useful agent against obesity-induced adipose tissue inflammation.

Characterization of the CCR3 and CCR9 genes in miiuy croaker and different selection pressures imposed on different domains between mammals and teleosts

The innate immune system can recognize non-self through pattern recognition receptors and provides a first line of antimicrobial host defense. Thus innate immunity plays a very important role in resistance against major bacterial disease in vertebrates. In the innate immune responses, the chemokine receptors act as the main receptors of chemokines which are released at the sites of infection, inflammation and injury. In this study, the Miichthys miiuy CCR3 and CCR9 genes were cloned and characterized, showing that MIMI-CCR3 possesses a highly conserved DRYLA motif similar to that of other fishes. MIMI-CCR3 and CCR9 were ubiquitously expressed in all tested tissues and the expressions were significantly up-regulated after infection with Vibrio anguillarum except that of CCR9 in spleen. Evolutionary analysis showed that all the ancestral lineages of CCR3 and CCR9 in mammals and teleosts underwent positive selection, indicating that the ancestor of terrestrial animals further evolved to adapt to terrestrial environments and the continuous intrusion of microbes stimulated the evolution of CCR genes in the ancestor of teleost. Multiple ML methods were used to detect the robust candidates for sites under positive selection. In total, 11 and 8 positively selected sites were found in the subsets of current mammal and teleost CCR3 genes, and 3 and 2 sites were detected in the subsets of current mammals and teleosts in CCR9. Interestingly, for mammal CCR3 and CCR9 genes, the robust candidates of positively selected sites were mainly located in the extracellular domains which were the ligand binding and pathogen interaction regions. For teleost CCR3 and CCR9 genes, the positively selected sites were not only located in the extracellular domains but also in the C-terminal and intracellular domains, indicating mammals and teleosts experienced different selection pressures upon their N-terminus, C-terminus and intracellular loops of CCRs.

The specificity of targeted vaccines for APC surface molecules influences the immune response phenotype

Different diseases require different immune responses for efficient protection. Thus, prophylactic vaccines should prime the immune system for the particular type of response needed for protection against a given infectious agent. We have here tested fusion DNA vaccines which encode proteins that bivalently target influenza hemagglutinins (HA) to different surface molecules on antigen presenting cells (APC). We demonstrate that targeting to MHC class II molecules predominantly induced an antibody/Th2 response, whereas targeting to CCR1/3/5 predominantly induced a CD8⁺/Th1 T cell response. With respect to antibodies, the polarizing effect was even more pronounced upon intramuscular (i.m) delivery as compared to intradermal (i.d.) vaccination. Despite these differences in induced immune responses, both vaccines protected against a viral challenge with influenza H1N1. Substitution of HA with ovalbumin (OVA) demonstrated that polarization of immune responses, as a consequence of APC targeting specificity, could be extended to other antigens. Taken together, the results demonstrate that vaccination can be tailor-made to induce a particular phenotype of adaptive immune responses by specifically targeting different surface molecules on APCs.

The thymic medulla is required for Foxp3+ regulatory but not conventional CD4+ thymocyte development

A key role of the thymic medulla is to negatively select autoreactive CD4(+) and CD8(+) thymocytes, a process important for T cell tolerance induction. However, the involvement of the thymic medulla in other aspects of αβ T cell development, including the generation of Foxp3(+) natural regulatory T cells (nTreg cells) and the continued maturation of positively selected conventional αβ T cells, is unclear. We show that newly generated conventional CD69(+)Qa2(-) CD4 single-positive thymocytes mature to the late CD69(-)Qa2(+) stage in the absence of RelB-dependent medullary thymic epithelial cells (mTECs). Furthermore, an increasing ability to continue maturation extrathymically is observed within the CD69(+)CCR7(-/lo)CCR9(+) subset of conventional SP4 thymocytes, providing evidence for an independence from medullary support by the earliest stages after positive selection. In contrast, Foxp3(+) nTreg cell development is medullary dependent, with mTECs fostering the generation of Foxp3(-)CD25(+) nTreg cell precursors at the CD69(+)CCR7(+)CCR9(-) stage. Our results demonstrate a differential requirement for the thymic medulla in relation to CD4 conventional and Foxp3(+) thymocyte lineages, in which an intact mTEC compartment is a prerequisite for Foxp3(+) nTreg cell development through the generation of Foxp3(-)CD25(+) nTreg cell precursors.

Molecular characterization of three novel chemokine receptors in rainbow trout (Oncorhynchus mykiss)

Chemokines signal through a family of seven-transmembrane domain G-coupled receptors in order to regulate both leukocyte mobilization and activate the recruited cells. Although many chemokines have been identified in rainbow trout (Oncorhynchus mykiss), only a few chemokine receptors have been reported to date. In this work, we have cloned three novel chemokine receptors in rainbow trout. One of these receptors seems to be a clear orthologue of CCR6, while the second one constitutes a novel CCR9 gene different from the previous CCR9 reported in this species. This gene, which we have designated as CCR9B, represents another lineage of fish CCR9 genes, not previously identified. Finally, a deeper phylogenetic analysis of the third novel chemokine receptor gene, which had been identified on the basis of sequence similarity to CCR3, constitutes a novel lineage of CCR receptors which has no equivalent in humans and that may be teleost-specific. We have designated this novel gene as CCR13, to avoid any possible ascription to mammalian genes. Further transcriptional studies revealed that CCR6 was constitutively transcribed in thymus, gills, hindgut and peripheral blood leukocytes (PBLs), while CCR9B was strongly transcribed in thymus and PBLs but also in spleen, gills, hindgut and brain at lower levels. CCR13, on the other hand, was strongly detected in spleen, head kidney and PBLs and faintly in thymus, gills, brain and gonad. The data provided constitutes a step forward the identification of novel chemokine receptors that may contribute to a future understanding of chemokine signalling in fish.

CD4+CD25+ Regulatory T cell ontogeny and preferential migration to the cecal tonsils in chickens

Thymic CD4(+)CD25(+) cells have regulatory-T-cell-like properties in chickens. This study examined the ontogeny of CD4(+)CD25(+) cells in the thymus and in peripheral compartments in chickens. CD4(+)CD25(+) cells started to appear in the thymus at day 15 of incubation (E15), although at low percentages. Expressed as a percentage of CD4(+) cells, CD4(+)CD25(+) cells increased (P<0.01) from 1.7% at E20 to 7.3% at 0 d post-hatch (D0). CD4(+)CD25(+) cells did not appear in the spleen or cecal tonsils of embryos. Expressed as a percentage of CD4(+) cells, CD4(+)CD25(+) cells increased (P<0.01) from 0% at D0 to 27% at D1 in cecal tonsils and from 0% at D0 to 11% at D1 in the spleen. Expressed as a percentage of all mononuclear cells, cecal tonsils at D1 had approximately 3.5-fold higher percentage of CD4(+)CD25(+) cells than the spleen at D1. CD4(+)CD25(+) cells from cecal tonsils of chicks at D1 were suppressive. CD4(+)CD25(+) cells from D0 thymus, when injected back into MHC-compatible chicks, migrated to cecal tonsils and lungs and were detected until 10 d post-injection. CD4(+)CD25(+) cells from cecal tonsils had a higher (P = 0.01) relative amount of CCR9 mRNA than CD4(+)CD25(+) cells from the thymus. It could be concluded that in chickens CD4(+)CD25(+) cells migrate from the thymus immediately post-hatch and preferentially colonize the gut associated lymphoid tissues. CD4(+)CD25(+) cells' preferential migration to cecal tonsils is likely directed through the CCR9 pathway in chickens.

Role of exonic variation in chemokine receptor genes on AIDS: CCRL2 F167Y association with pneumocystis pneumonia

Chromosome 3p21–22 harbors two clusters of chemokine receptor genes, several of which serve as major or minor coreceptors of HIV-1. Although the genetic association of CCR5 and CCR2 variants with HIV-1 pathogenesis is well known, the role of variation in other nearby chemokine receptor genes remain unresolved. We genotyped exonic single nucleotide polymorphisms (SNPs) in chemokine receptor genes: CCR3, CCRL2, and CXCR6 (at 3p21) and CCR8 and CX3CR1 (at 3p22), the majority of which were non-synonymous. The individual SNPs were tested for their effects on disease progression and outcomes in five treatment-naïve HIV-1/AIDS natural history cohorts. In addition to the known CCR5 and CCR2 associations, significant associations were identified for CCR3, CCR8, and CCRL2 on progression to AIDS. A multivariate survival analysis pointed to a previously undetected association of a non-conservative amino acid change F167Y in CCRL2 with AIDS progression: 167F is associated with accelerated progression to AIDS (RH = 1.90, P = 0.002, corrected). Further analysis indicated that CCRL2-167F was specifically associated with more rapid development of pneumocystis pneumonia (PCP) (RH = 2.84, 95% CI 1.28–6.31) among four major AIDS–defining conditions. Considering the newly defined role of CCRL2 in lung dendritic cell trafficking, this atypical chemokine receptor may affect PCP through immune regulation and inducing inflammation.

Human chemokine receptors are cell surface proteins that may be utilized by HIV-1 for entry into host cells. DNA variation in the HIV-1 major coreceptor CCR5 affects HIV-1 infection and progression. This study comprehensively assesses the role of genetic variation of multiple chemokine receptor genes clustered in the chromosome 3p21 and 3p22 on HIV-1 disease outcomes in HIV-1 natural history cohorts. The multivariate survival analyses identified functional variants that altered disease progression rate in CCRL2, CCR3, and CCR8. CCRL2-F167Y affects the rate to AIDS development through a specific protection against pneumocystis pneumonia (PCP), a common AIDS–defining condition. Our study identified this atypical chemokine receptor CCRL2 as a key factor involved in PCP, possibly through inducing inflammation in the lung.

Commensal bacteria and expression of two major intestinal chemokines, TECK/CCL25 and MEC/CCL28, and their receptors

BACKGROUND

CCL25/TECK and CCL28/MEC are CC chemokines primarily expressed in thymic dendritic cells and mucosal epithelial cells. Their receptors, CCR9 and CCR10, are mainly expressed on T and B lymphocytes. In human, mouse, pig and sheep CCL25 and CCL28 play an important role in the segregation and the compartmentalization of the mucosal immune system. As evidenced by early comparisons of germ-free and conventional animals, the intestinal bacterial microflora has a marked effect on host intestinal immune functions. However, little is known about the impact of bacterial colonization on constitutive and induced chemokine expressions as well as on the generation of anti-inflammatory mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

Therefore, we decided to focus by qPCR on the mRNA expression of two main gut chemokines, CCL25 and CCL28, their receptors CCR9 and CCR10, the Tregs marker Foxp3 and anti-inflammatory cytokines TGF-beta and IL-10 following colonization with different bacterial species within the small intestine. To accomplish this we used an original germ-free neonatal pig model and monoassociated pigs with a representative Gram-negative (Escherichia coli) or Gram-positive (Lactobacillus fermentum) commensal bacteria commonly isolated from the neonatal pig intestine. Our results show a consistent and marked effect of microbial colonization on the mRNA expression of intestinal chemokines, chemokine receptors, Foxp3 and TGF-beta. Moreover, as evidenced by in vitro experiments using two different cell lines, the pattern of regulation of CCL25 and CCL28 expression in the gut appears complex and suggests an additional role for in vivo factors.

CONCLUSIONS/SIGNIFICANCE

Taken together, the results highlight the key role of bacterial microflora in the development of a functional intestinal immune system in an elegant and relevant model for human immune system development.