Recombinant Macaca mulatta (Rhesus macaque) C-C chemokine receptor type 3 (CCR3)

What is C-C chemokine receptor type 3 (CCR3) in Macaca mulatta and what are its alternative nomenclatures?

C-C chemokine receptor type 3 (CCR3) in Macaca mulatta is a G protein-coupled receptor involved in chemokine signaling pathways that regulate immune cell trafficking and inflammatory responses. It has several alternative nomenclatures including C-C CKR-3, CC-CKR-3, CCR-3, CCR3, and CKR3. Additionally, it is identified as CD193 in the CD antigen classification system. The gene encoding CCR3 is officially designated as CCR3 with the synonym CMKBR3 . The protein's full length encompasses 355 amino acids, with the expression region documented as positions 1-355. For research purposes, it's essential to recognize these various designations to ensure comprehensive literature searches and proper experimental design.

How are recombinant CCR3 proteins from Macaca mulatta typically stored and handled for optimal stability?

Recombinant CCR3 proteins from Macaca mulatta are typically stored in Tris-based buffer with 50% glycerol, which has been optimized specifically for this protein. The recommended storage temperature is -20°C, with extended storage recommendations at either -20°C or -80°C to maintain protein integrity and activity . For working aliquots, storage at 4°C for up to one week is recommended. Repeated freezing and thawing cycles should be avoided as they can lead to protein denaturation and loss of functional activity. When handling the protein, researchers should maintain sterile conditions and consider adding protease inhibitors if working with cell or tissue lysates. Additionally, optimization of buffer conditions may be necessary depending on the specific experimental application, such as adjusting pH or ionic strength for specific binding assays or functional studies.

How does CCR3 expression in Macaca mulatta compare to its human counterpart, and what implications does this have for translational research?

Comparative analysis between Macaca mulatta CCR3 and human CCR3 reveals important insights for translational research. While both receptors share significant sequence homology, there are subtle structural differences that can impact pharmacological studies. This comparative relationship mirrors what has been observed with other chemokine receptors across these species. For instance, research on mmGMCSF (Macaca mulatta granulocyte-macrophage colony-stimulating factor) showed that despite having six amino acid differences from human GMCSF, the macaque protein demonstrated strong cross-reactivity with human receptors .

What methodological approaches are most effective for studying CCR3's role in SIV/HIV pathogenesis in the rhesus macaque model?

To investigate CCR3's role in SIV/HIV pathogenesis using rhesus macaque models, several methodological approaches have proven effective. A comprehensive strategy should combine genomic, transcriptomic, and functional analyses. For genomic studies, whole genome shotgun (WGS) read depth analysis has been successfully employed to determine copy number variations (CNV) of chemokine-related genes in macaques, which could be adapted for CCR3-related investigations . This approach requires aligning sequence fragments to the macaque reference genome with appropriate identity thresholds and comparing coverage depth across regions of interest.

For transcriptomic analyses, RNA isolation from whole blood samples followed by NextSeq 500 platform sequencing (Illumina) provides high-quality data with Phred scores typically exceeding 35, indicating excellent base call accuracy . Alignment to the Macaca mulatta Mmul_10.98 reference genome using STAR spliced read aligner achieves mapping efficiencies between 43-86% . For functional studies of CCR3 expression and activity, stimulation of peripheral blood mononuclear cells (PBMCs) with specific agents like Concanavalin A has been shown to significantly increase chemokine receptor expression , which could be adapted for CCR3 studies.

When investigating CCR3's specific role in SIV pathogenesis, longitudinal studies tracking receptor expression before and after infection are crucial. Sample collection at key timepoints (pre-infection, acute infection, and chronic phase) allows for temporal analysis of CCR3 expression patterns and correlation with disease progression markers. Integration of these methodologies provides a comprehensive understanding of CCR3's role in SIV/HIV pathogenesis.

How can researchers effectively design experiments to investigate the relationship between CCR3 genetic variations and disease susceptibility in rhesus macaques?

Designing experiments to investigate CCR3 genetic variations and disease susceptibility requires a multifaceted approach combining genetic analysis, functional validation, and disease model integration. First, researchers should establish baseline genetic variation of CCR3 in their rhesus macaque population through whole-genome sequencing or targeted gene sequencing. Investigators should collect samples from diverse rhesus macaque subpopulations, including both Indian-origin and Chinese-origin animals, as genetic diversity varies significantly between these populations, similar to what has been observed with CCL3L genes .

For quantitative assessment of gene copy number variation, real-time PCR (rtPCR) methods validated against interphase fluorescence in situ hybridization (FISH) provide reliable results. When designing rtPCR assays, researchers should use appropriate reference samples with known copy numbers and run multiple replicates (typically three) to ensure accuracy . To confirm rtPCR findings, interphase FISH can be employed as demonstrated in CCL3L studies where researchers achieved consistent results between methodologies .

Disease susceptibility studies should employ retrospective and prospective approaches. In retrospective designs, researchers can analyze banked samples from animals with known disease outcomes, while prospective studies allow monitoring of disease progression in real-time. Statistical analysis using Cox proportional hazard models enables quantification of the relationship between genetic variations and survival outcomes, adjusting for covariates like age, sex, and viral load . This approach has successfully detected significant associations between gene copy number variations and disease progression in rhesus macaque SIV models.

What expression systems are most effective for producing functional recombinant Macaca mulatta CCR3 protein?

Several expression systems can be utilized for producing functional recombinant Macaca mulatta CCR3 protein, each with distinct advantages for specific research applications. Based on successful approaches with similar macaque proteins, Escherichia coli expression systems can effectively produce CCR3 as a soluble fusion protein when appropriate fusion tags and expression conditions are employed . This approach typically involves cloning the CCR3 gene into a bacterial expression vector with a fusion partner (like thioredoxin, GST, or MBP) to enhance solubility, followed by affinity purification and protease cleavage to obtain the native protein .

For applications requiring post-translational modifications, mammalian expression systems offer significant advantages. HEK293 or CHO cells transfected with expression vectors containing the Macaca mulatta CCR3 gene can produce properly folded protein with appropriate glycosylation patterns. These systems are particularly valuable for functional studies requiring intact receptor signaling capabilities. Alternatively, baculovirus-insect cell systems provide a balance between prokaryotic and mammalian systems, offering moderate post-translational modifications with higher protein yields.

The choice of expression system should be guided by the specific research requirements. For structural studies requiring large protein quantities, E. coli or baculovirus systems may be preferable. For functional analyses investigating receptor-ligand interactions or signaling pathways, mammalian expression systems that preserve native protein conformations would be more appropriate. Regardless of the chosen system, optimization of expression conditions (temperature, induction parameters, media composition) is essential for maximizing protein yield and functionality.

What are the established protocols for measuring CCR3 expression levels in Macaca mulatta tissue samples?

Established protocols for measuring CCR3 expression in Macaca mulatta tissue samples include both mRNA and protein detection methods, each with specific advantages for different research questions. For mRNA quantification, RNA isolation from tissue samples followed by real-time quantitative PCR (RT-qPCR) provides sensitive detection of CCR3 transcript levels. This approach requires careful primer design targeting conserved regions of the CCR3 gene and appropriate reference genes for normalization. Based on successful transcriptome analysis protocols for rhesus macaques, total RNA isolation should yield high-quality RNA with RNA integrity numbers (RIN) exceeding 7.0 for reliable results .

For protein-level detection, Western blotting and flow cytometry represent complementary approaches. Western blotting allows semi-quantitative assessment of total CCR3 protein levels in tissue homogenates, while flow cytometry provides quantitative measurement of cell surface CCR3 on specific cell populations. For flow cytometry, single-cell suspensions from tissues or peripheral blood can be stained with fluorescently labeled antibodies against CCR3, alongside markers for specific cell types (e.g., CD4, CD8, CD14). Analysis gates should be established using fluorescence-minus-one (FMO) controls to accurately identify CCR3-positive populations.

Immunohistochemistry (IHC) provides valuable spatial information about CCR3 expression within intact tissue architecture. This approach requires validation of antibodies specifically reactive with Macaca mulatta CCR3, as cross-reactivity with human antibodies cannot be assumed. Positive and negative controls, including tissues known to express or lack CCR3, should be included in all experiments. For all protocols, appropriate normalization strategies (housekeeping genes for RT-qPCR, loading controls for Western blot) are essential for accurate quantification across samples.

How can researchers effectively validate the functional activity of recombinant Macaca mulatta CCR3 in vitro?

Validating the functional activity of recombinant Macaca mulatta CCR3 in vitro requires multiple complementary approaches to assess different aspects of receptor functionality. Ligand binding assays represent a fundamental validation method, typically employing radiolabeled or fluorescently labeled CCR3 ligands (eotaxin/CCL11, eotaxin-2/CCL24, or RANTES/CCL5) to measure specific binding to the recombinant receptor. Competitive binding assays with unlabeled ligands can determine binding affinities and specificities. Scatchard analysis of binding data provides quantitative measurements of receptor-ligand interaction kinetics.

Signal transduction assays provide crucial information about receptor coupling to downstream pathways. Calcium flux assays using fluorescent calcium indicators (Fluo-4 AM or Fura-2) can detect the rapid intracellular calcium mobilization that follows CCR3 activation. Alternative approaches include measuring other second messengers like cAMP or phosphorylated ERK1/2 following receptor stimulation. For more comprehensive pathway analysis, phospho-specific antibody arrays or RNA-seq can identify broader signaling networks activated by CCR3 engagement.

Cell migration assays directly assess the primary functional outcome of CCR3 activation. Transwell migration assays using eosinophils, basophils, or CCR3-transfected cell lines quantify chemotactic responses to CCR3 ligands applied in the lower chamber. Inhibition of migration by CCR3-specific antagonists confirms the receptor-dependence of the observed effects. Time-lapse microscopy provides additional insights into migration dynamics and cellular morphology changes during chemotaxis. Integration of these complementary approaches provides robust validation of recombinant CCR3 functionality across multiple dimensions of receptor activity.

How should researchers interpret variations in CCR3 expression across different macaque populations in relation to disease susceptibility?

Interpreting variations in CCR3 expression across different macaque populations requires careful consideration of multiple factors to establish meaningful connections to disease susceptibility. First, researchers must distinguish between genetic and environmental influences on expression variability. Population-specific genetic backgrounds, particularly between Indian-origin and Chinese-origin rhesus macaques, can significantly impact baseline CCR3 expression levels, similar to what has been observed with other chemokine receptors . Analysis of CCR3 expression data should therefore be stratified by population origin to avoid confounding effects.

Statistical approaches for analyzing population differences should employ mixed-effects models that account for both fixed (population origin, age, sex) and random (individual variation) effects. When correlating expression levels with disease outcomes, Cox proportional hazard models can quantify the relationship between CCR3 expression and survival time while adjusting for covariates . The predicted hazard ratio (exp(β)) offers a standardized measure of effect size that can be compared across studies. For example, in studies of CCL3L copy number variation, each additional copy decreased the baseline risk by a factor of approximately 0.907 .

Researchers should consider potential non-linear relationships between CCR3 expression and disease outcomes, as threshold effects may exist where expression below or above certain levels significantly alters susceptibility. Visualizing these relationships through Kaplan-Meier survival curves for different expression quantiles can reveal such patterns. Additionally, validation of findings across independent cohorts is essential to confirm biological significance versus cohort-specific effects. These analytical approaches provide a framework for robustly interpreting CCR3 expression variations in relation to disease outcomes in macaque populations.

What statistical approaches are recommended for analyzing CCR3 genetic variation data in relation to SIV/HIV progression?

Statistical analysis of CCR3 genetic variation in relation to SIV/HIV progression requires specialized approaches that account for the complexity of survival data and potential confounding factors. Cox proportional hazards regression models represent the gold standard for analyzing time-to-event data in this context, allowing researchers to quantify the relationship between CCR3 genetic variations and progression rates while controlling for covariates . This approach has been successfully applied to similar genetic studies, revealing that genetic factors like CCL3L copy number explain approximately 15.6% of survival time variation among Indian-origin macaques infected with SIV .

For copy number variation (CNV) analysis specifically, researchers should employ normalization strategies that account for batch effects and technical variations in assay performance. Reference samples with known copy numbers should be included in each experimental batch. When analyzing the relationship between continuous variables (like copy number) and progression, researchers should test for linearity assumptions and consider transformation or categorization if necessary. The effect size of genetic variations can be quantified using hazard ratios, where each additional copy of a gene may decrease the baseline risk by a constant factor (e.g., 0.907 for CCL3L) .

To account for population substructure effects, separate analyses for different macaque populations (Indian-origin versus Chinese-origin) are recommended, as demonstrated in studies showing population-specific genetic influences on disease progression . Power calculations should guide sample size determination, particularly for studies involving rarer genetic variants. Retrospective power analysis can help interpret negative findings, especially in smaller subpopulations. Additionally, multiple testing corrections using methods like Benjamini-Hochberg false discovery rate or Bonferroni correction should be applied when testing multiple genetic variants simultaneously to control for Type I errors.

How can transcriptomic data be integrated with protein-level analyses to better understand CCR3 function in rhesus macaque disease models?

Integration of transcriptomic and protein-level data provides a comprehensive understanding of CCR3 function in rhesus macaque disease models by capturing both regulatory and functional aspects of gene expression. For effective multi-omics integration, researchers should collect matched samples for both RNA-seq and protein analysis from the same animals at identical timepoints to enable direct correlation between transcripts and proteins. Whole blood samples can be processed for RNA isolation using established protocols that yield high-quality RNA (Phred scores >35) suitable for NextSeq 500 platform sequencing .

Transcriptomic data processing should include robust quality control measures, including pre- and post-mapping quality checks. Reads should be aligned to the current Macaca mulatta reference genome (Mmul_10.98) using spliced read aligners like STAR, which achieve mapping efficiencies between 43-86% . For protein analysis, quantitative approaches like mass spectrometry or targeted assays (ELISA, Western blot) can measure CCR3 protein levels in matching samples. Correlation analysis between mRNA and protein levels can identify potential post-transcriptional regulatory mechanisms affecting CCR3 expression.

For integrative analysis, researchers can employ several computational approaches. Co-expression network analysis identifies modules of co-regulated genes and proteins that may function together with CCR3 in disease processes. Pathway enrichment analysis using tools like GSEA or IPA can reveal biological processes enriched in differentially expressed genes and proteins. Causal network analysis using tools like Key Driver Analysis can identify potential regulatory factors controlling CCR3 expression networks. Time-course experiments analyzing both transcriptomic and proteomic changes following SIV infection can reveal dynamic regulatory relationships, with early transcriptional changes potentially predicting later protein-level alterations in CCR3 signaling pathways.

How can research on Macaca mulatta CCR3 inform the development of therapeutic interventions for human inflammatory diseases?

Research on Macaca mulatta CCR3 provides valuable insights for developing human therapeutic interventions due to significant cross-species conservation of structure and function. The structural similarities between macaque and human CCR3 create opportunities for using rhesus models to evaluate therapeutic strategies targeting this receptor. This translational potential is supported by evidence from related chemokine studies, where Macaca mulatta GMCSF showed strong cross-reactivity with human GMCSF receptors despite differences at six amino acid residues . This cross-species receptor binding capability suggests that CCR3-targeted therapies developed in macaque models may translate effectively to human applications.

For therapeutic development, rhesus macaque models offer several advantages. First, they enable evaluation of both efficacy and safety profiles of CCR3 antagonists in a physiologically relevant system before human trials. Second, macaque models allow investigation of tissue-specific effects that may not be apparent in simpler in vitro systems. Third, the ability to conduct controlled infection studies in macaques provides insights into how CCR3-targeted interventions may affect disease progression in conditions like HIV/AIDS. The observation that neutralizing agents developed against human proteins can cross-react with their macaque counterparts further supports the translational value of these models .

To maximize translational relevance, researchers should compare the pharmacological profiles of CCR3 antagonists between human and macaque receptors, identifying any species-specific differences in binding affinity or signaling outcomes. Additionally, therapeutic dosing should account for potential variations in receptor density or distribution between species. By carefully addressing these considerations, research on Macaca mulatta CCR3 can accelerate the development of effective therapeutic interventions for human inflammatory diseases mediated by this important chemokine receptor.

What research gaps remain in understanding the comparative immunology of CCR3 between humans and rhesus macaques?

Despite significant advances, several critical research gaps persist in understanding the comparative immunology of CCR3 between humans and rhesus macaques. First, comprehensive comparative mapping of CCR3 expression patterns across tissue types and immune cell subsets between species remains incomplete. While expression in major immune cells has been documented, differences in tissue-specific expression or in rare cell populations could significantly impact translational research. Development of species-specific antibodies and probes would enable more precise comparative expression mapping across tissues.

Second, the regulation of CCR3 expression under different inflammatory conditions shows species-specific variations that are incompletely characterized. Comparative analysis of CCR3 promoter regions and transcription factor binding sites between humans and macaques would provide insights into evolutionary conservation of regulatory mechanisms. Epigenetic factors influencing CCR3 expression, including DNA methylation patterns and histone modifications, remain largely unexplored in macaques compared to humans.

Third, while structural similarities between human and macaque CCR3 are acknowledged, fine molecular details of ligand binding pockets and signaling interfaces deserve deeper investigation. Comparative analysis using techniques like hydrogen-deuterium exchange mass spectrometry or cryo-electron microscopy could reveal subtle structural differences that impact drug binding or signaling outcomes. Additionally, systematic comparison of CCR3 post-translational modifications between species, including patterns of glycosylation, phosphorylation, and sulfation, would illuminate potential functional differences.

Finally, comprehensive comparison of CCR3 genetic diversity within human and macaque populations remains a significant gap. While copy number variations of chemokine genes have been documented in both species , the extent of CCR3 allelic variation and its functional consequences across different macaque subpopulations relative to human diversity patterns requires further investigation. Addressing these research gaps would substantially enhance the translational value of rhesus macaque models for CCR3-related immunological research.

How should researchers prioritize future directions in Macaca mulatta CCR3 research given current knowledge gaps?

Researchers should prioritize future Macaca mulatta CCR3 investigations based on both knowledge gaps and translational potential, focusing on several key areas. First, comprehensive characterization of CCR3 genetic diversity across different macaque populations should be prioritized, as population-specific genetic backgrounds significantly impact disease susceptibility and progression . This should include both copy number variation analysis and single nucleotide polymorphism (SNP) identification to create a complete genetic landscape of CCR3 variation. Such data would provide essential context for interpreting experimental results across different macaque subpopulations.

Second, functional genomics approaches integrating transcriptomic and proteomic data should be employed to elucidate the dynamic regulation of CCR3 expression in response to various immunological challenges. Following the successful methodology used in radiation response studies , longitudinal sampling before and after infection or inflammatory stimuli would reveal temporal patterns of CCR3 regulation. This approach should incorporate analysis of various tissue compartments beyond peripheral blood to capture tissue-specific regulation patterns.

Third, development of improved tools for CCR3 detection and manipulation in macaque systems deserves significant investment. This includes creation of species-specific antibodies, CRISPR/Cas9 genome editing protocols optimized for macaque cells, and improved recombinant expression systems for functional studies. Finally, translational studies directly comparing CCR3-targeted therapeutic approaches between macaque models and human systems should be prioritized to validate the predictive value of macaque models for human applications. By addressing these priorities, researchers will substantially advance both basic understanding of CCR3 biology and its translational applications in human disease.

What technological advances would most significantly enhance research capabilities in studying Macaca mulatta CCR3?

Several technological advances would substantially enhance research capabilities for studying Macaca mulatta CCR3, addressing current methodological limitations. First, development of single-cell multiomics technologies optimized for macaque samples would enable unprecedented resolution of CCR3 expression patterns. Combining single-cell RNA sequencing with simultaneous protein detection (CITE-seq) and chromatin accessibility analysis (ATAC-seq) in the same cells would reveal cell type-specific regulation patterns and functional heterogeneity. These approaches should be adapted specifically for macaque samples, with appropriate antibody panels and analysis pipelines optimized for the Macaca mulatta genome.

Second, advanced genetic manipulation technologies for rhesus macaques would revolutionize functional studies. While CRISPR/Cas9 technology has been applied to macaque embryos, development of conditional and tissue-specific gene editing systems for adult macaques would enable precise manipulation of CCR3 expression in specific contexts. Similarly, advanced viral vector systems for tissue-specific gene delivery would facilitate both overexpression and knockdown studies in adult animals without requiring germline modification.

Third, improved imaging technologies for tracking CCR3-expressing cells in vivo would provide critical insights into cell trafficking and tissue localization. Development of macaque-specific PET imaging ligands targeting CCR3 would enable non-invasive tracking of receptor expression during disease progression. Similarly, intravital multiphoton microscopy techniques optimized for deeper tissue penetration would allow real-time visualization of CCR3-mediated cellular interactions in living tissues.

Finally, advanced computational methods specifically designed for cross-species comparative analysis would enhance translational research. Machine learning algorithms trained on integrated human and macaque datasets could identify conserved and divergent features of CCR3 biology, improving prediction of cross-species translatability. Development of these technological capabilities would collectively transform research on Macaca mulatta CCR3, accelerating both basic discoveries and translational applications.

What is the recommended protocol for cloning and expressing the Macaca mulatta CCR3 gene for functional studies?

The recommended protocol for cloning and expressing Macaca mulatta CCR3 gene involves multiple steps from gene isolation to functional validation. Initially, total RNA should be isolated from appropriate macaque tissues known to express CCR3, such as peripheral blood mononuclear cells (PBMCs). For enhanced CCR3 expression, PBMCs can be stimulated with Concanavalin A (Con A) or through mismatched allogeneic antigen stimulation, approaches that have successfully increased expression of other immune genes in macaque cells .

From isolated RNA, cDNA synthesis should be performed using oligo(dT) primers and reverse transcriptase. The CCR3 coding sequence should then be amplified using high-fidelity polymerase and primers designed based on the reference sequence (UniProt P56483), with appropriate restriction sites added for subsequent cloning. The amplified product should be verified by sequencing to confirm the absence of mutations before proceeding to expression vector construction.

For bacterial expression, the following approach has proven effective with similar macaque proteins: The verified CCR3 sequence encoding the mature protein (amino acids 1-355) should be cloned into a prokaryotic expression vector containing an appropriate fusion tag (such as His, GST, or MBP) to enhance solubility. Expression in E. coli BL21(DE3) or similar strains should be conducted at reduced temperatures (16-18°C) after IPTG induction to minimize inclusion body formation . The fusion protein can then be purified using affinity chromatography, followed by tag removal using specific proteases if required for downstream applications.

For mammalian expression, which may better preserve native protein folding and post-translational modifications, the CCR3 sequence should be cloned into vectors with strong promoters (CMV) and appropriate signal sequences. Transfection into HEK293 or CHO cells typically yields functional receptor expression, which can be verified by flow cytometry using anti-CCR3 antibodies or tagged ligands. Stable cell lines can be generated through antibiotic selection for long-term studies.

What experimental design would best evaluate the impact of CCR3 genetic variations on SIV disease progression in rhesus macaques?

An optimal experimental design to evaluate CCR3 genetic variations on SIV disease progression would employ a comprehensive approach combining retrospective and prospective analyses with robust genetic characterization and clinical monitoring. The study should include a minimum of 40-60 rhesus macaques, balanced between Indian-origin and Chinese-origin animals to account for population-specific genetic effects similar to those observed with CCL3L genes . Prior to SIV infection, comprehensive genetic characterization should be performed, including CCR3 gene sequencing to identify single nucleotide polymorphisms (SNPs), copy number variation (CNV) analysis using both real-time PCR and confirmatory fluorescence in situ hybridization (FISH), and haplotype determination .

For prospective analysis, animals should be infected with a well-characterized SIV strain (such as SIVmac) using standardized viral doses and infection routes. Following infection, longitudinal monitoring should include:

• Viral load measurements at weeks 1, 2, 4, 8, 12, 24, 36, and 48 post-infection

• CD4+ T cell counts at the same timepoints

• CCR3 expression levels on various leukocyte subsets by flow cytometry

• Routine clinical examinations to assess disease progression

• Blood samples for transcriptomic analysis at key timepoints

The primary endpoint should be time to development of simian AIDS (defined by specific clinical and laboratory criteria) or a predefined survival timepoint (e.g., 18-24 months post-infection), consistent with established endpoints in similar studies . Secondary endpoints should include viral set point, rate of CD4+ T cell decline, and development of specific opportunistic infections.