IL 16 Rhesus Macaque
Description
Biological Functions and Mechanisms of Action
IL-16 binds the CD4 receptor, inducing chemotaxis in CD4+ T cells, monocytes, and eosinophils . Key roles include:
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Suppression of HIV replication: Blocks viral propagation via CD4 receptor interference .
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Immune regulation: Inhibits T-cell receptor (TCR)/CD3-mediated activation and promotes IL-2Rα expression on T cells .
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Proinflammatory modulation: Enhances macrophage and dendritic cell recruitment during infections .
HIV/SIV Studies
IL-16’s ability to suppress HIV replication has made it a focus in simian immunodeficiency virus (SIV) models. Its homology to human IL-16 allows direct insights into:
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Mechanisms of viral reservoir persistence in lymphoid tissues .
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Combinatorial therapies with cytokines like IL-21 or IFNα to enhance NK cell antiviral activity .
Immunotherapy Development
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T-cell modulation: IL-16’s inhibition of TCR activation suggests utility in autoimmune or hyperinflammatory conditions .
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Vaccine adjuvants: Potential to enhance CD4+ T-cell responses in mucosal vaccines .
Production and Purification
Recombinant rhesus IL-16 is generated via E. coli expression systems, followed by:
Comparative Analysis with Human and Murine IL-16
| Feature | Rhesus IL-16 | Human IL-16 | Murine IL-16 |
|---|---|---|---|
| Amino Acid Identity | 100% | 95% | 85% |
| CD4 Binding Efficiency | High | High | Moderate |
| HIV/SIV Suppression | Demonstrated | Demonstrated | Limited |
This high conservation underscores its utility in modeling human immune responses .
Experimental Findings in Primate Models
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SIV/HIV suppression: IL-16 reduced viral loads in lymphoid tissues by enhancing CD8+ T-cell and NK cell activity .
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Cytokine synergy: Combined with IL-21 or IFNα, IL-16 amplified antiviral NK cell differentiation, mimicking nonpathogenic SIV control in African green monkeys .
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Neuroinflammation: IL-6 upregulation during acute SIV infection correlated with IL-16-mediated microglial activation, suggesting neuroprotective roles .
Challenges and Future Directions
While IL-16 shows therapeutic promise, barriers include:
Product Specs
Q&A
What is IL-16 and what are its primary functions in rhesus macaques?
IL-16 is a pro-inflammatory cytokine that functions primarily as a chemoattractant for CD4+ T cells in rhesus macaques. Research has demonstrated that IL-16 has potent capabilities for inducing chemotaxis in rhesus macaque immune cells (p < 0.05), suggesting its importance in immune cell trafficking and inflammatory responses . Additionally, IL-16 has been shown to inhibit Simian Immunodeficiency Virus (SIV) mRNA transcription, thereby reducing viral replication in infected rhesus macaque cells . The functionality of recombinant rhesus macaque IL-16 (rrIL-16) includes marked inhibition of mixed lymphocyte response (MLR) at approximately 73 ± 0.6% (p < 0.05) in both rhesus and human cell systems, indicating its immunomodulatory properties .
How does rhesus macaque IL-16 compare structurally to human IL-16?
Sequence comparison analysis reveals that recombinant rhesus macaque IL-16 (rrIL-16) shares over 97% amino acid identity with human IL-16 . This high degree of conservation suggests that the structure and function of IL-16 have been largely preserved across primate evolution. This remarkable similarity also explains the cross-reactivity observed in bioassays, where rrIL-16 demonstrates functionality in human cell systems . The high homology between rhesus and human IL-16 makes the rhesus macaque an appropriate model for studying IL-16-mediated processes that may be applicable to human immunology and disease.
What experimental models utilize rhesus macaques for IL-16 research?
The primary experimental models utilizing rhesus macaques for IL-16 research include:
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SIV infection models: Rhesus macaques are susceptible to SIV infection, making them valuable for studying the antiviral effects of IL-16. Specifically, both SIVmac251 (dual-tropic virus) and SIVmac239 (T-tropic virus) models are employed to evaluate IL-16's suppressive effects on viral replication .
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Chronic enterocolitis models: While not specifically focused on IL-16, these models examine broader cytokine networks in rhesus macaques with intestinal inflammation, providing context for understanding IL-16's role within the larger cytokine environment .
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Genetic diversity models: Indian-origin rhesus macaques with known genetic backgrounds are used to study how genetic variation might influence IL-16 expression and function .
What techniques are used to measure IL-16 activity in rhesus macaque studies?
Multiple sophisticated methodologies are employed to measure IL-16 activity in rhesus macaque studies:
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Chemotaxis assays: Quantitative measurement of immune cell migration in response to IL-16 concentration gradients. Studies have demonstrated significant chemotactic responses (p < 0.05) in rhesus macaque immune cells exposed to recombinant IL-16 .
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Mixed Lymphocyte Response (MLR) inhibition assays: These measure IL-16's ability to suppress T-cell proliferation in response to allogeneic stimuli. Research has demonstrated that rrIL-16 can inhibit MLR by 73 ± 0.6% (p < 0.05) .
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Viral suppression assays: These assess IL-16's antiviral effects by measuring p27 antigen production in SIV-infected peripheral blood mononuclear cells (PBMCs). Data shows that rrIL-16 can reduce p27 antigen production by up to 70% in SIVmac251-infected cultures and up to 96% in SIVmac239-infected cultures .
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Confocal microscopy techniques: While not specifically used for IL-16 in the search results, advanced imaging techniques have been developed to visualize cytokine-producing cells in situ in rhesus macaque tissues, enabling simultaneous visualization of multiple extra- and intracellular antigens at high resolution .
How does IL-16 impact SIV replication in rhesus macaques?
IL-16 demonstrates significant antiviral activity against SIV in rhesus macaque models through multiple mechanisms:
| SIV Strain | Cell Tropism | IL-16 Source | Reduction in p27 Antigen | Statistical Significance |
|---|---|---|---|---|
| SIVmac251 | Dual-tropic (T cells and monocyte/macrophages) | Rhesus macaque (rrIL-16) | Up to 70% | p < 0.05 |
| SIVmac251 | Dual-tropic (T cells and monocyte/macrophages) | Sooty mangabey (rmIL-16) | Up to 70% | p < 0.01 |
| SIVmac239 | T-tropic (primarily T cells) | Rhesus macaque (rrIL-16) | 96% | Not specified |
| SIVmac239 | T-tropic (primarily T cells) | Sooty mangabey (rmIL-16) | 100% | Not specified |
The primary mechanism of action appears to be inhibition of SIV mRNA transcription, which prevents viral replication within infected cells . This effect is observed with both rrIL-16 (from disease-susceptible rhesus macaques) and rmIL-16 (from disease-resistant sooty mangabeys), although with varying degrees of efficacy depending on the viral strain used .
How do genetic differences between rhesus macaque populations affect IL-16 function?
Rhesus macaques display remarkable genetic diversity, with levels of single nucleotide polymorphisms (SNPs) approximately twice as high as those observed in most human populations . This genetic variation may influence IL-16 function in several ways:
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Population differences: Chinese-origin and Indian-origin rhesus macaques show differences in disease pathogenesis, blood chemistry, major histocompatibility complex, and behavioral traits . While not specifically studied for IL-16, these population differences likely extend to cytokine networks including IL-16.
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Genotype-phenotype relationships: The high genetic diversity of rhesus macaques provides an opportunity to map functional genetic variation to phenotypic differences in immune responses, potentially including IL-16 activity . Research utilizing three-generation pedigrees of Indian-origin rhesus macaques with whole-genome sequencing data allows for investigating genetic influences on cytokine function .
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MHC variation: Differences in major histocompatibility complex alleles between rhesus macaque populations may influence IL-16 function through altered T-cell responses, given IL-16's role in CD4+ T-cell chemotaxis and immune modulation .
What contradictory findings exist in IL-16 rhesus macaque research?
While the search results don't explicitly mention contradictory findings specific to IL-16 in rhesus macaques, several research challenges can be identified:
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Efficacy discrepancies: There appears to be differential efficacy of IL-16 against different SIV strains, with higher suppression of T-tropic SIVmac239 (96-100%) compared to dual-tropic SIVmac251 (up to 70%) . This suggests strain-specific mechanisms that require further investigation.
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Source-dependent effects: IL-16 from disease-resistant sooty mangabeys (rmIL-16) shows slightly different efficacy profiles compared to IL-16 from disease-susceptible rhesus macaques (rrIL-16), despite high sequence homology . Understanding these subtle functional differences remains a challenge.
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Integration with broader cytokine networks: The complex interplay between IL-16 and other cytokines in the context of SIV infection requires further elucidation, particularly given findings about Th17 cells and IL-2 in SIV pathogenesis .
How does the pre-existing immune environment affect IL-16 function in SIV infection?
The pre-existing immune environment significantly influences SIV infection outcomes in rhesus macaques, which likely impacts IL-16 function:
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Th17 cell compartment: Research has demonstrated that SIV replication in infected rhesus macaques is limited by the size of the pre-existing Th17 cell compartment. Animals with a higher representation of these cells prior to infection experienced viral loads approximately one log unit lower than those with fewer Th17 cells .
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Regulatory T cell balance: The ratio between Th17 cells and CD3+CD4+CD25+CD127low regulatory T cells (Tregs) influences viral replication dynamics. Treatment with IL-2 and granulocyte colony stimulating factor (G-CSF) before infection leads to depletion of Th17 cells, reduction of the Th17/Treg ratio, and higher viral loads for six months after infection .
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IL-16 and T cell subsets: Given IL-16's role in CD4+ T cell chemotaxis and immune modulation, its function is likely influenced by the pre-existing distribution and activation state of various T cell subsets, including Th17 cells and Tregs .
What advanced genetic approaches are being applied to IL-16 research in rhesus macaques?
Cutting-edge genetic approaches being applied to cytokine research in rhesus macaques include:
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Whole-genome sequencing: Analysis of genomic data from multi-generation pedigrees enables identification of genetic variants that may influence cytokine expression and function .
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SNP mapping: With exceptionally high levels of SNPs compared to other model organisms, rhesus macaques provide opportunities for mapping genotype-phenotype relationships related to immune function .
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Quality control methodologies: Advanced bioinformatic approaches including adapter sequence marking, repeat-masked reference assembly mapping, duplicate marking, multiple sequence realignments around insertions/deletions, and base quality score recalibration are being employed to improve the quality of genetic data in rhesus macaque research .
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Comparative genomics: Comparison of genetic sequences between disease-susceptible rhesus macaques and disease-resistant sooty mangabeys provides insights into potential genetic determinants of differential immune responses, including IL-16 function .
How does rhesus macaque IL-16 research inform human immunology and HIV research?
Rhesus macaque IL-16 research has important translational implications for human immunology and HIV research:
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Structural and functional homology: The >97% amino acid identity between rhesus macaque and human IL-16 suggests that findings regarding IL-16 function in rhesus macaques may be applicable to humans .
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Cross-reactivity in bioassays: Recombinant rhesus macaque IL-16 demonstrates functionality in human cell systems, including chemotaxis induction and MLR inhibition, supporting its relevance as a model for human immunology .
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SIV as an HIV model: The ability of IL-16 to inhibit SIV mRNA transcription suggests potential parallel mechanisms in HIV infection, which could inform novel therapeutic approaches targeting IL-16 or its pathways in humans .
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Inflammatory disease models: The similarity in cytokine networks between rhesus macaques with chronic enterocolitis and humans with inflammatory bowel diseases suggests potential translational value for understanding IL-16's role in human inflammatory conditions .
What methodological advancements in rhesus macaque research can be applied to human studies?
Several methodological advancements from rhesus macaque research have potential applications in human studies:
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In situ cytokine visualization: The confocal microscopy technique developed for simultaneous visualization of multiple extra- and intracellular antigens in rhesus macaque tissues enables higher resolution than traditional light or epifluorescence microscopy and could be adapted for human tissue analysis .
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Genetic diversity analysis: Methods for analyzing the exceptionally high genetic diversity in rhesus macaques could inform approaches to understanding human genetic variation and its impact on immune function .
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Intervention studies modulating immune cell compartments: The experimental design used to alter Th17 cell compartments in rhesus macaques before SIV infection could inform similar approaches in human studies investigating the impact of pre-existing immune environments on infection outcomes .
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Recombinant cytokine production and characterization: Techniques for producing and characterizing recombinant rhesus macaque IL-16 could be applied to the development and assessment of human recombinant cytokines for therapeutic applications .
Product Science Overview
Recombinant Rhesus Macaque Interleukin-16 (rrmIL-16) is a form of IL-16 that has been produced using recombinant DNA technology. This involves inserting the gene encoding IL-16 into a host organism, such as Escherichia coli (E. coli), to produce the protein in large quantities . The recombinant protein is then purified using various chromatographic techniques to ensure high purity and biological activity .
The recombinant rhesus macaque IL-16 is a single, non-glycosylated polypeptide chain containing 121 amino acids and has a molecular weight of approximately 12.5 kDa . The amino acid sequence of rrmIL-16 shares 85% to 95% identity with human and murine IL-16, making it a valuable tool for comparative studies and research .
The protein is typically lyophilized (freeze-dried) for stability and can be reconstituted in sterile distilled water or an aqueous buffer containing 0.1% bovine serum albumin (BSA) to a concentration of 0.1-1.0 mg/mL . Upon reconstitution, the preparation is stable for up to one week at 2-8°C and for long-term storage at -20°C to -80°C .
Recombinant rhesus macaque IL-16 is fully biologically active when compared to the standard IL-16. Its biological activity is determined by a chemotaxis bioassay using human peripheral T lymphocytes, with an effective concentration range of 1.0-100 ng/mL . The protein signals through the CD4 receptor, similar to its human counterpart .
Recombinant IL-16 is used extensively in immunological research to study its role in immune responses and its potential therapeutic applications. It is particularly useful in studying the mechanisms of T-cell activation, chemotaxis, and the suppression of viral replication . Additionally, due to its high sequence identity with human IL-16, rrmIL-16 serves as a valuable model for understanding the function and regulation of IL-16 in humans .
