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BACKGROUND: The aryl hydrocarbon receptor repressor (AhRR) is known to repress aryl hydrocarbon receptor (AhR) signaling, but very little is known regarding the role of the AhRR in vivo. OBJECTIVE: This study tested the role of AhRR in vivo in AhRR overexpressing mice on molecular and toxic end points mediated through a prototypical AhR ligand. METHODS: We generated AhRR-transgenic mice (AhRR Tg) based on the genetic background of C57BL/6J wild type (wt) mice. We tested the effect of the prototypical AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the expression of cytochrome P450 (CYP)1A1 and cytokines in various tissues of mice. We next analyzed the infiltration of immune cells in adipose tissue of mice after treatment with TCDD using flow cytometry. RESULTS: AhRR Tg mice express significantly higher levels of AhRR compared to wt mice. Activation of AhR by TCDD caused a significant increase of the inflammatory cytokines Interleukin (IL)-1β, IL-6 and IL-10, and CXCL chemokines in white epididymal adipose tissue from both wt and AhRR Tg mice. However, the expression of IL-1β, CXCL2 and CXCL3 were significantly lower in AhRR Tg versus wt mice following TCDD treatment. Exposure to TCDD caused a rapid accumulation of neutrophils and macrophages in white adipose tissue of wt and AhRR Tg mice. Furthermore we found that male AhRR Tg mice were protected from high-dose TCDD-induced lethality associated with a reduced inflammatory response and liver damage as indicated by lower levels of TCDD-induced alanine aminotransferase and hepatic triglycerides. Females from both wt and AhRR Tg mice were less sensitive than male mice to acute toxicity induced by TCDD. CONCLUSION: In conclusion, the current study identifies AhRR as a previously uncharacterized regulator of specific inflammatory cytokines, which may protect from acute toxicity induced by TCDD. [ABSTRACT FROM AUTHOR]

Interindividual immune variability is driven predominantly by environmental factors, including exposure to chronic infectious agents such as cytomegalovirus (CMV). We investigated the effects of rhesus CMV (RhCMV) on composition and function of the immune system in young macaques. Within months of infection, RhCMV was associated with impressive changes in antigen presenting cells, T cells, and NK cells-and marked expansion of innate-memory CD8+ T cells. These cells express high levels of NKG2A/C and the IL-2 and IL-15 receptor beta chain, CD122. IL-15 was sufficient to drive differentiation of the cells in vitro and in vivo. Expanded NKG2A/C+CD122+CD8+ T cells in RhCMV-infected macaques, but not their NKG2-negative counterparts, were endowed with cytotoxicity against class I-deficient K562 targets and prompt IFN-γ production in response to stimulation with IL-12 and IL-18. Because RhCMV clone 68-1 forms the viral backbone of RhCMV-vectored SIV vaccines, we also investigated immune changes following administration of RhCMV 68-1-vectored SIV vaccines. These vaccines led to impressive expansion of NKG2A/C+CD8+ T cells with capacity to inhibit SIV replication ex vivo. Thus, CMV infection and CMV-vectored vaccination drive expansion of functional innate-like CD8 cells via host IL-15 production, suggesting that innate-memory expansion could be achieved by other vaccine platforms expressing IL-15. [ABSTRACT FROM AUTHOR]

"Adaptive" NK cells, characterized by FcRγ deficiency and enhanced responsiveness to Ab-bound, virus-infected cells, have been found in certain hCMV-seropositive individuals. Because humans are exposed to numerous microbes and environmental agents, specific relationships between hCMV and FcRγ-deficient NK cells (also known as g-NK cells) have been challenging to define. Here, we show that a subgroup of rhesus CMV (RhCMV)-seropositive macaques possesses FcRγ-deficient NK cells that stably persist and display a phenotype resembling human FcRγ-deficient NK cells. Moreover, these macaque NK cells resembled human FcRγ-deficient NK cells with respect to functional characteristics, including enhanced responsiveness to RhCMV-infected target in an Ab-dependent manner and hyporesponsiveness to tumor and cytokine stimulation. These cells were not detected in specific pathogen-free (SPF) macaques free of RhCMV and six other viruses; however, experimental infection of SPF animals with RhCMV strain UCD59, but not RhCMV strain 68-1 or SIV, led to induction of FcRγ-deficient NK cells. In non-SPF macaques, coinfection by RhCMV with other common viruses was associated with higher frequencies of FcRγ-deficient NK cells. These results support a causal role for specific CMV strain(s) in the induction of FcRγ-deficient NK cells and suggest that coinfection by other viruses further expands this memory-like NK cell pool., (Copyright © 2023 by The American Association of Immunologists, Inc.)

Type I interferons (IFNs) are innate cytokines with potent antiviral and immunoregulatory activities. It remains unclear how human cytomegalovirus (HCMV) can establish persistence in the face of these strongly antagonistic cytokines. In this study, we confirm that IFN-alpha efficiently suppresses the penetration of HCMV into susceptible cells, including monocytes, the major cell population in peripheral blood that is highly susceptible to HCMV infection. We further demonstrate that the HCMV-derived interleukin 10 (IL-10) homolog functions similar to cellular IL-10 and broadly inhibits TLR-induced transcriptional activation of IFN-alpha/beta genes in plasmacytoid dendritic cells (PDCs), a major type I IFN-producer in vivo that is highly resistant to HCMV infection in vitro. These results suggest that HCMV subverts innate immunity by suppressing type I IFN production of PDCs during primary viral infection via its IL-10 homolog.

The large family of human type I interferon (IFN) includes 13 distinct subtypes of IFN-alpha, all utilizing a single type I IFN receptor. Many viruses have created evasion strategies to disable this cytokine family, highlighting their importance in antiviral defense. It is unclear what advantage the presence of so many different IFN-alpha subtypes provides, but functional differences observed among individual IFN-alpha subtypes suggested that they might play distinct regulatory roles during an immune response. To determine whether IFN-alpha subtype responses differ depending on a particular type of insult and thus whether IFN-alpha subtype responses are flexible to adapt to distinct pathogen challenges, we developed a novel nested multiplex reverse transcriptase polymerase chain reaction assay with which we measured expression of all IFN-alpha subtypes by freshly isolated human plasmacytoid dendritic cells (pDCs), a main source of IFN-alpha following pathogen challenge. Collectively our data show a remarkable stability in the relative magnitude and the kinetics of induction for each IFN-alpha subtype produced by pDC. Although various stimuli used, A-, B- and C-class CpGs, live and heat-inactivated influenza viruses and the TLR7 agonist R837 affected the overall magnitude of the response, each IFN-alpha subtype was induced at statistically similar relative levels and with similar kinetics, thereby revealing a great degree of rigidity in the IFN-alpha response pattern of pDC. These data are most consistent with the induction of optimized ratios of IFN-alpha subtypes, each of which may have differing signaling properties or alternatively, a great degree of redundancy in the IFN-alpha response.

The kinetics of rhesus cytomegalovirus (RhCMV) infection were compared in primary and telomerase-immortalized (Telo-) rhesus fibroblasts (RF). Equivalent viral titers were achieved with both cell types. However, the production of infectious virions was slightly faster and plaque size was larger in Telo-RF, compared with primary cells. Comparable RhCMV growth curves and viral susceptibility were observed using Telo-RF passaged for different time periods in culture, whereas the ability of primary cells to support robust RhCMV replication declined as the cells approached senescence. Analysis of cell growth kinetics suggested that the rate of RhCMV replication was directly related to the rate of cell proliferation. RT-PCR analysis of representative RhCMV genes demonstrated that the presence of telomerase did not alter the temporal profile of RhCMV gene expression. In addition, Telo-RF cells were observed to have a significantly increased efficiency of transfection with cationic lipids, compared with primary RF. These results demonstrated that Telo-RF represents a stable, permissive cell line for RhCMV infection, facilitating standardization of in vitro assays for this important non-human primate CMV. The ease of transfection will enable molecular analyses and the generation of complementing cell lines for the propagation of defective RhCMV variants.