MCMV Infection Research Articles

Abstract A035: Infection of primary mammary fibroblasts with cytomegalovirus coordinately increases autotaxin-lysophosphatidate-inflammatory signaling, which could increase breast cancer metastasis

Abstract Background: Metastatic breast cancer is the most prevalent cause of mortality by cancer-related deaths in women. Our group showed that the 63% of Canadian breast cancer patients who were infected with CMV were 5.6-times more likely to develop Stage IV cancers with reduced relapse-free survival. Also, the metastatic phenotype of breast tumors and the number and sizes of lung metastases were increased in mice with latent infections. Fibroblasts are important sites of CMV infection. Cancer-associated fibroblasts (CAFs) are also major sites of autotaxin (ATX) secretion in breast tumors, whereas ATX production and CMV infection in breast cancer cells is negligible. ATX produces lysophosphatidate (LPA), which increases inflammatory cytokine production that stimulates further ATX secretion in a feedforward cycle. LPA promotes breast tumor growth and metastasis by signaling through six G protein-coupled receptors. Signaling is terminated by lipid phosphate phosphatases (LPPs)-1 and -3, which degrade LPA and are decreased in breast tumors. Hypothesis: Breast cancer metastasis could be increased by active CMV infection of CAFs through increased inflammation and LPA signaling. Results: Quiescent fibroblasts isolated and cultured from mammary tissue of non-tumor bearing mice (n>3) produced negligible quantities of ATX. LPA signaling was coordinately promoted in these primary fibroblasts infected for 48 h with 1 MOI of mouse CMV (n=3) with a 5-fold increase in mRNA for ATX (p=0.008), increased mRNAs for LPA2,3,4 receptors (p<0.05) and decreased mRNA expressions for LPP1 and LPP3 (p<0.05). An increase in the secretion of granulocyte monocyte-colony stimulating factor of 548 pg/ml (p=0.01) and Interleukin-6 by 8307 pg/ml (p=0.03) was observed post infection (n=5), thus creating a pro-inflammatory environment. Increased mRNA expression of fibroblast markers, including alpha-smooth muscle actin (p=0.005), fibroblast-associated protein (p=0.007), epidermal growth factor receptor (EGFR) (p=0.001) and transforming growth factor- ß receptor 1 (TGF-ßR1) (p=0.03) was also observed post-infection (n=3). The results were analyzed by student’s t-test. Assessment of these factors in breast cancer patients (n=1100) using the Tumor Immune Estimation Resource Analysis showed a positive correlation in the expression of EGFR and TGF-ßR1 with the LPA3,4 receptors (p<0.05). Conclusion: The changes in expression of ATX, LPA receptors and LPPs in CMV- infected fibroblasts are consistent with increased metastasis. Our results show that mCMV infection of primary mammary fibroblasts dramatically reprograms them to express CAF-like properties and promotes ATX-LPA-inflammatory signaling. CAFs are a major constituent of the tumor stroma. They promote tumor progression by secreting factors such as ATX, which increases metastasis, fibrosis and favors immunosuppression. Our results support the use of pharmacological agents to block signaling by the ATX-LPA-inflammatory cycle to treat breast and other cancers, especially for the majority of patients who are infected with CMV. Citation Format: Humayara Khan, Xiaoyun Tang, Frank Wuest, David N. Brindley, Denise G. Hemmings. Infection of primary mammary fibroblasts with cytomegalovirus coordinately increases autotaxin-lysophosphatidate-inflammatory signaling, which could increase breast cancer metastasis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A035.

Pgam1 Regulate Adaptive NK Cells in Anti-Viral and Anti-Tumor Response

Natural killer (NK) cells are the innate immune cells that play a role in the anti-viral infections and tumor cells. The adaptive NK cells are characterized with expression of the HLA-E-specific CD94/NKG2C activating receptor. The reconstitution of NKG2C+ adaptive NK cells post HSCT is much faster in NKG2C homozygous(NKG2C wt/wt) donors than NKG2C heterozygous donors (NKG2C wt/del), which resulted in lower incidence of CMV infection. In this study, we aimed to find out the mainly regulators of adaptive NK cells between NKG2C wt/wt and NKG2C wt/del donors. RNA-sequencing analysis were performed. Results shown that NK cells from NKG2C wt/wt donors constant upregulated glycolysis and biosynthesis-related genes, while downregulated in TGF-beta signaling and FOXO signaling pathway(Figure A and B). In order to determine the role of glycolysis in adaptive NK cells, upregulated glycolysis related genes were assessed by q-PCR, and PGAM1 is considered as the most important gene in the expansion of adaptive NK cells(Figure C). PGAM1 is upregulated upon NK cells stimulation via cytokine or target cells, which is related to the CD107a expression. HKB99 is an allosteric inhibitor for PGAM1, which is considered as a potential therapeutic target for many cancers nowadays. NK cells were added with HKB99 in vitro for 12h hours to evaluate the anti-K562 function. After that, Glycolysis is inhibited with the decreasing of ECAR while the OCR is not affected (FigureD). The adding of PGAM1 inhibitor resulted in decreasing of CD107a expression in NK cells, especially in the adaptive NK cells. NK cells activation signaling pathway is also inhibited, including the phosphorylation of mTORC1 protein S6, Syk, zap70, and the PLC-gamma. The PI3K/AKT is inhibited after the PGAM1 inhibition. After that,supplementation of pyruvate is efficient to rescue the inhibition caused by PGAM1 inhibitor. 5mM pyruvate adding can restore the cytokine release of NK cells and the phosphorylation of S6 and syk/zap70(Figure E). PGAM1-NCR-cre mice was constructed in which PGAM1 is knock out in NK cells specifically. In KO group, the ratio of NK cells and the maturation of NK cells are decreased. Upon cytokine stimulation, the activator receptors expression is less in KO mice. Besides, PGAM1 deficiency NK cells exhibited glucose uptake deficiency and disadvantages in proliferation both in vivo and in vitro (Figure F). The differentiation (CD11b+CD27-) and activation marker (DNAM1, Ly49H) are decreased in the competing transplantation mouse model, while the exhaustion markers such as PD-1 and NKG2A is upregulated. Further, MCMV infection models shown that PGAM1 deficiency mice with lower ratio of Ly49H+ adaptive NK cells at the early stage of infection, while Ly49G2 and Ly49C+ cells are not affected(Figure G). Further, Ly49H+ adaptive NK cells shown less expression of Ki67 in PB-NK cells, with the activating markers CD25 is decreased. Higher MCMV load induced inflammation is occurred in PGAM1 deficiency NK cells. Anti-tumor effect was also evaluated. The apoptosis of YAC-1 cells is decrease in coincidence with CD107a expression decreasing. MLL-AF9 leukemia mice model shown in day 18, the Ly49H+ adaptive NK cells in PGAM1 deficiency mice is less than WT mice, and the tumor burden is higher and accompanied with shorter survival under tumor circumstances(Figure H). RNA seq analysis shown compared to WT mice, the downregulated genes in PGAM1 deficiency NK cells are enriched in leukocyte activation and innate immune response also interfered the cytokine-mediated signaling pathway. At last, we monitored expression of PGAM1 and the function of NK cells in patients whose CMV is reactive post HSCT. PGAM1 is elevated post CMV infection, which is correlated with CD107a secretion. ROC curve suggests that PGAM1 may act as a predictor for refractory recurrence CMV infection in patients post HSCT(Figure I). In summary, our studies shown the glycolysis is effectively support the faster adaptive NK cells expansion and CMV response. PGAM1-mediated glycolysis is significant for NK cells anti-tumor and anti-viral function.

The TNFα/TNFR2 axis mediates natural killer cell proliferation by promoting aerobic glycolysis

Natural killer (NK) cells are predominant innate lymphocytes that initiate the early immune response during infection. NK cells undergo a metabolic switch to fuel augmented proliferation and activation following infection. Tumor necrosis factor-alpha (TNFα) is a well-known inflammatory cytokine that enhances NK cell function; however, the mechanism underlying NK cell proliferation in response to TNFα is not well established. Here, we demonstrated that upon infection/inflammation, NK cells upregulate the expression of TNF receptor 2 (TNFR2), which is associated with increased proliferation, metabolic activity, and effector function. Notably, IL-18 can induce TNFR2 expression in NK cells, augmenting their sensitivity toward TNFα. Mechanistically, TNFα-TNFR2 signaling upregulates the expression of CD25 (IL-2Rα) and nutrient transporters in NK cells, leading to a metabolic switch toward aerobic glycolysis. Transcriptomic analysis revealed significantly reduced expression levels of genes involved in cellular metabolism and proliferation in NK cells from TNFR2 KO mice. Accordingly, our data affirmed that genetic ablation of TNFR2 curtails CD25 upregulation and TNFα-induced glycolysis, leading to impaired NK cell proliferation and antiviral function during MCMV infection in vivo. Collectively, our results delineate the crucial role of the TNFα-TNFR2 axis in NK cell proliferation, glycolysis, and effector function.

Two developmental pathways generate functionally distinct populations of natural killer cells

Abstract Natural killer (NK) cells function by eliminating virus-infected cells or tumor cells during early defenses. However, the early development of NK cells and lineage relationships between NK cells and helper innate lymphoid cells (ILCs) remain elusive. Common precursors for ILCs (ILCPs) can differentiate into both helper ILCs and NK cells. Here, we identified a NK lineage-restricted progenitor population, early NK progenitor (ENKP), which does not develop from ILCPs, thus ENKP may represent the ILCP-independent pathway of NK cell development. Competitive chimera experiment shows ENKPs generate NK cells more efficiently than ILCPs, suggesting that ENKP-dependent pathway is the major pathway for NK cell development. scRNA-seq shows ENKP-derived NK cells express Ly49 receptors and higher levels of cytotoxic genes whereas ILCP-derived NK cells have very low expression of Ly49 receptors and express higher levels of genes implicated in tissue residency such as CD69 and CD200R. Furthermore, Ly49H+ NK cells which response to MCMV infection mostly develop from ENKPs but not ILCPs. Consistently, ENKP-derived NK cells but not ILCP-derived NK cells expanded dramatically after MCMV infection. Our findings establish the existence of two pathways of NK cell development that generate functionally distinct NK cell subsets.

Altered epithelial function in the stria vascularis and hearing loss in a mouse model of congenital cytomegalovirus infection associated hearing loss

Abstract Congenital Human Cytomegalovirus (HCMV) infection is a leading cause of sensorineural hearing loss (SNHL) in children. The mechanism of HCMV damage to the developing auditory system that leads to SNHL is not understood and effective treatments are lacking. We developed a murine model of HCMV infection that results in neurodevelopmental abnormalities and SNHL, thus providing a useful model to study the mechanisms of SNHL associated with cCMV infection. We have shown that MCMV induces expression of proinflammatory molecules and immune cell activation in the cochlea associated with histopathologic changes and SNHL. The stria vascularis (SV) plays a critical role in hearing by; (1) maintaining an epithelial barrier needed for generation of the high electrical potential of endocochlear fluid surrounding the hair cells; (2) expression of a system of ion channels that create a high K +concentration in the endocochlear fluid; and (3) generation of a blood labyrinth barrier (BLB) that surrounds the vasculature in the SV and functions like the blood brain barrier. Utilizing several assays, our studies showed that MCMV infection altered each of these functions. The transcription and protein expression in the SV required for tight junctions in the epithelial barrier and ion channels were decreased early after infection and in SV from infected mice with SNHL compared to those without SNHL. In addition, the resident macrophages that contribute to the BLB had altered phenotypes. Functionally, penetration of a cell-impermeable tracer into the SV could be demonstrated in MCMV infected mice. In all, our data show that MCMV dysregulates expression of key proteins in the SV that in turn impact the capacity of the SV to maintain the cochlea’s unique environment.

Systemic Cancer Immunostimulatory Therapies and Acute Viral Infection Induce Corticosteroid-Mediated Thymic Involution and Naïve T cell Output in Mice and Humans

Abstract Thymic involution (TI) occurs with aging and during stress responses, decreasing naïve T cell output. Thymic progenitor apoptosis can occur directly by corticosteroids (CS) leading to transient involution followed by recovery. The effects of systemic immunotherapies (IT) used in cancer or immune stimulation via acute viral infection on the thymus has not been well-characterized and was the primary goal of this study. IT treatment of mice with high dose IL-2 (HD IL-2) or models of acute viral infection (mouse cytomegalovirus, MCMV) all resulted in rapid TI due to apoptosis of CD4/CD8 double-positive progenitors followed with a reduction in naïve T cell content. Interestingly, cessation of therapy or resolution of viral infection resulted in greater thymic size compared to untreated recipients, indicating a rebound effect. In both models, increased CS levels in the serum of mice preceded TI. Clinically, patients receiving HD IL-2 for cancer had significantly reduced T cell receptor excision circles, a marker for naïve T cell output, also correlating with increased cortisol levels. Using a model of sub-lethal MCMV infection that did not increase systemic pro-inflammatory cytokines, we observed a similar correlation of TI and increased CS levels. To further analyze the effects of CS on TI, mice were adrenalectomized and then given HD IL-2, where significantly reduced CS levels correlated with partial protection from TI. These results indicate that strong systemic immunostimulation by either IT or acute viral infections markedly induce transient CS-mediated TI, leading to a decrease in naïve T cells. Therefore, targeting CS responses in preventing TI and, especially with the aged, allow for naïve T cell populations to be maintained.

415.6: Exploring Cell-Specific Mechanisms of Ischemia/Reperfusion Injury Mediated Reactivation of Cytomegalovirus From Latency in the Orthotopic Mouse Lung Transplantation

Purpose: Cytomegalovirus (CMV) is the most common opportunistic infection in lung transplant recipients, with the highest risk seen in CMV seronegative recipients (R-) of seropositive organs (D+). This study aims to explore key molecular pathways responsible for transplant-mediated CMV reactivation by using single-cell RNA sequencing (scRNA-seq) in a mouse model of syngeneic D+/R- lung transplantation. Methods: Left lungs from naïve (D-) mice or MCMV latently infected (D+) mice were transplanted to syngeneic R- recipients, while the contralateral right lungs served as controls. Lung tissues from the transplants at day 2 post-transplant (POD) or controls were harvested for viral RNA analysis and single cell isolation. CD31+ and CD45+ enriched single cell suspensions were processed using 10X Genomics, followed by sequencing. The sequenced data were processed using Cell Ranger pipeline and Seurat. Additional transplants were treated with small molecule Myd88 inhibitor to determine whether innate immunity plays a role in transplant induced CMV reactivation. Results: MCMV IE-1 mRNA transcripts were significantly upregulated at POD 2, but were not detectable in the controls, indicating that transcriptional activation is induced in the early phase of transplant and ischemia/reperfusion (I/R) injury associated with the transplant procedures is an important contributing factor. In addition, viral DNA amplification was detected in the salivary glands of D+/R- recipients at POD14, confirming that transplant of a D+ graft results in viral reactivation and dissemination. These data support the mouse lung transplant model as a viable approach to study mechanisms of CMV reactivation. Data from scRNAseq analysis showed distinct lung and immune cell clusters in lung transplants and controls. There were minimal differences in transcriptome landscapes between D- and D+ lungs prior to transplant (controls). In contrast, the differences were prominent between lungs from D-/R- transplant vs D+/R- lung grafts in the myeloid populations [e.g. neutrophils, macrophages (Macs)] and endothelial cells. Gene expression of Macs showed more differences between transplant lungs and control lungs than any endothelial cells or neutrophils. Pathway analysis of differentially expressed genes for myeloid cell types showed several significant immune response pathways including MIF regulation of innate immunity and communication between innate and adaptive immune cells. Expression of Myd88 and c-fos were increased in the lung grafts regardless of latent MCMV infection. Furthermore, our preliminary study using a Myd88 inhibitor showed a trend of CMV viral load reduction in lung grafts. Conclusions: Early I/R injury following lung transplant resulted significant alterations of transcriptome landscape unique to different cell types. Myd88/AP-1 plays a critical role in CMV reactivation; thus targeting Myd88 has a great therapeutic potential to prevent I/R injury-mediated CMV reactivation. NIH NIAID R21AI163876. NIH/NIAID P01AI112522.

UTX is an epigenetic regulator of natural killer cell development and anti-viral effector function.

Abstract Natural killer (NK) cells are circulating type 1 innate lymphocytes that protect against viral infection and cancer. While it is now clear that NK cells display distinct epigenetic states during development and activation, the factors that control the epigenetic programming of NK cells during these processes are not well understood. Here, we show that the H3K27me3 histone demethylase UTX epigenetically regulates NK cells in a cell-intrinsic and demethylase-independent manner by regulating the chromatin accessibility of gene loci involved in homeostasis and effector function. As a consequence, mice with NK cell-specific UTX deficiency displayed an increase in peripheral immature NK cell cells that express higher levels of Bcl-2. Furthermore, UTX-deficient NK cells produce lower amounts of interferon (IFN)-γ and Granzyme B following MCMV infection, resulting in increased mortality. These findings reveal UTX as an essential regulator of NK cell homeostatic and effector epigenetic programs. M.I.C. is supported by Ruth L. Kirschstein National Research Service Awards (GM007185 and AI007323), and Whitcome Fellowship from the Molecular Biology Institute at UCLA.

Novel mouse model of MCMV-induced adaptive NK cells

Abstract NK cells are important mediators of viral control with the capacity to form adaptive immune features following infection. However, studies of infection-induced adaptive NK cells require adoptive cell transfer to lower the precursor frequency of ‘antigen-specific’ NK cells, potentially limiting the diversity of the NK cell response. In seeking an unmanipulated model to probe the adaptive NK cells, we interrogated a wide range of Collaborative Cross (CC) inbred mice, inbred mouse strains which exhibit broad genetic diversity across strains. Our assessment identified and validated a putative ‘ideal’ CC strain, CC006, which does not require manipulation to generate and maintain adaptive NK cells. Critically, CC006 mice, in contrast to C57Bl/6 mice, are capable of developing enhanced NK cell-mediated protective responses to MCMV infection following m157-mediated vaccination. This work both furthers our understanding of adaptive NK cells and demonstrates the utility of CC mice in the development and interrogation of immunologic models. Supported by T32AI007511 (IJJ), T32AI007485 (IJJ), 5R01AI114543 (VPB), 1R35GM134880 (VPB), U01-AI150680 (DLF)

Chronic Vaccine Boost Prolongs Malaria Vaccine Immunity and CD4 Effector and Memory T cells

Abstract Vaccines to persistent parasite infections have been challenging to develop, and current iterations lack long-term protection. Persistent infection generates effector and effector memory T cells (Teff, Tem), and both contribute to protection, as we recently showed for Plasmodium infection. Sterilizing immunity from live P. chabaudi vaccination lasts less than 200 days. While specific antibody levels remain stable after the acute phase of infection, the decay of T cells corresponds with loss of protection from re-infection. Chronic vaccination with CMV has been shown to generate Tem and Teff, and so we tested MCMV for the ability to prolong protection to P. chabaudi. We generated MCMV encoding P. chabaudi MSP-1 epitope B5 (MCMV-B5), and used B5 TCR Transgenic CD4 T cells to follow the MCMV-B5 response. We showed that boosting the live malaria vaccine with MCMV-B5: i) prolonged vaccine protection to heterologous infection at day 200, ii) increased parasite-specific T cells and promoted a highly-differentiated Teff phenotype, including iii) IFN-γ+ and TNF+ T cells. Importantly, chronic MCMV infection itself improved protection from P. chabaudi infection and promoted generation of a T cell phenotype similar to P. chabaudi infection. Investigating the mechanisms of MCMV in prolonged vaccine-induced protection, we found an impressive role for IFN-γ, as its neutralization in vivo during MCMV latency is associated with loss of protection to P. chabaudi challenge. Blocking IFN-γ before challenge induced fewer Teff and less plasma IL-12 upon P. chabaudi challenge. Our findings suggest a mechanism to boost CD4 T cell immunity using chronic vaccines, which may be broadly applicable to infections that require T cell based immunity. Supported by R01AI135061

Maize miR167-ARF3/30-polyamine oxidase 1 module-regulated H2O2 production confers resistance to maize chlorotic mottle virus.

Maize chlorotic mottle virus (MCMV) is the key pathogen causing maize lethal necrosis (MLN). Due to the sharply increased incidence of MLN in many countries, there is an urgent need to identify resistant lines and uncover the underlying resistance mechanism. Here, we showed that the abundance of maize (Zea mays) microR167 (Zma-miR167) positively modulates the degree of resistance to MCMV. Zma-miR167 directly targets Auxin Response Factor3 (ZmARF3) and ZmARF30, both of which negatively regulate resistance to MCMV. RNA-sequencing coupled with gene expression assays revealed that both ZmARF3 and ZmARF30 directly bind the promoter of Polyamine Oxidase 1 (ZmPAO1) and activate its expression. Knockdown or inhibition of enzymatic activity of ZmPAO1 suppressed MCMV infection. Nevertheless, MCMV-encoded p31 protein directly targets ZmPAO1 and enhances the enzyme activity to counteract Zma-miR167-mediated defense to some degree. We uncovered a role of the Zma-miR167-ZmARF3/30 module for restricting MCMV infection by regulating ZmPAO1 expression, while MCMV employs p31 to counteract this defense.

DOP46 Metabolic adaptation to ER stress licences STING signalling in intestinal epithelial cells

Abstract Background Chronic endoplasmic reticulum stress (ER) in the intestinal epithelium is a pathophysiological hallmark of IBD. cGAS/STING is an innate immune pathway involved in the detection of double stranded DNA fragments leading to the subsequent induction of type I IFN responses. We here tested the hypothesis that chronic ER stress impairs cGAS/STING signalling in the intestinal epithelium. Methods Mice with a conditional intestinal epithelial deletion of Xbp1 (Xbp1 ΔIEC, Xbp1fl/fl) were used to assess intestinal epithelial STING expression in-vivo. Small intestinal organoids (Xbp1ΔIEC, Xbp1fl/fl) and cell lines (Mode K, iCtrl and iXbp1) were used to assess cGAS/STING signalling in-vitro using STING agonist (dsDNA, DMXAA). Murine cytomegalovirus (mCMV) infection assays were performed in iCtrl and iXbp1cells and Xbp1ΔIEC, Xbp1fl/fl mice to functionally link impaired cGAS/STING to pathogen response. LC-MS profiling was performed in iCtrl and iXbp1cells to identify underlying metabolic programs affecting cGAS/STING responses in ER-stressed cells. IBD biopsy samples (cross-sectional, longitudinal therapy response cohort) were used to validate key molecular phenotypes in human IBD. Results Compared to Xbp1 fl/fl mice, Xbp1ΔIEC show completely abrogated STING expression in the basal crypt compartment of the small intestinal epithelium. In line with that iXbp1 ModeK cells displayed impaired pathway activation (TBK1) and interferon inducible gene expression (Cxcl10) in response to cGAS/STING stimulation and towards mCMV infection, leading to increased viral replication compared to iCtrl cells. In-vivo mCMV infection led to augmented small intestinal histopathological disease activity in Xbp1ΔIEC, but not Xbp1fl/fl mice. Using LC-MS, we show that ER-stress induces a metabolic adaptation towards increased serin/glycin metabolism, which is used to counterbalance reactive oxygen species (ROS) via glutathione (GSH) synthesis. Pharmacological interception of key pathways of GSH synthesis of deprivation of serin/glycin phenocopies ER-stress in abrogating STING signalling in IECs. Lastly, we show that key aspects of metabolic adaptation to ER-stress are present in intestinal biopsies of IBD patients. Conclusion Our data describe a novel mechanism of metabolic adaptation to compensate ER-stress and maintain intestinal epithelial cGAS/STING signalling. We therefore put forward a model of ER-stress driven immunodeficiency via cGAS/STING signalling which renders the intestinal mucosa susceptible towards CMV infection in the context of IBD.

NanoString evaluation of murine Cytomegalovirus transcription in vivo and in vitro

BackgroundNext Generation Sequencing allows for deep analysis of transcriptional activity in cells and tissues, however it is still a cost intensive method that demands well versed data handling. Reverse transcription quantitative PCR (RT-qPCR) is the most commonly used method to measure gene expression levels, however the information gathered is quite small in comparison to NGS. A newer method called nanoString allows for highly multiplexed gene expression analysis by detecting mRNAs without the use of enzymes for reverse transcription or amplification even for single cells or low input material. The method can be done in 1.5 days and data are quickly analyzed by the accompanied user friendly software.Our aim was to investigate this new method and compare it to the existing alternatives, while investigating murine Cytomegalovirus (mCMV) infection and latency. MethodsmCMV infected murine embryonic fibroblasts (MEF), lung and salivary glands from BALB/c mice were evaluated at different stages of infection. A set of 30 custom designed nanoString probes were tested, 20 probes specific for mCMV genes, 6 probes for host genes known to be influenced by viral infection and 4 reference gene specific probes. nanoString counts were compared to published RNA-Seq RPKM. ResultsWe found that nanoString can be used for analysis of cytomegalovirus gene expression during acute infection in vitro and in vivo, both for virus specific and host genes. Although some transcripts show different expression rates in comparison to NGS data, the most abundant transcripts are comparable. When tissues are infected, there are significantly fewer transcripts than in MEFs, and consistent with previous work there are significant differences in relevant abundance between MEF and tissues. We were unable to detect our viral transcripts of interest in latently infected tissue. ConclusionsFor viruses with annotated transcriptomes, nanoString allows simultaneous quantitation of multiple virus and host genes. One huge advantage of the platform is rapid turnaround and simplicity of analysis. It should prove to be very useful to explore host virus interactions during acute infection, but it is unclear if it has adequate sensitivity for analysis during latency in immunocompetent mice.

Natural killer cells and dendritic epidermal γδ T cells orchestrate type 1 conventional DC spatiotemporal repositioning toward CD8+ T cells

SummarySuccessful immune responses rely on a regulated delivery of the right signals to the right cells at the right time. Here we show that natural killer (NK) and dendritic epidermal γδ T cells (DETCs) use similar mechanisms to spatiotemporally orchestrate conventional type 1 dendritic cell (cDC1) functions in the spleen, skin, and its draining lymph nodes (dLNs). Upon MCMV infection in the spleen, cDC1 clusterize with activated NK cells in marginal zones. This XCR1-dependent repositioning of cDC1 toward NK cells allows contact delivery of IL-12 and IL-15/IL-15Rα by cDC1, which is critical for NK cell responses. NK cells deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) to cDC1, guiding their CCR7-dependent relocalization into the T cell zone. In MCMV-infected skin, XCL1-secreting DETCs promote cDC1 migration from the skin to the dLNs. This XCR1-dependent licensing of cDC1 both in the spleen and skin accelerates antiviral CD8+ T cell responses, revealing an additional mechanism through which cDC1 bridge innate and adaptive immunity.

Siglec-H-Deficient Mice Show Enhanced Type I IFN Responses, but Do Not Develop Autoimmunity After Influenza or LCMV Infections.

Siglec-H is a DAP12-associated receptor on plasmacytoid dendritic cells (pDCs) and microglia. Siglec-H inhibits TLR9-induced IFN-α production by pDCs. Previously, it was found that Siglec-H-deficient mice develop a lupus-like severe autoimmune disease after persistent murine cytomegalovirus (mCMV) infection. This was due to enhanced type I interferon responses, including IFN-α. Here we examined, whether other virus infections can also induce autoimmunity in Siglec-H-deficient mice. To this end we infected Siglec-H-deficient mice with influenza virus or with Lymphocytic Choriomeningitis virus (LCMV) clone 13. With both types of viruses we did not observe induction of autoimmune disease in Siglec-H-deficient mice. This can be explained by the fact that both types of viruses are ssRNA viruses that engage TLR7, rather than TLR9. Also, Influenza causes an acute infection that is rapidly cleared and the chronicity of LCMV clone 13 may not be sufficient and may rather suppress pDC functions. Siglec-H inhibited exclusively TLR-9 driven type I interferon responses, but did not affect type II or type III interferon production by pDCs. Siglec-H-deficient pDCs showed impaired Hck expression, which is a Src-family kinase expressed in myeloid cells, and downmodulation of the chemokine receptor CCR9, that has important functions for pDCs. Accordingly, Siglec-H-deficient pDCs showed impaired migration towards the CCR9 ligand CCL25. Furthermore, autoimmune-related genes such as Klk1 and DNase1l3 are downregulated in Siglec-H-deficient pDCs as well. From these findings we conclude that Siglec-H controls TLR-9-dependent, but not TLR-7 dependent inflammatory responses after virus infections and regulates chemokine responsiveness of pDCs.

Therapeutic Vaccination of Hematopoietic Cell Transplantation Recipients Improves Protective CD8 T-Cell Immunotherapy of Cytomegalovirus Infection.

Reactivation of latent cytomegalovirus (CMV) endangers the therapeutic success of hematopoietic cell transplantation (HCT) in tumor patients due to cytopathogenic virus spread that leads to organ manifestations of CMV disease, to interstitial pneumonia in particular. In cases of virus variants that are refractory to standard antiviral pharmacotherapy, immunotherapy by adoptive cell transfer (ACT) of virus-specific CD8+ T cells is the last resort to bridge the “protection gap” between hematoablative conditioning for HCT and endogenous reconstitution of antiviral immunity. We have used the well-established mouse model of CD8+ T-cell immunotherapy by ACT in a setting of experimental HCT and murine CMV (mCMV) infection to pursue the concept of improving the efficacy of ACT by therapeutic vaccination (TherVac) post-HCT. TherVac aims at restimulation and expansion of limited numbers of transferred antiviral CD8+ T cells within the recipient. Syngeneic HCT was performed with C57BL/6 mice as donors and recipients. Recipients were infected with recombinant mCMV (mCMV-SIINFEKL) that expresses antigenic peptide SIINFEKL presented to CD8+ T cells by the MHC class-I molecule Kb. ACT was performed with transgenic OT-I CD8+ T cells expressing a T-cell receptor specific for SIINFEKL-Kb. Recombinant human CMV dense bodies (DB-SIINFEKL), engineered to contain SIINFEKL within tegument protein pUL83/pp65, served for vaccination. DBs were chosen as they represent non-infectious, enveloped, and thus fusion-competent subviral particles capable of activating dendritic cells and delivering antigens directly into the cytosol for processing and presentation in the MHC class-I pathway. One set of our experiments documents the power of vaccination with DBs in protecting the immunocompetent host against a challenge infection. A further set of experiments revealed a significant improvement of antiviral control in HCT recipients by combining ACT with TherVac. In both settings, the benefit from vaccination with DBs proved to be strictly epitope-specific. The capacity to protect was lost when DBs included the peptide sequence SIINFEKA lacking immunogenicity and antigenicity due to C-terminal residue point mutation L8A, which prevents efficient proteasomal peptide processing and binding to Kb. Our preclinical research data thus provide an argument for using pre-emptive TherVac to enhance antiviral protection by ACT in HCT recipients with diagnosed CMV reactivation.

MyD88 is an essential regulator of NK cell-mediated clearance of MCMV infection

The signaling adapter MyD88 is critical for immune cell activation in response to viral or bacterial pathogens via several TLRs, IL-1βR and IL-18R. However, the essential role of MyD88 during activations mediated by germline-encoded NK cell receptors (NKRs), such as Ly49H or NKG2D, has yet to be investigated. To define the NK cell-intrinsic function of MyD88, we generated a novel NK cell conditional knockout mouse for MyD88 (Myd88fl/flNcr1Cre/+). Phenotypic characterization of these mice demonstrated that MyD88 is dispensable for NK cell development and maturation. However, the MyD88-deficient NK cells exhibited significantly reduced cytotoxic potentials in vivo. In addition, the lack of MyD88 significantly reduced the NKG2D-mediated inflammatory cytokine production in vitro. Consistent with this, mice lacking MyD88 were unable to respond and clear MCMV infection. Transcriptomic analyses of splenic NK cells following MCMV infection revealed that inflammatory gene signatures were upregulated in Ly49H+. In contrast, Ly49H− NK cells have significant enrichment in G2M checkpoint genes, revealing distinct transcriptomic profiles of these subsets. Our results identify a central role for MyD88 in Ly49H-dependent gene signatures, including alterations in genes regulating proliferation in Ly49H+ NK cells. In summary, our study reveals a previously unknown function of MyD88 in Ly49H-dependent signaling and in vivo functions of NK cells.

Expression of Nutrient Transporters on NK Cells During Murine Cytomegalovirus Infection Is MyD88-Dependent.

Natural killer (NK) cells are the predominant innate lymphocytes that provide early defense against infections. In the inflammatory milieu, NK cells modify their metabolism to support high energy demands required for their proliferation, activation, and functional plasticity. This metabolic reprogramming is usually accompanied by the upregulation of nutrient transporter expression on the cell surface, leading to increased nutrient uptake required for intense proliferation. The interleukin-1 family members of inflammatory cytokines are critical in activating NK cells during infection; however, their underlying mechanism in NK cell metabolism is not fully elucidated. Previously, we have shown that IL-18 upregulates the expression of solute carrier transmembrane proteins and thereby induces a robust metabolic boost in NK cells. Unexpectedly, we found that IL-18 signaling is dispensable during viral infection in vivo, while the upregulation of nutrient transporters is primarily MyD88-dependent. NK cells from Myd88-/- mice displayed significantly reduced surface expression of nutrient receptors and mTOR activity during MCMV infection. We also identified that IL-33, another cytokine employing MyD88 signaling, induces the expression of nutrient transporters but requires a pre-exposure to IL-12. Moreover, signaling through the NK cell activating receptor, Ly49H, can also promote the expression of nutrient transporters. Collectively, our findings revealed multiple pathways that can induce the expression of nutrient transporters on NK cells while highlighting the imperative role of MyD88 in NK cell metabolism during infection.

The Anti-apoptotic Murine Cytomegalovirus Protein vMIA-m38.5 Induces Mast Cell Degranulation.

Mast cells (MC) represent “inbetweeners” of the immune system in that they are part of innate immunity by acting as first-line sentinels for environmental antigens but also provide a link to adaptive immunity by secretion of chemokines that recruit CD8 T cells to organ sites of infection. An interrelationship between MC and cytomegalovirus (CMV) has been a blank area in science until recently when the murine model revealed a role for MC in the resolution of pulmonary infection by murine CMV (mCMV). As to the mechanism, MC were identified as a target cell type of mCMV. Infected MC degranulate and synthesize the CC-chemokine ligand-5 (CCL-5), which is released to attract protective virus-specific CD8 T cells to infected host tissue for confining and eventually resolving the productive, cytopathogenic infection. In a step forward in our understanding of how mCMV infection of MC triggers their degranulation, we document here a critical role for the mCMV m38.5 gene product, a mitochondria-localized inhibitor of apoptosis (vMIA). We show an involvement of mCMV vMIA-m38.5 in MC degranulation by two reciprocal approaches: first, by enhanced degranulation after m38.5 gene transfection of bone marrow-derived cell culture-grown MC (BMMC) and, second, by reduced degranulation of MC in peritoneal exudate cell populations infected ex corpore or in corpore with mutant virus mCMV-Δm38.5. These studies thus reveal a so far unknown function of mCMV vMIA-m38.5 and offer a previously unconsidered but biologically relevant cell system for further analyzing functional analogies between vMIAs of different CMV species.

Metabolic but not transcriptional regulation by PKM2 is important for natural killer cell responses.

Natural Killer (NK) cells have an important role in immune responses to viruses and tumours. Integrating changes in signal transduction pathways and cellular metabolism is essential for effective NK cells responses. The glycolytic enzyme Pyruvate Kinase Muscle 2 (PKM2) has described roles in regulating glycolytic flux and signal transduction, particularly gene transcription. While PKM2 expression is robustly induced in activated NK cells, mice lacking PKM2 in NK cells showed no defect in NK cell metabolism, transcription or antiviral responses to MCMV infection. NK cell metabolism was maintained due to compensatory PKM1 expression in PKM2-null NK cells. To further investigate the role of PKM2, we used TEPP-46, which increases PKM2 catalytic activity while inhibiting any PKM2 signalling functions. NK cells activated with TEPP-46 had reduced effector function due to TEPP-46-induced increases in oxidative stress. Overall, PKM2-regulated glycolytic metabolism and redox status, not transcriptional control, facilitate optimal NK cells responses.