Liver Is a Generative Site for the B Cell Response to Ehrlichia muris.

The B cell response to Ehrlichia muris is dominated by plasmablasts (PBs), with few-if any-germinal centers (GCs), yet it generates protective immunoglobulin M (IgM) memory B cells (MBCs) that express the transcription factor T-bet and harbor V-region mutations. Because Ehrlichia prominently infects the liver, we investigated the nature of liver B cell response and that of the spleen. B cells within infected livers proliferated and underwent somatic hypermutation (SHM). Vh-region sequencing revealed trafficking of clones between the spleen and liver and often subsequent local clonal expansion and intraparenchymal localization of T-bet+ MBCs. T-bet+ MBCs expressed MBC subset markers CD80 and PD-L2. Many T-bet+ MBCs lacked CD11b or CD11c expression but had marginal zone (MZ) B cell phenotypes and colonized the splenic MZ, revealing T-bet+ MBC plasticity. Hence, liver and spleen are generative sites of B cell responses, and they include V-region mutation and result in liver MBC localization.

MyD88-dependent inflammasome activation and autophagy inhibition contributes to Ehrlichia-induced liver injury and toxic shock.

Severe hepatic inflammation is a common cause of acute liver injury following systemic infection with Ehrlichia, obligate Gram-negative intracellular bacteria that lack lipopolysaccharide (LPS). We have previously shown that type I IFN (IFN-I) and inflammasome activation are key host-pathogenic mediators that promote excessive inflammation and liver damage following fatal Ehrlichia infection. However, the underlying signals and mechanisms that regulate protective immunity and immunopathology during Ehrlichia infection are not well understood. To address this issue, we compared susceptibility to lethal Ixodes ovatus Ehrlichia (IOE) infection between wild type (WT) and MyD88-deficient (MyD88-/-) mice. We show here that MyD88-/- mice exhibited decreased inflammasome activation, attenuated liver injury, and were more resistant to lethal infection than WT mice, despite suppressed protective immunity and increased bacterial burden in the liver. MyD88-dependent inflammasome activation was also dependent on activation of the metabolic checkpoint kinase mammalian target of rapamycin complex 1 (mTORC1), inhibition of autophagic flux, and defective mitophagy in macrophages. Blocking mTORC1 signaling in infected WT mice and primary macrophages enhanced bacterial replication and attenuated inflammasome activation, suggesting autophagy promotes bacterial replication while inhibiting inflammasome activation. Finally, our data suggest TLR9 and IFN-I are upstream signaling mechanisms triggering MyD88-mediated mTORC1 and inflammasome activation in macrophages following Ehrlichia infection. This study reveals that Ehrlichia-induced liver injury and toxic shock are mediated by MyD88-dependent inflammasome activation and autophagy inhibition.

Transcription of the herpes simplex virus 1 genome during productive and quiescent infection of neuronal and nonneuronal cells.

UNLABELLED: Herpes simplex virus 1 (HSV-1) can undergo a productive infection in nonneuronal and neuronal cells such that the genes of the virus are transcribed in an ordered cascade. HSV-1 can also establish a more quiescent or latent infection in peripheral neurons, where gene expression is substantially reduced relative to that in productive infection. HSV mutants defective in multiple immediate early (IE) gene functions are highly defective for later gene expression and model some aspects of latency in vivo. We compared the expression of wild-type (wt) virus and IE gene mutants in nonneuronal cells (MRC5) and adult murine trigeminal ganglion (TG) neurons using the Illumina platform for cDNA sequencing (RNA-seq). RNA-seq analysis of wild-type virus revealed that expression of the genome mostly followed the previously established kinetics, validating the method, while highlighting variations in gene expression within individual kinetic classes. The accumulation of immediate early transcripts differed between MRC5 cells and neurons, with a greater abundance in neurons. Analysis of a mutant defective in all five IE genes (d109) showed dysregulated genome-wide low-level transcription that was more highly attenuated in MRC5 cells than in TG neurons. Furthermore, a subset of genes in d109 was more abundantly expressed over time in neurons. While the majority of the viral genome became relatively quiescent, the latency-associated transcript was specifically upregulated. Unexpectedly, other genes within repeat regions of the genome, as well as the unique genes just adjacent the repeat regions, also remained relatively active in neurons. The relative permissiveness of TG neurons to viral gene expression near the joint region is likely significant during the establishment and reactivation of latency. IMPORTANCE: During productive infection, the genes of HSV-1 are transcribed in an ordered cascade. HSV can also establish a more quiescent or latent infection in peripheral neurons. HSV mutants defective in multiple immediate early (IE) genes establish a quiescent infection that models aspects of latency in vivo. We simultaneously quantified the expression of all the HSV genes in nonneuronal and neuronal cells by RNA-seq analysis. The results for productive infection shed further light on the nature of genes and promoters of different kinetic classes. In quiescent infection, there was greater transcription across the genome in neurons than in nonneuronal cells. In particular, the transcription of the latency-associated transcript (LAT), IE genes, and genes in the unique regions adjacent to the repeats persisted in neurons. The relative activity of this region of the genome in the absence of viral activators suggests a more dynamic state for quiescent genomes persisting in neurons.

Blocking TLR7- and TLR9-mediated IFN-α production by plasmacytoid dendritic cells does not diminish immune activation in early SIV infection.

Persistent production of type I interferon (IFN) by activated plasmacytoid dendritic cells (pDC) is a leading model to explain chronic immune activation in human immunodeficiency virus (HIV) infection but direct evidence for this is lacking. We used a dual antagonist of Toll-like receptor (TLR) 7 and TLR9 to selectively inhibit responses of pDC but not other mononuclear phagocytes to viral RNA prior to and for 8 weeks following pathogenic simian immunodeficiency virus (SIV) infection of rhesus macaques. We show that pDC are major but not exclusive producers of IFN-α that rapidly become unresponsive to virus stimulation following SIV infection, whereas myeloid DC gain the capacity to produce IFN-α, albeit at low levels. pDC mediate a marked but transient IFN-α response in lymph nodes during the acute phase that is blocked by administration of TLR7 and TLR9 antagonist without impacting pDC recruitment. TLR7 and TLR9 blockade did not impact virus load or the acute IFN-α response in plasma and had minimal effect on expression of IFN-stimulated genes in both blood and lymph node. TLR7 and TLR9 blockade did not prevent activation of memory CD4+ and CD8+ T cells in blood or lymph node but led to significant increases in proliferation of both subsets in blood following SIV infection. Our findings reveal that virus-mediated activation of pDC through TLR7 and TLR9 contributes to substantial but transient IFN-α production following pathogenic SIV infection. However, the data indicate that pDC activation and IFN-α production are unlikely to be major factors in driving immune activation in early infection. Based on these findings therapeutic strategies aimed at blocking pDC function and IFN-α production may not reduce HIV-associated immunopathology.

Immuno-targeting the ectopic phosphorylation sites of PDGFRA generated by MAN2A1-FER fusion in HCC.

BACKGROUND: HCC is one of the most lethal cancers for humans. Mannosidase alpha class 2A member 1 (MAN2A1)-FER is one of the most frequent oncogenic fusion genes in HCC. In this report, we showed that MAN2A1-FER ectopically phosphorylated the extracellular domains of PDGFRA, MET, AXL, and N-cadherin. The ectopic phosphorylation of these transmembrane proteins led to the activation of their kinase activities and initiated the activation cascades of their downstream signaling molecules. METHODS: A panel of mouse monoclonal antibodies was developed to recognize the ectopic phosphorylation sites of PDGFRA. RESULTS AND CONCLUSIONS: The analyses showed that these antibodies bound to the specific phosphotyrosine epitopes in the extracellular domain of PDGFRA with high affinity and specificity. The treatment of MAN2A1-FER-positive cancer HUH7 with one of the antibodies called 2-3B-G8 led to the deactivation of cell growth signaling pathways and cell growth arrest while having minimal impact on HUH7ko cells where MAN2A1-FER expression was disrupted. The treatment of 2-3B-G8 antibody also led to a large number of cell deaths of MAN2A1-FER-positive cancer cells such as HUH7, HEPG2, SNU449, etc., while the same treatment had no impact on HUH7ko cells. When severe combined immunodeficiency mice xenografted with HEPG2 or HUH7 were treated with monomethyl auristatin E-conjugated 2-3B-G8 antibody, it slowed the progression of tumor growth, eliminated the metastasis, and reduced the mortality, in comparison with the controls. Targeting the cancer-specific ectopic phosphorylation sites of PDGFRA induced by MAN2A1-FER may hold promise as an effective treatment for liver cancer.

Therapeutic targeting at genome mutations of liver cancer by the insertion of HSV1 thymidine kinase through Cas9-mediated editing.

BACKGROUND: Liver cancer is one of the most lethal malignancies for humans. The treatment options for advanced-stage liver cancer remain limited. A new treatment is urgently needed to reduce the mortality of the disease. METHODS: In this report, we developed a technology for mutation site insertion of a suicide gene (herpes simplex virus type 1- thymidine kinase) based on type II CRISPR RNA-guided endonuclease Cas9-mediated genome editing to treat liver cancers. RESULTS: We applied the strategy to 3 different mutations: S45P mutation of catenin beta 1, chromosome breakpoint of solute carrier family 45 member 2-alpha-methylacyl-CoA racemase gene fusion, and V235G mutation of SAFB-like transcription modulator. The results showed that the herpes simplex virus type 1-thymidine kinase insertion rate at the S45P mutation site of catenin beta 1 reached 77.8%, while the insertion rates at the breakpoint of solute carrier family 45 member 2 - alpha-methylacyl-CoA racemase gene fusion were 95.1%-98.7%, and the insertion at V235G of SAFB-like transcription modulator was 51.4%. When these targeting reagents were applied to treat mouse spontaneous liver cancer induced by catenin beta 1S45P or solute carrier family 45 member 2-alpha-methylacyl-CoA racemase, the mice experienced reduced tumor burden and increased survival rate. Similar results were also obtained for the xenografted liver cancer model: Significant reduction of tumor volume, reduction of metastasis rate, and improved survival were found in mice treated with the targeting reagent, in comparison with the control-treated groups. CONCLUSIONS: Our studies suggested that mutation targeting may hold promise as a versatile and effective approach to treating liver cancers.

Hepatocyte-specific regulation of autophagy and inflammasome activation via MyD88 during lethal Ehrlichia infection.

Hepatocytes play a crucial role in host response to infection. Ehrlichia is an obligate intracellular bacterium that causes potentially life-threatening human monocytic ehrlichiosis (HME) characterized by an initial liver injury followed by sepsis and multi-organ failure. We previously showed that infection with highly virulent Ehrlichia japonica (E. japonica) induces liver damage and fatal ehrlichiosis in mice via deleterious MyD88-dependent activation of CASP11 and inhibition of autophagy in macrophage. While macrophages are major target cells for Ehrlichia, the role of hepatocytes (HCs) in ehrlichiosis remains unclear. We investigated here the role of MyD88 signaling in HCs during infection with E. japonica using primary cells from wild-type (WT) and MyD88-/- mice, along with pharmacologic inhibitors of MyD88 in a murine HC cell line. Similar to macrophages, MyD88 signaling in infected HCs led to deleterious CASP11 activation, cleavage of Gasdermin D, secretion of high mobility group box 1, IL-6 production, and inflammatory cell death, while controlling bacterial replication. Unlike macrophages, MyD88 signaling in Ehrlichia-infected HCs attenuated CASP1 activation but activated CASP3. Mechanistically, active CASP1/canonical inflammasome pathway negatively regulated the activation of CASP3 in infected MyD88-/- HCs. Further, MyD88 promoted autophagy induction in HCs, which was surprisingly associated with the activation of the mammalian target of rapamycin complex 1 (mTORC1), a known negative regulator of autophagy. Pharmacologic blocking mTORC1 activation in E. japonica-infected WT, but not infected MyD88-/- HCs, resulted in significant induction of autophagy, suggesting that MyD88 promotes autophagy during Ehrlichia infection not only in an mTORC1-indpenedent manner, but also abrogates mTORC1-mediated inhibition of autophagy in HCs. In conclusion, this study demonstrates that hepatocyte-specific regulation of autophagy and inflammasome pathway via MyD88 is distinct than MyD88 signaling in macrophages during fatal ehrlichiosis. Understanding hepatocyte-specific signaling is critical for the development of new therapeutics against liver-targeting pathogens such as Ehrlichia.

CD8+ cell depletion of SHIV89.6P-infected macaques induces CD4+ T cell proliferation that contributes to increased viral loads.

Previous studies have shown that depletion of CD8(+) cells during acute and chronic simian immunodeficiency virus (SIV) infection leads to increased viral replication, morbidity, and mortality, which have been attributed to loss of CD8(+) T cell-mediated control of SIV. However, these studies did not exclude that CD8(+) cell depletion increased homeostatic proliferation of CD4(+) T cells, resulting in increased viral targets and, therefore, viral rebound. Chronically SHIV89.6P-infected cynomolgus macaques were CD8(+) cell-depleted, and the frequency, cell number, and phenotype of CD4(+) T cells and viral infection were examined using flow cytometry and quantitative real-time PCR. The frequency and number of Ki-67-expressing CD4(+) T cells were increased with CD8(+) cell depletion. This proliferation of CD4(+) T cells occurred even in animals with no rebound of viral loads. Most of the proliferating cells were effector memory CD4(+) T cells. Plasma simian HIV (SHIV) RNA copies positively correlated with proliferating CD4(+) T cells and SHIV DNA copies in Ki-67(+) CD4(+) T cells. Although this study does not exclude an important role for virus-specific CD8(+) T cells in SIV and SHIV infection, our data suggest that homeostatic proliferation is an important contributor to increases in plasma viremia that follow CD8(+) cell depletion.

Increased IL-15 production is associated with higher susceptibility of memory CD4 T cells to simian immunodeficiency virus during acute infection.

Acute SIV infection is characterized by explosive infection of memory CD4 T cells in peripheral and mucosal tissues. Interestingly, relatively few memory CD4 T cells are infected until as late as days 7-8 after challenge. However, by day 10 postinfection, most of the memory CD4 T cells are infected and carry viral DNA. The rapidity with which infection expands within 2-3 days to encompass virtually the entire memory CD4 T cell compartment suggests significant alterations in the susceptibility of memory CD4 T cells to infection during this period. The mechanism(s) underlying this increased permissiveness to infection is not known. In this study, we show that IL-15 secretion significantly correlates with the up-regulated expression of CD4 on memory CD4 T cells that is associated with increased permissiveness to SIV infection. Activation and proliferation of memory CD8, but not memory CD4 T cells, preceded the amplification of viral infection. Although memory CD4 T cells did not express normal activation markers, they displayed a significant up-regulation in the density of CD4 but not CCR5 expression between days 7 and 10 postinfection that correlated with increased plasma IL-15 levels and infection in these cells. Culture of purified CD4 T cells with IL-15 and/or SIV was associated with a significant increase in the expression of CD4 and infection of these sorted cells. Our results demonstrate that IL-15 contributes to the increased susceptibility of memory CD4 T cells to SIV during the early phase of acute SIV infection.

Interferon Type I Regulates Inflammasome Activation and High Mobility Group Box 1 Translocation in Hepatocytes During Ehrlichia-Induced Acute Liver Injury.

Inflammasomes are an important innate immune host defense against intracellular microbial infection. Activation of inflammasomes by microbial or host ligands results in cleavage of caspase-1 (canonical pathway) or caspase-11 (noncanonical pathway), release of interleukin (IL)-1ß, IL-18, high mobility group box 1 (HMGB1), and inflammatory cell death known as pyroptosis. Ehrlichia are obligate, intracellular, gram-negative bacteria that lack lipopolysaccharide but cause potentially life-threatening monocytic ehrlichiosis in humans and mice that is characterized by liver injury followed by sepsis and multiorgan failure. Employing murine models of mild and fatal ehrlichiosis caused by infection with mildly and highly virulent Ehrlichia muris (EM) and Ixodes ovatus Ehrlichia (IOE), respectively, we have previously shown that IOE infection triggers type I interferon (IFN-I) response and deleterious caspase-11 activation in liver tissues, which promotes liver injury and sepsis. In this study, we examined the contribution of IFN-I signaling in hepatocytes (HCs) to Ehrlichia-induced liver injury. Compared to EM infection, we found that IOE enter and replicate in vitro cultured primary murine HCs and induce secretion of IFNß and several chemokines, including regulated upon activation, normal T-cell expressed, and secreted (RANTES), monocyte chemoattractant protein 1 (MCP1), monokine induced by gamma (MIG)/chemokine (C-X-C motif) ligand 9 (CXCL9), macrophage inflammatory protein 1 alpha (MIP1α), keratinocyte-derived chemokine (KC), and granulocyte-macrophage colony-stimulating factor (GM-CSF). Notably, in vitro stimulation of uninfected and Ehrlichia-infected HCs with recombinant IFNß triggered activation of caspase-1/11, cytosolic translocation of HMGB1, and enhanced autophagy and intracellular bacterial replication. Secretion of HMGB1 by IOE-infected HCs was dependent on caspase-11. Primary HCs from IOE- but not EM-infected mice also expressed active caspase-1/11. Conclusion: HC-specific IFN-I signaling may exacerbate liver pathology during infection with obligate intracellular Ehrlichia by promoting bacterial replication and detrimental caspase-11-mediated inflammasome activation.

Antiretroviral therapy prior to acute viral replication preserves CD4 T cells in the periphery but not in rectal mucosa during acute simian immunodeficiency virus infection.

The rectal mucosa is a major site for human immunodeficiency virus entry and CD4 T-cell depletion. The early and near-total loss of these cells from the rectal mucosa severely compromises the ability of the mucosal immune system to control various opportunistic infections. Protecting these cells from infection and destruction can delay disease progression, leading to a better long-term outcome. Here we show that effective suppression of viral infection in memory CD4 T cells from the rectal mucosa and peripheral blood to a very low level with antiretroviral therapy (ART) initiated prior to the peak of infection is associated with opposite outcomes in these tissues. A near-total loss of CD4 T cells in the rectal mucosa contrasted with preservation of most memory CD4 T cells in peripheral blood during the course of treatment. Interestingly, ART significantly reduced viral infection in memory CD4 T cells from both rectal mucosa and peripheral blood. Although early ART was of limited value in protecting the CD4 T cells in the rectal mucosa, the significant preservation of peripheral CD4 T cells could contribute to maintaining immune competence, leading to a better long-term outcome.

mTORC1-mediated polarization of M1 macrophages and their accumulation in the liver correlate with immunopathology in fatal ehrlichiosis.

A polarized macrophage response into inflammatory (M1) or regenerative/anti-inflammatory (M2) phenotypes is critical in host response to multiple intracellular bacterial infections. Ehrlichia is an obligate Gram-negative intracellular bacterium that causes human monocytic ehrlichiosis (HME): a febrile illness that may progress to fatal sepsis with multi-organ failure. We have shown that liver injury and Ehrlichia-induced sepsis occur due to dysregulated inflammation. Here, we investigated the contribution of macrophages to Ehrlichia-induced sepsis using murine models of mild and fatal ehrlichiosis. Lethally-infected mice showed accumulation of M1 macrophages (iNOS-positive) in the liver. In contrast, non-lethally infected mice showed polarization of M2 macrophages and their accumulation in peritoneum, but not in the liver. Predominance of M1 macrophages in lethally-infected mice was associated with expansion of IL-17-producing T, NK, and NKT cells. Consistent with the in vivo data, infection of bone marrow-derived macrophages (BMM) with lethal Ehrlichia polarized M0 macrophages into M1 phenotype under an mTORC1-dependent manner, while infection with non-lethal Ehrlichia polarized these cells into M2 types. This work highlights that mTORC1-mediated polarization of macrophages towards M1 phenotype may contribute to induction of pathogenic immune responses during fatal ehrlichiosis. Targeting mTORC1 pathway may provide a novel aproach for treatment of HME.

Herpes Simplex Virus-1 qPCR in the Diagnosis of Lower Respiratory Tract Infections in Organ Transplant Recipients and Critically Ill Patients.

OBJECTIVES: To determine a quantitative herpes simplex virus (HSV) DNA threshold in lower respiratory tract specimens that correlates with positive viral culture and clinical outcomes. METHODS: Bronchoalveolar lavage and bronchial wash samples from 53 HSV culture-positive and 61 culture-negative matched controls were tested using HSV-1 and HSV-2 quantitative polymerase chain reaction (qPCR). RESULTS: Median viral culture turnaround time was 21.8 days and 9.9 days for culture-negative and culture-positive specimens, respectively. Using an HSV-1 viral load threshold of 1.62 × 103 copies/mL, there was 93% agreement with viral culture. An HSV-1 viral load ≥1.3 × 104 copies/mL was associated with worse clinical outcome compared to a viral load <1.3 × 104 copies/mL (hazard ratio [HR] = 4.27, P = .017), and there was a trend of worse outcome compared to patients with undetectable HSV-1 DNA (HR = 1.60, P = .056). CONCLUSIONS: qPCR has clinical utility for rapid accurate identification of HSV-1 in lower respiratory tract specimens.

Dissecting the role of dendritic cells in simian immunodeficiency virus infection and AIDS.

Human immunodeficiency virus (HIV) infection is associated with the loss of the two principal types of dendritic cell (DC), myeloid DC (mDC) and plasmacytoid DC (pDC), but the mechanism of this loss and its relationship to AIDS pathogenesis remain ill-defined. The nonhuman primate is a powerful model to dissect this response for several reasons. Both DC subsets have been well characterized in nonhuman primates and shown to have strikingly similar phenotypic and functional characteristics to their counterparts in the human. Moreover, decline of mDC and pDC occurs in rhesus macaques with end-stage simian immunodeficiency virus (SIV) infection, the model of HIV infection in humans. In this brief review, we discuss what is known about DC subsets in pathogenic and nonpathogenic nonhuman primate models of HIV infection and highlight the advances and controversies that currently exist in the field.