HSV-2 triggers upregulation of MALAT1 in CD4+ T cells and promotes HIV latency reversal

Herpes simplex virus type 2 (HSV-2) coinfection is associated with increased HIV-1 viral loads and expanded tissue reservoirs, but the mechanisms are not well defined. HSV-2 recurrences result in an influx of activated CD4+ T cells to sites of viral replication and an increase in activated CD4+ T cells in peripheral blood. We hypothesized that HSV-2 induces changes in these cells that facilitate HIV-1 reactivation and replication and tested this hypothesis in human CD4+ T cells and 2D10 cells, a model of HIV-1 latency. HSV-2 promoted latency reversal in HSV-2-infected and bystander 2D10 cells. Bulk and single-cell RNA-Seq studies of activated primary human CD4+ T cells identified decreased expression of HIV-1 restriction factors and increased expression of transcripts including MALAT1 that could drive HIV replication in both the HSV-2-infected and bystander cells. Transfection of 2D10 cells with VP16, an HSV-2 protein that regulates transcription, significantly upregulated MALAT1 expression, decreased trimethylation of lysine 27 on histone H3 protein, and triggered HIV latency reversal. Knockout of MALAT1 from 2D10 cells abrogated the response to VP16 and reduced the response to HSV-2 infection. These results demonstrate that HSV-2 contributes to HIV-1 reactivation through diverse mechanisms, including upregulation of MALAT1 to release epigenetic silencing.

HSV-2 increases replication of HIV in human T cells

Herpes simplex virus 2 (HSV-2) infection is a major factor driving the global HIV epidemic, leading to increased HIV plasma viral loads (PVLs) and transmission. Previous studies which focused on mucosal responses cannot explain the observed effects of HSV-2 on HIV PVLs. We sought to determine mechanisms by which HSV-2 increases HIV PVLs. CD4 T cells are recruited to sites of HSV-2 lesions and HSV-2 can infect these cells. Phenotyping of CD4 cells infected with HSV-2 in vitro suggested a preference for T follicular helper cells, an HIV latent reservoir. HSV infection of latently infected Jurkat-2D10 cells resulted in a 10-fold increase in HIV ltr expression. After exposing CD4 cells from HIV+ donors to HSV-2, HIV p24 was detected only in cells expressing HSV-2 glycoprotein B (gB), a marker of productive HSV-2 infection. Bulk and single cell RNAseq on FACS-purified, HSV-infected and uninfected CD4 cells demonstrated reduced expression of HIV restriction factors in HSV+ cells; HSV exposed but uninfected cells exhibited higher expression of interferon response genes, potentially explaining their resistance to HIV reactivation. HSV+ cells exhibited increased expression of the lncRNA MALAT1, which may promote HIV reactivation through epigenetic modification, and HSV infection of 2D10 and CD4 cells led to decreased histone deacetylase activity. Transfection of 2D10 cells with HSV protein VP16 resulted in significantly increased HIV ltr and MALAT1 gene expression, and reduced epigenetic silencing marks. HIV proteins were also increased by proteomic analyses. These findings identify several mechanisms by which HSV-2 directly triggers HIV reactivation, such as the up-regulation of the lncRNA MALAT1.

Supported by grants from the NIH (R01 AI134367, T32 AI007501, T32 GM007288)

Functional Genomics of the Pediatric Obese Asthma Phenotype Reveal Enrichment of Rho-GTPase Pathways

Rationale: Obesity-related asthma disproportionately affects minority children and is associated with nonatopic T-helper type 1 (Th1) cell polarized inflammation that correlates with pulmonary function deficits. Its underlying mechanisms are poorly understood.Objectives: To use functional genomics to identify cellular mechanisms associated with nonatopic inflammation in obese minority children with asthma.Methods: CD4⁺ (cluster of differentiation 4-positive) Th cells from 59 obese Hispanic and African American children with asthma and 61 normal-weight Hispanic and African American children with asthma underwent quantification of the transcriptome and DNA methylome and genotyping. Expression and methylation quantitative trait loci revealed the contribution of genetic variation to transcription and DNA methylation. Adjusting for Th-cell subtype proportions discriminated loci where transcription or methylation differences were driven by differences in subtype proportions from loci that were independently associated with obesity-related asthma.Measurements and Main Results: Obese children with asthma had more memory and fewer naive Th cells than normal-weight children with asthma. Differentially expressed and methylated genes and methylation quantitative trait loci in obese children with asthma, independent of Th-cell subtype proportions, were enriched in Rho-GTPase pathways. Inhibition of CDC42 (cell division cycle 42), one of the Rho-GTPases associated with Th-cell differentiation, was associated with downregulation of the IFNγ, but not the IL-4, gene. Differential expression of the RPS27L (40S ribosomal protein S27-like) gene, part of the p53/mammalian target of rapamycin pathway, was due to nonrandom distribution of expression quantitative trait loci variants between groups. Differentially expressed and/or methylated genes, including RPS27L, were associated with pulmonary function deficits in obese children with asthma.Conclusions: We found enrichment of Rho-GTPase pathways in obese asthmatic Th cells, identifying them as a novel therapeutic target for obesity-related asthma, a disease that is suboptimally responsive to current therapies.

HVEM signaling promotes protective antibody-dependent cellular cytotoxicity (ADCC) vaccine responses to herpes simplex viruses

Herpes simplex virus (HSV) glycoprotein D (gD) not only is required for virus entry and cell-to-cell spread but also binds the host immunomodulatory molecule, HVEM, blocking interactions with its ligands. Natural infection primarily elicits neutralizing antibodies targeting gD, but subunit protein vaccines designed to induce this response have failed clinically. In contrast, preclinical studies demonstrate that an HSV-2 single-cycle strain deleted in gD, ΔgD-2, induces primarily non-neutralizing antibodies that activate Fcγ receptors (FcγRs) to mediate antibody-dependent cellular cytotoxicity (ADCC). These studies were designed to test the hypothesis that gD interferes with ADCC through engagement of HVEM. Immunization of Hvem-/- mice with ΔgD-2 resulted in significant reduction in HSV-specific IgG2 antibodies, the subclass associated with FcγR activation and ADCC, compared with wild-type controls. This translated into a parallel reduction in active and passive vaccine protection. A similar decrease in ADCC titers was observed in Hvem-/- mice vaccinated with an alternative HSV vaccine candidate (dl5-29) or an unrelated vesicular stomatitis virus-vectored vaccine. Unexpectedly, not only did passive transfer of immune serum from ΔgD-2-vaccinated Hvem-/- mice fail to protect wild-type mice but transfer of immune serum from ΔgD-2-vaccinated wild-type mice failed to protect Hvem-/- mice. Immune cells isolated from Hvem-/- mice were impaired in FcγR activation, and, conversely, addition of gD protein or anti-HVEM antibodies to in vitro murine or human FcγR activation assays inhibited the response. These findings uncover a previously unrecognized role for HVEM signaling in generating and mediating ADCC and an additional HSV immune evasion strategy.

A Single-Cycle Glycoprotein D Deletion Viral Vaccine Candidate, ΔgD-2, Elicits Polyfunctional Antibodies That Protect against Ocular Herpes Simplex Virus

Herpes simplex virus 1 (HSV-1) is a leading cause of infectious blindness, highlighting the need for effective vaccines. A single-cycle HSV-2 strain with the deletion of glycoprotein D, ΔgD-2, completely protected mice from HSV-1 and HSV-2 skin or vaginal disease and prevented latency following active or passive immunization in preclinical studies. The antibodies functioned primarily by activating Fc receptors to mediate antibody-dependent cellular cytotoxicity (ADCC). The ability of ADCC to protect the immune-privileged eye, however, may differ from skin or vaginal infections. Thus, the current studies were designed to compare active and passive immunization with ΔgD-2 versus an adjuvanted gD subunit vaccine (rgD-2) in a primary lethal ocular murine model. ΔgD-2 provided significantly greater protection than rgD-2 following a two-dose vaccine regimen, although both vaccines were protective compared to an uninfected cell lysate. However, only immune serum from ΔgD-2-vaccinated, but not rgD-2-vaccinated, mice provided significant protection against lethality in passive transfer studies. The significantly greater passive protection afforded by ΔgD-2 persisted after controlling for the total amount of HSV-specific IgG in the transferred serum. The antibodies elicited by rgD-2 had significantly higher neutralizing titers, whereas those elicited by ΔgD-2 had significantly more C1q binding and Fc gamma receptor activation, a surrogate for ADCC function. Together, the findings suggest ADCC is protective in the eye and that nonneutralizing antibodies elicited by ΔgD-2 provide greater protection than neutralizing antibodies elicited by rgD-2 against primary ocular HSV disease. The findings support advancement of vaccines, including ΔgD-2, that elicit polyfunctional antibody responses.IMPORTANCE Herpes simplex virus 1 is the leading cause of infectious corneal blindness in the United States and Europe. Developing vaccines to prevent ocular disease is challenging because the eye is a relatively immune-privileged site. In this study, we compared a single-cycle viral vaccine candidate, which is unique in that it elicits predominantly nonneutralizing antibodies that activate Fc receptors and bind complement, and a glycoprotein D subunit vaccine that elicits neutralizing but not Fc receptor-activating or complement-binding responses. Only the single-cycle vaccine provided both active and passive protection against a lethal ocular challenge. These findings greatly expand our understanding of the types of immune responses needed to protect the eye and will inform future prophylactic and therapeutic strategies.

HSV-2 infects T follicular helper cells to promote HIV reactivation

HSV-2 is one of the most significant factors fueling the global HIV epidemic and coinfection is associated with higher HIV plasma viral loads and increased rates of HIV transmission and HSV-2 recurrences. The mechanisms underlying this syndemic likely reflect local and systemic effects. To explore potential systemic effects, we characterized PBMC from a cohort of HIV-1+ women who were or were not HSV-2 seropositive (HSV-2+) and identified phenotypic changes in CD4 T cells including increased frequencies of activated cells and cells expressing co-receptors for HIV entry in HIV+/HSV-2+ vs. HIV+/HSV-2 seronegative (HSV-2−) women. Surprisingly, IL-32, a proinflammatory cytokine, was lower in CD4 T cells from HSV-2+ women. Addition of IL-32γ to CD4 T cells from HIV+ women blocked HIV reactivation following stimulation with phytohemagglutinin, suggesting that HSV-2 induces phenotypic changes in CD4 T cells to promote HIV reactivation. Subsequent RNAseq analysis of CD4 T cells infected ex vivo with HSV-2 also showed lower levels of IL-32, as well as elevated bcl6, itch, and irf4 transcripts along with decreased ccr7, psgl1, and s1pr1, suggesting a transcriptional landscape consistent with T follicular helper (TFH) cells. Flow cytometry studies using CD4 T cells isolated from PBMC from HIV− or HIV+ donors, as well as from tonsils, showed an increased frequency of TFH cells in HSV-2 infected CD4 T cells, suggesting preferential infection of this subpopulation, which is known to harbor latent HIV. HSV-2 infection of CD4 T cells isolated from HIV+ donors or latently infected T cell lines triggered HIV reactivation. These findings demonstrate that HSV-2 directly infects CD4 T cell subpopulations including TFH cells to promote HIV reactivation.

Murine Model of Maternal Immunization Demonstrates Protective Role for Antibodies That Mediate Antibody-Dependent Cellular Cytotoxicity in Protecting Neonates From Herpes Simplex Virus Type 1 and Type 2

BACKGROUND

Neonatal herpes simplex virus (HSV) disease results in unacceptable morbidity and mortality. The primary humoral immune response to natural infection is neutralizing antibodies (Abs). However, Abs that activate Fc gama receptors (FcγRs) and mediate antibody-dependent cell-mediated cytotoxicity (ADCC) may play a dominant role in protection. In adult mice, a single-cycle HSV candidate vaccine deleted in glycoprotein-D (ΔgD-2) that induces ADCC provided complete protection against HSV disease and prevented the establishment of latency. Passive transfer studies showed that Abs were sufficient for protection. The current study tested the hypothesis that maternal immunization with ΔgD-2 would protect neonates.

METHODS

C57BL/6 female mice were vaccinated 3 weeks apart with ΔgD-2, and pups were challenged at different times postnatally with lethal doses of HSV-1 or HSV-2. Concentration and functionality of Abs and immune cells were assessed.

RESULTS

Maternal ΔgD-2 immunization provided significant protection and reduced viral dissemination after lethal challenge with HSV-1 or HSV-2. Protection correlated with Abs acquired transplacentally or from breastmilk that mediated ADCC. Protection was reduced when pups were challenged on Day 1 of life, and this was associated with decreased ability of newborn cells to mediate Ab-dependent cell killing.

CONCLUSIONS

Antibodies mediating ADCC provide significant protection against neonatal HSV.

Escherichia coli K1 utilizes host macropinocytic pathways for invasion of brain microvascular endothelial cells

Eukaryotic cells utilize multiple endocytic pathways for specific uptake of ligands or molecules, and these pathways are commonly hijacked by pathogens to enable host cell invasion. Escherichia coli K1, a pathogenic bacterium that causes neonatal meningitis, invades the endothelium of the blood-brain barrier, but the entry route remains unclear. Here, we demonstrate that the bacteria trigger an actin-mediated uptake route, stimulating fluid phase uptake, membrane ruffling and macropinocytosis. The route of uptake requires intact lipid rafts as shown by cholesterol depletion. Using a variety of perturbants we demonstrate that small Rho GTPases and their downstream effectors have a significant effect on bacterial invasion. Furthermore, clathrin-mediated endocytosis appears to play an indirect role in E. coli K1 uptake. The data suggest that the bacteria effect a complex interplay between the Rho GTPases to increase their chances of uptake by macropinocytosis into human brain microvascular endothelial cells.

Pneumococcal neuraminidase activates TGF-β signalling

Neuraminidase A (NanA) is an important virulence factor that is anchored to the pneumococcal cell wall and cleaves sialic acid on host substrates. We noted that a secreted allele of NanA was over-represented in invasive pneumococcal isolates and promoted the development of meningitis when swapped into the genome of non-meningitis isolates replacing cell wall-anchored NanA. Both forms of recombinant NanA directly activated transforming growth factor (TGF)-β, increased SMAD signalling and promoted loss of endothelial tight junction ZO-1. However, in assays using whole bacteria, only the cell-bound NanA decreased expression of ZO-1 and showed NanA dependence of bacterial invasion of endothelial cells. We conclude that NanA secretion versus retention on the cell surface does not influence neurotropism of clinical isolates. However, we describe a new NanA-TGF-β signalling axis that leads to decreased blood-brain barrier integrity and enhances bacterial invasion.

Bacterial Peptidoglycan Traverses the Placenta to Induce Fetal Neuroproliferation and Aberrant Postnatal Behavior

Maternal infection during pregnancy is associated with adverse outcomes for the fetus, including postnatal cognitive disorders. However, the underlying mechanisms are obscure. We find that bacterial cell wall peptidoglycan (CW), a universal PAMP for TLR2, traverses the murine placenta into the developing fetal brain. In contrast to adults, CW-exposed fetal brains did not show any signs of inflammation or neuronal death. Instead, the neuronal transcription factor FoxG1 was induced, and neuroproliferation leading to a 50% greater density of neurons in the cortical plate was observed. Bacterial infection of pregnant dams, followed by antibiotic treatment, which releases CW, yielded the same result. Neuroproliferation required TLR2 and was recapitulated in vitro with fetal neuronal precursor cells and TLR2/6, but not TLR2/1, ligands. The fetal neuroproliferative response correlated with abnormal cognitive behavior in CW-exposed pups following birth. Thus, the bacterial CW-TLR2 signaling axis affects fetal neurodevelopment and may underlie postnatal cognitive disorders.

Exogenous remodeling of lung resident macrophages protects against infectious consequences of bone marrow-suppressive chemotherapy

Infection is the single greatest threat to survival during cancer chemotherapy because of depletion of bone marrow-derived immune cells. Phagocytes, especially neutrophils, are key effectors in immunity to extracellular pathogens, which has limited the development of new approaches to protect patients with cancer and chemotherapy-induced neutropenia. Using a model of vaccine-induced protection against lethal Pseudomonas aeruginosa pneumonia in the setting of chemotherapy-induced neutropenia, we found a population of resident lung macrophages in the immunized lung that mediated protection in the absence of neutrophils, bone marrow-derived monocytes, or antibodies. These vaccine-induced macrophages (ViMs) expanded after immunization, locally proliferated, and were closely related to alveolar macrophages (AMs) by surface phenotype and gene expression profiles. By contrast to AMs, numbers of ViMs were stable through chemotherapy, showed enhanced phagocytic activity, and prolonged survival of neutropenic mice from lethal P. aeruginosa pneumonia upon intratracheal adoptive transfer. Thus, induction of ViMs by tissue macrophage remodeling may become a framework for new strategies to activate immune-mediated reserves against infection in immunocompromised hosts.

Preparation of Purified Gram-positive Bacterial Cell Wall and Detection in Placenta and Fetal Tissues

Cell wall is a complex biopolymer on the surface of all Gram-positive bacteria. During infection, cell wall is recognized by the innate immune receptor Toll-like receptor 2 causing intense inflammation and tissue damage. In animal models, cell wall traffics from the blood stream to many organs in the body, including brain, heart, placenta and fetus. This protocol describes how to prepare purified cell wall from Streptococcus pneumoniae, detect its distribution in animal tissues, and study the tissue response using the placenta and fetal brain as examples.

Escherichia coli K1 invasion of human brain microvascular endothelial cells

The pathogenic Escherichia coli strain E. coli K1 is a primary causative agent of neonatal meningitis. Understanding how these bacteria cross the blood-brain barrier is vital to develop therapeutics. Here, we describe the use of live-cell imaging techniques to study E. coli K1 interactions with cellular markers following infection of human brain microvascular endothelial cells, a model system of the blood-brain barrier. We also discuss optimization of endothelial cell transfection conditions using nonviral transfection technique, bacterial labeling techniques, and in vitro assays to screen for fluorescent bacteria that retain their ability to invade host cells.

Possible roles of phospholipase A(2) in the biological activities of Acanthamoeba castellanii (T4 Genotype)

Using phospholipases A(2)-specific spectrophotometric assays, it was shown thatA. castellaniilysates and their conditioned medium exhibit phospholipase activities. The extracellular levels of PLA(2)detected were significantly reduced compared with the cell-associated enzyme (P<0.05). Sphinganine, a PLA(2)inhibitor showed robust amoebistatic properties but had no effect on the viability ofA. castellanii. The potency of sphinganine was demonstrated effectively towards purified PLA(2)derived from porcine pancreas. Using sphinganine, it was observed that PLA(2)is involved in neither binding nor cytotoxicity of the human brain microvascular endothelial cells due toA. castellanii. Unlike as was the case forDictyosteliumamoebae, PLA(2)appeared to be involved inA. castellaniiphagocytosis of the fluorescently-labelled polystyrene beads. Horseradish peroxidase was used as a tracer molecule to develop assays to study pinocytosis inA. castellanii. The findings revealed that sphinganine impedes phagocytosis but augments pinocytosis inA. castellaniisuggesting distinct nature of processes. A complete understanding of the role of phospholipases in the biology and pathogenesis ofA. castellaniiinfections will determine their potential as therapeutic targets.

The effect of neem (Azadirachta indica) extract and dietary selenium on distribution of selenium in hepatocarcinogenesis induced rat

Neem, Azadirachta indica, is a plant from the family Meliaceae, known as "Pokok Semambu" in Malay community. It has been extensively used in India as traditional Ayurvedic and folklore minedicine for the treatment of various diseases. This study aimed to determine the distribution of selenium in the liver of rats during hepatocarcinogenesis when neem aqueous extract and dietary selenium was supplemented.