Human cytomegalovirus-induced immunosuppression. Relationship to tumor necrosis factor-dependent release of arachidonic acid and prostaglandin E2 in human monocytes

The elucidation of plasma lipidome profiles during severe influenza in a mouse model

Although influenza virus infection has been shown to affect lipid metabolism, details remain unknown. Therefore, we elucidated the kinetic lipid profiles of mice infected with different doses of influenza virus A/Puerto Rico/8/34 (H1N1) (PR8) by measuring multiple lipid molecular species using untargeted lipidomic analysis. C57BL/6 male mice were intranasally infected with PR8 virus at 50 or 500 plaque-forming units to cause sublethal or lethal influenza, respectively. Plasma and tissue samples were collected at 1, 3, and 6 days post-infection (dpi), and comprehensive lipidomic analysis was performed using high-performance liquid chromatography-linear trap quadrupole-Orbitrap mass spectrometry, as well as gene expression analyses. The most prominent feature of the lipid profile in lethally infected mice was the elevated plasma concentrations of phosphatidylethanolamines (PEs) containing polyunsaturated fatty acid (PUFA) at 3 dpi. Furthermore, the facilitation of PUFA-containing phospholipid production in the lungs, but not in the liver, was suggested by gene expression and lipidomic analysis of tissue samples. Given the increased plasma or serum levels of PUFA-containing PEs in patients with other viral infections, especially in severe cases, the elevation of these phospholipids in circulation could be a biomarker of infection and the severity of infectious diseases.

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

Bioactive lipid-based therapeutic approach to COVID-19 and other similar infections

COVID-19 is caused by SARS-CoV-2 infection. Epithelial and T, NK, and other immunocytes release bioactive lipids especially arachidonic acid (AA) in response to microbial infections to inactivate them and upregulate the immune system. COVID-19 (coronavirus) and other enveloped viruses including severe acute respiratory syndrome (SARS-CoV-1 of 2002-2003) and Middle East respiratory syndrome (MERS; 2012-ongoing) and hepatitis B and C (HBV and HCV) can be inactivated by AA, γ-linolenic acid (GLA, dihomo-GLA (DGLA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), which are precursors to several eicosanoids. Prostaglandin E1, lipoxin A4, resolvins, protectins and maresins enhance phagocytosis of macrophages and leukocytes to clear debris from the site(s) of infection and injury, enhance microbial clearance and wound healing to restore homeostasis. Bioactive lipids modulate the generation of M1 and M2 macrophages and the activity of other immunocytes. Mesenchymal and adipose tissue-derived stem cells secrete LXA4 and other bioactive lipids to bring about their beneficial actions in COVID-19. Bioactive lipids regulate vasomotor tone, inflammation, thrombosis, immune response, inactivate enveloped viruses, regulate T cell proliferation and secretion of cytokines, stem cell survival, proliferation and differentiation, and leukocyte and macrophage functions, JAK kinase activity and neutrophil extracellular traps and thus, have a critical role in COVID-19.

Does reactivation of cytomegalovirus contribute to severe COVID-19 disease?

The majority of people infected with SARS-CoV-2 are asymptomatic or have mild to moderate symptoms. However, for unknown reasons, about 15 % have severe pneumonia requiring hospital care and oxygen support, and about 5 % develop acute respiratory distress syndrome, septic shock, and multiorgan failure that result in a high mortality rate. The risk of severe COVID-19 is highest among those who are over 70 years of age. Why severe COVID-19 develops in some people but not others is not understood. Could some cases involve reactivation of latent cytomegalovirus (CMV)?

From conifers to cognition: Microbes, brain and behavior

A diversity of bacteria, protozoans and viruses ("endozoites") were recently uncovered within healthy tissues including the human brain. By contrast, it was already recognized a century ago that healthy plants tissues contain abundant endogenous microbes ("endophytes"). Taking endophytes as an informative precedent, we overview the nature, prevalence, and role of endozoites in mammalian tissues, centrally focusing on the brain, concluding that endozoites are ubiquitous in diverse tissues. These passengers often remain subclinical, but they are not silent. We address their routes of entry, mechanisms of persistence, tissue specificity, and potential to cause long-term behavioral changes and/or immunosuppression in mammals, where rabies virus is the exemplar. We extend the discussion to Herpesviridae, Coronaviridae, and Toxoplasma, as well as to diverse bacteria and yeasts, and debate the advantages and disadvantages that endozoite infection might afford to the host and to the ecosystem. We provide a clinical perspective in which endozoites are implicated in neurodegenerative disease, anxiety/depression, and schizophrenia. We conclude that endozoites are instrumental in the delicate balance between health and disease, including age-related brain disease, and that endozoites have played an important role in the evolution of brain function and human behavior.

Assessing Anti-HCMV Cell Mediated Immune Responses in Transplant Recipients and Healthy Controls Using a Novel Functional Assay

HCMV infection, reinfection or reactivation occurs in 60% of untreated solid organ transplant (SOT) recipients. Current clinical approaches to HCMV management include pre-emptive and prophylactic antiviral treatment strategies. The introduction of immune monitoring to better stratify patients at risk of viraemia and HCMV mediated disease could improve clinical management. Current approaches quantify T cell IFNγ responses specific for predominantly IE and pp65 proteins ex vivo, as a proxy for functional control of HCMV in vivo. However, these approaches have only a limited predictive ability. We measured the IFNγ T cell responses to an expanded panel of overlapping peptide pools specific for immunodominant HCMV proteins IE1/2, pp65, pp71, gB, UL144, and US3 in a cohort of D+R- kidney transplant recipients in a longitudinal analysis. Even with this increased antigen diversity, the results show that while all patients had detectable T cell responses, this did not correlate with control of HCMV replication in some. We wished to develop an assay that could directly measure anti-HCMV cell-mediated immunity. We evaluated three approaches, stimulation of PBMC with (i) whole HCMV lysate or (ii) a defined panel of immunodominant HCMV peptides, or (iii) fully autologous infected cells co-cultured with PBMC or isolated CD8+ T cells or NK cells. Stimulation with HCMV lysate often generated non-specific antiviral responses while stimulation with immunodominant HCMV peptide pools produced responses which were not necessarily antiviral despite strong IFNγ production. We demonstrated that IFNγ was only a minor component of secreted antiviral activity. Finally, we used an antiviral assay system to measure the effect of whole PBMC, and isolated CD8+ T cells and NK cells to control HCMV in infected autologous dermal fibroblasts. The results show that both PBMC and especially CD8+ T cells from HCMV seropositive donors have highly specific antiviral activity against HCMV. In addition, we were able to show that NK cells were also antiviral, but the level of this control was highly variable between donors and not dependant on HCMV seropositivity. Using this approach, we show that non-viraemic D+R+ SOT recipients had significant and specific antiviral activity against HCMV.

Meal for Two: Human Cytomegalovirus-Induced Activation of Cellular Metabolism

Viruses are parasites that depend on the host cell’s metabolic resources to provide the energy and molecular building blocks necessary for the production of viral progeny. It has become increasingly clear that viruses extensively modulate the cellular metabolic network to support productive infection. Here, we review the numerous ways through which human cytomegalovirus (HCMV) modulates cellular metabolism, highlighting known mechanisms of HCMV-mediated metabolic manipulation and identifying key outstanding questions that remain to be addressed.

Embolizing pulmonary aspergillosis, mycobacterial & aspergillous splenic abscess and cytomegalovirus co-infection following steroid induced immunosuppression: a case report

BACKGROUND

Aspergillosis is a serious infection particularly affecting the immunodeficient host. Its co-infection with tuberculosis and cytomegalovirus has not been reported before. Embolic events are well recognized with aspergillous endocarditis and aortitis. Splenic abscess is a rare serious complication of disseminated aspergillosis and is difficult to treat. We report the first case of multiple embolic events and splenic abscess in a patient with pulmonary aspergillosis and cytomegaloviral and tuberculous co-infection, without endocarditis or aortitis.

CASE PRESENTATION

Thirty-year-old male presented with fever and non-productive cough while on glucocorticoids for glomerulonephritis. He was found to have pulmonary aspergillosis and subsequently developed bilateral lower limb and cerebral fungal emboli and fungal abscess in the spleen. He had IgM and B cell deficiency and cytomegalovirus (CMV) and tuberculous co-infections. He recovered after prolonged course of antimicrobials, splenectomy and cessation of glucocorticoid therapy which also lead to the resolution of immune deficiencies.

CONCLUSION

This report illustrates rare combination of B and T cell suppressive effects of glucocorticoids leading to co-infections with CMV, Mycobacterium tuberculosis and Aspergillus and systemic fungal embolization from pulmonary aspergillosis.

Latent virus reactivation in astronauts on the international space station

Reactivation of latent herpes viruses was measured in 23 astronauts (18 male and 5 female) before, during, and after long-duration (up to 180 days) spaceflight onboard the international space station . Twenty age-matched and sex-matched healthy ground-based subjects were included as a control group. Blood, urine, and saliva samples were collected before, during, and after spaceflight. Saliva was analyzed for Epstein-Barr virus, varicella-zoster virus, and herpes simplex virus type 1. Urine was analyzed for cytomegalovirus. One astronaut did not shed any targeted virus in samples collected during the three mission phases. Shedding of Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus was detected in 8 of the 23 astronauts. These viruses reactivated independently of each other. Reactivation of Epstein-Barr virus, varicella-zoster virus, and cytomegalovirus increased in frequency, duration, and amplitude (viral copy numbers) when compared to short duration (10 to 16 days) space shuttle missions. No evidence of reactivation of herpes simplex virus type 1, herpes simplex virus type 2, or human herpes virus 6 was found. The mean diurnal trajectory of salivary cortisol changed significantly during flight as compared to before flight (P = 0.010). There was no statistically significant difference in levels of plasma cortisol or dehydoepiandosterone concentrations among time points before, during, and after flight for these international space station crew members, although observed cortisol levels were lower at the mid and late-flight time points. The data confirm that astronauts undertaking long-duration spaceflight experience both increased latent viral reactivation and changes in diurnal trajectory of salivary cortisol concentrations.

Prostaglandin E2 As a Modulator of Viral Infections

Viral infections are a major cause of infectious diseases worldwide. Inflammation and the immune system are the major host defenses against these viral infection. Prostaglandin E2 (PGE2), an eicosanoid generated by cyclooxygenases, has been shown to modulate inflammation and the immune system by regulating the expression/concentration of cytokines. The effect of PGE2 on viral infection and replication is cell type- and virus-family-dependent. The host immune system can be modulated by PGE2, with regards to immunosuppression, inhibition of nitrogen oxide (NO) production, inhibition of interferon (IFN) and apoptotic pathways, and inhibition of viral receptor expression. Furthermore, PGE2 can play a role in viral infection directly by increasing the production and release of virions, inhibiting viral binding and replication, and/or stimulating viral gene expression. PGE2 may also have a regulatory role in the induction of autoimmunity and in signaling via Toll-like receptors. In this review the known effects of PGE2 on the pathogenesis of various infections caused by herpes simplex virus, rotavirus, influenza A virus and human immunodeficiency virus as well the therapeutic potential of PGE2 are discussed.

Protective effect of resveratrol against pseudorabies virus-induced reproductive failure in a mouse model

Resveratrol (RES), a natural polyphenol that is abundant in grapes, exerts anti-inflammatory, anti-oxidative, and antiviral bioactive effects. Protective effects of RES against pseudorabies virus (PrV)- induced reproductive failure were investigated in a mice model. Injection of PrV partially induced stillbirth and abortion, and caused poor growth of progeny. Treatment with RES attenuated the reproductive failure induced by the virus with recovery of the serum progesterone level. RES improved the growth performance of newborn mice. RES can attenuate the reproductive failure induced by PrV in mice.

Infection homeostasis: implications for therapeutic and immune programming of metabolism in controlling infection

Homeostasis underpins at a systems level the regulatory control of immunity and metabolism. While physiologically these systems are often viewed as independent, there is increasing evidence showing a tight coupling between immune and metabolic functions. Critically upon infection, the homeostatic regulation for both immune and metabolic pathways is altered yet these changes are often investigated in isolation. Here, we summarise our current understanding of these processes in the context of a clinically relevant pathogen, cytomegalovirus. We synthesise from the literature an integrative view of a coupled immune-metabolic infection process, centred on sugar and lipid metabolism. We put forward the notion that understanding immune control of key metabolic enzymatic steps in infection will promote the future development of novel therapeutic modalities based on metabolic modifiers that either enhance protection or inhibit infection.

Cyclooxygenase-2-prostaglandin E2-eicosanoid receptor inflammatory axis: a key player in Kaposi's sarcoma-associated herpes virus associated malignancies

The role of cyclooxygenase-2 (COX-2), its lipid metabolite prostaglandin E2 (PGE2), and Eicosanoid (EP) receptors (EP; 1-4) underlying the proinflammatory mechanistic aspects of Burkitt's lymphoma, nasopharyngeal carcinoma, cervical cancer, prostate cancer, colon cancer, and Kaposi's sarcoma (KS) is an active area of investigation. The tumorigenic potential of COX-2 and PGE2 through EP receptors forms the mechanistic context underlying the chemotherapeutic potential of nonsteroidal anti-inflammatory drugs (NSAIDs). Although role of the COX-2 is described in several viral associated malignancies, the biological significance of the COX-2/PGE2/EP receptor inflammatory axis is extensively studied only in Kaposi's sarcoma-associated herpes virus (KSHV/HHV-8) associated malignancies such as KS, a multifocal endothelial cell tumor and primary effusion lymphoma (PEL), a B cell-proliferative disorder. The purpose of this review is to summarize the salient findings delineating the molecular mechanisms downstream of COX-2 involving PGE2 secretion and its autocrine and paracrine interactions with EP receptors (EP1-4), COX-2/PGE2/EP receptor signaling regulating KSHV pathogenesis and latency. KSHV infection induces COX-2, PGE2 secretion, and EP receptor activation. The resulting signal cascades modulate the expression of KSHV latency genes (latency associated nuclear antigen-1 [LANA-1] and viral-Fas (TNFRSF6)-associated via death domain like interferon converting enzyme-like- inhibitory protein [vFLIP]). vFLIP was also shown to be crucial for the maintenance of COX-2 activation. The mutually interdependent interactions between viral proteins (LANA-1/vFLIP) and COX-2/PGE2/EP receptors was shown to play key roles in the biological mechanisms involved in KS and PEL pathogenesis such as blockage of apoptosis, cell cycle regulation, transformation, proliferation, angiogenesis, adhesion, invasion, and immune-suppression. Understanding the COX-2/PGE2/EP axis is very important to develop new safer and specific therapeutic modalities for KS and PEL. In addition to COX-2 being a therapeutic target, EP receptors represent ideal targets for pharmacologic agents as PGE2 analogues and their blockers/antagonists possess antineoplastic activity, without the reported gastrointestinal and cardiovascular toxicity observed with few a NSAIDs.

Human cytomegalovirus regulates bioactive sphingolipids

Sphingolipids are present in membranes of all eukaryotic cells. Bioactive sphingolipids also function as signaling molecules that regulate cellular processes such as proliferation, migration, and apoptosis. Human cytomegalovirus (HCMV) exploits a variety of cellular signaling pathways to promote its own replication. However, whether HCMV modulates lipid signaling pathways is an essentially unexplored area of research in virus-host cell interactions. In this study, we examined the accumulation of the bioactive sphingolipids and the enzymes responsible for the biosynthesis and degradation of these lipids. HCMV infection results in increased accumulation and activity of sphingosine kinase (SphK), the enzyme that generates sphingosine 1-phosphate (S1P) and dihydrosphingosine 1-phosphate (dhS1P). We also utilized a mass spectrometry approach to generate a sphingolipidomic profile of HCMV-infected cells. We show that HCMV infection results in increased levels of dhS1P and ceramide at 24 h, suggesting an enhancement of de novo sphingolipid synthesis. Subsequently dihydrosphingosine and dhS1P decrease at 48 h consistent with attenuation of de novo sphingolipid synthesis. Finally, we present evidence that de novo sphingolipid synthesis and sphingosine kinase activity directly impact virus gene expression and virus growth. Together, these findings demonstrate that host cell sphingolipids are dynamically regulated upon infection with a herpes virus in a manner that impacts virus replication.

Possible role of human cytomegalovirus in pouchitis after proctocolectomy with ileal pouch-anal anastomosis in patients with ulcerative colitis

AIM: To detect the presence of human cytomegalovirus (HCMV) proteins and genes on the ileal pouch of patients with ulcerative colitis who have undergone proctocolectomy with ileal pouch-anal anastomosis (IPAA).

METHODS: Immunohistochemistry, polymerase chain reaction (PCR) and PCR sequencing methods were utilized to test the presence of HCMV in pouch specimens taken from 34 patients in 86 endoscopies.

RESULTS: HCMV genes and proteins were detected in samples from 12 (35.2%) patients. The rate of detection was significant in the endoscopies from patients diagnosed with pouchitis (5 of 12, 41.6%), according to the Japanese classification of pouchitis, in comparison to patients with normal pouch (7 of 62, 11.2%; P = 0.021). In all patients with pouchitis in which the HCMV was detected, it was the first episode of pouchitis. The virus was not detected in previous biopsies taken in normal endoscopies of these patients. During the follow-up, HCMV was detected in one patient with recurrent pouchitis and in 3 patients whose pouchitis episodes improved but whose positive endoscopic findings persisted.

CONCLUSION: HCMV can take part in the inflammatory process of the pouch in some patients with ulcerative colitis who have undergone proctocolectomy with IPAA.

Dendritic cell function in cytomegalovirus-infected patients with mononucleosis

Dendritic cells (DCs) are important target cells for human cytomegalovirus (HCMV) infection, and the virus has been shown to hamper the differentiation and maturation pathways of these cells in vitro. In the present study, we examined the function of monocyte-derived DCs obtained from immunocompetent individuals undergoing symptomatic HCMV infection in terms of immunophenotypic characteristics, pinocytosis, lymphocyte stimulation capacity, and cyto-chemokine secretion in comparison with DCs obtained from healthy controls. Immature and lipopolysaccharide (LPS)-stimulated DCs obtained from patients actively infected with HCMV expressed significantly lower levels of major histocompatibility complex (MHC) class II molecules. The inhibition of expression of MHC class II molecules by HCMV appeared to be functionally relevant, as mature DCs obtained from patients with HCMV mononucleosis were inefficient in stimulating proliferation of allogenic lymphocytes. Finally, the pattern of cyto-chemokines secreted by DCs obtained from patients with HCMV mononucleosis was characterized by a proinflammatory profile with an increased production of interleukin (IL)-1beta, tumor necrosis factor alpha, CC chemokine ligand 2 (CCL2) and CCL3, and reduced secretion of IL-10 upon LPS stimulation. During symptomatic HCMV infection in the immunocompetent host, DCs exhibit an impaired immunophenotype and function. These effects may contribute to the viral-induced immunomodulation, which is often observed in HCMV-infected patients.

Human cytomegalovirus downregulates complement receptors (CR3, CR4) and decreases phagocytosis by macrophages

Human cytomegalovirus (HCMV) infection is associated with an increased susceptibility to opportunistic infections. Although the subversion of adaptive immune responses has been extensively studied, the consequences of HCMV infection on natural immune responses are not well documented. A striking selective downmodulation of CD11b/CD18 (CR3) or CD11c/CD18 (CR4) was found upon HCMV infection, on two models, the monocytic THP-1 cell line and monocyte- derived macrophages. HCMV-infected macrophages have an altered adhesion/phagocytic capacity to Candida albicans, a pathogen responsible for some opportunistic infections in immunocompromised patients. These results suggest a new mechanism implicated in the augmentation of opportunistic infections in HCMV patients.

RSV-induced prostaglandin E2 production occurs via cPLA2 activation: role in viral replication

Prostaglandins (PGs) are lipid mediators that participate in the regulation of immunological and inflammatory responses, and PG production can affect viral replication. In this study, we have investigated the mechanism of PGE2 production in airway epithelial cells, following respiratory syncytial virus (RSV) infection, and its role in viral replication. We show that RSV infection strongly induces PGE2 secretion, in a time- and replication-dependent manner, through increased cyclooxygenase-2 (COX-2) expression, which occurs independently from viral or cellular protein synthesis. RSV infection induces arachidonic acid release through induction of cytoplasmic phospholipase A2 (cPLA2) enzymatic activity and its membrane translocation. Specific inhibitors of cPLA2 significantly block RSV-induced PGE2 secretion, indicating a key role of cPLA2 in viral-induced PG production. Blocking PG secretion, through cPLA2 or COX-2 inhibition, results in impairment of RSV replication and subsequent RSV-mediated epithelial cell responses, suggesting that inhibition of PG secretion could be beneficial in RSV infection by reducing proinflammatory mediator production.

Increased Levels of Tumor Necrosis Factor α Are Associated with an Increased Risk of Cytomegalovirus Infection after Allogeneic Hematopoietic Stem Cell Transplantation

Tumor necrosis factor-alpha (TNF) has been implicated in the reactivation of cytomegalovirus (CMV) at a cellular level. We therefore hypothesized that increased posttransplantation TNF levels may be associated with the development of CMV antigenemia (CMV-Ag). We studied 134 patients undergoing allogeneic hematopoietic stem cell transplantation. After excluding CMV-negative donor and recipient pairs, 94 patients were evaluable. By cluster analysis, 2 groups were designated by TNF levels obtained between days 4 and 7 after transplantation: 58 patients had low levels (median, 0 pg/mL; range, 0-5.5 pg/mL), and 36 patients had high levels (median, 43.75 pg/mL; range, 7.5-1756 pg/mL). To determine the independent effect of TNF on the development of CMV-Ag and acute graft-versus-host disease and on survival, Kaplan-Meier and Cox models stratified by TNF patient groups were evaluated. High TNF levels were associated with a more rapid onset of CMV-Ag (P < .001) and with the occurrence of the composite end point of CMV-Ag or death (P < .001). Factors independently associated with CMV-Ag in multivariate analysis were a high TNF level (hazard ratio [HR], 2.57; P = .003) and acute graft-versus-host disease (as a time-dependent covariate; HR, 2.30; P = .010). Factors independently associated with the composite end point of CNV-Ag or death were a high TNF level (HR, 2.42; P < .001) and patient age (per year; HR, 1.93; P = .017). In conclusion, a high posttransplantation TNF level is significantly associated with the risk for developing CMV infection. Early detection of high levels of TNF may be used to identify patients at high risk for developing CMV-Ag.

Cellular stress and signal transduction responses to human cytomegalovirus infection

Human cytomegalovirus (HCMV) receptor-ligand interactions and viral entry excite cellular responses such as receptor tyrosine kinase and mitogen-activated protein kinase signaling, cytoskeletal rearrangement, and the induction of transcription factors, prostaglandins, and cytokines. Bi-phasic stimulation of these pathways, excepting interferon, facilitates productive viral infection and likely contributes to viral pathogenesis.

Human cytomegalovirus carries a cell-derived phospholipase A2 required for infectivity

Human cytomegalovirus (HCMV) is known to carry host cell-derived proteins and mRNAs whose role in cell infection is not understood. We have identified a phospholipase A2 (PLA2) activity borne by HCMV by using an assay based on the hydrolysis of fluorescent phosphatidylcholine. This activity was found in all virus strains analyzed and in purified strains. It was calcium dependent and was sensitive to inhibitors of cytosolic PLA2 (cPLA2) but not to inhibitors of soluble PLA2 or calcium-independent PLA2. No other phospholipase activity was detected in the virus. Purified virus was found to contain human cellular cPLA2alpha, as detected by monoclonal antibody. No homology with PLA2 was found in the genome of HCMV, indicating that HCMV does not code for a PLA2. Decreased de novo expression of immediate-early proteins 1 and 2 (IE1 and IE2), tegument phosphoprotein pp65, and virus production was observed when HCMV was treated with inhibitors of cPLA2. Cell entry of HCMV was not altered by those inhibitors, suggesting the action of cPLA2 was postentry. Together, our results indicate a selective sorting of a cell-derived cPLA2 during HCMV maturation, which is further required for infectivity.

The role and regulation of COX-2 during viral infection

Prostaglandins are lipid mediators, generated by cyclooxygenase (COX), that have been shown to participate in the regulation of virus replication and the modulation of inflammatory responses following infection. A number of studies support a role for PGE2 in the modulation of virus replication and virulence in a cell type and virus selective manner. Virus infection also stimulates the expression of a number of proinflammatory gene products, including COX-2, inducible nitric oxide synthase (iNOS) as well as proinflammatory cytokines. This review will focus on the mechanisms by which proinflammatory prostaglandin production regulates virus replication and virulence. In addition, the signaling pathways that are activated during a virus infection, and that regulate proinflammatory gene expression in macrophages will be reviewed. Specific attention will be placed on the ability of virus infection to activate multiple signaling cascades (such as PKR, MAPK, iPLA2, NF-kappaB) and how these pathways are integrated in the regulation of individual target gene expression.

Mediators in HIV-associated cardiovascular disease: a focus on cytokines and genes

As longevity increases in HIV-infected individuals, late effects such as cardiovascular disease and, more specifically, symptomatic heart failure are emerging as leading health issues. In the present review, we discuss possible cytokine and gene-mediated effects on HIV-associated cardiovascular illness that may play a role in diagnosis, management, and therapy of HIV-associated heart failure.

Activation of monocyte cyclooxygenase-2 gene expression by human herpesvirus 6. Role for cyclic AMP-responsive element-binding protein and activator protein-1

Prostaglandin E(2) (PGE(2)) is an arachidonic acid metabolite mainly produced by activated monocytes/macrophages (Mo/Mphi) that display broad immunomodulatory activities. Several viruses capable of infecting Mo/Mphi modulate PGE(2) synthesis in a way that favors the infection processes and the spread of virions. In the present work, we studied the effect of human herpesvirus 6 (HHV-6) infection of Mo/Mphi on PGE(2) synthesis. Our results indicate that HHV-6 induces COX-2 gene expression and PGE(2) synthesis within a few hours of infection. We mapped the different promoter elements associated with COX-2 gene activation by HHV-6 to two cis-acting elements: a cyclic AMP-responsive element and an activator protein-1 element. HHV-6 immediate-early protein 2 was identified as a modulator of COX-2 gene expression in Mo/Mphi. Finally, addition of PGE(2) to HHV-6-infected peripheral blood mononuclear cells cultures was found to increase significantly viral replication. Overall, these results further contribute to the immunomodulatory properties of HHV-6 and highlight a potential role for eicosanoids in the replication process of this virus.

Inhibition of cyclooxygenase 2 blocks human cytomegalovirus replication

Cyclooxygenase 2 (COX-2) mRNA, protein, and activity are transiently induced after infection of human fibroblasts with human cytomegalovirus. Prostaglandin E(2), the product of COX-2 activity, is transiently increased by a factor of >50 in cultures of virus-infected fibroblasts. Both specific (BMS-279652, 279654, and 279655) and nonspecific (indomethacin) COX-2 inhibitors can abrogate the virus-mediated induction of prostaglandin E(2) accumulation. Levels of COX-2 inhibitors that completely block the induction of COX-2 activity, but do not compromise cell viability, reduce the yield of human cytomegalovirus in human fibroblasts by a factor of >100. Importantly, the yield of infectious virus can be substantially restored by the addition of prostaglandin E(2) together with the inhibitory drug. This finding argues that elevated levels of prostaglandin E(2) are required for efficient replication of human cytomegalovirus in fibroblasts. COX-2 inhibitors block the accumulation of immediate-early 2 mRNA and protein, but have little effect on the levels of immediate-early 1 mRNA and protein. Viral DNA replication and the accumulation of some, but not all, early and late mRNAs are substantially blocked by COX-2 inhibitors. Elevated levels of prostaglandin E(2) apparently facilitate the production of immediate-early 2 protein. The failure to produce normal levels of this critical viral regulatory protein in the presence of COX-2 inhibitors might block normal progression beyond the immediate-early phase of human cytomegalovirus infection.

Human cytomegalovirus infections in nonimmunosuppressed critically ill patients

OBJECTIVE

To assess the occurrence of active human cytomegalovirus (HCMV) infection and HCMV disease and to evaluate potential risk factors in immunocompetent intensive care patients after major surgery or trauma.

DESIGN

A prospective clinical study.

SETTING

An anesthesiological intensive care unit (ICU) in a university hospital.

PATIENTS

Fifty-six anti-HCMV immunoglobulin G (IgG) seropositive patients without manifest immunodeficiency whose simplified acute physiology score (SAPS II) value rose to >or=41 points during their ICU stay.

INTERVENTIONS

Once a week, the patients were examined for active HCMV infection by polymerase chain reaction and by viral cultures from blood and lower respiratory tract secretions. Three times a week, detailed clinical examination for signs of HCMV disease was carried out.

MEASUREMENTS AND MAIN RESULTS

Twenty of the 56 ICU patients (35.6%) who met the study criteria of a SAPS II score >40 points and anti-HCMV IgG seropositivity developed an active HCMV infection as diagnosed by the detection of HCMV DNA in leukocytes, plasma, or respiratory tract secretions. In seven patients, the virus was isolated in the respiratory tract secretions. Severe HCMV disease appeared in two patients with pneumonia or encephalitis respectively. In patients with active HCMV infection, the mortality tended to be higher (55%) than in those without (36%); the duration of intensive care treatment of the survivors was significantly longer in the patients with active HCMV infection (median 30 vs. 23 days; p = .0375). Univariate testing for factors associated with active HCMV infection showed the importance of sepsis at admission (p = .011) and prolonged pretreatment on the ward or in an external ICU (p = .002); the relevance of underlying malignant disease was borderline (p = .059). Multiple regression analysis identified only sepsis to be independently associated with active HCMV infection (p = .02; odds ratio, 4.62).

CONCLUSIONS

Even in a group of ICU patients without manifest immunodeficit who were anti-HCMV IgG seropositive and had reached a SAPS II score of >or=41 points, active HCMV infection occurred frequently (35.6%). Septic patients were affected twice as often as the total study population. In 2 of the 20 cases, active HCMV infection progressed to severe HCMV disease. Proper diagnosis demands special clinical attention combined with extended virological examinations. Further studies in a larger patient group should evaluate the influence of HCMV on ICU mortality.

The postoperative course of gamma-glutamyl transpeptidase--a marker of cytomegalovirus (CMV) replication risk?

Cytomegalovirus (CMV) infection is a common complication in the postoperative course of liver transplantation. In order to start early prophylactic therapy, but to avoid unnecessary treatment, or expensive screening, a desirable goal in post-transplant monitoring is to find appropriate markers in standard laboratory diagnostics. In the present study, the results of a 6-week CMV replication monitoring schedule by the pp65 antigenemia assay in 100 liver graft recipients were included. The activities of transaminases, glutamate dehydrogenase and gamma-glutamyl transpeptidase (gamma-GT) were measured by routine laboratory methods. In contrast to the transaminases, the serum activity of gamma-GT increased during the first postoperative week. The maximum levels were 246 +/- 211 U/l in patients without (n = 46) and 140 +/- 89 U/l in patients with early CMV replication (n = 54; p = 0.02). Patients with gamma-GT levels below 200 U/l on the 5th postoperative day (n = 72) had a CMV replication risk of 65%, whereas those patients with gamma-GT levels above this threshold had a risk of 30% (n = 28; p = 0.0007; relative risk = 2.9). These findings provide a routinely usable marker for the identification of patients at an increased risk of CMV replication. It can be considered that these phenomena may be caused by an additional immunosuppressive effect of the CMV virus.

Transient decreases in human T cell proliferative responses following vaccinia immunization

To further study the immunosuppression associated with virus infections, we analyzed the proliferative responses of serial PBMC samples obtained following vaccinia virus immunization. In four of five volunteers, responses to PHA, anti-CD3, vaccinia virus, and recall antigens were markedly decreased at at least one time point between days 5 and 29 after vaccination. Responses to PHA were restored by the addition of IL-2 or irradiated autologous healthy PBMC in the two volunteers tested, suggesting that the proliferation defect is attributable to accessory cell dysfunction. In one donor, immobilized anti-CD3 failed to induce proliferation, but addition of immobilized anti-CD28 partially restored proliferation. These results indicate that vaccinia virus infection can transiently suppress proliferative responses of PBMC, in part by causing accessory cell dysfunction. Our findings extend the list of viral infections associated with systemic immunologic effects and demonstrate that suppression of proliferation can occur with localized virus infections.

EBV suppresses prostaglandin E2 biosynthesis in human monocytes

It is well known that EBV has developed strategies to evade immune surveillance. Previously, EBV was shown to bind specifically to monocytes and regulate expression of proinflammatory mediators such as IL-1, IL-6, TNF-alpha, and leukotrienes. EBV was also found to affect phagocytosis of monocytes. In this study, we show that in addition to these effects, EBV suppresses the biosynthesis of PGE2, a pleiotropic immunomodulatory molecule that is synthesized by the dioxygenation of arachidonic acid via the cyclooxygenase (COX) pathway. This down-regulation of PGE2 formation involved the inhibition of the inducible COX-2 isoform expression both at the transcriptional and translational levels, whereas expression of the constitutive COX-1 isoform was unaltered. Furthermore, exposure of monocytes to EBV was found to impact on the NF-kappaB activation pathway, which plays an essential role in the induction of COX-2 in monocytes. The inhibition of PGE2 biosynthesis was relieved when the experiments were conducted in presence of phosphonoacetic acid, an inhibitor of herpesviruses DNA polymerase, indicating that viral replication and/or neosynthesized viral proteins were involved in this process. Thus, inhibition of PGE2 biosynthesis in monocytes may represent an additional mechanism underlying EBV pathogenicity.

Independent functioning of cytosolic phospholipase A2 and phospholipase D1 in Trp-Lys-Tyr-Met-Val-D-Met-induced superoxide generation in human monocytes

Recently, a novel peptide (Trp-Lys-Tyr-Met-Val-D-Met, WKYMVm) has been shown to induce superoxide generation in human monocytes. The peptide stimulated phospholipase A2 (PLA2) activity in a concentration- and time-dependent manner. Superoxide generation as well as arachidonic acid (AA) release evoked by treatment with WKYMVm could be almost completely blocked by pretreatment of the cells with cytosolic PLA2 (cPLA2)-specific inhibitors. The involvement of cPLA2 in the peptide-induced AA release was further supported by translocation of cPLA2 to the nuclear membrane of monocytes incubated with WKYMVm. WKYMVm-induced phosphatidylbutanol formation was completely abolished by pretreatment with PKC inhibitors. Immunoblot showed that monocytes express phospholipase D1 (PLD1), but not PLD2. GF109203X as well as butan-1-ol inhibited peptide-induced superoxide generation in monocytes. Furthermore, the interrelationship between the two phospholipases, cPLA2 and PLD1, and upstream signaling molecules involved in WKYMVm-dependent activation was investigated. The inhibition of cPLA2 did not blunt peptide-stimulated PLD1 activation or vice versa. Intracellular Ca2+ mobilization was indispensable for the activation of PLD1 as well as cPLA2. The WKYMVm-dependent stimulation of cPLA2 activity was partially dependent on the activation of PKC and mitogen-activated protein kinase, while PKC activation, but not mitogen-activated protein kinase activation, was an essential prerequisite for stimulation of PLD1. Taken together, activation of the two phospholipases, which are absolutely required for superoxide generation, takes place through independent signaling pathways that diverge from a common pathway at a point downstream of Ca2+.

Immunopathogenesis of haemorrhagic enteritis virus (HEV) in turkeys

Infection of turkeys with the haemorrhagic enteritis virus (HEV), a type II avian adenovirus, results in varying rates of morbidity and mortality. The disease is characterised by splenomegaly, intestinal haemorrhage, sudden death and immunosuppression. The mechanisms of HEV immunopathogenesis and immunosuppression are not fully understood. Recent studies indicate that immune responses play a central role in disease pathogenesis. HEV infects B cells and macrophages and induces necrosis as well as apoptosis in infected and possibly in by-stander cells. The ability of the infected birds to mount an optimum humoral immune response as well as normal macrophage functions such as phagocytosis may be impaired. Elevated numbers of splenic CD4(+) cells during the acute phase of infection may be associated with viral clearance. Types I and II interferons (IFN) and pro-inflammatory cytokines such as interleukin-6 and tumour necrosis-like factors (TNF) are released at the peak of the infection. Cytokines may play a protective as well as a destructive role. While a massive release of proinflammatory cytokines may lead to systemic shock associated with haemorrhagic enteritis and death, release of IFNs may protect turkeys from the disease. Treatment with thalidomide, which is a potent TNF down-regulatory drug, prevented HEV-induced intestinal haemorrhage and treatment with an IFN-inducing chemical prevented HEV-replication and inhibited HEV-induced pathological and histopathological lesions.

Cytopathology or immunopathology? The puzzle of cytomegalovirus pneumonitis revisited

Various hypotheses have been proposed to explain why cytomegalovirus pneumonitis (CMV-P) is frequent and severe in bone marrow transplant patients while remaining rare and mild in HIV infected patients. One hypothesis suggests that CMV-P is an immunopathological condition that is common in bone marrow transplantation (BMT) under the effects of an abnormally regenerating immune system that reacts against CMV infected lung tissue. Such a hypothesis implicates CD4 T lymphocytes as one of the critical cell populations involved in immunopathology and also suggests that this process would be aborted by CD4 T cell deficiency in HIV infection. However, studies correlating the onset of CMV-P with lymphocyte reconstitution following BMT have revealed that CD4 cells are present at very low frequencies in the blood during the early period after transplantation when most cases of CMV-P occur. Furthermore, studies directly investigating bronchoalveolar lavage cell types during episodes of CMV-P in BMT patients have also failed to demonstrate significant CD4 involvement and, instead, have emphasized a predominance of natural killer (NK) cells and CD8 cells. These findings serve as the basis for questioning the validity of a CD4-driven immunopathological model of CMV-P in BMT. On the other hand, a variety of experimental and clinical observations support the protective role of CMV-specific CD3+ CD8 T lymphocytes against CMV in both immunocompetent individuals and BMT patients. In a murine BMT model, adoptive transfer of syngeneic BM cells was associated with massive increases in lung CD8 cells which resulted in the resolution rather than the exacerbation of existing CMV-P. In the light of these findings a more plausible hypothesis for CMV-P in BMT is that during the early period after transplantation adequate protective CD8 responses are absent and an uncontrolled CMV proliferation is allowed to develop. Once a critical viral load is reached a cytokine 'storm' may be triggered in the lung tissue that aggravates direct CMV-associated cytopathic effects. Likely candidates for this process would include the release of tumour necrosis factor-alpha (TNF-alpha) from alveolar macrophages stimulated by interferon-gamma (IFN-gamma) released from NK cells that are reconstituted early after BMT.

Oligo-monoclonal immunoglobulins frequently develop during concurrent cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections in patients after renal transplantation

In the present study we report that the appearance of oligo-monoclonal immunoglobulins (oligoM-Igs) in the sera of transplanted individuals is concurrent with the detection of coincident active CMV infection and EBV replication. Eighty-four renal allograft patients were monitored with respect to CMV isolation, to CMV conventional serology and humoral response against the EBV trans-activator ZEBRA (an immediate-early antigen also called BZLF1). Titration of anti-ZEBRA antibodies (IgG and IgM) and amount of EBV DNA in serum were evaluated. Using the combination of four techniques (agarose gel electrophoresis, analytical isoelectric focusing, high resolution immunoelectrophoresis, immunofixation electrophoresis), oligoM-Igs were found in 25% of patients after allografting and significantly associated with rejection episodes (P < 0.001). Twenty out of 23 (86%) concurrent CMV/EBV infections were associated with serum oligoM-Igs (P < 0.001). One can thus reasonably assume that a sustained EBV replication following iatrogenic immunosuppression can promote the immunoglobulin heavy chain expression in EBV-infected B lymphocytes. The proliferation of immunoglobulin-secreting clones might occur after active CMV infection, through a transient over-immunosuppression or via immune subversion.

Impaired T Cell Proliferation in Acute Dengue Infection

Decreased proliferative responses to mitogens and recall Ags have been observed in PBMC obtained during several acute human viral infections. To determine whether cell-mediated responses are altered during acute dengue infection, we examined the proliferative responses of PBMC from children enrolled in a prospective study of dengue infections in Thailand. All responses of PBMC during acute illness were compared with the same patients’ PBMC obtained at least 6 mo after their infection. Proliferative responses to PHA, anti-CD3, tetanus toxoid, and dengue Ags were decreased significantly in PBMC obtained during the acute infection. The proliferative responses to PHA were restored by the addition of gamma-irradiated autologous convalescent or allogeneic PBMC. Cell contact with the irradiated PBMC was necessary to restore proliferation. Non-T cells from the acute PBMC of dengue patients did not support proliferation of T cells from control donors in response to PHA, but T cells from the PBMC of patients with acute dengue proliferated if accessory cells from a control donor were present. Addition of anti-CD28 Abs restored anti-CD3-induced proliferation of the PBMC of some patients. The percentage of monocytes was reduced in the acute sample of PBMC of the dengue patients. Addition of IL-2 or IL-7, but not IL-4 or IL-12, also restored proliferation of acute PBMC stimulated with anti-CD3. The results demonstrate that both quantitative and qualitative defects in the accessory cell population during acute dengue illness result in a depression of in vitro T cell proliferation.

Initial transforming event in myelodysplastic syndromes may be viral: case for cytomegalovirus

Myelodysplastic syndromes (MDS) are clonal hematopoietic disorders which begin in a pluripotential bone marrow (BM) stem cell. This early stem cell is believed to acquire a growth advantage over its neighbors as a result of an initial transforming event, the nature of which has remained obscure. In this paper, we propose that pathogens such as those belonging to the herpesvirus family of DNA viruses may play a role in the initial transformation of the stem cell. The case for cytomegalovirus (CMV) as a representative of this family of viruses is discussed at length and a molecular mechanism which may be involved in the oncogenic activity of CMV is proposed. No proof has been presented to implicate CMV directly in MDS, but circumstantial evidence which supports such a possibility is provided.

Cytomegalovirus viremia: risk factor for allograft cirrhosis after liver transplantation for hepatitis C

BACKGROUND

Despite recent advances in diagnosis and treatment, cytomegalovirus (CMV) infection continues to be a common cause of morbidity in liver transplant (LT) recipients. Because CMV infection suppresses cell-mediated immunity, which seems to be important in neutralizing hepatitis C virus (HCV) infection, we assessed the impact of CMV infection on histopathological HCV recurrence after LT.

METHODS

The study group was comprised of 43 consecutive LT recipients with at least 6 months of histologic follow-up. Group 1 consisted of the 8 patients who developed CMV viremia after LT; group 2 comprised the 35 patients without CMV viremia. There was no significant difference with regard to age, initial immunosuppression, incidence of rejection, distribution of HCV genotypes, or mean follow-up between the groups. Semiquantitative histopathologic assessment of allograft hepatitis was performed using the Knodell's score.

RESULTS

The mean total Knodell score of the final allograft biopsy was significantly greater in group 1 patients (P=0.016), with most of the difference due to periportal/bridging necrosis (P=0.009) and lobular activity subitem (P=0.01) scores. Half of the CMV viremic patients eventually developed allograft cirrhosis as compared with 11% of the CMV-negative patients (P=0.027). Accordingly, the cirrhosis-free actuarial survival by Kaplan-Meier estimates was significantly diminished in the CMV viremic patients. Glycoprotein B genotype analysis of CMV isolates revealed no significant differences between patients who did and those who did not develop allograft cirrhosis.

CONCLUSIONS

After LT for chronic HCV, patients who develop CMV viremia incur a significantly greater risk of severe HCV recurrence.

Prostaglandins in primate semen: biasing the immune system to benefit spermatozoa and virus?

The levels of prostaglandins in human semen are many orders of magnitude higher than those found elsewhere in the body and semen contains 19-hydroxy PGE which has not been found in other tissues. The reason for the presence of these prostaglandins is now becoming apparent with the demonstration of powerful effects of PGE and 19-hydroxy PGE on the balance of cytokines (stimulating IL-10 and inhibiting IL-12) released by antigen presenting cells. The effects of the seminal prostaglandins will be two-fold. First, there will be cAMP mediated direct effect on T cells, inhibiting clonal proliferation, inhibiting natural killer cell function and biasing the CD4 cells to a T-helper-2 pattern of cytokine production away from one that would favour a cell-mediated response. Second, and perhaps the major effect, is at the level of the antigen presenting cell that will reinforce the direct effects and induce a tolerance of antigens that are presented together with the IL-10, or PGE. Such tolerance might be necessary for the survival of the spermatozoa under adverse conditions, for instance, in the presence of infection Viruses and other invading organisms would also benefit from this switch in cytokines and the inhibition of the cell-mediated defences. Particular concerns are human immunodeficiency virus (HIV) and human papilloma virus (HPV) which can be transmitted in semen. Not only will the initial immune response be affected, but also repeated exposure to semen will reduce immunesurveillance and the removal of virally infected cells.