Direct Viral Replication Research Articles

IFNγ as an Immune Response in Groupers Infected by Viral Nervous Necrosis

One of the diseases reported to have infected groupers is Viral Nervous Necrosis (VNN) which can cause mass mortality in the larval stage of up to 100%. The nervous system of the fish so that the fish will lose their nerve control, develop weakness in motion, and cause death. In fish teleost, interferon (IFN) plays an important role in non-specific responses, especially in maintaining viral infections in vertebrates. The purpose of this study was to determine the immune response of the brain, kidney, and eye tissue receptors of grouper infected with Viral Necrosis (VNN) through flowcytometric analysis. The method used in this research is descriptive by analyzing and analyzing the IFNγ response in the brain, kidney, and eye tissue of VNN-infected groupers and healthy fish through flowcytometric analysis. The results of flowcytometric analysis showed that there was an immune response formed in the brain, kidney, and mouse grouper tissue by forming qualitative immune cells, namely the IFNγ immune response as a pro-inflammatory response to cells. The analysis showed that the IFNγ response in healthy grouper fish brain tissue was 0.21%, and VNN-infected fish was 0.55%. Healthy grouper fish eyes were 14.05%, and VNN infected fish was 17.73%. Then the kidney tissue of healthy grouper was 8.54%, and grouper infected with VNN was 16.08%. The response of all organs showed that fish had higher IFNγ values. IFNγ is important in the system due in part to its ability to inhibit direct viral replication, and most importantly its immunomodulatory effect.

Tick‐Borne Flaviviruses Activate the IRE1 Stress Pathway in a Virus‐ and Cell‐Type Dependent Manner Promoting Virus Replication

Tick-borne flaviviruses (TBFV) are transmitted by either tick-bite or consumption of raw milk products from infected ruminants. After crossing the blood-brain barrier, the virus enters the central nervous system (CNS) leading to neural inflammation and causing neurological complications. Individual viruses within this group, show differences in tissue tropism and pathogenicity. The mechanisms behind these differences are poorly understood, but likely result from a mix of direct viral replication and cellular responses to infection. Flavivirus replication is ER-associated and uses the cellular machinery for viral protein synthesis. The increased protein burden results in the activation of the unfolded protein response (UPR). The IRE1 pathway is hypothesized to support flavivirus replication by increasing protein and lipid biogenesis. We investigated the ER stress response following flavivirus infection in relevant target cell types as well as the effect of ER stress inhibition on virus replication. For this purpose, human astrocyte, neuronal and intestinal cell lines were infected with tick-borne encephalitis (TBEV) strains Neudörfl and HB171 as well as Langat virus (LGTV) and the rate of virus replication and activated UPR pathways in these cells were investigated. All three viruses activated the ER stress response in a virus- and cell-type dependent manner with IRE1 being the prominent pathway. The upregulation of X-box binding protein 1 (XBP1) as marker protein for the IRE1 pathway, differed between the cell lines and showed varying levels of intensities. The levels of activation of the IRE1 pathway among the three viruses correlated with their described levels of pathogenicity. As we found IRE1 to be the most strongly induced pathway, we further investigated the effect of three different IRE1 inhibitors on virus replication and cell viability during TBFV infection. Our data showed that TBFV replication was significantly reduced upon inhibition of the kinase and RNAse activity of IRE1, either combined or alone. These results confirm the supporting role of the IRE1 pathway for TBFV infection in relevant viral target cells and suggest that virus and cell-type dependent differences in UPR induction may affect the outcome of the infection.

Chimeric HCMV/HSV-1 and Δγ134.5 oncolytic herpes simplex virus elicit immune mediated antigliomal effect and antitumor memory

Malignant gliomas are the most common primary brain tumor and are characterized by rapid and highly invasive growth. Because of their poor prognosis, new therapeutic strategies are needed. Oncolytic virotherapy (OV) is a promising strategy for treating cancer that incorporates both direct viral replication mediated and immune mediated mechanisms to kill tumor cells. C134 is a next generation Δγ134.5 oHSV-1 with improved intratumoral viral replication. It remains safe in the CNS environment by inducing early IFN signaling which restricts its replication in non-malignant cells. We sought to identify how C134 performed in an immunocompetent tumor model that restricts its replication advantage over first generation viruses. To achieve this we identified tumors that have intact IFN signaling responses that restrict C134 and first generation virus replication similarly. Our results show that both viruses elicit a T cell mediated anti-tumor effect and improved animal survival but that subtle difference exist between the viruses effect on median survival despite equivalent in vivo viral replication. To further investigate this we examined the anti-tumor activity in immunodeficient mice and in syngeneic models with re-challenge. These studies show that the T cell response is integral to C134 replication independent anti-tumor response and that OV therapy elicits a durable and circulating anti-tumor memory. The studies also show that repeated intratumoral administration can extend both OV anti-tumor effects and induce durable anti-tumor memory that is superior to tumor antigen exposure alone.

HIV Infection and Myocardial Infarction.

After the advent of the potent combination antiretroviral therapy (cART) the incidence of acquired immune deficiency syndrome (AIDS) has declined dramatically and HIV infection became a chronic disease with a significant increase in the life expectancy of HIV-positive people. Consequently, chronic comorbidities as coronary heart disease raised an increasing concern in this population. Aim of this editorial article is to review the most recent data about the cardiovascular disease risk among HIV-positive persons and to suggest an appropriate clinical management. An increased risk of myocardial infarction has been reported among HIVinfected subjects compared to the general population, but the pathogenic mechanism of this accelerated atherosclerotic process is complex and certainly multifactorial. The occurrence of myocardial infarction may be the consequence of traditional risk factors (that are overrepresented in the HIVinfected population), direct viral replication, and long-term toxicity of the antiretroviral drugs. Moreover, despite the persistent viral suppression induced by cART usually reduces the cardiovascular risk, several studies show in HIV-positive subjects a condition of chronic inflammation and immune activation that could lead to both accelerated endothelial dysfunction and atherosclerotic disease. The cardiovascular risk reduction and coronary heart disease prevention are today a leading challenge for all the clinicians involved in the HIV patients' care.

Caspase-8 and FLIP Regulate RIG-I/MDA5-induced Innate Immune Host Responses to Picornaviruses

Picornaviruses are small, nonenveloped, positive-stranded RNA viruses, which cause a wide range of animal and human diseases, based on their distinct tissue and cell type tropisms. Myocarditis, poliomyelitis, hepatitis and the common cold are the most significant human illnesses caused by picornaviruses. The host response to picornaviruses is complex, and the damage to tissues occurs not only from direct viral replication within infected cells. Picornaviruses exhibit an exceptional ability to evade the early innate immune response, resulting in chronic infection and autoimmunity. This review discusses the detailed aspects of the early innate host response to picornaviruses infection mediated by RIG-I-like helicases, their adaptor, mitochondrial ant iviral signaling protein, innate immune-induced apoptosis, and the role of caspase-8 and its regulatory paralog, FLIP, in these processes.

D471G Mutation in LCMV-NP Affects Its Ability to Self-associate and Results in a Dominant Negative Effect in Viral RNA Synthesis

Arenaviruses merit significant interest because several family members are etiological agents of severe hemorrhagic fevers, representing a major burden to public health. Currently, there are no FDA-licensed vaccines against arenaviruses and the only available antiviral therapy is limited to the use of ribavirin that is partially effective. Arenavirus nucleoprotein (NP) is found associated with the genomic RNA forming the viral ribonucleoproteins (vRNPs) that together with the polymerase (L) direct viral replication and transcription. Virion formation requires the recruitment of vRNPs into budding sites, a process in which the arenavirus matrix-like protein (Z) plays a major role. Therefore, proper NP-NP and NP-Z interactions are required for the generation of infectious progeny. In this work we demonstrate the role of the amino acid residue D471 in the self-association of lymphocytic choriomeningitis virus nucleoprotein (LCMV-NP). Amino acid substitutions at this position abrogate NP oligomerization, affecting its ability to mediate replication and transcription of a minigenome reporter plasmid. However, its ability to interact with the Z protein, counteract the cellular interferon response and bind to dsRNA analogs was retained. Additionally, we also document the dominant negative effect of D471G mutation on viral infection, suggesting that NP self-association is an excellent target for the development of new antivirals against arenaviruses.

Regulatory T cells and Th17 cells in Viral Infections: Implications for Multiple Sclerosis and Myocarditis

In immune-mediated diseases, Treg and proinflammatory Th17 cells have been suggested to play either suppressor (beneficial) or effector (detrimental) roles, respectively. Tissue damage in viral infections can be caused by direct viral replication or immunopathology. Viral replication can be enhanced by anti-inflammatory responses and suppressed by proinflammatory responses. However, Tregs could suppress proinflammatory responses, reducing immunopathology, while Th17 cell-induced inflammation may enhance immunopathology. Here, the roles of Treg and Th17 cells depend on whether tissue damage is caused by direct virus replication or immunopathology, which differ depending on the virus, disease stage and host immune background. Although the precise mechanisms of tissue damage in multiple sclerosis and myocarditis are unclear, both viral replication and immune effector cells have been proposed to cause pathogenesis. Personalized medicine that alters the balance between Treg and Th17 cells may ameliorate viral pathology during infections.

Interactions between prostaglandins, leukotrienes and HIV-1: Possible implications for the central nervous system

In HIV-1-infected individuals, there is often discordance between viremia in peripheral blood and viral load found in the central nervous system (CNS). Although the viral burden is often lower in the CNS compartment than in the plasma, neuroinflammation is present in most infected individuals, albeit attenuated by the current combined antiretroviral therapy. The HIV-1-associated neurological complications are thought to result not only from direct viral replication, but also from the subsequent neuroinflammatory processes. The eicosanoids - prostanoids and leukotrienes - are known as potent inflammatory lipid mediators. They are often present in neuroinflammatory diseases, notably HIV-1 infection. Their exact modulatory role in HIV-1 infection is, however, still poorly understood, especially in the CNS compartment. Nonetheless, a handful of studies have provided evidence as to how these lipid mediators can modulate HIV-1 infection. This review summarizes findings indicating how eicosanoids may influence the progression of neuroAIDS.

Impact of γ‐chain cytokines on T cell homeostasis in HIV‐1 infection: therapeutic implications

CD4(+) T cell lymphocytes are a major target for human immunodeficiency virus type-1 (HIV-1) infection. During this chronic infection, CD4(+) T cell loss (induced through direct viral replication), generalized immune activation and increased susceptibility to apoptosis result in impaired T cell homeostasis with subsequent development of opportunistic infections and cancers. Highly active antiretroviral therapy (HAART) has a well-defined, beneficial effect on HIV-1-related clinical outcome; however, it does not lead to normalization of immune dysregulation. In order to boost both CD4(+) T cell restoration and HIV-1 specific immunity, immunotherapy with gamma-chain cytokines has been used in HIV-1-infected patients during concomitant HAART. In this review, we summarize the role of gamma-chain cytokines, especially interleukin (IL)-2 and IL-7, in influencing T cell homeostasis and proliferation, and discuss how immunotherapy with these cytokines may be beneficial to reconstitute the T cell compartment in the context of HIV-1 infection. The intriguing results of two large trials evaluating the efficacy of IL-2 in restoring immune function during HIV-1 infection are also discussed. In addition, we consider the promises and caveats of the first phase I/II clinical trials with IL-7 in HIV-1-infected patients and the knowledge that is still lacking in the field of T cell reconstitution through gamma-chain cytokines.

Evolutionary Constraints Acting on DDX3X Protein Potentially Interferes with Rev-Mediated Nuclear Export of HIV-1 RNA

Differential host-pathogen interactions direct viral replication in infected cells. In HIV-1 infected cells, nuclear export of viral RNA transcripts into cellular cytoplasm is governed by interaction of HIV-1 Rev, Exportin-1 (CRM-1) and DDX3X. Knock down of DDX3X has been shown to drastically impair HIV replication. Here we show that evolutionary forces are responsible for demarking previously unidentified critical functionally important residues on the surface of DDX3X. Using computational approaches, we show that these functional residues, depending on their location, are capable of regulating ATPase and RNA helicase functions of DDX3X. The potential of these residues in designing better blockers against HIV-1 replication was also assessed. Also, using stepwise docking simulations, we could identify DDX3X-CRM-1 interface and its critical functional residues. Our data would help explain the role of DDX3X in HIV-1 Rev function with potential to design new intervention strategies against HIV-1 replication.

Influence of Dendritic Cells on Viral Pathogenicity

Although most viral infections cause minor, if any, symptoms, a certain number result in serious illness. Viral disease symptoms result both from direct viral replication within host cells and from indirect immunopathological consequences. Dendritic cells (DCs) are key determinants of viral disease outcome; they activate immune responses during viral infection and direct T cells toward distinct T helper type responses. Certain viruses are able to skew cytokine secretion by DCs inducing and/or downregulating the immune system with the aim of facilitating and prolonging release of progeny. Thus, the interaction of DCs with viruses most often results in the absence of disease or complete recovery when natural functions of DCs prevail, but may lead to chronic illness or death when these functions are outmanoeuvred by viruses in the exploitation of DCs.

Treatment of Acute Idiopathic Dilated Cardiomyopathy with Intravenous Immunoglobulin: A Case Series of Nine Patients

Background: Pathogenesis of acute idiopathic dilated cardiomyopathy (DCMP) is not understood. Cardiac damage occurs either from direct viral replication or post-infectious myocardial inflammation. There have been case reports and series of pts with DCMP treated with intravenous immunoglobulin (IVIG), with variable degrees of success. The only randomized, placebo-controlled trial of IVIG in idiopathic DCMP failed to show long term benefit. Methods: We reviewed data on 9 consecutive pts with a diagnosis of idiopathic DCMP and hemodynamic compromise who received IVIG at a total dose of 2g/kg, administered as 1g/kg daily on two consecutive days.

Impact of direct virus-induced neuronal dysfunction and immunological damage on the progression of flavivirus (Modoc) encephalitis in a murine model.

Flavivirus encephalitis is believed to be the result of two main mechanisms: (i) direct damage to and dysfunction of neurons as a result of viral replication and (ii) destruction of the brain tissue by an inflammatory response. The differential impact of both mechanisms on the progression of flavivirus encephalitis has not been clearly determined. We have now studied the encephalitis caused by Modoc virus (MODV) infection in (i) severe combined immunodeficiency (SCID) mice, (ii) immunocompetent NMRI mice, and (iii) NMRI mice under varying immunosuppressive treatment regimens. In SCID mice, Modoc virus infection proved to be uniformly lethal (100%). The virus replicated extensively in neurons and no signs of inflammation of the brain were observed. In immunocompetent NMRI mice, intranasal (but not intraperitoneal) inoculation with MODV caused severe encephalitis accompanied by a fulminate inflammatory response. When NMRI mice, infected with MODV via the intraperitoneal route, were submitted to a brief immunosuppressive treatment, they also developed encephalitis with an obvious inflammatory component. These animals died significantly earlier than NMRI mice, which received immunosuppressive treatment for a longer period of time. In the latter group, no signs of inflammation of the brain were noted. These models thus allow us to distinguish between the impact of direct viral replication and that of immunological factors in the development of MODV encephalitis, and let us to conclude that (i) replication of the virus in neurons is sufficient to cause fatal encephalitis and (ii) immunological factors contribute significantly to disease progression.

Sindbis-group alphavirus replication in periosteum and endosteum of long bones in adult mice.

Several alphaviruses, including the Sindbis-group viruses, Ross River virus, O'nyong-nyong virus, and Chikungunya virus, are associated with outbreaks of acute and persistent arthralgia and arthritis in humans. Mechanisms underlying alphavirus-induced arthralgia and arthritis are not clearly understood, though direct viral replication within or around the affected joints is thought to contribute to disease. S.A.AR86 is a Sindbis-group alphavirus closely related to the arthralgia-associated Ockelbo and Girdwood S.A viruses. Following inoculation with S.A.AR86 derived from a molecular clone, infectious virus was isolated from bone and joint tissue 1 to 6 days postinfection. Studies using either in situ hybridization or S.A.AR86-derived double promoter viruses and replicons expressing green fluorescent protein localized sites of viral replication to the periosteum, tendons, and endosteum within the epiphyses of the long bones adjacent to articular joints. These results demonstrate that alphaviruses associated with arthralgia in humans replicate within bone-associated connective tissue adjacent to articular joints in an adult mouse model.

Virologic and Pathogenetic Aspects of Cytomegalovirus Infection

Cytomegalovirus (CMV) is a ubiquitous agent that rarely causes disease in immunocompetent humans but is an important cause of morbidity and mortality in the immunocompromised. A number of host and viral factors are associated with pathology following CMV infection. CMV can be found at many sites in the body but only causes disease at some of these and then only in certain patient populations. In some situations the mechanism underlying disease is direct viral replication, but in others, particularly CMV pneumonitis in allogeneic transplant recipients, an immunopathologic basis is strongly implicated. An important factor in the pathogenesis of infection and the expression of symptomatic disease is the source of CMV infection-whether it arises from an exogenous source or is due to reactivation of latent endogenous virus. Exogenous infection can occur in previously seronegative individuals or in those with prior exposure to the virus. In renal transplant recipients both types of exogenous infection have been associated with disease. Another factor that affects the interaction between CMV and its host is the modulating effect of the virus on the host immune response, the mechanism of which remains unknown.

Ultrastructural and immunohistochemical study of the human kidney in Argentine Haemorrhagic Fever

In six lethal cases of Argentine Haemorrhagic Fever (AHF) a disease caused by Junin virus, kidney samples were studied by means of immunofluorescent and electron microscopic techniques.--The ultrastructural studies showed that the distal and collecting tubes presented a large number of virus like intracytoplasmic particles. Those particles were present in the lumen of the endoplasmic reticulum cisternae and showed two distinct morphological aspects. Some of them were of high electron density and contained a few granules. The others were larger in size, electron lucid, and contained a variable number of ribosome like granules. Both types of particles originated from the endoplasmic reticulum wall by a process of budding. The presence of these particles was coincident with a severe cell damage which lead to necrosis and desquamation; and with large quantities of Junin virus antigen as demonstrated by immunofluorescence.--On the basis of these observations it is assumed that in AHF the cell damage is due to direct viral replication within the affected cells.