Identification of Interleukin1ß as an Amplifier of Interferon alpha-induced Antiviral Responses.

The induction of an interferon-mediated response is the first line of defense against pathogens such as viruses. Yet, the dynamics and extent of interferon alpha (IFNα)-induced antiviral genes vary remarkably and comprise three expression clusters: early, intermediate and late. By mathematical modeling based on time-resolved quantitative data, we identified mRNA stability as well as a negative regulatory loop as key mechanisms endogenously controlling the expression dynamics of IFNα-induced antiviral genes in hepatocytes. Guided by the mathematical model, we uncovered that this regulatory loop is mediated by the transcription factor IRF2 and showed that knock-down of IRF2 results in enhanced expression of early, intermediate and late IFNα-induced antiviral genes. Co-stimulation experiments with different pro-inflammatory cytokines revealed that this amplified expression dynamics of the early, intermediate and late IFNα-induced antiviral genes can also be achieved by co-application of IFNα and interleukin1 beta (IL1ß). Consistently, we found that IL1ß enhances IFNα-mediated repression of viral replication. Conversely, we observed that in IL1ß receptor knock-out mice replication of viruses sensitive to IFNα is increased. Thus, IL1ß is capable to potentiate IFNα-induced antiviral responses and could be exploited to improve antiviral therapies.

Differential Requirements for Tcf1 Long Isoforms in CD8+ and CD4+ T Cell Responses to Acute Viral Infection.

In response to acute viral infection, activated naive T cells give rise to effector T cells that clear the pathogen and memory T cells that persist long-term and provide heightened protection. T cell factor 1 (Tcf1) is essential for several of these differentiation processes. Tcf1 is expressed in multiple isoforms, with all isoforms sharing the same HDAC and DNA-binding domains and the long isoforms containing a unique N-terminal ß-catenin-interacting domain. In this study, we specifically ablated Tcf1 long isoforms in mice, while retaining expression of Tcf1 short isoforms. During CD8+ T cell responses, Tcf1 long isoforms were dispensable for generating cytotoxic CD8+ effector T cells and maintaining memory CD8+ T cell pool size, but they contributed to optimal maturation of central memory CD8+ T cells and their optimal secondary expansion in a recall response. In contrast, Tcf1 long isoforms were required for differentiation of T follicular helper (TFH) cells, but not TH1 effectors, elicited by viral infection. Although Tcf1 short isoforms adequately supported Bcl6 and ICOS expression in TFH cells, Tcf1 long isoforms remained important for suppressing the expression of Blimp1 and TH1-associated genes and for positively regulating Id3 to restrain germinal center TFH cell differentiation. Furthermore, formation of memory TH1 and memory TFH cells strongly depended on Tcf1 long isoforms. These data reveal that Tcf1 long and short isoforms have distinct, yet complementary, functions and may represent an evolutionarily conserved means to ensure proper programming of CD8+ and CD4+ T cell responses to viral infection.

Effective Treatment of Experimental Lymphocytic Choriomeningitis Virus Infection: Consideration of Favipiravir for Use With Infected Organ Transplant Recipients.

Lymphocytic choriomeningitis virus (LCMV) poses a substantial risk to immunocompromised individuals. The case fatality rate in recent clusters of LCMV infection in immunosuppressed organ transplantation recipients has exceeded 70%. In the present study, we demonstrate potent antiviral activity of favipiravir against acute, disseminated LCMV infection in NZB mice. Treatment resulted in complete protection against mortality and dramatic reductions in viral loads. In contrast, ribavirin, the current antiviral of choice, was mostly ineffective. Our findings, and the high lethality associated with LCMV infection in transplant recipients, support the consideration of favipiravir as a first-line therapeutic option.

Seroprevalence of lymphocytic choriomeningitis virus and Ljungan virus in Finnish patients with suspected neurological infections.

Directly-transmitted rodent-borne zoonotic viruses, such as lymphocytic choriomeningitis virus (LCMV) can cause nervous system infections. Rodent-borne Ljungan virus (LV) is considered potentially zoonotic possibly causing neurological symptoms. Our objective was to understand the role of these two viruses compared to other pathogens in causing neurological infections in Finnish patients. Routine screening data were available for 400 patients aged 5-50 years, collected from December 2013 to December 2014 with suspected neurological infection. Depending on symptoms, patients were variously tested for herpesviruses, enteroviruses, varicella zoster virus, and Mycoplasma pneumoniae, while those suspected of tick bite were further tested for Borrelia spp. and tick-borne encephalitis virus using antibody and/or nucleic acid tests. For 380 patients, we also screened the RNA and antibody prevalence of LCMV and LV in order to test if either of these viruses were the causative agent. Data collected indicated that the causative microbial agent was confirmed in only 15.5% of all Finnish patients with neurological symptoms, with M. pneumoniae (26 cases) being the most common causative agent found in sera, whereas Borrelia spp. (15), herpes simplex viruses (7), and enteroviruses (5) were the most common agents confirmed in the CSF. The seroprevalences for LV and LCMV were 33.8% and 5.0%, respectively, but no samples were PCR-positive. In this study, M. pneumoniae and Borrelia spp. were the most common causative agents of neurological infections in Finland. No LCMV or LV infections were detected. We conclude there was no association of LV with neurological diseases in this patient cohort.

TNFRs and Control of Chronic LCMV Infection: Implications for Therapy.

The control of persistent viral infections requires the immune system to limit the spread of the virus while avoiding immunopathology. Recent studies have revealed that members of the tumor necrosis factor receptor (TNFR) superfamily play unique and pivotal roles in control of chronic lymphocytic choriomeningitis virus (LCMV) infection and in some settings can tip the balance between immune control and immune pathology. We review these findings and discuss how our understanding of the role of TNFRs in the immune response to chronic LCMV infection may shed light on what happens during HIV infection in humans. We discuss preclinical models of TNF/TNFR family-targeted immunotherapy of chronic LCMV infection and evaluate which TNFRs present the most promising targets for immune intervention.

Lymphocytic choriomeningitis virus meningoencephalitis in a renal transplant recipient following exposure to mice.

Solid organ transplant recipients (SOTR) are at increased risk for a wide variety of typical and atypical infections as a consequence of impaired cell mediated and humoral immunity. We report a case of meningoencephalitis in a renal transplant recipient caused by lymphocytic choriomeningitis virus (LCMV) acquired by exposure to mice excreta. The clinical course was complicated by the development of hydrocephalus, requiring a ventriculoperitoneal shunt. To our knowledge, this is the first reported case of LCMV infection in a SOTR that was not organ donor derived.

Microcephaly Caused by Lymphocytic Choriomeningitis Virus.

We report congenital microencephaly caused by infection with lymphocytic choriomeningitis virus in the fetus of a 29-year-old pregnant women at 23 weeks' gestation. The diagnosis was made by ultrasonography and negative results for other agents and confirmed by a positive PCR result for lymphocytic choriomeningitis virus in an amniotic fluid sample.

Sequence-specific detection of different strains of LCMV in a single sample using tentacle probes.

BACKGROUND: Virus infections often result in quasispecies of viral strains that can have dramatic impacts on disease outcomes. However, sequencing of viruses to determine strain composition is time consuming and often cost-prohibitive. Rapid, cost-effective methods are needed for accurate measurement of virus diversity to understand virus evolution and can be useful for experimental systems. METHODS: We have developed a novel molecular method for sequence-specific detection of RNA virus genetic variants called Tentacle Probes. The probes are modified molecular beacons that have dramatically improved false positive rates and specificity in routine qPCR. To validate this approach, we have designed Tentacle Probes for two different strains of Lymphocytic Choriomeningitis Virus (LCMV) that differ by only 3 nucleotide substitutions, the parental Armstrong and the more virulent Clone-13 strain. One of these mutations is a missense mutation in the receptor protein GP1 that leads to the Armstrong strain to cause an acute infection and Clone-13 to cause a chronic infection instead. The probes were designed using thermodynamic calculations for hybridization between target or non-target sequences and the probe. RESULTS: Using this approach, we were able to distinguish these two strains of LCMV individually by a single nucleotide mutation. The assay showed high reproducibility among different concentrations of viral cDNA, as well as high specificity and sensitivity, especially for the Clone-13 Tentacle Probe. Furthermore, in virus mixing experiments we were able to detect less than 10% of Clone-13 cDNA diluted in Armstrong cDNA. CONCLUSIONS: Thus, we have developed a fast, cost-effective approach for identifying Clone-13 strain in a mix of other LCMV strains.

The impact of illegal waste sites on a transmission of zoonotic viruses.

BACKGROUND: Illegal waste disposal impacts public health and causes aesthetic and environmental pollution. Waste disposed in places without permitted and controlled facilities can provide a ready source of nutrition and shelter for rodents and thus promote the spread of their ecto- and endoparasites. The presence of two distinct zoonotic viruses, lymphocytic choriomeningitis virus (LCMV) and tick-borne encephalitis virus (TBEV), was searched at illegal waste sites. The aim of this study was to determine the prevalence of infection with both viruses in rodents and to discuss the virus-rodent relations in such environments. METHODS: Rodents sampled between October 2011 and April 2013 at 7 locations in the Istrian peninsula, were identified morphologically and genetically to minimize misidentification. Serological and molecular techniques were used to determine seroprevalence of infection in rodents and to detect viral RNAs. Serological testing was performed by immune fluorescence assay for detection of LCMV and TBEV specific antibodies. Real-time RT PCR was used for the detection of LCMV nucleoprotein gene and TBEV 3' non-coding region. Data were statistically analysed using SPSS statistic v2.0. RESULTS: Out of 82 rodent sera tested, the presence of LCMV antibodies was demonstrated in 24.93%. The highest prevalence of LCMV infection was found in commensal Mus musculus (47.37%), followed by 11.53%, 19.04% and 25% prevalence of infection in A. agrarius, A. flavicolis and A. sylvaticus, respectively. The highest prevalence of infection in rodents (53.33%) was found in locations with large waste sites and high anthropogenic influence. LCMV seroprevalence was significantly lower in rodents sampled from natural habitats. Viral nucleic acids were screened in 46 samples but yielded no amplicons of LCMV or TBEV. In addition, TBEV specific antibodies were not detected. CONCLUSIONS: Illegal waste sites have considerable impact on the area where they are located. Results have shown that the transmission of human pathogens can be significantly increased by the presence of waste sites. However, the pathogen must be endemic in the environment where the waste site is located. The introduction of a human pathogen as a consequence of the waste site in the area of interest could not be proven.

High clinical suspicion of donor-derived disease leads to timely recognition and early intervention to treat solid organ transplant-transmitted lymphocytic choriomeningitis virus.

Despite careful donor screening, unexpected donor-derived infections continue to occur in organ transplant recipients (OTRs). Lymphocytic choriomeningitis virus (LCMV) is one such transplant-transmitted infection that in previous reports has resulted in a high mortality among the affected OTRs. We report a LCMV case cluster that occurred 3 weeks post-transplant in three OTRs who received allografts from a common organ donor in March 2013. Following confirmation of LCMV infection at Centers for Disease Control and Prevention, immunosuppression was promptly reduced and ribavirin and/or intravenous immunoglobulin therapy were initiated in OTRs. The liver recipient died, but right kidney recipients survived without significant sequelae and left kidney recipient survived acute LCMV infection with residual mental status deficit. Our series highlights how early recognition led to prompt therapeutic intervention, which may have contributed to more favorable outcome in the kidney transplant recipients.

Evidence of lymphocytic choriomeningitis virus (LCMV) in domestic mice in Gabon: risk of emergence of LCMV encephalitis in Central Africa.

Lymphocytic choriomeningitis virus (LCMV) can cause acute fatal disease on all continents but was never detected in Africa. We report the first detection of LCMV RNA in a common European house mouse (Mus musculus domesticus) in Africa. Phylogenetic analyses show a close relationship with North American strains. These findings suggest that there is a risk of the appearance of LCMV acute encephalitis cases. This is a perfect example of virus dissemination by its natural host that may have dramatic public health consequences.

Notes from the Field: Lymphocytic Choriomeningitis Virus Meningoencephalitis from a Household Rodent Infestation - Minnesota, 2015.

On April 20, 2015, a female aged 15 years sought care at her pediatrician's office after 5 days of fever, myalgia, left parietal headache, and photophobia. A rapid influenza assay was negative, and erythrocyte sedimentation rate and total white blood cell count were normal. She improved with symptomatic care at home, but returned to her pediatrician's office on April 28, reporting recurrence of her headache and photophobia and new onset of a stiff neck. She was admitted to the hospital, where she was febrile to 102.9°F (39.4°C) and had meningismus. Computed tomography scan of her head was normal, and a cerebrospinal fluid (CSF) analysis showed a markedly elevated white blood cell count with 68% lymphocytes, low glucose, and a negative Gram stain. She was treated empirically for both bacterial and herpes simplex virus meningitis. The patient's hospital course was notable for hypotension (blood pressure 81/50), irritability, and pancreatitis with a peak lipase of 8,627 U/L. CSF cultures yielded no growth, and CSF polymerase chain reaction (PCR) testing for herpes simplex virus was negative. Nucleic acid amplification testing, acid-fast bacilli stain, and acid-fast bacilli cultures of CSF were negative for Mycobacterium tuberculosis. Results of investigations for human immunodeficiency virus, syphilis, Lyme disease, human herpesvirus 6 and 7, and species of Babesia, Toxoplasma, Histoplasma, Cryptococcus, Blastomyces, and Brucella were negative. She recovered and was discharged on hospital day 11 with no apparent sequelae.

Development and application of ELISA for the detection of IgG antibodies to lymphocytic choriomeningitis virus.

Lymphocytic choriomeningitis virus (LCMV) is a neglected human pathogen, which can cause severe illnesses in humans. The most vulnerable are the human foetus and immunosuppressed individuals. Since there is no commercially available enzyme-linked immunosorbent assay (ELISA) for the diagnosis of anti-LCMV antibodies in human sera, we developed a sandwich ELISA method detecting anti-nucleoprotein IgG antibodies, using a specific monoclonal anti-nucleoprotein antibody and cells persistently infected with LCMV strain MX as antigen. In the present study we show standardization of this ELISA protocol, determination of its clinical specificity and sensitivity and its application on 30 clinical samples from multiorgan donors. Comparison of these results to the indirect immunofluorescence antibody test (IFA) demonstrates that ELISA is more sensitive. The developed ELISA assay provides a fast, simple and efficient tool for the clinical detection of anti-nucleoprotein antibodies in human sera.

Human plasmacytoid dendritic cells sense lymphocytic choriomeningitis virus-infected cells in vitro.

We previously reported that exosomal transfer of hepatitis C virus (HCV) positive-strand RNA from human Huh-7 hepatoma cells to human plasmacytoid dendritic cells (pDCs) triggers pDC alpha/beta interferon (IFN-α/ß) production in a Toll-like receptor 7 (TLR7)-dependent, virus-independent manner. Here we show that human pDCs are also activated by a TLR7-dependent, virus-independent, exosomal RNA transfer mechanism by human and mouse hepatoma and nonhepatoma cells that replicate the negative-strand lymphocytic choriomeningitis virus (LCMV).

CD70 deficiency impairs effector CD8 T cell generation and viral clearance but is dispensable for the recall response to lymphocytic choriomeningitis virus.

CD27 interactions with its ligand, CD70, are thought to be necessary for optimal primary and memory adaptive immune responses to a variety of pathogens. Thus far, all studies addressing the function of the CD27-CD70 axis have been performed in mice lacking CD27, in those overexpressing CD70, or in those in which these molecules were blocked or mimicked by Abs or recombinant soluble CD70. Because these methods have in some cases led to divergent results, we generated CD70-deficient mice to directly assess its role in vivo. We find that lack of CD70-mediated stimulation during primary responses to lymphocytic choriomeningitis virus lowered the magnitude of CD8 Ag-specific T cell response, resulting in impaired viral clearance, without affecting CD4 T cell responses. Unexpectedly, CD70-CD27 costimulation was not needed for memory CD8 T cell generation or the ability to mount a recall response to lymphocytic choriomeningitis virus. Adoptive transfers of wild-type memory T cells into CD70(-/-) or wild-type hosts also showed no need for CD70-mediated stimulation during the course of the recall response. Moreover, CD70 expression by CD8 T cells could not rescue endogenous CD70(-/-) cells from defective expansion, arguing against a role for CD70-mediated T:T help in this model. Therefore, CD70 appears to be an important factor in the initiation of a robust and effective primary response but dispensable for CD8 T cell memory responses.

Notes from the field: a cluster of lymphocytic choriomeningitis virus infections transmitted through organ transplantation - Iowa, 2013.

On April 26, 2013, the United Network for Organ Sharing reported to CDC a cluster of ill organ transplant recipients in Iowa with a common organ donor. Infection with lymphocytic choriomeningitis virus (LCMV) was suspected. LCMV is a rodent-borne virus that most commonly causes nonfatal, influenza-like illness and occasional aseptic meningitis, but when transmitted through organ transplantation or in utero can cause severe, life-threatening disease.

Lymphocytic choriomeningitis virus-associated meningitis, southern Spain.

Lymphocytic choriomeningitis virus (LCMV) was detected in 2 patients with acute meningitis in southern Spain within a 3-year period. Although the prevalence of LCMV infection was low (2 [1.3%] of 159 meningitis patients), it represents 2.9% of all pathogens detected. LCMV is a noteworthy agent of neurologic illness in immunocompetent persons.

Solid organ transplant-associated lymphocytic choriomeningitis, United States, 2011.

Three clusters of organ transplant-associated lymphocytic choriomeningitis virus (LCMV) transmissions have been identified in the United States; 9 of 10 recipients died. In February 2011, we identified a fourth cluster of organ transplant-associated LCMV infections. Diabetic ketoacidosis developed in the organ donor in December 2010; she died with generalized brain edema after a short hospitalization. Both kidneys, liver, and lung were transplanted to 4 recipients; in all 4, severe posttransplant illness developed; 2 recipients died. Through multiple diagnostic methods, we identified LCMV infection in all persons, including in at least 1 sample from the donor and 4 recipients by reverse transcription PCR, and sequences of a 396-bp fragment of the large segment of the virus from all 5 persons were identical. In this cluster, all recipients developed severe illness, but 2 survived. LCMV infection should be considered as a possible cause of severe posttransplant illness.