Quentin Lepiller

Neutralizing Antibodies and Pathogenesis of Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide. The interplay between the virus and host innate and adaptive immune responses determines the outcome of infection. There is increasing evidence that host neutralizing responses play a relevant role in the resulting pathogenesis. Furthermore, viral evasion from host neutralizing antibodies has been revealed to be an important contributor in leading both to viral persistence in acute liver graft infection following liver transplantation, and to chronic viral infection. The development of novel model systems to study HCV entry and neutralization has allowed a detailed understanding of the molecular mechanisms of virus-host interactions during antibody-mediated neutralization. The understanding of these mechanisms will ultimately contribute to the development of novel antiviral preventive strategies for liver graft infection and an urgently needed vaccine. This review summarizes recent concepts of the role of neutralizing antibodies in viral clearance and protection, and highlights consequences of viral escape from neutralizing antibodies in the pathogenesis of HCV infection.

High Incidence but Low Burden of Coronaviruses and Preferential Associations between Respiratory Viruses

ABSTRACT Respiratory viruses are the leading cause of acute infections in humans. However, the burden of certain respiratory viruses, such as coronaviruses, and the relevance of viral coinfections remain unclear. In this study, we investigated the distribution and seasonal occurrences of respiratory viruses detected by multiplex molecular assay in 6,014 samples from 2008 to 2011 in a French hospital. We assessed the detection frequencies of 14 respiratory viruses and their clinical impact in immunosuppressed and nonimmunosuppressed patients. Furthermore, we explored the preferential association patterns between respiratory viruses in multiple infections. Our results indicated that human rhinovirus/enterovirus (HRV/EV) and coronavirus (HCoV) were frequently detected in respiratory samples (48.81% and 11.74% of infected samples, respectively), and the detection frequencies of these viruses were further increased in immunosuppressed patients. The most common subtypes of HCoV were HCoV-229E (33.80%) and HCoV-HKU1 (32.39%). A sharp increase in the detection frequencies of HCoV-229E and HCoV-HKU1 over several months suggested that these subtypes were epidemic in our population. In immunosuppressed patients, HCoV contributed to upper respiratory tract infections (52%). Evidence did not support lower respiratory tract infections exclusive to a unique HCoV infection. In multiply infected individuals, determined in 6.3% of samples, HRV/EV and HCoV were detected in 33.29% and 22.90% of samples, respectively. Interestingly, nearly 50% of HCoV infections were detected in association with another virus. Since the distributions of respiratory viruses in multiply infected patients were subject to preferential association patterns between viruses, we propose complex interactions between different respiratory viruses and host factors.

Cytomegalovirus and Tumors: Two Players for One Goal-Immune Escape

Cytomegalovirus (CMV) and the human tumor cell share the same objectives: escape the recognition and destruction by the immune system and establish a state of immune tolerance conducive for their development. For early tumor development, the escape of the first lines of defense of the immune surveillance is a critical step which determines survival or destruction. The presence of CMV on the tumor site and its involvement in carcinogenesis as initiator or promoter is increasingly documented. In this article, we highlight the similarity between mechanisms used by tumors and CMV to circumvent the immune defenses and evade from immune surveillance. We suggest that CMV and tumors help one another for their common objective. CMV gets shelter in immunologically poor environment of the tumor cells. In return CMV, by acting directly on the cancer cell and/or on the tumor microenvironment, provides the tumor cell the ways to promote its immune escape and development of immune tolerance.

Antiviral and immunoregulatory effects of indoleamine-2,3-dioxygenase in hepatitis C virus infection

In patients with hepatitis C virus (HCV) infection, enhanced activity of indoleamine-2,3-dioxygenase 1 (IDO) has been reported. IDO - a tryptophan-catabolizing enzyme - has been considered as both an innate defence mechanism and an important regulator of the immune response. The molecular mechanism of IDO induction in HCV infection and its role in the antiviral immune response remain unknown. Using primary human hepatocytes, we show that HCV infection stimulates IDO expression. IDO gene induction was transient and coincided with the expression of types I and III interferons (IFNs) and IFN-stimulated genes in HCV-infected hepatocytes. Overexpression of hepatic IDO prior to HCV infection markedly impaired HCV replication in hepatocytes, suggesting that IDO limits the spread of HCV within the liver. siRNA-mediated IDO knock-down revealed that IDO functions as an IFN-mediated anti-HCV effector. Hepatic IDO was most potently induced by IFN-γ, and ongoing HCV replication could significantly upregulate IDO expression. IRF1 (IFN-regulatory factor 1) and STAT1 (signal transducer and activator of transcription 1) regulated hepatic IDO expression. Hepatic IDO expression also had a significant inhibitory effect on CD4+ T-cell proliferation. Our data suggest that hepatic IDO plays a dual role during HCV infection by slowing down viral replication and also regulating host immune responses.

45 years after the discovery of human polyomaviruses BK and JC: Time to speed up the understanding of associated diseases and treatment approaches

Abstract Nearly 45 years after the discovery of the first two human polyomaviruses BK and JC, their life-long persistence and mechanisms of pathogenesis remain poorly understood and efficient antiviral treatments are severely lacking. In this review, we sought to provide an update on recent advances in understanding the life cycle of these two viruses, particularly focusing on their interaction with the host immune system and pathogenesis. We have also discussed novel treatment approaches and highlighted areas of future research.

Toward Standardization of BK Virus Monitoring: Evaluation of the BK Virus R-gene Kit for Quantification of BK Viral Load in Urine, Whole-Blood, and Plasma Specimens

ABSTRACT Screening of BK virus (BKV) replication is recommended to identify patients at increased risk of BKV-associated diseases. However, the heterogeneity of molecular techniques hinders the establishment of universal guidelines for BKV monitoring. Here we aimed to compare the performance of the CE-marked BK virus R-gene kit (R-gene) to the performance of our in-house assay for quantification of BKV DNA loads (BKVL). A 12-specimen panel from the Quality Control for Molecular Diagnostics (QCMD) organization, 163 urine samples, and 88 paired specimens of plasma and whole blood (WB) from transplant recipients were tested. Both the R-gene and in-house assays showed a good correlation within the QCMD panel (r = 0.995 and r = 0.989, respectively). BKVL were highly correlated between assays, although positive biases were observed with the in-house assay in analysis of urine (0.72 ± 0.83 log10 copies/ml), plasma (1.17 ± 0.63 log10 copies/ml), and WB (1.28 ± 0.37 log10 copies/ml). Recalibration with a common calibrator significantly reduced the bias in comparisons between assays. In contrast, BKVL was underestimated with the in-house PCR in eight samples containing BKV genotype II, presenting point mutations at primer-annealing sites. Using the R-gene assay, plasma and WB specimens were found to be equally suitable for quantification of BKVL, as indicated by the high correlation coefficient (r = 0.965, P < 0.0001). In conclusion, the R-gene assay demonstrated reliable performance and higher accuracy than the in-house assay for quantification of BKVL in urine and blood specimens. Screening of BKV replication by a well-validated commercial kit may enable clinical laboratories to assess viral loads with greater reproducibility and precision.

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.

Congenital Lymphocytic Choriomeningitis Virus: A Case of Prenatal Diagnosis

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343 HUMAN HEPATOCYTE INDOLEAMINE-2,3-DIOXYGENASE CONTRIBUTES TO ANTIVIRAL DEFENSE AND IMMUNE REGULATION IN HEPATITIS C VIRUS INFECTION

(0.89±0.52%) versus blood (0.05±0.01%; p =0.0005) and their numbers correlated with advanced stages of fibrosis (p = 0.022), but not to inflammation. Finally, in vitro supernatants of Tregs induced mRNA up-regulation of profibrogenic markers TIMP1, MMP2, TGFbeta1 and alpha-SMA in resting HSC (p < 0.05 each). Conclusion: Our data demonstrate that in chronic hepatitis C Foxp3CD4 Tregs are enriched in areas of hepatic fibrosis, exhibit up-regulated IL-8 expression and can activate HSC. Thus, in addition to suppression of inflammation adaptive Tregs in hepatitis C play a dual role as regulators of fibrogenesis.