[Challenges and advances in the management of HCMV infections]. / Enjeux et avancées de la prise en charge des infections à CMVH.

Human cytomegalovirus (HCMV) is one of the most important causes of complications in immunocompromised patients and congenital infections. HCMV could also represent an interesting target for treatment to limit the progression of glioblastoma, a highly aggressive tumor. Ganciclovir, foscarnet and cidofovir, which interfere with the activity of the viral polymerase pUL54, are widely used in the treatment of transplant patients. However, their use in pregnant women remains limited or even contraindicated. On the other hand, hyperimmune immunoglobulins and valaciclovir have been shown to have a protective effect on the fetus. However, the toxicity of these treatments and the emergence of resistance mean that new therapeutic strategies need to be identified. Letermovir and maribavir have been developed to inhibit new targets, respectively the terminase complex and UL97 protein kinase. Their respective indications are the prevention of HCMV infection in haematopoietic stem cell transplant patients and the treatment of refractory HCMV infections. Finally, with the development of mRNA vaccines, the hope of one day seeing a prophylactic HCMV vaccine has never been greater. New therapeutic approaches are also being explored, but they still require extensive preclinical and clinical evaluation.

Cell-based cccDNA reporter assay combined with functional genomics identifies YBX1 as HBV cccDNA host factor and antiviral candidate target.

OBJECTIVES: Chronic hepatitis B virus (HBV) infection is a leading cause of liver disease and hepatocellular carcinoma. A key feature of HBV replication is the synthesis of the covalently close circular (ccc)DNA, not targeted by current treatments and whose elimination would be crucial for viral cure. To date, little is known about cccDNA formation. One major challenge to address this urgent question is the absence of robust models for the study of cccDNA biology. DESIGN: We established a cell-based HBV cccDNA reporter assay and performed a loss-of-function screen targeting 239 genes encoding the human DNA damage response machinery. RESULTS: Overcoming the limitations of current models, the reporter assay enables to quantity cccDNA levels using a robust ELISA as a readout. A loss-of-function screen identified 27 candidate cccDNA host factors, including Y box binding protein 1 (YBX1), a DNA binding protein regulating transcription and translation. Validation studies in authentic infection models revealed a robust decrease in HBV cccDNA levels following silencing, providing proof-of-concept for the importance of YBX1 in the early steps of the HBV life cycle. In patients, YBX1 expression robustly correlates with both HBV load and liver disease progression. CONCLUSION: Our cell-based reporter assay enables the discovery of HBV cccDNA host factors including YBX1 and is suitable for the characterisation of cccDNA-related host factors, antiviral targets and compounds.

Towards a Prophylactic Vaccine for the Prevention of HCMV Infection.

Human cytomegalovirus (HCMV) or human herpesvirus 5, is a ubiquitous human herpesvirus, which can cause severe disease in immunocompromised patients (AIDS patients and solid organ transplant or hematopoietic stem cell transplant recipients) [...].

Hepatitis B virus-host interactions and novel targets for viral cure.

Chronic infection with HBV is a major cause of advanced liver disease and hepatocellular carcinoma. Nucleos(t)ide analogues effectively control HBV replication but viral cure is rare. Hence treatment has often to be administered for an indefinite duration, increasing the risk for selection of drug resistant virus variants. PEG-interferon-α-based therapies can sometimes cure infection but suffer from a low response rate and severe side-effects. CHB is characterized by the persistence of a nuclear covalently closed circular DNA (cccDNA), which is not targeted by approved drugs. Targeting host factors which contribute to the viral life cycle provides new opportunities for the development of innovative therapeutic strategies aiming at HBV cure. An improved understanding of the host immune system has resulted in new potentially curative candidate approaches. Here, we review the recent advances in understanding HBV-host interactions and highlight how this knowledge contributes to exploiting host-targeting strategies for a viral cure.

Targeting Viral cccDNA for Cure of Chronic Hepatitis B.

Purpose of Review: Chronic hepatitis B (CHB), caused by hepatitis B virus (HBV), is a major cause of advanced liver disease and hepatocellular carcinoma (HCC) worldwide. HBV replication is characterized by the synthesis of covalently closed circular (ccc) DNA which is not targeted by antiviral nucleos(t)ide analogues (NUCs) the key modality of standard of care. While HBV replication is successfully suppressed in treated patients, they remain at risk for developing HCC. While functional cure, characterized by loss of HBsAg, is the first goal of novel antiviral therapies, curative treatments eliminating cccDNA remain the ultimate goal. This review summarizes recent advances in the discovery and development of novel therapeutic strategies and their impact on cccDNA biology. Recent Findings: Within the last decade, substantial progress has been made in the understanding of cccDNA biology including the discovery of host dependency factors, epigenetic regulation of cccDNA transcription and immune-mediated degradation. Several approaches targeting cccDNA either in a direct or indirect manner are currently at the stage of discovery, preclinical or early clinical development. Examples include genome-editing approaches, strategies targeting host dependency factors or epigenetic gene regulation, nucleocapsid modulators and immune-mediated degradation. Summary: While direct-targeting cccDNA strategies are still largely at the preclinical stage of development, capsid assembly modulators and immune-based approaches have reached the clinical phase. Clinical trials are ongoing to assess their efficacy and safety in patients including their impact on viral cccDNA. Combination therapies provide additional opportunities to overcome current limitations of individual approaches.

Highlighting of a LAGLIDADG and a Zing Finger Motifs Located in the pUL56 Sequence Crucial for HCMV Replication.

The human cytomegalovirus (HCMV) terminase complex is part of DNA-packaging machinery that delivers a unit-length genome into a procapsid. Sequence comparison of herpesvirus homologs allowed us to identify a potential LATLNDIERFL and zinc finger pattern in N-terminal part of pUL56. Recombinant viruses were generated with specific serine or alanine substitutions in these putative patterns. We identified a LATLNDIERFL pattern characteristic of LAGLIDADG homing endonucleases and a metal-binding pattern involving the cysteine and histidine residues C191-X2-C194-X22-C217-X-H219 (CCCH) close to the region conferring letermovir resistance. These patterns are crucial for viral replication, suggesting that they are essential for pUL56 structure and function. Thus, these patterns represent potential targets for the development of new antivirals such as small molecules or peptides and may allow to better understand the letermovir mechanism of action.

Hepatitis C Virus (HCV)-Apolipoprotein Interactions and Immune Evasion and Their Impact on HCV Vaccine Design.

With more than 71 million people chronically infected, hepatitis C virus (HCV) is one of the leading causes of liver disease and hepatocellular carcinoma. While efficient antiviral therapies have entered clinical standard of care, the development of a protective vaccine is still elusive. Recent studies have shown that the HCV life cycle is closely linked to lipid metabolism. HCV virions associate with hepatocyte-derived lipoproteins to form infectious hybrid particles that have been termed lipo-viro-particles. The close association with lipoproteins is not only critical for virus entry and assembly but also plays an important role during viral pathogenesis and for viral evasion from neutralizing antibodies. In this review, we summarize recent findings on the functional role of apolipoproteins for HCV entry and assembly. Furthermore, we highlight the impact of HCV-apolipoprotein interactions for evasion from neutralizing antibodies and discuss the consequences for antiviral therapy and vaccine design. Understanding these interactions offers novel strategies for the development of an urgently needed protective vaccine.