Claire Gourin

Glioblastoma (GB) is a highly aggressive brain tumor with a very poor prognosis. Treatment usually consists of surgery, followed by radiotherapy and chemotherapy, but the prognosis remains poor due to its resistance to therapies and a high recurrence rate. Multiple studies have reported the presence of human cytomegalovirus (HCMV) proteins and/or nucleic acids in GB tissues, suggesting its possible implication. These findings have led to the hypothesis that HCMV may contribute to tumor progression, immune evasion, angiogenesis, and resistance to therapy. Clinical trials using anti-HCMV therapies have shown promising preliminary results, indicating a potential therapeutic benefit. This review aims to provide a comprehensive overview of the current evidence linking HCMV to GB and the therapeutic implications. A deeper understanding of this complex interaction could unveil novel strategies for GB treatment.

Human cytomegalovirus (HCMV) is a significant cause of morbidity and mortality in immunocompromised and congenitally infected patients. Current antiviral therapies, primarily targeting the viral DNA polymerase, are limited by toxicity and resistance, underscoring the need for novel therapeutic strategies. Letermovir (LTV), which targets the viral terminase complex (pUL56-pUL89-pUL51), has improved prophylaxis in transplant recipients, but resistance mutations have already emerged. This complex is responsible for cleaving and packaging the viral genome into neo-formed capsids in close interaction with several other proteins. This study focuses on two essential terminase-associated proteins, pUL77 and pUL93, investigating their natural polymorphism, mutations arising under LTV prophylaxis, and the functional relevance of their putative nuclear localization signals (NLS). Sequence alignments across 18 herpesviruses revealed conserved and variable regions in both proteins. New mutations emerging in patients treated with LTV did not confer resistance, but the pUL77 R43C mutation, when present with pUL56 C325F, significantly reduces LTV resistance compared to C325F alone. In addition, nuclear localization motifs were assessed in the viral replication context and in autonomous cell production after plasmid transfection and revealed motifs essential for viral replication: ₄₃ RVRKRYLRQ ₅₅ and ₂₂₅ PRWKRV ₂₃₁ in pUL77 and ₅₀₅ RDRRGRLRR ₅₁₃ in pUL93. Finally, AI-based modeling provided some insights into the functions of these motifs for both proteins, notably in interaction with other viral proteins. Collectively, these data provide a wealth of information about putative functional sites in pUL77 and pUL93 that could be new targets for anti-HCMV strategies such as inhibitory peptides. IMPORTANCE: Human cytomegalovirus (HCMV) remains a significant health concern, particularly for immunocompromised individuals and in cases of congenital infection. The emergence of resistance to current antivirals targeting viral polymerase has necessitated the development of novel therapeutic approaches. Letermovir, which targets the HCMV terminase complex, represents a promising alternative. However, a deeper understanding of the virus’s structural components and their interactions is crucial for identifying new potential drug targets. Here, we focused on two proteins, pUL77 and pUL93, which are associated with the viral capsid and interact with the terminase complex. By analyzing their polymorphism, structure, and functional motifs, we identified essential nuclear localization motifs and conserved regions in these proteins, providing valuable insights for the development of innovative anti-HCMV strategies, such as inhibitory peptides, which could complement existing treatments and address the ongoing challenge of antiviral resistance.

Human cytomegalovirus (HCMV) is one of the main causes of serious complications in immunocompromised patients and after congenital infection. There are currently drugs available to treat HCMV infection, targeting viral polymerase, whose use is complicated by toxicity and the emergence of resistance. Maribavir and letermovir are the latest antivirals to have been developed with other targets. The approval of letermovir represents an important innovation for CMV prevention in hematopoietic stem cell transplant recipients, whereas maribavir allowed improving the management of refractory or resistant infections in transplant recipients. However, in case of multidrug resistance or for the prevention and treatment of congenital CMV infection, finding new antivirals or molecules able to inhibit CMV replication with the lowest toxicity remains a critical need. This review presents a range of molecules known to be effective against HCMV. Molecules with a direct action against HCMV include brincidofovir, cyclopropavir and anti-terminase benzimidazole analogs. Artemisinin derivatives, quercetin and baicalein, and anti-cyclooxygenase-2 are derived from natural molecules and are generally used for different indications. Although they have demonstrated indirect anti-CMV activity, few clinical studies were performed with these compounds. Immunomodulating molecules such as leflunomide and everolimus have also demonstrated indirect antiviral activity against HCMV and could be an interesting complement to antiviral therapy. The efficacy of anti-CMV immunoglobulins are discussed in CMV congenital infection and in association with direct antiviral therapy in heart transplanted patients. All molecules are described, with their mode of action against HCMV, preclinical tests, clinical studies and possible resistance. All these molecules have shown anti-HCMV potential as monotherapy or in combination with others. These new approaches could be interesting to validate in clinical trials.

Human cytomegalovirus (HCMV) can cause serious diseases in immunocompromised patients. Current antiviral inhibitors all target the viral DNA polymerase. They have adverse effects, and prolonged treatment can select for drug resistance mutations. Thus, new drugs targeting other stages of replication are an urgent need. The terminase complex (pUL56–pUL89–pUL51) is highly specific, has no counterpart in the human organism, and thus represents a target of choice for new antivirals development. This complex is required for DNA processing and packaging. pUL52 was shown to be essential for the cleavage of concatemeric HCMV DNA and crucial for viral replication, but its functional domains are not yet identified. Polymorphism analysis was performed by sequencing UL52 from 61 HCMV naive strains and from 14 HCMV strains from patients treated with letermovir. Using sequence alignment and homology modeling, we identified conserved regions and potential functional motifs within the pUL52 sequence. Recombinant viruses were generated with specific serine or alanine substitutions in these putative patterns. Within conserved regions, we identified residues essential for viral replication probably involved in CXXC-like or zinc finger motifs. These results suggest that they are essential for pUL52 structure/function. Thus, these patterns represent potential targets for the development of new antivirals.