Inhibition of Measles Viral Fusion Is Enhanced by Targeting Multiple Domains of the Fusion Protein

Clinical features, pathogenesis, pathology, neuroimaging, clinical course and outcome of measles inclusion-body encephalitis: a systematic review of published case reports and case series

Measles inclusion-body encephalitis (MIBE) is rare, with insights largely from case studies. We systematically analyzed subacute Sclerosing Panencephalitis (SSPE) cases in immunocompromised patients, identifying distinctive clinical and neuroimaging features. These findings could facilitate MIBE diagnosis without the need for brain biopsies. Our systematic review on MIBE and HIV-related SSPE adhered to PRISMA guidelines and was registered with PROSPERO. We searched multiple databases and followed a detailed inclusion process with independent reviews and quality assessment. Data on patient demographics, clinical features, and outcomes were compiled. A review of 39 studies on 49 MIBE patients and 8 reports on HIV-positive SSPE patients was conducted. Acute lymphoblastic leukemia, HIV, organ transplants, and malignancies were common precursors to MIBE. Perinatal HIV was prevalent among SSPE cases. Seizures were the primary symptom in MIBE, often drug-resistant and progressing to status epilepticus or epilepsia partialis continua, whereas periodic myoclonus was universal in SSPE. Neuroimaging showed distinct patterns for each group, and histopathology confirmed measles virus presence in 39% of MIBE cases. MIBE patients typically progressed to coma and death. In conclusion, MIBE and SSPE in HIV-infected patients present with distinct clinical pictures but identical brain pathological abnormalities.

A neutralizing antibody prevents postfusion transition of measles virus fusion protein

Measles virus (MeV) presents a public health threat that is escalating as vaccine coverage in the general population declines and as populations of immunocompromised individuals, who cannot be vaccinated, increase. There are no approved therapeutics for MeV. Neutralizing antibodies targeting viral fusion are one potential therapeutic approach but have not yet been structurally characterized or advanced to clinical use. We present cryo-electron microscopy (cryo-EM) structures of prefusion F alone [2.1-angstrom (Å) resolution], F complexed with a fusion-inhibitory peptide (2.3-Å resolution), F complexed with the neutralizing and protective monoclonal antibody (mAb) 77 (2.6-Å resolution), and an additional structure of postfusion F (2.7-Å resolution). In vitro assays and examination of additional EM classes show that mAb 77 binds prefusion F, arrests F in an intermediate state, and prevents transition to the postfusion conformation. These structures shed light on antibody-mediated neutralization that involves arrest of fusion proteins in an intermediate state.

Structure and function of a novel lineage-specific neutralizing epitope on H protein of canine distemper virus

Canine distemper virus (CDV) infects many sensitive species worldwide and its host range is expanding. The hemagglutinin (H) protein, the major neutralizing target, binds to cellular receptors and subsequently triggers fusion for initial viral infection. So it's necessary to clarify the precise neutralizing epitopes of H protein and extend the knowledge of mechanisms of virus neutralization. In this study, a neutralizing monoclonal antibody (mAb) 2D12 against CDV H protein, which had different reactivity with different CDV strains, was generated and characterized. A series of truncated H proteins were screened to define the minimal linear epitope 238DIEREFD244 recognized by 2D12. Further investigation revealed that the epitope was highly conserved in America-1 vaccine lineage of CDV strains, but different substitutions in the epitope appeared in CDV strains of the other lineages and two substitutions (D238Y and R241G) caused the change of antigenicity. Thus, the epitope represents a novel lineage-specific neutralizing target on H protein of CDV for differentiation of America-1 vaccine lineage and the other lineages of CDV strains. The epitope was identified to localize at the surface of H protein in two different positions in a three-dimensional (3D) structure, but not at the position of the receptor-binding site (RBS), so the mAb 2D12 that recognized the epitope did not inhibit binding of H protein to the receptor. But mAb 2D12 interfered with the H-F interaction for inhibiting membrane fusion, suggesting that the mAb plays key roles for formation of H-F protein oligomeric structure. Our data will contribute to the understanding of the structure, function, and antigenicity of CDV H protein and mechanisms of virus neutralization.

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitor, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, blocks respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We use a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptide to the respiratory tract and demonstrate the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevents MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional means to fight against respiratory infection in non-vaccinated people, that can be readily translated to human trials. It presents a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure.

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitors, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, block respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We used a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptides to the respiratory tract and demonstrated the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevented MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional shield which complements vaccination to fight against respiratory infection, presenting a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure, that can be readily translated to human trials.

Repurposing an In Vitro Measles Virus Dissemination Assay for Screening of Antiviral Compounds

Measles virus (MV) is a highly contagious respiratory virus responsible for outbreaks associated with significant morbidity and mortality among children and young adults. Although safe and effective measles vaccines are available, the COVID-19 pandemic has resulted in vaccination coverage gaps that may lead to the resurgence of measles when restrictions are lifted. This puts individuals who cannot be vaccinated, such as young infants and immunocompromised individuals, at risk. Therapeutic interventions are complicated by the long incubation time of measles, resulting in a narrow treatment window. At present, the only available WHO-advised option is treatment with intravenous immunoglobulins, although this is not approved as standard of care. Antivirals against measles may contribute to intervention strategies to limit the impact of future outbreaks. Here, we review previously described antivirals and antiviral assays, evaluate the antiviral efficacy of a number of compounds to inhibit MV dissemination in vitro, and discuss potential application in specific target populations. We conclude that broadly reactive antivirals could strengthen existing intervention strategies to limit the impact of measles outbreaks.

Antiviral peptide engineering for targeting membrane-enveloped viruses: Recent progress and future directions

Membrane-enveloped viruses are a major cause of global health challenges, including recent epidemics and pandemics. This mini-review covers the latest efforts to develop membrane-targeting antiviral peptides that inhibit enveloped viruses by 1) preventing virus-cell fusion or 2) disrupting the viral membrane envelope. The corresponding mechanisms of antiviral activity are discussed along with peptide engineering strategies to modulate membrane-peptide interactions in terms of potency and selectivity. Application examples are presented demonstrating how membrane-targeting antiviral peptides are useful therapeutics and prophylactics in animal models, while a stronger emphasis on biophysical concepts is proposed to refine mechanistic understanding and support potential clinical translation.

Computational methods to study enveloped viral entry

The protein-membrane interactions that mediate viral infection occur via loosely ordered, transient assemblies, creating challenges for high-resolution structure determination. Computational methods and in particular molecular dynamics simulation have thus become important adjuncts for integrating experimental data, developing mechanistic models, and suggesting testable hypotheses regarding viral function. However, the large molecular scales of virus-host interaction also create challenges for detailed molecular simulation. For this reason, continuum membrane models have played a large historical role, although they have become less favored for high-resolution models of protein assemblies and lipid organization. Here, we review recent progress in the field, with an emphasis on the insight that has been gained using a mixture of coarse-grained and atomic-resolution molecular dynamics simulations. Based on successes and challenges to date, we suggest a multiresolution strategy that should yield the best mixture of computational efficiency and physical fidelity. This strategy may facilitate further simulations of viral entry by a broader range of viruses, helping illuminate the diversity of viral entry strategies and the essential common elements that can be targeted for antiviral therapies.