ETIDIOH - NEW

{Excerpt} Highlights •  A new strain of Lassa virus (LASV) was successfully isolated and characterized. •  The combination of ribavirin and LHF-535 has been demonstrated to exhibit synergistic effects in inhibiting LASV. •  The findings provide new directions for the development of antiviral drugs and vaccines for Lassa fever. Dear Editor, Lassa virus (LASV) is the causative agent of the acute viral hemorrhagic Lassa fever (LF), which is classified into Mammarenavirus within the Arenaviridae family , with a single-stranded, negative-sense, bi-segmented RNA genome. Due to its high pathogenicity and lethality , LASV is considered as a priority threat to public health , with an estimated cases of 300,000 infections and 5,000 deaths annually . LASV was first isolated and described as a clinical entity in 1969 in Lassa, Nigeria (Garry, 2023). LASV isolates of different geographic and host origins are highly diverse in genomic sequences and phylogenetically classified into up t...

Significance Anti-influenza therapeutics remain essential for the control of influenza infections , which may require hospitalization for the most severe cases. Hemagglutinin (HA) and neuraminidase (NA), the two membrane glycoproteins of the influenza virus, play crucial roles in the viral replication cycle. While many monoclonal antibodies and small-molecule inhibitors target HA or NA, each faces limitations tied to their individual properties. We developed an antibody–drug conjugate (ADC) by covalently linking the NA inhibitor zanamivir to MEDI8852, an HA stem-specific monoclonal antibody . The MEDI8852–zanamivir conjugate targets both HA and NA and offers robust and long-lasting protection in mice against lethal infections with influenza A and B viruses. This approach represents an addition to anti-influenza therapy. Abstract Influenza remains a significant public health threat . Both monoclonal antibodies and small-molecule inhibitors can target the influenza surface glycoproteins ...

Summary Background The substantial burden of post-COVID-19 condition (also known as long COVID) underscores the need for effective pharmacological interventions. Given that viral persistence has been hypothesised as a potential cause of long COVID, antiviral therapy might offer a promising approach to alleviating long COVID symptoms. We therefore investigated the efficacy, safety, and tolerability of nirmatrelvir–ritonavir for treating long COVID. Methods In this phase 2, decentralised, double-blind, randomised controlled trial , adults (aged ≥18 years) from the 48 states across the contiguous USA, with previous documented SARS-CoV-2 infection and long COVID symptoms starting within 4 weeks of initial infection and persisting for at least 12 weeks, were eligible for inclusion. Key exclusion criteria were use of nirmatrelvir–ritonavir within the previous 2 months, CYP3A4-dependent medications, or strong CYP3A4 inducers; acute medical illness such as SARS-CoV-2 infection within the past ...

Abstract Influenza A(H1N1)pdm09 virus carrying an I38N substitution was detected in an untreated teenager in Japan . The I38N mutant virus exhibited reduced susceptibility to baloxavir but remained susceptible to neuraminidase inhibitors and showed reduced growth capability . Monitoring antiviral drug susceptibility of influenza viruses is necessary to aid public health planning and clinical recommendations. Source: US Centers for Disease Control and Prevention,  https://wwwnc.cdc.gov/eid/article/31/5/24-1123_article ____

Highlights •  Phylogenetic analysis of genotype B3.13 and D1.1 across the species. •  Mutations on the receptor binding sites related to receptor preferring. •  Host adaptability differences between B3.13 and D1.1. •  Antivirals resistance mutations emergence of genotype B3.13 and D1.1. Abstract The recent report of the first fatality associated with infection by influenza virus H5N1 clade 2.3.4.4b, identified as genotype D1.1, which is distinct from the B3.13 genotype, has sparked fears of a potential human pandemic . However, the genetic relationships between B3.13 and D1.1, as well as their origins, host adaptability, and antiviral resistance, remain poorly understood . Here we conducted a comprehensive phylogenetic and comparative analysis of H5N1 clade 2.3.4.4b across multiple species , in order to identify the molecular characteristics and frequency of resistance mutations in these two genotypes, elucidate their evolutionary trajectories , and assess their impl...

Abstract In recent years, the influenza viruses have posed an increasingly severe threat to public health . It is essential to analyze the virulence and pathogenesis of influenza viruses to prevent and control them, as well as create antiviral drugs . Previous studies have revealed that influenza virus segment 3 codes for not only the PA protein but also a novel protein, PA-X . PA protein is one subunit of the polymerase of influenza viruses and plays a critical role in its life cycle. PA presented endonuclease activity , the transcription and replication of the viral genome , viral virulence , protein degradation , and host immune response by interacting with viral proteins, including PB2, PB1, and host factors, including ANP32A, CHD6, HAX1, hCLE, HDAC6, MCM complex. PA mutations were involved in the viral replication, pathogenicity, and transmission of influenza viruses in poultry, mammals, and humans . PA-X is an open reading frame generated by +1 ribosomal code shift at the N-termi...

Abstract The coronavirus membrane protein (M) is the main organizer of coronavirus assembly. Here, we report on an M-targeting molecule , CIM-834, that blocks the assembly of SARS-CoV-2. CIM-834 was obtained through high-throughput phenotypic antiviral screening followed by medicinal-chemistry efforts and target elucidation. CIM-834 inhibits the replication of SARS-CoV-2 (including a broad panel of variants) and SARS-CoV. In SCID mice and Syrian hamsters intranasally infected with SARS-CoV-2, oral treatment reduced lung viral titres to nearly undetectable levels, even (as shown in mice) when treatment was delayed until 24 h before the end point. Treatment of infected hamsters prevented transmission to untreated sentinels. Transmission electron microscopy studies show that virion assembly is completely absent in cells treated with CIM-834. Single-particle cryo-electron microscopy reveals that CIM-834 binds and stabilizes the M protein in its short form, thereby preventing the conformati...

Abstract Objective :  To analyze the epidemiological, etiological and genetic characteristics of influenza virus in Shandong Province during 2023-2024.  Methods :  The surveillance data of influenza-like illness (ILI) in sentinel hospitals in Shandong from 2023 to 2024 were collected and analyzed. The isolated influenza strains with hemagglutination titers ≥8 were selected for antigenicity analysis , drug susceptibility test, gene sequencing and evolutionary analysis .  Results :  From 2023 to 2024, the positive rate of influenza virus in Shandong was 8.51% (23 663/277 995), the highest positive rate was in the age group of 5-14 years (15.78%, 6 073/38 478), and the highest positive rate was in the 49th week (35.86%, 2 264/6 313). Both antigenicity analysis and evolutionary analysis showed that the A(H1N1)pdm09 subtype and B(Victoria) strain had good matching effect and close evolutionary distance with the 2023-2024 surveillance year vaccine strain. The A(H3N2) ...

Abstract Pharmacometric assessment of antiviral efficacy in acute influenza informs treatment decisions and pandemic preparedness. We assessed natural viral clearance in untreated acute influenza to guide clinical trial design. Standardized duplicate oropharyngeal swabs were collected daily over 14 days from 80 untreated low-risk Thai adults , with viral densities measured using qPCR. We evaluated three models to describe viral clearance: exponential, bi-exponential, and growth-and-decay . The growth-and-decay model provided the best fit, but the exponential decay model was the most parsimonious. The median viral clearance half-life was 10.3 hours (interquartile range [IQR]: 6.8-15.4), varying by influenza type: 9.6 hours (IQR: 6.2-13.0) for influenza A and 14.0 (IQR: 10.3-19.3) hours for influenza B. Simulated trials using clearance parameters from the exponential decay model, showed that 120 patients per arm provide over 90% power to detect treatments accelerating viral clearance by ...

Abstract The effectiveness of antivirals in mitigating influenza outbreaks depends on both their ability to reduce the number of infections and the risk of drug resistance. We extended a previously developed mathematical model to investigate the impact of mitigation strategies , including mono or combination antiviral treatment or chemoprophylaxis and vaccination , on influenza transmission dynamics. Our findings indicate that chemoprophylaxis is more effective than treatment in reducing influenza burden, except when the resistant strain has a high transmission rate, in which case chemoprophylaxis may trigger a resistance-driven secondary infection wave. Combination therapy considerably reduces resistance emergence with similar infection numbers as mono-therapy. Vaccination coverage of at least 80% is required to prevent outbreaks; otherwise, antivirals can contribute to outbreak control provided drug resistance emergence is low. This analysis could inform public health decision-making...

Abstract Testing approved antivirals against A(H5N1) influenza viruses circulating in peridomestic species, including dairy cows , is critical to public health and pre-pandemic planning . It cannot be tested in humans due to A(H5N1) disease severity. Here, in mice, we demonstrate that US FDA-approved baloxavir treatment mediates improved disease outcomes ( survival and viral dissemination ) over oseltamivir after lethal intranasal and ocular challenge with A(H5N1)-contaminated cow milk. Source: Nature Microbiology,  https://www.nature.com/articles/s41564-025-01961-5 ____

The antiviral drug tecovirimat used without other antivirals did not reduce the time to clinical resolution of clade II mpox lesions or improve pain control among adults in an international clinical trial sponsored by the National Institutes of Health (NIH).  The trial enrollment was stopped in late 2024 when an interim analysis showed that tecovirimat monotherapy was ineffective in the study population. Detailed results were presented at the 2025 Conference on Retroviruses and Opportunistic Infections (CROI) in San Francisco. “This study brought us a step forward in better understanding mpox disease and potential treatment strategies,” said Jeanne Marrazzo, M.D., M.P.H., director of NIH’s National Institute of Allergy and Infectious Diseases (NIAID), which sponsored and funded the trial. “We are grateful to the study team and participants for their contributions to groundbreaking research on a disease that we still do not know enough about.” Mpox is caused by a virus that spreads ...

Abstract During 2023-2024, highly pathogenic avian influenza A(H5N1) viruses from clade 2.3.2.1c caused human infections in Cambodia and from clade 2.3.4.4b caused human infections in the Americas . We assessed the susceptibility of those viruses to approved and investigational antiviral drugs . Except for 2 viruses isolated from Cambodia , all viruses were susceptible to M2 ion channel-blockers in cell culture-based assays. In the neuraminidase inhibition assay , all viruses displayed susceptibility to neuraminidase inhibitor antiviral drugs oseltamivir, zanamivir, peramivir, laninamivir , and AV5080. Oseltamivir was ≈4-fold less potent at inhibiting the neuraminidase activity of clade 2.3.4.4b than clade 2.3.2.1c viruses. All viruses were susceptible to polymerase inhibitors baloxavir and tivoxavir and to polymerase basic 2 inhibitor pimodivir with 50% effective concentrations in low nanomolar ranges. Because drug-resistant viruses can emerge spontaneously or by reassortment, close m...

Abstract Background Influenza is a pervasive respiratory infection which disproportionately burdens long-term care residents. To limit outbreaks, guidelines recommend antiviral prophylaxis, particularly oseltamivir or zanamivir , despite acknowledging the inadequate supporting evidence . Therefore, we aimed to review the literature on the efficacy of oseltamivir, zanamivir, and baloxavir prophylaxis for influenza in long-term care. Methods Medline, Embase, PubMed, and several other databases were searched from inception to August 16, 2023. For inclusion, observational studies or randomized controlled trials (RCTs) had to report influenza-like illness (ILI) or infection rates amongst adult long-term care populations receiving prophylaxis. Outcome values were meta-analyzed as intervention-specific pooled proportions (PPs) and risk ratios (RRs) when applicable. Risk of bias was assessed via the Cochrane risk of bias tool 2.0 and Joanna Briggs Institute checklist. Results In total, 14 stud...

Abstract It is essential to understand the molecular mechanisms of influenza antiviral therapeutics to evaluate their efficacy. Virus plaque assays are commonly used to assess the antiviral effects of drugs on virus replication ; however, this method is labor-intensive and can present challenges. We avoided this method by using a replication-competent influenza A virus (IAV) expressing a reporter fluorescent gene fused to the non-structural protein 1 (NS1) gene. The reporter IAV was detectable in normal human bronchoepithelial (NHBE) infected cells and offered an improved method to determine the therapeutic efficacy of the antiviral drugs probenecid and oseltamivir compared to a standard plaque assay. This method provides an excellent means for evaluating therapeutic approaches against IAV. Source: Viruses,  https://www.mdpi.com/1999-4915/17/3/335 ____

Abstract We report the detection of a clade 2.3.4.4b A(H5N1) reassortant virus with a neuraminidase surface protein derived from a North American lineage low-pathogenic avian influenza virus. This virus caused a widespread and ongoing outbreak across 45 poultry farms in British Columbia, Canada . Isolates from 8 farms reveal a mutation in the neuraminidase protein (H275Y) that is exceptionally rare among clade 2.3.4.4b viruses (present in 0.045% of publicly available clade 2.3.4.4b isolates). NA-H275Y is a well-known marker of resistance to the neuraminidase inhibitor oseltamivir . We demonstrate that this substitution maintains its resistance phenotype on the genetic background of H5N1 clade 2.3.4.4b viruses. Source: Emerging Microbes and Infections,  https://www.tandfonline.com/doi/full/10.1080/22221751.2025.2469643 ____

Abstract To better manage seasonal and pandemic influenza infections , new drugs are needed with enhanced activity against amantadine- and rimantadine-resistant influenza A virus (IAV) strains containing the S31N variant of the viral M2 ion channel (M2S31N). Here we tested 36 amantadine analogs against a panel of viruses containing either M2S31N or the parental, M2 S31 wild-type variant (M2WT). We found that several analogs, primarily those with sizeable lipophilic adducts, inhibited up to three M2S31N-containing viruses with activities at least 5-fold lower than rimantadine, without inhibiting M2S31N proton currents or modulating endosomal pH. While M2WT viruses in passaging studies rapidly gained resistance to these analogs through the established M2 mutations V27A and/or A30T, resistance development was markedly slower for M2S31N viruses and did not associate with additional M2 mutations. Instead, a subset of analogs, exemplified by 2-propyl-2-adamantanamine (38), but not 2-(1-adama...

ABSTRACT In a subset of SARS-CoV-2-infected individuals treated with the antiviral nirmatrelvir -ritonavir, the virus rebounds following treatment. The mechanisms driving this rebound are not well understood. We used a mathematical model to describe the longitudinal viral load dynamics of 51 individuals treated with nirmatrelvir-ritonavir, 20 of whom rebounded. Target cell preservation , either by a robust innate immune response or initiation of N-R near the time of symptom onset, coupled with incomplete viral clearance , appears to be the main factor leading to viral rebound. Moreover, the occurrence of viral rebound is likely influenced by the time of treatment initiation relative to the progression of the infection, with earlier treatments leading to a higher chance of rebound . A comparison with an untreated cohort suggests that early treatments with nirmatrelvir-ritonavir may be associated with a delay in the onset of an adaptive immune response . Nevertheless, our model demonstra...

Abstract SARS-CoV-2 main protease, Mpro , is responsible for processing the viral polyproteins into individual proteins, including the protease itself. Mpro is a key target of anti-COVID-19 therapeutics such as nirmatrelvir (the active component of Paxlovid). Resistance mutants identified clinically and in viral passage assays contain a combination of active site mutations (e.g., E166V, E166A, L167F), which reduce inhibitor binding and enzymatic activity, and non-active site mutations (e.g., P252L, T21I, L50F), which restore the fitness of viral replication. To probe the role of the non-active site mutations in fitness rescue, here we use an Mpro triple mutant (L50F/E166A/L167F) that confers nirmatrelvir drug resistance with a viral fitness level similar to the wild-type. By comparing peptide and full-length Mpro protein as substrates, we demonstrate that the binding of Mpro substrate involves more than residues in the active site. Particularly, L50F and other non-active site mutations...

Summary The 2024 Nipah outbreak in Kerala, India —its fifth in six years—and the recurring annual outbreaks in Bangladesh underscore the persistent threat posed by the Nipah virus (NiV) in the region. With a high mortality rate, human-to-human transmission potential , and the widespread presence of Pteropus bats , the natural reservoir, NiV remains a significant epidemic threat . Despite being a WHO priority pathogen , there has been no systematic effort to improve patient care for NiVD, leading to consistently poor outcomes . Current care relies on supportive measures and the ‘ compassionate use ’ of unapproved drugs like ribavirin and remdesivir . Drugs used ‘off-label’ during outbreaks can become the ‘standard of care’ without robust evidence of their safety or efficacy, complicating the testing of new therapies and perpetuating uncertainty about their true effectiveness. To improve NiVD care, we propose four key strategies: 1) Enhance early case detection , 2) optimize supportive c...