Treatment of influenza with neuraminidase inhibitors

Identification of catalytically active domain epitopes in neuraminidase protein of H9N2 subtype of avian influenza virus

H9N2 subtype of avian influenza virus (AIV) is primarily a bird virus, which is widespread in clinical avian disease, and reported in cases of human infection. As one of the surface proteins of AIV, the neuraminidase (NA) protein plays an important role mainly in viral budding. However, vaccine development and detection methods for NA of H9N2 AIVs are in urgent clinical need. In this study, a truncated NA gene (205-900 bp) was cloned from the NA sequence of H9N2 strain, and then expressed using pET-28a (+) vector. This purified recombinant NA protein was used to immunize BALB/c mice, and the monoclonal antibodies were screened through the indirect enzyme-linked immunosorbent assay (ELISA). Next, eight prokaryotic expression vectors were constructed for epitope identification. After cell fusion, three hybridoma cell lines producing the antibodies special to NA protein were screened by ELISA, western blotting, and indirect immunofluorescence; these were named 1B10, 2B6, and 5B2, respectively. Epitope scanning techniques were used to identify three B-cell epitopes recognized by these three monoclonal antibodies, 196KNATASIIYDGMLVD210, 210DSIGSWSKNIL220 and 221RTQESECVCI230. The subsequent homology analysis revealed the three epitopes were highly conserved in H9N2 AIV strains. The structural predictions of the antigenic epitopes indicated that all three epitopes were located in the catalytic region of NA. These results provide a basis for studying the function of the NA protein of H9N2 AIV and technical support for the development of a universal detection method based on anti-NA monoclonal antibodies.

Polydopamine-based nanomedicines for efficient antiviral and secondary injury protection therapy

Viral infections continue to threaten human health. It remains a major challenge to efficiently inhibit viral infection while avoiding secondary injury. Here, we designed a multifunctional nanoplatform (termed as ODCM), prepared by oseltamivir phosphate (OP)-loaded polydopamine (PDA) nanoparticles camouflaged by the macrophage cell membrane (CM). OP can be efficiently loaded onto the PDA nanoparticles through the π-π stacking and hydrogen bonding interactions with a high drug-loading rate of 37.6%. In particular, the biomimetic nanoparticles can accumulate actively in the damaged lung model of viral infection. At the infection site, PDA nanoparticles can consume excess reactive oxygen species and be simultaneously oxidized and degraded to achieve controlled release of OP. This system exhibits enhanced delivery efficiency, inflammatory storm suppression, and viral replication inhibition. Therefore, the system exerts outstanding therapeutic effects while improving pulmonary edema and protecting lung injury in a mouse model of influenza A virus infection.

Iterative Optimization and Structure-Activity Relationship Studies of Oseltamivir Amino Derivatives as Potent and Selective Neuraminidase Inhibitors via Targeting 150-Cavity

With our continuous endeavors in seeking neuraminidase (NA) inhibitors, we reported herein three series of novel oseltamivir amino derivatives with the goal of exploring the druggable chemical space inside the 150-cavity of influenza virus NAs. Among them, around half of the compounds in series C were demonstrated to be better inhibitors against both wild-type and oseltamivir-resistant group-1 NAs than oseltamivir carboxylate (OSC). Notably, compounds 12d, 12e, 15e, and 15i showed more potent or equipotent antiviral activity against H1N1, H5N1, and H5N8 viruses compared to OSC in cellular assays. Furthermore, compounds 12e and 15e exhibited high metabolic stability in human liver microsomes (HLMs) and low inhibitory effect on main cytochrome P450 (CYP) enzymes, as well as low acute/subacute toxicity and certain antiviral efficacy in vivo. Also, pharmacokinetic (PK) and molecular docking studies were performed. Overall, 12e and 15e possess great potential to serve as anti-influenza candidates and are worthy of further investigation.

An affinity interaction guided two-dimensional separation system for the screening of neuraminidase inhibitors from Reynoutria japonica Houtt. roots

Discovering bioactive compounds from medicinal herbs is crucial for drug discovery. Ultrafiltration is often used in the screening of bioactive compounds from natural herbs because of its simple and rapid operations. However, the ultrafiltration results are often disturbed by the undissolved compounds and the non-target compounds, which reduces the accuracy of the results. Herein, an affinity interaction guided two-dimensional (2D) separation system was developed. Discovery of the potential neuraminidase (NA) inhibitors from the dried roots of Reynoutria japonica Houtt. (RRJ) was used as an example. Only the small molecules showing affinity interaction with NA could be screened by the affinity interaction guided 2D separation system. Firstly, the NA and crude extract were incubated to form a sample solution (containing NA-inhibitor complexes, NA, and three types of small molecules with different polarities) by affinity interaction. Then the sample solution was separated and detected by the 2D separation system. This aimed to reduce the interference of the undissolved compounds and non-target compounds, and pick out the NA-inhibitor complexes (NA-Is). The collected NA-Is were denatured to release small molecular inhibitors (Is) for LC-MS/MS analysis. Compared with the ultrafiltration, more obvious peak area differences were observed in the results, and four potential NA inhibitors were successfully identified. In all, we provided a simple strategy with better performance in the screening of natural bioactive compounds.

The Dual Role of CCR5 in the Course of Influenza Infection: Exploring Treatment Opportunities

Influenza is one of the most relevant respiratory viruses to human health causing annual epidemics, and recurrent pandemics. Influenza disease is principally associated with inappropriate activation of the immune response. Chemokine receptor 5 (CCR5) and its cognate chemokines CCL3, CCL4 and CCL5 are rapidly induced upon influenza infection, contributing to leukocyte recruitment into the airways and a consequent effective antiviral response. Here we discuss the existing evidence for CCR5 role in the host immune responses to influenza virus. Complete absence of CCR5 in mice revealed the receptor’s role in coping with influenza via the recruitment of early memory CD8+ T cells, B cell activation and later recruitment of activated CD4+ T cells. Moreover, CCR5 contributes to inflammatory resolution by enhancing alveolar macrophages survival and reprogramming macrophages to pro-resolving phenotypes. In contrast, CCR5 activation is associated with excessive recruitment of neutrophils, inflammatory monocytes, and NK cells in models of severe influenza pneumonia. The available data suggests that, while CCL5 can play a protective role in influenza infection, CCL3 may contribute to an overwhelming inflammatory process that can harm the lung tissue. In humans, the gene encoding CCR5 might contain a 32-base pair deletion, resulting in a truncated protein. While discordant data in literature regarding this CCR5 mutation and influenza severity, the association of CCR5delta32 and HIV resistance fostered the development of different CCR5 inhibitors, now being tested in lung inflammation therapy. The potential use of CCR5 inhibitors to modulate the inflammatory response in severe human influenza infections is to be addressed.

Replication and transmission of an influenza A(H3N2) virus harboring the polymerase acidic I38T substitution, in guinea pigs

The polymerase acidic (PA) I38T substitution is a dominant marker of resistance to baloxavir. We evaluated the impact of I38T on the fitness of a contemporary influenza A(H3N2) virus. Influenza A/Switzerland/9715293/2013 (H3N2) wild-type (WT) virus and its I38T mutant were rescued by reverse genetics. Replication kinetics were compared using ST6GalI-MDCK and A549 cells and infectivity/contact transmissibility were evaluated in guinea pigs. Nasal wash (NW) viral titres were determined by TCID50 ml^-1 in ST6GalI-MDCK cells. Competition experiments were performed and the evolution of viral population was assessed by droplet digital RT-PCR. I38T did not alter in vitro replication. I38T induced comparable titres vs the WT in guinea pigs NWs and the two viruses transmitted equally by direct contact. However, a 50 %:50 % mixture inoculum evolved to mean WT/I38T ratios of 71 %:29 % and 66.4 %:33.6 % on days 4 and 6 p.i., respectively. Contemporary influenza A(H3N2)-I38T PA variants may conserve a significant level of viral fitness.

The use of antiviral drugs in children

Viral infections are particularly common among children. They often have a mild course, are self-limiting and do not need any specific treatment. However, in some cases, the disease can be severe and lead to permanent disabilities. A variety of antiviral drugs are available for the treatments of certain infectious agents: for instance, acyclovir is used to treat herpes simplex virus encephalitis. Recommendations for flu treatment may change according to the current epidemiological surveillance data, on the basis of which antiviral sensibility can be forecast: recommended drugs for the 2020-21 flu season are oseltamivir, zanamivir, peramivir and baloxavir. Some drugs are used to treat congenital infections, such as valganciclovir and ganciclovir in congenital cytomegalovirus infection. Antiretroviral prophylaxis in newborns from HIV-1 infected mothers must be initiated as soon as possible, with one or more drugs according to therapeutic regimens based on the baby's risk category. According to the most recent guidelines, antiretroviral therapy must be started at diagnosis. Several antiretroviral drugs are available today and approved for use in children, so several combinations can be made. However, out of the 29 antiretroviral drugs approved for adults, only 38% (11/29) are approved for children under the age of two and about 60% (18/29) for children under the age of twelve. Treatment with direct antiviral agents against hepatitis C virus is approved for children over the age of three; it consists in different therapeutic regimens chosen on the basis of the viral genotype (ledipasvir/sofosbuvir for genotypes 1, 4, 5 and 6, sofosbuvir/ribavirin for genotypes 2 and 3, sofosbuvir/velpatasvir and glecaprevir/pibrentasvir for all genotypes) and it has dramatically changed the course of the illness. Many molecules have been studied in order to treat SARS-CoV-2 infection, but only remdesivir seems to play a role in shortening recovery time, although inclusion criteria are very specific and data on the use in children is limited.

Effects of Different Drug Combinations in Immunodeficient Mice Infected with an Influenza A/H3N2 Virus

The prolonged treatment of immunosuppressed (IS) individuals with anti-influenza monotherapies may lead to the emergence of drug-resistant variants. Herein, we evaluated oseltamivir and polymerase inhibitors combinations against influenza A/H3N2 infections in an IS mouse model. Mice were IS with cyclophosphamide and infected with 3 × 10³ PFU of a mouse-adapted A/Switzerland/9715293/2013 (H3N2) virus. Forty-eight hours post-infection, the animals started oseltamivir, favipiravir or baloxavir marboxil (BXM) as single or combined therapies for 10 days. Weight losses, survival rates and lung viral titers (LVTs) were determined. The neuraminidase (NA) and polymerase genes from lung viral samples were sequenced. All untreated animals died. Oseltamivir and favipiravir monotherapies only delayed mortality (the mean day to death (MDD) of 21.4 and 24 compared to 11.4 days for those untreated) while a synergistic improvement in survival (80%) and LVT reduction was observed in the oseltamivir/favipiravir group compared to the oseltamivir group. BXM alone or in double/triple combination provided a complete protection and significantly reduced LVTs. Oseltamivir and BXM monotherapies induced the E119V (NA) and I38T (PA) substitutions, respectively, while no resistance mutation was detected with combinations. We found that the multiple dose regimen of BXM alone provided superior benefits compared to oseltamivir and favipiravir monotherapies. Moreover, we suggest the potential for drug combinations to reduce the incidence of resistance.

In Vitro Profiling of Laninamivir-Resistant Substitutions in N3 to N9 Avian Influenza Virus Neuraminidase Subtypes and Their Association with In Vivo Susceptibility

Laninamivir (LAN) is a long-acting neuraminidase (NA) inhibitor (NAI) with a similar binding profile in the influenza NA enzyme active site as those of other NAIs, oseltamivir (OS), zanamivir (ZAN), and peramivir, and may share common resistance markers with these NAIs. We screened viruses with NA substitutions previously found during OS and ZAN selection in avian influenza viruses (AIVs) of the N3 to N9 subtypes for LAN susceptibility. Of the 72 NA substitutions, 19 conferred resistance to LAN, which ranged from 11.2- to 549.8-fold-decreased inhibitory activity over that of their parental viruses. Ten NA substitutions reduced the susceptibility to all four NAIs, whereas the remaining 26 substitutions yielded susceptibility to one or more NAIs. To determine whether the in vitro susceptibility of multi-NAI-resistant AIVs is associated with in vivo susceptibility, we infected BALB/c mice with recombinant AIVs with R292K (ma81K-N3_R292K) or Q136K (ma81K-N8_Q136K) NA substitutions, which impart in vitro susceptibility only to LAN or OS, respectively. Both ma81K-N3_R292K and ma81K-N8_Q136K virus-infected mice exhibited reduced weight loss, mortality, and lung viral titers when treated with their susceptible NAIs, confirming the in vitro susceptibility of these substitutions. Together, LAN resistance profiling of AIVs of a range of NA subtypes improves the understanding of NAI resistance mechanisms. Furthermore, the association of in vitro and in vivo NAI susceptibility indicates that our models are useful tools for monitoring NAI susceptibility of AIVs.IMPORTANCE The chemical structures of neuraminidase inhibitors (NAIs) possess similarities, but slight differences can result in variable susceptibility of avian influenza viruses (AIVs) carrying resistance-associated NA substitutions. Therefore, comprehensive susceptibility profiling of these substitutions in AIVs is critical for understanding the mechanism of antiviral resistance. In this study, we profiled resistance to the anti-influenza drug laninamivir in AIVs with substitutions known to impart resistance to other NAIs. We found 10 substitutions that conferred resistance to all four NAIs tested. On the other hand, we found that the remaining 26 NA substitutions were susceptible to at least one or more NAIs and showed for a small selection that in vitro data predicted in vivo behavior. Therefore, our findings highlight the usefulness of screening resistance markers in NA enzyme inhibition assays and animal models of AIV infections.

Clinical Effectiveness of Intravenous Peramivir Compared With Oseltamivir in Patients With Severe Influenza A With Primary Viral Pneumonia: A Randomized Controlled Study

Background

High-quality evidence confirms that the clinical efficacy of peramivir in severe influenza patients with primary viral pneumonia is lacking. To optimize clinical medication, we evaluate the different efficacy between peramivir and oseltamivir in the treatment of severe influenza A with primary viral pneumonia.

Methods

A single-center, randomized, controlled trial was conducted during the Chinese influenza season from December 2018 to April 2019 in patients with severe influenza A with primary viral pneumonia. A total of 40 inpatients were enrolled and treated with either intravenous peramivir (300 mg, once daily for 5 days) or oral oseltamivir (75 mg, twice daily for 5 days).

Results

The duration of influenza virus nucleic acid positivity in the oseltamivir group and the peramivir group was 2.95 days and 2.80 days, respectively. The remission times of clinical symptoms in the oseltamivir group and the peramivir group were 3.90 days and 3.25 days, respectively. In addition, the remission time of cough symptoms in the peramivir group (63.89 hours) was shorter than that in the oseltamivir group (75.53 hours). There was no significant difference between these values (P > .05). The remission time of fever symptoms in the oseltamivir group was 23.67 hours, which was significantly longer than that in the peramivir group (12.32 hours) (P = .034).

Conclusions

Peramivir is no less effective than oseltamivir in the treatment of severe influenza A with primary viral pneumonia, and patients treated with peramivir had significantly shorter remission times of fever symptoms than those treated with oseltamivir.

Predictors and Outcomes of Hospitalization for Influenza: Real-World Evidence from the United States Medicare Population

INTRODUCTION

The purpose of this study was to identify predictors of initial hospitalization and describe the outcomes of high-risk patients hospitalized with influenza.

METHODS

Data were taken from the 5% national US Medicare database from 2012 to 2015. Patients (aged at least 13 years) were required to have at least one diagnosis for influenza and have continuous health plan enrollment for 6 months before (baseline) and 3 months (follow-up) after the date of influenza diagnosis. Patients who died during follow-up were included. Patients were categorized as initially hospitalized if hospitalized within 0-1 day of diagnosis. High-risk initially hospitalized patients were defined as patients aged at least 65 years or those that had a diagnostic code for chronic lung disease, cardiovascular or cerebrovascular disease, or weakened immune system during baseline period. Logistic regression models were developed to determine predictors of initial hospitalization.

RESULTS

The study population included 8127 high-risk patients who were initially hospitalized and 16,784 who were not hospitalized. Among high-risk patients, 89.3% were diagnosed in the emergency room, whereas 7.5% and 3.2% were diagnosed in a physician's office or other Medicare settings, respectively. Chronic obstructive pulmonary disorder, congestive heart failure, chronic kidney disease, older age, being male, other comorbidities, number of comorbidities, and baseline healthcare resource use were the predictors of hospitalization. Median length of stay for the hospitalization was 5.0 days, and the 30-day readmission rate was 14%. All-cause mortality rate was 5.1% during the inpatient stay and 9.2% within 30 days of diagnosis. Hospitalized patients with influenza incurred an increase of $16,568 per patient in total all-cause healthcare costs from pre-influenza to post-influenza diagnosis.

CONCLUSION

The study characterized the burden of hospitalization for influenza and found that hospitalized high-risk patients experience greater comorbidity burden, higher likelihood of multiple inpatient admissions, and costly medical interventions compared to patients who were not hospitalized.

In Vitro Combinations of Baloxavir Acid and Other Inhibitors against Seasonal Influenza A Viruses

Two antiviral classes, the neuraminidase inhibitors (NAIs) and polymerase inhibitors (baloxavir marboxil and favipiravir) can be used to prevent and treat influenza infections during seasonal epidemics and pandemics. However, prolonged treatment may lead to the emergence of drug resistance. Therapeutic combinations constitute an alternative to prevent resistance and reduce antiviral doses. Therefore, we evaluated in vitro combinations of baloxavir acid (BXA) and other approved drugs against influenza A(H1N1)pdm09 and A(H3N2) subtypes. The determination of an effective concentration inhibiting virus cytopathic effects by 50% (EC50) for each drug and combination indexes (CIs) were based on cell viability. CompuSyn software was used to determine synergism, additivity or antagonism between drugs. Combinations of BXA and NAIs or favipiravir had synergistic effects on cell viability against the two influenza A subtypes. Those effects were confirmed using a physiological and predictive ex vivo reconstructed human airway epithelium model. On the other hand, the combination of BXA and ribavirin showed mixed results. Overall, BXA stands as a good candidate for combination with several existing drugs, notably oseltamivir and favipiravir, to improve in vitro antiviral activity. These results should be considered for further animal and clinical evaluations.

Neurological Manifestations of Influenza A (H1N1): Clinical Features, Intensive Care Needs, and Outcome

OBJECTIVES

To describe neurological manifestations in children with Influenza A (H1N1).

METHODS

This retrospective study was conducted in the Pediatric intensive care unit (PICU) and Pediatric Neurology unit of a tertiary care teaching hospital in North India involving children with PCR confirmed Influenza A (H1N1) with neurological manifestations during 2019 outbreak.

RESULTS

Six children (5 females, 1 male) were enrolled. All presented with neurological symptoms (seizures and altered sensorium) accompanied with fever and respiratory symptoms with duration of illness of 2-7 d. The admission Glasgow Coma Scale ranged from 4 to 12. Only 2 cases showed cerebrospinal fluid pleocytosis. Neuroimaging was suggestive of diffuse cerebral edema, acute necrotizing encephalopathy of childhood, and acute disseminated encephalomyelitis. All were treated with Oseltamivir. Four cases had clinical features of raised intracranial pressure (ICP) and were managed in PICU, 3 of them needed mechanical ventilation, 3 needed vasoactive drugs, 3 received 3% saline infusion, 1 underwent invasive ICP monitoring, and 3 (cases 4, 5 and 6) received intravenous methylprednisolone (30 mg/kg) for 5 d. Total duration of hospital stay was 10-30 d. Case 2 expired due to refractory raised ICP. Among survivors, 3 children had residual neurological deficits and the remaining 2 had achieved premorbid condition.

CONCLUSIONS

Influenza A (H1N1) can present with isolated or predominant neurological manifestations which can contribute to poor outcome. The authors suggest to rule out H1N1 in any child who presents with unexplained neurological manifestations during seasonal outbreaks of H1N1.

Influenza-associated mortality in hospital care: a retrospective cohort study of risk factors and impact of oseltamivir in an English teaching hospital, 2016 to 2017

Background

Evidence of an oseltamivir treatment effect on influenza A(H3N2) virus infections in hospitalised patients is incomplete.

Aims

This cohort study aimed to evaluate risk factors for death among PCR-confirmed hospitalised cases of seasonal influenza A(H3N2) of all ages and the impact of oseltamivir.

Methods

Participants included all 332 PCR-confirmed influenza A(H3N2) cases diagnosed between 30 August 2016 and 17 March 2017 in an English university teaching Hospital. Oseltamivir treatment effect on odds of inpatient death was assessed by backward stepwise multivariable logistic regression analysis.

Results

The odds of death were reduced by two thirds (odds ratio (OR): 0.32; 95% confidence interval (CI): 0.11–0.93), in inpatients treated with a standard course of oseltamivir 75 mg two times daily for 5 days – compared with those untreated with oseltamivir, after adjustment for age, sex, current excess alcohol intake, receipt of 2016/17 seasonal influenza vaccine, serum haemoglobin and hospital vs community attribution of acquisition of influenza.

Conclusions

Oseltamivir treatment given according to National Institutes of Clinical Excellence (NICE); United States Centres for Disease Control and Prevention (CDC); Infectious Diseases Society of America (IDSA) and World Health Organization (WHO) guidelines was shown to be effective in reducing the odds of mortality in inpatients with PCR-confirmed seasonal influenza A(H3N2) after adjustment in a busy routine English hospital setting. Our results highlight the importance of hospitals complying with relevant guidelines for prompt seasonal influenza PCR testing and ensuring standard oseltamivir treatment to all PCR-confirmed cases of seasonal influenza.

Seasonal and pandemic influenza: 100 years of progress, still much to learn

Influenza viruses are highly transmissible, both within and between host species. The severity of the disease they cause is highly variable, from the mild and inapparent through to the devastating and fatal. The unpredictability of epidemic and pandemic outbreaks is accompanied but the predictability of seasonal disease in wide areas of the Globe, providing an inexorable toll on human health and survival. Although there have been great improvements in understanding influenza viruses and the disease that they cause, our knowledge of the effects they have on the host and the ways that the host immune system responds continues to develop. This review highlights the importance of the mucosa in defence against infection and in understanding the pathogenesis of disease. Although vaccines have been available for many decades, they remain suboptimal in needing constant redesign and in only providing short-term protection. There are real prospects for improvement in treatment and prevention of influenza soon, based on deeper knowledge of how the virus transmits, replicates and triggers immune defences at the mucosal surface.

Influenza H7N9 Virus Neuraminidase-Specific Human Monoclonal Antibodies Inhibit Viral Egress and Protect from Lethal Influenza Infection in Mice

H7N9 avian influenza virus causes severe infections and might have the potential to trigger a major pandemic. Molecular determinants of human humoral immune response to N9 neuraminidase (NA) proteins, which exhibit unusual features compared with seasonal influenza virus NA proteins, are ill-defined. We isolated 35 human monoclonal antibodies (mAbs) from two H7N9 survivors and two vaccinees. These mAbs react to NA in a subtype-specific manner and recognize diverse antigenic sites on the surface of N9 NA, including epitopes overlapping with, or distinct from, the enzyme active site. Despite recognizing multiple antigenic sites, the mAbs use a common mechanism of action by blocking egress of nascent virions from infected cells, thereby providing an antiviral prophylactic and therapeutic protection in vivo in mice. Studies of breadth, potency, and diversity of antigenic recognition from four subjects suggest that vaccination with inactivated adjuvanted vaccine induce NA-reactive responses comparable to that of H7N9 natural infection.

Investigational antiviral therapies for the treatment of influenza

INTRODUCTION

Influenza viral ribonucleoprotein complexes (vRNPs) play a key role in viral transcription and replication; hence, the recent development of novel anti-influenza drugs targeting vRNPs has garnered widespread interest.

AREAS COVERED

We discuss the function of the constituents of vRNPs and summarize those vRNPs-targeted synthetic drugs that are in preclinical and early clinical development.

EXPERT OPINION

vRNPs contain high-value drug targets; such targets include the subunits PA, PB1, PB2, and NP. Developing a new generation of antiviral therapies with strategies that utilize existing drugs, natural compounds originated from new resources and novel drug combinations may open up new therapeutic approaches to influenza.