Influenza, SARS-CoV-2, and Their Impact on Chronic Lung Diseases and Fibrosis: Exploring Therapeutic Options

Respiratory tract infections represent a significant global public health concern, disproportionately affecting vulnerable populations such as children, the elderly, and immunocompromised individuals. RNA viruses, particularly influenza viruses and coronaviruses, significantly contribute to respiratory illnesses, especially in immunosuppressed and elderly individuals. Influenza A viruses (IAVs) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to pose global health threats due to their capacity to cause annual epidemics, with profound implications for public health. In addition, the increase in global life expectancy is influencing the dynamics and outcomes of respiratory viral infections. Understanding the molecular mechanisms by which IAVs and SARS-CoV-2 contribute to lung disease progression is therefore crucial. The aim of this review was to comprehensively explore the impact of IAVs and SARS-CoV-2 on chronic lung diseases, with a specific focus on pulmonary fibrosis in the elderly. It also outlines potential preventive and therapeutic strategies and suggests directions for future research.

A systemic review on medicinal plants and their bioactive constituents against avian influenza and further confirmation through in-silico analysis

Background

Avian influenza or more commonly known as bird flu is a widespread infectious disease in poultry. This review aims to accumulate information of different natural plant sources that can aid in combating this disease. Influenza virus (IV) is known for its ability to mutate and infect different species (including humans) and cause fatal consequences.

Methods

Total 33 plants and 4 natural compounds were identified and documented. Molecular docking was performed against the target viral protein neuraminidase (NA), with some plant based natural compounds and compared their results with standard drugs Oseltamivir and Zanamivir to obtain novel drug targets for influenza in chickens.

Results

It was seen that most extracts exhibit their action by interacting with viral hemagglutinin or neuraminidase and inhibit viral entry or release from the host cell. Some plants also interacted with the viral RNA replication or by reducing proinflammatory cytokines. Ethanol was mostly used for extraction. Among all the plants Theobroma cacao, Capparis Sinaica Veil, Androgarphis paniculate, Thallasodendron cillatum, Sinularia candidula, Larcifomes officinalis, Lenzites betulina, Datronia molis, Trametes gibbose exhibited their activity with least concentration (below 10 μg/ml). The dockings results showed that some natural compounds (5,7- dimethoxyflavone, Aloe emodin, Anthocyanins, Quercetin, Hemanthamine, Lyocrine, Terpenoid EA showed satisfactory binding affinity and binding specificity with viral neuraminidase compared to the synthetic drugs.

Conclusion

This review clusters up to date information of effective herbal plants to bolster future influenza treatment research in chickens. The in-silico analysis also suggests some potential targets for future drug development but these require more clinical analysis.

Influenza Treatment: Limitations of Antiviral Therapy and Advantages of Drug Combination Therapy

Influenza infection is serious and debilitating for humans and animals. The influenza virus undergoes incessant mutation, segment recombination, and genome reassortment. As a result, new epidemics and pandemics are expected to emerge, making the elimination challenging of the disease. Antiviral therapy has been used for the treatment of influenza since the development of amantadine in the 1960s; however, its use is hampered by the emergence of novel strains and the development of drug resistance. Thus, combinational therapy with two or more antivirals or immunomodulators with different modes of action is the optimal strategy for the effective treatment of influenza infection. In this review, we describe current options for combination therapy, their performance, and constraints imposed by resistance, calling attention to the advantages of combination therapy against severe influenza infections. We also discuss the challenges of influenza therapy and the limitations of approved antiviral drugs.

Anti-SARS-CoV-2 Activity of Adamantanes In Vitro and in Animal Models of Infection

Coronavirus disease 2019 (COVID-19) has had devastating effects worldwide, with particularly high morbidity and mortality in outbreaks on residential care facilities. Amantadine, originally licensed as an antiviral agent for therapy and prophylaxis against influenza A virus, has beneficial effects on patients with Parkinson's disease and is used for treatment of Parkinson's disease, multiple sclerosis, acquired brain injury, and various other neurological disorders. Recent observational data suggest an inverse relationship between the use of amantadine and COVID-19. Adamantanes, including amantadine and rimantadine, are reported to have in vitro activity against severe acute respiratory syndrome coronavirus (SARS-CoV) and, more recently, SARS-CoV-2. We hypothesized that adamantanes have antiviral activity against SARS-CoV-2, including variant strains. To assess the activity of adamantanes against SARS-CoV-2, we used in vitro and in vivo models of infection. We established that amantadine, rimantadine, and tromantadine inhibit the growth of SARS-CoV-2 in vitro in cultured human epithelial cells. While neither rimantadine nor amantadine reduces lung viral titers in mice infected with mouse-adapted SARS-CoV-2, rimantadine significantly reduces viral titers in the lungs in golden Syrian hamsters infected with SARS-CoV-2. In summary, rimantadine has antiviral activity against SARS-CoV-2 in human alveolar epithelial cells and in the hamster model of SARS-CoV-2 lung infection. The evaluation of amantadine or rimantadine in human randomized controlled trials can definitively address applications for the treatment or prevention of COVID-19.

An Influenza Virus Entry Inhibitor Targets Class II PI3 Kinase and Synergizes with Oseltamivir

Two classes of antivirals targeting the viral neuraminidase (NA) and endonuclease are currently the only clinically useful drugs for the treatment of influenza. However, resistance to both antivirals has been observed in clinical isolates, and there was widespread resistance to oseltamivir (an NA inhibitor) among H1N1 viruses prior to 2009. This potential for resistance and lack of diversity for antiviral targets highlights the need for new influenza antivirals with a higher barrier to resistance. In this study, we identified an antiviral compound, M85, that targets host kinases, epidermal growth factor receptor (EGFR), and phosphoinositide 3 class II β (PIK3C2β) and is not susceptible to resistance by viral mutations. M85 blocks endocytosis of influenza viruses and inhibits a broad-spectrum of viruses with minimal cytotoxicity. In vitro, we found that combinations of M85 and oseltamivir have strong synergism. In the mouse model for influenza, treatment with the combination therapy was more protective against a lethal viral challenge than oseltamivir alone, indicating that development of M85 could lead to combination therapies for influenza. Finally, through this discovery of M85 and its antiviral mechanism, we present the first description of PIK3C2β as a necessary host factor for influenza virus entry.

Amantadine resistance markers among low pathogenic avian influenza H9N2 viruses isolated from poultry in India, during 2009-2017

Antiviral susceptibility screening of avian influenza (AI) H9N2 viruses is crucial considering their role at the animal-human interface and potential to cause human infections. The Matrix 2 (M2) inhibitors (amantadine and rimantadine) have been used for prophylaxis and treatment of influenza A virus infections, however, resistance to these drugs has been widely reported. Information about amantadine susceptibility of H9N2 viruses from India is scanty. Matrix genes of 48H9N2 viruses isolated from India during 2009-2017 were sequenced and M2 trans-membrane region sequences were screened for mutations which are known to confer resistance to amantadine namely, L26F, V27A, A30 T/V, S31N and G34E. All the viruses isolated during the year 2009 were sensitive to amantadine. However, resistance started to appear since the year 2010 and all the viruses isolated from the year 2015 onwards showed presence of molecular markers conferring resistance to amantadine. Majority of the resistant viruses exhibited S31 N mutation. Four isolates showed presence of V27A + S31 N dual mutations. Comparison of the M2 sequences from other Asian countries showed different patterns of amantadine resistance wherein phylogenetic analysis of the M genes of the strains from Pakistan formed a separate cluster. In conclusion, the present study reports prevalence and gradual increase of amantadine resistance among AI H9N2 viruses in India, emphasizing the importance of the antiviral surveillance.

Investigating Different Mechanisms of Action in Combination Therapy for Influenza

Combination therapy for influenza can have several benefits, from reducing the emergence of drug resistant virus strains to decreasing the cost of antivirals. However, there are currently only two classes of antivirals approved for use against influenza, limiting the possible combinations that can be considered for treatment. However, new antivirals are being developed that target different parts of the viral replication cycle, and their potential for use in combination therapy should be considered. The role of antiviral mechanism of action in the effectiveness of combination therapy has not yet been systematically investigated to determine whether certain antiviral mechanisms of action pair well in combination. Here, we use a mathematical model of influenza to model combination treatment with antivirals having different mechanisms of action to measure peak viral load, infection duration, and synergy of different drug combinations. We find that antivirals that lower the infection rate and antivirals that increase the duration of the eclipse phase perform poorly in combination with other antivirals.

Zoonotic Influenza and Human Health-Part 2: Clinical Features, Diagnosis, Treatment, and Prevention Strategies

Purpose of Review

Zoonotic influenza viruses are those influenza viruses that cross the animal-human barrier and can cause disease in humans, manifesting from minor respiratory illnesses to multiorgan dysfunction. The increasing incidence of infections caused by these viruses worldwide has necessitated focused attention to improve both diagnostic as well as treatment modalities. In this second part of a two-part review, we discuss the clinical features, diagnostic modalities, and treatment of zoonotic influenza, and provide an overview of prevention strategies.

Recent Findings

Illnesses caused by novel reassortant avian influenza viruses continue to be detected and described; most recently, a human case of avian influenza A(H7N4) has been described from China. We continue to witness increasing rates of A(H7N9) infections, with the latest (fifth) wave, from late 2016 to 2017, being the largest to date. The case fatality rate for A(H7N9) and A(H5N1) infections among humans is much higher than that of seasonal influenza infections. Since the emergence of the A(H1N1) 2009 pandemic, and subsequently A(H7N9), testing and surveillance for novel influenzas have become more effective. Various newer treatment options, including peramivir, favipiravir (T-705), and DAS181, and human or murine monoclonal antibodies have been evaluated in vitro and in animal models.

Summary

Armed with robust diagnostic modalities, antiviral medications, vaccines, and advanced surveillance systems, we are today better prepared to face a new influenza pandemic and to limit the burden of zoonotic influenza than ever before. Sustained efforts and robust research are necessary to efficiently deal with the highly mutagenic zoonotic influenza viruses.

Combined efficacy of oseltamivir, isoprinosine and ellagic acid in influenza A(H3N2)-infected mice

Influenza pathogenesis comprises a complex cascade of impaired cellular processes resulting from the viral replication and exaggerated immune response accompanied by reactive oxygen species (ROS) burst and oxidative stress, destructing membranous structures and tissues. By classical virological and biochemical methods we compared and evaluated the therapeutic effects of 2.5mg/kg/day of the antiviral drug - oseltamivir (OS), 500mg/kg/day of the immune modulator - isoprinosine (IP) and 500mg/kg/day of the antioxidant agent ellagic acid (EA) with a focus on their combined activities in influenza H3N2 virus-infected mice. The survival, lung pathology and titers, as well as the oxidative stress biomarker thiobarbituric acid reactive substances (TBARS) in the lungs, liver and blood plasma, correlated to the activities of the antioxidant enzymes superoxide dismutase (SOD) and glutathione reductase (GR) were assessed. We found that the viral inhibitor applied together with the immune modulator and the antioxidant exhibited strong therapeutic effects on the survival of the influenza-challenged mice. That effect was mostly pronounced for the triple combination - protection index (PI) of 75.2%, mean survival time (MST) extended by 5.8 days compared to the PBS control and significant reduction of the lung titers by 1.38 Δlg; 2.3 scores lower lung pathology and 8 times reduction of the accumulated TBARS in the lungs and liver on the 5^-th day p.i. The enzymatic assays revealed that this combination demonstrated very good protection against the damaging superoxide radicals (83% efficiency of SOD, in comparison to healthy controls 100%). The double combinations of OS with IP and EA also showed protective effects according to the virological analysis - PI of 53.1% and 54.5%. Ten times higher GR activity was observed when the combination EA+OS and monotherapy of EA were applied (96% in comparison to healthy controls 100%). The best antioxidant effect in blood plasma was observed in the EA+IP group - 4 times reduction in the TBARS-content compared to infected controls but it did not have any efficacy on the survival and lung injury.

Oseltamivir, amantadine, and ribavirin combination antiviral therapy versus oseltamivir monotherapy for the treatment of influenza: a multicentre, double-blind, randomised phase 2 trial

BACKGROUND

Influenza continues to have a substantial socioeconomic and health impact despite a long established vaccination programme and approved antivirals. Preclinical data suggest that combining antivirals might be more effective than administering oseltamivir alone in the treatment of influenza.

METHODS

We did a randomised, double-blind, multicentre phase 2 trial of a combination of oseltamivir, amantadine, and ribavirin versus oseltamivir monotherapy with matching placebo for the treatment of influenza in 50 sites, consisting of academic medical centre clinics, emergency rooms, and private physician offices in the USA, Thailand, Mexico, Argentina, and Australia. Participants who were aged at least 18 years with influenza and were at increased risk of complications were randomly assigned (1:1) by an online computer-generated randomisation system to receive either oseltamivir (75 mg), amantadine (100 mg), and ribavirin (600 mg) combination therapy or oseltamivir monotherapy twice daily for 5 days, given orally, and participants were followed up for 28 days. Blinded treatment kits were used to achieve masking of patients and staff. The primary endpoint was the percentage of participants with virus detectable by PCR in nasopharyngeal swab at day 3, and was assessed in participants who were randomised, had influenza infection confirmed by the central laboratory on a baseline nasopharyngeal sample, and had received at least one dose of study drug. Safety assessment was done in all patients in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT01227967.

FINDINGS

Between March 1, 2011, and April 29, 2016, 633 participants were randomly assigned to receive combination antiviral therapy (n=316) or monotherapy (n=317). Seven participants were excluded from analysis: three were not properly randomised, three withdrew from the study, and one was lost to follow-up. The primary analysis included 394 participants, excluding 47 in the pilot phase, 172 without confirmed influenza, and 13 without an endpoint sample. 80 (40·0%) of 200 participants in the combination group had detectable virus at day 3 compared with 97 (50·0%) of 194 (mean difference 10·0, 95% CI 0·2-19·8, p=0·046) in the monotherapy group. The most common adverse events were gastrointestinal-related disorders, primarily nausea (65 [12%] of 556 reported adverse events in the combination group vs 63 [11%] of 585 reported adverse events in the monotherapy group), diarrhoea (56 [10%] of 556 vs 64 [11%] of 585), and vomiting (39 [7%] of 556 vs 23 [4%] of 585). There was no benefit in multiple clinical secondary endpoints, such as median duration of symptoms (4·5 days in the combination group vs 4·0 days in the monotherapy group; p=0·21). One death occurred in the study in an elderly participant in the monotherapy group who died of cardiovascular failure 13 days after randomisation, judged by the site investigator as not related to study intervention.

INTERPRETATION

Although combination treatment showed a significant decrease in viral shedding at day 3 relative to monotherapy, this difference was not associated with improved clinical benefit. More work is needed to understand why there was no clinical benefit when a difference in virological outcome was identified.

FUNDING

National Institute of Allergy and Infectious Diseases, National Institutes of Health, USA.

Different Inhibitory Potencies of Oseltamivir Carboxylate, Zanamivir, and Several Tannins on Bacterial and Viral Neuraminidases as Assessed in a Cell-Free Fluorescence-Based Enzyme Inhibition Assay

Neuraminidase is a key enzyme in the life cycle of influenza viruses and is present in some bacterial pathogens. We here assess the inhibitory potency of plant tannins versus clinically used inhibitors on both a viral and a bacterial model neuraminidase by applying the 2′-(4-methylumbelliferyl)-α-d-N-acetylneuraminic acid (MUNANA)-based activity assay. A range of flavan-3-ols, ellagitannins and chemically defined proanthocyanidin fractions was evaluated in comparison to oseltamivir carboxylate and zanamivir for their inhibitory activities against viral influenza A (H1N1) and bacterial Vibrio cholerae neuraminidase (VCNA). Compared to the positive controls, all tested polyphenols displayed a weak inhibition of the viral enzyme but similar or even higher potency on the bacterial neuraminidase. Structure–activity relationship analyses revealed the presence of galloyl groups and the hydroxylation pattern of the flavan skeleton to be crucial for inhibitory activity. The combination of zanamivir and EPs^® 7630 (root extract of Pelargonium sidoides) showed synergistic inhibitory effects on the bacterial neuraminidase. Co-crystal structures of VCNA with oseltamivir carboxylate and zanamivir provided insight into bacterial versus viral enzyme-inhibitor interactions. The current data clearly indicate that inhibitor potency strongly depends on the biological origin of the enzyme and that results are not readily transferable. The therapeutic relevance of our findings is briefly discussed.

Comparison of three dimensional synergistic analyses of percentage versus logarithmic data in antiviral studies

Cell culture antiviral experiments were conducted in order to understand the relationship between percentage data generated by plaque reduction (PR) and logarithmic data derived by virus yield reduction (VYR) assays, using three-dimensional MacSynergy II software. The relationship between percentage and logarithmic data has not been investigated previously. Interpretation of drug-drug interactions is based on a Volume of Synergy (VS) calculation, which can be positive (synergy), negative (antagonistic), or neutral (no or minimal interaction). Interactions of two known inhibitors of vaccinia virus replication, cidofovir and 6-azauridine, used in combination by PR assay yielded a VS value of 265, indicative of strong synergy. By VYR, the VS value was only 37, or weak synergy using the same criterion, even though profound log₁₀ reductions in virus titer occurred at multiple drug combinations. These results confirm that the differences in VS values is dependent of the measurement scale, and not that the degree of synergy differed between the assays. We propose that for logarithmic data, the calculated VS values will be lower for significant synergy and antagonism and that volumes of >10 μM²log₁₀ PFU/ml (or other units such as μM²log₁₀ genomic equivalents/ml or μM²log₁₀ copies/ml) and <-10 μM²log₁₀ PFU/ml are likely to be indicative of strong synergy and strong antagonism, respectively. Data presented here show that the interaction of cidofovir and 6-azauridine was strongly synergistic in vitro.

Mapping the Resistance Potential of Influenza's H+ Channel against an Antiviral Blocker

The development of drug resistance has long plagued our efforts to curtail viral infections in general and influenza in particular. The problem is particularly challenging since the exact mode of resistance may be difficult to predict, without waiting for untreatable strains to evolve. Herein, a different approach is taken. Using a novel genetic screen, we map the resistance options of influenza's M2 channel against its aminoadamantane antiviral inhibitors. In the process, we could identify clinically known resistant mutations in a completely unbiased manner. Additionally, novel mutations were obtained, which, while known to exist in circulating viruses, were not previously classified as drug resistant. Finally, we demonstrated the approach against an anti-influenza drug that has not seen clinical use, identifying several resistance mutations in the process. In conclusion, we present and employ a method to predict the resistance options of influenza's M2 channel to antiviral agents ahead of clinical use and without medical hazard.

Comparative study on the antioxidant capacities of synthetic influenza inhibitors and ellagic acid in model systems

This study compares the antioxidant capacities in vitro of several synthetic and natural compounds applied and researched for influenza treatment - oseltamivir, isoprinosine, ellagic acid, vitamin E and vitamin C. Three chemical systems are utilized for the generation of reactive oxygen species (ROS) at pH 7.4 and pH 8.5: (1) Fenton's (Fe²⁺+H₂O₂) for OH and -OH species (2) H₂O₂ (3) NADH-phenazinemethosulfat, for superoxide radicals (O₂^-). The kinetics was evaluated by lucigenin-enhanced chemiluminescence. The calculated constants of inhibition k₇ describe the antioxidant capacity at the moment of oxidative burst. Their values do not necessarily correspond to the calculated total antioxidant activity. The obtained results revealed that the synthetic anti-influenza drugs (oseltamivir and isoprinosine) as well as ellagic acid possess pronounced scavenging properties mostly against superoxide radicals, comparable and higher than that of traditional natural antioxidants. Quantitative analysis of the antioxidant effects of the examined synthetic substances was performed. The results compared the corresponding effect of the average physiological concentrations and the applied therapeutic antioxidant dose. With these experiments we registered new aspects of their therapeutic activities, due to antioxidant properties against hydroxyl, superoxide radicals and H₂O₂ oxidation.

Pharmacological Characterization of the Spectrum of Antiviral Activity and Genetic Barrier to Drug Resistance of M2-S31N Channel Blockers

Adamantanes (amantadine and rimantadine) are one of the two classes of Food and Drug Administration-approved antiviral drugs used for the prevention and treatment of influenza A virus infections. They inhibit viral replication by blocking the wild-type (WT) M2 proton channel, thus preventing viral uncoating. However, their use was discontinued due to widespread drug resistance. Among a handful of drug-resistant mutants, M2-S31N is the predominant mutation and persists in more than 95% of currently circulating influenza A strains. We recently designed two classes of M2-S31N inhibitors, S31N-specific inhibitors and S31N/WT dual inhibitors, which are represented by N-[(5-cyclopropyl-1,2-oxazol-3-yl)methyl]adamantan-1-amine (WJ379) and N-[(5-bromothiophen-2-yl)methyl]adamantan-1-amine (BC035), respectively. However, their antiviral activities against currently circulating influenza A viruses and their genetic barrier to drug resistance are unknown. In this report, we evaluated the therapeutic potential of these two classes of M2-S31N inhibitors (WJ379 and BC035) by profiling their antiviral efficacy against multidrug-resistant influenza A viruses, in vitro drug resistance barrier, and synergistic effect with oseltamivir. We found that M2-S31N inhibitors were active against several influenza A viruses that are resistant to one or both classes of Food and Drug Administration-approved anti-influenza drugs. In addition, M2-S31N inhibitors display a higher in vitro genetic barrier to drug resistance than amantadine. The antiviral effect of WJ379 was also synergistic with oseltamivir carboxylate. Overall, these results reaffirm that M2-S31N inhibitors are promising antiviral drug candidates that warrant further development.

Combinations of Oseltamivir and T-705 Extend the Treatment Window for Highly Pathogenic Influenza A(H5N1) Virus Infection in Mice

Current anti-influenza therapy depends on administering drugs soon after infection, which is often impractical. We assessed whether combinations of oseltamivir (a neuraminidase inhibitor) and T-705 (a nonspecific inhibitor of viral polymerases) could extend the window for treating lethal infection with highly pathogenic A(H5N1) influenza virus in mice. Combination therapy protected 100% of mice, even when delayed until 96 h postinoculation. Compared to animals receiving monotherapy, mice receiving combination therapy had reduced viral loads and restricted viral spread in lung tissues, limited lung damage, and decreased inflammatory cytokine production. Next-generation sequencing showed that virus populations in T-705–treated mice had greater genetic variability, with more frequent transversion events, than did populations in control and oseltamivir-treated mice, but no substitutions associated with resistance to oseltamivir or T-705 were detected. Thus, combination therapy extended the treatment window for A(H5N1) influenza infection in mice and should be considered for evaluation in a clinical setting.

Avian influenza virus in pregnancy

The unprecedented epizootic of avian influenza viruses, such as H5N1, H5N6, H7N1 and H10N8, has continued to cause disease in humans in recent years. In 2013, another novel influenza A (H7N9) virus emerged in China, and 30% of those patients died. Pregnant women are particularly susceptible to avian influenza and are more likely to develop severe complications and to die, especially when infection occurs in the middle and late trimesters. Viremia is believed to occur infrequently, and thus vertical transmission induced by avian influenza appears to be rare. However, avian influenza increases the risk of adverse pregnancy outcomes, including spontaneous abortion, preterm birth and fatal distress. This review summarises 39 cases of pregnant women and their fetuses from different countries dating back to 1997, including 11, 15 and 13 infections with H7N9, H5N1 and the 2009 pandemic influenza (H1N1), respectively. We analysed the epidemic features, following the geographical, population and pregnancy trimester distributions; underlying diseases; exposure history; medical timelines; human-to-human transmission; pathogenicity and vertical transmission; antivirus treatments; maternal severity and mortality and pregnancy outcome. The common experiences reported in different countries and areas suggest that early identification and treatment are imperative. In the future, vigilant virologic and epidemiologic surveillance systems should be developed to monitor avian influenza viruses during pregnancy. Furthermore, extensive study on the immune mechanisms should be conducted, as this will guide safe, rational immunomodulatory treatment among this high-risk population. Most importantly, we should develop a universal avian influenza virus vaccine to prevent outbreaks of the different subtypes. Copyright © 2016 John Wiley & Sons, Ltd.

Efficacy of oseltamivir-peramivir combination therapy compared to oseltamivir monotherapy for Influenza A (H7N9) infection: a retrospective study

BACKGROUND

Since the novel H7N9 avian influenza outbreak occurred in China in 2013, neuraminidase inhibitors (NAIs) such as oseltamivir and peramivir have been used as first-line drugs to treat the influenza virus infection. This study aimed to compare the efficacy of oseltamivir-peramivir combination therapy versus oseltamivir monotherapy.

METHODS

A retrospective study of 82 H7N9 confirmed patients was conducted by reviewing medical charts at the First Affiliated Hospital of ZheJiang University in China from April 1, 2013 to Feb 28, 2014. The patients' clinical information was collected systematically, and we compared the virology and clinical data between oseltamivir monotherapy group (43 patients) and oseltamivir-peramivir combination group (39 patients).

RESULTS

The median duration from NAIs administration to H7N9 virus-negative in oseltamivir monotherapy group and oseltamivir-peramivir combination group was 6.50 and 7.00 days (p >0.05), respectively. The median decline of Day 2 to Day 0 (initiation of NAIs therapy) viral load was 0.00 and 0.69 log10 copies/μl (p >0.05) respectively in the monotherapy vs. combination therapy groups. The incidence of new Acute Respiratory Distress Syndrome during NAI administration was 63.89 and 77.78 % (p >0.05); while the mortality rates were 25.58 and 43.59 % (p >0.05) in the oseltamivir group vs. oseltamivir-peramivir group.

CONCLUSIONS

Our results suggest that in adults with H7N9 virus infection, the use of oseltamivir-peramivir combination therapy was not superior to oseltamivir monotherapy.

New small-molecule drug design strategies for fighting resistant influenza A

Influenza A virus is the major cause of seasonal or pandemic flu worldwide. Two main treatment strategies-vaccination and small molecule anti-influenza drugs are currently available. As an effective vaccine usually takes at least 6 months to develop, anti-influenza small molecule drugs are more effective for the first line of protection against the virus during an epidemic outbreak, especially in the early stage. Two major classes of anti-influenza drugs currently available are admantane-based M2 protein blockers (amantadine and rimantadine) and neuraminidase (NA) inhibitors (oseltamivir, zanamivir, and peramivir). However, the continuous evolvement of influenza A virus and the rapid emergence of resistance to current drugs, particularly to amantadine, rimantadine, and oseltamivir, have raised an urgent need for developing new anti-influenza drugs against resistant forms of influenza A virus. In this review, we first give a brief introduction of the molecular mechanisms behind resistance, and then discuss new strategies in small-molecule drug development to overcome influenza A virus resistance targeting mutant M2 proteins and neuraminidases, and other viral proteins not associated with current drugs.

Adamantane-resistant influenza a viruses in the world (1902-2013): frequency and distribution of M2 gene mutations

Adamantanes (amantadine and rimantadine) have been used to prevent and treat influenza A virus infections for many years; however, resistance to these drugs has been widely reported in the world. To investigate the frequency and distribution of M2 gene mutations in adamantane-resistant influenza variants circulated in the world between 1902 and 2013, 31251 available M2 protein sequences from different HA-subtype influenza A viruses (H1–H17) were analyzed and adamantane resistance-associated mutations were compared (L26F, V27A, A30T, A30V, S31N, G34E, and L38F). We find that 45.2% (n = 14132) of influenza A (H1–H17) viruses circulating globally were resistant to adamantanes, and the vast majority of resistant viruses (95%) bear S31N mutations. Whereas, only about 1% have V27A mutations and other mutations (L26F, A30T, G34E, and L38F) were extremely rare (their prevalence appeared to be < 0.2%). Our results confirm that H1, H3, H5, H7, H9, and H17 subtype influenza A viruses exhibit high-level resistance to adamantanes. In contrast, the appearance of adamantane-resistant mutants in H2, H4, H6, H10, and H11 subtypes was rare. However, no adamantane resistance viruses were identified among other HA subtypes (H8, H12–H16). Our findings indicate that the frequency and distribution of adamantane-resistant influenza variants varied among different HA subtypes, host species, years of isolation, and geographical areas. This comprehensive study raises concerns about the increasing prevalence of adamantane-resistant influenza A viruses and highlights the importance of monitoring the emergence and worldwide spread of adamantane-resistant variants.

How to approach and treat viral infections in ICU patients

Patients with severe viral infections are often hospitalized in intensive care units (ICUs) and recent studies underline the frequency of viral detection in ICU patients. Viral infections in the ICU often involve the respiratory or the central nervous system and can cause significant morbidity and mortality especially in immunocompromised patients. The mainstay of therapy of viral infections is supportive care and antiviral therapy when available. Increased understanding of the molecular mechanisms of viral infection has provided great potential for the discovery of new antiviral agents that target viral proteins or host proteins that regulate immunity and are involved in the viral life cycle. These novel treatments need to be further validated in animal and human randomized controlled studies.

Amantadine and rimantadine for influenza A in children and the elderly

BACKGROUND

Influenza is an acute respiratory illness caused by influenza A and B viruses. Complications may occur, especially among children and the elderly.

OBJECTIVES

To assess the effectiveness and safety of amantadine and rimantadine in preventing, treating and shortening the duration of influenza A in children and the elderly.

SEARCH METHODS

We searched CENTRAL (2014, Issue 9), MEDLINE (1966 to September week 4, 2014) and EMBASE (1980 to October 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing amantadine and/or rimantadine with no intervention, placebo, other antivirals or different doses or schedules of amantadine or rimantadine in children and the elderly with influenza A.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the search results. We extracted and analysed data using the standard Cochrane methodology.

MAIN RESULTS

We identified 12 studies (2494 participants: 1586 children and 908 elderly) comparing amantadine and rimantadine with placebo, paracetamol (one trial: 69 children) or zanamivir (two trials: 545 elderly) to treat influenza A.Amantadine was effective in preventing influenza A in children (773 participants, risk ratio (RR) 0.11; 95% confidence interval (CI) 0.04 to 0.30). The assumed risk of influenza A in the control group was 10 per 100. The corresponding risk in the rimantadine group was one per 100 (95% CI 0 to 3). Nevertheless, the quality of the evidence was low and the safety of the drug was not well established.For treatment, rimantadine was beneficial in abating fever on day three of treatment in children: one selected study with low risk of bias, moderate evidence quality and 69 participants (RR 0.36; 95% CI 0.14 to 0.91). The assumed risk was 38 per 100. The corresponding risk in the rimantadine group was 14 per 100 (95% CI 5 to 34).Rimantadine did not show any prophylactic effect in the elderly. The quality of evidence was very low: 103 participants (RR 0.45; 95% CI 0.14 to 1.41). The assumed risk was 17 per 100. The corresponding risk in the rimantadine group was 7 per 100 (95% CI 2 to 23).There was no evidence of adverse effects caused by treatment with amantadine or rimantadine.We found no studies assessing amantadine in the elderly.

AUTHORS' CONCLUSIONS

The quality of the evidence combined with a lack of knowledge about the safety of amantadine and the limited benefits of rimantadine, do not indicate that amantadine and rimantadine compared to control (placebo or paracetamol) could be useful in preventing, treating and shortening the duration of influenza A in children and the elderly.

A Critical Role for Immune System Response in Mediating Anti-influenza Drug Synergies Assessed by Mechanistic Modeling

Influenza virus infections represent a serious public health problem worldwide, due to the rapid emergence of drug resistance. One strategy to improve treatment efficacy is to combine drugs that act synergistically. Potentially useful drug combinations are typically identified through empirical testing using in vitro and animal models, but the complexity of the clinical situation warrants the use of more careful analysis and sophisticated approaches. To explore new approaches, we constructed a mechanistic model representing the interaction of antiviral drugs with the viral replication pathway and human immune responses. Simulation of combination therapy using oseltamivir and amantadine predicted significant therapeutic synergy only when immune response was included, in agreement with previous in vitro and in vivo studies using amantadine-resistant strains. Our model can be used to predict the optimal doses for combination therapy, and also raises questions about current drug evaluation methods that do not account for immune system interactions.

Antiviral combinations for severe influenza

Observational data suggest that the treatment of influenza infection with neuraminidase inhibitors decreases progression to more severe illness, especially when treatment is started soon after symptom onset. However, even early treatment might fail to prevent complications in some patients, particularly those infected with novel viruses such as the 2009 pandemic influenza A H1N1, avian influenza A H5N1 virus subtype, or the avian influenza A H7N9 virus subtype. Furthermore, treatment with one antiviral drug might promote the development of antiviral resistance, especially in immunocompromised hosts and critically ill patients. An obvious strategy to optimise antiviral therapy is to combine drugs with different modes of action. Because host immune responses to infection might also contribute to illness pathogenesis, improved outcomes might be gained from the combination of antiviral therapy with drugs that modulate the immune response in an infected individual. We review available data from preclinical and clinical studies of combination antiviral therapy and of combined antiviral-immunomodulator therapy for influenza. Early-stage data draw attention to several promising antiviral combinations with therapeutic potential in severe infections, but there remains a need to substantiate clinical benefit. Combination therapies with favourable experimental data need to be tested in carefully designed aclinical trials to assess their efficacy.

Combination therapy with amantadine, oseltamivir and ribavirin for influenza A infection: safety and pharmacokinetics

BACKGROUND

Antiviral resistance among influenza A viruses is associated with high morbidity and mortality in immunocompromised hosts. However, treatment strategies for drug-resistant influenza A are not established. A triple-combination antiviral drug (TCAD) regimen consisting of amantadine (AMT), oseltamivir (OSL) and ribavirin (RBV) demonstrated good efficacy in an animal model.

METHODS

We first analysed the pharmacokinetics (PKs) of TCAD therapy in healthy volunteers. We then performed a pilot study of TCAD therapy in patients undergoing chemotherapy or haematopoietic cell transplantation. AMT (75 mg), OSL (50 mg) and RBV (200 mg) were administered three times a day for 10 days. The safety and PKs of TCAD therapy were monitored.

RESULTS

The PKs of TCAD therapy in healthy volunteers was shown to be similar to the PKs of each drug individually from a single dose. In the pilot study, six immunocompromised patients received TCAD therapy and one patient received OSL monotherapy. All but one patient completed 10 days of TCAD therapy without side effects; one patient receiving TCAD was withdrawn from the study because of respiratory failure and ultimately recovered. Viral load was decreased after TCAD therapy, despite the presence of either AMT- or OSL-resistant virus in two cases. One patient with 2009 influenza A/H1N1 receiving OSL monotherapy developed confirmed OSL resistance during treatment.

CONCLUSIONS

TCAD therapy had similar PKs to each individual antiviral during monotherapy following a single dose and can be administered safely in immunocompromised patients.

Characterization of a fully human monoclonal antibody against extracellular domain of matrix protein 2 of influenza A virus

The extra-cellular domain of the influenza virus matrix protein 2 (M2e) is highly conserved between influenza A virus strains compared to hemagglutinin and neuraminidase, and has long been viewed as a potential and universal vaccine target. M2e induces no or only weak and transient immune responses following infection, making it difficult to detect M2e-specific antibodies producing B-cells in human peripheral blood lymphocytes. Recently, using a single-cell manipulation method, immunospot array assay on a chip (ISAAC), we obtained an M2e-specific human antibody (Ab1-10) from the peripheral blood of a healthy volunteer. In this report, we have demonstrate that Ab1-10 reacted not only to seasonal influenza A viruses, but also to pandemic (H1N1) 2009 virus (2009 H1N1) and highly pathogenic avian influenza A virus, and that the antibody-bound M2e of 2009 H1N1 inactivated the virus with high affinity (∼10(-10)M). More importantly, it inhibited 2009 H1N1 viral propagation in vitro. These results suggest that Ab1-10 might be a potential candidate for antibody therapeutics for a wide range of influenza A viruses.