Arbidol: a broad-spectrum antiviral compound that blocks viral fusion

Arbidol (ARB; ethyl-6-bromo-4-[(dimethylamino)methyl]-5-hydroxy-1-methyl-2-[(phenylthio)methyl]-indole-3-carboxylate hydrochloride monohydrate), is a Russian-made potent broad-spectrum antiviral with demonstrated activity against a number of enveloped and non-enveloped viruses. ARB is well known in Russia and China, although to a lesser extent in western countries. Unlike other broad-spectrum antivirals, ARB has an established molecular mechanism of action against influenza A and B viruses, which is different from that of available influenza antivirals, and a more recently established mechanism of inhibition of hepatitis C virus (HCV). For both viral infections the anti-viral mechanism involves ARB inhibition of virus-mediated fusion with target membrane and a resulting block of virus entry into target cells. However, ARB inhibition of fusion exploits different ARB modalities in case of influenza viruses or HCV. This review aims to summarize the available evidence of ARB effects against different groups of viruses, also, to compare various aspects of ARB anti-fusion mechanisms against influenza virus and HCV (with reference to different stringency of pH-dependence of these two viral fusogens) and to discuss further prospects for ARB and its improved derivatives of the parent compounds.

Characteristics of arbidol-resistant mutants of influenza virus: implications for the mechanism of anti-influenza action of arbidol

The antiviral drug arbidol (ARB), which is licensed in Russia for use against influenza, is known to inhibit early membrane fusion events in influenza A and B virus replication. To investigate in more detail the target and mechanism of ARB action we generated and studied the characteristics of ARB-resistant influenza virus mutants. Observations of the ARB susceptibility of reassortants between A/Singapore/1/57(H2N2) and A/chicken/Germany/27(H7N7, "Weybridge" strain) and of mutants of the latter virus identified the virus haemagglutinin (HA) as the major determinant of ARB sensitivity. ARB-resistant mutants, selected from the most sensitive reassortant, possessed single amino acid substitutions in the HA2 subunit which caused an increase in the pH of fusion and the associated conformational change in HA. ARB was shown to stabilize the HA by causing a 0.2 pH unit reduction in the pH of the transition to the low pH form, which was specifically abrogated by the resistance mutations. Some of the resistance mutations, which reduce acid stability and would disrupt ARB-HA interactions, are located in the vicinity of a potential ARB binding site identified using the docking programme Gold. Together, the results of these investigations indicate that ARB falls within a class of inhibitor which interacts with HA to stabilize it against the low pH transition to its fusogenic state and consequently inhibit HA-mediated membrane fusion during influenza virus infection.

Comparison of efficacies of RWJ-270201, zanamivir, and oseltamivir against H5N1, H9N2, and other avian influenza viruses

The orally administered neuraminidase (NA) inhibitor RWJ-270201 was tested in parallel with zanamivir and oseltamivir against a panel of avian influenza viruses for inhibition of NA activity and replication in tissue culture. The agents were then tested for protection of mice against lethal H5N1 and H9N2 virus infection. In vitro, RWJ-270201 was highly effective against all nine NA subtypes. NA inhibition by RWJ-270201 (50% inhibitory concentration, 0.9 to 4.3 nM) was superior to that by zanamivir and oseltamivir carboxylate. RWJ-270201 inhibited the replication of avian influenza viruses of both Eurasian and American lineages in MDCK cells (50% effective concentration, 0.5 to 11.8 microM). Mice given 10 mg of RWJ-270201 per kg of body weight per day were completely protected against lethal challenge with influenza A/Hong Kong/156/97 (H5N1) and A/quail/Hong Kong/G1/97 (H9N2) viruses. Both RWJ-270201 and oseltamivir significantly reduced virus titers in mouse lungs at daily dosages of 1.0 and 10 mg/kg and prevented the spread of virus to the brain. When treatment began 48 h after exposure to H5N1 virus, 10 mg of RWJ-270201/kg/day protected 50% of mice from death. These results suggest that RWJ-270201 is at least as effective as either zanamivir or oseltamivir against avian influenza viruses and may be of potential clinical use for treatment of emerging influenza viruses that may be transmitted from birds to humans.

The neuraminidase inhibitor GS4104 (oseltamivir phosphate) is efficacious against A/Hong Kong/156/97 (H5N1) and A/Hong Kong/1074/99 (H9N2) influenza viruses

In 1997, an H5N1 avian influenza A/Hong Kong/156/97 virus transmitted directly to humans and killed six of the 18 people infected. In 1999, another avian A/Hong/1074/99 (H9N2) virus caused influenza in two children. In such cases in which vaccines are unavailable, antiviral drugs are crucial for prophylaxis and therapy. Here we demonstrate the efficacy of the neuraminidase inhibitor GS4104 (oseltamivir phosphate) against these H5N1 and H9N2 viruses. GS4071 (the active metabolite of oseltamivir) inhibited viral replication in MDCK cells (EC(50) values, 7.5-12 microM) and neuraminidase activity (IC(50) values, 7.0-15 nM). When orally administered at doses of 1 and 10 mg/kg per day, GS4104 prevented death of mice infected with A/Hong Kong/156/97 (H5N1), mouse-adapted A/Quail/Hong Kong/G1/97 (H9N2), or human A/Hong Kong/1074/99 (H9N2) viruses and reduced virus titers in the lungs and prevented the spread of virus to the brain of mice infected with A/Hong Kong/156/97 (H5N1) and mouse-adapted A/Quail/Hong Kong/G1/97 (H9N2) viruses. When therapy was delayed until 36 h after exposure to the H5N1 virus, GS4104 was still effective and significantly increased the number of survivors as compared with control. Oral administration of GS4104 (0.1 mg/kg per day) in combination with rimantadine (1 mg/kg per day) reduced the number of deaths of mice infected with 100 MLD(50) of H9N2 virus and prevented the deaths of mice infected with 5 MLD(50) of virus. Thus, GS4104 is efficacious in treating infections caused by H5N1 and H9N2 influenza viruses in mice.

The Comparative Analysis of Antiviral Activity of Native and Modified Fucoidans from Brown Algae Fucus evanescens In Vitro and In Vivo

The enzymatic depolymerization of fucoidans from brown algae allowed the production of their standardized derivatives with different biological activities. This work aimed to compare the antiviral activities of native (FeF) and modified with enzyme (FeHMP) fucoidans from F. evanescens. The cytotoxicity and antiviral activities of the FeF and FeHMP against herpes viruses (HSV-1, HSV-2), enterovirus (ECHO-1), and human immunodeficiency virus (HIV-1) in Vero and human MT-4 cell lines were examined by methylthiazolyltetrazolium bromide (MTT) and cytopathic effect (CPE) reduction assays, respectively. The efficacy of fucoidans in vivo was evaluated in the outbred mice model of vaginitis caused by HSV-2. We have shown that both FeF and FeHMP significantly inhibited virus-induced CPE in vitro and were more effective against HSV. FeF exhibited antiviral activity against HSV-2 with a selective index (SI) > 40, and FeHMP with SI ˃ 20, when they were added before virus infection or at the early stages of the HSV-2 lifecycle. Furthermore, in vivo studies showed that after intraperitoneal administration (10 mg/kg), both FeF and FeHMP protected mice from lethal intravaginal HSV-2 infection to approximately the same degree (44-56%). Thus, FeF and FeHMP have comparable potency against several DNA and RNA viruses, allowing us to consider the studied fucoidans as promising broad-spectrum antivirals.

Efficacy of zanamivir against avian influenza A viruses that possess genes encoding H5N1 internal proteins and are pathogenic in mammals

In 1997, an avian H5N1 influenza virus, A/Hong Kong/156/97 (A/HK/156/97), caused six deaths in Hong Kong, and in 1999, an avian H9N2 influenza virus infected two children in Hong Kong. These viruses and a third avian virus [A/Teal/HK/W312/97 (H6N1)] have six highly related genes encoding internal proteins. Additionally, A/Chicken/HK/G9/97 (H9N2) virus has PB1 and PB2 genes that are highly related to those of A/HK/156/97 (H5N1), A/Teal/HK/W312/97 (H6N1), and A/Quail/HK/G1/97 (H9N2) viruses. Because of their similarities with the H5N1 virus, these H6N1 and H9N2 viruses may have the potential for interspecies transmission. We demonstrate that these H6N1 and H9N2 viruses are pathogenic in mice but that their pathogenicities are less than that of A/HK/156/97 (H5N1). Unadapted virus replicated in lungs, but only A/HK/156/97 (H5N1) was found in the brain. After three passages (P3) in mouse lungs, the pathogenicity of the viruses increased, with both A/Teal/HK/W312/97 (H6N1) (P3) and A/Quail/HK/G1/97 (H9N2) (P3) viruses being found in the brain. The neuraminidase inhibitor zanamivir inhibited viral replication in Madin-Darby canine kidney cells in virus yield assays (50% effective concentration, 8.5 to 14.0 microM) and inhibited viral neuraminidase activity (50% inhibitory concentration, 5 to 10 nM). Twice daily intranasal administration of zanamivir (50 and 100 mg/kg of body weight) completely protected infected mice from death. At a dose of 10 mg/kg, zanamivir completely protected mice from infection with H9N2 viruses and increased the mean survival day and the number of survivors infected with H6N1 and H5N1 viruses. Zanamivir, at all doses tested, significantly reduced the virus titers in the lungs and completely blocked the spread of virus to the brain. Thus, zanamivir is efficacious in treating avian influenza viruses that can be transmitted to mammals.

Antioxidant Potential of Antiviral Drug Umifenovir

Free radical reactions play an important role in biological functions of living systems. The balance between oxidants and antioxidants is necessary for the normal homeostasis of cells and organisms. Experimental works demonstrate the role of oxidative stress that is caused by influenza virus as well as the toxic effects of some antiviral drugs. Therefore, antiviral drugs should be characterized by its pro- and antioxidant activity, because it can affect its therapeutic efficiency. The aim of the study was to quantify the antioxidant capacity and propose the mechanism of the antioxidant effect of the antiviral drug Umifenovir (Arbidol®). The kinetic chemiluminescence with the 2,2'-azobis (2-amidinopropane) dihydrochloride + luminol system was used to quantify the antioxidant capacity of Umifenovir relative to the standard compound Trolox. With computer simulation, the reaction scheme and rate constants were proposed. The antioxidant capacity of 0.9 μM Umifenovir (maximum concentration of Umifenovir in blood after oral administration of 200 mg) was as high as 1.65 ± 0.18 μM of Trolox. Thus, the total antioxidant capacity of Umifenovir is comparable to the antioxidant capacity of Trolox. Unlike Trolox, Umifenovir reacts with free radicals in two stages. For Trolox, the free radical scavenging rate constant was k = 2000 nM-1 min.-1, for Umifenovir k1 = 300 nM-1min.-1, k2 = 4 nM-1min.-1. Slower kinetics of Umifenovir provides the prolonged antioxidant effect when compared to Trolox. This phenomenon can make a serious contribution to the compensation of oxidative stress that is caused by a viral disease and the therapeutic effect of the drug.

Clinical efficacy of umifenovir in influenza and ARVI (study ARBITR)

AIM

The aim of the study is to obtain additional data on safety and therapeutic efficacy of the antiviral drug Arbidol (umifenovir) in patients with a diagnosis of influenza and common cold.

MATERIALS AND METHODS

Double-blind, randomized, placebo-controlled clinical study investigating efficacy and safety of Arbidol (umifenovir) in Treatment and Prophylaxis of Influenza and Common Cold (ARBITR) IV phase started in November 2011 and completed in April 2016 on the basis of 15 research centers in various regions of the Russian Federation. A total of 359 patients, aged 18 to 65 years with influenza or acute respiratory tract infection, of no more than 36 hours' duration were enrolled in the study. Patients were randomized into two groups: a group of patients (therapy group) treated by Arbidol (umifenovir) at a dosage of 800 mg/day (2 capsules) for 5 days (n=181), and a group of patients receiving placebo 4 times a day for 5 days (n=178). The primary outcome measures of the study were the duration of clinical illness among patients with common cold and influenza/ARVI, the duration and severity of the main symptoms. Number of clinical complications associated with influenza and common cold was assessed as a secondary outcome. Safety was assessed by analyzing number of adverse events that are probably or definitely related to Arbidol, assessing vital signs, examining the physical condition of patients and general clinical laboratory parameters.

RESULTS

In the group treated by umifenovir, the number of full recover patients on the 4th day from the disease onset were significantly differed from the number of such cases in the placebo group. The number of cases of complete recovery after 96 hours was 98 patients (54.1%) and 77 (43.3%), p<0.05, and after 108 hours - 117 (64.6%) and 98 (55.1%), p<0.05. Duration of intoxication was reduced with umifenovir compared to placebo, amounted to 77.76 and 88.91 hours, respectively, p=0.013. The duration of all intoxication syndrome symptoms was also lower in the group receiving umifenovir. Thus, in the therapy group and placebo group, these parameters were respectively: fever duration - 67.96 and 75.32 hours (p=0.037), muscle pain - 52.23 and 59.08 hours (p=0.023), headache - 52.78 and 63.28 hours (p=0.013), weakness - 76.90 and 88.89 hours (p=0.008). The incidence of complications in the umifenovir group was 3.8%, in the placebo group 5.62%. Cases of acute tracheobronchitis was an increase in the placebo group (p<0.02). Umifenovir and placebo were well tolerated. A total of 42 cases of adverse events were registered in 11 patients in the treatment group and in 18 patients in the placebo group, which were not associated with umifenovir or placebo.

CONCLUSION

The results of this study indicate umifenovir safety and confirm its effectiveness to the treatment of influenza and other acute respiratory viral infections in adult patients. It was found that effect of umifenovir in the treatment of influenza in adults is most pronounced in the acute stage of the disease and appears in the reduction of time to resolution of all symptoms of the disease, reducing the severity of symptoms of the disease.

[Clinical efficacy of arbidol (umifenovir) in the therapy of influenza in adults: preliminary results of the multicenter double-blind randomized placebo-controlled study ARBITR]

AIM

To evaluate the efficacy and safety of Arbidol (umifenovir) in adult patients with influenza.

SUBJECTS AND METHODS

The analysis of the preliminary results of the multicenter double-blind randomized placebo-controlled post-marketing study ARBITR was performed. A total of 293 adults aged 18 to 65 years with influenza or acute respiratory tract infection of no more than 36 hours' duration were enrolled in the study. Individuals were randomized into 2 treatment groups: oral umifenovir 200 mg four times daily for 5 days or placebo four times daily for 5 days. The efficacy endpoints were time to resolution of all symptoms, severity of symptoms and illness, durations of virus shedding.

RESULTS

The efficacy of umifenovir was evaluated in the group of 119 (40.6%) patients with influenza: 45 patients with laboratory-confirmed influenza and 74 patients whom diagnosis of influenza was made based on clinical and epidemiological data. Umifenovir had influence on the time to resolution of all symptoms. All symptoms were resolved within the first 60 hours after therapy initiation in 23.8% patients with laboratory-confirmed influenza in the umifenovir group and it was 5.7 times greater compared to placebo group (4.2%) (p < 0.05). Severity of illness, catarrhal symptoms and intoxication was reduced with umifenovir compared to placebo, reducing of severity was most evidently observed within the first 2-3 days following the therapy initiation. Umifenovir had a significant effect on viral shedding. The proportion of patients still shedding influenza virus on day 4 was significantly reduced in the umifenovir group compared to placebo (25 vs 53%, respectively; p < 0.05).

CONCLUSION

It was found that the effect of umifenovir in the treatment of influenza in adults is most pronounced in the acute stage of the disease and appears in the reduction of time to resolution of all symptoms of the disease, reducing the severity of symptoms of the disease and durations of virus shedding.

A novel influenza virus neuraminidase inhibitor AV5027

A medium-sized focused library of novel Oseltamivir structural analogues with promising antiviral activity was successfully synthesized using a combinatorial approach. The synthesized compounds were then thoroughly evaluated in neuraminidase- and cell-based assays. As a result, (3R,4R,5S)-4-(2,2-difluoroacetylamino)-5-amino-3-(1-ethyl-propoxy)-cyclohex-1-enecarboxylic acid (AV5027) was identified as novel Hit-compound with picomolar potency. QSAR analysis was carried out based on the obtained biological data. Computational modeling was performed using a 3D-molecular docking approach and classical regression analysis. The developed integral model demonstrated a sufficient prediction accuracy and tolerance to evaluate compounds based on their potential activity against neuraminidase (NA) at least within the scaffold. Several compounds from the series can be reasonably regarded as promising anti-influenza drug-candidates.

Synthesis, inhibitory activity and oral dosing formulation of AV5124, the structural analogue of influenza virus endonuclease inhibitor baloxavir

BACKGROUND

The development and clinical implementation of the cap-dependent endonuclease (CEN) inhibitor baloxavir marboxil was a breakthrough in influenza therapy, but it was associated with the emergence of drug-resistant variants.

OBJECTIVES

To design and synthesize structural analogues of CEN inhibitors and evaluate their safety, pharmacokinetics and antiviral potency in vitro and in vivo.

METHODS

The drug candidate AV5124 and its active metabolite AV5116 were synthesized based on pharmacophore modelling. Stability in plasma and microsomes, plasma protein binding, cytotoxicity and antiviral activities were assessed in vitro. Pharmacokinetics after IV or oral administration were analysed in CD-1 mice. Acute toxicity and protective efficacy against lethal A(H1N1)pdm09 influenza virus challenge were examined in BALB/c mice.

RESULTS

Pharmacophore model-assisted, 3D molecular docking predicted key supramolecular interactions of the metal-binding group and bulky hydrophobic group of AV5116 with the CEN binding site (Protein Data Bank code: 6FS6) that are essential for high antiviral activity. AV5116 inhibited influenza virus polymerase complexes in cell-free assays and replication of oseltamivir-susceptible and -resistant influenza A and B viruses at nanomolar concentrations. Notably, AV5116 was equipotent or more potent than baloxavir acid (BXA) against WT (I38-WT) viruses and viruses with reduced BXA susceptibility carrying an I38T polymerase acidic (PA) substitution. AV5116 exhibited low cytotoxicity in Madin-Darby canine kidney cells and lacked mitochondrial toxicity, resulting in favourable selective indices. Treatment with 20 or 50 mg/kg AV5124 prevented death in 60% and 100% of animals, respectively.

CONCLUSIONS

Overall, AV5124 and A5116 are promising inhibitors of the influenza virus CEN and warrant further development as potent anti-influenza agents.

Non-rigid Diarylmethyl Analogs of Baloxavir as Cap-Dependent Endonuclease Inhibitors of Influenza Viruses

4-Substituted 2,4-dioxobutanoic acids inhibit influenza virus cap-dependent endonuclease (CEN) activity. Baloxavir marboxil, 4, is approved for treating influenza virus infections. We describe here the synthesis and biological evaluation of active compounds, 5a-5g, and their precursors (6a, 6b, 6d, and 6e) with flexible bulky hydrophobic groups instead of the rigid polyheterocyclic moieties. In silico docking confirmed the ability of 5a-5g to bind to the active site of influenza A CEN (PDB code: 6FS6) like baloxavir acid, 3. These novel compounds inhibited polymerase complex activity, inhibited virus replication in cells, prevented death in a lethal influenza A virus mouse challenge model, and dramatically lowered viral lung titers. 5a and 5e potently inhibited different influenza genera in vitro. Precursors 6a and 6d demonstrated impressive mouse oral bioavailability with 6a, providing effective in vivo protection. Thus, these novel compounds are potent CEN inhibitors with in vitro and in vivo activity comparable to baloxavir.

[Pharmacoepidemiological study of the course of influenza and other acute respiratory viral infections in risk groups]

AIM

To identify risk factors (RFs) for the development of bacterial complications and the prolonged course of influenza and other acute respiratory viral infections (ARVIs) among inpatients treated in Russian healthcare facilities in the post-pandemic period; to determine the clinical presentation of the disease (flu-like syndrome) in risk-group people and to evaluate the efficacy of antiviral therapy with arbidol (umifenovir).

MATERIAL AND METHODS

The investigators retrospectively analyzed randomly selected medical records of inpatients with influenza and other ARVI in 88 hospitals from 50 regions of the Russian Federation: those of 3532 and 1755 patients in the 2010-2011 and 2014-2015 seasons, respectively, by applying parametric and nonparametric statistical methods.

RESULTS

The built database of patients with influenza-like syndrome contained data from the histories of 2072 men and 2537 women, of whom there were 317 (12.49%) pregnant women; gender evidence was not given in the medical records for 678 patients. 382 (7.2%) were vaccinated against influenza. 1528 (28.9%) people were admitted to hospital with various complications. Information on laboratory tests was available in 1691 (31.98%) patients; of these, 1291 (76.4%) were detected to have influenza and other respiratory viruses. Influenza viruses were found in 1026 (60.7%) examinees; influenza A viruses in 712 (42.1%) people while pandemic strain of swine influenza A/H1N1 and A/H3N2 viruses was detected in 487 (28.8%) and 107 (6.3%) patients, respectively; influenza A subtype was indicated in 118 (7%) persons with laboratory-confirmed influenza virus. Influenza B viruses were found in 314 (18.6%) examinees. Other types of respiratory viruses were detected in 265 (15.7%) patients. The body mass index exceeded 30 kg/m2 in 227 (4.3%) patients. Single-factor analysis of variance revealed factors influencing the course of flu-like syndrome and identified risk groups: children younger than 2 years old and adults over 65, pregnant women, and people with chronic somatic diseases and obesity. The high-risk groups exhibited a more severe course of flu-like syndrome than did the patients outside the risk groups. The incidence of complications was higher, especially in the under 2-year-year-old children and in patients with endocrine, metabolic, or respiratory diseases, with a large proportion of complications being pneumonia. The efficacy of antiviral therapy was higher in the elderly, patients with chronic diseases, and pregnant women than in patients not at risk. In patients treated with umifenovir (provided that it was administered in the first 48 hours after disease onset), the duration of fever and frequency of complications proved to be lower than those in patients who did not receive antiviral therapy.

CONCLUSION

The FRs for influenza and ARVI complications are patient's age (children under 3 years of age and adults older than 65 years), the presence of chronic somatic diseases, and pregnancy. Patients with endocrine, eating, metabolic (including obesity), circulatory, and respiratory disorders are at high risk for influenza and ARVI complications. Umifenovir therapy substantially reduces the duration of fever and risk of complications, especially in patients with laboratory-confirmed influenza infection.

Off-target effects of an insect cell-expressed influenza HA-pseudotyped Gag-VLP preparation in limiting postinfluenza Staphylococcus aureus infections

Clinical and historical data underscore the ability of influenza viruses to ally with Staphylococcus aureus and predispose the host for secondary bacterial pneumonia, which is a leading cause of influenza-associated mortality. This is fundamental because no vaccine for S. aureus is available and the number of antibiotic-resistant strains is alarmingly rising. Hence, this leaves influenza vaccination the only strategy to prevent postinfluenza staphylococcal infections. In the present work, we assessed the off-target effects of a Tnms42 insect cell-expressed BEI-treated Gag-VLP preparation expressing the HA of A/Puerto Rico/8/1934 (H1N1) in preventing S. aureus superinfection in mice pre-infected with a homologous or heterologous H1N1 viral challenge strain. Our results demonstrate that matched anti-hemagglutinin immunity elicited by a VLP preparation may suffice to prevent morbidity and mortality caused by lethal secondary bacterial infection. This effect was observed even when employing a single low antigen dose of 50 ng HA per animal. However, induction of anti-hemagglutinin immunity alone was not helpful in inhibiting heterologous viral replication and subsequent bacterial infection. Our results indicate the potential of the VLP vaccine approach in terms of immunogenicity but suggest that anti-HA immunity should not be considered as the sole preventive method for combatting influenza and postinfluenza bacterial infections.

Interaction of M protein and RNP of fowl plague virus in vitro

The ability of the fowl plague virus (FPV) M protein to form a complex with FPV RNP and to inhibit the RNP transcriptase activity in vitro depended on NaCl concentration and did not depend on the concentration of nonionic detergents. The results obtained indicate that the M protein-RNP links formed were of an electrostatic rather than a hydrophobic nature. As demonstrated using individual RNP components, vRNA and RNA-free protein structures, M protein formed complexes only with vRNA, and the complex formation was salt-dependent. Analysis of products formed in the in vitro system containing RNP of FPV in the presence of the M protein showed impairment in the transcription of all RNA segments. The degree of inhibition correlated with the size of a segment, transcription of high molecular weight RNA segments being inhibited significantly more than that of low molecular weight RNA segments.

The Potential of Influenza HA-Specific Immunity in Mitigating Lethality of Postinfluenza Pneumococcal Infections

Influenza virus infections pre-dispose an individual to secondary pneumococcal infections, which represent a serious public health concern. Matching influenza vaccination was demonstrated helpful in preventing postinfluenza bacterial infections and associated illnesses in humans. Yet, the impact of influenza hemagglutinin (HA)-specific immunity alone in this dual-infection scenario remains elusive. In the present study, we assessed the protective effect of neutralizing and non-neutralizing anti-hemagglutinin immunity in a BALB/c influenza-pneumococcus superinfection model. Our immunogens were insect cell-expressed hemagglutinin-Gag virus-like particles that had been differentially-treated for the inactivation of bioprocess-related baculovirus impurities. We evaluated the potential of several formulations to restrain the primary infection with vaccine-matched or -mismatched influenza strains and secondary bacterial replication. In addition, we investigated the effect of anti-HA immunity on the interferon status in mouse lungs prior to bacterial challenge. In our experimental setup, neutralizing anti-HA immunity provided significant but incomplete protection from postinfluenza bacterial superinfection, despite effective control of viral replication. In view of this, it was surprising to observe a survival advantage with non-neutralizing adaptive immunity when using a heterologous viral challenge strain. Our findings suggest that both neutralizing and non-neutralizing anti-HA immunity can reduce disease and mortality caused by postinfluenza pneumococcal infections.

Pharmacoepidemiological research of COVID-19 in the Russian Federation EGIDA-2020

Aim. An analysis of coronavirus infection in Russia and evaluation of different AVT regimens effectiveness. Materials and methods. The study involved a retrospective analysis of 1082 patient records with laboratory-confirmed COVID-19 in 17 regions of Russia. The number of men and women was equal, mean age 48.718.1 (median 50). Patients with moderate COVID-19 (85%) versus mild COVID-19 (15%) were characterized by higher age (median 54 vs 21 years; p0.001), higher body mass index (27.8 vs 23.4; p0.001), prevalence of chronic diseases (75.3% vs 8.5%; p0.001), including circulatory system diseases (37.8%). Moderate COVID-19 characterized higher intoxication (10.86.1 vs 4.22.7 days; p0.001) and catarrhal symptoms duration (10.25.4 vs 6.14.1 days; p0.001). Results. During hospitalization 92% of the patients received AVT, 77% antibiotics, and 16% corticosteroids. Umifenovir therapy resulted in a significant reduction of intoxication (8.75.5 vs 11.75.5 days; p0.001) and catarrhal symptoms duration (8.85.1 vs 12.04.9 days; p0.001) compared to the group without AVT. The usage of INF reduced intoxication symptoms compared with the group without AVT (8.97.5 vs 11.75.5; p0.05). Therapy with hydroxychloroquine, imidazolylethanamide pentandioic acid, and lopinavir + ritonavir combination did not affect the course of COVID-19. Most of adverse reactions were related to antibiotics. Conclusion. Umifenovir therapy and inclusion of interferon in AVT regimens was associated improvement in the clinical manifestation of the disease among patients.

Studies of proteins soluble in acidic chloroform-methanol isolated from crude human leukocyte interferon preparations

Acidic chloroform-methanol soluble proteins possessing hydrophobic properties and capable of inhibiting in vitro transcriptase activity of influenza virus RNP were detected in native and partially purified human leukocyte interferon (IFN) preparations. Purification of IFN resulted in the removal of at least a portion of such proteins; however, no proteins have been found in highly-purified IFN preparations.

[Use of monoclonal antibodies for studying the classical hog cholera virus]

Numerous monoclonal antibodies (MAb) to hog cholera virus are a highly specific and effective instrument for studies of this agent. Panels of MAb for differential diagnosis of Pestiviruses are characterized. International reference panel of 30 MAbs is a result of cooperation of European scientists; it was approved as the official reference for assessing all available and new diagnostic agents. MAb permit intraspecies differentiation between hog cholera virus strains and, which is particularly important, between vaccine and field strains. Study of antigenic structure and functional characteristics of surface proteins of the virus with the use of MAb panels helped single out and map the functions of four antigenic sites of surface glycoprotein E2 and detect a relationship between RNAse activity and structural component of another surface glycoprotein E0.

[Susceptibility of pandemic influenza virus A 2009 H1N1 and highly pathogenic avian influenza virus A H5N1 to antiinfluenza agents in cell culture]

The data on cytotoxicity and antiviral activity of commercial antivirals, such as Remantadine, Oseltamivir, Arbidol and Ribavirin in the MDCK cell culture infected with highly pathogenic (H5N1) and pandemic 2009 (H1N1) influenza A viruses are presented. The study of the antiviral activity of antivirals in the MDCK cells culture demonstrated that Arbidol, Rimantadine and Ribavirin efficiently inhibited reproduction of the highly pathogenic H5N1 influenza viruses isolated from sick birds. Arbidol and Oseltamivir carboxylate selectively inhibited reproduction of the pandemic 2009 H1N1 influenza A viruses with changed specificity to the cell receptors, causing severe influenza in men, while remantadine had no effect on their reproduction.

[Umifenovir and coronavirus infections: a review of research results and clinical practice]

Coronaviruses are known to cause acute respiratory infections. Antiviral therapy, including for COVID-19, is based on clinical practice, experimental data and trial results. The purpose of this review is to: provide and systematize actual preclinical data, clinical trials results and clinical practice for antiviral agent umifenovir (Arbidol). Databases Scopus, Web of Science, RSCI and medRxiv were used for publication searching from 2004. A meta-analysis of clinical trials results was performed. Umifenovir is antiviral agent, it belongs to fusion inhibitors, interacts with SARS-CoV-2 spike protein. Umifenovir the impede the trimerization of spike glycoprotein and inhibit host cell adhesion, at the level of the coronaviruses S-protein of interaction with ACE2 receptor. Preclinical studies in vitro and on animals show umifenovir activity against a number of coronaviruses, including SARS-CoV, MERS-CoV, SARS-CoV-2, and others. Umifenovir, in combination with other antiviral drugs, symptomatic or traditional medicine, was used in China to treat patients with COVID-19, resulting in reduced mortality, virus elimination, the frequency of more severe course and complications in middle severity. However, antiviral therapy for the treatment of severe patients, with ARDS, did not lead to improved outcomes. In comparative clinical studies, umifenovir showed similar effectiveness with other antiviral drugs, and lower frequency of adverse reactions. Therapy with umifenovir, led to an increase percentage of patients with negative results of PCR tests on days 714 (I2=69.8%, RR 0.48, 95% CI 0.190.76; p=0.001). The efficacy and safety of antivirals against SARS-CoV-2 still requires clinical investigation. Moderate forms of COVID-19 could be effectively treated by antivirals, but severe forms of COVID-19, characterized by pulmonary immunopathology, require different approaches to treatment.

[Effects of remantadine on fusion of lipid membranes of influenza A virus with plasma and internal membranes of lymphoblastic cells]

The method of fluorescence dequenching was used to study the interaction between influenza virus A/Krasnodar/101/59 and Namalwa and Raji lymphoblastoid cells. Experiments with endocytosis inhibitors and fluorescence quenchers have shown that at pH = 5.0 the virus lipid envelopes are fused with the plasma membranes of the cells, and at pH = 7.4 the virus lipid envelopes are fused with the internal, presumably endosomal, membranes of the cells. Remantadine at a concentration of 50-1000 micrograms/ml did not influence the fusion of virus lipid envelopes with intracellular membranes at pH = 7.4 whereas at pH = 5.0 it inhibited, beginning from 25 micrograms/ml concentration, the fusion of virus lipid envelopes with the plasma membranes of cells.