Lora Simeonova

Rimantadine and oseltamivir demonstrate synergistic combination effect in an experimental infection with type A (H3N2) influenza virus in mice

We studied the combination effect of rimantadine hydrochloride and oseltamivir phosphate on mice infected with influenza A/Aichi/2/68 (H3N2) virus. Compounds were simultaneously administered in a 5-day-treatment course, starting 4 h before intranasal infection with 10 or 20 viral 50% mouse lethal doses. Initially, we tested combinations of oseltamivir (0.05, 0.1 and 0.2 mg/kg/day) and rimantadine (2.5, 5.0 and 7.5 mg/kg/day). Significant differences were recorded between combinationtreated groups, and groups with separately applied compounds and the placebo group, such as: protection index of oseltamivir with 5.0 or 7.5 mg/kg rimantadine varied between 34–41% and 43–87%, respectively, whereas the individual effects of oseltamivir, 5 mg/kg of rimantadine and 7.5 mg/kg of rimantadine were 0–10%, 0% and 18.7–29.6%, respectively; mean survival time in combination-treated groups was lengthened by 3.1–6.9 days, in oseltamivir groups by 0–1.9 days, and in rimantadine groups by 0.8–1.3 days at 5 mg/kg and 2.6–3.2 days at 7.5 mg/kg. The three-dimensional method of Prichard and Shipman characterized the combination effect as synergistic. Further, we studied the activity of 0.05 mg/kg/day of oseltamivir combined with 5 mg/kg of rimantadine. Lung virus titre in Madin Darby canine kidney cells, lung index and consolidation score proved the high effectiveness of the combination. When compared with the placebo group, a 2.8 log10 lower titre of 50% cell culture infectious dose (CCID50) was recorded in the combination-treated group at 48–60 h post-infection (the peak of lung virus growth). This is in contrast to the 0.1–1.0 log10 and 1.1–1.4 log10 reduction in CCID50 titre observed in the oseltamivir and rimantadine groups, respectively. These data emphasize the high anti-influenza A potential of the combination.

Combination activity of neuraminidase inhibitor oseltamivir and α-tocopherol in influenza virus A (H3N2) infection in mice

Background Influenza is a highly contagious viral infection of the respiratory system. To attack two processes involved in flu pathogenesis—viral replication in the infected body and oxidative damages, we studied the combination effect of neuraminidase inhibitor oseltamivir and antioxidant α-tocopherol in experimental model of influenza. Methods After inoculation of albino mice with 10 MLD50 (50% mouse lethal dose) of influenza virus A/Aichi/2/68 (H3N2), oseltamivir was applied orally at three doses, 2.5 mg/kg, 1.25 mg/kg, and 0.625 mg/kg, for five days post infection. α-Tocopherol (120 mg/kg, in sunflower oil) was administered intraperitoneally. Three schemes of α-tocopherol five-day course were tested: onset five or two days before infection, or on the virus inoculation day. Results Strongly dose-dependent augmented antiviral effect of the combination α-tocopherol and 0.625 mg/kg oseltamivir was demonstrated when α-tocopherol was administered simultaneously with oseltamivir: a pronounced decrease in mortality rate (a 78% protection), and a lengthening of mean survival time by 3.2–4 days. Lung parameters showed a substantial decrease in infectious virus content (Δ logs = 3.8/4.1) and a marked diminishment of lung index and pathology. Combination α-tocopherol with 1.25 mg/kg oseltamivir manifested a marked protective effect, but the effect on lung parameters was less. The combination effect of α-tocopherol with 2.5 mg/kg oseltamivir did not surpass the monotherapeutic effect of oseltamivir. When α-tocopherol was applied in courses starting five or two days before infection, its combination with oseltamivir was ineffective. Conclusions Evidently, α-tocopherol could be considered as prospective component of influenza therapy in combination with oseltamivir.

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) Fentons (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.

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.

Chemotherapy of Influenza: Current and Novel Approach

ABSTRACT Influenza virus infection attacks huge contingents of the global population in periodic epidemics and pandemics and not rarely is manifested with a severe course, complications and mortality. So far two groups of anti-influenza chemotherapeutics have been licensed and used for prophylaxis and therapy of flu every year—adamantanes (M2 blockers) and neuraminidase inhibitors (NAIs). Since the drug resistance to both groups has been increasing constantly and the risk of flu pandemics still exists, alternative effective inhibitory strategies, like antivirals combinations, should be designed and applied in complicated epidemiological situations with co-circulating influenza subtypes susceptible to different drugs. At the same time discovery of novel antivirals with high activity and selectivity is a matter of great importance and is underway. Both directions will be shortly described in this review.