[Evolution of pandemic influenza virus A(H1N1)pdm09 in 2009-2016: dynamics of receptor specificity of the first hemagglutinin subunit (HA1).]

INTRODUCTION

The new reassortant of the swine flu virus A(H1N1)pdm09, which emerged in 2009, overcame the species barrier and caused the 2009-2010 pandemic. One of the key points required for the influenza virus to overcome the species barrier and adapt it to humans is its specific binding to the receptors on the epithelium of the human respiratory tract.

PURPOSE

Studying the dynamics of changes in receptor specificity (RS) of the HA1 subunit of the hemagglutinin of the influenza A(H1N1)pdm09 virus strains isolated during the period 2009-2016 on the territory of the Russian Federation, and an analysis of the possible impact of these changes on the incidence rates of the population of the Russian Federation of pandemic influenza in certain epidemic seasons.

MATERIAL AND METHODS

Standard methods of collecting clinical materials, isolation of influenza viruses, their typing and genome sequencing were used. For the study of RS of influenza A virus (H1N1)pdm09, the method of solid phase sialosidenzyme analysis was used.

RESULTS

It is shown that the change in the parameter W_3/6 , which characterizes the degree of a2-3 receptor specificity (a2-3-RS) of the influenza virus A(H1N1) pdm09 over a2-6-RS, coincides with the change in the incidence rates of the Russian Federation's pandemic flu in separate epidemic seasons. There is a tendency to increase the affinity of the virus A(H1N1)pdm09 to α2-3 analogs of the sialyl-glycan receptors of the human respiratory tract epithelium - α2-3-sialoglycopolymers (α2-3-SGP), and falls to α2-6-SGP, with the virus showing the greatest affinity for sulfated sialoglycopolymers.

DISCUSSION

Screening for RS strains of influenza A (H1N1)pdm09 virus isolated on the territory of the Russian Federation in 2009-2016 revealed a decrease in the affinity of viruses for a2-6-sialosides, especially for 6'SL-SGP, which is probably due to the presence of amino acid substitutions in the 222 and 223 positions of RBS HA1 viruses. Previous studies have shown that the presence of such substitutions correlates with an increase in the virulence of the influenza A virus (H1N1)pdm09 [16, 23]. Probably, the pandemic virus has evolved towards the selection of more virulent pneumotropic variants.

CONCLUSION

Monitoring of the receptor specificity of a pandemic influenza virus makes it possible to identify strains with altered RS to the epithelium of the human respiratory tract and an increased ability to transfer from person to person. Change in the period 2009-2016 the W_3/6 parameter characterizing the degree of α2-3-RS excess of the influenza A(H1N1)pdm09 virus over α2-6-RS, coincides with the change in the incidence rates of the pandemic influenza population of the Russian Federation in certain epidemic seasons.

Mechanical Transformation of Compounds Leading to Physical, Chemical, and Biological Changes in Pharmaceutical Substances

This study demonstrates the link between the modification of the solid-phase pharmaceutical substances mechanical structure and their activity in waters with different molar ratio «deuterium-protium». Mechanochemical transformation of the powders of lactose monohydrate and sodium chloride as models of nutrients and components of dosage forms was investigated by the complex of physicochemical and biological methods. The solubility and kinetic activity of substances dispersed in various ways showed a positive correlation with the solvent isotope profile. Substances dissolved in heavy water were more active than solutes in natural water. Differential IR spectroscopy confirmed the modification of substituents in the sample of lactose monohydrate, demonstrating physicochemical changes during mechanical intervention. The biological activity of the compounds was determined by the method of Spirotox. The activation energy was determined by Arrhenius. Compared with the native compound, dispersed lactose monohydrate showed lower activation energy and, therefore, greater efficiency. In conclusion, proposed data confirm the statement that mechanical changes in compounds can lead to physicochemical changes that affect chemical and biological profiles.

The effect of the deuterium depleted water on the biological activity of the eukaryotic cells

Here we show the dependence of the unicellular biosensor S.ambigua lifespan on the water D/H isotopic composition. This dependence is bell-shaped with descents both in case of deficiency or excess of deuterium in water. The influence of the water D/H isotopic composition on the cell culture proliferative potential and colony forming efficiency in vitro was tested on the human dermal fibroblasts. We observed that the deuterium depleted water stimulates cell colony formation at the early passages. The dynamics of the cell doubling index in the deuterium depleted water-based growth medium showed higher proliferation potential compared to the water with normal isotopic composition. Using scratch assay, we have also studied the impact of the growth medium D/H isotopic composition on the cell motility of human cancer cell lines A549 and HT29. We have shown that the deuterium depleted water considerably suppressed cancer cell lines amoeboid movement in vitro.

Influenza A virus in the Western Arctic

Small bays of bird bazaars of the Arctic Kola Peninsula (Barents Sea) have been studied. RNA of influenza A virus was found in the surface microlayer (SM) and aerosol samples from the bays located beneath bird colonies. The nucleotide sequencing of the PCR fragments from the SM and the sea aerosol showed their identity for each bay. Virus transfer mechanism along the “surface microlayer - sea aerosol” path has been proposed. The kinetic scheme of the virus-host-environment interaction, which allows the dependence of the viral population size on the temperature to be simulated, has been developed.

[The modern approaches to the determination of the content of elemental impurities in the pharmaceutical substances with the use of inductively-coupled plasma mass-spectrometry]

The elemental impurities contained in the composition of the pharmaceutical dose forms are known to be capable of interacting with their active substances and excipients and of catalyzing their degradation; thereby, they alter stability of the drug products and exert toxic effects on the human tissues. The present publication was designed to report the results of the purity tests for ascorbic acid, valine, and galactose substances by inductively-coupled plasma mass-spectrometry (IBP-MS). This method is recommended for use by the US and EU pharmacopoeias and for the replacement of the traditional test for heavy metals with the use of PbS ethanol suspension.

[The influence of an air ionizer on the air ionic composition]

The air ionic composition in a classroom was determined during the operation of a Neo Tec XJ-2100 ionizer (Germany). The amount of ions in the air was measured before and after the switch-on of the ionizer. It was shown to vary depending on the mode of operation of the device and differ from the recommended normal values. The necessity of checking up the work of air ionizers both in living quarters and at workplaces is discussed with the application of air ion counters making it possible to carry out monitoring of the air ionic composition and estimate its compliance with the sanitary and hygienic norms.

[Prognostication of toxicity of a group of chemical compounds comprising anti-tuberculosis medicines by the quantitative structure-activity correlation method]

Balaban (J), Wiener (W), and Rouvray (R) topological indices as well as detour (Ip) and electropy (Ie) indices reflecting the structure of chemical substances were used to establish correlation between median lethal dose (LD50) of an anti-tuberculosis medicine and its molecular structure. Monocyclic compounds showed linear correlation between LD50 values and Balaban index (R = 0.93). Correlation between a maximum daily dose and electropy index was typical of the products having a more complicated structure. Results of this study open up prospects for the development of new anti-tuberculosis medicinal preparations characterized by reduced toxicity.

Laser diffraction for standardization of heterogeneous pharmaceutical preparations

A new quantitative method for standardization of heterogeneous pharmaceutical preparations and their quality control during storage based on laser diffraction is proposed. A series of pharmaceutical dosage forms--suspensions, emulsions, tinctures, decoctions, cell preparations and others, are heterogeneous medicines. In some cases disperse phase can be formed during storage as a result of layering (L1/L2) or precipitation (S/L). Laser diffraction method proposed in this study can be used for standardization and quality control of medicines.

[The role of intercellular contacts in the initiation of growth and in the development of a transiently nonculturable state by the cultures of Rhodococcus rhodochrous grown in poor media]

It was found that the growth of Rhodococcus rhodochrous cells in modified Saton's medium strongly depends on the rate of culture agitation in the flask: an agitation at 250 rpm in flasks with baffles stops cell multiplication, whereas slight agitation leads to pronounced culture growth. The growth retardation phenomenon was reversible and did not manifest itself in exponential-phase cultures or when the cells were grown in a rich medium; furthermore, it was not connected with the degree of culture aeration. When agitated at a moderate rate, the bacterial cells formed aggregates in the lag phase, which broke up into single cells in the exponential phase. The inhibitory effect of vigorous agitation was removed by the addition to the medium of the supernatant (SN) of a log-phase culture grown in the same medium with moderate agitation. Vigorous agitation is thought to interfere with the cell contacts, whose establishment is necessary for the development of an R. rhodochrous culture in a poor medium, which occurs in the form of (micro) cryptic growth. When grown in modified Saton's medium, R. rhodochrous cells were capable of transition, in the prolonged stationary phase, to a resting and transiently nonculturable state. Such cells could be resuscitated by incubation in a liquid medium with the addition of the supernatant or the Rpf secreted protein. The formation of transiently nonculturable cells was only possible under the conditions of a considerable agitation rate (250-300 rpm), which prevented secondary (cryptic) growth of the culture. This circumstance indicates the importance of intercellular contacts not only for the initiation of growth but also for the transition of the bacteria to a dormant state.

Neutron flow exposure as a test for survival of Artemia salina spores

Live and heat-inactivated Artemia salina spores (samples with the same mass and filling density) were exposed to a flow of thermal neutrons from a (252)Cf radioactive source at an equivalent dose power of about 1 microSv/h. Irradiation led to a 4-fold acceleration of nauplius development and to modification of the element profiles of live spores. The difference between absorption/diffusion of thermal neutrons by live and dead spores was revealed.

[Formation of nonculturable Mycobacterium tuberculosis and their regeneration]

Nonculturable cells were found to occur in populations of Mycobacterium tuberculosis cells during the long post-stationary phase. These cells were small (0.6-0.8 micron) ovoid and coccoid forms with intact cell walls and negligible respiratory activity, which allows them to be regarded as dormant cells. Nonculturable cells were characterized by low viability after plating onto solid medium; a minor part of the population of these cells could be cultivated in liquid medium. Cell-free culture liquid of an exponential-phase Mycobacterium tuberculosis culture or the bacterial growth factor Rpf exerted a resuscitating effect, increasing substantially the growth capacity of the nonculturable cells in liquid medium. During resuscitation of nonculturable cells, a transition from ovoid to rodlike cell shape occurred. At early stages of resuscitation, ovoid cells formed small aggregates. The recovery of culturability was associated with the formation of rod-shaped cells in the culture. The data obtained demonstrate the in vitro formation of dormant cells of Mycobacterium tuberculosis, which do not grow on solid media but can be resuscitated in liquid medium under the effect of substance(s) secreted by actively growing cells.

Kinetic mechanism of ATP synthesis catalyzed by mitochondrial Fo x F1-ATPase

Initial rates of succinate-dependent ATP synthesis catalyzed by submitochondrial particles from bovine heart substoichiometrically coupled with oligomycin were found to have hyperbolic dependencies on contents of Mg x ADP, free Mg2+, and phosphate. The results suggest that Mg x ADP complex and free phosphate are true substrates of the enzyme; and an unordered ternary complex of Fo x F1-ATPase, Mg x ADP, and phosphate is generated during the catalysis. The presence of free Mg2+ is required for the reaction. Mg2+ was a noncompetitive activator of ATP synthesis relative to Mg x ADP and a competitive activator relative to phosphate. The decrease in steady-state values of Deltamu(H)+ (by the inhibition of succinate oxidase with malonate) results in the decreased value of Vmax and in a slight decrease in Km for the substrates and Mg2+ without changes in affinity for the substrates. Based on these results, a kinetic scheme of ATP synthesis is proposed.

Kinetic mechanism of Fo x F1 mitochondrial ATPase: Mg2+ requirement for Mg x ATP hydrolysis

The initial rates of ATP hydrolysis catalyzed by Fo x F1 (bovine heart submitochondrial particles) preincubated in the presence of Pi for complete activation of the oligomycin-sensitive ATPase were measured as a function of ATP, Mg2+, and Mg x ATP concentrations. The results suggest the mechanism in which Mg x ATP complex is the true substrate of the ATPase and the second Mg2+ bound at a specific pH-dependent site is needed for the catalysis. Simple hyperbolic Michaelis--Menten dependences of the reaction rate on the substrate (Mg x ATP) and activating Mg2+ were found. In contrast to the generally accepted view, no inhibition of ATPase by free Mg2+ was found. Inhibition of the reaction by free ATP is due to a decrease of free Mg2+ needed for the catalysis. In the presence of both Ca2+ and Mg2+ the kinetics of ATP hydrolysis suggest that the Ca x ATP complex is neither hydrolyzed nor competes with Mg x ATP, and free Ca2+ does not affect the hydrolysis of Mg x ATP complex. A crucial role of free Mg2+ in the time-dependent inhibition of ATPase by azide is shown. The dependence of apparent Km for Mg x ATP on saturation of the Mg2+-specific site suggests the formal ping-pong mechanism in which bound Mg2+ participates in the overall reaction after dissociation of one product (most likely Pi) thus promoting either release of ADP (catalytic turnover) or slow isomerization of the enzyme--product complex (formation of the dead-end ADP(Mg2+)-inhibited enzyme). The rate of Mg x ATP hydrolysis only slightly depends on pH at saturating Mg2+. In the presence of limited amounts of free Mg2+ the pH dependence of the initial rate corresponds to the titration of a single group with pKa = 7.5. The simple competition between H+ and activating Mg2+ was observed. The specific role of Mg2+ as a coupling cation for energy transduction in Fo x F1-ATPase is discussed.

Contraction transitions of F1-F0 ATPase during catalytic turnover

Strong acoustic pressure was applied to submitochondrial particles (SMP) from bovine heart in order to drive ATP synthesis by F1-F0 complex for the account of sound waves. We observed a net ATP production at two narrow frequency ranges, about 170 Hz and about 340 Hz, that corresponds to the resonance oscillations of experimental cuvette when the acoustic pressure had a magnitude of 100 kPa. The results can be explained quantitatively by contractive conformational changes of F1-F0 complex during catalytic turnover. Negative staining electron microscopy of SMP preparations was used to visualize the ADP(Mg2+)-induced conformational changes of F1-F0 complex. In the particles with high ATPase activity in the presence of phosphate the factors F1 and F0 formed a congregated domain plunged into the membrane without any observable stalk in between. The presence of ADP(Mg2+) caused a structural rearrangement of F1-F0 to the essentially different conformation: the domains F1 and F0 were dislodged distinctly from each other and connected by a long thin stalk. The latter conformation resembled well the usual bipartite profile of ATPase. The data indicate that besides rotation, the catalytic turnover of ATP synthase is also accompanied by stretch transitions of F1-F0 complex.

ATP synthesis catalyzed by the mitochondrial F1-F0 ATP synthase is not a reversal of its ATPase activity

The ADP(Mg2+)-deactivated oligomycin-sensitive F1-F0 ATPase of coupled submitochondrial particles treated with the substoichiometric amount of oligomycin was studied to test whether ATP synthesis and hydrolysis proceed in either direction through the same intermediates. The initial rates of ATP hydrolysis, oxidative phosphorylation, ATP-dependent, succinate-supported NAD+ reduction, and ATP-induced delta microH+ generation were measured using deactivated ATPase trapped by azide [Biochem. J. (1982) 202, 15-23]. Three ATP consuming reactions were strongly inhibited when azide was present in the assay mixtures, whereas ATP synthesis was not altered by azide. The unidirectional effect of azide is not consistent with three alternating binding sites mechanism operating in ATP synthesis and support our hypothesis on the existence of nucleotide(Mg2+)-controlled 'synthase' and 'hydrolase' states of the mitochondrial F1-F0 ATPase.

Nucleotide/H(+)-dependent change in Mg2+ affinity at the ATPase inhibitory site of the mitochondrial F1-F0 ATP synthase

The interactions between ADP and Mg2+ that result in the slowly reversible inhibition of the mitochondrial F1-F0 ATPase were studied. The Ki for the inhibitory Mg2+ is shown to be strongly dependent on the occupation of the nucleotide-binding sites. The inhibitory binding site for Mg2+ is not seen unless a stoichiometric amount of ADP is added [Biochem. J. 276 (1991) 149-156]; it appears (Ki = 2.10(-6) M) in the presence of stoichiometric ADP and the affinity for inhibitory Mg2+ decreases to a Ki value of 7.10(-5) M when the second nucleotide binding site with Kd = 5.10(-6) M is loaded with ADP. The binding of the inhibitory Mg2+ is competitively inhibited by H+ ions within the pH interval 6.8-8.2. The nucleotide-dependent affinity transition of the Mg(2+)-specific site suggests that H+/Mg2+ exchange may play an important role in the catalytic mechanism of ATP synthesis/hydrolysis at the active site(s) of F1-F0 ATP synthase.