E.K. Petrova

Influenza virus aerosols in the air and their infectiousness.

Influenza is one of the most contagious and rapidly spreading infectious diseases and an important global cause of hospital admissions and mortality. There are some amounts of the virus in the air constantly. These amounts is generally not enough to cause disease in people, due to infection prevention by healthy immune systems. However, at a higher concentration of the airborne virus, the risk of human infection increases dramatically. Early detection of the threshold virus concentration is essential for prevention of the spread of influenza infection. This review discusses different approaches for measuring the amount of influenza A virus particles in the air and assessing their infectiousness. Here we also discuss the data describing the relationship between the influenza virus subtypes and virus air transmission, and distribution of viral particles in aerosol drops of different sizes.

The role of the 5′-cap structure in viral ribonucleoproteins assembly from potato virus X coat protein and RNAs

The potato virus X (PVX) virion can be reconstituted in vitro from the virus coat protein (CP) and RNA; heterologous RNAs may be used as well. In our recent study, structure and properties of cognate and heterologous viral ribonucleoproteins (vRNPs) were demonstrated to be similar to those of native virions. The assembly was found to be initiated at the 5 terminus of an RNA and was not dependent on RNA sequence. The aim of the present study was to search for a signal or an essential structural element that directs packaging of viral genetic material into vRNPs. vRNPs were formed by incubation of the PVX CP with heterologous capped RNAs, their functional fragments lacking the cap structure, as well as the capped and uncapped transcripts corresponding to the 5-terminal region of the genomic PVX RNA. Experimental data show that the presence of the cap structure at the 5 end of a nucleic acid is an important condition for vRNP assembly from RNA and CP. Presumably, the 5-cap affects conformational state of the RNA region responsible for the efficient interaction with CP and creates conformational encapsidation signal for vRNP assembly.

The 5′-proximal region of Potato virus X RNA involves the potential cap-dependent “conformational element” for encapsidation

Filamentous helical Potato virus X (PVX) can be regarded as one of the well-studied viruses. Nevertheless, some aspects of the PVX assembly remained obscure. Previously, we have shown that the presence of a cap structure at the 5 end of PVX RNA is indispensable for assembly of viral ribonucleoprotein (vRNP) particles varying in length. Here, most significantly, removal of the cap structure from previously capped PVX RNA did not affect the efficiency of decapped RNA molecules to be assembled into vRNP. This result provided evidence that the cap structure by itself does not act as a signal for initiation of vRNP assembly. These observations allowed to presume that the capping triggers some spatial changes in the 5-proximal site of PVX RNA creating a conformational encapsidation signal for vRNP assembly, which is capable of triggering vRNP assembly in the absence of cap structure. Apparently, during capping the 5-proximal segment of PVX RNA acquires a unique conformation which is stable to be retained even after cap removal.

Stimulated low-frequency Raman scattering in a suspension of tobacco mosaic virus

The interaction of laser pulses with tobacco mosaic virus (TMV) in Tris-HCl pH7.5 buffer and in water has been investigated. Ruby laser pulses of 20 ns duration have been used for excitation. The spectrum of the light passing through the sample was registered with the help of a Fabry–Perot interferometer. In the case of TMV in water we observed in the spectrum only one line of the exciting laser light, but for TMV in Tris-HCl pH7.5 buffer a second line appeared, corresponding to stimulated low-frequency Raman scattering (SLFRS) on the breathing radial mode of TMV. The frequency shift of the SLFRS by 2 cm−1 (60 GHz), the conversion efficiency and the threshold are measured for the first time to the best of our knowledge.

Thermal conversion of filamentous potato virus X into spherical particles with different properties from virions.

We developed a method for the fast transformation of virions of tobacco mosaic virus (TMV) in so‐called spherical particles (SPs) of different sizes. These SPs turned out to be highly useful for the preparation of different kinds of important biotechnological products. In this communication, we report that a representative of the flexuous helical virus group—potato virus X (PVX), produces SPs as well, but these SPs differ from TMV SPs in several important aspects. PVX SPs may be useful biotechnological devices.

The key role of rubella virus glycoproteins in the formation of immune response, and perspectives on their use in the development of new recombinant vaccines

Rubella is a highly contagious viral disease which is mostly threatens to women of reproductive age. Existent live attenuated vaccines are effective enough, but have some drawbacks and are unusable for a certain group of people, including pregnant women and people with AIDS and other immunodeficiency. Thereby the development of alternative non-replicating, recombinant vaccines undoubtedly is needed. This review discusses the protein E1 and E2 role in formation of immune response and perspectives in development of new generation recombinant vaccines using them.

Stimulated low-frequency Raman scattering in viruses

Stimulated low-frequency Raman scattering (SLFRS), caused by laser pulses interaction with the radial breathing modes of tobacco mosaic virus (TMV) in Tris-HCl pH7.5 buffer was registered. SLFRS frequency shift, conversion efficiency and threshold are measured.

Study of the Potexvirus Ribonucleoproteins Signal of Assembly

Formation of viral ribonucleoprotein particles during incubation of the Alternanthera mosaic virus 5’-end transcripts with Potato virus X (members of the Potexvirus genus) coat protein was studied. It was shown that the capping of Alternanthera mosaic virus transcripts affects the efficiency of their interaction with a coat protein. At the same time, the removal of the cap structure from previously capped Alternanthera mosaic virus transcripts did not prevent assembly of viral ribonucleoproteins. The removal of the first 100 nucleotides (the likely site for assembly initiation) had no effect on the formation of viral ribonucleoproteins. The additional evidences that the potexvirus ribonucleoproteins assembly does not depend on the RNA nucleotide sequence were obtained.