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.

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.

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Potato virus X (PVX) and some other potexviruses can be reconstitutedin vitrofrom viral coat protein (CP) and RNA. PVX CP is capable of forming viral ribonucleoprotein complexes (vRNP) not only with homologous, but also with foreign RNAs. This paper presents the structure and properties of vRNP assembledin vitroupon incubation of PVX CP and RNAs of various plant and animal viruses belonging to different taxonomic groups. We have shown that the morphology and translational properties of vRNPs containing foreign (heterologous) RNA are identical to those of homological vRNP (PVX RNA – PVX CP). Our data suggest that the assembly of the “mixed” vRNPin vitrocould be started at the 5’-proximal region of the RNA, producing a helical structure of vRNPs with foreign nucleic acids. The formation of heterologous vRNPin vitrowith PVX CP appears not to require a specific 5’ end RNA nucleotide sequence, and the PVX CP seems to be able to pack foreign genetic material of various sizes and compositions into artificial virus-like particles.

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

A b s t r a c tPotato virus X (Potexvirus) is an important pathogen of number of economically significant agricultural plants of the Solanaceae family. Potato virus X (PVX) virions are flexible filamentous particles 515 nm in length and 13.5 nm in diameter with a helical structure. PVX genome consists of a single-stranded RNA (6435 nucleotides) which is capped and polyadenylated. The study of various stages of the infection process of plant viruses during infection, including the assembly of viral particles is of great practical interest. Identification of these mechanisms can be the basis for developing new approaches in virus-free crop production. Herein, the initial stages of potato virus X (PVX) virion assembly were examined on the example of virus-like particles (VLPs) produced by incubation of PVX RNA with PVX coat protein (CP) in vitro. The formation of identical set of VLP with discrete size under different incubation conditions (ionic strength, pH) was shown. However, the amount of VLP of a different size changes depending on incubation conditions. Most efficient VLP similar to the native virion size assembly has been achieved in a buffer of low ionic strength at pH 8.5. PVX RNA fragments from 800 to 5700 nt in length which were protected by coat protein within VLPs were isolated. Their individual analysis confirmed that all of them represent the 5´-terminal fragments of the genomic PVX RNA of different lengths. Thus, it was revealed that RNAs within VLP are genomic RNA 5´-terminal fragments of different lengths. PVX virions assembly initiation at the RNA 5´-end which is cooperatively extending in the 5´-to 3´-end direction was confirmed. Nucleotide sequence analysis of RNA fragments isolated from VLP of different sizes showed that sites capable to form RNA hairpins were discovered near the RNA 3´-end. They could act as «stop-signals» that prevent CP and RNA interaction and continuous cooperative assembling PVX VLP and virions. Probably, CP could «melt» RNA hairpins more or less efficiently and overcome «stop-signals» during the viral particles formation, depending on the conditions of incubation with the RNA in vitro.Êeywords: plant viruses, potato virus X, virus-like particles, RNA, coat protein, virion assembly.