Hemorrhagic fevers of the family Bunyaviridae

The Bunyaviridae family numbers more than 250 serotypes of the viruses that make up the five genera: Bunyavirus, Phlebovirus, Nairovirus, Hantavirus, Tospovirus. Typical viruses of these genera are: Bunyamver virus, Sicily mosquito fever virus, Nairobi sheep disease virus and Hantaan virus, respectively. Tospoviruses are non-pathogenic to humans and affect plants.

The prototype virus of this family is the first isolated in Central Africa mosquito-borne Bunyamver virus (the name of the virus is given in the Bunyamvera area in Uganda).

Characteristics of hemorrhagic fevers of the family Bunyaviridae

Name	The genus of the virus	The transporter	Spread
GL of the Rift Valley (Rift Valley GL)	Phlebovirus	Aedes mcintoshi, Aedes vexans and others	Tropical Africa
Crimea-Congo GL	Nairovirus	Ixodes ticks of the genus Hyalomma	Africa, the south of Russia, the countries of the Middle East, Central Asia, the Balkans, China
Hemorrhagic fever with renal syndrome	Phlebovirus	Aedes mcintoshi, Aedes vexans and others	Tropical Africa
Crimea-Congo GL	Hantavirus	Mouse rodents	Europe Asia.
Hemorrhagic fever with renal syndrome	Hantavirus	Mouse rodents	Europe Asia.
Hantavirus Pulmonary Syndrome	Hantavirus	Rats and mice of various genera	South and North America

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10],

Stability of viruses to the action of physical and chemical factors

Bunyaviruses are sensitive to the action of ether and detergents, are inactivated upon heating to a temperature of 56 ° C for 30 minutes and almost instantaneously at reflux, but they retain their infectious activity for a long time during freezing. Bunyaviruses are stable in a very limited range of pH values of 6.0-9.0, are inactivated by commonly used disinfectants.

Morphology

Virions have an oval or spherical shape with a diameter of 80-120 nm, with electron microscopy resemble a donut. These are complex RNA genomic viruses containing three internal nucleocapsids with a spiral type of symmetry. Each nucleocapsid consists of a nucleocapsid protein N, a unique single-stranded minus-RNA, and a transcriptase enzyme (RNA-dependent RNA polymerase). Three RNA segments associated with nucleocapsid are designated by size: L (long) - large, M (medium) - medium and S (short) - small. RNA does not have an infectious activity. Unlike other viruses with minus-RNA genome (Orthomixoviridae, Paramixoviridae and Rhabdoviridae), bunyaviruses do not contain M-protein, so they are more ductile. The core of the virion containing ribonucleoprotein (RNP) is surrounded by a lipoprotein envelope, on the surface of which there are spines - glycoproteins G1 and G2, which are encoded by the M segment of RNA.

Antigens

The protein N is a carrier of group-specific properties and is identified in the DSC. Glycoproteins (G1 and G2) are type-specific antigens detected in PH and RTGA. These are protective antigens, which determine haemagglutinating properties, which in bunyaviruses are not as pronounced as in orthomixo- and paramyxoviruses. They induce the formation of virus neutralizing antibodies. Glycoproteins are the main determinants of pathogenicity, which determine the cellular organotropic nature of viruses and the effectiveness of their transmission by arthropods.

On the basis of the analysis of cross-linking in the RSK, bunyaviruses are combined into genera within which, on the basis of crossed RN and RTGA, they are divided into serogroups.

[11], [12], [13], [14], [15], [16], [17], [18], [19]

Reproduction of bunyavirus

Reproduction of bunyavirus occurs in the cytoplasm of the cell, where RNP is first formed. Three kinds of mRNA are formed, each of which encodes the corresponding polypeptide - L, N and the precursors of proteins G1 and G2. Viral proteins in the infected cell are synthesized quickly. So, protein N can be detected after 2 hours, and G1 and G2 - after 4 and 6-8 hours, respectively. Maturation of viruses (the acquisition of an external lipid-containing envelope) as a result of budding RNP, unlike other viruses, occurs not on the plasma membranes of the cell, but when passing through the walls of vesicles in the region of the Golgi apparatus. Subsequently, the viral particles are transported to the plasmolemma (cell membrane). The yield of viral particles occurs by exocytosis, and sometimes by cell lysis. Bunyaviruses, like other representatives of arboviruses, have the ability to multiply in two temperature regimes: 36-40 and 22-25 ° C, which allows them to reproduce not only in the body of vertebrates, but also in the body of carriers - blood-sucking arthropods.

Features of bunyavirus cultivation and susceptibility to laboratory animals

Bunyaviruses are susceptible to newborn white mice, white rats and hamsters when infected in the brain. Cell cultures from vectors, human embryonic kidneys, BHK-21, chicken embryo fibroblasts are used to cultivate viruses, where they do not exert a pronounced CPD. Viruses can be cultured in chick embryos. A universal model for isolating arboviruses is the infection of newborn white mice, in which they cause the development of encephalitis, which ends lethal.

[20], [21], [22], [23], [24], [25], [26],