General Characteristics of herpesvirus
In this article, we will understand about General Characteristics of Herpesvirus. Among the viral diseases, AIT occupies a leading position. It is due to the widespread proliferation of herpes viruses (HBV), a variety of clinical manifestations of disease, usually chronic course, and different ways of transmission of infection (Barinskaja JF et al., 1986).
GW combined into large family Herpesviridae and is currently the most strictly classified. The family Herpesviridae comprises more than 70 members, of which most human pathogenic viruses are herpes simplex virus types 1 and 2 (HSV-1, HSV-2), varicella zoster virus and herpes zoster (VOG), cytomegalovirus (CMV), the virus Epshteyn - Barr (EBV), human herpesvirus type 6 (HHV-6), human herpesvirus 7-type (HHV-7). There are reports of identification of human herpesvirus 8-type.
Size virionau herpesviruses range from 100 to 300 nm. Various representatives of the GW have some standard features in the structure of the virions. They are described by spherical shape and the presence of 4 structural components: core, capsid, the inner membrane (tegument), the outer shell (envelope). The core contains the linear dvunitchatuyu viral DNA, the molecular weight of which varies from 80 - 100 x 10s long-tone (HSV) to 145 x 10s daltons (human cytomegalovirus). As part of virions detected more than 30 proteins (glycoproteins), seven of which (gB, gC, gD, gE, gF, gG and gX) are on the surface and cause the formation of virus-neutralizing antibodies. Six glycoproteins are part of the capsid. Many of the dozens of proteins, including timidinki-Nazarov, are non-structural and are produced during the viral life cycle. Among other proteins unique to the GW should be called DNA polymerase and a protein associated with DNA * The penetration of HBV into the host cell is a complex multistep process and involves the attachment of virions to cellular receptors, endocytosis and membrane fusion of virions and cells. As a result, the capsid is released from the proteins of the outer shell, and the complex DNA-protein of the virus? Arises in the nucleus. Virion DNA released in the nucleoplasm and here transcribed cellular RNA polymerase. Distinguish between very early, rapid and late transcription. The result is a series of sequential processes: the processing of mRNA, the synthesis of encoded products and a partial return of their transport into the nucleus, DNA replication, and formation of daughter molecules. Formed in the nuclei of cells are immature cap-oxides by budding penetrate the nuclear membrane into the cytoplasm, and endoplasmic reticulum cisterns end formation of mature capsid and the outer shell of the virus, followed by transport to the surface and release them from the cells (Table I).
Synthesis of viral proteins, as shown in the experiment, starting 2 hours after infection, and the maximum number is stored in about 8 hours. Infectious virions appear within 10 hours and achieve the highest titers after 15 hours. It is significantly inhibited the synthesis of its cell proteins. In the replication of viral DNA is dominated by the belkovosinteticheskie structure of cell DNA. However, its implementations are essential viral genes and their products.
Viral DNA, consisting of 80 genes, divided into sub-groups of genes: a, b, g. Expression of these groups of genes and thus the synthesis of proteins encoded by them are subject to a cascade of regulation, and genes - the first group of genes that are transcribed by RNA polymerase and do not require transcription for the presence of de novo synthesized proteins. Currently, some mapped genes and study the properties of proteins encoded by herpes viruses. For example, a protein involved in establishing the ICP of the latent state of HSV-1 and its reactivation, and protein ICP-4 are required for the expression of the second group of gene-b. B-gene products - it's virus-specific DNA polymerase and thymidine kinase times required for the biosynthesis of DNA GW. Other b-proteins turn off the gene expression of a host cell and a gene-HS and initiate the work of the third group of genes - g.
Proteins encoded by a group of g-genes are the structural virion polypeptides and are mainly represented by membrane glycoproteins A, B, C, D, E, F, G, which play a significant role in the immunopathogenesis of HBV. The studies demonstrated Norrild V. their important role in the penetration of HSV into the cell and in the phenomenon simplastoobrazovaniya. For example, glycoprotein D (gD) is about groups and tipospedifi-cal antigenic determinants, being the most-antigen but significant protein. In response to the immunization of gD-specific antibodies are formed, characterized by high affinity and play an important role in the neutralization of HSV. Another protein - gC constitutes interest, as functions as a receptor for the C 3 fraction of complement by blocking the alternative and classical pathway of complement activation and lysis of preventing HBV-infected cells. Some researchers believe that gC HSV-1 plays a significant role in virus adsorption on cells and infectivity of the virus. Glycoprotein E can bind Fc-fragment of immunoglobulin G (IgG), impede the implementation of antibody-dependent lysis of target cells.
Thus, the SH glycoproteins expressed in virus-infected cells (including immune system cells), leading to a change in their phenotypic properties, i.e., the transformation. Transformation of cells causes the development of individual immunopathological reactions directed against your own body and is one of the mechanisms virusindutsirovannoy immunosuppression. Thus HS may lead to the development of primary immunodeficiency, but the most severe clinical forms of AIT observed in individuals with immunodeficiency, due to other causes, including HIV infection (Isakov VA, Safronova, MM, 1997).
Until recently, the laboratory diagnosis of AIT was carried out only in specialized virology centers. The emergence of new research methods in the last decade has led to the empowerment of virological diagnosis AIT in sound public health. Modern methods of laboratory diagnosis of AIT, you can: receive the analysis results in a short time (hours, sometimes - minutes), to undertake and complete the study without isolation of virus cultures, using only native materials; receive adequate reliability of the analysis, given the high specificity and sensitivity of methods.
Most methods of laboratory diagnosis of AIT based on the mutual strictly specific interaction of antigen (AG) and antibodies (AT), allowing you to detect viral AG quickly and AT to them in body fluids. However, many of the proposed methods are simple, convenient and reproducible in hospital laboratories, thus increasing the possibility of the diagnosis of AIT in medical institutions in various fields. No less important, these methods have in epidemiological practice, contributing to rapid epidemiological analysis and the formation of targeted anti-epidemic measures in the outbreak of viral infection.