In medicine, special research methods have been developed for the diagnosis of diseases with a viral nature. This is necessary in order to identify the virus, study its biology and the ability to affect the cells of an animal and a person. Thus, it becomes possible to understand the pathogenesis of viral diseases and, accordingly, to choose the right treatment method.
What is the diagnosis?
Viruses multiply in living cells. To study it, cultivation is necessary at the level of the experimental organism or cell culture. To do this, in medical practice and microbiology in general, virological research methods are carried out, which have the following main approaches:
- straight;
- indirect;
- serological.
The material can be examined directly for the presence of nucleic acids, a viral antigen, or, for example, to isolate and identify the virus from clinical material.
In addition to the ability to establish the etiology of the disease, monitoring the therapeutic effect, virological research methods play a large role in anti-epidemic measures. Chicken embryos, laboratory animals or cell cultures are used to isolate and cultivate the virus .
How to research?
The fastest is the direct method. It allows you to detect a virus, antigen or NK (nucleic acid) in the clinical material itself. It takes time from two hours to a day.
- EM - electron microscopy. It detects the virus directly.
- IEM - immune electron microscopy. Uses specific antibodies to viruses.
- RIF - immunofluorescence reaction. Uses dye bound antibodies. Such virological research methods are widely used as a quick decoding of the etiology of acute respiratory viral infections (acute respiratory viral infections) when smears are taken from the mucous membrane of the upper respiratory tract.
- ELISA - enzyme-linked immunosorbent assay - determination of viral antigens, similar to RIF, but based on the labeling of antibodies with enzymes.
- RIA - radioimmunoassay. Uses a label of antibodies with radioisotopes to ensure high sensitivity in determining the viral antigen.
- Molecular - NK hybridization or virus genome isolation using PCR (polymerase chain reaction).
- Cytology - rarely used, but with certain infections, these virological methods of research are very effective. Biopsy, autopsy, and smear materials are examined, processed for staining and analysis under a microscope.
What is the point of research?
To successfully isolate viruses, clinical material is taken in accordance with pathogenesis and as early as possible. Often this process requires several passages before applying specific virological research methods.
Microbiology studies microscopic creatures. And her area is not only medicine. It is a fundamental science for agriculture, veterinary medicine, the space and technical industries, and geology.
But of course, everything is created for man and his development on this beautiful planet. Therefore, it is very important to detect danger in time and neutralize it. Viruses are different from bacteria. These are structures that enter the body and cause the formation of a new generation. They are similar to crystals and are aimed at controlling the process of their reproduction, although they themselves do not feed, do not grow and do not secrete metabolic products.
The virus is capable of causing severe illness in any living organism in which it enters. Moreover, it can evolve. That is why virological research methods in microbiology should be developed and improved, since human civilization as a whole may be at risk.
Materials
To detect and identify viruses in medicine, as a rule, the following are taken:
- nasopharyngeal flushing (respiratory infections);
- flushing and feces (enterovirus infections);
- scrapings, contents of the vesicles (skin lesions, mucous membranes like herpes, chickenpox);
- swabs (exanthemic infections like measles, rubella);
- blood, cerebrospinal fluid (arbovirus infections).
Phases
All stages of the virological research method include:
- material intake;
- selection, obtaining a test system, determining its viability;
- infection of the test system;
- virus indication;
- determination of the type of virus.
In general, pathogenic viruses are distinguished by the presence of tissue and type specificity. Take, for example, poliovirus, which is reproduced only in primates (in their cells). Accordingly, a specific tissue culture is used to isolate a specific virus. If we are talking about an unknown pathogen, then it would be advisable to simultaneously infect three, and preferably four, cell cultures.
Thus, perhaps one of them will be sensitive. To determine the presence of the virus in infected cultures, one looks at the development of specific cell degeneration, intracellular inclusions, the detection of a specific antigen, and positive hemagglutination and hemadsorption reactions.
All virological research methods (direct and indirect, serological) should be selected as the most suitable for the specific case of the alleged infection.
Indirect methods are based on the isolation and identification of the virus. They are laborious, time consuming, but accurate.
Serodiagnosis
Such diagnostics means a method based on the antigen-antibody reaction. Most often, paired blood serums are used, taken at intervals of several weeks. If the increase in antibody titer is 4 or more times, the reaction is considered positive. To determine the type-specificity of the virus, a neutralization reaction is used. To determine group specificity, a complement binding reaction needs to be obtained.
Various variants of enzyme immunoassay, the inhibition of hemagglutination inhibition, passive hemagglutination, reverse passive hemagglutination, and RIF are widely used. Even in genetic engineering, a method for producing monoclonal antibodies was developed. The narrow specificity of monoclones can be overcome by using several monoclonal antibodies to various viral determinants. Thus, the specificity and sensitivity of the study with the determination of antigens was increased.
Some features
Today, many different test systems have been created for the immunological diagnosis of infections resulting from the ingress of the virus into a living organism.
Thus, virological research methods are methods for isolating viruses, studying their properties and establishing their etiological connection with certain diseases.
As for the animals used in these studies, they should be quite susceptible to a specific viral infection, they should not be carriers of latent infections and any parasites. The type of animal, its age, breed, body weight, fatness, gender and living conditions also matter. The experiment involved animals of the same species, age, with the same conditions of detention. Sometimes different types of animals can be used, with different sensitivity to the same virus. This helps to identify the whole variety of infectious forms.