Medical Department or Discipline of Virology
Meaning of Virology: Virology is a new subject formed by the penetration and fusion of virology and molecular biology. Specifically, it is a molecule that studies the structure and function of the viral genome, explores the viral genome replication and gene expression. Its regulatory mechanism based on a full understanding of the general morphology and structural characteristics of the virus, thereby revealing the molecules of viral infection and pathogenicity. In essence, it provides the scientific basis and scientific basis for the development of viral genetic engineering vaccines and antiviral drugs, as well as the diagnosis, prevention and treatment of viral diseases.
Medical name: Virology
English name: Virology
History I: Tobacco mosaic
virus was discovered in 1892
History II: Confirmed that the
virus has only one nucleic acid
Table of Content
- Introduction
- History
- Basic characteris
- Purpose
- Main content
- Development process
Introduction to Virology Medical Department
Virology is a science that takes the smallest acellular
biological virus on Earth as a research object.
As a class of biological
factors in the Earth’s biosphere, humans have also experienced the
understanding of the nature of viruses and their laws of life.
Over the past
century, virology has achieved tremendous development and has now become an
important branch of life science.
The content of virology research involves
various aspects of the virus's types, components, structure, metabolism, growth
and reproduction, genetics, evolution, distribution and other life activities,
as well as the relationship between the virus and other organisms and the
environment.
Virology research is closely related to life sciences and
biotechnology, because viruses are the simplest model for studying life
activities, providing a powerful tool for modern research on the structure and
function of biological macromolecules, efficient expression and regulation of
genomes, and the understanding of life phenomena in humans.
Many basic
information is provided during the process. At the same time, on the one hand,
the virus can cause various diseases of animals, plants and humans, such as
AIDS, which is still a huge threat to the survival of human beings.
On the
other hand, it can be used to eliminate pests and be used as the expression of
foreign genes, The carrier can be used by humans.
Virology involves a wide range
of fields such as medicine, veterinary medicine, environment, agriculture and
industry. It has developed into branch disciplines such as phage, medical
virology, veterinary virology, environmental virology, plant virology and
insect virology.
Virology has become a key subject that people must understand
in order to understand the nature of life, develop the national economy, and
ensure the health of humans and animals.
Medical virology is an important branch of virology, which
mainly studies the characteristics of viruses from a medical perspective,
sometimes called medical molecular virology.
The scope of medical virology
research includes the nature of viruses, transmission modes and pathogenic
mechanisms, as well as application-level drug and vaccine research. It is
closely related to molecular biology and pharmacology.
What is the History of Virology Department Discipline?
Viruses are a relatively primitive, life-like, non-cellular
organism capable of self-replication and strict intracellular parasitism. Its
meaning is that as people continue to deepen their understanding of the nature
of the virus, Daqi has experienced the following more important stages:
1.1892 When Ivanofsky discovered the tobacco mosaic virus
(TMV), he called it a filter pathogenic factor
What is Tobacco mosaic virus (TMV)?
2. In 2.1957, Lwoff.A was defined as a class of pathogens with
strict intracellular parasitic and potentially infectious characteristics due
to the elucidation of the virus replication cycle and the establishment of some
virus cell culture techniques, and pointed out that the virus has only one
nucleic acid.
3. In 1978, Luria and Darnell further confirmed that the
virus has only one kind of nucleic acid, which can reproduce in living cells to
produce progeny virus particles.
4. In 1971, Dienner discovered a viroid with only small
molecular RNA, viroid-like virusoid (satellite virus) was discovered in
Australia in 1981, and prion (virinoorprion) with a molecular weight of about
50KD was discovered by Prusiner in 1982.).
What are the Basic Features of Virology Department Discipline
1. Common ground:
Like all living things, viruses are a class of biological
entities that have characteristics of genes, replication and evolution, and
occupy special ecological status. In the extracellular environment
Virus-like
In the form of mature virions, it has a certain size, shape,
density, sedimentation coefficient and chemical composition, similar to
chemical macromolecules.
In the intracellular environment, it displays the
basic characteristics of born objects (genome replication leads to viruses
Reproduction, followed by a series of typical life activities such as genetics
and mutations).
2. Similarities and differences:
1) Does not have a cell structure so it is classified as
a non-cellular organism, and other organisms use cells as the basic building
block.
2) The virion has only one type of nucleic acid.
3) A special breeding method, because most organisms grow
through the orderly increase of the various components that make up the body,
and the breeding is completed through division.
Viruses complete the synthesis
of new virions through genome replication and expression.
Pseudovirus
4) Lack of complete enzyme system and energy synthesis system
All metabolic activities of organisms need to be carried out
under the action of enzymes, but also require a certain amount of energy
5) Absolute intracellular parasite: It does not show any vital characteristics outside the cell,
and all its life activities can only be performed within the host cell in which
it lives. This parasitic mode is different from that of some microorganisms
such as Leprosy, Rickettsia, and Chlamydia.
They are mainly derived from the
lack of exogenous nutrients or exogenous metabolic intermediates that need to
be provided by the host.
What is the Purpose of Virology?
First of all, viruses are pathogens. They can infect almost
all cell-type organisms and cause diseases. According to preliminary
statistics, 60 to 70% of human infections are caused by viral infections.
From
common colds, measles, mumps, polio, rabies, hepatitis and various
encephalitis, to epidemic hemorrhagic fever, senile dementia, AIDS, and many
cancers. Therefore, viral infectious diseases are still one of the main
diseases that seriously endanger the health of our people.
The reason is that
viral genes continue to mutate under the combined effects of natural selection
and crowd immunity, and the aging of the population and the acceleration of
urbanization.
Due to the interaction of factors, the prevalence of certain
viral infectious diseases not only failed to be effectively controlled, but
also became more rampant.
The prevalence of hepatitis A, B, C, AIDS, influenza
and various enterovirus diseases is still very serious.
In addition, many
results indicate that the virus is closely related to the occurrence of
malignant tumors and various chronic diseases.
At the same time, because the virus can also cause diseases
of poultry, livestock, wild animals, crops, forest fruits and many other
economic animals, plants and microorganisms, it will cause great harm to human
economic activities and the ecological environment.
The study of molecular
virology is to fully understand the characteristics of the virus, clarify the
relationship between the structure and function of the virus genes and products
at the molecular level, reveal the pathogenic mechanism and essence of the
virus, and ultimately control viral diseases.
Popularity provides important
theoretical and scientific evidence.
Ruan virus
Secondly, because certain viruses can also attack those harmful
to humans, they can become an important means of biological control. For
example, bacteriophage can be used to treat bacteria such as cholera, dysentery
and typhoid fever. Insect viruses can be used to control harmful insects.
Finally, because the virus is the simplest living unit with a
known structure, based on its relative simplicity outside the cell and the
outstanding characteristics of the complexity of the interaction between the
virus inside the cell and the host cell, it has become a molecular biology
research Ideal for replication, information transfer, mutation, and other
molecular biology problems.
The use of molecular biology methods for research
not only promotes the study of virology, but also in turn greatly promotes the
development of molecular biology.
In short, molecular virology is
interpenetrating and promoting each other in various natural sciences today.
Its research and development have an important role in elucidating more major
topics in modern biology, or in promoting the development of biotechnology.
Main Content
1) Structure and function of viral genome
Nucleic acid is divided into DNA and RNA, there are
single-stranded and double-stranded, linear and circular.
For single-stranded
RNA, there are also different polarities, divided into positive-strand RNA (+
RNA), negative-strand RNA (-RNA) and double-sense RNA (part of its genome is
positive.
The other part is negative). Positive strand RNA (+ RNA) with or
without hat structure, positive strand RNA (+ RNA) genome with no hat structure
5, with covalent binding protein at the end.
Polytailed poly (A) or no poly (A)
at the 3` end ).
Identify the nucleotide composition and sequence of the viral
genome.
Clarify the number, position and function of open reading frames (ORFs)
in the genome.
Understand the effects of repetitive sequence elements and
regulatory units in the viral genome on viral gene replication and expression.
Clarify viral structural genes, regulatory genes and their encoded products in
the viral replication cycle and their relationship with cellular genes and
their expressed products.
2) Regulation of viral gene expression
Gene expression involves two aspects: transcription and
translation.
Transcription
- Some viruses use RNA polymerase encoded by their own genome.
- Some are completely host-dependent RNA polymerases.
- Some regulatory proteins encoded by regulatory genes replace certain factors in the RNA polymerase of the host cell, thereby changing the transcription pathway of the host RNA polymerase.
- Use promoters or enhancers to bind or act on these regulatory elements through regulatory factors encoded by cells or viruses to affect the expression of viral genes.
- End cap and poly (A) tail with 3′ end, intron excision and mRNA splicing.
Translation
Because protein synthesis is completely dependent on the cell
translation system, the virus can take over and use the host's translation
system through its own specific mechanism, such as the inactivation of the
poliovirus 2A proteolytic cap binding protein complex (CBP), resulting in a cap
.
The structured host mRNA cannot be translated, and the virus mRNA lacking the
cap structure can be successfully translated using the host's translation
system.
3) Molecular mechanism of virus infection
The research includes not only the characteristics of the
virus absorption, invasion and release of the infection cycle, but also the
elucidation of the molecular mechanism of virus pathogenicity and host immune
effects.
Mainly involves the mutual recognition and function of the
viral adsorption protein and the host cell receptor protein.
The mechanism of
acute viral infection and persistent infection, especially in the process of
persistent infection, non-cell killing infection and viral escape host immune
recognition Mechanism of action.
4) Molecular mechanism of virus carcinogenesis
In addition to the genetic and other factors related to the
formation of human and animal tumors, some tumor viruses are also important
triggers for occurrence. There are three specific situations:
(1) Transforming Proteins Encoding
The transforming proteins encoded by the early genes of
certain DNA tumor viruses cause cell transformation and animal carcinogenesis.
The mechanism is that they bind to or act on the cell's tumor suppressor
protein P53 or Rb, causing P53 or Rb inactivation, resulting in unlimited
cells.
Uncontrolled proliferation and growth eventually induce cell
transformation and tumor formation.
(2) RNA Tumour
The genome of some RNA tumor viruses carries viral
oncogenes. The cell transformation and carcinogenesis of such RNA tumor viruses
are related to the expression activity of viral oncogenes.
(3) HTLV-1
Among RNA viruses, there are some viruses such as human T
lymphocytic leukemia virus type 1 (HTLV-1), which neither contain viral
oncogenes, nor protoviral DNA is preferentially inserted and integrated near
cell oncogenes.
However, the protein P40tax can be regulated by its own genome,
which can transactivate cell proliferation-related gene expression, thereby
causing unlimited cell proliferation and cancer.
5) Antiviral active substance
Interferon is the most clearly studied mechanism of action in
antiviral peptide substances.
It is present in almost all mammals. It is not
only resistant to viruses, but also has immunomodulatory and tumor suppressing
effects.
In 1979, the interferon gene was successfully cloned for the first
time. After years of development, it has become an important antiviral drug.
The cloned recombinant lymphokines such as IL-1, IL-2, and
tumor necrosis factor (TNF) also have strong antiviral activity.
The antiviral activity of antisense RNA has also received
widespread attention.
Mainly by hybridizing with its corresponding viral mRNA
or DNA, the function of viral mRNA encoding synthetic protein is blocked,
thereby destroying the replication cycle of the virus, and achieving the
purpose of anti-viral infection and prevention and treatment.
Ribozyme is an R capable of hydrolyzing target RNA.
NA molecules, after hybridizing with the target sequence
through ribozymes, can cleave specific phosphodiester bonds on RNA.
6) Genetic engineering vaccine of virus
Vaccines, especially viral vaccines, have become the most
important and effective means for people to prevent infectious diseases, and
are increasingly valued by the biomedical community.
Especially in the past 30
years, the rapid development of bioengineering technology and molecular biology
technology has greatly promoted the research and development of vaccines.
In
general, viruses with clear immune protection mechanisms and easy culture can
be produced using traditional processes.
While some immune protection
mechanisms are unclear and may produce immune pathological reactions, viruses
that have potential tumorigenic effects or are difficult to culture.
It is
difficult to produce vaccines by traditional methods, which can be solved by
genetic engineering methods.
The following issues need to be considered when
using this method:
- Use an appropriate expression system-whether the expression product is immunogenic
- Expression efficiency of the expression system
- Convenient purification of expression products
Development Process
The formation and development of virology generally
experienced the following four periods:
1. The discovery period of the virus
2.The chemical age of the virus
3. Cell-level research period
4. Period of molecular virology
1) When the virus was discovered?
Time Periods
1. Before the virus was discovered, people started dealing with the virus in a conscious or unconscious process.
It is observed that natural
phenomena caused by the existence of many viruses cannot be reasonably
explained due to the limitations of historical conditions and the level of
people's knowledge at the time.
Until 1892, when scientist D.Ivanofsky was
studying tobacco mosaic disease, he found that the causative factor of tobacco
mosaic disease can pass through bacterial filters, but he still believed that
the disease was caused by toxin-producing bacteria.
Later, in 1898, Dutch
scientist Beijerinck repeated D. Ivanofsky's experiment, proving that tobacco
mosaic disease was caused by a filtering pathogen. In the same year, German
scientists Loeffler and Frosch discovered that FMD pathogens are also
filterable.
More than 10 years later, more than 10 pathogenic viruses of
infectious diseases (chicken plague virus, yellow fever virus, rabies virus,
etc.), as well as phage and various plant viruses later discovered.
2. The chemical period of the virus
Since 1935, Stanley in the United States purified and
crystallized tobacco mosaic virus for the first time, which led to a major
breakthrough in the understanding of the chemical nature of the virus and
opened a broad path for further research on the virus.
Then, Bawden et al.
Further revealed that the chemical nature of tobacco mosaic virus is not pure
protein, but nuclear protein.
On this basis, the German Kausche first observed
the rod-shaped appearance of tobacco mosaic virus in 1940 using electron
microscopy.
The application of electron microscopy technology has promoted its
development in many ways. The morphogenetic research within provides an
effective means.
In short, although virology has made great progress by this
period, it has not yet formed an independent discipline. Its understanding
of the nature of virus chemistry is relatively superficial.
There is still a
lot of controversy about the concept of virus.
3) The cellular level of the virus
During this period, virology has developed greatly both in
theory and in practice, and has a unified and clear concept for viruses.
Gradually formed as an independent discipline, but also laid the foundation for
the establishment of molecular virology.
- By studying the interaction between bacteriophage and infected bacteria, clarify the replication cycle of bacteriophage.
- Reveal the principle of lysogenic bacteriophage induction.
- Prove the infectivity of bacteriophage DNA.
- Discover the transduction phenomenon of lysogenic bacteriophage and bacteriophage, tissue culture technology.
The establishment of
the technology has greatly expanded the research scope of virology and promoted
people's understanding of the nature of the virus.
At present, the technology
has been widely used in the isolation of unknown infectious agents, diagnosis
of viral diseases, vaccine production, and basic research on virus infection
and replication.
4) Period of molecular virology
Since the establishment of the double-helix structure theory of
DNA in 1953, the widespread application of new technologies and methods has
made virological research into the development of molecular virology.
The 1950s
and 1960s were the foundational era for molecular biology, and bacteriophages
and plant viruses have made great contributions to this. Therefore, molecular
virology emerged in the course of the development of molecular biology.
At this stage, people are mainly committed to:
- The structure, function, and expression regulation mechanism of the viral genome.
- The structure, function and synthesis of viral proteins.
- The mechanisms of infection, reproduction and pathogenicity of various viruses.
- A deeper understanding of the relationship between the virus and its host Interactions, especially the relationship between tumor viruses and tumorigenesis.
- Continuous exploration of new technologies and methods for the diagnosis, prevention and treatment of viral diseases.
- Understanding of the pathogenic nature of suspected viral diseases for which the etiology has not yet been confirmed. The fruits have been fruitful, specifically in the following aspects.
- In 1955, Frannkel-Conrat completed the in vitro disassembly and reconstruction experiments of tobacco mosaic virus (TMV) nucleic acid and protein subunits.
- 1960 Anderer clarified the amino acid sequence of TMV capsid protein subunits
In 1962, Casfar clarified the icosahedral structure of
certain viruses, and clarified the structure of the nucleocapsid icosahedron.
What is the Retroviral replication process?
In 1962, Nathans successfully translated phage RNA in vitro.
In 1965, Spiegelman successfully replicated bacteriophage RNA
in vitro, thus breaking the traditional concept that viruses must proliferate
in vivo.
These work have played an important role in elucidating the
reproduction mechanism of DNA viruses and RNA viruses in the future.
Baltimore and Temin discovered the viral reverse
transcriptase separately in 1970, which is an important supplement and
development to the central law proposed in 1958.
In 1976, Dueberg discovered that Rous sarcoma virus contains
the oncogene v-src, and in the DNA of normal chickens and other vertebrates and
invertebrates, a homologous sequence of oncogene v-src was also found,
speculating that the virus oncogene may be Normal genes from cells.
In 1977, Sanger completed the complete sequencing of the
phage φX174-DNA.
Taniguchi successfully expressed the human interferon gene in
1979, which was a major breakthrough in genetic engineering.
In 1982, Moss and Paoletti used vaccinia virus as a vector to
express foreign genes with success.
In 1983, Montagnier and Gallo isolated human retroviruses
(HIV) related to AIDS.
In 1991N, Han et al. Introduced the antisense expression
sequence of Moloney mouse leukemia virus into mouse fertilized eggs, thereby
cultivating transgenic mice that were resistant to the virus.
The identification of the three-dimensional structure of HIV
aspartyl protease in 1995 led to the emergence of inhibitors targeting the
active site of viral protease.
In 1996, the Chinese-American He Dayi and other cocktail
drugs formulated with reverse transcriptase inhibitors and protease inhibitors
successfully resisted HIV infection.
Author's Bio
 |
| Dr. Shawna Reason |
Education: MBBS, MD
Occupation: Medical Doctor / Virologist
Specialization: Medical Science, Micro Biology / Virology, Natural Treatment
Experience: 15 Years as a Medical Practitioner
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