LIFE CIENCES AND MEDICINE.

Viruses are important to the study of cell and molecular biology as they are simple systems that can be used to investigate or manipulate the functions of the cells. For example, viruses have been useful in studying the basic mechanisms of molecular genetics, such as DNA replication, transcription, RNA processing, gene translation, transport of proteins and immunology.

ANTIVIRAL DRUGS

Over the past twenty years, the development of antiviral drugs has increased rapidly, fueled by the AIDS epidemic. Antiviral drugs are often 'nucleoside analogues (nucleoside false, the building blocks of nucleic acids) that the virus entering their genomes during replication. The life cycle of the virus then stops because the new DNA chains are synthesized defective. This is because the lack of similar hydroxyl groups together with the phosphorus atoms are strong links "backbone" of the DNA molecule. This is called interruption in the supply chain ADN.Ejemplos of nucleoside analogues are acyclovir to treat herpes virus infections and lamivudine for HIV and hepatitis B. Acyclovir is one of the oldest and antiviral drugs often prescribed.

VACCINATIONS

Vaccination is a cheap and effective way to prevent infections caused by viruses. The vaccines have been used to prevent viral diseases long before the discovery of the virus. Their use has led to a dramatic decrease in morbidity (illness) and mortality (death) associated with viral infections such as polio, measles, mumps and rubella. Smallpox has been eradicated.It is now available vaccines to prevent viral infections over thirteen in humans, and others are used to prevent viral infections in animals. The vaccines may consist of live attenuated virus or killed, or only the viral proteins (antigens).The live vaccines contain weakened forms of the virus that causes the disease. Live vaccines can be dangerous when administered to immunocompromised persons, because these people even in the weakened virus can cause illness original. However, the vaccine against yellow fever virus, obtained from an attenuated strain called 17D is arguably one of the safest and most effective vaccines manufactured. Biotechnology and genetic engineering techniques are used to produce vaccines subunits. These vaccines use only the capsid protein of the virus. The vaccine for hepatitis B is an example of such a vaccine.subunit vaccines are safe for immunocompromised patients because they can not cause disease.

Host immune response

The first line of defense against the virus body is the innate immune system. This includes the cells and other mechanisms that defend the body from infection in a non-specific. This means that the innate system cells recognize and respond to pathogens in a generic way, but unlike the adaptive immune system does not confer long-term protection or immunity.
RNA interference is an important innate defense against viruses. Many viruses have a replication strategy that involves bicatenario RNA (dsRNA). When these viruses infect a cell and release its RNA molecule or molecules, just a complex protein called dicer binds to RNA and cut into smaller pieces. A biochemical pathway called RISC complex is activated and degrades the viral mRNA. Rotaviruses desnudándose not avoid completely the mechanism inside the cell. The genomic dsRNA remains protected inside the core of the virion and released new mRNA produced through the pores of the capsid.
When the adaptive immune system of a vertebrate is a virus, producing antibodies that bind to the virus and make it non-infectious, which is known as humoral immunity. Two types of antibodies are important. The first is called IgM, is highly effective in neutralizing the virus, but is only produced by cells of the immune system for a few weeks. The second, called IgG, is indefinitely. The presence of IgM in the blood of the host is used to identify an acute infection, whereas IgG indicates an infection in the past.The two types of antibodies test was carried out when the evidence of immunity.
A second line of defense of vertebrates against viruses is called cellular immunity and consists of immune cells known as T lymphocytes The body's cells constantly display short fragments of proteins in the cell surface. If a T cell recognizes a cell suspected of being a viral fragment, and then destroys the cell is a proliferation of T cells specific for the virus. Macrophages are cells specialized in antigen presentation. The production of interferon is an important mechanism involved in the defense.
Not all virus infections in this way produce a protective immune response. HIV evades the immune system by changing the sequence of amino acids of the protein on the virion surface. These persistent virus escape control by the abduction and blocking antigen presentation, resistance to cytokines, to the avoidance of lifocitos T, inactivation of apoptosis, and antigenic shift. Other viruses, called "virus neurotrophic "is propagagan in neural system, where the immune system may be unable to reach them.

Prevention and treatment.

Because viruses use the machinery of a host cell to reproduce and reside within them, are difficult to remove without killing the host cell. The most effective medical approaches to combat viral diseases are the vaccines that provide resistance to infection, and antiviral drugs to treat the symptoms of viral infections.

VIRAL INFECTION DISEASES

AIDS

Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century. HIV is now a pandemic, with an estimated 38.6 million people currently infected by the disease around the world . The Joint United Nations Program on HIV / AIDS (UNAIDS) and World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognized the June 5 1981, becoming one of the most destructive epidemics in history.

Ebola

Several highly lethal virus pathogens are members of the family Filoviridae. These are filamentous viruses that cause viral haemorrhagic fever, including Ebola virus and Marburg virus. The Marburg virus attracted the attention of the press in April 2005 by an outbreak in Angola. The outbreak began in October 2004 and continued in 2005 and was the worst epidemic of any kind of viral hemorrhagic fever.

VIRUSES AND DISEASES

Examples of common human diseases caused by viruses include the common cold, flu, chicken pox, polio, measles, mumps and rubella. Among the major diseases are caused by the Ebola virus, AIDS, avian flu and SARS. Other diseases are polio, mumps, rubella, hepatitis B, hepatitis C, yellow fever, dengue fever, smallpox (eradicated), and so on. Some diseases are under investigation to determine if they have a virus as the causative agent, for example, human herpesvirus-6 (HHV6) could be related to neurological diseases such as multiple sclerosis and chronic fatigue syndrome. It is also investigating whether the Borna virus, which causes neurological disease in horses, could be responsible for psychiatric illness in humans.

The relative ability of the virus to cause disease is described in terms of virulence. The viruses cause disease in the host through different mechanisms that rely heavily on the kind of virus. The mechanisms at the cellular level include mainly the analysis and subsequent cell death. In pluricellular agencies, if enough cells die, the whole body will start to be affected. The virus may also exist within a relatively ineffective body. This is called latent and is a feature of herpesvirus including the herpes simplex virus, which causes cold sores, the Epstein-Barr virus, which causes glandular fever, and varicella-zoster virus, which causes chickenpox. The chickenpox virus, after the disease returns in later life as shingles.

Some viruses can cause chronic infections, in which the virus is still replicating in the body, despite the host's defense mechanisms.This is a common infection of hepatitis B and hepatitis C. People chronically infected with hepatitis B virus serve as reservoirs of the virus (are carriers). When there is a high proportion of carriers in a population, it is said that the disease is endemic.