Introduction of AIDS
In 1981, a group of homosexual youths was found in America who were addicted to heroin and other narcotics. Members of this group started getting fatal diseases like pneumonia and skin cancer (Kaposi's sarcoma). On discovering the reason for this, it was found that these youths had lost the necessary immunity against these deadly diseases. This condition is named as Acquired Immunodeficiency Syndrome—AIDS.
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Soon, in 1983, Luc Montagnier, a scientist at the Pasteur Institute in Paris, and In 1984, research by Robert Gallo, a scientist at the US National Institute of Health (NIH), showed that infection with an unknown retrovirus class virus had destroyed immunity in these people.
full form of HIV
In May 1986, the International Committee on Virus Nomenclature ICVN named this virus as Human Immunodeficiency Virus - HIV.
Structure of HIV
HIV is a spherical, enveloped retrovirus of approximately 0.1 to 0.14 µm (100 to 140 nm) in diameter and complex in structure. Its structure is complex. It consists of three main parts -
1. Central part or core
2. capsid in the middle
3. outermost lipoprotein envelope
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| structure of AIDS virus - HIV |
➤ Its central part is conical. In which there is the genome of the Virus and some proteins associated with it.
➤ Its genome consists of two identical ribonucleotide chains of single-stranded RNA (ssRNA).
➤ The proteins associated with these chains mainly contain molecules of reverse transcriptase, integrase, protease, and ribonuclease enzymes. Among these, the reverse transcriptase enzyme is the most important.
➤ The capsid surrounds the central core in the form of a rigid, protective shell made of protein molecules called the nucleocapsid.
Its inner conical part around the central core is shelf-like and outside it is an icosahedral shell made of 20 plates. While the protein molecules in the shelf-like portion are of p24, the protein molecules in the icosahedral shell are of p17.
Its inner conical part around the central core is shelf-like and outside it is an icosahedral shell made of 20 plates. While the protein molecules in the shelf-like portion are of p24, the protein molecules in the icosahedral shell are of p17.
➤ Each part has a definite symmetrical arrangement of a definite number of protein molecules. Some protein molecules, denoted p7 and p9, remain attached to RNA sources in the central core.
The outer lipoprotein shell of HIV is in the form of a phospholipid bilayer derived from the plasma membrane of the host cell. It contains molecules of many types of proteins of the host cell and of the virus itself.
➤ There are two types of glycoproteins in the proteins of the virus, which have been given the codes of gp41 and gp120. Together the molecules of these two Glycoproteins form 72 pedunculated spike-like knobs that emerge on the surface of the cover, which work to connect the virus particle to the host cell. These knobs are also called peplomers. The stalk of each knob is made of gp41 and the knob itself is made of gp120.
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Pathogenesis of HIV (through the diagram)
➤ HIV attacks only those cells whose cell membrane has molecules of a special type of receptor protein raised on the surface of the cell. This protein was given the code name of CD4 protein.
➤ Although CD4 protein molecules are present in the cytoplasm of many types of cells, their number is very high in the cytoplasm of T4 lymphocytes.
Hence T4 lymphocytes are the major host or target cells of HIV. HIV does its proliferation by entering T4 lymphocytes and weakens the body's immunity by destroying more and more T4 lymphocytes. This whole process can be described in brief by dividing it into the following steps -
1. Adsorption - Upon contact with the T4 lymphocyte, the interaction between the glycoproteins (gp120) of the knobs of the outer lipoprotein shell of HIV and the CD4 proteins of the Cell membrane of T4 lymphocytes results in the binding of HIV to the surface of T4 lymphocytes.
2. Entrance - As a result of the reaction of gp-41 molecules on the knobs of the lipoprotein shell of HIV, the lipoprotein shell binds to the Cell membrane of the host lymphocyte and becomes a part of it. Thus the nucleocapsid of HIV enters the lymphocyte's cytosol by endocytosis.
3. Uncoating - The proteins of the nucleocapsid of HIV undergo hydrolysis in the cytoplasm of the host lymphocyte cell. Hence, the RNA sequences of the HIV genome and the enzymes associated with them are exposed and released into the cytoplasm.
4. and 5. Transcription of RNA into DNA - Molecules of the reverse transcriptase enzyme bound to the RNA strands of HIV in the cytoplasm first catalyze the transcription of these strands into a single single-stranded DNA strand and then catalyze the duplication of this single-stranded DNA strand into a double-stranded DNA strand.
6. Integration of dsDNA of HIV into host DNA - The dsDNA strand formed by reverse transcription of HIV's RNA enters the nucleus of the host lymphocyte and, with the help of integrase enzymes, integrates into the lymphocyte's DNA. This is now called provirus.
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7. and 8. Synthesis of genome and nucleocapsid proteins of HIV - Repeated transcription of DNA derived from the HIV genome results in multiple copies of the two types of RNA molecules being passed from the nucleus of the host lymphocyte into the cytoplasm. One type of RNA molecule combines in pairs to make copies of the HIV genome. The second type of RNA molecule is messenger RNA (mRNA) whose translation leads to the synthesis of proteins and enzymes of the HIV capsid on the ribosomes of the lymphocyte.
9. Combination - The HIV genome and proteins are assembled into several separate nucleocapsids in the cytoplasm of the host lymphocyte.
10. Liberation - Now the nucleocapsid of HIV comes close to the cell membrane of the host lymphocyte and is released into the blood by budding i.e. exocytosis.
➤ HIV that is released into the blood repeatedly after being formed in infected T4 lymphocytes continues to infect new T4 lymphocytes. Each infected T4 lymphocyte eventually weakens and disintegrates. Thus due to the widespread destruction of T4 lymphocytes, the body's immunity is gradually reduced.
➤ Gradually, HIV starts being present in the saliva, tears, urine, sweat, cerebrospinal fluid of the Central Nervous System (CNS), semen of men, and vaginal discharge and milk of women. Scientists have discovered that the AIDS virus found in India belongs to the C subfamily (HIV-C). This virus is more deadly than HIV in other countries because it damages our body's immune system at a higher rate.
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Clinical Symptoms
➤ Primary infection - The entry of HIV into a person's body is called primary infection. No effect of infection is visible in the infected person for 2-4 weeks, but after that 70 to 80% of the people show some symptoms for some time such as mild fever, head and body pain, boils, nervousness, etc.
➤ Incubation period - The above symptoms of primary infection disappear quickly and no symptoms appear for 3 to 12 years in different individuals. Meanwhile, HIV continues to proliferate in T4 lymphocytes. HIV is transmitted from the blood to other body fluids above. Therefore, such infected persons work to spread HIV infection to other persons.
➤ Full-blown AIDS - Due to the destruction of more and more T4 lymphocytes in the incubation period of 3 to 12 years, when the immunity of the infected person's body gradually becomes very weak, such a person becomes a victim of full-blown AIDS disease. Many types of disease symptoms are clearly visible in this.
These symptoms include-
- Pneumonia
- Blindness
- Dementia
- Rashes on the face
- Skin cancer
- Persistent fever and diarrhea
- Loss of appetite
- Weakness
- Tiredness
- Body aches
- Dry cough
- Sores in the mouth and intestines,
- Warts on the genitals and anus.
The body becomes so weak that the disease is often called slim disease. Ultimately, the person's immune system becomes so inefficient that the patient dies due to many infectious diseases like malaria, Tuberculosis (TB), etc.
Transmission of HIV
As is clear from the above description, HIV is present in the blood, semen, vaginal discharge, and other body fluids of infected persons. The virus spreads from infected individuals to healthy individuals through these fluids. Such transmission is called horizontal transmission. It has the following three main methods-
➤ Sexual intercourse - Sexual intercourse also plays an important role in the effort to get rid of the tensions of the complex social life. Sexual intercourse can be mainly of three types - vaginal sex, anal sex, and oral sex. Most (about 80%) transmission of HIV occurs through sexual contact. In this too, most of the transmission occurs through sexual contact, because HIV is found in large numbers in the semen of infected men and vaginal fluid of infected women.
Therefore, it is clear that maximum transmission of HIV is done by commercial sex workers i.e. prostitutes and men who have sex with them.
Some transmission of HIV also occurs among homosexuals through anal sex. When the mucous membrane of the anus is broken during anal sex, the HIV present in the semen reaches directly into the blood.
➤ Medical reason - In medical reasons, the biggest reason for the transmission of HIV is the transfusion of the blood of an infected person into the body of a healthy person in blood transfusion. Similarly, HIV is also transmitted by doctors using unsterilized injection needles and organ transplantation from infected individuals to healthy individuals.
➤ Drug addiction - Many drug addicts take these substances through intravenous injections. In this, these people often use the same shared injection needle, due to which HIV keeps going from infected persons to healthy persons.
In addition to the above methods of transmission of HIV, HIV can be passed from an infected mother to the fetus, or the infant can be infected after birth through breast milk. Such infection is called vertical transmission.
HIV is not transmitted through normal social interactions such as dry kissing, hugging, shaking hands, coughing, sneezing, eating or sleeping together, or through insect bites. Thus AIDS is an infectious disease, but it is not a contagious disease like cold, influenza, polio, measles, etc. That's why other people should treat people infected with HIV with empathy.
Epidemiology of AIDS
Although it has been only about 25 years since the disease of AIDS started, it has become a worldwide (pandemic) spreading in all the countries of the world. According to World Health Organization (WHO) statistics, about 4 crore people in the world have been infected with HIV.
➤ According to the latest statistics, about 10 to 20 lakh people get infected with HIV every year in the world and millions of people die due to AIDS disease.
➤ The number of youth and women in the age group of 16 to 24 years is the highest among the people who are vulnerable to HIV.
HIV infection in India was first detected in 1986 by Dr. Suneti Solomon in some prostitutes of Madras. Since then its infection has been detected in about 5 million Indians.
- Only in Uttar Pradesh, about 70 thousand people have been found infected with HIV. This disease is now spreading very fast in our country.
- Prostitutes have contributed the most to its spread. States like Andhra Pradesh, Manipur, Tamil Nadu, Karnataka, Maharashtra, Nagaland, etc. are getting more and more affected.
- According to the statistics of the National AIDS Control Organization (NACO), which was established in 1987 for the prevention of AIDS, now our country is second in the world in HIV infection.
If the transmission of AIDS continues to increase in this way, then it will have a bad effect on the military power and economy of our country.
Prevention and Prophylaxis of AIDS
Despite extensive research, scientists have not yet been able to make a vaccine for the prevention of AIDS to generate immunity in the body. Efforts are also being made to prevent it through gene technology. Presently, the method of its prevention is limited to the precautions taken by humans in their social activities. For example -
- Complete cleanliness and caution should be taken in sexual intercourse and condoms should be used.
- Blood for transfusion and organs used for transplant should be thoroughly tested.
- Complete cleanliness of injection needles should be taken care of.
For the prevention of the disease, WHO has declared the first day of December every year as World AIDS Day to attract the attention of the general public towards these things. At present, education should be given at the social level to make citizens aware of AIDS disease. Educationists think that the subject related to this disease should be included in the curriculum at the secondary level and beyond.
Diagnosis and Treatment of AIDS
➤ HIV infection can be identified through an electron microscope by the presence of the virus in fluids such as semen, vaginal discharge, saliva, milk, blood, etc., but scientists have invented simple, chemical testing methods.
➤ Remember, in infected T4 lymphocytes, under the control of certain HIV genes, antigenic proteins are synthesized and released into the bloodstream, which are then neutralized by the body's immune system by producing appropriate antibodies.
➤ The absence of HIV infection is determined by detecting the presence of these antibody proteins in the blood by serological test. Scientists have made an ELISA kit (Enzyme-linked Immunosorbent Assay Kit) to test the serum of these antibodies. The most important role in this test is played by the alkaline phosphatase enzyme.
➤ The most unfortunate thing is that till now no effective treatment method has been developed for AIDS. That's why, many people around the world continue to die due to this disease.
About thirty drugs have been estimated to have the potential to treat AIDS. These include drugs such as zidovudine, namely azidothymidine (AZT), didanosine, stavudine, delavirdine, etc. These drugs cannot cure the disease, but by inactivating the reverse transcriptase enzyme of HIV, they stop the multiplication of HIV, so that the disease does not progress.
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