structure of HIV virus

 In 2012, the estimated adult prevalence in the general population  was 0.27 percent and the total number of people living with HIV/AIDS (PLHA) people living with HIV/AIDS was estimated to be 20.89 lakh . Children less than 15 years of age accounted for percent (1.45 lakh). India is estimated to have around 1.16 lakh annual new HIV infections among adults and around 14,500 new HIV infections among children in 2011.            

Virus: Classification, Structure and Genome

HIV is a Lentivirus that infects and destroys cells in the immune system. Lentiviruses are in turn
part of a larger group of viruses known as retroviruses. The name 'lentivirus' means 'slow virus.'
They are thus named because they take a long time, often many years, to produce adverse
effects in the body. There are two HIV types, HIV-1 and HIV-2. HIV-1 is the most prevalent type
throughout the world. HIV-2 has limited geographic distribution. HIV-1 is closely related to
Simian Immunodeficiency Virus (SIV), prevalent in populations of wild chimpanzees in West-
Central Africa.

HIV is an enveloped virus as shown in figure. The virus envelope is composed of two Phospholipid layers derived from the host cell membrane. The envelope also contains the trimers of an envelope coated protein, glycoprotein (gp) 160. Gp160 is composed of two subunits, gp120 and gp41. While gp120 has external protein and contains sites that bind CD4 cells and co-receptors on the surface of human CD4 T cells, gp41 is membrane bound protein. Inside the viral envelope there is a layer called the matrix, which is made from the protein p17.
The viral core (or capsid) is usually bullet-shaped and is made up of protein p24. Inside the core
are three enzymes required for HIV replication: Reverse Transcriptase (RT), integrase and
protease, they are the 3 important factor of HIV 's life they are found in nucleocapsid,  Also held within the core is HIV genetic material which consists of two positive strands
of single stranded Ribonucleic Acid (RNA).

We know that T helper cells is the main target for HIV, other cells can become infected as well., they include MONOCYTES , MACROPHAGES and  etc, they can hold them together like as a friend , and they don't get killed , they acts like a hypnotized person , some of them T helper cells acts like a reservoirs of the HIV virus

HIV genome is approximately 9.1 Kb in size ans carries 9 gene and a long terminal repeat region at either ends of genome. There are 3 structural genes are present there , these genes are known as
1.  ENVELOP (env) helps for coding for envelop of HIV
2. GROUP SPECIFIC ANTIGEN (gag)  helps in coding for caspid and matrix
3. DNA POLYMARESE (pol) helps in coding for integrase, protease, reverse transcriptase enzyme.
and there is a other  gene whose name is TRANS ACTIVATOR OF TRANSCRIPTION (tat) helps for virus replication

What is HIV ?

HIV is transmitted from one infected person to another through penetrative sexual acts, both heterosexual and homosexual, through a contaminated blood transfusion or sharing of needles and syringes , and from mother to child in pregnancy or in breast feeding, Initially they are called HIGH RISK GROUPS , the population most vulnerable to HIV are compromised of sex worker(male and female), men having sex with men, Transgender, and injecting drug user.

By the end of 2013, an estimated 35 million (33.1 million - 37.2 million) people were infected with HIV globally. The average adult prevalence was 0.8 percent. Of the total number of infections 3.2 million occurred in children (individuals less than 15 years of age). Of the total number, 2.1 million were new infections – illustrating an overall decline in the number of new infections. Over the decade, thirty-three countries reported a decline in the incidence of HIV;two thirds, of the remaining countries, showed a stable incidence rate; and the remaining third showed an increasing incidence rate. Over the past five years, there has been a 19 percent decline in AIDS related deaths

HIV infects vital cells in the human immune system such as Helper T cells (specifically CD4⁺ T cells), macrophages , and dendritic cells. HIV infection leads to low levels of CD4+ T cells through a number of mechanisms, including pyroptosis of abortively infected T cells, apoptosis of uninfected by standers cells, direct viral killing of infected cells, and killing of infected CD4⁺ T cells by CD8 cytotoxic lymphocytes  that recognize infected cells. When CD4⁺ T cell numbers decline below a critical level, cell mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.

What is CD4 cells ?

CD4+ T helper cells  are the white blood cells that are an essential part of the human immune system. They are often referred to as CD4 cells, T-helper cells or T4 cells. They are called helper cells because one of their main roles is to send signals to other types of immune cells, including CD8 killer cells, which then destroy the infectious particle. If CD4 cells become depleted, for example in untreated HIV infection, or following immune suppression prior to a transplant, the body is left exposed  to a wide range of infections that it would otherwise have been able to fight like Tuberculosis, Pneumonia, common cold etc. 

The full form of CD4 cells are clusters of differentiation 4 is a Glycoprotein  found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells. Just like the paint on wall , or at any surface.

Unlike some other viruses, the human body can’t get rid of HIV completely. So once you have HIV, you have it for life. The CD4 cell count of a person who does not have HIV can be anything between 500 and 1500 People living with HIV who have a CD4 count over 500 are usually in pretty good health.People living with HIV who have a CD4 cell count below 200 are at significant risk of developing serious illnesses. While HIV treatment is recommended for all people living with HIV, it is especially important for people with low CD4 counts.If you have HIV and do not take HIV treatment, your CD4 count will fall over time. The lower the CD4 cell count, the greater the damage to the immune system and the greater the risk of illness

Without treatment, people who are diagnosed with AIDS typically survive about 3 years. Once someone has a dangerous opportunistic illness, life expectancy without treatment falls to about 1 year. People with AIDS need medical treatment to prevent death.