AIDS stand for Acquired Immune Deficiency Syndrome. They are caused by HIV – Human Immunodeficiency Virus which belong to the family RETROVIRUSES.

Retroviruses are RNA viruses and the virion RNA is linear and 7 to 10kb long. The positive sense single stranded RNA genome is packaged into a protein capsid, surrounded by a lipid envelope.

Retrovirus particles also contain the enzyme reverse transcriptase (or RTase), which causes synthesis of a complementary DNA molecule (cDNA) in the host cell using virus RNA as a template. This means that the DNA in the cells contains the virus and the genome does not serve as an mRNA. The virus thereafter replicates as part of the host cell's DNA. mRNA would be then translated into viral proteins that are used to make the virus envelope. New viral particles are assembled and they bud from the plasma membrane, and are released.

This lipid envelope contains polypeptide chains including receptor binding proteins which link to the membrane receptors (complex protein structures) of the host cell, initiating the process of infection. A receptor is often compared to a lock into which a specific key or "ligand" will fit. There are at least two receptors on T-lymphocytes to which the human immunodeficiency virus (HIV) sticks. The primary receptor, called "CD4" is the main molecule responsible for HIV virus to bind. Cells that do not contain “CD4” do not attract HIV.

All retroviruses contain the gag, pol and the env genes.
Gag – Group specific antigen codes for core and structural proteins of the virus.
Pol – Polymerase codes for reverse transcriptase, protease and integrase. They do not contribute to the structure.
Env – Envelope codes for the retroviral coat proteins.

AIDS is transmitted through various ways such as
· Having sex with an infected person
· Sharing a needle (shooting drugs) with someone who is infected
· Blood and blood products
· Child being born when mother is infected
· Drinking the breast milk from an infected mother

Acute stage
Primary infection of HIV may cause flu-like symptoms, fever, skin rash, swollen glands and swollen lymph nodes. These symptoms do not indicate the development of AIDS, and they usually disappear within a few days or weeks.

Asymptomatic stage
People living with HIV may feel and look completely well but their immune systems would nevertheless be damaged. The HIV still replicates within and it will still transmit even if the infected person is healthy.

Symptomatic stage
Over time the immune system becomes severely damaged by HIV. The lymph nodes and tissues become damaged or 'burnt out' because of the years of activity. HIV mutates and becomes more pathogenic, in other words stronger and more varied. It leads to more T helper cell and CD4 T lymphocytes destruction. The body fails to keep up with replacing the T helper cells that are lost. As the immune system deteriorates, the symptoms worsen.
A drug has not been found for AIDS therefore, it is very difficult to treat this disease. Those people who are infected with AIDS should boost their immune system by the intake of vitamins, minerals and anti-oxidants.

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