AIDS - How HIV Infects T-helper Cells?

AIDS virus is found in the blood of the infected person. The virus is even found in genital secretions of every infected person. This virus spreads to an uninfected person who happens to come in sexual contact where in the virus from the genital secretions of the infected person enters the tissues of the healthy person (which are at the lining of the anal area, vagina, mouth etc.), the virus enters in the body of an uninfected person if the blood (or genital secretion) of the infected person is touched by the uninfected person who has cut/punctured skin on the area that comes in contact with it or if an uninfected person uses a syringe/needle (used for any purpose such as tattooing, drugs etc.) that is used by an infected person. The virus also spreads from infected mother to newborn baby during pregnancy and even breast feeding from the infected mother can cause AIDS to her baby.

Now let us see effects that a person might experience after getting infected with HIV virus. The person who gets infected by HIV virus (knowingly or unknowingly) does not develop positive HIV antibodies immediately; in fact it takes between 2 to 4 months to turn the HIV antibodies into positive (which can be confirmed by tests such as ELISA and western blot). The starting period of infection of HIV virus is also called primary stage of HIV infection. During this period, the infected person (although this is not what all the infected patients experience, but these are general symptoms) experience a flu-like situation, the person might experience fever for several weeks. Soared throats/mouth, frequent fever, muscles and join pain, swollen lymph nodes in the neck etc. are some of the common symptoms experienced by most of the AIDS patients during their primary stage of infection. In most of the cases it is found that the above enlisted symptoms vanish as soon as the HIV virus turns positive. In this phase, the virus starts spreading (multiplying) inside the body of the infected person and as he has no symptoms of AIDS, only a test can tell whether the person is infected with HIV.

As given above, after the patient passes the primary stage of infection, the virus starts multiplying inside the host's body. The viral reproduction depends on many factors such as physical condition, immune system etc. of the host. Every day more than some millions (or sometimes billions, the number is not same for everyone and everyday) HIV viruses are produced inside the patient's body. AIDS is a very slow progressing disease, the procedure of HIV virus multiplying generally takes about 8 to 10 years. Once the HIV virus is reproduced up to a certain extent, a situation called AIDS develops in patient.

Now let us see, how the virus works inside the patient's body. In biological words, every living cell has its set of functions defined, such as CD4 cells, which has a function to fight with diseases and provide make our immune system stronger. We can say that every cell is programmed to do some activity. The HIV virus; reprograms the cells of immune system and converts them in cells that produces more HIV viruses (as HIV viruses cannot reproduce more HIV viruses or cannot replicate itself just like a living cell can do). This process continues until human immune system becomes so weak that it cannot fight even a simple disease that did not need any special dose of medicine.

HIV virus attacks CD4+T cell, which is also known as T-helper cell of Immune System. HIV virus is called retroviral, because it takes help of enzyme called Reverse Transcriptase, to convert RNA strands into DNA. As a first step of infecting a healthy T-helper cell, HIV virus gets itself attached to the CD4 protein of the T-helper cell wall with the help of its gp120 Envelop protein. This works as a gate opener, the cell wall of the T-helper cell allows the viral core of the HIV virus enters into T-helper cell after gp120 protein docks itself to the CD4 protein. Further, the reverse transcriptase inside the HIV virus core, copies the virus's RNA into DNA. This newly generated DNA is carried to the T-helper cell's nucleus by an enzyme called viral integrase, where the virus's DNA binds itself with the T-helper cell's DNA. This mutated DNA then creates messenger RNA (mRNA), and in this process it uses the enzymes available in T-helper cell. The messenger RNA is just like blue-print of instruction which tell how to create new viral proteins.

This mRNA is carried out of the nucleus of the T-cell by the cell's own enzymes. Now the virus inside the cell uses cell's proteins to make more long chains of viral proteins and enzymes. Here the infected T-helper cell comes completely under control of the HIV virus and works as new virus producing factory. The newly created viral proteins, RNA and enzymes gather at the edge of the T-helper cell ready to get into a protective sheathe and infect another healthy T-helper cell. An enzyme which is called protease cuts the polypeptides into viral proteins. The newly created HIV virus particles then leave the infected T-helper cell and get their own protective sheathe (which again is made up of membrane of the infected T-helper cell) and head towards the other Immune System cells. This process is also called budding and about thousands of T-helper cells are infected slowly until the CD4 cell count reduces to a very low level. At certain level when the number of T-helper cells per millimeter in blood goes below a particular number, the person is considered to have developed AIDS.