HIV And Transmission
Human immunodeficiency virus or commonly known as HIV is a lentvirus that falls into category of retroviruses. When a person gets exposed to HIV the virus will cause progressive failure of immune system and in the final stages AIDS. HIV infects T helper cells. The reduction of CD4+ T cells is achieved in three different ways, by viral killing of the cells they inflict, second way is by increasing aptosis and the third by using CD8 cytotoxic lymphocytes that recognize the infected cells and destroy them. If the number of CD4+ T cells drops too low the cell mediated immunity will be lost and opportunistic infections will be able to infect the body.
There are two different types of HIV that have been identified, the first one is HIV-1 it is highly virulent and infectious and the second one HIV-2 has lower infectivity and virulence. They are both believed to originate from non human primates in West-central Africa and they were transmitted to humans trough a process known as zoonosis in the first half of 20th century. HIV-1 is believed to originate from southern Cameroon after the simian immunodeficiency virus that effects chimpanzees evolved, and the closest relative of HIV-2 is a virus that affected sooty mangabey called SIV, sooty mangabey is an old world monkey from litoral West Africa.
The virus is transmitted in many different ways, but most commonly trough exposure to body fluids or tissues. That means you can get infected if you had sex (anal, vaginal, oral), sharing a needle or receiving a blood transfusion from an infected person.
The transmission of HIV trough sex happens if you have unprotected sex and although the risk of getting infected is less than 1% per act the risk is still there and it is increased if a partner has any sexually transmitted infections or genital ulcers and also having rough sex will increase the risk because of cuts or breaks that might occur which will allow easy enterance in the blood stream. Risk of getting HIV from blood transfusions has been greatly reduced in higher income countries due to regular screening of donor blood, but there is still a great risk from sharing a needle during drug injections.
Third way of getting an HIV infection is a mother to child transmission that can happen during pregnancy, breastfeeding or delivery. There are ways to prevent this to happen, the one that is used commonly is taking antiretrovirals during pregnancy and delivery, avoiding breastfeeding and giving antiretrovirals to the newborn baby after its birth. About 90% of HIV infected children got the infection trough vertical transmission. After the virus enters the bloodstream the replication cycle begins. After HIV virus comes in contact with T cell it attaches itself to the cell and fuses with it so it can inject its genetic material into it. The attachment is a specific binding of proteins on the surface of the cell and the virus. Once the virus is attached the virus penetrates the cell and injects the genetic core into the cytoplasm, after that viral envelope and the cells membrane fuse together.
After the penetration the nucleocapsid gets partially dissolved and RNA from the virus gets converted to DNA so it can be integrated into the cells DNA. HIV’s RNA gets converted to a double stranded DNA via the help of enzyme reverse transcriptase the reverse transcription will be complete. After the reverse transcription is succesful the converted DNA will be integrated in the cells DNA and in order for that to happen the converted DNA will need to be transported across the nuclear membrane and to the nucleus. When the integration occurs the cell becomes latently infected with the virus and waits for its activation. Once it is activated it will begin producing the components of HIV, from the viral DNA two strands of RNA will be created and the first will create subunits of HIV and the second will become the genetic materal of the new viruses.
The created subunits will be processed and separated so they can be assembled into the new virus with the help of protease enzyme. The HIV subunits will make up new virons if the separation is succesful. The particles will deform a section of membrane and the nucleocapsid will take shape with RNA tightly fit inside.
In the final stage of the lifecycle the nucleocapsid and the materials inside it will merge with the deformed membrane and create a new virus that will enter the bloodstream and continue the process all over again, the side effect of this is that the T cell gets severely damaged and dies. With the amount of virus in the organism that continually cause the death of T cells as a effect of their reproduction mechanism it will cause progressive worsening of immune system and lead to AIDS.