Structure of HIV Virus
The Human Immunodeficiency Virus (HIV) is a complex retrovirus that has been extensively researched since its discovery in 1983. The structure of HIV follows the typical pattern of the retrovirus family, with a single-stranded, positive-sense ribonucleic acid (RNA) genome of about 9.2 kilobases.
Genome and Proteins
The HIV genome encodes a small number of viral proteins, invariably establishing cooperative associations among HIV proteins and between HIV and host proteins, to invade host cells and hijack their internal machineries. The genome of HIV encodes 8 viral proteins playing essential roles during the HIV life cycle. HIV is composed of two strands of RNA, 15 types of viral proteins, and a few proteins from the last host cell it infected.
Virion Structure
The HIV virion is approximately 100 nm in diameter. Its innermost region consists of a cone-shaped core that includes two copies of the positive sense ssRNA genome, the enzymes reverse transcriptase, integrase and protease, some minor proteins, and the major core protein. This core is enclosed by a capsid, which itself is enclosed by a viral envelope and associated matrix.
RNA Genome
The two RNAs are often identical, yet they are not independent, but form a compact dimer within the virion. Several reasons as for why two copies of RNA are packaged rather than just one have been proposed, including probably a combination of these advantages: One advantage is that the two copies of RNA strands are vital in contributing to HIV-1 recombination, which occurs during reverse transcription of viral replication, thus increasing genetic diversity. Another advantage is that having two copies of RNA would allow the reverse transcriptase to switch templates when encountering a break in the viral RNA, thus completing the reverse transcription without loss of genetic information. Yet another reason is that the dimeric nature of the RNA genome of the virus may play a structural role in viral replication.
Role in Infection
HIV infects cells of the immune system and forces them to build new copies of the virus. Each molecule in the virus plays a role in this process, from the first steps of viral attachment to the final process of budding. Since 1986, research on the structural biology of HIV have revealed the atomic details of these proteins.
Conclusion
Understanding the structure of HIV is crucial for the development of effective treatments and vaccines. The detailed knowledge of its structure has allowed researchers to design new treatments for HIV infection, including effective drug regimens that halt the growth of the virus.
