Contributed by Oliver Ting, Jackson Fritz and Milan Patel

According to a report from the World Health Organization, human immunodeficiency virus (HIV) infected about 2.7 million new people in 2010 alone. Broken down, HIV destroys the immune system in humans, allowing opportunistic diseases to come in and kill the patient. HIV spreads through bodily fluid from person to person. Once inside a patient, HIV targets certain cells within the immune system called T-cells. HIV forces these cells to create new copies of the virus and destroys the T-cells in the process. As the virus grows exponentially, the immune system loses its ability to fight other diseases, leading to acquired immune deficiency virus (AIDS).

HIV cannot be cured. The main problem in creating a drug that treats HIV is that the virus is constantly changing. HIV is a retrovirus, meaning it uses RNA and then converts that into DNA when it infects cells. Retroviruses use an enzyme called reverse transcriptase to do this. However, unlike DNA enzymes, this enzyme cannot proofread itself, allowing more mutations (changes in the genetic code) to occur. This causes the virus to produce a base mismatch roughly every 10, 000–30, 000 bases during the replication. This differs significantly from regular viruses that typically have a range of one base mismatch per one million to one billion base pairs. When these base mutations occur in specific regions of the HIV DNA, new types or subtypes of the virus can be created. HIV builds up drug resistance because a drug that was effective for a previous variation of HIV may not be effective against a new variant of the virus. In addition, the virus builds cross-resistance, and becomes resistant to multiple types of HIV drugs within the same class. This further limits the number of drugs that can be used to treat the virus.

HIV is a prime example of evolution in action. HIV’s high rate of DNA mutation creates many variants. When HIV is selected against through antiviral drugs, certain variants survive that are resistant to the drug. These drug-resistant strains of HIV survive to reproduce and can be transmitted to other individuals. This constantly changing HIV population produces a substantial obstacle in trying to treat and eradicate the virus. Continued research is required to combat this evolving virus and improve the quality of life of those affected by HIV and AIDS.

Inspired by Radiolab “Patient Zero”, a fascinating tale about how HIV began, where it came from, and who “Patient 0” may have been. The podcast further reinforces how the virus has been able to combat so many challenges to its existence as well as it has.

Further Reading:

Bao, Yi, et al. “Characteristics Of HIV-1 Natural Drug Resistance-Associated Mutations In Former Paid Blood Donors In Henan Province, China.” Plos ONE 9.2 (2014): 1-9.

Bennett, Diane E . et al. “Drug Resistance Mutations for Surveillance of Transmitted HIV-1 Drug-Resistance: 2009 Update.” Ed. Douglas F. Nixon. PLoS ONE 4.3 (2009): E4724.

Sanjuan, R. et al. “Viral Mutation Rates.” Journal of Virology 84.19 (2010): 9733-748.

Shilts, Randy. And the Band Played On: Politics, People, and the AIDS Epidemic. New York: St. Martin’s, 1987.