HIV/AIDS in the 2000s

The human immunodeficiency virus in (HIV) is the etiological agent for acquired immune deficiency syndrome (AIDS).

Since AIDS was first recognized in 1981, approximately thirty million persons have died from the disease. While no vaccine was developed to prevent the disease during the first decade of the twenty-first century, improved programs for treatment and the institution of preventive measures resulted in a decrease in mortality of nearly 25 percent.

HIV is the virus class known as retroviruses, of which the genome is ribonucleic acid (RNA) and that replicate through a deoxyribonucleic acid (DNA) intermediate. The agent uses a viral enzyme, reverse transcriptase, to copy the genome into DNA, which integrates into the host chromosome. The specific cell infected and killed is the T lymphocyte, a cell that regulates the immune response. The virus requires two proteins on the surface of the cell for infection; the CD4 protein allows attachment of the virus, while a hormone (chemokine) receptor is necessary for entry. Mutations in either prevent infection. Once the virus is replicating it requires another enzyme, a protease that cleaves a viral protein that constitutes part of its structure, for maturation and release. Antiviral therapy has largely targeted either the reverse transcriptase or protease.

Depletion of CD4+ cells, the T lymphocytes, below 1000 per microliter of blood places a person at risk for any of a large number of opportunistic infections. AIDS is identified when the person is HIV positive and has been diagnosed with any of these infections.

Incidence and Prevalence of AIDS

While no vaccine has proven effective in protecting against AIDS, preventive measures have reduced the likelihood of infection. A 2006 study demonstrated that male circumcision significantly reduced the risk of infection; diaphragm usage by women however, demonstrated no reduction in risk.

Estimates are that 68 million persons worldwide are infected (as of 2012), most in underdeveloped countries. In the United States total AIDS cases are estimated at 1.3 million. While the yearly incidence of AIDS in the United States had declined by 2001, numbers increased after 2002. African Americans and Latinos represented 75 percent of new cases. In part, this was the result of poor education addressing the risk of infection; a significant number of people have shown indifference to their risk of contracting the disease or falsely believe there is a cure. Many of the cases are among gay men (defined as “men who have sex with men”); a 2007 study found nearly half of gay African Americans may be HIV positive. Many of these men were initially unaware they were HIV positive.

Prospective Treatments for AIDS in the Near Future

Antiretroviral therapy is generally started when the number of CD4+ cells drops below 350 per microliter of blood. Beginning in 2011, a worldwide study known as START has tested if the initiation of antiretroviral therapy when CD4+ numbers drop to 500 is more useful in reducing the level of virus than when the number drops to 350. The theory is that earlier treatment may both prove more beneficial and decrease the risk of transmission to an HIV-negative partner. Early results using some eleven different drugs targeting both the viral reverse transcriptase and viral protease demonstrated more than a 90 percent reduction in transmission to previously uninfected partners.

Another approach addressed the question of whether pre-exposure prophylaxis (PrEP) may actually prevent infection in men who refuse to practice safe sex. Clinical trials began in 2007 among HIV-negative gay men in six countries. They were given the drug Truvada, an inhibitor of reverse transcriptase. A 2011 report suggested a reduction in infection of more than 75 percent in men who maintained the recommended schedule in use of the drug.

Since the chemokine protein CCR5 on the surface of CD4+ cells is necessary for entry of the virus, scientists are testing whether genetically engineered cells that lack the protein may render the person resistant to the disease. The initial test case was an HIV-positive individual who developed leukemia. Following eradication of bone-marrow cells to treat the leukemia, the patient received a transplant from an individual whose cells lacked the CCR5 protein. After five years the patient showed no evidence of AIDS. Further research has taken place to test the usefulness of the approach in other HIV-infected persons.

Impact

The use of combinations of drugs, referred to as drug “cocktails,” for treatment of AIDS, highly active antiretroviral therapy (HAART) originated in 1996 and represented the first long-term effective treatment of the disease. The cost of manufacturing the drugs, as well as the accessibility of treatment in poor countries, has resulted in limited availability in much of the world. Political changes in countries such as those in southern Africa, the site for much of the increase in HIV incidence, have allowed an increased awareness of how the virus is transmitted. Attempts to reduce prostitution and to educate the populations about the use of condoms have met with only limited success.

HAART therapy has proven much more successful in developed countries. The transmission of HIV from infected women to children has been reduced from 25 percent to nearly 1 percent; the goal is to eliminate such transmission by 2015. Early treatment of infected persons, or pre-exposure prophylaxis, has significantly extended the prospective life span of patients and has shown strong evidence that risk of transmission to an uninfected partner is also reduced.

Bibliography

Harden, Victoria. AIDS at Thirty: A History. Washington, DC: Potomac, 2012. Print.

June, Carl, and Bruce Levine. “Blocking AIDS Attack.” Scientific American 306.3 (2012): 54–59. Print.

Montagnier, Luc. Virus: The Co-Discoverer of HIV Tracks Its Rampage and Charts the Future. New York: Norton, 2000. Print.

Stine, Gerald. AIDS Update 2012. New York: McGraw, 2012. Print.

Timberg, Craig, and Daniel Halperin. Tinderbox. New York: Penguin, 2012. Print.