HIV Infection and AIDS

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HIV infection and AIDS

Definition

Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immune deficiency syndrome (AIDS) by infecting helper T cells of the immune system. The most common serotype, HIV-1, is distributed worldwide, while HIV-2 is primarily confined to West Africa. AIDS is a severe immunological disorder caused by the retrovirus HIV, resulting in a defect in cell-mediated immune response that is manifested by increased susceptibility to opportunistic infections and to certain rare cancers, especially Kaposi's sarcoma. It is transmitted primarily by exposure to contaminated body fluids, especially blood and semen. Everybody who has AIDS also has HIV disease, but not everybody with HIV disease is classified by the United States (U.S.) government as having AIDS. The U.S. government uses CD4 cell counts (part of the immune system) to make this distinction.

Description

The earliest known case of HIV-1 came from a human blood sample collected in 1959 from a man in Kinshasa, Democratic Republic of Congo. The method by which he became infected is not known; however, genetic analysis of his blood sample suggested that HIV-1 might have stemmed from a single virus in the late 1940s or early 1950s. HIV has existed in the United States since the mid to late 1970s. During 1979 to 1981, rare types of pneumonia , cancer , and other illnesses were reported by physicians in Los Angeles and New York among a number of male patients who had sex with other men. Since it is rare to find these diseases in people with a healthy immune system, public health representatives became concerned that a new virus was emerging.

In 1982, the term AIDS was introduced to describe the occurrences of opportunistic infections, Kaposi sarcoma, and Pneumocystis carinii pneumonia in previously healthy persons and formal tracking of these cases in the United States began that year. The virus that causes AIDS was discovered in 1983 and named human T-cell lymphotropic virus-type III/lymphadenopathyassociated virus (HTLV-III/LAV) by an international scientific committee who later changed it to HIV. Many theories as to the origins of HIV and how it appeared in the human population have been suggested. The majority of scientists believed that HIV originated in other primates and was somehow transmitted to man. In 1999, an international group reported the discovery of the origins of HIV-1, the predominant strain of HIV in the developed world. A subspecies of chimpanzees native to west equatorial Africa were identified as the original source of the virus. The researchers believe that HIV-1 was introduced into the human population when hunters became exposed to infected blood.

Most scientists believe that HIV causes AIDS by directly inducing the death of CD4+ T cells (helper T cells in the immune system) or interfering with their normal function and by triggering other events that weaken a person's immune function. For example, the network of signaling molecules that normally regulates a person's immune response is disrupted during HIV disease, impairing a person's ability to fight other infections. The HIV-mediated destruction of the lymph nodes and related immunologic organs also plays a major role in causing the immunosuppression seen in persons with AIDS.

In the absence of antiretroviral therapy, the median time from HIV infection to the development of AIDS-related symptoms has been approximately 10 to 12 years. A wide variation in disease progression, however, has been noted. Approximately 10 percent of HIV-infected persons have progressed to AIDS within the first two to three years after infection, whereas up to 5 percent of persons have stable CD4+ T cell counts and no symptoms even after 12 or more years. Factors such as age or genetic differences among persons with HIV, the level of virulence of an individual strain of virus, and co-infection with other microbes may influence the rate and severity of disease progression. Drugs that fight the infections associated with AIDS have improved and prolonged the lives of HIV-infected persons by preventing or treating conditions such as Journal of Infectious Diseases. This approach is known formally as short-cycle structured intermittent antiretroviral therapy (SIT) or colloquially as the "7-7" approach. Dr. Mark Dybul, of the National Institute of Allergy and Infectious Diseases (NIAID) and the study author, noted that this approach together with high patient adherence could be a powerful and cost-effective tool in HIV treatment. This regimen uses half as much antiretroviral medication so not only are drug costs reduced but drug-related toxicities may be less in the long run. He believes that this is particularly important to countries with few resources around the world.

Nutritional concerns

Nutrition is definitely a concern for the individual who is HIV infected and even more so for the individual who has progressed to AIDS. The antiretroviral drugs have numerous side effects that make eating an adequate diet difficult and the disease itself affects nutritional intake. It is important for HIV individuals to supplement their diet with vitamins and minerals as well as protein drinks to maintain their energy. There are many supplements on the market and in health food stores that can be of benefit. The patient needs to go in search of what best suits their tastes.

Prognosis

The prognosis for individuals with AIDS in recent years has improved significantly because of new drugs and treatments, and educational and preventive efforts. Women whose HIV infections are detected early and receive appropriate treatment survive as long as infected men. There are several studies that have shown HIV-infected women to have shorter survival times than men. Women may be less likely than men to be diagnosed early, which may account for shorter survival times. In an analysis of several studies involving more than 4,500 people with HIV infection, women were one-third more likely than men to die within the study period. The investigators could not definitively identify the reasons for excess mortality among women in this study, but they speculated that poorer access to or use of health care resources among HIV-infected women as compared to men, domestic violence, homelessness, and lack of social supports for women may have been important factors.

Researchers have observed two general patterns of illness in HIV-infected children. About 20 percent of children develop serious disease in the first year of life; most of these children die by age four years. The remaining 80 percent of infected children have a slower rate of disease progression, many not developing the most serious symptoms of AIDS until school entry or even adolescence . A recent report from a large European registry of HIV-infected children indicated that half of the children with perinatally acquired HIV disease were alive at age nine. Another study, of 42 perinatally HIV-infected children who survived beyond nine years of age, found about one-quarter of the children to be asymptomatic with relatively intact immune systems.

Prevention

Because no vaccine for HIV is available, the only way to prevent infection by the virus is to avoid behaviors that put a person at risk of infection, such as sharing needles and having unprotected sex. Many people infected with HIV have no symptoms; therefore, there is no way of knowing with certainty whether a sexual partner is infected unless he or she has repeatedly tested negative for the virus and has not engaged in any risky behavior. Individuals should either abstain from having sex or use male latex condoms or female polyurethane condoms, which may offer partial protection, during oral, anal, or vaginal sex. Only water-based lubricants should be used with male latex condoms. Although some laboratory evidence shows that spermicides can kill HIV, researchers have not found that these products can prevent a person from getting HIV.

The risk of HIV transmission from a pregnant woman to her baby can be significantly reduced with the use of antiretroviral drugs taken during pregnancy, labor, and delivery and administered to the baby for the first six weeks of life. In addition, the International Perinatal HIV Group reported in 1999 that elective cesarean section delivery could help reduce vertical transmission of HIV, although it is not without risk to certain women.

Parental concerns

Parental concerns are reflected in the status of a reproductive couple to prevent the transmission of the virus before pregnancy and if this is not possible, to obtain adequate prenatal care to prevent the transmission to the baby.

KEY TERMS

B-cell lymphomas —Non-Hodgkin's lymphomas that arise from B cells.

CD4+ cells —Called helper T-cells, these cells work in cell-mediated immunity by causing a form of inflammation to wall off and destroy foreign material as with a bacterial infection.

Co-infection —Concurrent infection of a cell or organism with two microorganisms (pneumonia caused by coinfection with a cytomegalovirus and streptococcus).

Immunosuppression —Techniques used to prevent transplant graft rejection by the recipient's immune system.

Kaposi's sarcoma —A cancer characterized by bluish-red nodules on the skin, usually on the lower extremities, that often occurs in people with AIDS.

Lymphadenopathy —A disorder characterized by local or generalized enlargement of the lymph nodes or lymphatic vessels.

Perinatal —Referring to the period of time surrounding an infant's birth, from the last two months of pregnancy through the first 28 days of life.

Pneumocystis carinii —A parasite transitional between a fungus and protozoan, frequently occurring as aggregate forms existing within rounded cystlike structures. It is the causative agent of pneumocystosis.

Retrovirus —A family of RNA viruses containing a reverse transcriptase enzyme that allows the viruses' genetic information to become part of the genetic information of the host cell upon replication. Human immunodeficiency virus (HIV) is a retrovirus.

T cell —A type of white blood cell that is produced in the bone marrow and matured in the thymus gland. It helps to regulate the immune system's response to infections or malignancy.

See also High-risk pregnancy.

Resources

BOOKS

Cohen, J., and W. Powderly. Infectious Disease. Philadelphia, PA: Mosby, 2003.

PERIODICALS

Schechter, M. "Therapy for early HIV infection: how far back should the pendulum swing?" (Editorial Commentary) Journal of Infectious Diseases 190, no. 6 (Sept. 2004): 1043.

Dybul, M. et al. "A proof-of-concept study of short-cycle intermittent antiretroviral therapy with a once-daily regimen of didanosine, lamivudine, and efavirenz for the treatment of chronic HIV infection." Journal of Infectious Diseases 189, no. 11 (June 2004): 1974–83.

ORGANIZATIONS

Center for Disease Control and Prevention, National Center for HIV, STD and TB Prevention. 1600 Clifton Rd., Atlanta, GA 30333. (800) 311-3435. Web site: <www.cdc.gov/hiv/dhap.htm>.