HTLV-I, HTLV-II, HIV-1 and HIV-2 are all retroviruses. All of them keep their genetic information in their RNA, instead of in DNA. After a retrovirus infects a cell, it makes a DNA copy of its genetic information from its RNA, then goes into the nucleus of the cell and uses the cell to make more viruses.
Adult T Cell Leukemia/Lymphoma
The HTLV-II virus does not cause disease, but scientists are still investigating to see if it has a role in the development of some diseases, according to Dr. Dan Longo, scientific director at the National Institutes of Health in "Harrison's Principles of Internal Medicine." The HTLV-I virus causes adult T cell leukemia/lymphoma, or ATL. There are four kinds of ATL. Most adults have acute ATL, where they usually live for just six months after the diagnosis. They have skin lesions that develop very fast, lesions in their bones and abnormalities in their lungs stomach and intestines. They also have many abnormal lymphocytes circulating throughout their bloodstream. Lymphocytes are white blood cells that normally defend against foreign substances and diseases. In chronic ATL, people do not have any bone lesions or problems with their stomach or intestines. There may be abnormalities in the lungs and skin of smoldering ATL, the third kind of ATL. In lymphomatous ATL, people have enlarged lymph nodes.
Tropical Spastic Paraparesis
The HTLV-I retrovirus causes this disease. According to the National Institutes of Health, the full name of the disease is HTLV-I associated myelopathy/tropical spastic paraparesis or HAM/TSP. The disease affects adults living in the tropics. Scientists hypothesize that the virus somehow interferes with the immune system. People develop paraparesis, or a weakness in their legs. They also have muscle spasms, stiff muscles and problems with their bladder. Some may develop arthritis and an inflammation in their lungs, muscles, skin or eyes. Still others may develop ATL. Longo says that the symptoms of tropical spastic paresis resemble multiple sclerosis in some ways. He also adds that this disease slowly develops and worsens. Approximately 33 percent of adults with this disorder are confined to a bed within 10 years from the time they were diagnosed, and about 50 percent can walk only if they have help.
AIDS
The HIV-1 and HIV-2 viruses cause the acquired immunodeficiency syndrome, or AIDS. People have the diagnosis of AIDS if their white blood cells, called the CD4+ T lymphocytes, have decreased to a certain level or they are developing certain diseases, according to Dr. J. Allen McCutchan, professor of medicine at the University of California in "The Merck Manual for Healthcare Professionals." These diseases include the fungal infections of histoplasma and coccidioides, and the yeast infections of candida and cryptococcus. Histoplasma, coccidioides and cryptococcus will spread throughout the body, while candida infects the mouth, lungs and esophagus. They can develop viral infections caused by herpes simplex, Varicella zoster or cytomegalovirus. Herpes attacks their lungs and esophagus, varicella causes a painful skin infection, while the cytomegalovirus infects the eyes. People with AIDS can develop various cancers and brain infections as well. According to the Centers for Disease Control and Prevention, as of July 2010, there are approximately 1 million people with HIV in the U.S., and more than 18,000 people die with AIDS every year.
References
- Centers for Disease Control and Prevention: HIV and AIDS in the United States
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- National Institutes of Health: NINDS Tropical Spastic Paraparesis Information Page
- The Merck Manual for Healthcare Professionals: Human Immunodeficiency Virus
