Immunotherapy for Infectious Diseases

INTRODUCTION
Immunopathogenesis of HIV Infection
From: Immunotherapy for Infectious Diseases
Edited by: J. M. Jacobson © Humana Press Inc., Totowa, NJ
151
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Lawrence M. Fox
AIDS was recognized in the United States in 1981, when scientists at the Centers for Disease
Control and Prevention (CDC) noted a cluster of cases of Pneumocystis carinii pneumonia
and Kaposi’s sarcoma in homosexual men in New York City and Los Angeles. HIV
was isolated in 1983 and was demonstrated to be the agent of AIDS in 1984. HIV is a retrovirus
of the lentivirus family, which includes the human lymphotropic viruses (human T-cell
lymphoma virus [HTLV]-I and II) and HIV-1 and -2. HIV-2 infection is largely confined to
West Africa. HIV-1 is responsible for the world AIDS pandemic, which is now the number
one cause of death owing to infectious disease in the world. Currently, 34 million people are
estimated to be infected with HIV-1, and 14 million have died from AIDS (1).
HIV DISEASE
Etiology
HIV-1 is divided into subtypes or clades. The major clades, group M, are designated
A–I; the less common group O has been largely confined to West and Central Africa.
Based on maps of genetic diversity between clades and compared with the simian
immunodeficiency viruses (SIVs) that are endemic in African monkeys, HIV-1 is
believed to have derived from mutation of an SIV, whose original host was probably a
chimpanzee (2). HIV-1 is thought to have then infected human groups that lived in
close proximity to infected chimpanzees, and possibly kept them as pets or hunted
them. Most likely, HIV remained for decades a disease largely confined to rural African
villages, until urbanization of Africa eventually permitted worldwide spread.
The disease is spread through contact of infected body fluids, usually blood, semen
or breast milk, by the mucous membranes or directly into the recipient’s blood or an
open wound. The vast majority of cases of HIV-1 infection in the world are the result
of heterosexual intercourse. In the United States, the disease was originally largely confined
to homosexual men and then spread into intravenous drug users through the sharing
of needles. HIV infection is now rapidly increasing among women, both through
intravenous drug use and via sexual intercourse with infected men. Pediatric HIV infection
usually occurs during labor and delivery from an infected mother but may also
occur earlier in gestation or later, as a result of breast feeding.