The Relationship between the Human Immunodeficiency Virus and the Acquired Immunodeficiency Syndrome (Draft)

DRAFT

One feature that distinguishes lentiviruses from other retroviruses is the remarkable
complexity of their viral genomes. Most retroviruses that are capable of replication contain
only three genes--env, gag and pol (Varmus, 1988). HIV contains not only these essential
genes but also the complex regulatory genes tat, rev, nef, and auxiliary genes vif, vpr, vpu
(Greene, 1991). The actions of these additional genes probably contribute to the profound
pathogenicity that differentiates HIV from many other retroviruses.
CD4+ T cells, the cells depleted in AIDS patients, are primary targets of HIV because
of the affinity of the virus for the CD4 molecule and specifically the viral envelope glycoprotein
gpl 60 (Dalgleish et al., 1984; Klatzmann et al., 1984b; McDougal et al., 1985a, 1986). These
so-called T-helper cells coordinate a number of critical immunologic functions. The loss of
these cells results in the progressive impairment of an HIV-infected individual's immune
response and is associated with a deteriorating clinical course (Pantaleo et al., 1993a). In
advanced HIV disease, abnormalities of virtually every component of the immune system are
evident (Fauci, 1993a; Pantaleo et al., 1993a).
Course of HIV Infection
Primary HIV infection is associated with a burst of HIV viremia and a concomitant
abrupt decline of CD4+ T cells in the peripheral blood (Daar et al., 1991; Tindall and Cooper,
1991; Clark et al., 1991; Pantaleo et al., 1993a). The decrease in CD4+ T cells during
primary infection is probably due both to HIV-mediated cell killing and to retrafficking of cells
to the lymphoid tissues and other organs (Fauci, 1993a).
The median period of time between infection with HIV and the onset of clinically
apparent disease is approximately 10 years, according to prospective studies of homosexual
men in which dates of seroconversion are known (Lemp et al., 1990; Hessol et al., 1994).
Similar estimates of asymptomatic periods have been made for HIV-infected blood-transfusion
recipients, injection-drug users, and adult hemophiliacs (Eyster et al., 1987; Ward et al., 1989;
Moss et al., 1989; Goedert, et al., 1989).

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