Natural history of HIV-1 infection

Infection with the human immunodeficiency virus type 1 (HIV-1) results in p rogressive loss of immune function marked by depletion of the CD4+ T-lympho cytes, leading to opportunistic infections and malignancies characteristic of AIDS. Although both host and viral determinants influence the rate of di sease progression, the median time from initial infection to the developmen t of AIDS among untreated patients ranges from 8 to 10 years. The clinical staging of HIV disease and the relative risk of developing opportunistic in fections historically relied on the CD4+ T-lymphocyte counts. Although more recent studies have shown the importance of viral load quantitation in det ermining the rate of disease progression, it is still useful to categorize HIV disease stage on the basis of the degree of immunodeficiency: early dis ease (CD4+ > 500 cells/mL), mid-stage disease (CD4+ between 200 and 500 cel ls/mL), and end-stage disease (CD4+ < 50 cell/ mL). This article reviews th e natural history of HIV disease at each stage of HIV-1 infection with emph asis on acute infection and the major virologic and immunologic determinant s of disease progression.