Clinical Implications of Identifying Non-B Subtypes of Human Immunodeficiency Virus Type 1 Infection (original) (raw)

Although human immunodeficiency virus type 1 (HIV-1) infection in the United States has predominantly involved subtype B, increasing global travel is leading to wider dissemination of genetically heterogeneous subtypes. While physicians depend on HIV-1 viral load measurements to guide antiretroviral therapy, commonly used molecular assays may underestimate the viral load of patients with non-B subtypes. Nine patients with non-B subtypes of HIV-1 were identified by physicians who suspected a non-B subtype on the basis of a low or undetectable HIV-1 viral load, by the Amplicor HIV-1 Monitor test, version 1.0, in conjunction with either a declining CD4 cell count or history of travel outside the United States. Use of version 1.5 of the Amplicor HIV-1 Monitor test detected a median HIV-1 viral load that was 2.0 log 10 RNA copies/mL higher than was determined with version 1.0. Clinical management was altered in all cases after diagnosis of a non-B-subtype infection. These cases demonstrate that it is critical for physicians to suspect and diagnose non-B subtypes of HIV-1 so that an assay with reliable subtype performance can be used to guide antiretroviral therapy. One of the challenges facing physicians and researchers who work with HIV-1 is the extensive genetic heterogeneity among HIV-1 isolates from around the world. Molecular epidemiological studies have identified 3 major phylogenetic groups of the virus (M, O, and N), which differ in their prevalence and geographic distribution [1-3]. Most isolates fall into group M (major), which is further subdivided into at least 9 distinct