Interpretation of Western blots of specimens from children infected with human immunodeficiency virus type 1: Implications for prognosis and diagnosis

Abstract

The current method of diagnosing human immunodeficiency virus type 1 infection in adults is based on serologic detection of HIV-1 antibodies by means of an enzymelinked immunosorbent assay, with subsequent confirmation by Western blot immunoassay. The Western blot qualitatively measures the presence of antibody to a number of virus-associated proteins, including major group-specific antigen proteins, envelope proteins, and polymerase gene products. In the Western blot assay, proteins from a lysate of HIV-1 are separated according to size with the use of polyacrylamide gel electrophoresis. The electrophoresed proteins are transferred to nitrocellulose paper and reacted with patient serum. The HIV-1 antibody from the patient's serum is then detected by an antihuman IgG antibody conjugated with an enzyme. When the nitrocellulose paper is exposed to substrate, a colored band will appear on the paper where serum antibody was bound to viral protein. Western blot immunoassays have recognized limitations: 32% of adults without antibody detected by ELISA, who are at low risk for HIV-1 infection, may have Western blot reactivity, resulting in an indeterminate interpretation. 1 Indeterminate Western blots also are obtained late in the course of adult HIV1 infection, when there is a loss of antibodies to core HIV-1 antigens, z, 3 In infants, the serologic diagnosis of HIV-1 infection is confused by the presence of HIV-1 antibodies transplacentally acquired from the mother. Of those infants who are offspring of H1V-1 seropositive mothers, but who are not