Natural antibodies to HIV‐tat epitopes and expression of HIV‐1 genes in vivo

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Abstract
The tat regulatory protein of HIV‐1 was expressed as a fusion protein in E. coli and used as antigen to detect antibodies against HIV‐tat (anti‐tat) in the serum of HIV‐1 infected children and adults. HIV‐1‐infected children showed a higher frequency (55%) of anti‐tat than HIV‐1‐infected adults (36%). Anti‐tat were present in only 15% (3/20) of acutely infected individuals. Forty percent (10/25) of individuals with prolonged HIV‐1 infection but without antigen were anti‐tat positive. Only 13% (3/23) of HIV‐1‐antibody‐positive individuals with prolonged HIV‐1 antigenemia were anti‐tat positive and titers of anti‐tat antibodies declined with time. Pepscan analysis identified the amino terminus of HIV‐tat as the major antibody‐binding site. Antibodies to HIV‐tat occurred as a harbinger of HIV‐1 antigen expression and disappeared thereafter, possibly reflecting the transience of HIV‐tat expression. Because of the low antigenicity of HIV‐tat, antibodies to this regulatory protein are not a reliable marker for either early HIV‐1 infection or subsequent disease progression.