Beta amyloid precursor protein and patterns of HIV p24 immunohistochemistry in different brain areas of AIDS patients

Objectives: To evaluate the correlation between immunohistochemical positive patterns (globular and filamentous structures) of β-amyloid precursor protein (β-APP), used as a marker of axonal damage, and the different distribution of HIV p24 antigens, in three different brain areas of AIDS patients. Methods: Eighteen AIDS patients with HIV-related brain lesions were included in the study. Forty-nine sections from basal ganglia, frontal cortex and hippocampus were selected. After microwave oven pre-treatment, the sections were incubated with anti-HIV p24 and anti-β-APP monoclonal antibodies; the reactions were developed with peroxidase/3,3′diaminobenzidine. The positivity was graded by semi-quantitative scores. Double immunohistochemical staining was used to evaluate the co-localization of the antigens. Results: HIV p24 immunohistochemistry was positive in 44 of 49 sections (89%), with a prevalence of interstitial positive cells and positive microglial nodules in 27 and 13 sections respectively. β-APP-positive structures were demonstrated in 23 of 44 sections (52%) with HIV-related lesions, and were absent from the five sections without viral expression. Globular and filamentous lesions were observed in 21 of 23 sections and 10 of 23 lesions respectively. Moreover, a high grade of globular type lesion was related to an elevated presence of diffuse interstitial HIV p24-positive cells in basal ganglia; double immunohistochemical reactions demonstrated the co-localization of β-APP globules and HIV p24 antigens. Conclusions: The data obtained confirm the coexpression of β-APP and viral antigens in particular areas of the brain with HIV-related lesions; there is a strict correlation between β-APP globules (indicating chronic cerebral damage) and the interstitial pattern of HIV p24 immunohistochemistry.