Antibody reactivity to HIV-1 Vpu in HIV-1/AIDS patients on highly active antiretroviral therapy

Human immunodeficiency virus type 1 (HIV-1) Vpu protein promotes both extracellular release of viral particles and degradation of CD4 in the endoplasmic reticulum. The correlation of anti-Vpu antibody (Ab) reactivity to Vpu and AIDS disease progression was studied in 162 HIV-1/AIDS patients after they had received highly active antiretroviral therapy (HAART) for 1 year. Anti-Vpu Ab reactivity was analyzed by Western blot using a recombinant Vpu protein. Results showed that at baseline (prior to initiation of HAART), 31.5% of patients (51/162) had anti-Vpu Ab. The proportion of anti-Vpu Ab in patients with CD4 counts ≥500, 200-500 and <200/mm³ were 40.6, 34.7 and 14.3%, respectively (χ² test, p < 0.05). In addition, decreasing levels of anti-Vpu Ab reactivity were significantly correlated with increasing levels of HIV-1 viral load. After receiving HAART for 1 year, 7 of 111 anti-Vpu Ab-negative patients (6.3%) seroconverted (-→+ group) and 8 of 51 anti-Vpu Ab-positive (15.7%) patients became negative (+→- group). Among 104 anti-Vpu Ab-negative patients, 40 were selected for analysis of the vpu gene. All of them had an intact vpu gene. Patients were further divided into four groups according to their anti-Vpu Ab serostatus and anti-HIV-1 Ab was measured. The results showed that only the anti-Vpu Ab serocon-verted group (-→+) had increased serum levels of anti-HIV-1 Abs after 1 year of HAART, while the other three groups (+→+, -→- and +→-) had decreased serum levels of anti-HIV-1 Abs after 1 year of HAART (p < 0.05). In conclusion, the presence of anti-Vpu Ab is associated with improved prognosis following HIV-1 infection, and seroconversion of anti-Vpu Ab in patients on HAART indicates significant recovery of immunity.