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To examine whether polyclonal activation of circulating B cells, in a process that involves CD40–CD40 ligand and cytokine interactions, could induced HIV-1-specific memory B cells to synthesize HIV-1-specific antibodies.B cells from 26 HIV-1-infected patients were cultured with a CD40L-transfected cell line plus interleukins 2 and 10 and tested for their secretion of HIV-1- and Toxoplasma gondii-specific antibodies.In vitro activated B lymphocytes from HIV-1-infected patients secreted anti-HIV-1-specific antibodies. B cells from HIV-1-infected patients as well as those from controls chronically infected by T. gondii synthesized T. gondii-specific antibodies. HIV-1-specific IgG-, IgA- or IgM-secreting B cells represented approximately 1 × 10−4 to 1 × 10−5 of total circulating B cells and 1 × 10−2 to 1 × 10−3 of immunoglobulin-secreting cells. HIV-1-specific memory B cells were found in 9/9 untreated patients and in 8/17 patients receiving highly active antiretroviral therapy (HAART). The other nine patients showed a normal CD40–CD40L B cell response and six of them produced T. gondii-specific antibody B cells. The follow-up of seven patients indicated that HIV-1-specific memory B cells became undetectable after 8 to 46 months of HAART, whereas T. gondii-specific memory B cells persisted in parasite coinfected patients.Circulating memory HIV-1-specific B cells were detected in untreated patients and in about half of the patients taking HAART, suggesting that persistent low-level ongoing viral replication is not sufficient to maintain HIV-1-specific memory B cells.