Figure 1. Morphine enhances HIV Bal strain (A) and SIV Delta_B670 strain (B) infection of macrophages.

Seven-day-cultured macrophages were incubated with or without morphine (10⁻¹⁰ M) for 24 h before HIV or SIV infection. An opioid receptor antagonist, naltrexone (10⁻⁸ M) was added to macrophage cultures 1 h before morphine (10⁻¹⁰ M) treatment. HIV or SIV RT activity in culture supernatant was determined at day 6 postinfection. Data are expressed as HIV (A) and SIV (B) RT activity in morphine-treated cells (percentage of control) to those in untreated cells, morphine-treated cells plus naltrexone versus morphine only. The results represent the mean ± SD of three experiments using cells from three different donors. Statistical analysis was performed using one-way analysis of variance, and significance is shown with * P<0.05 (morphine vs control or morphine vs morphine + naltrexone).