Figure 1.

Schematic representation of the establishment of morphine-dependence and infection of animals. Nine 1.5- to 2.5-year-old male rhesus macaques (Macaca mulatta) were obtained from the Caribbean Research Primate Center and maintained in the AAALAC-approved Animal Facility at the University of Puerto Rico Medical School. The experimental protocol was approved by the Institutional Animal Care and Use Committee. The body weight of these animals ranged between 3 and 4.2 kg. The animals tested negative for tuberculosis, simian T-cell leukemia virus type-1, and simian retrovirus. The monkeys were divided into two groups (morphine-dependent and control) of six and three, respectively. Morphine dependence was established by injecting increasing doses of morphine (1 to 5 mg/kg of body weight over a 2-week period) every 8 h by the intramuscular route. Morphine injections were maintained throughout the study. The control animals were given the same amount of normal saline at the same time. After 20 weeks of the initiation of morphine/saline injections, all animals were injected intravenously (indicated by vertical arrow on timeline) with a 2-ml inoculum containing 10⁴ 50% tissue culture infectious doses each of SHIV_ku–1b, SHIV_89.6P, and SIV/17E-Fr. Graph: Plasma (top) and cerebrospinal fluid (CSF; bottom) viral load in morphine-dependent rapid progressors (▪), slow progressors (▲), and control macaques (•). Sequential plasma and CSF samples were collected, and viral load was determined by real-time RT-PCR. The results are presented as RNA copy/ml plasma or CSF.