0.05 vs. R5 HIV-1; #p < 0.05 vs. R5 + morphine (M); ¶p < 0.05 vs. R5 + maraviroc (MVC); §p < 0.05 vs. R5 + M + MVC; ¥p < 0.05 vs. R5 + M + MVC + naltrexone). (a–b) Modified and reprinted with permission from Arnatt et al. (