“…Indeed, in the United States and Europe, it is estimated that 10% to 20% of new infections are caused by HIV-1 strains harboring resistance to at least one of the three main types of ARV drugs: entry/fusion inhibitors, RTIs, or protease inhibitors (6,11,12,30,46,58,70,77). Although levels of RTI resistance in the developing world are not fully characterized (26,48,49,63,72), they are likely to increase with the scale-up of ARV therapy. The development of combination ARV rectal microbicides might provide an important defense against rectal transmission of resistant strains of HIV-1 in regions where treatment of chronic HIV infection has resulted in the emergence of ARV resistance.…”