This is a multicentre, open label, non-randomized, prospective, noninferiority study to compare the pharmacokinetics of lopinavir administered with superboosting (LPV/r 1:1) and concurrent RIF treatment or with standard boosting (LPV/r 4:1) without concurrent RIF treatment, and to assess the safety, tolerance, and virological effect of superboosting in HIV-TB co-infected infants and children weighing >3 kg and ≤15 kg.