Early Neutralizing Antibodies in Infants Living With HIV to Enhance Their Life

The goal of this clinical trial is to learn if subcutaneous ePGT121v1-LS added to standard antiretroviral therapy (ART) is safe and helps improve HIV viral suppression in infants living with HIV in South Africa. The study will also learn how the body processes ePGT121v1-LS and whether caregivers and health workers find this treatment approach acceptable. The main questions it aims to answer are: * Is ePGT121v1-LS safe and well tolerated in infants living with HIV? * Does adding ePGT121v1-LS to standard ART increase the number of infants who achieve HIV viral suppression by week 48? * How long does it take participants receiving ePGT121v1-LS to achieve viral suppression compared with standard treatment alone? * How does ePGT121v1-LS behave in the body after repeated subcutaneous injections? Researchers will compare infants receiving ePGT121v1-LS plus ART to infants receiving standard ART plus placebo (saline) to see if ePGT121v1-LS improves HIV viral suppression. Participants will: * Continue taking standard oral ART. * Receive 4 subcutaneous injections of ePGT121v1-LS or placebo every 12 weeks. * Attend regular clinic visits for safety checks, blood tests, and HIV viral load monitoring. * Have follow-up visits for 48 weeks. * Participate in evaluations of treatment adherence and acceptability from the perspective of caregivers and health workers.