The present invention relates to methods for preventing or treating Human Immunodeficiency Virus (HIV) infection, inflammatory conditions, and graft-versus-host-disease (GVHD) in a subject. Therapeutic compositions of the present invention comprise Leukocidin E (LukE) and/or D proteins or polypeptides. The invention further relates to methods of treating Staphylococcus aureus infection by administering a composition comprising a CCR5 antagonist or any molecule that blocks LukE/D interaction with CCR5+ cells in an amount effective to treat the S. aurreus infection in the subject.
