Scavenger receptor CD163 is a key entry mediator for porcine reproductive and respiratory syndrome virus (PRRSV). To identify the CD163 protein domains involved in PRRSV infection, deletion mutants and chimeric mutants were created. Infection experiments revealed that scavenger receptor cysteine-rich (SRCR) domain 5 (SRCR 5) is essential for PRRSV infection, while the four N-terminal SRCR domains and the cytoplasmic tail are not required. The remaining CD163 protein domains need to be present but can be replaced by corresponding SRCR domains from CD163-L1, resulting in reduced (SRCR 6 and interdomain regions) or unchanged (SRCR 7 to SRCR 9) infection efficiency. In addition, CD163-specific antibodies recognizing SRCR 5 are able to reduce PRRSV infection.