Additionally, there is a naturally occurring mutation in ccr5 (ccr5∆32) that prevents expression of CCR5 on the cell surface, and individuals homozygous for this mutation are highly resistant to infection with viruses capable of using CCR5, although their cells remain susceptible to infection with CXCR4-using viruses [22,23,24]. The gene discussed is CXCR4; the disease is infection.