The fact that the two patients displaying clusters of sequences predictive of CXCR4 usage in proviral HIV DNA in monocytes have been on fully suppressive HAART for almost the entire time of the infection, although intriguing, is not completely unexpected, as in a recent study where X4 viruses (either pure or dual/mixed R5/X4) were recognized in 17.2% of patients studied early after seroconversion [38]. This evidence concerns the gene CXCR4 and infection.