Moreover, some viruses can exploit the complement system to promote infection, either by binding directly to complement receptors (CRs) to gain entry to host cells or indirectly through complement-opsonized virus interactions.35, 36, 37, 38 Interaction of rAAV-1 and rAAV-6 with CRP in mouse serum is another example of enhancement of viral vector efficacy by the host defense system.9, 10. Here, CRP is linked to infection.