CypA also regulates the infection by variousviruses like HIV-1 and hepatitis C. Several efforts have been madeto design and develop potent isoform-specific inhibitors for CypAand other cyclophilin isoforms.21−24 Insights into the dynamics of CypA and other cyclophilinsand how it can be modified by variations of the primary structuremay provide information needed to develop new isoform-specific cyclophilininhibitors and also to engineer new enzymes for better PPIase activities. The gene discussed is PPIA; the disease is hepatitis A virus infection.