Recombinant protein of heptad-repeat HR212, a stable fusion inhibitor with potent anti-HIV action in vitro

HR212, a recombinant protein expressed in Escherichia coli, has been previously reported to inhibit HIV-1 membrane fusion at low nanomolar level. Here we report that HR212 is effective in blocking laboratory strain HIV-1IIIB entry and replication with EC50 values of 3.92 ± 0.62 and 6.59 ± 1.74 nM, respectively, and inhibiting infection by clinic isolate HIV-1KM018 with EC50 values of 44.44 ± 10.20 nM, as well as suppressing HIV-1-induced cytopathic effect with an EC50 value of 3.04 ± 1.20 nM. It also inhibited HIV-2ROD and HIV-2CBL-20 entry and replication in the µM range. Notably, HR212 was highly effective against T20-resistant strains with EC50 values ranging from 5.09 to 7.75 nM. Unlike T20, HR212 showed stability sufficient to inhibit syncytia formation in a time-of-addition assay, and was insensitive to proteinase K digestion. These results suggest that HR212 has great potential to be further developed as novel HIV-1 fusion inhibitor for treatment of HIV/AIDS patients, particularly for those infected by T20-resistant variants.