P33.01
Background: The lectin griffithsin (GRFT) is a homodimer isolated from the red alga griffithsia sp. GRFT has demonstrated potent and broad anti-HIV-1 activity across subtypes and is one of the leading HIV-1 microbicide candidates. The GRFT Derivatives 2MG, 2MG3, 3MG and 4MG are made of arrays of two, three and four monomeric GRFT units, respectively.
Methods: We evaluated HIV-1 subtype A, B and C against 2MG, 2MG3, 3MG, 4MG and GRFT using the TZM-bl neutralization assay. GRFT derivatives were also tested for their inhibition of the cell-to-cell transmission of HIV-1. The 234 and 295 glycans, shown to be important in GRFT binding to HIV-1, were introduced in the virus by site directed mutagenesis, and their effects on 2MG, 2MG3, 3MG and 4MG binding studied. GRFT resistant viruses were generated by culturing HIV-1 under escalating concentrations of the lectin. These resistant viruses were then tested for sensitivity to 2MG, 2MG3, 3MG and 4MG.
Results: In general 2MG and 2MG3 were as potent as GRFT against all the viruses tested while 3MG and 4MG were more potent against HIV-1 subtype A and C. GRFT was also less potent than these two derivatives in the inhibition of cell-to-cell transmission of HIV-1. Similar to GRFT, the introduction of the 234 and 295 glycans affected HIV-1 sensitivity to 2MG and 2MG3; while it did not affect 3MG and 4MG neutralization of the virus. Lastly, GRFT resistant viruses showed sensitive to 3MG and 4MG.
Conclusions: The 3MG and 4MG derivatives were more potent than GRFT in inhibiting HIV-1 infection. Also viruses that showed resistance to GRFT remained sensitive to these compounds. It is possible that 3MG and 4MG binding site on the viral envelope is different from that of GRFT given that the 234 and 295 glycans do affect their neutralization of the virus. The data generated from these studies suggests that linking GRFT into arrays of more than two monomeric units increases its potency against HIV-1.
