Structure-activity, biochemical and antiviral studies on griffithsin(GRFT), cyanovirin(CV-N) and scytovirin(SVN) continue. Currently, we are continuing the clinical development of GRFT as an anti-HIV microbicide. Evaluation of the antiviral proteins GRFT and SVN for activity against ebola have continued with both USAMRIID and NIAID to investigate the proteins we have discovered for activity against pathogenic viruses of potential biodefense interest including MERS. We have also recently begun collaborating with the Centers for Disease Control on the use of these antiviral proteins against both Nipah virus and Rabies. To potentially use PCMBS lectins as anti-HIV microbicides, whose largest need is in resource-poor countries, it was necessary to find large-scale, low-cost methods of production. To address this requirement, we collaborated broadly with researchers to develop options for the agricultural production of these proteins. We have now completed large scale production of the proteins GRFT and CV-Nin plants including tobacco, rice and soy. The PCMBS has steadily collaborated with the MCL to enable structure determination of the bioactive proteins we discover. We have worked with Dr. Alex Wlodawer's group to define the structure of CV-N, SVN and GRFT. During the current review period we have continued this collaboration to evaluate modified GRFT mutants and characterized several GRFT-tandemers with improved potency. GRFT is now entering first-in-human clinical trials as an anti-HIV microbicide with one Phase I clinical trial underway and a second slated to start in 2019. The PCMBS continues to isolate and characterize new anti-HIV proteins from aqueous natural product extracts. We have been working on a new protein isolated from the sponge Vagocia sp, from which no bioactive compounds have so far been reported. Initial studies on the protein fraction of this extract identified potent anti-HIV activity that appeared to bind to HIV-1 gp120. A protein, named vagocin, has been purified to homogeneity by a combination of precipitation techniques, hydrophobic interaction and anion exchange chromatography. Vagocin was shown to have an anti-HIV-1 EC50 of 4.4 nM in whole-cell anti-HIV assays. Additional anti-HIV screening of vagocin using the TzmBl assay system, performed with our collaborator ImQuest Biosciences, showed that the protein had activity against several clades of HIV-1 in the mid- to low-nanomolar range, with clade C being the most sensitive. Vagocin also inhibited cell-to-cell transmission of HIV and was found to be synergistic with the anti-HIV monoclonal antibody b12 and to a lesser extent with GRFT. We have produced rabbit polyclonal antibodies to vagocin which we will use to further define its binding interactions.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
Application #
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Basic Sciences
Zip Code
Mitchell, Carter A; Ramessar, Koreen; O'Keefe, Barry R (2017) Antiviral lectins: Selective inhibitors of viral entry. Antiviral Res 142:37-54
Woodrum, Brian W; Maxwell, Jason; Allen, Denysia M et al. (2016) A Designed ""Nested"" Dimer of Cyanovirin-N Increases Antiviral Activity. Viruses 8:
Vamvaka, Evangelia; Arcalis, Elsa; Ramessar, Koreen et al. (2016) Rice endosperm is cost-effective for the production of recombinant griffithsin with potent activity against HIV. Plant Biotechnol J 14:1427-37
Vamvaka, E; Evans, A; Ramessar, K et al. (2016) Cyanovirin-N produced in rice endosperm offers effective pre-exposure prophylaxis against HIV-1BaL infection in vitro. Plant Cell Rep 35:1309-19
Moulaei, Tinoush; Alexandre, Kabamba B; Shenoy, Shilpa R et al. (2015) Griffithsin tandemers: flexible and potent lectin inhibitors of the human immunodeficiency virus. Retrovirology 12:6
Garrison, Aura R; Giomarelli, Barbara G; Lear-Rooney, Calli M et al. (2014) The cyanobacterial lectin scytovirin displays potent in vitro and in vivo activity against Zaire Ebola virus. Antiviral Res 112:1-7
Barton, Christopher; Kouokam, J Calvin; Lasnik, Amanda B et al. (2014) Activity of and effect of subcutaneous treatment with the broad-spectrum antiviral lectin griffithsin in two laboratory rodent models. Antimicrob Agents Chemother 58:120-7