NanoViricides Inc. (NNVC)

[KMBJN]

Excellent point - Ebola viruses are first attracted to cells perhaps by lectins and TIM-1 cell surface receptors. Ebola viruses then somehow undergo endocytosis, and within the low-pH environment of the endosome, the viruses are "primed" for fusion by removal of the glycan caps via cathepsins B and L. This exposes the receptor binding region (RBR) of Ebola, allowing interaction of the RBR with host NPC1 receptors on the endosome surface, a step which finally then allows Ebola fusion with the endosome membrane and entry into the cell.

Anyways, Ebola is unusual in that the vital cellular receptor for it, NPC1, occurs on the endosome, inside the cell. Or stated another way, "NPC1 is the first known viral receptor that recognizes its ligand within an intracellular compartment and not at the plasma membrane."

http://www.ncbi.nlm.nih.gov/pubmed/22395071

or as Hoffman-Winkler et al. state in the paper with the figures, "NPC1 is unique in recognizing the filoviral glycoprotein only after uptake into the cell and after proteolytic processing."

This could be a problem if nanoviricides don't go into these intracellular compartments (endosomes).

NNVC always claimed that "we don't go inside the cell," but I always wondered how they know some nanoviricides won't undergo endocytosis and get into the cell. If some EbolaCides enter the endosome with Ebola after the caps are removed and the receptor binding region is exposed, then EbolaCide could perhaps destroy the virus in the endosome, instead of in the blood. It is possible that "destroying" the virus in the endosome might not work as well as destruction in the blood, but I can't imagine why not.

It might be possible that the EbolaCide2 ligand could be designed to attach to the NPC1 receptor binding region, despite the glycan cap, or as Robi-1 said, to include some type of glycan cap removers with EbolaCide2, perhaps?

It's a tricky virus for sure, and it will be interesting to see if EbolaCide2 is able to work by mimicking NPC1 (and binding to the receptor binding region of Ebola - which as you say appears to be capped and only exposed once inside the endosome), instead of whatever they used last time, a ligand that bound to a different part of the GP glycoprotein (perhaps something like TIM-1?) Using this non-specific GP ligand had the effect of "diluting" EbolaCide1 since it also bound the non-infectious sGP "chaff" and not the whole infectious GP-virus. Mimicking NPC1 would avoid the chaff, but would have to get inside and work inside the endosome, instead of the blood like other nanoviricides.

It will be interesting to see how EbolaCide2 works against this difficult to defeat Ebola virus.

Perhaps some other drug will have better luck using some other mechanism - either specific antibodies, or RNA blocking drugs, or chemical inhibition of NPC1, or other ...

Let's hope they find something that works!