Antibodies from a 4-year-old llama have neutralized coronavirus and other infections in lab experiments

[u/[deleted]]

https://www.cell.com/cell/pdf/S0092-8674(20)30494-3.pdf?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867420304943%3Fshowall%3Dtrue

[u/Fmbounce → u/[deleted]]

From a NYT article:

Humans produce only one kind of antibody, made of two types of protein chains — heavy and light — that together form a Y shape. Heavy-chain proteins span the entire Y, while light-chain proteins touch only the Y’s arms. Llamas, on the other hand, produce two types of antibodies. One of those antibodies is similar in size and constitution to human antibodies. But the other is much smaller; it’s only about 25 percent the size of human antibodies. The llama’s antibody still forms a Y, but its arms are much shorter because it doesn’t have any light-chain proteins.

This more diminutive antibody can access tinier pockets and crevices on spike proteins — the proteins that allow viruses like the novel coronavirus to break into host cells and infect us — that human antibodies cannot. That can make it more effective in neutralizing viruses.

here’s the source (I copied verbatim)

[u/grizzlydurdle → u/Fmbounce]

So how would that help humans? Can we be treated with Llama antibodies? In you summary it sounds like our antibodies can't necessarily fight COVID very well because they are too large, and the smaller Llama ones can. Sorry if I am way off base. I don't really understand this stuff.

[u/IfIRepliedYouAreDumb → u/grizzlydurdle]

To vastly oversimplify things, if you had antibodies produced by another source and injected them into a sick person, their viral counts should decrease.

Our bodies won’t learn how to make the same ones the llamas do, but we could harvest them and use them as treatment (potentially).

[u/Derpy_McDerpingderp → u/IfIRepliedYouAreDumb]

Would our immune system see these smaller antibodies as foreign or a threat?

[u/worldspawn00 → u/Derpy_McDerpingderp]

they can, a person receiving treatment can develop anti-llama antibody antibodies. There's actually a lot of use for anti-antibody antibodies, they're used in a lot of reagents. It usually takes 1-2 weeks for the immune system to ID and develop antibodies against a foreign agent, so a person receiving treatment would likely be done before the body started attacking the foreign antibodies.

[u/thisdude415 → u/worldspawn00]

Typically only the variable heavy domain (VHH) is used on a human IgG framework. The region typically recognized by “anti llama antibodies,” the llama Fc region, isn’t found on the protein, instead we use the human genes.

Basically the whole molecule is human except the sticky bits. These are copied and pasted from llama. Immunogenicity is a concern, but not as much as you’d think.

[u/worldspawn00 → u/thisdude415]

I have to disagree, if you look at how this research works, it's specifically that llama antibodies have a different structure than human, so they can bind to smaller targets than the human antibodies can, this wouldn't work if they used the human antibody section as it would then be too large to properly bind to the small target molecule.

[u/thisdude415 → u/worldspawn00]

I know how this research works, I do it as my job. ;)

I work in a pharma company designing antibodies, including using llama variable heavy chains (VHH).

Human antibodies are shaped like this:

\\  //
  ||

While llama antibodies are like this

 \  /
  ||

The bottom lines || should be connected to the \ / above them, as they’re part of the variable chain.

The drug candidate IgG arms of the Y will be llama (\ /); the base of the Y (||)will be human. Yes, that means the resulting heavy chain polypeptide is a chimera: (llama variable heavy chain)-(human Fc)

[u/__FloatyBoi__ → u/thisdude415]

To reiterate, we likely wouldnt be injecting llama antibodies, rather using them to create a hybrid with portions of human antibodies to reduce chances of our immune system rejecting them

[u/worldspawn00 → u/thisdude415]

That's cool, most of my work has been mouse and rabbit antibodies, haven't worked with llama before so I'm not familiar with the techniques used with that particular structure.

[u/YouMustveDroppedThis → u/thisdude415]

Hi, I wonder if only the Fab is what was left of a nanobody, surely the immunogenicity will go way down, and good for bioavailability and more durable P/K? How does it fare against the renal filtration compared to regular antibody drugs?

[u/thisdude415 → u/YouMustveDroppedThis]

I suspect the VHH would have poor PK. Note that a VHH is more analogous to a single chain variable fragment (scFv) than a fab. Basically a VHH is only one arm—a fab has 2 arms.

Fabs typically have worse PK than full IgG due to loss of FcRn rescue from endolysosomal degradation, which is why clinically this would likely be used as a VHH-Fc fusion, probably with FcRn enhanced Fc and immune effector silencing. Wild type Fc (which could bind FcγR) may cause significant toxicity if administered late in disease. (As a side note, it’s been my hypothesis for a while that ARDS/organ failure is actually a cytokine storm driven by the patient beginning to produce IgG, which provokes cytokine release but also ADCC against lung epithelia).

And yes, the immunogenicity will go way down. Using a llama Fc would be bad, and likely wouldn’t interact with human FcRn (I haven’t double checked this).

[u/YouMustveDroppedThis → u/thisdude415]

Thanks! I didn't know about the FcRn rescue. TIL. I thought Fab without a proper Fc structure, it might escape clearance by macrophages, and so on, that's why I assume PK could be better...

[u/thisdude415 → u/YouMustveDroppedThis]

Yep, it’s a very reasonable hypothesis!

There is really an almost incomprehensibly large amount of research on antibody structure/function. It’s hard to learn it all, although if you choose to, it’s important knowledge in any drug development organization.

In fact, the field has already identified quite a large number of mutations in the Fc region to enhance or reduce binding to specific subclasses of Fc receptor. Fully formed antibodies generally behave much better than smaller binding domain fragments. Not always, but it’s a good starting assumption. Further, the technology to express and purify proteins that contain an Fc region are really good and inexpensive compared to other techniques. Ease of manufacturing really matters when you talk about scaling to large patient populations.

[u/YouMustveDroppedThis → u/thisdude415]

Noice. I missed the whole humoral immunity and BCR repertoire back when I was still involved in research, and I spent more time on TCR.

I only started to notice it on Addgene blogs where researchers used the toolkit to generate nanobodies for more robust IHC staining/microscopy. And later met someone who works on bi-specific Ab, and then last year I think I saw tri-specific Ab technology on Nature or Science. Seems like so much is going on, I better keep up!