Harvesting Blood From Limpets for a Cancer Vaccine

Using a California snail to treat Alzheimer’s and autoimmune diseases

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This segment is part of the IEEE Spectrum series “The New Medicine

Susan Hassler: Sometimes new medical technology comes from very unexpected places. In Southern California, researchers have found a way to grow an unusual marine snail that may play a major role in the vaccines of the future. Lauren Sommer went to explore this unique laboratory site.

Lauren Sommer: When you think of cancer treatment, this probably isn’t the scene you’d imagine. But this rocky strip of land in Port Hueneme in Southern California is home to a unique medical facility.

Brandon Lincicum: So, what you’re seeing right now is—this is our primary production seawater system. Essentially, we pump nutrient-rich seawater right over here from the port.

Lauren Sommer: Brandon Lincicum is the aquaculture manager for Stellar Biotechnologies. We’re standing next to large tanks just a stone’s throw from the Pacific Ocean.

Brandon Lincicum: Take a look at some of these guys. Okay, so, this is what you’ve been waiting to see. This is Megathura crenulata right here, the giant keyhole limpet.

Lauren Sommer: Lincicum reaches into the tank and pulls out a round, purplish animal that looks like an abalone.

Brandon Lincicum: They do have a hard shell, but they have this mantle tissue that they can fold up over their shell so you know, when you touch these guys, they are almost soft. It’s almost...

Lauren Sommer: A little slimy.

Brandon Lincicum: A little slimy? Right? A little bit.

Lauren Sommer: The limpet he’s holding weighs almost a pound, but it takes years for them to grow this large.

Brandon Lincicum: So I’ll show you some of our up-and-coming limpets right here. So, if we take a look in this tank, these are our limpets, and these guys are fairly slow growing, but you can see them. These guys are about three and a half years old or so. We produce these guys from sperm and egg—microscopic sperm and egg. These guys are teeny tiny.

Lauren Sommer: This is the only place in the world where giant keyhole limpets are bred and grown. And there are thousands here, each with their own unique tracking number. The question is, why?

Frank Oakes: It pretty much is a nondescript member of the local California coastal environment but turns out to be really important when it comes to medical technology.

Lauren Sommer: Frank Oakes is the CEO of Stellar Biotechnologies. He says what’s special about giant keyhole limpets is their blood—or more specifically, something found in their blood called KLH.

Frank Oakes: Keyhole limpet hemocyanin. And then, hemocyanin is the protein from the blood, analogous to hemoglobin in humans.

Lauren Sommer: This unique blood protein, KLH, has been studied since the 1950s, and it’s played a major role in immune system research. But the keyhole limpet is only found in Southern California, which means there’s a limited supply.

Frank Oakes: It was harvested routinely for extraction of its blood, and with little regard to understanding the animal, its importance in the wild, or the perishability of the wild population.

Lauren Sommer: Oakes has a background in aquaculture, so he began studying how to breed limpets in captivity.

Frank Oakes: In the late 1990s, we started work on developing nonlethal extraction methods for the animal, so we can take the blood without killing them.

Lauren Sommer: Getting limpets to grow in captivity was no easy task. Oakes had to learn how to coax them into reproducing. He had to learn what conditions they grow best in. And because the limpets are part of medical research, there has to be strict quality control to prevent contamination. Today, thousands of limpets go through their entire life cycle in a controlled system, giving blood several times a year.

Frank Oakes: From a 50-animal lot, we get about a liter of serum. And from that liter of serum, we will typically produce about 20 grams of protein. And at retail value, that 20 grams of protein for us is approximately $100 000.

Lauren Sommer: Why would a blood protein be so valuable?

Herb Chow: Without it, a lot of the vaccines will not work.

Lauren Sommer: Herb Chow is a vice president at Stellar Biotechnologies. He says to understand why KLH is useful, you have to go back to the early days of vaccines. Medical researchers would take something harmful like a virus, kill it, and then inject it into your body. Your immune system would see the inactive virus and it would learn how to attack it.

Herb Chow: Except if you use the dead virus or that bacteria, it does accomplish that activation or stimulation, but it comes with a price. The price is some level of toxicities: People get sick because the toxin is still there.

Lauren Sommer: So researchers took viruses apart, pulling off the small chunks that your immune system could attack. They injected those smaller pieces as the vaccine, but there was a problem.

Herb Chow: Just too small. They don’t see it. So it becomes stealth to your immune system.

Lauren Sommer: And like a stealth plane, if your body doesn’t see it, it can’t learn to attack it. But attach those virus pieces to KLH, and it’s like attaching reflectors to the plane.

Herb Chow: By putting two together, all of a sudden the radar starts seeing it.

Lauren Sommer: And your immune system mounts an attack or starts making antibodies. KLH itself is neutral and doesn’t harm you. Chow says it’s being used in vaccine research for Alzheimer’s and autoimmune diseases. It’s also being used in cancer vaccine research.

Herb Chow: The problem with the cancer cells is a lot of the antigen that are expressed on the cancers is actually your own tissues. The body sees them: This is my own, I shouldn’t react to it.

Lauren Sommer: Cancer cells are, in essence, your own cells. So your immune system doesn’t see them as foreign invaders.

Herb Chow: And, as such, it fools your immune system to kind of ignore them and let them keep growing. And when the tumor mass gets to be a certain size, then your body no longer be able to handle it.

Lauren Sommer: So doctors use treatments like radiation and chemotherapy, which target all fast-growing cells in your body. But Chow says that’s why cancer vaccines have such promise.

Herb Chow: It’s something that it’s high on the radar screen because of the characteristics—that they can differentiate the normal cells from the tumor cells and be able to target the treatments to the tumors.

Lauren Sommer: Cancer vaccines could train your body to only attack the cancer cells. Chow says the challenge is finding something on cancer cells that would help your immune system differentiate them from your own cells.

Herb Chow: And there are differences, and it used to be we are looking at differences on the cell surface, and it seems like that difference is not big enough. There are some differences, now we’re going inside the cells, looking a lot—zillions of molecules inside the cells—and you find more differences.

Lauren Sommer: Today, most of the cancer vaccines that use KLH are still in the research phase or in clinical trials. But CEO Frank Oakes says the role of KLH is looking promising.

Frank Oakes: The long-term commercial demand for KLH looks very promising because it’s a key ingredient in a wide variety of drugs that are currently in clinical development.

Lauren Sommer: The challenge is that vaccines take decades to develop—and not all of them come to market.

Frank Oakes: Unfortunately, in this business, more drugs fail in clinical development than succeed.

Lauren Sommer: But Oakes says with the growth in cancer vaccine research, there’s a good chance that this mollusk from Southern California will eventually play a role in keeping us healthy. In Point Hueneme, I’m Lauren Sommer.

Photo: Lauren Sommer

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