“Those glowing parts you see there,” said Sarah, leaning in toward the monitor and using her pen as a pointer. “Those are antibodies, thousands of miniscule immunoglobulins, each labeled with a tiny fluorescent protein. They are the mouse defense system, so they float around in the blood, watching out for any trouble. They seem to have found it so they are attaching to the foreign particle that is threatening the mouse. In this case, their enemy is the Laptev virus,” she said, moving the pen to trace a large ovoid shape, the virus, at the center of a gleaming halo.
“But I can’t really distinguish anything. It’s all just a spiky glowing mass around the virus,” answered Angela.
Drew nodded. “Antibodies are too small to be observed under the microscope. And sometimes many antibodies will link together, forming complexes.” He switched to another screen which had a schematic drawing of antibodies attaching to an antigen. “The ‘Y’ shaped antibodies become attached to each other by the base of the ‘Y’, and the arms of the ‘Y’ stick out so as to capture the foreign particle, which is called the antigen, that they’re seeking. Of course, like I just said, all of that’s way too small for us to observe directly. That’s why scientists came up with the idea of attaching markers, labels, to the antibodies.”
“When the immunoglobulins link into a single complex, it’s like putting several daggers together by their hilts and throwing them at the enemy,” said Shane, and everyone turned to him. “Except each dagger has two blades instead of one. As soon as the enemy is stabbed, it becomes labeled. So it’s like it has this big flag on it. So now other factors in the blood see the flag and they signal for the white blood cells, the big bad blood thugs, to come and ‘beat up’ the offending virus or particle by ingesting it, entombing it in a vacuole, and mercilessly exposing it to lysozyme, a noxious enzyme that breaks down and dissolves almost any viable molecule.”
“That’s… a good way to explain it,” said Sarah, more than a bit surprised that Shane had actually contributed something worthwhile, even if his description had been rather unorthodox.
“So in these mice we can see that there are some antibodies in their blood,” Tally said, “but the number is not high enough to stem a viral infection the way we see happening here in this ELISA.”
“Before we go any further,” said Angela, “can anyone tell me where scientists got a protein that glows in the dark? Did they, like, steal it from lightning bugs or something?” She smirked as if her question was outlandish.
“That’s exactly what they did,” said Sarah. “They cloned the genes responsible for the glowing. Now they also use genes from bioluminescent protozoa as well.”
Angela’s eyes widened with surprise and then, as if to cover her embarrassment, she quickly turned to Tally. “Please go on, you were saying?”
“Okay, so clearly we have the mouse’s immune system attacking the virus, but that’s not at all that’s going on here. It’s almost as if… well, no. I can’t rightly say. It just seems like…”
“Like what?” asked Sarah, almost holding her breath. She was really hoping that another of the researchers would come to the same conclusion that she had.
Tally shook her head. All eyes were focused on her now, and the lab was quiet, waiting for her to finish her thought. “If I didn’t know better,” she said, spreading her words out as she thought, “I would say that instead of the mouse’s host defense system coming to the rescue, it was an entirely different particle which was attacking the virus.”
Sarah raised an eyebrow. Everyone watched mesmerized as Tally showed them some more slides in which the viral particle could be seen being engulfed by a much larger dark spot. It reminded Sarah of the first video games she had played as a child, where the Pacman, that smiley face turned profile, had swallowed those little balls.
“Whoa, what is that? It’s way too big to be a part of the blood that we’ve never seen before,” said Emile.
“I know,” said Tally. “It definitely should not be there.”
“But, we have seen it before,” said Sarah. She waited until she had everyone’s attention and then she clicked to the brain cell slides with the purple dots.
“Toxoplasmosis?” asked Drew, incredulously. “But it was in the brain cells. Now you’re saying it’s in the blood too?”
“I think so,” said Sarah.
“I don’t understand,” said Rhonda. “Are you saying that the Toxoplasmosis is somehow protecting the mice?”
“I know it sounds improbable,” said Sarah, “but it’s what the results are showing us. Somehow the Toxoplasmosis infection is protecting the mice from Laptev HFV.”
“That’s crazy!” said Shane. “Why would that happen? One’s a primitive virus and the other is so much more evolutionarily advanced. The two have nothing in common. How would the Toxoplasmosis even know to attack the virus?”
“I never thought I’d say this,” said Tally, “but I agree with Shane.”
“And I’m totally lost again,” said Angela, clearly frustrated.
Sarah held her hands up in a placating manner. “I could be wrong, I admit, it’s just a hypothesis, but work with me here. Toxoplasmosis was the established infection in our C12 mice, right? We don’t know for sure how long these mice have been infected, but they looked healthy and acted normally when we began the experiments, right? So that means we can assume that Toxoplasmosis knows its host and the two are fairly copacetic…”
“Inasmuch as a parasite can be copacetic with the organism it is feeding on!” said Tally.
“Yes, you’re right. Still, the two of them are fine, living in relative peace, when all of a sudden, in waltzes Laptev, the third wheel. Toxoplasmosis dude is not up to sharing, so he kicks Laptev in the butt. Totally gets rid of him,” Sarah said.
Emile crossed his arms and gave her a skeptical look.
“You guys have heard of this happening before, right?” said Sarah, her eyes shining with excitement. “I remember studying a case like this in a Parasitology class I took a long time ago. There was a type of acacia tree whose sap was particularly appealing to a certain type of ant which crawled up and down the trunk feeding on the sap that the tree produced. The tree and the ants had a symbiotic relationship. When, however, the tree was threatened by, say, a giraffe or an antelope, which decided to feast on some of the tree’s tender leaves, the ants would rush to the invader and pierce its tongue with their fiery venom, and the giraffes were soon dissuaded from making a meal of these leaves. In that manner, the ants were parasitizing an organism, the tree, which in turn they protected from another invasion by the giraffe.”
Drew and Rhonda nodded but everyone else still looked doubtful.
“I think it’s possible that this is a similar situation. In this case, this little Toxoplasmosis was doing the same thing that the ants did. It was protecting its host from harm by this attacking virus,” said Sarah.
Angela shook her head and blew out a long breath. “Well, if that doesn’t beat all.”
“Do people get Toxoplasmosis infections?” asked Miquela.
“Actually, they do,” said Sarah.
Everyone was silent for another moment while they digested this fact.
“Do you think, I mean, is it possible that some of the people who survived the Laptev infection in the Arctic could have had a Toxoplasmosis infection?” asked Tally.
“That’s the million dollar question, isn’t it?” said Sarah, now beaming.
“I’m on it right now,” said Angela. “I’ll have everyone who survived tested and I’ll let you know the results at the next meeting.”