The Petri Dish: NU professor hopes yeast is the key to managing HIV treatment

    Bad news for pre-meds: It turns out that yeast, the stuff you use to bake bread and make wine, can do some of the clinical chemistry on which you’ve spent your entire college career.

    Blame Keith Tyo. Tyo is a professor of chemical and biological engineering in McCormick, and his lab is one of the many at Northwestern that focuses on synthetic biology, a field of study that genetically manipulates cells to perform useful functions. Tyo’s project engineers yeast to help HIV patients in developing countries monitor their progress.

    “I’ve always been passionate about serving the poor and thinking about how I can utilize the talents I have to do that,” he said.

    In his lab, this humanitarianism takes the form of providing cheap access to crucial health information. HIV patients should ideally be tested multiple times every year to determine how their treatment is progressing. Unfortunately, this often isn’t possible in sub-Saharan Africa.

    “At the end of the day we want to make something that looks like a pregnancy test that people can use in the privacy of their own home where they have access to information that in the United States would only be available if you went to a first class teaching hospital,” he said. “We’re basically teaching this yeast cell to do all of these things that technicians can do using very very expensive equipment.”

    This is achieved by engineering yeast to detect CD4 protein, a part of the immune system that is attacked by HIV. The lab is able to manipulate these tiny animals through a process called directed evolution. In directed evolution, researchers introduce a variety of mutations into the protein within the yeast that is responsible for sensing the CD4 protein.

    These mutations can vary wildly in effectiveness; some will do nothing at all. The researchers also engineer correct sensing to activate another fluorescent protein, so that those with working mutations can be detected. During the screening process, the glowing yeast cells, the same ones detecting CD4 protein, are picked out of the bunch and investigated for their sensing properties.

    Sounds benign, right? Not everyone is convinced. News media and science fiction have transformed genetic engineering into a cultural boogeyman, raising serious concerns about the ethics of altering naturally evolved life forms.

    One of those concerned is Mark Sheldon, Distinguished Senior Lecturer in Philosophy and also in the Medical Ethics and Humanities Program. He compared yeast to apples, in that both evolved naturally the way they did for a reason.

    “The apples that are out there exist in response to the challenges that the species faced in developing. They evolved in such a way that they did a pretty good job of holding on,” he said. “And then we come along with different ideas of what standards to put in place.”

    Sheldon also raises concerns with the ethics of allowing people to have such sensitive and possibly devastating information about their health at their fingertips. In the past, at-home HIV testing has been argued against as being too traumatic.

    “Pregnancy can be devastating as well but often it’s great happy news that one is pregnant,” Sheldon said. “There’s never going to be great happy news when one is HIV positive and to the extent that people still regard it as a death sentence. And depending on the society where this is available it could be a death sentence.”

    However, Tyo said he believes he is developing an ethically sound, vitally important product. Synthetic biology, he said, can be used for both bad and good, much like a hammer. While you can build a home with it, you can also use it to hit someone.

    “Really the fundamental challenge is not to engineer the hammer so it can’t hit someone on the head but to make sure education of the people who operate that hammer know how to use it wisely,” he said.


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