Frozen cells reveal a clue for a vaccine to block the deadly TB bug
STEVE INSKEEP, HOST:
The pandemic helped to speed the development of a new class of vaccines - the mRNA shots against COVID made by Pfizer and Moderna. Now, scientists hope to create mRNA vaccines against other diseases for which traditional vaccines have not worked. NPR's Nurith Aizenman traveled to the University of Cape Town in South Africa, where they report a breakthrough against tuberculosis.
NURITH AIZENMAN, BYLINE: MRNA vaccines are like a plug-and-play system. If you know what proteins on a virus or bacterium a person's immune system can latch onto to kill it, you insert the genetic code for those proteins into the vaccine. But when it comes to the tuberculosis bacteria - TB for short - figuring out what those target proteins should be is tricky.
MUNYARADZI MUSVOSVI: TB is quite a complex bug.
AIZENMAN: That's Munyaradzi Musvosvi, one of the researchers behind this breakthrough.
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AIZENMAN: And he's about to show me the key to it.
MUSVOSVI: So, yeah, here would be the cells in liquid nitrogen. So we keep them...
AIZENMAN: I'm looking at some enormous metal vats.
MUSVOSVI: Cryo-tanks, yeah. Yeah, liquid nitrogen tanks.
AIZENMAN: Inside are a set of frozen blood samples collected from about 6,000 South African high school students starting decades ago.
MUSVOSVI: Yeah, essentially cryo-preserved. They were kept nicely frozen.
AIZENMAN: Can I take a peek?
MUSVOSVI: Yeah, I think...
AIZENMAN: As he pulls off the lid, plumes of white vapor clouds spill out.
MUSVOSVI: It's kind of hazy, but you just might be able to see a little box there.
AIZENMAN: These samples were originally collected for some other studies. Then the leftovers just sat here.
MUSVOSVI: Yeah, quite a long time. Almost 12 years.
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AIZENMAN: Back in his office, Musvosvi explains how this all came together. Tuberculosis kills more people around the world than any infectious disease other than COVID. And in South Africa, a lot of people get exposed to TB, but only a fraction of them actually develop the disease. So when the researchers analyzed the first set of samples taken from those South African high schoolers...
MUSVOSVI: Some of these adolescents had an immune response that indicated that they'd been exposed to TB.
AIZENMAN: ...Even though they hadn't gotten sick. But it can take months after exposure to develop TB, so researchers continued to collect samples from these students for the next two years.
MUSVOSVI: So as we followed them up, we actually could document that some of these adolescents were diagnosed with active TB disease.
AIZENMAN: They had symptoms.
MUSVOSVI: They had symptoms, and we could actually measure the bacteria in sputum that they were coughing up.
AIZENMAN: This meant the researchers could separate out the TB-exposed students who ultimately did develop the disease.
MUSVOSVI: So then it allowed us to ask the question, what was different between them and those who managed to control infection during this two-year follow-up?
AIZENMAN: Specifically, were the immune cells - called T cells - of the students who never got sick latching on to a different, presumably more vulnerable part of the TB bacteria?
MUSVOSVI: Trying to see, you know, out of all the proteins that TB makes, what do these T cells recognize?
AIZENMAN: Except scientists didn't have a good way of doing that until 2019, when a Stanford researcher named Huang Huang came up with the technique. And Huang says when the South African researchers immediately proposed teaming up to use it, he was excited.
HUANG HUANG: This is a great opportunity to explore these very precious samples.
AIZENMAN: So they thawed them out and got to work.
MUSVOSVI: Let me just log in here.
AIZENMAN: Musvosvi is pulling up the results on his computer.
MUSVOSVI: So here you can see that so far we've identified three proteins.
AIZENMAN: These are the actual proteins that you're recommending.
MUSVOSVI: Yeah. Yeah.
AIZENMAN: And he says a number of vaccine developers, including the drug company Pfizer, are already testing them out.
Nurith Aizenman, NPR News.
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