Readers comment on TB vaccines and more

Cellular hideout

Delivering a tuberculosis vaccine intravenously instead of under the skin improved its effectiveness, Tara Haelle reported in “Injecting a TB vaccine into the blood, not the skin, boosts its effectiveness” (SN: 2/1/20, p. 12). 

“My main takeaway from this article is that something as big as bacteria can get inside of a cell,” reader Mike Hamm wrote. The article states that the bacteria that cause tuberculosis enter cells, but bacteria are typically much larger than viruses that infect cells, he noted. “So how does something as big as bacteria get through?”

Once in the lungs, TB bacteria infect cells called macrophages. These immune cells are part of the body’s first line of defense against invaders. Macrophages typically swallow pathogens and destroy them in compartments called vacuoles, says epidemiologist Tara Smith of Kent State University in Ohio. 

TB bacteria are swallowed by macrophages but aren’t so easily destroyed. “Scientists are still trying to understand how TB bacteria manage to escape their death sentence,” Haelle says. It’s possible the bacteria trick macrophages into releasing a protein that reduces the cells’ ability to fight infection.

Once TB bacteria escape death, they become executioners, somehow breaking up their macrophage prisons from within, Haelle says. Other types of cells rush to clean up the mess, forming clumps around the bacteria and macrophage debris. TB bacteria can live inside the clumps, which appear as lesions on the lungs, or break free to cause new infections. 

Team effort

In his book The Crowd and the Cosmos, astrophysicist Chris Lintott applauds the work of citizen scientists, Erin Wayman wrote in her review, which was headlined “An astrophysicist honors citizen scientists in the age of big data (SN: 2/1/20, p. 29).

The book review sparked warm memories for reader Keith Greiner. “I recall that my father, who graduated with a master’s in chemistry in the 1930s, continued to contribute to his community as a scientist … up until he passed away at the age of 108. I learned much from his postretirement investigations,” Greiner wrote. He suggested that Science News report on how nonscientists can apply science in their lives. “Such an article would say to young readers, ‘Even though your life may turn in many directions, your interest in science and mathematics can continue to grow.’ ”