A mouse study by researchers at the University of Illinois College of Veterinary Medicine demonstrated that a specific type of T cell produces cytokines that are necessary for the body to acquire immunity against fungal pathogens. Their findings could pave the way for developing novel, effective fungal vaccines.

The study, “GM-CSF+ Tc17 cells are required to bolster vaccine immunity against lethal fungal pneumonia without causing overt pathology,” is published in Cell Reports.

“GM-CSF co-expressing T17 cells instigate pathologic inflammation during autoimmune disorders, but their function in immunity to infections is unclear,” wrote the researchers. “Here, we demonstrate the role of GM-CSF+ Tc17 cells for vaccine immunity against lethal fungal pneumonia and the cytokine requirements for their induction and memory homeostasis.”

“A particular type of T cell [TH17 cells] that expresses GM-CSF [granulocyte-macrophage colony-stimulating factor] was linked to greater severity of illness in people infected with the virus that causes COVID-19,” said Som Nanjappa, PhD, an assistant professor of immunology at the University of Illinois.

“Our study shows that IL-17A+ CD8+ T cell (Tc17), which also expresses GM-CSF, is necessary for mediating fungal vaccine immunity without instigating hyperinflammation. So clearly, the antigen specificity of T cells—whether they target viral vs. fungal or bacterial pathogens—has a huge impact on whether they play a protective or detrimental role.”

Colonies of mice were given an experimental fungal vaccine. The mice were then exposed to a virulent fungal pathogen to cause lethal pulmonary infection. Researchers could then determine the necessity of GM-CSF+ Tc17 cells to mediate vaccine immunity.

“Our study reveals the beneficial, nonpathological role of GM-CSF+ Tc17 cells during fungal vaccine immunity,” concluded the researchers.

“In line with this, we have identified a functional phenotypic marker that could be targeted to enhance this subset to augment vaccine efficacy,” said Nanjappa. He recently received NIH-R01 funding to pursue this strategy for a fungal vaccine.

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