The body’s immune response to fungal infections changes when the individual is also infected by a virus, according to a study which examines the interaction of the two types of infection.
Researchers at the University of Birmingham, UK, The Pirbright Institute and University College London, UK, say they have uncovered new information about the immune system’s ability to deal with co-infection.
Although it is understood how the immune system responds to each of these pathogens, it is not known what happens when both types occur together, the researchers say.
White blood cells attack pathogens through phagocytosis, but in fungal infections, the process can reverse, ejecting the fungus back out of the white blood cell via vomocytosis.
This new study, published in the latest edition of PLOS Pathogens, the researchers established that the process of expulsion is accelerated when the white blood cell detects a virus.
The research team used advanced microscopy techniques to study live white blood cells exposed to two different types of virus – HIV, and measles – as well as Cryptococcus neoformans, a fungal pathogen that is particularly deadly among HIV+ patients.
The researchers found that white blood cells began expelling the fungal cells quicker, rather than becoming simply less able to deal with the fungus.
Lead author, Professor Robin May, director of the Institute of Microbiology and Infection at the University of Birmingham, said: “We found the macrophages ejected their prey – the fungal cells – much more quickly when the virus was present. This was very unexpected but could be an attempt to ‘free up’ those white blood cells to deal with the new viral invaders.”
Because the vomocytosis occurred with both viruses, the team believed the effect was likely to be a general response to viral co-infection.
“This is the first time that scientists have studied our immune system’s response to fungal infection in the much more realistic setting of a secondary (viral) infection,” said Professor May.
“We don’t yet know whether this mechanism makes the white blood cells more or less effective in fighting off either infection. Although expelling the fungal cell will free up the macrophage to attack the virus, it also sets free the fungal cell to continue its spread through the body.”
Dr Dalan Bailey, head of the viral glycoproteins group at Pirbright, added: “This is another interesting example of transkingdom interactions between microbes, this time fungi and viruses. We are only beginning to understand the complexity of microbe interactions within the host, and this collaboration sheds new light on this exciting new area of research.”
May et al. Viral infection triggers interferon-induced expulsion of live Cryptococcus neoformans by macrophages. PLOS Pathogens 27 February 2020.
Leave a Reply