How a rare pathogen could infect the healthiest of people

A unique evolutionary trait in a rare pathogen called Cryptococcus gattii allows it to infect even the healthiest of hosts through a mechanism that neutralises the body's immune response against it, a study showed.

Scientists at the University of Birmingham have explained how this pathogen responds to the human immune response and triggers a 'division of labour' in its invading cells, which can lead to life-threatening infections.

The pathogen, once inhaled, can spread through the body to cause pneumonia or meningitis, the study showed.

"By understanding how this particular lineage behaves once in the body, we have provided an insight into the key mystery of why it is virulent in immunocompetent people - that is those with a strong immune system," said professor Robin May from the University of Birmingham.

When invaded by an outbreak strain, the host body creates reactive oxygen species (ROS) which form an essential part of the antimicrobial defence in mammals.

ROS works to prevent the spread of harmful pathogens by cleansing the body of invasive cells.

A strong ROS reaction usually makes people less susceptible to infections, but in the case of Cryptococcus gattii just the opposite is true as the fungus uses this reaction to its own benefit.

The pathogen uses the release of ROS as a signal to trigger a 'division of labour' in the intracellular fungal population, showed the study.

"Cryptococcus gattii displays unique traits and has adapted to new environments in such a way that it presents us with a chance to make huge strides in understanding how these pathogens operate and, hopefully, make sure we are a well prepared to deal with future outbreaks," concluded May.

The study appeared in the journal Nature Communications.