Tuesday, 8 November 2011

Aspergillus Catches a Cold

Can Aspergillus catch the equivalent of 'flu? Apparently it can as reported in a new paper published recently.  Several Aspergillus fumigatus isolates have been shown to be infected with mycovirus. They were 'cured' of infection and then re-infected to prove that there was a virus passing between the different isolates. Once 'cured' the fungus had a different growth rate and appearance. When re-infected they took on the same appearance that they had had prior to 'curing'.

On left - 'cured'           On right virally infected

Interestingly those isolates that were infected showed a number of physical changes including poorer growth - they grew less well in several different types of growth media, so this suggests that the virus disables the fungus to some extent.

We know that mycovirus' cannot infect humans so perhaps here is a potential route for treatment of people with chronic infections by Aspergillus fumigatus? One thought is that if we could use these viruses to infect the fungus growing in the lungs or sinus' of people living with aspergillosis then we might be able to reduce the pathogenicity or virulence of the resident fungus with little damage to the host? This may help us resist the infection.

Another possibility is to genetically engineer a mycovirus so as to make it a deadly agent we could use against the fungus. The virus can only infect the fungus so the toxin would only be present in the fungus and not in the surrounding tissues of the human host - this is particularly attractive in the case of fungi that have become resistant to antifungal drugs as there is no known resistance in fungi to mycovirus infection and it would represent the opening of a whole new route of attack against the fungus.

Does this sounds a bit unlikely? Not really. In fact there are already extensive research efforts underway to do precisely this and to try to selectively transport antifungal toxins into fungi using mycovirus - see van de Sande et. al. 2011. Who knows? perhaps using a natural pathogen of fungi will help us overcome many of their defences, reduce our exposure to toxic drugs and act as the 'magic bullet' of the future to help us fight off these insidious invaders.

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