Assessment of development of resistance to neuraminidase inhibitors in A (H5N1) influenza viruses using a ferret model [ 2006 - 2007 ]

Research Grant

Researchers: Prof Lorena Brown (Principal investigator) ,  A/Pr Aeron Hurt ,  Dr Deborah Middleton ,  Dr Ian Barr ,  Mr Paul Selleck

Brief description The neuraminidase (NA) inhibitors are considered the most effective anti-influenza drugs available for both prevention and treatment of influenza virus infection including A(H5N1) viruses. The drugs are effective against all subtypes of influenza A, making them ideal for use in the early months of a pandemic prior to an appropriate vaccine being produced. As a result many countries around the world, including Australia, have stockpiled these drugs (mainly Tamiflu) as part of their pandemic preparedness plans. However, of concern is the increasing number of recent reports of a higher than expected level of resistance in epidemic influenza being generated against these drugs. A recent isolation of an H5N1 virus from a Vietnamese girl highlights that these viruses can also be resistant to Tamiflu. Within Australia, Tamiflu will be a critical weapon against the initial wave of an influenza pandemic, therefore it is vital that more is known about the propensity of the H5N1 virus to generate resistance, and possibly make these drugs clinically less effective. The aim of the project is to determine the levels, mode and type of resistance that may occur when ferrets are experimentally infected with HP A(H5N1) virus and then treated with NA inhibitors drugs such as Tamiflu. In the event of resistant viruses being isolated following drug pressure from Tamiflu, the strains will then be tested for their sensitivity to the other NA inhibitor drugs Relenza (zanamivir) or the peramivir (a third currently unlicensed NA inhibitor). The results from this cross resistance work will allow strategies to be put into place regarding the administration of an alternative NA inhibitor in the event of a pandemic virus acquiring particular NA mutations which may for example result in Tamiflu resistance. To determine the relative human risk of a NA inhibitor resistant A(H5N1) virus, studies to determine how infectious or transmissible the viruses are would be performed on all resistant strains isolated. NA inhibitor resistant strains demonstrate varying degrees of transmissibility and fitness, therefore it would be beneficial to classify this for any strains generated from this study so as to be in a better position to understand the public health implications if a particular resistant strain was to arise.

Funding Amount $AUD 165,546.23

Funding Scheme NHMRC Strategic Awards

Notes Urgent Research - Pandemic Influenza - H5N1