funding: war of the viruses

2 May 2005

A new study of interactions between two sheep retroviruses could suggest novel ways to tackle viruses such as HIV.

Professor Massimo Palmarini at the University of Glasgow has been awarded an £800 000 programme grant to study an unusual mechanism of 'retroviral interference'. The sheep genome, like all animal genomes, contains benign 'endogenous retroviruses': formerly free-living viruses that have permanently integrated their DNA into the host genome. One such retrovirus interacts with an externally acquired retrovirus, preventing the latter causing disease.

The acquired virus, Jaagsiekte sheep retrovirus (JSRV), is responsible for ovine pulmonary adenocarcinoma, an important disease of sheep. The sheep genome contains around 20 copies of related endogenous retroviruses, one of which interferes with JSRV replication. It prevents JSRV viral particles from 'budding', or exiting, from the cell membrane after they have been assembled inside the cell.

The crucial factor appears to be the virus's Gag protein – part of the core of the virus particle. The endogenous retrovirus produces a defective Gag protein, which not only prevents the endogenous virus spreading but also blocks the spread of JSRV. The interference is particularly interesting as it occurs at a later stage in the replication cycle than other naturally acting factors or antiretroviral drugs.

Over the next five years, Professor Palmarini and his team aim to analyse this mechanism in more detail. As well as shedding light on how retroviral particles reach the cell membrane, the work could highlight new ways to inhibit retrovirus spread.