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Infections with the human T-cell lymphotropic virus type-1’s (HTLV-1) are considered to be inconsequential in most cases, but Melbourne researchers now determined that in every infected person this virus causes insidious lifelong damage to normal immune function.

Publishing their findings in The Lancet Infectious Diseases, the team from the Peter Doherty Institute for Infection and Immunity (Doherty Institute) reviewed the strategies employed by HTLV-1 to maintain persistent lifelong infection, while still causing pathogenesis in the host. 

They discovered that HTLV-1 maintains a balance between active proliferation and stealthy persistence in infected immune cells, by strategic viral gene expression and altering the host cells themselves.

First author, University of Melbourne’s Ashley Hirons, a PhD student at the Doherty Institute, said that understanding these factors will underpin future developments in effective therapy for, and prevention of, HTLV-1 infection.

“Our research found that HTLV-1 ability to sneak past the immune system while maintaining, or increasing, the viral reservoirs provides an enormous obstacle to treatment and prevention – information that should be considered when developing future strategies,” Miss Hirons said.

HTLV-1 is a complex retrovirus that causes lifelong infection in around 10 million people worldwide. In some communities, such as Indigenous Australians living in remote areas, it affects more than 45 percent of people. 

HTLV-1 infects immune cells and can lead to excess growth stimulation that develops into adult leukemia. Various other conditions arise when virus-activated immune cells cram into confined organs, such as occurs in spinal cord damage from HTLV-1-associated myelopathy–tropical spastic paraparesis (HAM/TSP), eye inflammation (uveitis), enlargement of parts of the airways of the lung (bronchiectasis). Immune deficit from HTVL-1 is also associated with infectious dermatitis, scabies, and blood stream bacterial co-infections. 

Study principle, University of Melbourne Professor Damian Purcell, laboratory head at the Doherty Institute, said that unlike other blood-borne sexually transmitted viral infections, there are few effective interventions and treatments available for HTLV-1, and no effective vaccine.

“Further research on the activity of HTLV-1 during long term infection and how this virus interacts with the host will lead us to antiviral drugs, vaccines or passive immune therapies” said Professor Purcell. 

“People at risk from HTLV-1 deserve biomedical tools against this virus similar to those that provided game-changing therapeutic and prevention options for the other blood-born persistent viral infections like HIV and the HBV and HCV hepatitis viruses,” he said.

“This is critical in Australia, where we have the highest rates of HTLV-1 infection anywhere in the world.” Miss Hirons added.