A deadly virus no one talks about — and the HIV drugs that might stop it

 Around 10 million people globally live with the life-threatening virus HTLV-1. Yet it remains a poorly understood disease that currently has no preventative treatments and no cure.

But a landmark study co-led by Australian researchers could change this, after finding existing HIV drugs can suppress transmission of the HTLV-1 virus in mice.

The study, published in Cell, could lead to the first treatments to prevent the spread of this virus that is endemic among many First Nations communities around the world, including in Central Australia.

The research by WEHI and the Peter Doherty Institute for Infection and Immunity (Doherty Institute) also identifies a new drug target that could lead to the elimination of HTLV-1 positive cells from those with an established infection, and prevent disease progression.

At a glance

• New research co-led by WEHI and the Doherty Institute could lead to the first preventative treatments for HTLV-1, one of the most complex and neglected viruses in the world.
• The study found two specific HIV antivirals already on the market can suppress transmission of HTLV-1 in humanized mice and prevent disease, identifying the first prophylactic treatment against HTLV-1.
• Secondly, when the HIV antivirals were used in combination with a compound that induces cell death, infected cells were killed - flagging a potential future curative strategy for the disease.
• The unprecedented findings could enable these drugs to enter clinical trials preventing establishment of pathogenic levels of HTLV-1.

Human T-cell leukemia virus type 1 (HTLV-1) is a virus that infects the same cell type as HIV - T cells, a type of blood immune cell that helps the body fight off infections.

A small proportion of people infected with HTLV-1 after a long duration of infection develop serious diseases, such as adult T-cell leukemia and spinal cord inflammation.

Co-lead author and WEHI laboratory head Dr Marcel Doerflinger said the promising results of the new study could help find a desperately needed treatment and prevention strategy for one of the most neglected viruses in the world.

"Our study marks the first time any research group has been able to suppress this virus in a living organism," Dr Doerflinger said.

"As HTLV-1 symptoms can take decades to appear, by the time a person knows they have the infection the immune damage is already in full swing.

https://www.sciencedaily.com/releases/2025/07/250723045708.htm#:~:text=%22Suppressing%20the%20virus,at%20Centenary%20Institute.

Prof Pellegrini said the mouse models were not only critical in identifying potential therapeutic targets, but also allowed researchers to understand how different strains of the HTLV-1 virus can alter disease symptoms and outcomes. This is particularly important for the unique strain that is present in Australia, HTLV-1c.

"It's long been hypothesized that differences in viral subtype may influence disease outcomes, but a lack of research into HTLV-1 has made it difficult for us to find the evidence needed to support this claim - until now.

"Our study provides critical insights that enable us to better understand the consequences of the distinct molecular make-up of the virus affecting our First Nations communities. This will further help us to investigate ways to create the tools needed to control the spread of this virus subtype."

The human HTLV-1 samples needed to develop the mouse models were obtained through the front-line clinical work of Associate Professor Lloyd Einsiedel, a Clinician Scientist at the Doherty Institute and Infectious Diseases Physician, who has provided a clinical service to Central Australia for more than a decade and has dedicated his career to putting HTLV-1 on the map.

Advocacy for a neglected disease

Research by the University of Melbourne's Professor Damian Purcell, Head of Molecular Virology at the Doherty Institute and co-lead author of the study, isolated the virus from First Nations donors and identified significant genetic differences between the HTLV-1c strains from Central Australia compared to the HTLV-1a strains found internationally.

The new findings show that both HTLV-1 strains cause disease in mice, with HTLV-1c showing more aggressive features. The identified drug therapies were found to be equally effective against both strains.

Prof Purcell and Associate Prof Lloyd Einsiedel worked with the National Aboriginal Community Controlled Health Organization (NACCHO) HTLV-1 committee and the Australian Department of Health over many years to advocate for guidance on HTLV-1 from the World Health Organization (WHO) that led to them formally classify the virus as a Threatening Pathogen to Humans in 2021.

sources-science daily