Almost half of Indigenous adults in Central Australia are infected with a virus which can cause lung disease and blood cancers yet many physicians are unaware of it, an infectious disease specialist warns.
A prospective hospital-based study found patients with a HTLV-1c proviral load (pVL) ≥1% (1,000 copies per 105 peripheral blood leukocytes) had a marked increase in mortality compared to uninfected patients or those with a lesser viral load.
Mortality rates were 28.4% with a high pVL, 20.2% with a low pVL and 15.9% without the HTLV-1 infection.
A high proviral load of the virus also predicted bronchiectasis-related deaths in the Indigenous population in Central Australia.
The study confirmed bronchiectasis in 19.2% of patients with HTLV-1c infections and in 8.4% of patients without the retrovirus.
It also showed a new association between the virus and bronchitis or bronchiolitis.
“The median HTLV-1c pVL of subjects with radiologically defined airways inflammation was 16-fold higher than that for asymptomatic HTLV-1-infected subjects, and risk of airway inflammation increased three-fold among subjects with higher HTLV-1c pVL in an adjusted model,” the study said.
Infectious diseases physician Dr Lloyd Einsiedel told the limbic the virus-infected cells provoke inflammation when they infiltrate tissues such as the lungs, spinal cord, skin and eyes.
He said about 45% of Indigenous adults in Central Australia were infected and about 20% of those people had abnormal lung function.
“Clearly a public health response is warranted just on the basis of those results,” he said.
Dr Einsiedel, from the Alice Spring Hospital and the Baker Heart and Diabetes Institute, said few people were aware of HTLV-1 as an issue and there was also a degree of therapeutic nihilism.
“And that means we aren’t doing enough to educate our specialists and particularly respiratory specialists about this as a problem.”
He said Japanese research had recently shown a new monoclonal antibody was effective in reducing the viral load, inflammatory markers and disability in patients with HTLV-1 associated myelopathy/ tropical spastic paraparesis (HAM/TSP).
Mogamulizumab, already licensed in Japan for HTLV-1 associated adult T-cell leukaemia/lymphoma, targets the CCR4+ T-cells which are the main reservoir for the virus.
“And what we would anticipate is, in the next 3-5 years, we would be in a position to treat people with HTLV-1 associated pulmonary disease with this monoclonal antibody,” Dr Einsiedel said.
What needs to be done now is screening patients for the virus then determining their HTLV-1 proviral loads in order to stratify their risk and intensity of follow-up, he said.
“People with a high proviral load are at risk of developing life threatening complications so we need to follow them up more frequently and especially as we get closer to treatments that would be safe and effective in our setting.”
He added that respiratory physicians should think about the possibility of HTLV-1 infection in any patients with potential links to an endemic area such as Central and Western Australia.