HIV co-infection does not cause multidrug-resistant tuberculosis
For many years, the human immunodeficiency virus (HIV) pandemic has fueled tuberculosis outbreaks worldwide. However, new research shows that HIV co-infection does not specifically drive the development and transmission of multidrug-resistant tuberculosis, as previously suspected.
Researchers from Norway, UK and Argentina collaborated in a study that shows how multidrug-resistant tuberculosis bacteria do not evolve to a greater degree among HIV positive patients than HIV negative patients.
Tuberculosis and HIV are a major global health challenge, both as individual diseases and in combination.
“It is already well-known that the HIV pandemic is one of the biggest hurdles to combating tuberculosis, and work is ongoing on several fronts to tackle both diseases,” says Vegard Eldholm at the Norwegian Institute of Public Health, who led the study with Francois Balloux at University College London.
HIV and tuberculosis still claim many lives every year and countries without access to effective drugs and monitoring are at greatest threat.
Of 1.5 million people who died of tuberculosis in 2015, approximately 200,000 cases were caused by multidrug-resistant tuberculosis and 400,000 had both HIV and tuberculosis. To explore how HIV co-infection affects multidrug-resistance, the team analysed the genomes of tuberculosis bacteria isolated from patients from the largest known outbreak of multidrug-resistant tuberculosis in South America.
The isolates were collected from patients with known HIV status from the mid-1990s until 2009. The genomes were used to construct a ‘family tree’ to summarise the evolution of the outbreak. Mathematical modelling was also used to reconstruct how tuberculosis spreads between individuals. Finally, the researchers combined these results to estimate the length of the latent period in individual patients and whether multidrug resistance evolved equally among HIV positive and HIV negative patients.
“We saw no effect from HIV status on mutation rate or the development of multidrug resistance,” says Francois Balloux, Director of the UCL Genetics Institute in London.
“HIV destroys the immune system and impairs the body's ability to fight off other infections. Although HIV is beneficial to tuberculosis because it makes an individual highly susceptible to infection, we cannot demonstrate that the pandemic only caused the development of multidrug resistance in HIV patients,” explains Vegard Eldholm.he concludes.