A real-time, full body, imaging technique that allows the detection of viral presence in regions of the body not accessible to conventional detection methods is reported in a study published online this week in Nature Methods. The technique was used to locate viral reservoirs of Simian immunodeficiency virus (SIV) in Rhesus monkeys.
SIV (a virus similar to HIV that infects non-human primates) and HIV are typically detected in blood samples from those infected. However, the number of viral particles in the bloodstream can be reduced, by antiretroviral therapy or the immune systems of “elite controllers”, to levels that are not detectable by these methods. The viruses, however, persist in reservoirs in the body and can re-emerge when therapy is interrupted or the immune system is compromised. Blood tests cannot pinpoint the location of these hidden reservoirs and methods to detect them are needed.
Francois Villinger and colleagues used positron emission tomography (PET) in combination with an SIV-specific tracer to analyse the distribution of SIV in monkeys treated with antiretroviral therapy and in elite controller monkeys. Despite the barely detectable SIV levels in the blood of these monkeys, the virus was detected in the lymph nodes, the intestines, the lungs and other regions in the body. This approach opens up new avenues to study SIV infection dynamics in monkeys, and in the future it could also be adapted to benefit research into HIV reservoirs in humans.