A recent study used a new imaging technique to look at a real-time map of HIV in rhesus macaques, and while certain findings matched up with previous knowledge of the virus, some findings shed light on different aspects of the virus and its course of infection. A research team led by Francois Villinger of Emory University mimicked a technique used with cancer patients. The researchers first attach a radioactive molecule to an antibody against the surface protein of SIV (Simian Immunodeficiency virus), the monkey counterpart of HIV. The researchers injected the radioactive antibody into 12 monkeys with chronic SIV, and the antibodies clung on to the virus. A positron emission tomography (PET) scan detected the antibodies and basically lit up the virus in the monkeys.
The images showed the virus where it was suspected to be, mainly the lymph nodes and the gut. However these images also showed high levels of virus in the nasal cavity, the respiratory tract, and the lungs. The male genital tract, more specifically the epididymis, was also especially virus-rich, which is interesting because sexual transmission of HIV is not particularly easy. Villinger commented on the importance and novelty of these new findings: “We need to know where the virus goes, how it gets there, and why it’s a benefit to the virus. These pieces of the puzzle are really important.” The team also valued this information because it is not something that a biopsy or PCR test could tell you.
The researchers then gave 3 of the monkeys antiretroviral (ARV) drugs and gave the monkeys PET scans about 5 weeks after administration of the drugs. While the images showed that the monkeys didn’t have detectable amounts of SIV in their blood, biopsies showed that there was still replicating virus in certain reservoir tissues. The immunoPET technique could be used to identity those tissues that can act as reservoirs and hide the virus from the ART drugs. This finding suggests that fully suppressed HIV-patients still harbor the replicating virus and that the drugs might not be as effective as we think. While the interpretations of this study need further research, it’s clear that looking at HIV in a real time setting has its benefits and will shed light on this complicated virus.
- Nalani Wakinekona