The authors were interested in the clinical features of HIV type 1 group O (HIV-1/O) infection and how it responds to ART. They studied a series of 101 patients and found that during the natural course of their infection, there was a 16.6% cumulative probability of reaching stage C within 5 years following HIV diagnosis and a mean decrease in CD4+ T cell count of -30.5 cells/mm^3/year. When ART was initiated in ART-naive patients, there was a mean gain of +147 CD4+ T cells/mm^3 after 12 months, and to a median viral load of <40 cp/mL after 3.8 months for 89.3% of patients. Initiation with a non-recommended NNRTI- versus a PI/r-based regimen led to a much smaller gain of around 100 CD4+ T cells/mm^3 after one year. Patients who were still being followed up since 2007 had a median CD4+ T cell count of 498 cells/mm^3 and 87% had a viral load <40cp/mL. Therefore HIV-1/O infection appears to undergo a milder disease process compared with HIV-1/M and HIV-1/M guidelines can be used to treat it despite the genetic divergence.
Read more here