Background. To our knowledge, the antiviral activity of pegylated interferon alfa-2a has not been studied in participants with untreated human immunodeficiency virus type 1 (HIV-1) infection but without chronic hepatitis C virus (HCV) infection.

Methods. Untreated HIV-1-infected volunteers without HCV infection received 180 mg of pegylated interferon alfa-2a weekly for 12 weeks. Changes in plasma HIV-1 RNA load, CD4⁺ T cell counts, pharmacokinetics, pharmacodynamic measurements of 2^‘,5^’-oligoadenylate synthetase (OAS) activity, and induction levels of interferoninducible genes (IFIGs) were measured. Nonparametric statistical analysis was performed.

Results. Eleven participants completed 12 weeks of therapy. The median plasma viral load decrease and change in CD4⁺ T cell counts at week 12 were 0.61 log10 copies/mL (90% confidence interval [CI], 0.20–1.18 log10 copies/ mL) and -44 cells/μL (90% CI, -95 to 85 cells/μL), respectively. There was no correlation between plasma viral load decreases and concurrent pegylated interferon plasma concentrations. However, participants with larger increases in OAS level exhibited greater decreases in plasma viral load at weeks 1 and 2 (r = -0.75 [90% CI, -0.93 to -0.28] and r = -0.61 [90% CI, -0.87 to -0.09], respectively; estimated Spearman rank correlation). Participants with higher baseline IFIG levels had smaller week 12 decreases in plasma viral load (0.66 log10 copies/ mL [90% CI, 0.06–0.91 log10 copies/mL]), whereas those with larger IFIG induction levels exhibited larger decreases in plasma viral load (-0.74 log10 copies/mL [90% CI, -0.93 to -0.21 log10 copies/mL]).

Conclusion. Pegylated interferon alfa-2a was well tolerated and exhibited statistically significant anti-HIV-1 activity in HIV-1-monoinfected patients. The anti-HIV-1 effect correlated with OAS protein levels (weeks 1 and 2) and IFIG induction levels (week 12) but not with pegylated interferon concentrations.

Trial registration. ClinicalTrials.gov identifier: NCT00078442.