Randomized, placebo-controlled trial of nonpegylated and pegylated forms of recombinant human alpha interferon 2a for suppression of dengue virus viremia in rhesus monkeys

Abstract

Dengue fever and dengue hemorrhagic fever are caused by infection with any one of the four dengue viruses (DVs) and are significant public health burdens throughout the tropics. Higher viremia levels are associated with greater dengue disease severity. A therapeutic intervention to suppress viremia early in DV infection could potentially ameliorate severe disease. Recombinant alpha interferon 2a (rIFN-alpha-2a, Roferon-A) suppressed DV replication in human peripheral blood mononuclear cells in vitro. We therefore examined the effects of rIFN-alpha-2a and pegylated recombinant IFN-alpha-2a (PEG-rIFN-alpha-2a, PEGASYS) on DV serotype 2 (DV-2) viremia in rhesus monkeys. Flavivirus-naïve monkeys were inoculated with DV-2 and randomized to receive a single dose of rIFN-alpha-2a (10 million international units/m2) versus placebo or PEG-rIFN-alpha-2a (6 microg/kg) versus placebo 1 day after the onset of viremia. Serial daily viremia levels were measured, and convalescent-phase DV-2 neutralizing antibody titers were determined. Compared to placebo, a single injection of rIFN-alpha-2a temporarily suppressed DV-2 replication and delayed the time to peak viremia by a median of 3 days. However, measures of total viral burden were not different between the two groups. A single injection of PEG-rIFN-alpha-2a significantly lowered daily viremia levels and improved virus clearance, starting 48 h after administration. There were no significant differences in DV-2 neutralizing antibody titers between the treatment and placebo groups at 30 and 90 days postinfection. Based on their individual effects, future studies should investigate a combination of rIFN-alpha-2a and PEG-rIFN-alpha-2a for suppression of dengue virus viremia and as a potential therapeutic intervention.

FIG. 1.

In vitro effect of rIFN-α-2a on DV-2 replication in PBMC. Healthy donor PBMC (n = 3) were adsorbed with DV-2 16681 for 2 h at a multiplicity of infection of 1, washed, and then cultured in medium with and without rIFN-α-2a. The virus titers in the cell culture supernatants were measured over the next 3 days. Symbols: ⋄, medium alone; ▵, rIFN-α-2a 5 U/ml; ▪, rIFN-α-2a 50 U/ml; ○, rIFN-α-2a 500 U/ml. Values are means ± standard error of the mean. *, P ≤ 0.05 compared to medium alone.

FIG. 2.

Effect of rIFN-α-2a on DV-2 viremia in rhesus monkeys. We inoculated 24 flavivirus-naïve monkeys subcutaneously with DV-2 S16803; 24 h after onset of viremia was detected by qualitative RT-PCR, 12 animals were given a single subcutaneous injection of rIFN-α-2a (10 MIU/m²), and 12 animals were given placebo. Daily plasma viremia levels were measured by a quantitative, fluorogenic RT-PCR assay. The dotted line represents the lower limit of detection. Symbols: □, placebo group; •, treatment group, rIFN-α-2a 10 MIU/m². ↑, time when rIFN-α-2a or placebo was given. Day of viremia is numbered consecutively from the first day viremia was detected by the qualitative RT-PCR assay (day 1). Values are means ± standard error of the mean. *, P < 0.05, rIFN-α-2a group versus placebo.

FIG. 3.

Clearance of DV-2 in the plasma of monkeys after injection with PEG-rIFN-α-2a versus placebo. The elimination t_[1/2] of circulating DV-2 immediately following peak viremia levels was calculated for each animal, as described in the Materials and Methods section. Symbols: ▵, placebo group (n = 5), ▾, treatment group, PEG-rIFN-α-2a 6 μg/kg (n = 5). Bars represent median values. *, P = 0.08, PEG-rIFN-α-2a group versus placebo.