High-Dose Mannose-Binding Lectin Therapy for Ebola Virus Infection

Michelow, Ian C.; Lear, Calli; Scully, Corinne; Prugar, Laura I.; Longley, Clifford B.; Yantosca, L. Michael; Ji, Xin; Karpel, Marshall; Brudner, Matthew; Takahashi, Kazue; Spear, Gregory T.; Ezekowitz, R. Alan B.; Schmidt, Emmett V.; Olinger, Gene G.

We previously found that rhMBL bound Ebola (Zaire) and Marburg (Musoke) envelope GPs [2] . RhMBL effectively blocked Ebola GP interactions with DC-SIGN, and HIV particles lacking gp120/gp41 pseudotyped with Ebola or Marburg GPs were neutralized by the lectin complement pathway [2] . To develop an in vivo test of rhMBL effectiveness, we determined that 100 ng/mL of rhMBL was the minimum concentration needed to inhibit >90% infectivity of HepG2 cells using Ebola GP pseudotyped lentiviral particles and to inhibit >90% infectivity of Vero E6 cells using recombinant Ebola Zaire virus (Mayinga strain)-eGFP (data not shown). We had previously found that a single intraperitoneal dose of 75 lg of rhMBL reconstituted the lectin complement pathway in MBL-knockout mice [1] . We compared the pharmacokinetic parameters (Table 1) Intraperitoneal administration of 100 pfu of native Ebola Zaire virus (3000 3 LD 50 ) is uniformly fatal in mice. Treatment with 75 lg of rhMBL per dose every 12 hours failed to protect mice from that virus inoculum. Therefore, we increased rhMBL to 350 lg administered every 12 hours for 10 days starting either 1 hour before or 12 hours after Ebola virus challenge ( Figure 1A and 1B). When treatment was started 1 hour before virus infection, the supraphysiological dose increased survival to . 40% of mice in several trials ( Figure 1A) . We then started treatment 12 hours after viral infection. We compared survival in wild-type and complement component 3 (C3)-deficient mice as the inhibitory effects of MBL on Ebola virus are mediated by complement in cell culture [2] . Once again we saw an increase in survival from 0% to .40% in rhMBL-treated mice, and survival was dependent on an intact complement pathway, since C3deficient mice did not survive ( Figure 1B ). All inoculated mice showed signs of infection according to standardized observation scores and weight loss, and surviving mice had detectable Ebola virus-specific antibodies 28 days after infection (data not shown).