A neutralizing human monoclonal antibody protects african green monkeys from hendra virus challenge

Abstract

Hendra virus (HeV) is a recently emerged zoonotic paramyxovirus that can cause a severe and often fatal disease in horses and humans. HeV is categorized as a biosafety level 4 agent, which has made the development of animal models and testing of potential therapeutics and vaccines challenging. Infection of African green monkeys (AGMs) with HeV was recently demonstrated, and disease mirrored fatal HeV infection in humans, manifesting as a multisystemic vasculitis with widespread virus replication in vascular tissues and severe pathologic manifestations in the lung, spleen, and brain. Here, we demonstrate that m102.4, a potent HeV-neutralizing human monoclonal antibody (hmAb), can protect AGMs from disease after infection with HeV. Fourteen AGMs were challenged intratracheally with a lethal dose of HeV, and 12 subjects were infused twice with a 100-mg dose of m102.4 beginning at either 10, 24, or 72 hours after infection and again about 48 hours later. The presence of viral RNA, infectious virus, and HeV-specific immune responses demonstrated that all subjects were infected after challenge. All 12 AGMs that received m102.4 survived infection, whereas the untreated control subjects succumbed to disease on day 8 after infection. Animals in the 72-hour treatment group exhibited neurological signs of disease, but all animals started to recover by day 16 after infection. These results represent successful post-exposure in vivo efficacy by an investigational drug against HeV and highlight the potential impact a hmAb can have on human disease.

Figure 1. Survival curve of HeV-infected monkeys

Data from control subjects and m102.4-treated subjects were used to generate the Kaplan-Meier survival curve. Control included data from two additional historical control subjects (28). Subjects received m102.4 infusions at 10 hours and 3 days p.i. (10hr/d3), 24 hrs and 3 days p.i. (24hr/d3) or 72 hrs and 5 days p.i. (72hr/d5). Each group contained 4 subjects (n=4). Average time to end stage disease was 8 days in control subjects whereas all m102.4 treated subjects survived until euthanasia at the end of the study.

Figure 2. HeV antigen and viral RNA in untreated control AGM tissues and viral RNA in blood from m102.4 efficacy trial

(A) Localization of HeV antigen by immunohistochemical stain in the lung and brainstem of AGM 13. Sections were stained with a NiV nucleoprotein (N) specific rabbit polyclonal antibody and images were obtained at an original magnification of at 40X; however one panel was photographed at 200X as indicated. (B) Detection of HeV RNA in tissues collected from AGM 13 and AGM 17. (C) Detection of HeV RNA in blood samples. RNA samples were assayed in triplicate using TaqMan PCR. Blood and tissue Ct values were analyzed against Ct values generated from a standard curve of HeV RNA, as described in the methods, and a relative HeV N expression value was calculated for each blood replicate. Results are shown as average relative HeV N gene expression levels. The data are mean +/− SD. In panel C data from individual subjects are shown and indicated as none or different hatched patterns, and bar coloration (inset legend) indicates the different treatment groups. Virus isolation was attempted on all tissue and blood samples, and positive samples are indicated by (+). The blood sample (*) from one control subject was a terminal sample taken on day 8; lymph node.

Figure 3. Detection of F-specific antibodies in m102.4 treated AGMs

Median fluorescence intensities (M.F.I.) are shown on the Y-axis and represent binding to soluble F. Error bars represent the standard deviation of fluorescence intensity across 100 beads for each sample. Three of 4 subjects in the 10hr/d3 group were sampled on days 24 and 30 instead of days 27 and 35; the remaining animal ( ) in this group was sampled on day 27 and 35. No sample (*) was collected for one animal ( ) on day 24.