Late remdesivir treatment initiation partially protects African green monkeys from lethal Nipah virus infection

Abstract

Remdesivir is a nucleotide prodrug with preclinical efficacy against lethal Nipah virus infection in African green monkeys when administered 1 day post inoculation (dpi) (Lo et al., 2019). Here, we determined whether remdesivir treatment was still effective when treatment administration initiation was delayed until 3 dpi. Three groups of six African green monkeys were inoculated with a lethal dose of Nipah virus, genotype Bangladesh. On 3 dpi, one group received a loading dose of 10 mg/kg remdesivir followed by daily dosing with 5 mg/kg for 11 days, one group received 10 mg/kg on 12 consecutive days, and the remaining group received an equivalent volume of vehicle solution. Remdesivir treatment initiation on 3 dpi provided partial protection from severe Nipah virus disease that was dose dependent, with 67% of animals in the high dose group surviving the challenge. However, remdesivir treatment did not prevent clinical disease, and surviving animals showed histologic lesions in the brain. Thus, early administration seems critical for effective remdesivir treatment during Nipah virus infection.

Keywords: Antiviral; Nipah virus; Nonhuman primate; Nucleotide analog; Remdesivir.

Figure 1.. Effect of remdesivir treatment on Nipah virus infection in African green monkeys.

Three groups of six African green monkeys were inoculated with Nipah virus, genotype Bangladesh; remdesivir treatment was initiated 3 days later. One group received a loading dose of 10mg/kg remdesivir followed by daily dosing with 5mg/kg for 11 days (RDV 5mg/kg), one group received 10mg/kg for 12 consecutive days (RDV 10mg/kg), and the remaining group received an equivalent volume of vehicle solution (vehicle). A. Survival in animals inoculated with a lethal dose of Nipah virus, genotype Bangladesh and treated with remdesivir or vehicle. Statistical significance compared to the vehicle group was calculated in a log-rank (Mantel-Cox) test. B. Daily clinical scores were obtained by a person blinded to the group assignment of the animals using a standardized scoring sheet. C. Whole blood was collected from all animals in study on 0, 3, 5, and 8 dpi and analyzed for the presence of viral RNA. Data from animals treated with remdesivir are grouped by outcome (endpoint criteria reached before study endpoint vs. survival until the end of the experiment). In each run, counted RNA standards were included to calculate the copy number in the samples. Statistical analysis was performed using a 2-way ANOVA with Tukey’s multiple comparisons tests; p-values <0.05 were considered significant and are indicated. D. At euthanasia, cerebro-spinal fluid (CSF) was collected from all animals and analyzed for the presence of viral RNA. Open symbols indicate animals that survived until study end; closed symbols indicate animals that reached endpoint criteria and were euthanized before study endpoint. E. Lung tissue samples were collected from each lung lobe and (F) from three regions of the central nervous system and analyzed for the presence of viral RNA. Squares indicate animals that survived until study end; circles indicate animals that reached endpoint criteria and were euthanized before study endpoint.

Figure 2.. Histopathologic findings in the lungs and brains of remdesivir-treated animals.

In the animals in the RDV 5mg/kg group that reached endpoint criteria before the study end (n=4) and in all animals in the vehicle-treated group (n=6), the lungs were characterized by abundant alveolar and perivascular edema, fibrin accumulation, and marked bronchointerstitial pneumonia. In the CNS of all animals that in the RDV 5mg/kg group that reached endpoint criteria before the study end (n=2) and in the CNS of one of the vehicle-treated animals there were rare mild regions of perivascular cuffing. In one of the two of animals in the RDV 5mg/kg group that survived to the end of the experiment, and five of six animals in the RDV 10mg/kg group, there were varying degrees of nonsuppurative perivascular cuffing and/or meningoencephalitis in the CNS and no significant findings in the lungs. Lung magnification 100x, scale bar 200μm. Brain magnification 200x, scale bar 100μm. The number of animals with and without histologic lesions in lungs and brains in each group is indicated in Fig. S1C.