Defining Limits of Treatment with Humanized Neutralizing Monoclonal Antibody for West Nile Virus Neurological Infection in a Hamster Model

Abstract

A potent anti-West Nile virus (anti-WNV)-neutralizing humanized monoclonal antibody, hE16, was previously shown to improve the survival of WNV-infected hamsters when it was administered intraperitoneally (i.p.), even after the virus had infected neurons in the brain. In this study, we evaluated the therapeutic limit of hE16 for the treatment of WNV infection in hamsters by comparing single-dose peripheral (i.p.) therapy with direct administration into the pons through a convection-enhanced delivery (CED) system. At day 5 after infection, treatments with hE16 by the peripheral and the CED routes were equally effective at reducing morbidity and mortality. In contrast, at day 6 only the treatment by the CED route protected the hamsters from lethal infection. These experiments suggest that hE16 can directly control WNV infection in the central nervous system. In support of this, hE16 administered i.p. was detected in a time-dependent manner in the serum, cerebrospinal fluid (CSF), cerebral cortex, brain stem, and spinal cord in CSF. A linear relationship between the hE16 dose and the concentration in serum was observed, and maximal therapeutic activity occurred at doses of 0.32 mg/kg of body weight or higher, which produced serum hE16 concentrations of 1.3 g/ml or higher. Overall, these data suggest that in hamsters hE16 can ameliorate neurological disease after significant viral replication has occurred, although there is a time window that limits therapeutic efficacy.Since patients infected with West Nile virus (WNV) often present for medical attention with symptoms that suggest possible central nervous system (CNS) infection (9), therapies for WNV neurological disease should work even after the virus has infected the CNS. One possible therapy, immune immunoglobulin G (IgG), is being evaluated in a phase IIB clinical trial (NIH identifier NCT00068055) that assesses safety and efficacy in patients with known or suspected WNV infection. However, the product (Omr-IgGam) was generated from pools of nonimmune and immune serum from Israeli donors and has a relatively low neutralizing activity against the strains of WNV that currently circulate in North America (2, 6).A mouse monoclonal antibody (MAb), E16, specific for domain III (DIII) of the envelope protein, has been identified to have potent WNV-neutralizing activity (7,19,20). This MAb engaged 16 residues positioned on four loops of DIII and formed a consensus neutralizing epitope in virtually all WNV strains tested (18). Structural and virological studies suggest that E16 blocks infection at a postattachment state, possibly by inhibiting virus-endosome fusion and nucleocapsid release into the cytoplasm (18). A humanized version of E16 (hE16) that retained its antigen specificity, avidity, and neutralizing activity was generated. Studies with mice showed that treatment was effective even at 5 days after viral injection (16,19), a time at which infectious virus was identified in homogenized mouse brain.Studies with a hamster model of WNV infection subsequently confi...

Genotype-Specific Neutralization and Protection by Antibodies against Dengue Virus Type 3

“…This model, which does not reflect DENV-3 pathogenesis in humans, nonetheless is particularly stringent for protection, as immunocompromised AG129 mice are challenged by an i.c. route and only a small fraction (ϳ0.1%) of IgG crosses the blood-brain barrier in rodents during flavivirus infection (36). This challenge route was necessary, as virtually all DENV-3 isolates replicated poorly in mice after peripheral (subcutaneous, intraperitoneal, or intravenous) inoculation.…”

The Immunopathogenesis of Neurotropic Flavivirus Infection

“…Prophylactic treatment with these antibodies protects mice against lethal WNV infection ). On the other hand, humanised mAb E16 is able to increase survival of both mice and hamsters, even when administered after the CNS is infected Morrey et al, 2007). The treatment of hamsters 5 days after WNV inoculation with this E16 antibody also results in decreased viral burden in the CNS and increased survival (Morrey et al, 2006).…”

“…Thus, not surprisingly, both the specific epitope and binding affinity play a role (Sanchez et al, 2005). Other factors limiting antibody-mediated treatment include the poor movement of antibodies across an intact BBB to enable them to act on virus-infected neurons (Cheeran et al, 2005;Morrey et al, 2007) and the possibility that mutant virus strains might arise through antibody treatment. For example, mutations of the E16 epitope of the virus can abrogate the neutralising activity of monoclonal antibodies (Li et al, 2005;Sanchez et al, 2005).…”

“…Of the myriad antibodies induced by WNV infection only a few neutralise WNV and have a possible therapeutic role. Neutralising antibodies are mainly directed against domain III of the WNV envelope-protein where they prevent the conformational change in the virus required to fuse to cellular membranes, consequently inhibiting it from entering the cell Throsby et al, 2006;Morrey et al, 2007;S. Zhang et al, 2009).…”

Practical Considerations of Convection Enhanced Delivery for Novel Therapies Treating Spinal Cord Injury Related Neuropathic Pain

“…Single-dose peripheral (intraperitoneal) treatment was compared to CED with relation to use of the anti-West Nile virus neutralizing humanized monoclonal antibody, hE16, in the treatment of WNV infected hamsters [46]. CED via direct administration into the pons protected the hamsters from lethal infection for greater time compared to peripheral treatment.…”