Recombinant human respiratory syncytial virus (RSV)monoclonal antibody Fab is effective therapeutically when introduced directlyinto the lungs of RSV-infected mice.

Abstract

Previously, recombinant human respiratory syncytlal virus (RSV) monoclonal antibody Fabs were generated by antigen selection from random combinatorial libraries displayed at the tip of filamentous phage. Two such Fabs, which exhibited high binding affinity for RSV F glycoprotein (a major protective antigen), were evaluated for therapeutic efficacy in infected mice just before or at the time of peak virus replication in the lungs. Fab 19, which neutralized RSV infectivity with high efficiency in tissue culture, was effective therapeutically when delivered directly into the lungs by intranasal instillation under anesthesia. In contrast, RSV Fab 126, which failed to neutralize virus in cell culture, did not exhibit a therapeutic effect under these conditions. The amount of Fab 19 required to effect a 5000-to 12,000-fold reduction in titer of RSV in the lungs within 24 hr was rather small. In four separate experiments, a single instillation of 12.9-50 pg ofRSV Fab 19 was sufficient to achieve such a reduction in pulmonary virus in a 25g mouse. The use of Fabs instead of the whole immunoglobulin molecules from which they are derived reduced the protein content of a therapeutic dose. This is important because the protein load that can be delivered effectively into the lungs is limited. The therapeutic effect of a single treatment with Fab 19 was not sustained, so that a rebound in pulmonary virus titer occurred on the 2nd day after treatment. This rebound in pulmonary RSV titer could be prevented by treating infected mice with a single dose of Fab 19 daily for 3 days. These observations suggest that human monoclonal Fabs grown in Escherichia coli may prove useful in the treatment of serious RSV disease as well as diseases caused by other viruses where replication in vivo is limited primarily to the lumenal lining of the respiratory tract.Antibodies specific for respiratory syncytial virus (RSV) are of importance because of the urgent need to prevent or treat disease caused by this virus. Indeed, RSV is the major cause of serious viral lower respiratory tract illness in infants and young children worldwide (1). This virus is estimated to be responsible for -1 million deaths annually among infants and young children, mostly in developing countries. In the United States and in this age group, RSV commonly causes serious lung disease, necessitating hospitalization and intensive medical care. This virus has also recently emerged as an important cause of fatal pulmonary disease among individuals of any age who are immunosuppressed incident to organ transplantation, cancer chemotherapy, or human immunodeficiency virus (HIV) infection.Studies in experimental animals provided solid evidence that RSV-specific neutralizing antibodies could (i) prevent virus infection in the lungs when administered before exposure to virus and (ii) effect rapid resolution of infection when administered at the height of infection (2). Clinical trials have validated these aforementioned experimental observations. In a recently reported clin...

Infant baboons infected with respiratory syncytial virus develop clinical and pathological changes that parallel those of human infants

“…We also determined titers of RSV-neutralizing antibody (NA) in baboon sera using published methods (10). An RSV stock was diluted to contain 500 pfu/ml, and 0.5 ml of this stock was incubated with 0.5 ml of twofold dilutions of baboon sera in growth medium.…”

Functional Maturation of the Human Antibody Response to Rotavirus

“…We constructed chimeric Abs using portions of the Ab genes from respiratory syncytial virus (RSV) Fab19, a recombinant human Fab to a heterologous virus Ag (RSV F glycoprotein) that we previously isolated (20,21). The plasmid vectors containing the chimeric combinations of RV6-26 and RSV Fab19 Ab variable gene sequences were prepared by inserting a specific restriction enzyme site and then using molecular cloning techniques.…”

Human recombinant antibodies specific for hepatitis C virus core and envelope E2 peptides from an immune phage display library

“…Specific antibodies were obtained by sequential rounds of selection on proteins or haptens (Marks et al, 1991a). Application of the technology for the therapeutic treatment of viral infections seems promising and, if feasible, would open up a new area using engineered antibodies as therapeutic agents (Burioni et al, 1994;Burton et al, 1994;Crowe et al, 1994). The present study illustrates the feasibility of obtaining human recombinant antibodies which recognize the target protein molecules by selection using peptides derived from the core and the E2 regions of HCV.…”