ABSTRACT
The measles virus (MV) is a major cause of childhood morbidity and mortality worldwide. We previously established a mouse monoclonal antibody, 2F4, which shows high neutralizing titers against eight different genotypes of MV. However, the molecular basis for the neutralizing activity of the 2F4 antibody remains incompletely understood. Here, we have evaluated the binding characteristics of a Fab fragment of the 2F4 antibody. Using the MV infectious assay, we demonstrated that 2F4 Fab inhibits viral entry via either of two cellular receptors, SLAM and Nectin4. Surface plasmon resonance (SPR) analysis of recombinant proteins indicated that 2F4 Fab interacts with MV hemagglutinin (MV-H) with a KD value at the nm level. Furthermore, we designed a single-chain Fv fragment of 2F4 antibody as another potential biopharmaceutical to target measles. The stable 2F4 scFv was successfully prepared by the refolding method and shown to interact with MV-H at the µm level. Like 2F4 Fab, scFv inhibited receptor binding and viral entry. This indicates that 2F4 mAb uses the receptor-binding site and/or a neighboring region as an epitope with high affinity. These results provide insight into the neutralizing activity and potential therapeutic use of antibody fragments for MV infection.
Subject(s)
Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Immunoglobulin Fab Fragments/immunology , Measles virus/immunology , Measles/immunology , Single-Chain Antibodies/immunology , Viral Proteins/immunology , Antibodies, Neutralizing/biosynthesis , Antibodies, Neutralizing/genetics , Antibodies, Viral/biosynthesis , Antibodies, Viral/genetics , Epitopes/immunology , HEK293 Cells , Humans , Immunoglobulin Fab Fragments/biosynthesis , Immunoglobulin Fab Fragments/genetics , Measles/virology , Nectins/antagonists & inhibitors , Nectins/immunology , Nectins/metabolism , Protein Binding , Signaling Lymphocytic Activation Molecule Family Member 1/antagonists & inhibitors , Signaling Lymphocytic Activation Molecule Family Member 1/immunology , Signaling Lymphocytic Activation Molecule Family Member 1/metabolism , Single-Chain Antibodies/biosynthesis , Single-Chain Antibodies/genetics , Virus InternalizationABSTRACT
The BacMam system uses modified insect viruses (baculoviruses) as vehicles to efficiently deliver genes for expression in mammalian cells. The technique can be widely applied to large-scale recombinant protein production with appropriate modifications, high-throughput screening platforms for cell-based assays, and the delivery of large genes. The silkworm system is often employed as a rapid and cost-effective approach for recombinant baculovirus generation. Here we have developed the novel BacMam system using silkworm baculovirus, and shown the successful expression of EGFP in mammalian cells. The transduction to mammalian cells via the BacMam system was improved by adding phosphate-buffered saline and sodium butyrate to the culture medium and lowering the temperature after viral infection. This study provides an alternative gene delivery system for mammalian cells, which has various potential applications, including efficient native protein production and gene therapy.
