Isolation of single-chain antibody fragments against Venezuelan equine encephalomyelitis virus from two different immune sources

Venezuelan equine encephalomyelitis (VEE) virus is an important human and v eterinary pathogen of Central and South America. The virus can cause widesp read epidemics, affecting hundreds of thousands of horses, and thousands of humans. Detection of the virus early in infection and in mosquito populati ons may allow epidemics to be predicted such that suitable prophylaxis, suc h as vaccination, can be used to reduce disease severity and transmission. The sensitivity and specificity of current immunoassays, based on conventio nal monoclonal and polyclonal antibodies, needs to be improved for the diag nosis of infection. We have examined phage display libraries expressing sin gle-chain antibodies (scFv) produced from two different immune sources, a h ybridoma cell line and an immunized mouse spleen. The libraries were panned against VEE virus to select for specific scFvs. scFvs isolated from both l ibraries were specific for the same epitope on the VEE virus and sequence a nalysis showed that the scFvs were almost identical apart from the CDR3 reg ion of the heavy chain. The data presented in this article suggest that alt hough scFvs may be useful tools for the detection of viruses, there are ser ious limitations with the use of phage display as a tool for the isolation of specific antibodies.