The present invention provides, among other things, methods and compositions for delivering an antibody in vivo by administering to a subject in need thereof one or more mRNAs encoding a heavy chain and a light chain of an antibody, and wherein the antibody is expressed systemically in the subject. In some embodiments, the one or more mRNAs comprise a first mRNA encoding the heavy chain and a second mRNA encoding the light chain of the antibody.
