Abstract: Methods for obtaining modified proteins or virus with an intact native binding site and decreased antigenicity and modified proteins or virus obtainable by said methods are provided. The methods of protein or virus modification comprise masking with non-immunogenic molecules the protein or the virus surface, except for the protein or the virus binding site. Examples of modified proteins or virus that can be modified in accordance to the methods include polyclonal or monoclonal antibodies, modified replication-defective virus, hormones, and enterotoxins.