Obtenção e análise in silico de sequências de aminoácidos presentes em anticorpos humanos

Abstract

Antibodies are proteins that identify antigens and elicit immune response. The study of antibodies’ biochemical characteristics was, and still is, essential to the development of new technologies that employ such proteins. Due to their function, there is a great diversity of antibodies, which represents a hurdle to the study of antibodies in large scale. This type of study, however, may be a way of arriving to important insights that relate to antibodies as a whole. With the advancement of informatics and bioinformatics, it became possible to do such studies in large scale through in silico methods. This work seeks to obtain amino acid sequences of light and heavy chains of human antibodies and run in silico analysis of the biochemical characteristics of those sequences. The obtainment of the sequences was through the interface of NCBI, a website that unites several data bases, including aminoacid sequence data banks. The “Entrez” tool, which does textual searches, was used for such obtainment. The obtained sequences were then selected through scripts in Python language and numbered by the software ANARCI according to the Kabat numbering scheme. After that, an analysis of the CDRs lengths was done, and through the results two CDRs were selected to be further analyzed. The biochemical analysis were made through the Python language and the graphs were plotted with the MatPlotLib library; the analyses were: amino acid per position, chemical character per position and GRAVY per position. Around 52 thousand light chain sequences and 36 thousand heavy chain sequences were obtained. Some CDRs positions displayed tendencies in either amino acid type per position and/or chemical character per position, which indicates the possibility that those positions played a role in either function or stability of human antibodies. There didn’t seem to be any correlation between the GRAVY per position and the dominant chemical character per position. All in all, it was possible to map certain trends within the studied amino acid sequences, which may provide important data to technologies that deal with humanization, CDR grafting and mutagenesis of human antibodies.