Epitopes Characterization of S. pneumoniae Pili Protein

Abstract

Streptococcus pneumoniae is Gram positive, extracelluler, highly invasive bacterial pathogen. Its virulence factors includes the pneumolisin toxin, capsule, pneumococcal surface protein and pilus. S. pneumoniae pili is composed of three proteins: RrgA, RrgB and RrgC. Our previous research has identified that: (1) The 54 kDa hemagglutinin protein of S. pneumoniae has a similar structure to the chain A RrgB and; (2) In silico test showed that RrgB protein has 5 epitopes with different amounts of AA. To determine the immunogenicity of the epitope, information about physicochemical characteristics of the epitope is required. The characteristics and immunogenicity of epitope can be studied with the Protparam tool ExPASy and the Vaxi jen V 2.0 SERVER program respectively. Physicochemical characteristic test showed that all epitopes are classified as stable. The identification of AA residues indicated that the 4th epitope has 4 positive charge residues dan no negative charge residue of AA. It implies that the 4th epitope is the most immunogenic epitope. This data contraditcs the results of the immunogenicity test (Vaxi jen V 2.0 SERVER) which shows that the 4th epitope is not an antigen so it is not immunogenic. However, as computerised tools is not gold standart to identity of immunogenicity, an invitro dan invivo experiment is needed to determinent the immunogenicity that epitopes.