Preparation and characterization of a Staphylococcus aureus capsular polysaccharide-protein conjugate prepared by a low cost technique: a proof-of-concept study.

NAZARENA PUJATO, ; GERMÁN. DÍAZ, ; M. S. BARBAGELATA,; M. VICCO, ; L. CALVINHO, ; I. MARCIPAR

APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY

HUMANA PRESS INC

Lugar: Oregon; Año: 2015 vol. 175 p. 141 - 154

0273-2289

Staphylococcus aureus is a worldwide distributed pathogen that produces severaldiseases in many species and is the major cause of mastitis in dairy cows. S. aureus capsularpolysaccharide 5 (CP5) has been widely proposed as a vaccine candidate since it is expressedin a high proportion of isolates from intramammary infections and is able to induceopsonophagocytic antibodies. However, to reach immunological properties, polysaccharidesneed to be coupled to carrier proteins. The aim of this study was to evaluate a conjugationmethod employing p-benzoquinone (PBQ), which was not previously reported for the development of vaccine components. Purified S. aureus CP5 was coupled to human serumalbumin (HSA) with high efficiency, reaching a rate PS/protein of 0.5. Mice groups wereimmunized at days 0, 14, 28, and 42, with the conjugate (CP5-HSAPBQ), free CP5, or PBS,formulated with incomplete Freund adjuvant, and after 3 months, they were challenged withfree CP5 to evaluate the memory response. IgG and IgM isotypes were measured on serumsamples all along the experiment, and IgG subclasses were determined to analyze the humoralprofile. In contrast to the response obtained with free CP5, CP5-HSAPBQ induced IgG titers of1/238,900 after three doses and a memory response was observed after the challenge. Resultsindicate that immunization with CP5-HSAPBQ effectively induce a T-dependent immuneresponse against CP5. Moreover, besides IgG2a was the main subtype obtained, the jointproduction of specific IgG1, IgG2b, and IgG3 types indicated a balanced humoral response.As p-benzoquinone conjugation of CPs to proteins is far less expensive and straightforwardthan other methods commonly used in vaccine preparations, the robust humoral responseobtained using this method points out that this can be an interesting alternative to prepareS. aureus CP5 conjugate vaccines