Abstract: MATH/CHEM/COMP 2002, Dubrovnik, June 24-29, 2002

Identification of novel Staphylococcus epidermidis antigens

Brigitte Tempelmaier, Johannes Soellner, Birgit Winkler, Christine Triska, Dieter Gelbmann, and Uwe von Ahsen

Intercell, Forschungs- u. Entwicklungs AG, Campus Vienna Biocenter 6, A-1030 Vienna, Austria

Staphylococcus epidermidis is an opportunistic pathogen of low virulence prevalent on human skin. Due to its ability to colonize and form biofilms on the surface of prosthetic devices it causes serious medical problems. Therefore it is typically linked to nosocomial infections that can lead to the lethal toxic shock syndrome. As the number of multiple drug resistant Staphylococci is rapidly increasing, there is a great need of protective vaccine development.

The basis for the development of defined and synthetic vaccines against disease-causing bacteria is the identification of antigens from bacterial pathogens.

Weichhart et al. [in preparation] previously developed a ribosome display based technology ideal for largely unbiased selection of novel antigens from Staphylococcus aureus.

We used this in vitro method to identify new S. epidermidis antigens that have not been found by the use of conventional in vivo selection techniques. A genomic library with an average fragment size of 100 bp was screened against a library of IgGs from four patients suffering from an S. epidermidis infection. After five rounds of selection and amplification, the recovered library fragments were cloned into a transcriptionally silenced vector and sequenced. Most of the selected fragments consist of cell surface of membrane proteins consistent with the idea that such proteins should be accessible to an immune response. Some of the identified genes are previously described antigens or virulence factors, but most of the selected proteins are novel and are not known to be antigenic in S. epidermidis. Peptide ELISA confirmed the immune reactivity of the selected peptides in the presence of patient antibodies. A number of identified clones match into regions where no ORF has been annotated or to regions complementary to known ORFs. Transcription analyses by means of RT-PCR and serum reactivity of the corresponding peptides support the idea that these clones map into novel ORFs. Moreover, evidence is provided for alternative reading frames in already annotated ORFs.

Taken together, a large number of novel antigens of S. epidermidis could be identified which are the basis for the development of novel, defined and synthetic vaccines.