Gabriela Martinez

Identification of a Surface Protein of Streptococcus suis and Evaluation of Its Immunogenic and Protective Capacity in Pigs

ABSTRACT A Streptococcus suis surface protein reacting with convalescent-phase sera from pigs clinically infected by S. suis type 2 was identified. The apparent 110-kDa protein, designated Sao, exhibits typical features of membrane-anchored surface proteins of gram-positive bacteria, such as a signal sequence and an LPVTG membrane anchor motif. In spite of high identity with the partially sequenced genomes of S. suis Canadian strain 89/1591 and European strain P1/7, Sao does not share significant homology with other known sequences. However, a conserved avirulence domain that is often found in plant pathogens has been detected. Electron microscopy using an Sao-specific antiserum has confirmed the surface location of the Sao protein on S. suis. The Sao-specific antibody reacts with cell lysates of 28 of 33 S. suis serotypes and 25 of 26 serotype 2 isolates in immunoblots, suggesting its high conservation in S. suis species. The immunization of piglets with recombinant Sao elicits a significant humoral antibody response. However, the antibody response is not reflected in protection of pigs that are intratracheally challenged with a virulent strain in our conventional vaccination model.

Serotype III Streptococcus agalactiae from bovine milk and human neonatal infections

Although largely unrelated, many bovine type III GBS appear to share a common ancestor with an important human clone.

Cloning, Purification, and Enzymatic Properties of Dipeptidyl Peptidase IV from the Swine Pathogen Streptococcus suis

In this study, the dipeptidyl peptidase IV (DPP IV) of the swine pathogen Streptococcus suis was cloned, overexpressed in Escherichia coli, and characterized. The coding region comprises 2,268 nucleotides containing an open reading frame that codes for a 755-amino-acid protein with a calculated molecular mass of 85 kDa. The amino acid sequence contained the sequence Gly-X-Ser-X-X-Gly, which is a consensus motif flanking the active-site serine shared by serine proteases. The recombinant DPP IV showed a high affinity for the synthetic peptide glycine-proline-p-nitroanilide and was strongly inhibited by Hg2+ and diprotin A.