M. bovis infection in pigs: Improvement of the γ-IFN assay efficiency in this species using a maintenance medium.

The interferon-gamma (IFN-γ) test measures cell mediated immune response (CMI) during the early stages of tuberculosis infection. Although Bovine Tuberculosis (BT) spread in feral pigs is widely documented in literature, the effectiveness of IFN-γ in this species has been only recently reported. One of the major obstacle of this assay is that whole blood samples should be stimulated with purified protein derivative (PPD) cocktail within 8 h from the blood sampling. This study set up a defined broth culture in which lymphocytes, the cell population predominantly responsible for IFN-γ production, are maintained in a steady-state and their vitality is preserved. The IFN-γ production measured from the samples added with the maintenance medium and stored at 4 °C was similar to the enzyme-linked immunosorbent assay (ELISA) optical density values obtained from the same assay performed within 8 h from sampling.

Protective activity of Streptococcus pneumoniae Spr1875 protein fragments identified using a phage displayed genomic library.

There is considerable interest in pneumococcal protein antigens capable of inducing serotype-independent immunoprotection and of improving, thereby, existing vaccines. We report here on the immunogenic properties of a novel surface antigen encoded by ORF spr1875 in the R6 strain genome. An antigenic fragment encoded by spr1875, designated R4, was identified using a Streptococcus pneumoniae phage displayed genomic library after selection with a human convalescent serum. Immunofluorescence analysis with anti-R4 antisera showed that Spr1875 was expressed on the surface of strains belonging to different serotypes. Moreover, the gene was present with little sequence variability in 27 different pneumococcal strains isolated worldwide. A mutant lacking Spr1875 was considerably less virulent than the wild type D39 strain in an intravenous mouse model of infection. Moreover, immunization with the R4 recombinant fragment, but not with the whole Spr1875 protein, induced significant protection against sepsis in mice. Lack of protection after immunization with the whole protein was related to the presence of immunodominant, non-protective epitopes located outside of the R4 fragment. In conclusion, our data indicate that Spr1875 has a role in pneumococcal virulence and is immunogenic. As the R4 fragment conferred immunoprotection from experimental sepsis, selected antigenic fragments of Spr1875 may be useful for the development of a pneumococcal protein-based vaccine.

A surface protein of Streptococcus suis serotype 2 identified by proteomics protects mice against infection.

Streptococcus suis serotype 2 is a major Gram-positive swine pathogen, causing also zoonoses. We describe here the immunoprotective activity in an in vivo animal model of a serotype-2 cell wall protein, designated Sat, which was identified by a previously validated proteomics approach consisting of the protease digestion of live bacteria and the selective recovery of exposed domains, followed by LC/MS/MS analysis. Increased survival rate (80%) and decreased bacterial burden were observed in mice immunized with a recombinant Sat fragment, suggesting that this protein is a potential vaccine candidate against serotype-2 infection.

Immunoprotective activities of a Streptococcus suis pilus subunit in murine models of infection.

Pili of gram-positive bacteria are key virulence factors and their subunits are considered excellent vaccine candidates. Streptococcus suis is an emerging zoonotic agent that can cause epidemics of life-threatening infections in humans, but the functional role or immunoprotective potential of its pilus components have not been studied yet. Using a selective proteomics approach, we have identified a surface protein of serotype 2 S. suis showing features of an ancillary pilus subunit, as evidenced by bioinformatics analysis, immunoblot and immunoelectron microscopy. Immunization with recombinant fragments of this protein, designated herein as PAPI-2b, markedly protected mice from systemic S. suis infection.