Availability of autoantigenic epitopes controls phenotype, severity, and penetrance in TCR Tg autoimmune gastritis.

We examined TCR:MHC/peptide interactions and in vivo epitope availability to explore the Th1- or Th2-like phenotype of autoimmune disease in two TCR Tg mouse models of autoimmune gastritis (AIG). The TCR of strains A23 and A51 recognize distinct IA(d)-restricted peptides from the gastric parietal cell H/K-ATPase. Both peptides form extremely stable MHC/peptide (MHC/p) complexes. All A23 animals develop a Th1-like aggressive, inflammatory AIG early in life, while A51 mice develop indolent Th2-like AIG at 6-8 wk with incomplete penetrance. A51 T cells were more sensitive than A23 to low doses of soluble antigen and to MHC/p complexes. Staining with IA(d)/peptide tetramers was only detectable on previously activated T cells from A51. Thus, despite inducing a milder AIG, the A51 TCR displays a higher avidity for its cognate IA(d)/peptide. Nonetheless, in vivo proliferation of adoptively transferred A51 CFSE-labeled T cells in the gastric lymph node was relatively poor compared with A23 T cells. Also, DC from WT gastric lymph node, presenting processed antigen available in vivo, stimulated proliferation of A23 T cells better than A51. Thus, the autoimmune potential of these TCR in their respective Tg lines is strongly influenced by the availability of the peptide epitope, rather than by differential avidity for their respective MHC/p complexes.

Streptococcus pneumoniae fructose-1,6-bisphosphate aldolase, a protein vaccine candidate, elicits Th1/Th2/Th17-type cytokine responses in mice.

Streptococcus pneumoniae (S. pneumoniae) is a major pathogen worldwide. The currently available polysaccharide-based vaccines significantly reduce morbidity and mortality. However, the inherent disadvantages of the currently available polysaccharide-based vaccines have motivated the search for other bacterial immunogens capable of eliciting a protective immune response against S. pneumoniae. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic enzyme, which was found to localize to the bacterial surface, where it functions as an adhesin. Previously, immunizing mice with recombinant FBA (rFBA) in the presence of alum elicited a protective immune response against a lethal challenge with S. pneumoniae. Thus, the aim of the present study was to determine the cytokine responses that are indicative of protective immunity following immunization with rFBA. The protective effects against pneumococcal challenge in mice immunized with rFBA with complete Freund's adjuvant (CFA) in the initial immunization and with incomplete Freund's adjuvant (IFA) in booster immunizations surpassed the protective effects observed following immunization with either rFBA + alum or pVACfba. CD4+ T-cells obtained from the rFBA/CFA/IFA/IFA-immunized mice co-cultured with rFBA-pulsed antigen-presenting cells (APCs), exhibited a significantly greater proliferative ability than CD4+ T-cells obtained from the adjuvant-immunized mice co-cultured with rFBA­pulsed APCs. The levels of the Th1-type cytokines, interferon (IFN)-γ, interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-12, the Th2-type cytokines, IL-4, IL-5 and IL-10, and the Th17-type cytokine, IL-17A, significantly increased within 72 h of the initiation of co-culture with CD4+ T-cells obtained from the rFBA­immunized mice, in comparison with the co-cultures with CD4+ T-cells obtained from the adjuvant-immunized mice. Immunizing mice with rFBA resulted in an IgG1/IgG2 ratio of 41, indicating a Th2 response with substantial Th1 involvement. In addition, rabbit and mouse anti-rFBA antisera significantly protected the mice against a lethal S. pneumoniae challenge in comparison with preimmune sera. Our results emphasize the mixed involvement of the Th1, Th2 and Th17 arms of the immune system in response to immunization with pneumococcal rFBA, a potential vaccine candidate.

Fc fusion as a platform technology: potential for modulating immunogenicity.

The platform technology of fragment crystallizable (Fc) fusion, in which the Fc region of an antibody is genetically linked to an active protein drug, is among the most successful of a new generation of bioengineering strategies. Immunogenicity is a critical safety concern in the development of any protein therapeutic. While the therapeutic goal of generating Fc-fusion proteins has been to extend half-life, there is a critical mass of literature from immunology indicating that appropriate design of the Fc component has the potential to engage the immune system for product-specific outcomes. In the context of Fc-fusion therapeutics, a review of progress in understanding Fc biology suggests the prospect of engineering products that have an extended half-life and are able to modulate the immune system.