Regulation of Anthrax Toxin-Specific Antibody Titers by Natural Killer T Cell-Derived IL-4 and IFNγ

Abstract

Activation of Natural Killer-like T cells (NKT) with the CD1d ligand α-GC leads to enhanced production of anthrax toxin protective Ag (PA)-neutralizing Abs, yet the underlying mechanism for this adjuvant effect is not known. In the current study we examined the role of Th1 and Th2 type responses in NKT-mediated enhancement of antibody responses to PA. First, the contribution of IL-4 and IFNγ to the production of PA-specific toxin-neutralizing Abs was examined. By immunizing C57Bl/6 controls IL-4−/− mice and IFNγ−/− mice and performing passive serum transfer experiments, it was observed that sera containing PA-specific IgG1, IgG2b and IgG2c neutralized toxin in vitro and conferred protection in vivo. Sera containing IgG2b and IgG2c neutralized toxin in vitro but were not sufficient for protection in vivo. Sera containing IgG1 and IgG2b neutralized toxin in vitro and conferred protection in vivo. IgG1 therefore emerged as a good correlate of protection. Next, C57Bl/6 mice were immunized with PA alone or PA plus a Th2-skewing α-GC derivative known as OCH. Neutralizing PA-specific IgG1 responses were modestly enhanced by OCH in C57Bl/6 mice. Conversely, IgG2b and IgG2c were considerably enhanced in PA/OCH-immunized IL-4−/− mice but did not confer protection. Finally, bone marrow chimeras were generated such that NKT cells were unable to express IL-4 or IFNγ. NKT-derived IL-4 was required for OCH-enhanced primary IgG1 responses but not recall responses. NKT-derived IL-4 and IFNγ also influenced primary and recall IgG2b and IgG2c titers. These data suggest targeted skewing of the Th2 response by α-GC derivatives can be exploited to optimize anthrax vaccination.

CD40L-null NKT cells provide B cell help for specific antibody responses

“…The chimeras also had equivalent re-constitution of donor-derived NKT cells and expression of CD1d (Figure 2D). Re-constitution of NKT cells to the frequency observed in C57Bl/6 mice did not occur, but intact function and ability to enhance Ab responses has been demonstrated by our group [17]. …”

“…Using a similar mixed bone marrow chimera approach to that described herein, we were unable to assign a contribution to the inducible co-stimulator (ICOS) molecule (data not shown) , or to NKT-derived IL-4 or IFNγ [17]. ICOS-blocking mAbs were administered to the Jα18 −/− /C57Bl/6 and the Jα18 −/− /CD40L −/− chimeras since ICOS −/− mice are NKT-deficient.…”

Glycan surface antigens fromBacillus anthracisas vaccine targets: current status and future perspectives

“…Among the identified glycans, the cell wall polysaccharide possesses the characteristics of surface exposure and specificity in respect to other bacilli that would render it amenable for vaccine development. rPA in combination with TLR4a CIA05 Novel adjuvants [91] AVA adjuvanted with CpG oligonucleotides [92] PA adjuvanted with alum [93] PA adjuvanted with a-gal ceramide [94] PA and immune-enhancing cytokine IL-15 [95] Microsphere Novel delivery systems [96] Nanoemulsions [97] Nanoparticles [98] rAAV1…”

Critical Role of NKT Cells in Posttransplant Alloantibody Production

“…Reports by others also show a role for NKT cells in antibody production. However, the majority of these reports have occurred in the context of NKT cell activation by exogenous administration of α-GalCer (25, 26, 30-33, 54, 55) or other exogenous glycolipids including OCH (56), which is a glycolipid known to skew conditions toward Th2 conditions (57). Thus, another novel aspect of the current study is NKT-mediated enhancement of in vivo antibody production without concurrent exogenous glycolipid administration to activate NKT cells.…”