with vehicle (PBS/Tween), vehicle plus -GC, or vehicle plus OCH. bone marrow chimeras were generated such that NKT cells were unable to express IL-4 or IFN. NKT-derived IL-4 was required for OCH-enhanced primary IgG1 responses but not recall responses. NKT-derived IL-4 and IFN also influenced primary and recall IgG2b and IgG2c titers. These data suggest targeted skewing of the Th2 response by -GC derivatives can be exploited to optimize anthrax vaccination. == Introduction == RR6 The protective Ag (PA) protein secreted byBacillus anthracisis an 83 kDa protein that forms heptameric pores on the surface of target cells expressing anthrax toxin receptors (capillary morphogenesis protein-2, CMG-2 and tumor endothelial marker-8,TEM-8)[1],[2]. PA heptamers interact with lethal factor (LF) and edema factor (EF) to form lethal toxin (LT) and edema toxin (ET), which together are referred to as anthrax toxin[2]. The PA heptamer facilitates entry of EF and LF into the target cell. Following cell entry, EF generates supra-physiological levels of cAMP via the protein’ calmodulin-dependent adenylate cyclase activity[3]. Within the intoxicated cell LF functions as a zinc-dependent metalloprotease and cleaves mitogen activated protein kinase kinases. LT can also activate the inflammasome in rodent models of intoxication[4]. Both toxins are lethal in animal models and cause a broad range of defects in target cells, including altered cell cycle, cell growth and survival, and attenuated inflammatory responses[5]. Collectively these activities of anthrax toxin cripple the host immune system and allowB. anthracisto grow to high numbers RR6 in the bloodstream[2],[6],[7],[8],[9]. Hence, immune neutralization of PA counters the damaging effects of anthrax toxin, providing protection to the host during early stages of disease. PA-specific Ab neutralizes LT and ET in vitro and protects immunized animals in vivo following a lethal challenge with the toxins[10],[11],[12],[13],[14],[15]. There is a good correlation between PA-specific Ab titers and toxin neutralization by sera from patients who have survivedB. anthracisinfection[16]. Consequently, there is considerable interest in development RR6 of vaccines which incorporate PA as the immunogen but involves fewer immunizations, boosts immunological memory and prolongs neutralizing Ab production while stimulating a RR6 minimal inflammatory response[16],[17]. The current AVA anthrax vaccine administered IL1R2 antibody to US military personnel consists of PA and induces PA-specific Ab titers sufficient to neutralize anthrax toxin[16],[17]. However, the Anti-PA Ab titers are not sustained and individuals require administration of multiple booster vaccines to maintain toxin-neutralizing Ab titers (http://www.anthrax.osd.mil/vaccine/schedule.asp#). Thus, there is a need for improving the efficacy of the current anthrax vaccine. Towards this effort, we recently demonstrated that activation of CD1d-restricted NKT cells with the CD1d-binding ligand (-galactosylceramide, -GC) at the time of immunization with PA led to enhanced and sustained Ab-mediated protection against anthrax lethal toxin[18]. Recent work by our laboratory and others has shown that NKT activation improves Ab responses against model and pathogen-derived Ags, suggesting that study of responses to anthrax could be useful for future application to other pathogens[19],[20],[21],[22],[23]. The mechanism by which -GC-activated NKT cells provide help to PA-specific B cells is not clear, and whether -GC represents the best choice of CD1d-binding adjuvant is also unknown. The -GC ligand consists of a galactose headgroup with an -anomeric linkage to hydrophobic sphingosine and acyl chains. The lipid moiety is loaded into hydrophobic pockets in the CD1d molecule expressed by professional Ag-presenting cells, orienting the galactose headgroup for recognition by NKT cells[24],[25]. The predominant NKT subset is represented by the Type I NKT cells which express an invariant V14, J18 TCR in mice and a V24, J28 TCR in humans[24],[25]. Type II NKT cells are CD1d-restricted, have variable V usage and are thought to be RR6 stimulated by a variety of self glycolipids rather than -GC[24],[25]. Several researchers are investing considerable effort in designing -GC-based molecules that have improved or more selective adjuvant effects than -GC. Those focused on vaccines for cancer and.
