Oligosaccharides (OSs) related to the pneumococcal type 14 capsular polysaccharide (Pn14PS) were studied for their ability to inhibit the binding between anti-PS14 antisera and native PS14. A synthetic tetrasaccharide corresponding to the repeating unit of the Pn14PS, a hexasaccharide mimic, and an octasaccharide fragment obtained by Pn14PS depolymerization were good inhibitors. CRM197 conjugates of the tetrasaccharide and an octasaccharide mimic were prepared by using either adipic acid diester or diethyl squarate linkers. The conjugate with the tetrasaccharide chains induced anti-Pn14PS antibodies when injected subcutaneously into mice, as determined by an enzyme-linked immunosorbent assay, and antibody titers increased with oligosaccharide loading. The adipic acid-linked tetrasaccharide conjugates elicited higher antibody titers than those prepared with a squarate spacer. The lower anti-Pn14PS antibody response of the octasaccharide mimic conjugate indicates the importance of the backbone galactose residue for an appropriate antibody response. The OS-CRM197 conjugate prepared from a single repeat unit of the Pn14PS is a potential vaccine candidate.Streptococcus pneumoniae is a major cause of morbidity and mortality in children and adults in both industrialized and developing countries (10). Although the licensed 14-and 23-valent pneumococcal capsular polysaccharide (PnPS) vaccines are safe and effective in reducing the incidence of invasive disease in healthy adults (5, 24), they are weakly immunogenic in children less than 2 years old and in the elderly, the two groups at highest risk (8,22,25,31). Whereas PSs are T-cellindependent immunogens, conjugates in which the PS is covalently attached to a protein carrier elicit a T-cell-dependent antisaccharide response even in infants, as evidenced by a booster effect upon subsequent immunizations. A number of PnPS serotypes have been conjugated to various carrier proteins and have been shown to be immunogenic and protective in various animal models (13,20,30) and in humans (1, 32). Intact PS, small oligosaccharides (OSs), or OSs of undefined length have been used to prepare those conjugates (3, 13, 36). The capsular polysaccharide of S. pneumoniae type 14 (Fig. 1) consists of a branched tetrasaccharide repeating unit (21) which is identical to the asialo core antigen of the type III group B Streptococcus PS (38). The poor immunogenicity of the Pn14PS compared to other PnPSs (18) may be due to structural similarities between antigenic determinants of the Pn14PS and human OS structures (e.g., human milk OSs and blood group carbohydrate structures). To avoid cross-reactivity with human tissue and the induction of autoreactive antibodies (6), we have been investigating the synthesis of well-defined OS fragments (26,27) corresponding to the Pn14PS to enable specific protective epitopes to be defined. Inhibition studies were performed both with synthetic OS structures and fragments from PS degradation to determine optimal OSs for conjugation. The protein carrier used in...

Mucosal immunity is considered important for protection against Clostridium difficile infection (CDI). We show that in hamsters immunized with Bacillus subtilis spores expressing a carboxy-terminal segment (TcdA 26 -39 ) of C. difficile toxin A, no colonization occurs in protected animals when challenged with C. difficile strain 630. In contrast, animals immunized with toxoids showed no protection and remained fully colonized. Along with neutralizing toxins, antibodies to TcdA 26 -39 (but not to toxoids), whether raised to the recombinant protein or to TcdA 26 -39 expressed on the B. subtilis spore surface, cross-react with a number of seemingly unrelated proteins expressed on the vegetative cell surface or spore coat of C. difficile. These include two dehydrogenases, AdhE1 and LdhA, as well as the CdeC protein that is present on the spore. Anti-TcdA 26 -39 mucosal antibodies obtained following immunization with recombinant B. subtilis spores were able to reduce the adhesion of C. difficile to mucus-producing intestinal cells. This cross-reaction is intriguing yet important since it illustrates the importance of mucosal immunity for complete protection against CDI.

Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1alpha (IL-1alpha), and interferon-gamma (IFN-gamma) were estimated by conventional ELISA kits in 60, 42, and 58 Thai patients, respectively, with beta(o)-thalassemia HbE and found to be above the normal range in 13%, 21%, and 33% of the patients, respectively. Using high-sensitivity ELISA systems, an additional 10 beta(o)-thal/HbE patients were compared with 9 controls for concentrations of circulating TNF-alpha and IL-1beta, and 9 and 5 patients, respectively, but only 1 and none of the controls, respectively, showed values above the normal ranges. In patients with abnormally high IFN-gamma levels, basal hemoglobin values were significantly lower than in those with normal levels of the cytokine (mean +/- SEM: 6.03+/-0.24 vs. 7.08+/-0.18, p < 0.05), although circulating concentrations of soluble transferrin receptors (sTrF) and absolute reticulocyte counts were similar in the two groups. Patients with raised or normal levels of TNF-alpha, IL-1alpha, or IL-1beta had similar basal hemoglobin values. In a phagocytosis assay, monocytes of patients with raised serum levels of IFN-gamma showed significantly more attached or ingested IgG-coated red cells than those of patients with normal concentrations of the cytokine (mean +/- SEM: 192+/-22 vs. 140+/-14 per 100 monocytes, p < 0.05). Moreover, in 3 of 4 of the former patients, the number of attached or ingested IgG-coated red cells per 100 monocytes was above the 95% reference limit for the latter patients. The results suggest that IFN-gamma aggravates the anemia of beta(o)-thal/HbE by activating mononuclear phagocytes for destruction of red cells but not by inhibiting erythropoiesis. The elevated serum levels of TNF-alpha and IL-1 could contribute to complications of the disease, such as cachexia and thromboembolic phenomena.

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