Amphoteric Mannan as an Immune Response Modifier. New Model Immunobiologically Active Candida albicans Mannan-Based Formula.

BACKGROUND: Currently, the incidence and prevalence of serious fungal infections is increasing, especially in immunosuppressed individuals. The co-administration of antibiotic and immunosuppressive therapies has driven the emergence of new multidrug-resistant fungal pathogens. Their significant increase and their ability to form biofilms is associated with rising morbidity and mortality. Research into novel synthetically prepared immunomodulators as potential immune response modifiers and prospective participants in drug delivery systems is of interest. Microbial polysaccharides with zwitterionic charge motifs were shown to be promising candidates. METHODS: Native and ultrasonically treated mannan from the yeast Candida albicans were chemically modified to contain both positive and negative charges in a nearly equimolar ratio mimicking the zwitterionic polysaccharides. RAW 264.7 macrophages and Balb/c mice were subjected as in vitro and in vivo models. Macrophage exposure to the set of amphoteric derivatives of mannan induced a release of Th1, Th2, Th17, and Treg cytokine signature patterns. The functionality of the exposed macrophages was assayed by cell proliferation and phagocytosis. RESULTS: The Th1 and Th17 dominance was over Th2. The phagocytosis and respiratory burst, together with the viability based on cell proliferation supported the bioavailability of formulas. Mouse immunization induced humoral immune responses with high titers of the IgM isotype with the IgM/IgG shift. CONCLUSION: Our study demonstrated the immunobiological activities of amphoteric derivatives of mannan from Candida albicans. Amphoteric derivatives can be considered as bioavailable formulas with an effective immunomodulatory potency, prospectively applied as a subunit formula in the design of a mannan-based platform for drug and vaccine delivery systems.

Molar-mass-dependent antibacterial activity of cationic dextran derivatives against resistant nosocomial pathogens.

The rise of various multidrug-resistant bacteria has created a need for new biocompatible and biodegradable antibacterial compounds. Cationic polysaccharides are promising candidates for this role. Therefore, cationic derivatives of commercial dextrans with molar masses of 11 kDa, 76 kDa, 411 kDa, and 1500-2500 kDa and various degrees of substitution (DSQ 0.34-0.52) were prepared and their antimicrobial properties against four gram-negative nosocomial bacteria were tested. As expected, a higher DSQ led to higher efficiency. The best antimicrobial properties were found for derivatives of 411 kDa, followed by 76 kDa and 1500-2000 kDa dextrans. This indicates that there is a certain optimum molar mass with the best antimicrobial properties. However, as molar mass increased, the biocompatibility of cationic dextran steadily decreased, with increased hemagglutination and toxicity being seen for human cells. The derivatives of 76 kDa dextran with higher DSQ (0.40-0.52) were the best antimicrobial agents suitable for further clinical testing.

Comparison of O-specific polysaccharide responses in patients following infection with Vibrio cholerae O139 versus vaccination with a bivalent (O1/O139) oral killed cholera vaccine in Bangladesh.

Cholera caused by Vibrio cholerae O139 emerged in the early 1990s and spread rapidly to 11 Asian countries before receding for unclear reasons. Protection against cholera is serogroup-specific, which is defined by the O-specific polysaccharide (OSP) component of lipopolysaccharide (LPS). V. cholerae O139 also expresses the OSP-capsule. We, therefore, assessed antibody responses targeting V. cholerae O139 OSP, LPS, capsule, and vibriocidal responses in patients in Bangladesh with cholera caused by V. cholerae O139. We compared these responses to those of age-gender-blood group-matched recipients of the bivalent oral cholera vaccine (OCV O1/O139). We found prominent OSP, LPS, and vibriocidal responses in patients, with a high correlation between these responses. OSP responses primarily targeted the terminal tetrasaccharide of OSP. Vaccinees developed OSP, LPS, and vibriocidal antibody responses, but of significantly lower magnitude and responder frequency (RF) than matched patients. We separately analyzed responses in pediatric vaccinees born after V. cholerae O139 had receded in Bangladesh. We found that OSP responses were boosted in children who had previously received a single dose of bivalent OCV 3 yr previously but not in vaccinated immunologically naïve children. Our results suggest that OSP-specific responses occur during cholera caused by V. cholerae O139 despite the presence of capsules, that vaccination with bivalent OCV is poorly immunogenic in the short term in immunologically naïve individuals, but that OSP-specific immune responses can be primed by previous exposure, although whether such responses can protect against O139 cholera is uncertain. IMPORTANCE Cholera is a severe dehydrating illness in humans caused by Vibrio cholerae serogroups O1 or O139. Protection against cholera is serogroup-specific, which is defined by the O-specific polysaccharide (OSP) of V. cholerae LPS. Yet, little is known about immunity to O139 OSP. In this study, we assessed immune responses targeting OSP in patients from an endemic region with cholera caused by V. cholerae O139. We compared these responses to those of the age-gender-blood group-matched recipients of the bivalent oral cholera vaccine. Our results suggest that OSP-specific responses occur during cholera caused by V. cholerae O139 and that the OSP responses primarily target the terminal tetrasaccharide of OSP. Our results further suggest that vaccination with the bivalent vaccine is poorly immunogenic in the short term for inducing O139-specific OSP responses in immunologically naïve individuals, but OSP-specific immune responses can be primed by previous exposure or vaccination.

Fragmentation analysis of O-specific polysaccharide from bacteria Vibrio cholerae O139 by MALDI-TOF and LC/ESI-MS/MS.

Cholera is a life-threatening diarrhoeal disease caused by ingestion of Vibrio cholerae. There are at least 200 serogroups of V. cholerae but only two of them are causing epidemics - O1 and O139 serogroups. Fragmentation analysis of O-antigen, also known as O-specific polysaccharide (OSP), from lipopolysaccharide (LPS) is important to obtain new information about its structure, such as fragmentation patterns and fragment structures. In the present study, OSP and core (OSPc) structure from V. cholerae O139 was studied using matrix-assisted laser desorption ionization (MALDI)-time of flight (TOF) and direct injection electrospray ionization (ESI)-MS methods. MALDI-TOF analysis was performed in positive-ion reflectron mode, while ESI-MS was performed in negative ionization mode. ESI-MS analysis was followed by ESI-MS/MS analysis. Using this analytical approach, we managed to obtain two possible fragmentation pathways of OSP from V. cholerae O139. Mutual sign of these two pathways is shortening the length of the oligosaccharide by neutral loss of monosaccharide residues. Additionally, liquid chromatography-MS analysis was performed to separate depicted molecular forms of OSPc.

Defining Polysaccharide-Specific Antibody Targets against Vibrio cholerae O139 in Humans following O139 Cholera and following Vaccination with a Commercial Bivalent Oral Cholera Vaccine, and Evaluation of Conjugate Vaccines Targeting O139.

Cholera caused by Vibrio cholerae O139 could reemerge, and proactive development of an effective O139 vaccine would be prudent. To define immunoreactive and potentially immunogenic carbohydrate targets of Vibrio cholerae O139, we assessed immunoreactivities of various O-specific polysaccharide (OSP)-related saccharides with plasma from humans hospitalized with cholera caused by O139, comparing responses to those induced in recipients of a commercial oral whole-cell killed bivalent (O1 and O139) cholera vaccine (WC-O1/O139). We also assessed conjugate vaccines containing selected subsets of these saccharides for their ability to induce protective immunity using a mouse model of cholera. We found that patients with wild-type O139 cholera develop IgM, IgA, and IgG immune responses against O139 OSP and many of its fragments, but we were able to detect only a moderate IgM response to purified O139 OSP-core, and none to its fragments, in immunologically naive recipients of WC-O1/O139. We found that immunoreactivity of O139-specific polysaccharides with antibodies elicited by wild-type infection markedly increase when saccharides contain colitose and phosphate residues, that a synthetic terminal tetrasaccharide fragment of OSP is more immunoreactive and protectively immunogenic than complete OSP, that native OSP-core is a better protective immunogen than the synthetic OSP lacking core, and that functional vibriocidal activity of antibodies predicts in vivo protection in our model but depends on capsule thickness. Our results suggest that O139 OSP-specific responses are not prominent following vaccination with a currently available oral cholera vaccine in immunologically naive humans and that vaccines targeting V. cholerae O139 should be based on native OSP-core or terminal tetrasaccharide. IMPORTANCE Cholera is a severe dehydrating illness of humans caused by Vibrio cholerae serogroup O1 or O139. Protection against cholera is serogroup specific, and serogroup specificity is defined by O-specific polysaccharide (OSP). Little is known about immunity to O139 OSP. In this study, we used synthetic fragments of the O139 OSP to define immune responses to OSP in humans recovering from cholera caused by V. cholerae O139, compared these responses to those induced by the available O139 vaccine, and evaluated O139 fragments in next-generation conjugate vaccines. We found that the terminal tetrasaccharide of O139 is a primary immune target but that the currently available bivalent cholera vaccine poorly induces an anti-O139 OSP response in immunologically naive individuals.