Mucosal immunogenicity of polysaccharides conjugated to a peptide or multiple-antigen peptide containing T- and B-cell epitopes

A comprehensive and critical overview of schistosomiasis vaccine candidates

A digenetic platyhelminth Schistosoma is the causative agent of schistosomiasis, one of the neglected tropical diseases that affect humans and animals in numerous countries in the Middle East, sub-Saharan Africa, South America and China. Several control methods were used for prevention of infection or treatment of acute and chronic disease. Mass drug administration led to reduction in heavy-intensity infections and morbidity, but failed to decrease schistosomiasis prevalence and eliminate transmission, indicating the need to develop anti-schistosome vaccine to prevent infection and parasite transmission. This review summarizes the efficacy and protective capacity of available schistosomiasis vaccine candidates with some insights and future prospects.

Conjugation of a peptide to mannan and its confirmation by tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis

The conjugation of polysaccharides to peptides is essential for antigen delivery and vaccine development. Herein, we show that tricine SDS-PAGE in combination with Coomassie Blue staining was adequate to determine the conjugation efficacy of a peptide (epitope 35-55 of myelin oligodendrocyte glycoprotein) to mannan. In addition, tricine SDS-PAGE and periodic acid-Schiff stains were able to monitor the redox state of mannan. Using the described protocol, more than 99.9% of a peptide containing five lysines at its N-terminus was confirmed conjugated to mannan.

Dental caries vaccines: prospects and concerns

Dental caries remains one of the most common infectious diseases of mankind. Cariogenic micro-organisms enter the dental biofilm early in life and can subsequently emerge, under favorable environmental conditions, to cause disease. In oral fluids, adaptive host defenses aroused by these infections are expressed in the saliva and gingival crevicular fluid. This review will focus on methods by which mucosal host defenses can be induced by immunization to interfere with dental caries caused by mutans streptococci. The natural history of mutans streptococcal colonization is described in the context of the ontogeny of mucosal immunity to these and other indigenous oral streptococci. Molecular targets for dental caries vaccines are explored for their effectiveness in intact protein and subunit (synthetic peptide, recombinant and conjugate) vaccines in pre-clinical studies. Recent progress in the development of mucosal adjuvants and viable and non-viable delivery systems for dental caries vaccines is described. Finally, the results of clinical trials are reviewed, followed by a discussion of the prospects and concerns of human application of the principles presented.

Immunoadjuvant activity of interferon-gamma-liposomes co-administered with influenza vaccines

In an attempt to potentiate the relatively low immunogenicity of the currently used influenza vaccines, especially in high-risk groups, monovalent and divalent subunit vaccine preparations were co-administered with free or liposome-associated murine interferon gamma (mIFNgamma) as an adjuvant. Recombinant murine IFNgamma was entrapped (50-70% efficiency) in two types of large multilamellar vesicles: mIFNgamma-LIP A-'conventional' liposomes, and mIFNgamma-LIP B- 'surface-depleted' liposomes, in which 60 and 8% of the associated cytokine was located at the external liposome membrane, respectively. Subunit preparations containing the viral surface proteins hemagglutinin and neuraminidase (HN) were injected once, i.p. (0.5 microg each), into BALB/c mice, alone and combined with free or liposomal mIFNgamma (mIFNgamma-LIP, 0.5 or 3.0 microg). Sera were tested 3-16 weeks post-vaccination by hemagglutination inhibition (HI), and by ELISA for IgG1 and IgG2a antibodies (Abs). In addition, protective immunity against intranasal viral infection was assayed at 11 and 17 weeks post-vaccination. The results showed that: (a) Vaccination with HN alone produces very low HI and IgG titers and does not afford any protection. (b) Although co-administration with free mIFNgamma (particularly using 3.0 microg) markedly enhances HI titer as well as the IgG1 and IgG2a levels, protection is negligible (0-33%). (c) In most cases, mIFNgamma-LIP is significantly more potent than free mIFNgamma (2-40-fold increase in Ab titer), and the low dose (0.5 microg) is generally more efficient than the high dose. Up to 83% of the mice co-vaccinated with mIFNgamma-LIP were protected against viral challenge. (d) Both the IgG2a level and the HI titer appear to be crucial for protection. (e) Although the two liposomal preparations differ in their cytokine release profile in vivo and in their bioactivity in vitro, their adjuvant activity is comparable.

Short synthetic glycopeptides successfully induce antibody responses to carcinoma-associated Tn antigen

Glycopeptides containing a tumor-associated carbohydrate antigen (mono-, tri- or hexa-Tn antigen) as a B-cell epitope and a CD4+ T-cell epitope (PV: poliovirus or TT: tetanus toxin) were prepared for immunological studies. Several Tn antigen residues [FmocSer/Thr (alpha-GalNAc)-OH] were successively incorporated into the peptide sequence with unprotected carbohydrate groups. The tri- and hexa-Tn glycopeptides were recognized by MLS128, a Tn-specific monoclonal antibody. The position of the tri-Tn motif in the peptide sequence and the peptide backbone itself do not alter its antigenicity. As demonstrated by both ELISA and FACS analysis, the glycopeptides induced high titers of anti-Tn antibodies in mice, in the absence of a carrier molecule. In addition, the generated antibodies recognized the native Tn antigen on cancer cells. The antibody response obtained with a D-(Tn3)-PV glycopeptide containing three alpha-GalNAc-D-serine residues is similar that obtained with the Tn6-PV glycopeptide. These results demonstrate that short synthetic glycopeptides are able to induce anticancer antibody responses.

Oral immunization with a Streptococcal pneumoniae polysaccharide conjugate vaccine in enterocoated microparticles induces serum antibodies against type specific polysaccharides

The authors examined the antibody responses of mice orally immunized with pneumococcal polysaccharide (type 23F) or a pneumococcal polysaccharide conjugated to the outer membrane protein complex of Neisseria meningitides (23F-OMPC). These antigens were administered either in solution or entrapped within microcapsules. Only the mice receiving the encapsulated conjugate vaccine produced significant levels of anti-polysaccharide serum antibodies. These responses, observed after a second oral immunization with the conjugate, were predominantly IgG. Thus, the conversion from a T-cell-independent to a T-cell dependent response, achieved through conjugation was maintained following oral delivery. However, no local secretory IgA anti-polysaccharide response was detected in these mice indicating that while the OMPC carrier augments orally induced IgG responses, it was insufficient for the induction of secretory IgA.

[Immunologic behavior of meningococcal vaccines]

Meningococcal disease continues to be a great health problem on all continents and the meningococcal vaccines have been proposed for their prevention and epidemic control. The polysaccharide A and C vaccines are relatively efficacious with distinct immunological behavior with regard to the different age groups, however, up to the present no highly efficacious vaccine for meningococcal B disease exists. The meningococcal B capsular polysaccharide is not immunogenic due to the structural mimicry of mammalian tissues and efforts to produce carrier proteins have been proposed in order to obtain an immunogenic vaccine for all age groups that would if possible, protect against all the meningococci. This review of the literature presents the study of the development of the immunological behavior of all the meningococcal vaccines undergoing development and reports on the efforts to obtain a safe and efficacious product for the control of meningococcal disease.

Preparation of a multiple antigen glycopeptide (MAG) carrying the Tn antigen. A possible approach to a synthetic carbohydrate vaccine

The glycosidic tumor-associated Tn antigen was conjugated to a lysine backbone containing a helper T-cell epitope in order to activate immune responses specific for some types of carcinomas. As opposed to traditional protein conjugates, this multiple antigen glycopeptide (MAG) offers the advantages of the lack of immunogenicity of the polylysine core and of accurate chemical definition. The MAG construction was assembled by conventional solid-phase peptide synthesis. The analysis of its antigenicity demonstrated that the Tn antigen on the MAG is recognized by Tn-specific monoclonal antibodies.

Protection against generalized autoimmunity of the nervous system (GANS), a novel animal model with combined features of EAE, EAN and EAU by a recombinant HIV-1 Tat37-72 peptide-based multiple T cell epitope vaccine

A new model of multi-compartment auto-immune disease has been established to analyze the effects of polyvalent recombinant peptide vaccines. A synthetic gene encoding major pathogenic determinants for Lewis rats of guinea pig myelin basic protein (MBP68-84), bovine interphotoreceptor retinoid binding protein (IRBP1169-1191), and bovine P2 protein (P2,53-78) was used to induce Generalized Autoimmunity of the Nervous System (GANS), which is characterized by development of auto-immune infiltration of the brain and spinal cord, the eyes, the pineal organ and the peripheral nerves. Thus, this model integrates the prominent features of three auto-immune diseases: experimental autoimmune encephalomyelitis (EAE), neuritis (EAN) and uveitis (EAU). In this study, GANS was used to study the effect of HIV-1 Tat37-72 targeting peptide on vaccination by recombinant polyvalent T cell auto-antigen vaccine. Depending on the route of administration, the recombinant vaccine effectively protects against the development of auto-immune nervous system inflammation.

Persistence of serum and salivary antibody responses after oral immunization with a bacterial protein antigen genetically linked to the A2/B subunits of cholera toxin

Primary oral immunization of mice with a bacterial protein antigen genetically coupled to the A2 and B subunits of cholera toxin induced specific secretory immunoglobulin A and serum immunoglobulin G antibodies that persisted at substantial levels for at least 11 months. A subsequent single booster immunization did not further enhance the antibody responses. Long-term antibody persistence may be especially important in infections caused by common pathogens for which continuous immunity would be advantageous.