Vaccines toxoid-based

Diphtheria and tetanus vaccines are two commonly used toxoid-based vaccine preparations. The initial stages of diphtheria vaccine production entail the growth of Corynebacterium diphtheriae. 

Diphtheria and tetanus vaeeine are two eommonly used toxoid-based vaccine preparations. The initial stages of diphtheria vaccine production entails the growth of Corynebacterium diphtheriae. The toxoid is then prepared by treating the active toxin produced with formaldehyde. The product is normally sold as a sterile aqueous preparation. Tetanus vaccine production follows a similar approach Clostridium tetani is cultured in appropriate media, the toxin is recovered and inactivated by formaldehyde treatment. Again, it is usually marketed as a sterile aqueous-based product. 

A potential problem with ricin toxoid immunization is that at least some preparations have shown a tendency to revert to the toxic form when stored at room temperature or 4°C (Griffiths et al, 1998). This has led to the examination of different vaccination candidates based upon ricin A chain (Griffiths et al, 1998). The challenge is to develop a ricin A chain derivative that is sufficiently immunogenic to be used as a vaccine without having the enzymatic activity of the complete ricin A chain molecule. 

Recently, a novel vaccine concept based on nanosized polymer-linked vaccines, has been explored. In particular tumor-associated MUCl glyco-peptides and T-cell epitope peptides were coupled to watersoluble methacrylamide polymers the subsequent attachment of the tetanus toxoid T-cell epitope P2 onto the hydrophilic polymer vaccines, causes their self-assembly to micelle-like nanoobjects. These novel polymer-based glycopeptide vaccines induced significant MHC-II-mediated immune reactions in mice and elicit IgG antibodies, which recognize breast tumor cells. 

Research on an hCG vaccine has been conducted over the past 15 years. WHO has conducted a phase I clinical study in AustraUa, using a vaccine based on a synthetic C-terminal peptide (109—141) of P-hCG conjugated to Diptheria Toxoid (CTP-DT), that showed potentially effective contraceptive levels of antibodies were produced in vaccinated women without any adverse side effects. Phase II clinical studies are under consideration to determine if the immune response, raised to its prototype anti-hCG vaccine, is capable of preventing pregnancy in fertile women volunteers (115). While research on the C-terminal peptide from the P-subunit of hCG has been carried out under the auspices of WHO, research supported by the Population Council and the National Institutes of Health has involved two alternative vaccine candidates (109,116,118). 

A human contraceptive vaccine based on lactide polymers is currently being developed. The antigen is a 37-amino-acid peptide of B-HCG conjugated to diphtheria toxoid. The antigen is administered wtih microencapsulated muramyl dipeptide as an adjuvant. Studies in rabbits have shown 9-12 months of elevated antibody liter following... 

Toxoids, antigen-based and other vaccine preparations... 

Recombinant techniques (Ogra et al. 2001) for generating purified antigens in large quantities have been used for the development of several vaccines including the hepatitis B virus vaccine (oral hepatitis B vaccine based on live recombinant adenovirus) (Lubeck et al. 1989). Other examples of recombinantly produced vaccines include vaccines containing tetanus toxoid, diphtheria toxin, and acellular pertussis toxoid. 

In children aged 15-16 years receiving routine reinforcement tetanus immunization, adsorbed vaccine caused more intense and more frequent local reactions than did plain tetanus toxoid, and a higher incidence of pjrexia. The incidence of swelling and erythema at the inoculation site increased with serum antitoxin titre at the time of administration, whereas pain and tenderness were related to the presence of the aluminium hydroxide adjuvant (17). Based on similar experiences it has been widely recommended that plain and not adsorbed tetanus toxoid should be used when reinforcement of immunity to tetanus alone is desired. 

The stability of vaccines was enhanced in several ways against destabilizing solvents and polymers. By careful selection of the PLGA copolymer composition and molecular weight, an oil (mineral oil)-based cores of tetanus toxoid surrounded by outer polymer shells (PLGA) potentially protecting the bioactive material against water-mediated inactivation processes. However, adjuvants such as trehalose, threonyl muramyl dipeptide, " BSA, - and PEG 400 can also be used for this purpose. 

Due to the limitations with the gastrointestinal tract, there are few studies available on chitosan-based delivery systems for oral vaccine delivery (Table 1). Van der Lubben et al. [66] were among the first to demonstrate that chitosan microparticles with a particle size smaller than 10 pm, incorporated with the model protein OVA as well as diphtheria toxoid (DT), were taken up by the Peyer s patch after intragastric administration to mice. A dose-dependent immune reaction was observed for mice vaccinated with different doses of DT associated to chitosan microparticles [67]. It was also observed that the immune response started only 1 week after the boosting, indicating the formation of memory cells after priming. 

A bivalent P. damselae subsp. piscicida (RPS = -88%) and V. harveyi (RPS = -82%) vaccine based on formalized cells and ECP was administered by i.p. injection or immersion with booster dose to sole, and led to commendable protection for 4 months after which there was a decline in effectiveness (Arijo et al., 2005). Toxoid enriched inactivated whole cells of P. damselae subsp. piscicida applied by immersion led to a RPS of 37-41% and a low antibody response in sea bream (Magarinos et al., 1994). An improved RPS of >60% after 35 days resulted from use of an LPS mixed chloroform-killed whole cell vaccine (Kawakami et al., 1997). 

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