Immunogenic activity

Jiskoot, W., Teerlink, T., Van Hoof, M. M. M., Bartels, K., Kanhai, V., CrommeUn, D. J. A., and Beuvery, E. C. (1986b). Immunogenic activity of gonococcal protein I in mice with three different lipoidal adjuvants delivered in liposomes and in complexes, Inf. Immun.. 54. 333-338. 

Martinez C, Dalsgaard K, Lopez de Turiso JA, Cortes E, Vela C, Casal JI (1992), Production of porcine parvovirus empty capsids with high immunogenic activity, Vaccine 10 684-690. 

The insect baculovirus-cell system has been widely used, mainly for the production of recombinant proteins (Maiorella et al., 1988 Jarvis, 1997). This system has several advantages, including the ability to produce functional recombinant proteins that are immunogenically active, the ability to make post-translation modifications, and the fact that it contains a powerful promoter (polyhedrin), as well as the fact that the virus is not pathogenic to plants and vertebrates (Caron et al., 1990 Nguyen et al., 1993 Godwin et al., 1996). 

Some key aspects have to be considered when designing such synthetic vaccines because the immunogenic activity of the conjugate depends on the nature of the hapten, the loading onto the protein, and the characteristics of the carrier. In... 

Screening and selection of the source plasma will only avoid contamination by known pathogens. The protein purification steps and specific virus reduction methods used in production processes, however, will inactivate and/or remove both known and unknown viruses. Terminal virus inactivation treatments are applied to product in final container and must balance virus inactivation with any modifications to protein immunogenicity, activity, and yield. While many upstream virus inactivation steps rely on chemical methods that involve the addition and subsequent removal of toxic agents (e.g., solvent/detergent), physical methods for virus inactivation, such as pH and heat, are used for terminal steps. 

The complexation behaviour of proteins with dilute solutions of PAA and a random polyampholyte DMAEM-AA-MM A was studied by turbidimetric titration [87]. Polyampholyte-polyampholyte interaction (self-aggregation) and polyampholyte-protein complexation was studied as a function of pH and polymer dosage. Large increases in turbidity were observed for polyampholyte-protein mixtures compared with polyampholyte alone. However, protein analysis of the supernatant and precipitate revealed that only about 10% of the protein precipitates with the random polyampholyte while 90% of the protein remains in the equilibrium liquid. An experiment with PAA and oppositely charged protein shows the opposite trend with 90% precipitation of protein. Hence, great care needs to be taken in the interpretation of turbidimetric titration data. It has been reported that polyampholyte-protein associates behave with lowered immunogenic activity [88]. 

Because synthetic peptides are routinely assembled as short monomers representing individual epitopes, they may lack immunogenic activity either because they do not contain appropriate helper T-cell epitopes or conformational integrity is lacking in the B-cell epitope in addition they may be rapidly metabolised before having a chance to initiate an immune response. In many cases one or more of these factors contribute to the poor immunogenicity often observed with synthetic peptides. The rest of this chapter will address some of the recent improvements in peptide vaccine technology that have been used to advance the development of synthetic peptide-bas ed vaccines. 

The active immunotherapeutic approach is specific and based on the premise that tumor antigens are immunogenic and the host is sufficientiy immunocompetent to mount an effective immune response to an autologous tumor. Theoretically, a weak or suppressed host immune system that had allowed the formation of a tumor may be overridden by active immunization or immunostimulation. In practice, vaccines composed of so-called autologous tumor extracts have been used to treat patients with malignant melanoma (73), and purified melanoma tumor-associated antigens have been used to ehcit antibody responses in melanoma patients (74). 

In the early 1900s, a balanced mixture of diphtheria toxin and antitoxin was found to produce active immunity in both animals and humans. This preparation gained widespread acceptance and protected approximately 85% of recipients. Several years later, diphtheria toxoid was developed by treating the toxin with small amounts of formalin. This process caused the toxin to lose its toxic properties while maintaining its immunogenic properties. In the mid-1920s, the addition of an alum precipitate enhanced the immunogenic properties of the toxoid. 

Bacterial polysaccharides were activated with CDI and then coupled via spacers to immunogenic membrane proteins.[133],[134]... 

The reactions involved in an EDC-mediated conjugation are discussed in Chapter 3, Section 1.1 (Note EDC is l-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride MW 191.7 and is sometimes referred to as EDAC). The carbodiimide first reacts with available carboxylic groups on either the carrier or hapten to form a highly reactive o-acylisourea intermediate. The activated carboxylic group then can react with a primary amine to form an amide bond, with release of the EDC mediator as a soluble isourea derivative. The reaction is quite efficient with no more than 2 hours required for it to go to completion and form a conjugated immunogen. 

Figure 22.16 SMPB-activated liposomes may be modified with peptide hapten molecules containing cysteine thiol groups. The resultant immunogen may be used for immunization purposes to generate an antibody...

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