Traditional Vaccine Approaches

In addition to the quality, specificity, and magnitude of the immunologic responses 

Live attenuated vaccines retain their ability to infect and replicate in the vaccinated host. However, infection is usually self-limiting, resulting in an absence or a milder form of the disease normally caused by the pathogen. These vaccines are usually made by repeated passage ( adapting ) of the pathogen in nonnatural hosts, or in tissue cultures, and selection for variants that show reduced pathogenicity (attenuation). 

The most notable example of live attenuated vaccines is the smallpox vaccine, first developed by Edward Jenner, although the origin of the vaccine (vaccinia virus) remains obscure. More recent examples of live attenuated vaccines include most of the viral vaccines currently in use, such as measles/mumps/rubella (MMR) and varicella zoster (VZV) vaccines, and some 

Lyses virus-infected cell Secretes TNFp, IFNy, IL-2 

antigen-presenting cell and, class I and II major histocompatibility complex (MHC) antigens o and , peptides from degraded antigen bound to MFIC molecules  

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Vaccination to induce an adaptive immune response is expected for a broad range of infectious diseases and cancers. Traditional vaccines are mainly composed of live attenuated viruses, whole inactivated pathogens, or inactivated bacterial toxins. In general, these approaches have been successful for developing vaccines that can induce an immune response based on antigen-specific antibody and cytotoxic T lymphocyte (CTL) responses, which kill host cells infected with intracellular organisms (Fig. 1) [1,2], One of the most important current issues in vaccinology is the need for new adjuvants (immunostimulants) and delivery systems. Many of the vaccines currently in development are based on purified subunits, recombinant... 

The induction of an immune response by various mucosal routes is an important approach for the control of mucosally acquired infections. The apparent linked nature of the mucosal immune system enables the delivery of an antigen to any mucosal surface to have the secondary effect of potentially inducing immunity at others. Induction of a combination of systemic and secretory immune responses can be determined by the nature of the antigen, the route of administration, and the delivery system utilized. For example, traditional parenteral vaccines primarily induce IgM and IgG responses, whereas mucosal vaccination can elicit both IgG and secretory IgA responses (Corthesy, 2007). 

Although the term is somewhat uncommon for vaccines, traditional investigations about their mode of action by assessing the type and duration of protective immune mechanisms under various conditions are based on a very similar approach. 

Detoxification. The process by which bacterial toxins are converted to harmless toxoids. Formaldehyde is used to detoxify the toxins of Corynebacterium diphtheriae, Clostridium botu-linum and Cl. tetani. The detoxification may be performed either on the whole culture in the fermenter or on the purified toxin after fractionation. Traditionally the former approach has been adopted, as it is much safer for the operator. However, the latter gives a purer product. The pertussis toxin used in acellular vaccines may be detoxified with formaldehyde, glutaraldehyde, or both, hydrogen peroxide or tetranitromethane. In the case of genetically detoxified pertussis toxin, a treatment with a low concentration of formaldehyde is still performed to stabilize the protein. 

Liposomes as a dosage form allow for a broad variety of administration routes. In addition to the most traditional and frequent parenteral (intravenous) way of administration, some alternative approaches are also developed or under development, although each of these approaches has its own problems and limitations. Thus, oral administration requires high liposome stability and drug delivery from the gut to the blood with subsequent drug release. Early attempts with polymerized liposomes as potential oral vaccine carriers were only partially successful. Currently, many alternative schemes are under development. 

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