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Protein-based subunit vaccines

More about Hepatitis B vaccines

The first available hepatitis B vaccines were plasma-derived, produced by harvesting hepatitis B surface antigen (HBsAg) from the plasma of persons with chronic HBV infection. The particles are highly purified, and any residual infectious particles are inactivated by various combinations of urea, pepsin, formaldehyde and heat. Although concerns about transmission of bloodborne pathogens, including HIV, from plasma-derived vaccines have proven to be unfounded., public concerns over the safety of the plasma-derived vaccine hampered its acceptance in many populations. Therefore increased research efforts were made to develop a recombinant vaccine.

In 1986, a hepatitis B vaccine produced by recombinant technology was licensed, and a second followed in 1989. The recombinant technology expressed HBsAg in other microorganisms and offered the potential to produce  unlimited supplies of vaccine.

Although both the plasma-derived and recombinant hepatitis B vaccines are safe and highly effective in protecting against acute hepatitis disease as well as chronic disease, including cirrhosis and liver cancer, competition among the various hepatitis B vaccine producers drove down the price. When the price of both the plasma-derived and recombinant hepatitis B vaccines was relatively similar, the recombinant gradually replaced the plasma-derived hepatitis B vaccine.

Protein-based subunit vaccines

More about Pertussis vaccine

Both acellular (aP) and whole-cell pertussis (wP) vaccines are safe and effective. In terms of rare, more severe adverse reactions, aP and wP vaccines appear to have the same high level of safety. However, mild-to moderate adverse reactions are more commonly associated with wP vaccines, and tend to increase with client age and the number of injections. This is why wP vaccines are not recommended for use in adolescents and adults where aP vaccines rather come to use.

Because the price of wP is considerably less than aP, where resources are limited and the vaccine is well accepted by the local population, wP vaccine remains the vaccine of choice. In countries where a higher rate of adverse reactions after immunizations with wP prevents  high vaccination coverage, aP is recommended instead, at least for booster injections.

Protein-based subunit vaccines

Adverse reactions associated with subunit protein-based vaccines

• Acellular pertusis (aP)

1. Same as tetanus and diptheria toxoid vaccines
2. Acellular pertusus-containing vaccines are less reactogenic in terms of mild-to-moderate reactions than wP-containing vaccines

• Hepatitis B (HepB)

1. Very rare
2. Reports of severe anaphylactic reactions are very rare

Protein-based subunit vaccines

Commonly used protein-based subunit vaccines are the following:

• Acellular pertusis (aP) vaccines contain inactivated pertussis toxin (protein) and may contain one or more other bacterial components. The pertusis toxin is detoxified either by treatment with a chemical or by using molecular genetic techniques
• Hepatitis B vaccines are composed of the hepatitis B virus virus surface antigen (HBsAg), a protein produced by hepatitis B virus. Earlier vaccine products were produced using purified plasma of infected individuals. This production method has been replaced by recombinant technology that can produce HBsAg without requiring human plasma increasing the safety of the vaccine by excluding the risk from potential contamination of human plasma.

Protein-based subunit vaccines

Protein based subunit vaccines present an antigen to the immune system without viral particles, using a specific, isolated protein of the pathogen. A weakness of this technique is that isolated proteins, if denatured, may bind to different antibodies than the protein of the pathogen.

Subunit vaccines

Subunit vaccines can be further categorized into:

• Protein -based subunit vaccines
• Polysaccharide vaccines
• Conjugate subunit vaccines

Subunit vaccines:

Safety and stability

Like inactivated vaccines, subunit vaccines do not contain live components and are considered as very safe.

Immune response:

• Must determine which combination of antigenic properties will produce an effective immune response with the correct pathway
• A response may be elicited, but with no guarantee that memory will form for future responses
• Less strong immune response compared to LAVs

Safety and stability:

• Have no live components, no risk of inducing the disease
• Safer and more stable than LAVs
• Excellent stability profile

Subunit vaccines

Immune response:

• Subunit vaccines, like inactivated whole-cell vaccines do not contain live components of the pathogen. They differ from inactivated whole-cell vaccines, by containing only the antigenic parts of the pathogen. These parts are necessary to elicit a protective immune response
• This precision comes at a cost, as antigenic properties of the various potential subunits of a pathogen must be examined in detail to determine which particular combinations will produce an effective immune response witthin the correct pathway
• Often a response can be elicited, but there is no guarantee that immunological memory will be formed in the correct manner

Inactivated whole-cell vaccines

Safety and stability:

• Inactivated whole-cell vaccine have no risk of inducing the disease they are given against as they do not contain live components
• They are considered more stable than LAV vaccines.

Inactivated whole-cell vaccinations

Immune response:

• Inactivated-whole cell vaccines may not always induce an immune response and the response may not be long lived
• Several doses of inactivated whole-cell vaccines may be required to evoke a sufficient immune response