Vaccines

What is passive immunity?

Passive immunity is the protection against diseases supplied by an external source.

• Does not challenge the immune system

• Rapid, temporary protection

• Commonly passed from mother to child

Passive immunization has several benefits:

• Prevents disease after a known exposure

• Ease symptoms of an ongoing disease

• Protect immunodeficient individuals

• Blocks the action of bacterial toxins

What is active immunity?

Active immunity is the process by which protection against a disease that occurs after antibody production against a particular pathogen.

• Challenges the immune system

Active immunity can be naturally acquired following recovery from an infectious disease, or artificially acquired through vaccination.

What are the five (5) types of vaccines?

• Live vaccines

• Inactivated vaccines

• Subunit vaccines

• Recombinant factor vaccines

• DNA vaccines

What are live vaccines?

Live vaccines are avirulent, attenuated live organisms that are cultured in live mediums where they don’t naturally grow (e.g., embryonic egg or tissue culture).

These organisms are capable of reproduction; however, they’ve been weakened to such a degree that it can no longer cause disease. Growing under non-physiological conditions results in a virus that:

• Grows poorly at physiological temperatures

• Does not replicate well in a human host

• Poorly adapted to immune response evasion

• Cannot disseminate

This replication exposes the host to a mild concentrations of antigens to develop antibodies against over an extended period of time.

• Only requires one dose

• Results in long-term immunity

What are potential issues that are associated with live vaccines?

• These might not be effective for immunocompromised individuals.

• You run the rare risk of the attenuated bacteria reverting back to the virulent form.

• Has picky storage conditions

What are inactivated vaccines?

Inactivated vaccines are vaccines with pathogens or toxins that have been inactivated by heat or chemicals.

There are two (2) types of inactivated vaccines:

1. Inactivated whole cell vaccine = the complete, inactivated pathogen cell

2. Inactivated toxin = toxoid

Inactivated vaccines require multiple doses because they generally produce a weaker immune response.

Co-administered with adjuvants that enhance the overall immune response.

• Short-term immunity

What are subunit vaccines?

Subunit vaccines are vaccinations with only the antigenic component (polysaccharide/protein) of the pathogen.

• A type of inactive vaccine

• Polysaccharide subunit vaccines can include those directed against the capsule of the pathogen.

What is the problem with subunit vaccines?

Subunit vaccines are T-independent antigens. Therefore, antibody response is limited to IgM and is relatively poor.

• Polysaccharide subunits can be conjugated to give rise to a T-dependent immune response (conjugated subunit vaccine)

  • These result in more antibody production that standard polysaccharide vaccines

  • Induce class switching to IgG and memory B-cell differentiation

What are recombinant vector vaccines?

Recombinant vector vaccines are vaccines where gene-encoding antigens are inserted into a safe carrier organism—i.e., a bacteriophage or virus—that is nonpathogenic to humans.

• When the recipient is inoculated with this modified carrier organism, the bacteriophage replicates inside the host without directly harming it.

• As this carrier organisms undergoes a lysogenic cycle inside the host cell, it present antigen gene on the surface of the host cell, generating an immune response that activates both T-cell and antibody-related immunity.

• Again, these recombinant carrier organisms do not directly cause harm to the host because they lack the virulence factors to cause disease.

Immune response is like the live vaccine response. Perhaps because it is a type of live vaccine.

What is DNA vaccines?

DNA vaccines are largely still experimental and are not in widespread use.

The core principle of this technology is this idea that the antigen gene is directly inserted into the vaccinee’s cell via a plasmid vector.

This plasmid is then uptaken by the vaccinee’s cells, where the gene will be expressed and an antigen is produced.

DNA vaccines aim to produce botha cell-mediated (TH1) and antibody-mediated (TH2) immune response.

• Very stable vaccines because it’s DNA