“The concept is very simple , involving insertion of the gene encoding the antigen of choice into an bacterial plasmid ,and injection of the plasmid into the host ,where the antigen is expressed and induces humeral and cellular immunity .”

It was first discovered by Wolff who studies

on gene therapy by accident .

Control group

Surprise: naked DNA, expression of the antigenic gene , immune

response induced

“Cloning of SARS Sc gene and its effect on the immune response of mouse elicited by DNA vaccine pcDNA-Sc”

Objective:

To construct DNA vaccine against C region gene of SARS-CoV S protein, and observe the immune response indu

ced by DNA vaccine injection and mucosal immunization.

The specific antigen expressed in tissues

immuno-histochemical analysis.

The SARS-CoV antibodies in the sera

ELISA

Detect spleen and MLN lymphocyte proliferation and CTL response in vitro.

cytokine

cytokine

Y

Y

Y

Immune complex bound to Fc-receptor on APC

Somatic cell

“In animal model systems, DNA immunisation has been shown to induce protective immunity to influenza, herpes, rabies, hepatitis B and lymphocytic choriomeningitis viruses, and to malaria and mycobacteria.”

Enhance the immunogenicity of

DNA vaccine

“A very recent approach is the so-called “harmonization” of the DNA seque

nce coding for the antigen, enabling more efficient translation of non-mammalian DNA sequences by mammalian host cells. The basis for this approach is the preferential use of different codons for the same amino acid by bacteria, protozoan parasites, plants and mammalians.”

modulation of the gene of choice itself

harmonization

Vaccine vectors

Activation of an innate immune response

Antigen-specific adaptive immune response

prerequisite

Two major functions of adjuvants :

inflammatory response of the injection site

prevent rapid degradation and elimination of the antigen

Vaccine vectors

Adjuvants :

Danger ,death – innate immunity

Adaptive immunity

First report came as an surprise

Pro-inflammatory signal is also called “danger” signal

“naked DNA can launch an specific adaptive immune response without adjuvants to stimulate innate immune response”

PAMP + PRRs cocktail of secreted factors

Recruit of leukocytes

Milieu of an effective immune response

The discovery of PRRs explains everything

“Death - - apoptosis”

Molecule changes occurring on the surface of apoptotic cells

can be recognized by immune system.

phagocytized by APCs , processing , then cross-priming

Prerequisite :

1. Induce apoptosis

2. Antigen expression must precede cell death ,thereby allowing accumulation of antigen material.

Also unexpected advantages :

”triggering apoptosis in cells transfected with a plasmid eliminates a longering safety concern of many critics of DNA vaccine –the unlikely but theoretically possible Integration of the DNA into host’s genome which result in tumorgenesis. ”

Also can enhance DNA vaccine efficacy .

Very strange ,isn’t it ?

pro-apoptotic molecule act on transfected somatic cells

While anti-apoptotic molecules benefit transfected APCs

Discrepancy :

No universal strategy

“the usefulness must be explored for different antigens ,disease models , and vector backbone”

“The DNA immunization strategy has the potential to rapidly provide a new vaccine in the face of an emerging influenza pandemic.”

Emergency and cross-protection

Emergency : expression-library immunization (ELI)

Combined vaccine

Be achieved more easily than conventional vaccine

“The available information concerning safety is encouraging, with the risk of integration being considered to be orders of magnitude below the spontaneous mutation frequency in humans.”

The perceived risks include:

unlikely but

theoretically possible

integration of the plasmid into the host genome;

induction of anti-DNA antibodies

autoimmunity

“ DNA vaccines first advanced to the clinic five years ago, and the initial picture of their utility in humans is emerging. However, further analysis is required to determine their ultimate efficacy and safety in human beings.”

吴珍 张慧慧 吴瑕 徐安涛 徐慆 钊超

“the use of homologous genes from other species in an attempt to break tolerance to self-antigens.”

Establish an experimental animal model

for example: Establish an experimental autoimmune myasthenia gravis

Constructed by inserting the gene fragment of human acetylcholine receptor α- subunit N-terminal 211 residues (AChR_ α211 ) into shuttle plasmid pcDNA3.0.

GnRH

FS

Testosterone

immunoemasculation

in livestock agriculture

吴珍 张慧慧 吴瑕 徐安涛 徐慆 钊超