Seek a paper on immunization

Since 1796, when the British doctor Jener first used cowpox vaccine, vaccines have been widely used in the world, and over the past 200 years, various kinds of vaccines have helped human beings to overcome many kinds of infectious diseases, including smallpox. However, there are two kinds of vaccines: the first one is the traditional vaccine, i.e., live and inactivated vaccine, such as chicken Newcastle disease vaccine and swine fever inactivated vaccine, which is to inoculate non-toxic or attenuated pathogens directly into the human or animal body as a vaccine to stimulate the immune system to produce specific immune response, so as to prevent the disease from occurring; the second vaccine is the genetically engineered vaccine, which is to isolate and isolate the pathogens with strong immunogenicity but without immunogenicity by means of genetic engineering; the second vaccine is the genetically engineered vaccine. The second type of vaccine is genetic engineering vaccine, it is through genetic engineering, first isolate the coding gene of antigenic protein with strong immunogenicity but no toxicity, then introduce it into the expression vector, then express the recombinant antigenic protein in the host cell, and then the recombinant antigenic protein is used as a vaccine such as recombinant Hepatitis B vaccine after isolation and purification. However, it has some defects that cannot be ignored, such as: inactivated vaccine is difficult to induce cellular immunity, requiring multiple immunizations; subunit vaccine immunogenicity is poor; live attenuated vaccine has the danger of toxicity rebound, etc. Therefore, nowadays, some infectious diseases can be treated with inactivated vaccine. Therefore, there is still a lack of safe and effective vaccines for some infectious diseases. The introduction of the third-generation vaccine, the gene vaccine, has brought hope for the solution of these problems.

Genetic vaccine (genetic vaccine), also known as nucleic acid vaccine (nucleic acid vaccine) or DNA vaccine, is developed on the basis of gene therapy (genetic therapy) technology. Gene therapy is the most revolutionary biomedical medical technology developed in the 1980s for the prevention and treatment of diseases, the principle of which is to introduce normal genes or therapeutic genes of human or animals into target cells of human body in a certain way in order to correct the defects of the genes or to play a therapeutic role, so as to achieve the purpose of treating diseases. 1990, Wolff JA, etc., in the gene therapy test. In 1990, Wolff JA and others, when conducting gene therapy test, used naked DNA injection as a control, and accidentally found that naked DNA could be absorbed by skeletal muscle cells and expressed exogenous proteins. 1992 Tang, DC and others proved for the first time that exogenous proteins generated by gene immunization, human growth hormone, could stimulate the immune system of mice to produce specific antibodies, and the potency of antibodies increased after strengthened immunization, thus announcing the birth of gene vaccine. The antibody potency increased after strengthening immunization, thus announcing the birth of gene vaccine. (Note: 1)

In summary, a gene vaccine is a gene encoding an exogenous antigen that is inserted into a vector containing a eukaryotic expression system, and then directly introduced into a human or animal to express an antigenic protein in a host cell, which directly induces an immune response in the body. The continuous expression of the antigenic gene within a certain time limit constantly stimulates the body's immune system to produce a response, thus achieving the purpose of disease prevention.

The mechanism of nucleic acid immunization

Currently, the understanding of the mechanism of nucleic acid immunization is mainly limited to theoretical speculation, and most of the information comes from the gene therapy test, the two are very similar in the mechanism of action. In gene immunization, a nucleic acid vaccine containing the antigenic gene of the pathogen is introduced into the host cell, is taken up by surrounding tissue cells, APC cells, or other inflammatory cells, and is expressed intracellularly. The possible routes of presentation of the expression products as antigens are: direct uptake by myocytes or uptake into the T-tubules and cell-like invaginations, expression of the exogenous gene under the action of the exogenous gene promoter, so that the products are broken down by intracellular hydrolytic enzymes into polypeptides of varying lengths, a part of which is transported to the endoplasmic reticulum by hsp70, and is transferred to the membrane via TAP molecules on the reticulum to be bound to the major histocompatibility complex (MHC ) class I, which is eventually recognized by CDS ten cells at the cell membrane surface; another part of the short peptide enters the lysosome, binds to (MHC) II molecules, and is transported to the cell surface to be recognized by CD4+ cells. These peptides contain different antigenic epitopes, and they will induce cytotoxic T-lymphoid precursors, B-cells, and specific helper T-cells to generate cellular and humoral immunity. At the same time, gene expression can enter the tissue interstitial space by means of cell secretion and division and be recognized by B lymphocytes in a naturally folded manner. Following nucleic acid immunization, myocytes and antigen-presenting cells can also be infected, resulting in the activation of CD4+ and CD8+ cell subsets to generate specific immune responses. CorrM et al. (1996) showed that antigens released from DNA-transfected muscle tissue are taken up by APCs, transported to tubular lymph nodes, and expressed in B and T lymphocytes, and that the class I MHC-restricted CTL response may be generated primarily in this manner. It was previously thought that this process required the expression of endogenous antigens, but studies now suggest that the presence of exogenous antigens can also be effective in eliciting class I MHC-restricted CTL responses.

III. Construction of plasmid vectors for gene vaccines

Obtaining the exact antigen-encoding gene and inserting it into the appropriate vector DNA is the main task in the development of gene vaccines.

1, the isolation of genes encoding antigenic proteins

Preparation of DNA vaccines should first obtain the genes encoding antigens, and generally choose the genes encoding the surface glycoproteins of pathogens. Antigenic proteins can be correctly glycosylated in the host body, thus inducing an immune response to the pathogen; for easily mutated pathogens, it is best to choose a variety of variants of the core protein conserved DNA sequences, so that a variety of variants of the pathogen can produce an immune response, avoiding immune evasion due to the variability of the pathogen.

2 Vector construction of target gene plasmids

Gene vaccines mostly use plasmids as vectors. Generally speaking, gene vaccine plasmid vectors include at least five major components: (1) bacterial replicon, so that the plasmid DNA in the bacterial body replication and amplification, to get a large number of copies, but can not be replicated in the host cell (eukaryotic cells); (2) prokaryotic selective marker genes, such as antibiotic resistance genes, in order to screen for positive bacterial clones (strains) containing plasmid DNA; (3) eukaryotic promoters, enhancers, terminators, introns and other transcriptional regulatory elements; (4) sequences of target genes encoding antigenic proteins; and (5) polyribonucleotide signaling sequences to ensure timely termination of mRNA translation. In addition, gene vaccine plasmid vectors usually contain a segment of unmethylated CpG sequence, which has immune activity to stimulate Th1 cells.

IV. Systemic inflammatory response syndrome and immunomodulatory therapy after severe trauma

The immune function of the body after severe trauma shows bidirectional changes. On the one hand, the immune suppression is represented by the decrease of phagocytosis and interleukin-2 (IL-2) production; on the other hand, the excessive inflammatory response is characterized by the systemic inflammatory response syndrome. It is the combination of these two aspects that constitutes the post-traumatic immune dysfunction and induces Multiple Organ Dysfunction Syndrome (MODS). The following is a review of systemic inflammatory response syndrome and immunomodulatory therapy.