Peptides, as immunogens that induce immune response from effector cells in vivo, have become a new type of vaccine. peptide vaccine has the function of anti-virus, anti-tumor, anti-bacteria, anti-parasitic infection and so on.

Advantages and disadvantages of peptide vaccines

At present, one of the important directions of vaccine research is peptide vaccine, and many peptide vaccines have been developed for some infectious diseases (AIDS, hepatitis C) and tumors. The so-called peptide vaccine is a vaccine prepared by chemical peptide synthesis technology according to the amino acid sequence of a certain epitope known or predicted in the antigen gene of the pathogen.

Peptides, as immunogens that induce immune response from effector cells in vivo, have become a new type of vaccine. peptide vaccine has the function of anti-virus, anti-tumor, anti-bacteria, anti-parasitic infection and so on. Because peptide vaccine is completely synthetic, there is no virulence recovery or inactivation of incomplete problems, with low cost, safety, strong specificity, easy to save and application of the advantages, more and more attention to the industry. But also because of its poor immunogenicity, low efficacy and short half-life and other deficiencies affect the immune effect.

Classification of peptide vaccines

Peptide vaccines can be divided into two categories: genetic engineering peptide vaccines and synthetic peptide vaccines: the former is also known as genetic engineering subunit vaccines, mainly using genetic engineering technology, the isolated antigen protein genes with strong immunogenicity are loaded into the expression vector through the host cell to express recombinant antigen proteins, so as to isolate and purify recombinant proteins as vaccines. There are two kinds of synthetic peptide vaccines, which are those with continuous epitopes and those with discontinuous epitopes. The continuous immunogenic epitopes are determined by protein antigen DNA cloning and nucleic acid sequence as well as serological studies. Discontinuous epitopes, thousands of peptides are synthesized randomly and rapidly, mainly through prior art, and then the sequences that can best bind to protective antibodies are screened.

In addition, a number of different bioinformatics tools have been developed in recent years to improve candidate selection and identification for novel epitopes for vaccine design. Including whole-exome sequencing data algorithms such as NeoPredPipe, MuPeXI, pVAC-Seq, and CloudNeo to identify individual patient mutations, predict the HLA allotype of individual patients with neoantigen-derived peptides, and integrate tumor mutation and expression data to predict the immunogenicity of these peptides. And evaluate their potential as T cell epitopes.

Tumor peptide vaccine

Tumor peptide vaccine refers to antigen peptides eluted from the surface of tumor cells or obtained from tumor cells, which can improve the humoral and cellular immunity of the body after immunization. Tumor peptide vaccine has the advantages of strong specificity and high safety, and has broad market prospects. Common forms of peptide vaccines include: directly extracted peptide vaccines, amino acid residues or sequence modified peptide vaccines, heat shock protein peptide complex vaccines, polyvalent peptide vaccines.

From the analysis of the mechanism of action of tumor peptide vaccine, immature DC (dendritic cells) secrete the inhibitory factor indoleamine 2,3 dioxygenase (IDO) to inhibit tumor immunity in immunosuppressive state. Therapeutic DC or peptide vaccines enhance anti-tumor immune response by promoting DC maturation, B-cell antibody secretion, cytotoxic T cell proliferation and killing. Globally studied tumor peptide vaccines include those that target folate receptors (FR) or those developed against HER2 targets. As of April 25, 2022, a total of 58 peptide vaccines have been marketed worldwide.

Research progress of global peptide vaccines

From the perspective of global research and development of peptide vaccines, the research on the design of peptide vaccines targeting T and B cell epitopes has achieved good results, but there are still many problems to be further solved, including the optimal selection of epitopes, the optimal connection of epitopes, the development of suitable adjuvants and the application of vectors. It is believed that with the progress of science and technology, the research of peptide vaccines will continue to deepen in the future, in order to continuously improve the research and development efficiency of peptide vaccines, reduce research and development costs, and bring new hope to patients with global diseases.