Advances in basic and clinical research on immunotherapy of tuberculosis, especially the dual internal and external parasitism of Mycobacterium tuberculosis cells, the different expression, presentation and recognition pathways of endogenous and exogenous antigens in the organism, the distribution and characteristics of central and peripheral (circulating) memory T cell subsets, the effector cells, cytokines and final effector links in tuberculosis immunity, the timing and conditions of immunotherapy, and the complementarity of immunotherapy with antituberculosis chemotherapy should be taken into account by all researchers. The advances in understanding of the complementarity of immunotherapy and antituberculosis chemotherapy should be of interest to all researchers in immunotherapy of tuberculosis. The common resources of modern immunology research should be fully utilized to eliminate bias and promote further progress in TB immunotherapy research.
Regarding TB immunotherapy research, based on the different understanding of immunological mechanisms by different scholars, the main areas of focus are.
1. immunomodulatory factor replacement therapy that enhances the Th1-type immune response and suppresses the Th2-type immune response and suppresses the B-cell immune response.
2, vaccine therapy with Mycobacterium and its extracts.
3, treatment with genetic vaccines or genetically engineered vaccines.
4. treatment with immune preparations (non-mycobacterial vaccines, herbal medicines, chemical preparations) that enhance non-specific immunity.
5. based on the affirmative role of BCG in immunoprophylaxis of tuberculosis, which was originally thought not to be used in the treatment of tuberculosis, some scholars have again conducted research on immunotherapy with this vaccine from different aspects and levels, and have made affirmative progress in theory and clinical application
6. stem cell immune reconstitution; etc. To this day, it is necessary to make a short summary of the basic and clinical research on tuberculosis in order to take less detours and achieve more effective and economical results with half the effort.
I. The progress in the field of immunology of tuberculosis in recent years must be addressed
In the study of immunological mechanisms, most scholars have been enthusiastic about the CD4 cell Th1 pathway for decades, and the cell network doctrine of this pathway has become more complete and is indeed an important pathway for immune protection against tuberculosis, but there are indeed some misunderstandings in the understanding of this pathway, some of which overstate its significance, some of which overemphasize the role of the so-called Th1-type cytokines and their value in determining the immune status of the host. In recent years, the CD8 cytotoxic pathway, which has been lukewarm or misunderstood, has also received increasing attention, and there has been remarkable progress in the study of the role of the cytotoxic pathway in the clearance of target cells and their resident bacteria and the relevance of cytotoxic factors to anti-Mycobacterium tuberculosis; the NK cell pathway is also receiving increasing attention; and stem cell therapy for immune reconstitution is a completely new field. We should follow the pace of immunology as a whole to evaluate immunotherapy research in tuberculosis.
(i) The specificity of Mycobacterium tuberculosis infection
Mycobacterium tuberculosis infects the host and is not only phagocytosed, killed or inhibited by phagocytes, but also parasitized within immunophagocytes, and this specificity determines the special nature of antigen processing and antigen recognition in immunization against tuberculosis.
(ii) Antigen processing and antigen presenting cells against Mycobacterium tuberculosis
The first aspect of human immunity is achieved through the antigen presenting cell (APC) or target antigen presenting cell. Antigen-presenting cells in the immune system are those that can take up and process antigens and present them to immune cells such as T and B lymphocytes by presenting endogenous or exogenous antigenic peptides on the cell surface via MHC molecules. The specialized antigen-presenting cells include monocytes-phagocytes, dendritic cells, and B cells; the non-specialized antigen-presenting cells include endothelial cells, fibroblasts, various epithelial and mesothelial cells, etc. The target cells infected by intracellular parasitic pathogens are phagocytes transformed into target antigen-presenting cells (including virus-infected tumor cells). Eosinophils also have an antigen-presenting role.
1. There are two types of immune antigen-presenting cells in tuberculosis. ManLAM, a component of the cell wall of Mycobacterium tuberculosis, inhibits the maturation of DCs through the binding of its mannose cap residue to the dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintergrin (DC-SIGN), which affects the host’s antitubercular immune response. immune response. The other type of phagocytes infected by Mycobacterium tuberculosis is the phagocytes in which Mycobacterium tuberculosis forms an anti-lysosomal membrane to counteract the killing effect of phagocytes, inhibits the maturation of phagocytic lysosomes to reduce their bactericidal activity, and inhibits the apoptosis of infected phagocytes by producing transforming growth factor β (TGF-β) to evade host immune recognition. At this point, the infected phagocytes not only have no immune activity to kill the antigen, but also become target cells to shelter Mycobacterium tuberculosis and also become endogenous antigen presenting cells.
2. Antigen processing, presentation and recognition pathways
(1) Exogenous antigen processing, presentation and recognition pathway APC is phagocytosed, cytosolic, adsorbed or ingested into Mycobacterium tuberculosis by macrophage IgG Fc receptor (FcR) and complement receptor (CR)1 mediated conditioning to form phagosomes, which fuse with lysosomes to form phagolysosomes, where the antigen is degraded by protein hydrolases into small molecule peptides, including immunogenic antigenic peptides. peptides. The MHC-II molecules synthesized in the endoplasmic reticulum enter the Golgi apparatus and are carried by secretory vesicles, where they fuse with phagolysosomes to form an antigenic peptide-MHC II molecule complex antigen by binding the antigenic peptide to the MHC-II molecule in the vesicles. This complex antigen is expressed on the surface of APC and can be recognized and bound by the corresponding CD4+ T cells, which cannot be recognized by CD8+ T cells.
(2) Endogenous antigen processing, presentation and recognition pathway Target cell antigens, also known as endogenous antigens, are antigens synthesized by the cells themselves. The target cells infected by Mycobacterium tuberculosis interact with Mycobacterium tuberculosis and generate endogenous antigen in the target cells, which is degraded into small molecule polypeptides by small molecule polymeric polypeptidomes (LMP) present in the cytoplasm; after binding with certain proteins in the cytoplasm, the small molecule polypeptides are transported to the endoplasmic reticulum by the transporter of antigenic peptides (TAP) and become immunogenic antigenic peptides through processing and modification; the antigenic peptides bind to MHC class I molecules synthesized in the endoplasmic reticulum CD4+ T cells cannot recognize it.
(iii) Non-specific immune regulatory and effector cells
1. Macrophages are important immune cells in natural immunity against Mycobacterium tuberculosis infection. Their effect is shown in the phagocytosis of Mycobacterium tuberculosis, and their phagocytic lysosomes lyse, kill or inhibit Mycobacterium tuberculosis. Their regulatory role is manifested by their ability to attract and recruit other immune cells to the site of inflammation to play an immunoprotective role. Many substances can influence the response of macrophages to Mycobacterium tuberculosis. Adenosine ADO increases the number of mononuclear macrophages, their phagocytic activity and antibacterial effect. Glutathione affects the growth inhibition of intracellular Mycobacterium tuberculosis [28]. Intracellular neurosphingesine kinase (sphingesine kinase) in macrophages plays a similar role as a calcium signal driver during phagocytosis [29], and phosphatidylinositol triphosphate (PI3P) is a transport-regulated lipid on the cell membrane associated with lysosomal acquisition of phagocytic vesicles. Mycobacterium tuberculosis can inhibit the maturation of phagocytic lysosomes by inhibiting neurosphingosine kinase or hydrolyzing PI3P in macrophages. The biogenesis of phagocytosis and phagolysosomes represent fundamental biological processes that are important for the maintenance of homogeneity of their own tissue development, clearance of invading pathogenic microorganisms, and antigen presentation. Macrophages, stimulated by Mycobacterium tuberculosis and other cytokines, are able to produce many cytokines associated with antitubercular immune regulation and effects such as IFN-γ, TNF-α and IL-2, IL-23; they also produce inhibitory cytokines such as IL-6, IL-10. IL-6 stimulates early IFN-γ production and can also inhibit normal macrophage reactivity. The heterogeneity of macrophages may be one of the important factors in determining the immune response of the body and the regression of intracellular pathogenic infectious diseases.
2. natural killer cells (NK cells) are important members involved in immunity to intracellular pathogens. nK cells are activated in the early stages of TB and are important cells for the production of IFN-γ and perforin, with a function of lysing target cells. nK cells can also link natural and acquired immunity by activating CD8 cells to produce IFN-γ and lyse infected cells. However, some studies have shown that NK cells do not protect the body or even have harmful effects in the late stages of Mycobacterium tuberculosis infection.
3. Neutrophils After Mycobacterium tuberculosis infection, neutrophils become more chemotactic and accumulate in tuberculous nodules. Neutrophils are the first immune cells to reach the replication site of Mycobacterium tuberculosis and can kill Mycobacterium tuberculosis, but too many neutrophils can lead to increased pathological tissue damage.
(iv) Acquired immune memory, regulatory and effector cells
1. Immune memory T cells (CD45RO+ T cells): 2 subpopulations including central memory T cells (TCM) and peripheral memory T cells (TEM) [39-41].
(1) TCM express chemokine receptor 7 (CCR7) and homing receptor (CD62L); TCM exert reactive memory functions and homing to T cell areas in secondary lymphoid organs with little effector function, but can stably proliferate and differentiate into effector cells in response to antigen stimulation. Compared with natural T cells, TCM are highly sensitive to antigenic stimulation, less dependent on co-stimulatory signals, and upregulate the expression of plasma soluble leukocyte surface differentiation antigen 40 ligand (CD40L) with more effective stimulatory feedback to DCs and B cells. After T cell antigen receptor (TCR) signaling, TCM mainly produced IL-2, but after proliferation, they differentiated into effector cells and produced large amounts of IFN-γ or IL-4.
(2) TEM lost CCR7, mainly express chemokines that migrate to inflammatory sites, and the expression of CD62L is heterogeneous; TEM mediates protective memory, which migrates to peripheral inflammatory sites and exerts effector functions. Compared to TCM, TEM can perform effector functions rapidly, e.g. CD8+ TEM carries a large number of granzymes. Upon antigen stimulation, both CD4+ TEM and CD8+ TEM rapidly produce IFN-γ, IL-4 and IL-5. Some CD8+ TEMs expressing the lymphocyte common antigen (CD45) isoform CD45RA also carry large amounts of perforin.
In anti-TB immunity, acquired immune memory cells are mainly T cells, including CD4+ T cells, CD8+ T cells and CD4+CD8+ double positive T cells. The relative proportions of TCM and TEM in CD4 and CD8 in peripheral blood were variable, with TCM predominantly in the CD4 subpopulation and TEM predominantly in the CD8 subpopulation; however, in tissues TCM and TEM showed different distribution patterns, with TCM predominantly in the lymph nodes and tonsils and TEM predominantly in the lung, liver, and intestine. CD8T cells distributed in non-lymphoid tissues had direct killing activity, while those in the spleen had no direct killing activity.
Recent studies have reported that NK cells also have an immune memory function. The B-cell pathway is not considered to be correlated with protective immunity against tuberculosis, but some scholars believe that it is correlated with pathological damage of tuberculosis, but IL-12 produced by B cells is associated with T-cell immune regulation.
2. anti-TB immunomodulatory T cells Mainly acquired immune memory T cells, including TCM and TEM. natural regulatory (or suppressive) CD4+CD25+ T cells or CD4+CD25high T cells may also be involved in suppressive immunomodulation of TB. However, the causal relationship between the extent of lesions and changes in the number of CD4+CD25high T cells in TB patients is unclear.
3. Anti-tuberculosis immune effector cells are mainly monocytes-phagocytes, CD4+ CD25- T cells, CD8+ T cells, CD4+CD8+ double-positive T cells and NK cells.
(V) Cytokines involved in immune regulation
Cytokines are usually divided into five major categories.
(1) Natural immune-related effectors such as INF-α/β, TNF, IL-1, IL-6, etc.
(2) Lymphocyte activation, growth and differentiation-related regulatory factors such as IL-2, IL-4, TGF-β, IL-9, IL-10, IL-12, etc.
(3) Inflammatory response activators such as IFN-γ, lymphotoxin (LT), macrophage movement inhibitory factor (MIF), etc.
(4) Immature immune cell growth and differentiation-related stimulating factors such as IL-3, GM-CSF, IL-7, etc.
(5) Cytotoxic cytokines such as perforin, granzyme, granulysin, etc. The above cytokines, except granulysin, do not have the effect of directly killing Mycobacterium tuberculosis.
IFN-γ is only an activator of the inflammatory response, and the stronger the inflammatory response, the stronger the immune protection. It is inappropriate to overemphasize the role of IFN-γ in the anti-tuberculosis protective response, and it is also questionable to regard IFN-γ as the signature molecule of the Th1-type cellular immune response.
(vi) Effector molecules involved in anti-Mycobacterium tuberculosis immunity mainly include natural immunity-related effectors such as INF-α/β, TNF, IL-1, IL-6, etc., and cytokines related to cytotoxic effects such as perforin, granzyme, granulysin, etc. Among them, only granulysin can directly kill Mycobacterium tuberculosis.
(vii) The end effect point of immune response is simple and clear. The cytotoxic pathway achieves the immune effect through the clearance of target cells and the killing of Mycobacterium tuberculosis by granulocytes; and both of these objectives should be achieved while minimizing the possible side effects of accompanying histopathological damage.
II. Current immunotherapy approaches and methods
(i) Factor replacement therapy
1. Immune factor replacement therapy is considered by many scholars to be an anti-tuberculosis-specific approach. It includes.
(1) cytokine replacement therapy to enhance Th1-type immune response. IL-2 promotes the proliferation and activation of tuberculosis antigen-specific T cell clones, prompting T cells to secrete IFN-g, activating NK cells and macrophages, and enhancing the ability of macrophages to kill Mycobacterium tuberculosis. The combination of IL-2 or IFN-g with anti-tuberculosis drugs for refractory tuberculosis or multidrug-resistant tuberculosis can lead to improvement of symptoms, negative sputum and lesion resorption. The toxic side effects of IL-12 in the treatment of tuberculosis are large. If anti-TNF-α therapy is administered to patients with rheumatoid disease, it is prone to TB relapse [53]. Cytokines have the disadvantages of short half-life and high cost, and IFN-g may also produce fever, chills, fatigue, headache and other side effects, so its “double-edged sword” effect should not be ignored and should not be concealed.
(2) Cytokine replacement therapy to suppress Th2 immune response, such as IL-7, which activates macrophages to play a bactericidal role, induces Th1 immune response, promotes the secretion of IFN-g, and suppresses Th2 immune response.
(3) Cytotoxic cytomolecules [46,48,49,55]. The role of perforin, granzyme, and granulysin in TB immunity has been demonstrated by a number of authors, and cytotoxic molecules are involved in at least three cytotoxic immune pathways.
(i) The perforin-granzyme pathway that promotes apoptosis of target cells.
(ii) Independent perforin pathway, independent granulysin pathway that promotes target cell lysis.
(iii) The perforin-granulysin pathway, which directly kills Mycobacterium tuberculosis in target cells. Granulysin is guided by perforin into target cells to kill intracellular Mycobacterium tuberculosis, potentially restoring phagocytic activity and reducing tissue damage. , the direct cytolytic pathway may cause tissue damage, the pro-target cell apoptosis pathway may cause less tissue damage, and the perforin-granulysin pathway may avoid tissue damage. There is still a vast space waiting for us to study how to achieve the best cytotoxic pathway.
(4) Small molecule cytokine replacement therapy. It has been reported that transfer factors can improve T lymphocyte activity, enhance cellular immune function, and synergize with chemotherapeutic drugs to clear and kill TB bacilli, thus significantly improving the cure rate and reducing the relapse rate. Thymidine or thymic factor D can induce and promote the differentiation, proliferation and maturation of T lymphocytes, enhance the phagocytosis of macrophages, improve the viability of NK cells, increase the expression level of IL- 2 and its receptor, enhance the production of IFN-g in peripheral blood monocytes, enhance the activity of superoxide dismutase in serum, and have the effect of regulating and enhancing cellular and humoral immune functions. Thymidine combined with anti-tuberculosis drugs for the treatment of tuberculosis can improve symptoms, promote negative sputum and lesion absorption, without obvious toxic side effects. Polyerga (PLG; a low molecular active peptide extracted from animal spleen) can activate the immune system, promote the release of IL-2 and IFN-g, increase T cell activation and stimulate the increase of cytokinesis inhibitor, and improve the immunity of the body. Pulmonary activator (PS) is a pulmonary cell-activating factor that promotes phagocytosis of pulmonary macrophages, promotes IL-2 and IL-1 production, improves cellular immune function, and promotes the healing and improvement of tuberculosis. Granulocyte-macrophage colony-stimulating factor (GM-CSF) promotes the differentiation of hematopoietic cells into granulocytes and macrophages, and can be used as an adjuvant therapy in leukopenic TB patients. Two contrasting results have been reported regarding the use of high doses of immunoglobulins as immunotherapy for TB. One report suggests that it favors sputum negativity and improves clinical outcome, while the other report suggests that it is detrimental to sputum negativity and exacerbates pathological damage.
(ii) Non-specific immunotherapy
1.Non-mycobacterium vaccine treatment Glucomycin, short small rod-shaped bacillus vaccine, etc., mainly non-specific enhancement of phagocytic activity.
2, herbal immunotherapy mainly non-specific adjustment of human immune function, Astragalus polysaccharide, Fructus Lycii polysaccharide, Acanthopanax polysaccharide, etc. can promote the secretion of IL-2, IL-3, IFN-γ and other cytokines, and significantly improve the cellular and humoral immune function of the body. The immunotherapy of herbal medicine also includes the regulation of human nervous system, humoral system and metabolic status. Some of these herbal medicines have certain antibacterial effect on Mycobacterium tuberculosis.
3, the application of chemical drug immune adjuvant Immune adjuvant in the treatment of humoral immunity-based disease has achieved positive results. There are also a few reports that immune adjuvants can enhance the therapeutic effect of tuberculosis. In fact, the immune enhancing effect of immune adjuvants in cellular immune-based diseases is not as effective as their enhancing effect on inflammatory response.
(iii) Mycobacterium bifidum, its metabolites and gene vaccine therapy
1, BCG vaccine immunotherapy Attention should be paid to the selection of the timing of immunotherapy, which may aggravate pathological damage when used alone or prematurely, but it is safe to use it together with chemotherapeutic drugs after 1 month of effective chemotherapy. It has enhanced effect on both Th1 immune pathway and cytotoxic immune pathway, especially on cytotoxic immune pathway. It can improve the clinical treatment effect and bacteriological cure rate of tuberculosis, reduce the 5-year long-term relapse rate, and reduce the incidence of multidrug-resistant tuberculosis.
2.Other mycobacterial immunotherapy including Mycobacterium pubescens vaccine, Mycobacterium graminearum preparation (trade name Utilin’s), etc., all have good effects on enhancing Th1 type immunity and improving the clinical effect of tuberculosis.
3, inactivated vaccine or mycobacterium extract vaccine treatment including Mycobacterium bovis vaccine (microcarcinogenic vaccine), BCG polysaccharide nucleic acid injection (trade name Stryker), etc. Promote the proliferation of monocyte-macrophage system, enhance the phagocytosis and digestion ability of macrophages, improve the ability of macrophages to produce NO and H2O2, significantly enhance the function of T lymphocytes and natural killer cells in the body, activate T cells to release various lymphokines, increase the expression of IL-2 and IL-2 receptors and the level of IFN-g induction, and in combination with chemotherapy can make TB patients gain weight, accelerate the speed of sputum negative, lesion absorption and cavity reduction and closure, shorten the short course of chemotherapy, and improve the efficacy of combined chemotherapy.
4.Gene vaccine therapy DNA vaccine expresses endogenous antigen intracellularly, which can induce not only humoral immunity and Th1-type cellular immune response, but also specific cytotoxic lymphocyte response, which is more meaningful for Mycobacterium avium disease parasitized in macrophages. Since 1994, Lowrie et al. have reported the results of several studies on DNA vaccines for the treatment of tuberculosis in mice, and several Mycobacterium tuberculosis DNA vaccines have been found to have good adjuvant therapeutic effects, such as hsp65, hsp70, Ag85A, Ag85B, and MPT64 DNA vaccines, all of which induce high levels of IFN-g and low levels of IL-4. In After conventional chemotherapy kills most of the Mycobacterium tuberculosis, DNA vaccines can induce a significant reduction in the number of residual bacteria in the body. In addition, Ag85A DNA vaccine increased the IFN-γ response to Ag85A protein in mice, effectively preventing reactivation of M. tuberculosis. The combination of Mycobacterium tuberculosis DNA vaccine and conventional chemotherapy can not only improve the immunity of the body, but also effectively inhibit the reactivation of Mycobacterium tuberculosis, improve the effect of chemotherapy and shorten the course of treatment, thus opening up a new way for the treatment of tuberculosis, especially drug-resistant tuberculosis. This is due to the limited efficiency of vaccine DNA conversion and the inability of DNA vaccines to self-replicate in the host like live vaccines. Gene therapy with isocitrate cloning enzyme knockout [74-76] and ATP synthase as target [77] has good results, but is not part of immunotherapy.
(iv) Immune reconstitution: it is an immunotherapy method that replenishes immune cells and restores or enhances the cellular immune function of patients by importing plastic immune primitive cells into the body through stem cell transplantation technique. The hematopoietic stem cells used for transplantation are mainly derived from bone marrow and embryonic liver cells. On one hand, hematopoietic stem cell transplantation is equivalent to transplantation of immune organs; on the other hand, bone marrow mesenchymal stem cells can differentiate into respiratory epithelial cells and restore damaged lung tissue. Therefore, hematopoietic stem cell transplantation can reconstruct the hematopoietic, tissue repair and immune functions of the recipient. It has been shown that the combined application of stem cell therapy in the chemotherapy of refractory and drug-resistant tuberculosis can improve clinical symptoms, lead to negative sputum bacteria, lesion absorption and cavity closure, and may be an effective new approach to the treatment of tuberculosis.
There are some other immunotherapy methods.
Third, the actual effects of clinical studies on different immunotherapy pathways and methods need further objective evaluation
There are more reported studies on immunotherapy of tuberculosis and more types of immune agents reported, and all of these studies have reported enhanced protective immunity against tuberculosis and improved clinical outcomes of tuberculosis treatment. However, it is the misguided nature of some of the immunological research literature published in this country that has resulted in the misuse of immune agents, which have contributed to the development of disease in TB-infected patients and contributed to the exacerbation of disease in TB patients.
The rationality of the design of these studies reported in China varies widely, and the significance of the assessment indicators used varies widely, especially the use of certain cytokines such as IFN-γ as assessment indicators. Although there are many studies on various types of immunotherapy for tuberculosis, these studies lack analysis and targeting of the immune status of the patients themselves, and not many pay attention to the timing of immunotherapy selection, and most of them are limited to short-term efficacy assessment, with very few reports of efficacy assessment over 2 years and even fewer reports of efficacy assessment over 5 years; there are few multicenter studies, and the efficacy assessment of multicenter studies is only short-term efficacy assessment The efficacy assessment of multicenter studies is only short-term. Therefore, most of the above studies cannot show the definite effect on the eradication of tuberculosis and the prevention of long-term relapse of tuberculosis. Multi-center, long-term follow-up studies are needed to further elucidate the exact effects of the above studies.
IV. Outlook and recommendations
Conducting research on immunotherapy of tuberculosis is both a need of the times and a need of social development. In summary, future research efforts should pay attention to the following aspects.
(i) The need to seek immunotherapeutic agents that enhance both Th1-type immunity and cytotoxic pathway immunity. There are two types of T-cell antigen presenting cells in TB cellular immunology, two antigen processing, presentation and recognition pathways, and they are not interchangeable; two types of immune memory cells and they are not interchangeable. The Th1 immune pathway and the cytotoxic immune pathway complement and influence each other, but are not interchangeable; the endpoint of the Th1 immune pathway is the enhancement of phagocytosis and killing of Mycobacterium tuberculosis, which is an important aspect of immunity against tuberculosis, but does not have the ability to clear target cells and hold the bacilli. The endpoint link of cytotoxic immune pathway is to promote apoptosis and necrosis of target cells or kill Mycobacterium tuberculosis inside and outside the target cells through the perforin-granulolysin pathway, which has the ability to clear target cells and hold on to mycobacteria, but it also cannot replace the function of phagocytes to phagocytose and kill Mycobacterium tuberculosis. Therefore, we need to seek immunotherapeutic agents that meet both requirements.
(b) Further selection of cytokines suitable for the assessment of immunotherapeutic effects is needed. There are numerous cytokines, but as far as their immunomodulatory effects are concerned, most of them enhance both the immune protective response and also the inflammatory response or pathological damage, or inhibit both the inflammatory response or pathological damage and also the immune protective response. Indeed, no regulatory cytokine has been found that enhances only the specific antituberculosis protective immune response but not the nonspecific inflammatory response. Although the immunomodulatory role of Th1-type cytokines has been well described in many studies, the “double-edged sword” effect of these cytokines cannot be ignored when used in the immunotherapy of tuberculosis. Only granulysin has been found to directly kill Mycobacterium tuberculosis; only the perforin-granulysin pathway has been found to directly kill Mycobacterium tuberculosis in target cells, potentially reducing target cell necrosis and reducing histopathological damage. In view of the participation of perforin in all three cytotoxic pathways, the possibility of using perforin as an assessment parameter for immunotherapy effect should be considered.
(iii) BCG vaccine should still be fully used at present Mycobacterium tuberculosis pathogens and immunogens are complex, involving not one but many or even many genetic determinants, and the knowledge in this area is still very poor. Research on genetic vaccines that enhance both protective immunity against tuberculosis without enhancing the non-characteristic inflammatory response or pathological damage still has a long way to go. The effectiveness of vaccine DNA is still weaker than that of live vaccines because of its limited efficiency of transformation and its inability to self-replicate in the host. Immune factor therapy is even more problematic with limited stimulatory effect, short duration, and high price. Among the anti-tuberculosis vaccines that have been introduced, none of them has achieved the same effect as BCG, let alone surpassed it. Research to enhance the immunogenicity of BCG is also underway, and until a better vaccine than BCG is available, it is important not to forget to fully apply BCG while conducting research on new vaccines.
(iv) Proper understanding of the side effects of immunotherapy. Live vaccine, inactivated vaccine, bacterial metabolites or extracts, and all kinds of cytokines are allogeneic proteins for patients receiving immunotherapy, and theoretically, any use of allogeneic proteins has the possibility of metabolic reactions, and the greater the molecular weight, the greater the possibility of metabolic reactions, and the greater the difference in species, the greater the possibility of metabolic reactions. It is almost impossible to find an anti-tuberculosis vaccine without side effects, and it is our endeavor to find a vaccine with few side effects. Regarding the evaluation of immunization effect and side effects of BCG vaccine, the reports of different scholars at home and abroad vary greatly, and there is a lack of exact data obtained from a large sample survey in China, so it is not scientific to treat foreign data as a domestic phenomenon, to treat the result of place A as a result of place B, or to treat a few individual cases as a general phenomenon. It is necessary to investigate the immunization effect and side effects of BCG vaccine in China, and the correct evaluation of BCG vaccine is also necessary to find a new vaccine. There are few reports of studies on immune reconstitution methods for the treatment of tuberculosis, and the exact effects need to be explored.
(v) Attention should be paid to the timing of immunotherapy Domestic studies on immunotherapy of tuberculosis with BCG vaccine have raised the importance of timing of immunotherapy. The same vaccine used at different times may produce completely opposite results, one inducing protective immunity against tuberculosis, while the other may aggravate pathological damage. This “double-tough sword” problem can exist with any existing antituberculosis vaccine. The timing of immunotherapy is to avoid the peak of disease metamorphosis and to select the induction period that may enhance protective immunity in order to achieve the effect of minimizing the inflammatory damage response while enhancing the protective immune response as much as possible, which is very important and must attract the attention of academics and clinicians.
(vi) The necessity of combining immunotherapy and chemotherapy The chemotherapeutic drugs for tuberculosis have powerful bactericidal or antibacterial effects on Mycobacterium tuberculosis in tissues and cells, however, despite adequate standardized chemotherapy, some patients still fail treatment or relapse after cure. ). Immunotherapy alone given to TB patients or those with known TB infection may result in worsening of the disease or onset of disease in those who do not have the disease, and immunotherapy alone is not advisable. In fact, after effective chemotherapy kills a large number of Mycobacterium tuberculosis, the metabolic state that causes immune damage in the body is significantly weakened, and immunotherapy given at this time is not likely to aggravate immune damage due to generalized reactions, but mainly induces protective immune responses; effective immunotherapy does enhance the effect of chemotherapy for tuberculosis. Tuberculosis chemotherapy and immunotherapy can complement each other, but they cannot replace each other, at least not yet.
In conclusion, by making full use of the common resources of modern immunological research, eliminating bias, and seeking realistic analysis, research on immunotherapy for tuberculosis is bound to make further progress.