Bacterial lysate add-on therapy in adult and childhood asthma: a systematic review and meta-analysis

Introduction

The hygiene hypothesis suggests that reduced exposure to microorganisms in early life leads to an increased incidence of allergic diseases. The early life period is crucial to the establishment of immune tolerance, which is important for the maintenance of stable and normal physiologic functioning of the innate and adaptive immune responses (1). A balanced and stable immune function of the airway relies on appropriate interactions between the microbiota colonizing the mucosa, host immune responses, and environmental microorganisms (2).

Increased urbanization has considerably improved hygiene status and altered daily life patterns. Increased rates of caesarean section, reduced rates of breastfeeding, and overuse of antibiotics may considerably decrease microorganism diversity, which contributes to dysfunctional immune tolerance and promotes the occurrence of allergic diseases such as asthma. Based on these theoretical backgrounds, the influence of environmental microbial components on functions of the immune system has been garnering increasing attention. Subsequently, numerous animal and clinical trials have been used to examine microorganisms and their lysates or metabolites.

OM-85 (Broncho-Vaxom) has been widely used as an immunomodulator since the 1950s. OM-85 is a low endotoxin alkaline lysate, prepared using a standardized process from 21 strains of five bacterial genera (including Moraxella, Hemophilus, Klebsiella, Staphylococcus, and Streptococcus) that colonize the human respiratory tract (3). Currently, OM-85 is normally used in clinical treatment to prevent recurrent respiratory tract infections. Because atopic individuals tend to develop respiratory infections due to unbalanced T helper-1 (Th1) and T helper-1 (Th2) immune responses (4), strengthening the airway anti-pathogenic function is considered an important strategy in the treatment of patients with allergic diseases.

Orally administered OM-85 has been shown to decrease alveolar inflammatory cell infiltration in various murine models of allergic airway inflammation by reducing the levels of Th2 cytokines and promoting the proliferation of regulatory T cells (5-8). OM-85 has also been empirically used by numerous pediatricians to control or relieve wheezing symptoms in pediatric patients. However, whether OM-85 actually shows clinical benefits in alleviating asthma symptoms in patients remains controversial. In this study, we used a meta-analysis to determine whether OM-85 is beneficial in alleviating the clinical symptoms of asthma, and to compare differences in the efficacy of treatment using OM-85 in adults and children with asthma. We present this article in accordance with the PRISMA reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-22-1469/rc).

Methods

Search strategy and selection criteria

We conducted a systematic literature search of PubMed, Scopus, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang database, and WP (WeiPu) database. The search used the following keywords: “bacterial lysate”, “bacterial extract”, “OM-85”, and “asthma”. There were no language or time restrictions imposed on the search. All identified literature was entered into Endnote. After removing duplicate articles using Endnote, the following outcomes were excluded first: review and meta-analyses, case reports, editorials, preprints, communications and letters, data articles, notes, commentaries, news, brief surveys, errata and retractions, guidelines, and mathematical models. To determine the eligibility of the articles, two reviewers screened the included literature using the following three steps. First, the title of the article was examined. Then, the abstract of the article was examined. Finally, the subject and targeted disease of the article were identified by evaluating the full text of the article. Any disagreement was resolved by discussion with a third reviewer to reach consensus. Articles with computable data obtained from clinical examinations relevant to asthma (such as those of lung function, serum T-lymphocyte subsets, serum cytokine levels, and serum and induced sputum immunoglobulin levels) were included in the current meta-analysis. The study registration number is CRD42022322815, and its registration name is “A systematic review and meta-analysis of the bacterial lysate treatment in adults and children asthma.”

For inclusion in this review, studies had to meet all of the following criteria: (I) study design: randomized controlled trials without language restriction; (II) participants: children and adults diagnosed with any type of asthma; (III) intervention group: patients who received at least one course of OM-85 alone, or OM-85 combined with conventional symptomatic treatment of asthma; (IV) control group: asthma conventional therapy group or placebo alone group; (V) outcome assessment: each study had to provide data on valid or invalid laboratory tests. Exclusion criteria were as follows: (I) study was not a randomized controlled trial; (II) no primary outcome data were available; (III) trials using bacterial lysates other than OM-85; (IV) studies on the intervention of OM-85 in mice.

Data collection

Data were extracted independently by two reviewers. Any disagreement was resolved by discussion or by consulting the third reviewer until consensus was reached. The extracted data included the following information: authors of the study, year of the study, country in which the study was performed, language of the study, study design, sample size (intervention group/control group), groups, adverse events, primary outcomes [including frequency of asthma exacerbation, efficacy of intervention treatment, and predicted Forced expiratory volume in 1 second (FEV₁%)], secondary outcomes [including serum immunoglobulin (IgG, IgM, IgE, or IgA) levels, total serum eosinophil (EOS) count, eosinophilic cationic protein levels, sputum sIgA levels, and proportion of T lymphocyte subtypes (CD3⁺, CD4⁺, CD8⁺ or CD4⁺/CD8⁺). For meta-analysis, the format of laboratory values, presented as median [interquartile range (IQR)], was transformed into mean [standard deviation (SD)]. Data were pooled whenever two or more publications reported a given parameter. If both adults and children were included in a study conducted to analyze a given outcome, adults and children were divided into two subgroups for analysis.

Statistical analysis

In meta-analysis, dichotomous data are presented as relative rates (RRs) with 95% confidence intervals (CI). Continuous data are presented as standard mean differences (SMDs) with 95% CI. When both adults and children were included in studies evaluated in our analysis, subgroup analysis was performed according to age (patients under 14 years old were defined as children, and patients over 18 years old were defined as adults). The I² statistic was used to assess heterogeneity. Heterogeneity was considered low if I² was between 25–50%. I² values between 50% and 75%, and 75% and 100%, indicated moderate and high heterogeneity, respectively. I² values below 25% indicated no heterogeneity. All analyses were performed using Stata se-64. Risk of bias was assessed using the Cochrane risk of bias assessment tool.

Results

Study characteristics

A total of 731 records were identified using database searching. Of these 731 records, 614 records were selected for further assessment. We also assessed 319 full-text reports for inclusion in this meta-analysis. Figure 1 shows a PRISMA flow diagram of our search and eligibility results. We excluded 225 publications mainly because of ineligible study design or lack of patient laboratory data. Finally, 36 eligible publications were included in this review. Of these 36 eligible publications, 33 were published in Chinese and 3 in English. Another Chinese articles did not record the specific number of asthma attacks, nor did data from other laboratory tests, only data related to adverse effects was used for meta-analysis (9). A total of 3,030 patients were enrolled in this study; of these patients, the OM-85-treated group contained 1,551 participants, while the control group contained 1,479 participants. Nineteen studies reported on the rate of symptom improvement and nine studies reported on the frequency of asthma exacerbations. Seventeen and 15 studies analyzed changes in lung function and T lymphocyte subsets, respectively. Sixteen studies reported on immunoglobulin levels in serum or induced sputum, and 7 studies described changes in EOS numbers or ECP levels in serum. Eighteen studies reported on changes in serum cytokine levels in asthma patients. Seventeen trials investigated the adverse effects of OM-85. A total of 31 articles reported on findings obtained in children, and the remaining five studies reported on findings obtained in adults. The essential characteristics of the included studies are presented in Table 1.

Figure 1 Literature search and selection process.

Assessing the risk of bias in included trials

In all the major included studies, the outcome of asthma-related clinical symptoms was assessed using a questionnaire. In some of the studies, description of methodology used for the selection and allocation of trial participants was insufficient for assessing the risk of bias. In addition, unblinding of trial interventions may have also led to bias in non-quantitative data such as clinical symptoms (Figure 2A,2B).

Figure 2 Risk of bias was assessed using the Cochrane risk of bias assessment tool. (A) The summary of risk of bias; (B) each risk of bias item for each included study.

Clinical symptoms of asthma

A total of 19 randomized controlled trials (RCTs) were included in our analysis in order to determine the efficacy of treatment using oral administration of OM-85; we then assessed the number of asthma clinical symptoms, including wheezing and coughing, before and during treatment. There were 898 patients (of whom 817 were children) in the OM-85 treatment group and 879 patients (of whom 798 were children) in the control group. As shown in Figure 3, improvement in total asthma clinical symptoms was 24% greater in the OM-85 treatment group than in the control group (RR =1.23, 95% CI: 1.18–1.28). A subgroup of adult patients showed a 36% improvement in asthma clinical symptoms (RR =1.36, 95% CI: 1.16–1.59), which was higher than the 22% improvement in asthma clinical symptoms observed in a subgroup of pediatric patients (RR =1.22, 95% CI: 1.17–1.27). However, thus far, only two randomized controlled trials have been performed to assess the use of OM-85 in adult patients with asthma; therefore, more clinical trial data are needed to confirm that OM-85 shows greater effectiveness in ameliorating the clinical symptoms of asthma in adult patients than in pediatric patients (Figure 3A).

Figure 3 Forest map of clinical symptoms of asthma. (A) The proportion of improvement in asthma clinical symptoms; (B) the number of asthma exacerbations during treatment.

As shown in Figure 3B, the total number of asthma exacerbations in the experimental group was significantly reduced after treatment using OM-85 compared with that in the control group (SMD: −1.43, 95% CI: −1.62 to −1.24). Subgroup analysis showed that children presented significant reductions in asthma exacerbations after treatment using OM-85 (SMD: −1.78, 95% CI: −1.99 to −1.57). In contrast, a subgroup of adults, included in only one RCT, paradoxically showed a slightly increased number of asthma exacerbations after treatment using OM-85 (SMD: 0.2, 95% CI: 0.25–0.65).

Lung function

Treatment using OM-85 improved percent predicted FEV₁ (FEV₁%) (SMD: 0.65, 95% CI: 0.47–0.84), FEV₁ (SMD: 0.63, 95% CI: 0.48–0.77), FEV1/forced vital capacity (FVC) (SMD: 0.27, 95% CI: −0.10 to 0.63), FVC (SMD: 0.44, 95% CI: 0.19–0.69), and Peak expiratory flow (PEF) (SMD: 0.62, 95% CI: 0.48–0.76) in patients with asthma. Interestingly, a subgroup of children showed greater improvement in FEV₁% (SMD: 0.90, 95% CI: −0.68 to 1.13), compared with the improvement in FEV₁% of adult subjects (SMD: 0.10, 95% CI: −0.24 to 0.43) (Figure S1).

Levels of T-lymphocyte subsets

The children treated with OM-85 showed increased levels of CD3⁺ (SMD: 1.59, 95% CI: 1.45–1.73), CD4⁺ (SMD: 1.63, 95% CI: 1.49–1.76), and CD4⁺/CD8⁺ (SMD: 1.12, 95% CI: 1.00–1.24), as well as decreased concentrations of CD8⁺ (SMD: −2.38, 95% CI: −2.58 to −2.17) compared with those without OM-85 add-on therapy (Figure S2).

Levels of serum immunoglobulin and sputum sIgA

Patients with OM-85 add-on therapy presented higher serum levels of IgA (SMD: 1.11, 95% CI: −0.58 to 1.64), IgG (SMD: 0.34, 95% CI: 0.19–0.49), IgM (SMD: 0.26, 95% CI: 0.11–0.42), and total sputum sIgA (SMD: 0.2, 95% CI: 0.25–0.65), and slightly decreased levels of IgE (SMD: −0.12, 95% CI: −0.49 to −0.24) compared to the controls. Moreover, subgroup analysis showed significantly higher levels of sputum sIgA (SMD: 3.56, 95% CI: 3.18–3.93) in children than in adults (SMD: 1.05, 95% CI: 0.58–1.51). But there were significantly lower levels of serum IgM in children (SMD: 0.18, 95% CI: 0.00–0.36) than in adults (SMD: 0.54, 95% CI: 0.21–0.87) (Figure S3).

The number of peripheral EOS and the levels of ECP and serum cytokine

Regarding eosinophilic inflammation, OM-85 add-on therapy decreased the total number of peripheral EOS (SMD: −1.33, 95% CI: −1.56 to −1.10) and the levels of ECP (SMD: −2.06, 95% CI: −2.33 to −1.78). Intriguingly, children showed a stronger intensity of reduction in peripheral EOS number (SMD: −1.85, 95% CI: −2.11 to −1.59) compared than adults (SMD: 0.22, 95% CI: −0.23 to 0.67). Additionally, our data showed that OM-85 add-on therapy decreased the levels of interleukin-4 (IL-4) (SMD: −1.79, 95% CI: −1.94 to −1.64) and IL-5 (SMD: −2.75, 95% CI: −5.08 to 0.41), whereas increased the concentrations of IL-10 (SMD: 1.29, 95% CI: 0. 91–1.67), IL-12 (SMD: 2.46, 95% CI: 1.79–3.12), and IFN-γ (SMD: 1.34, 95% CI: 1.19–1.48). Similarly, children either presented a greater decrease in IL-4 levels (SMD: −1.92, 95% CI: −2.08 to −1.76) or a higher increase in IFN-γ levels (SMD: 1.40, 95% CI: 1.25–1.56) than adults (Figure S4).

Adverse events

Fifteen trials compared the incidence of adverse events in the experimental and control groups by recording the number of times the patients experienced symptoms such as dizziness, somnolence, nausea, diarrhea, and rash during the 85-OM add-on therapy period. The results showed no significant differences in the incidence of adverse events between patients treated with OM-85 and the control group (RR: 0. 97, 95% CI: 0.94–1.00) (Figure 4).

Figure 4 Adverse event.

Publication bias

Figure S5 shows the generated funnel plots. In the add-on therapy in the OM-85 and control groups, publication bias was readily discernable in the number of asthma exacerbations during treatment, as well as in the FEV1, CD3⁺, CD8⁺, and sputum sIgA levels. Despite the increase in OM-85 studies over the last 2 years, the mechanism underlying OM-85 add-on immunoregulatory therapy remains unclear. There is still a small study effect and more high-quality clinical studies are needed.

Sensitivity analysis

Sensitivity analysis showed that most of the parameters of sensitivity analysis have good stability and robustness. However, several sets of results indicated high sensitivity and heterogeneity. Detailed parameters for each sensitivity analysis are shown in Figure S6.

Heterogeneity

The degree of improvement in the clinical symptoms of asthma, FEV₁, FVC, PEF, serum IgE levels, and adverse events associated with treatment using OM-85 showed little heterogeneity, but all other included variables did (I²>50%). This heterogeneity might have come from any of several factors, such as the demographic and clinical characteristics of included patients, differences in basic treatment, time of symptom onset, laboratory parameters measured, and treatment interventions before admission. Due to the insufficient number of studies on OM-85, we did not further analyze the sources of high heterogeneity in the individual results.

Discussion

Our updated meta-analysis demonstrated that OM-85 add-on therapy could significantly improve asthmatic symptoms, decrease the number of asthma exacerbations, and reduce airway dysfunction. Additionally, treatment with OM-85 showed immune-modulatory effects indicated by elevated levels of serum immunoglobulins, increased numbers of T-lymphocytes and their subsets, and decreased levels of IL-4. Notably, for the first time, we observed that the effects of OM-85 were more prominent in asthmatic children than in adults based on the findings of subgroup analysis. Collectively, OM-85 add-on therapy shows promise as an asthma treatment. Our results indicate that OM-85 has potential applications in anti-asthma therapy, especially in asthmatic children with recurrent airway infections and poor disease control.

OM-85 is composed of non-viable bacterial extracts obtained by chemical lysis of bacterial cultures and lyophilization (46). Orally administered OM-85, absorbed through the gastrointestinal tract, is an effective stimulant that activates the innate and adaptive arms of the immune system, and leads to functional immune responses against the invading pathogens. Since the 1950s, OM-85 has been widely used for the prevention of recurrent respiratory tract infections in several European and Asian countries (47-49). Respiratory tract infection is a major predisposing factor that contributes to asthma exacerbations. Statistically, up to 50% of asthma exacerbations are elicited by respiratory tract infections (50). Because of the imbalanced T1/T2 inflammatory responses observed in asthma, patients with asthma are predisposed toward respiratory tract infections, which causes symptom worsening, decline of pulmonary function, and poor disease control (51). Therefore, strengthening and repair of the airway immune function may be a crucial strategy in asthma treatment. Our results show that add-on treatment using OM-85 was effective in relieving the symptoms of asthma, reducing the number of asthma exacerbations, and improving airway function. Due to immune-modulatory effects of OM-85, detailed application of OM-85 in asthma treatment warrants further study, especially in pediatric patients with recurrent airway viral infections and in adult patients with comorbidities such as chronic obstructive pulmonary disease, chronic bronchitis, and bronchiectasis.

Thus far, the working mechanisms of OM-85 have not been fully characterized. Based on evidence obtained in vitro, in animal models, and in studies of numerous human diseases, the following four cellular mechanisms may be responsible for the clinical effects of OM-85: gut-associated lymphoid tissue (GALT)-mediated activation of dendritic cells, T-lymphocytes, and B-lymphocytes; GALT-generated migration of immune cells into the upper and lower respiratory tract; increased production of immunoglobulins resulting in decreased susceptibility to pathogens; and correction of an imbalance in T1/T2-mediated inflammation (7,52-54). Based on our data, the OM-85 add-on therapy did present immunomodulatory effects such as increased numbers of T-lymphocytes, increased IgA concentration in serum and sputum, elevated levels of T1 inflammatory cytokines, and decreased intensity of T2-mediated inflammatory responses. Although the current study could not discover the potential mechanism, the changes in above immune parameters might serve as an indicator of treatment efficacy and predictor of disease aggression. More basic research is warranted to explore the working mechanisms.

Another finding showed that OM-85 add-on therapy presented more prominent effects in children, compared with those in adults, with asthma. From the time the newborn passes through the birth canal of the mother, humans are continuously exposed to probiotic or harmful bacteria in the external environment via various routes such as the mouth, skin, and respiratory tract. Various bacteria colonizing mucosal sites are essential for healthy human growth; these bacteria also affect the development of the immune system. Intestinal bacteria influence the development of Th17 (55,56), Treg (57), and memory T cells (58-61). Approximately 20% of lymphocytes residing in the gut are exposed to numerous possible foreign immunogens, which affects the occurrence and development of allergic diseases (62-64). Therefore, dysfunction immune homeostasis is considered a major cause of disease development. OM-85 contains numerous pathogen-associated pattern molecules that participate in restoring equilibrium to an impaired immune homeostasis. Given the unformed immune homeostasis in children, the treatment using OM-85 in children seemed to be more advantageous then using it in adults. Additionally, oral OM-85 is well tolerated and shows a good safety profile. Hence, OM-85 can be administered empirically to control or reduce wheezing in children who have not been diagnosed with asthma, especially children who are too young to cooperate with clinical tests, such as tests of lung function. Concurrently, OM-85 can also be used as an adjunct therapy in addition to routine therapy in adult asthma patients.

OM-85 is a mixed lysate of several fixed bacterial genera; it is currently one of the few such therapeutics prepared using standard processes. With improved understanding of immune development, we may be able to optimize the route and timing of bacterial lysate administration, and determine the immunologic mechanisms mediated by these treatment modalities in order to optimize intervention.

Other recent studies support our current findings (65,66). Our present study contributes to existing clinical data on patients with asthma, and to the best of our knowledge, is the first such study to include an adult subgroup treated with OM-85 in a meta-analysis. However, our present study had several limitations. In our meta-analysis, we included a large number of studies conducted in China. Furthermore, unclear descriptions of methodology and study design, and high risk of bias, were present in some of the studies included in our analysis. Thus, the strength of the obtained results may be low for some of the data. In the studies we included, the duration of OM-85 treatment varied widely. For example, the longest treatment period was 360 days and the shortest was only 10 days. We analyzed the improvement in asthma clinical symptoms relative to duration of treatment as subgroups. As shown in Figure 5, there were no significant differences in the improvement of the clinical symptoms of asthma as OM-85 treatment continued. However, we still need more study and data for each subgroup to increase the solidity of this conclusion. In addition, a considerable proportion of analyzed results had moderate or high heterogeneity. Finally, there were only five studies investigating the clinical efficacy of OM-85 in adult patients with asthma. Further analysis of existing literature is required to show whether OM-85 exerts differential therapeutic effects in adults and children with asthma. In summary, our study included numerous studies as sources of analytical data. The various laboratory and lung function tests examined in our current study helped demonstrate the effectiveness of OM-85 as an add-on treatment in asthma. Our analysis of the number of asthma exacerbations, lung function, T lymphocyte subsets, serum immunoglobulin levels, serum EOS numbers, serum IL-4 levels, and other indicators showed that OM-85 was more efficacious in the treatment or control of wheezing in children than as an add-on treatment in adult asthma.

Figure 5 Proportion of improvement in clinical symptoms of asthma (subgroup analysis of treatment duration).

Conclusions

The results of analysis performed in our present study suggest that OM-85 add-on therapy shows promising immunomodulatory effects that significantly improve asthma symptoms and lung function. The clinical benefits of OM-85 add-on treatment seemed to be more pronounced for asthmatic children than adults with asthma. Further studies focusing on the immunomodulatory function of OM-85 in asthma personalized treatment are warranted.

Acknowledgments

We would like to thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.

Funding: This study was supported by the National Natural Science Foundation of China (Nos. 82161138020 and U1801286); the Science and Technology Program of Guangzhou (No. 202102010011)-Zhongnanshan Medical Foundation of Guangdong Province (No. ZNSA-2020003); the Zhongnanshan Medical Foundation of Guangdong Province (No. ZNSA-2020013); It was also sponsored by the Open Project of the State Key Laboratory of Respiratory Disease (No. SKLRD-OP-202004).

Footnote

Reporting Checklist: The authors have completed the PRISMA reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-22-1469/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-22-1469/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-22-1469/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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References

1. Brodin P. Immune-microbe interactions early in life: A determinant of health and disease long term. Science 2022;376:945-50. [Crossref] [PubMed]
2. Renz H, Skevaki C. Early life microbial exposures and allergy risks: opportunities for prevention. Nat Rev Immunol 2021;21:177-91. [Crossref] [PubMed]
3. Pivniouk V, Pivniouk O, DeVries A, et al. The OM-85 bacterial lysate inhibits SARS-CoV-2 infection of epithelial cells by downregulating SARS-CoV-2 receptor expression. J Allergy Clin Immunol 2022;149:923-933.e6. [Crossref] [PubMed]
4. Rantala A, Jaakkola JJ, Jaakkola MS. Respiratory infections in adults with atopic disease and IgE antibodies to common aeroallergens. PLoS One 2013;8:e68582. [Crossref] [PubMed]
5. Fu R, Li J, Zhong H, et al. Broncho-Vaxom attenuates allergic airway inflammation by restoring GSK3β-related T regulatory cell insufficiency. PLoS One 2014;9:e92912. [Crossref] [PubMed]
6. Han L, Zheng CP, Sun YQ, et al. A bacterial extract of OM-85 Broncho-Vaxom prevents allergic rhinitis in mice. Am J Rhinol Allergy 2014;28:110-6. [Crossref] [PubMed]
7. Liu C, Huang R, Yao R, et al. The Immunotherapeutic Role of Bacterial Lysates in a Mouse Model of Asthma. Lung 2017;195:563-9. [Crossref] [PubMed]
8. Navarro S, Cossalter G, Chiavaroli C, et al. The oral administration of bacterial extracts prevents asthma via the recruitment of regulatory T cells to the airways. Mucosal Immunol 2011;4:53-65. [Crossref] [PubMed]
9. Feng GY, He WX, Zhang Y, et al. Effect of Montelukast sodium combined with bacterial dissolution products on elderly asthma. Clinical Medical & Engineering 2009;16:55-6.
10. Feng SZ, Su ZX. Efficacy and safety analysis of budesonide atomization inhalation combined with Famoshu in the treatment of acute attack of bronchial asthma. China Practical Medical 2020;15:109-11.
11. Song JF, Liu A, Li SY, et al. Effect of Fanfushu on SIgA content in induced sputum of asthmatic patients treated with hormone. Journal of Clinical Pulmonary Medicine 2010;15:944-5.
12. Yuan JH, Chen XH. Observation on the effect of Panfushu on bronchial asthma complicated with recurrent respiratory tract infection. Zhejiang Clinical Medical Journal 2007;9:627.
13. Cao J, Yang YZ, Luo TY. Effect of Broncho-Vaxom on Th1/Th2 cell balance and clinical symptoms of patients with acute bronchial asthma. Journal of Clinical Pulmonary Medicine 2016;21:2255-8.
14. Zhang T. Broncho Fanfushu capsule on cough variant asthma children serum IL-4, the influence of IL-10 levels. Shaanxi Journal of Traditional Chinese Medicine 2018;39:449-51.
15. Lv YQ, Zhan P, Gu HM, et al. Changes in cellular immune and inflammatory factors of children with bronchial asthma in treatment with bronchov-axom capsule. Chinese Journal of Difficult and Complicated Cases 2016;15:1170-3.
16. Wu XX. Effect of aerosol inhalation of Broncho-Vaxom combined with be-Clomethasone Propionate Aerosol in the treatment of children with acute attack of bronchial asthma. China Medical Herald 2020;17:102-5.
17. Zhang ZY. Study on the effect of Broncho-Vaxom combined with budesonide on respiratory function and ser-um IL-4 and IL-10 levels in children with asthma. Medical Journal of Liaoning 2021;35:3-6.
18. Chen Y, Zhu F, Li Q. Clinical study on effect of broncho-vaxom combined with budesonide atomization inhalation on immune function of children with bronchial asthma. The Chinese Journal of Clinical Pharmacology 2015;31:409-11.
19. Li X. Effect of Fafoshu combined with Budesonide aerosol in the treatment of children with bronchial asthma and its effect on immune function. Henan Medical Research 2017;26:2249-51.
20. Mao CL. Effect of Fafushu combined with salbutamol atomized inhalation on bronchial asthma in children and its effect on immune function. Henan Medical Research 2020;29:3759-61.
21. Yang F. Effect of broncho-Vaxom combined with atomization inhaled budesonide onT lymphocytes in acute attack of child bronchial asthma. Laboratory Medicine and Clinic 2017;14:1570-2.
22. Zhang HY, Pang BD, Liu FZ, et al. Observation on the efficacy and safety of Fanfushu in preventing recurrent respiratory tract infection in infants with asthma. The Journal of Practical Medicine 2007;23:3427-8.
23. Hu BL, Luo YW, Qian XB, et al. Clinical Efficacy of Fluticasone Plus Combined with Bacterial Lysates in Treatment of Children with Asthma. China Modern Doctor 2011;49:83-5.
24. Chen ZG, Jing JZ, Li M, et al. Effect and Analysis of Clinical Efficacy of Immunomodulator on Serum Levels of IL-4 and IFN-γ in Asthmatic Children. Journal of Sun Yat-sen University Medical Sciences 2009;30:100-3.
25. Li XQ. Clinical effect of bacteria-soluble product (Famosulum) combined with glucocorticoid and leukotriene modulator in the treatment of children with asthma. The Journal of Medical Theory and Practice 2017;30:680-1.
26. Zhang SL, Gu YX, Hu JY. Curative Efficacy of Broncho-vaxom in Pediatric Asthma and Its Effect on Serum IL-4, IFN-γ and IgE. Journal of Guizhou Medical University 2014;39:54-6.
27. Gao Y, Qian XB, Yu CY, et al. Therapeutic efficacy of bacterial lysates and montelukast treatment in children with intermittent asthma. Chinese Journal of Clinical Pharmacology and Therapeutics 2010;15:547-50.
28. Hao LX. Clinical research of Broncho-Vaxom combined with corticosteroids and leukotriene modifier in the treatment of children with asthma. Journal of Clinical Pulmonary Medicine 2016;21:694-7.
29. Song FJ, Liu A, Li SY, et al. The clinic effect of concentration of SIgA in induced sputum from the asthma patients treated with steroid or and with Broncho-Vaxom. Journal of Clinical Pulmonary Medicine 2011;16:875-6.
30. Xiong MM, Du LL. Impact of Broncho-vaxom to SIgA Content of Induced Sputum of Asthma Patients. Medical Information 2013;269.
31. Zhang W. Clinical observation on the adjuvant treatment of children bronchial asthma with Fanfushu. Guide of China Medicine 2015;13:70-1.
32. Li Y, Shen ZB, Zhang J, et al. Effect of budesonide suspension combined with broncho-vaxom on lung function in children with API positive wheezing. International Medical and Health Guide 2020;26:3732-4.
33. Yang X, Lu LQ, Huang L, et al. A Clinical Study on Broncho-vaxom Capsules in Adjuvant Therapy of Children with Bronchial Asthma. Progress in Modern Biomedicine 2017;17:1949-52.
34. Qian DL, Gao X, Li XX, et al. Clinical trial of Fanfusu Capsules in the treatment of children with bronchial asthma. The Chinese Journal of Clinical Pharmacology 2020;36:3407-9.
35. Liao JY, Zhang T. Influence of OM-85 BV on hBD-1 and immunoglobulin in children with asthma and recurrent respiratory tract infection. Chinese Journal of Contemporary Pediatrics 2014;16:508-12. [PubMed]
36. Cai JR, Lin ZL, Wang DF, et al. Effect of Broncho-Vaxom on immune function and asthma control level in children with positive asthma pre-diction index. Journal of Clinical Pulmonary Medicine 2020;25:74-7.
37. Yang LW, Zhang YL, Liu X, et al. Clinical Effect of Immunomodulator on Acute Exacerbations of Bronchial Asthma in Children and Its Influ-ence on Immune Function, ECP and FENO. Clinical Misdiagnosis & Mistherapy 2020;33:26-31.
38. Wang PS. Effect of salbutamol atomization combined with bacterial lysate capsule in the treatment of children with bronchial asthma and changes of T lymphocyte subsets. The Journal of Medical Theory and Practice 2021;34:2205-2207.
39. Tang YQ, Zhao DH, Sun WJ, et al. Clinical Observation of Bacterial Lysates Capsules in the Treatment of Acute Attack of Asthma in Children. China Pharmacy 2017;28:4537-40.
40. Yang SB. Effect of bacterial lysates combined with Salmeterol-Fluticasone powder inhalation in bronchial asthma. Chinese Journal of Microecology 2020;32:669-73.
41. Zhang YJ, Sun Y, Zhao XX. Clinical research on bacterial lysates in prevention of wheezing onset induced by viral infection among preschool cluldren. Maternal & Child Health Care of China 2011;26:3904-6.
42. Zhang H, Ding D. Clinical effect of oxygen-driven nebulized inhalation of glucocorticoid combined with bacterial dissolving product capsule in the treatment of children with acute attack of bronchial asthma. Medical Equipment 2019;32:14-5.
43. Han RF, Li HY, Wang JW, et al. Study on clinical effect and immunologic mechanism of infants capillary bronchitis secondary bronchial asthma treated with bacterial lysates Broncho-Vaxom. Eur Rev Med Pharmacol Sci 2016;20:2151-5. [PubMed]
44. de Boer GM, Braunstahl GJ, van der Ploeg EK, et al. Bacterial lysate add-on therapy to reduce exacerbations in severe asthma: A double-blind placebo-controlled trial. Clin Exp Allergy 2021;51:1172-84. [Crossref] [PubMed]
45. Lu Y, Li Y, Xu L, et al. Bacterial lysate increases the percentage of natural killer T cells in peripheral blood and alleviates asthma in children. Pharmacology 2015;95:139-44. [Crossref] [PubMed]
46. Huang Y, Pei Y, Qian Y, et al. A Meta-Analysis on the Efficacy and Safety of Bacterial Lysates in Chronic Obstructive Pulmonary Disease. Front Med (Lausanne) 2022;9:877124. [Crossref] [PubMed]
47. Zhang W, Huang J, Liu H, et al. Whether Immunostimulants Are Effective in Susceptible Children Suffering From Recurrent Respiratory Tract Infections: A Modeling Analysis Based on Literature Aggregate Data. J Clin Pharmacol 2022;62:245-53. [Crossref] [PubMed]
48. Cantarutti A, Barbieri E, Scamarcia A, et al. Use of the Bacterial Lysate OM-85 in the Paediatric Population in Italy: A Retrospective Cohort Study. Int J Environ Res Public Health 2021;18:6871. [Crossref] [PubMed]
49. Marengo R, Ortega Martell JA, Esposito S. Paediatric Recurrent Ear, Nose and Throat Infections and Complications: Can We Do More? Infect Dis Ther 2020;9:275-90. [Crossref] [PubMed]
50. Sallard E, Schult F, Baehren C, et al. Viral Infection and Respiratory Exacerbation in Children: Results from a Local German Pediatric Exacerbation Cohort. Viruses 2022;14:491. [Crossref] [PubMed]
51. Fragkou PC, Moschopoulos CD, Reiter R, et al. Host immune responses and possible therapeutic targets for viral respiratory tract infections in susceptible populations: a narrative review. Clin Microbiol Infect 2022;28:1328-34. [Crossref] [PubMed]
52. Holt PG, Strickland DH. Low dose treatment of mice with bacterial extract (OM-85) for attenuation of experimental atopic asthma in mice. Allergol Immunopathol (Madr) 2017;45:310-1. [Crossref] [PubMed]
53. Pivniouk V, Gimenes-Junior JA, Ezeh P, et al. Airway administration of OM-85, a bacterial lysate, blocks experimental asthma by targeting dendritic cells and the epithelium/IL-33/ILC2 axis. J Allergy Clin Immunol 2022;149:943-56. [Crossref] [PubMed]
54. Kaczynska A, Klosinska M, Janeczek K, et al. Promising Immunomodulatory Effects of Bacterial Lysates in Allergic Diseases. Front Immunol 2022;13:907149. [Crossref] [PubMed]
55. Kawano Y, Edwards M, Huang Y, et al. Microbiota imbalance induced by dietary sugar disrupts immune-mediated protection from metabolic syndrome. Cell 2022;185:3501-3519.e20. [Crossref] [PubMed]
56. Ivanov II, Tuganbaev T, Skelly AN, et al. T Cell Responses to the Microbiota. Annu Rev Immunol 2022;40:559-87. [Crossref] [PubMed]
57. Lyu M, Suzuki H, Kang L, et al. ILC3s select microbiota-specific regulatory T cells to establish tolerance in the gut. Nature 2022;610:744-51. [Crossref] [PubMed]
58. Campion SL, Brodie TM, Fischer W, et al. Proteome-wide analysis of HIV-specific naive and memory CD4(+) T cells in unexposed blood donors. J Exp Med 2014;211:1273-80. [Crossref] [PubMed]
59. Jensen IJ, Farber DL. Gutsy memory T cells stand their ground against pathogens. Sci Immunol 2022;7:eade7168. [Crossref] [PubMed]
60. Fu J, Sykes M. Emerging Concepts of Tissue-resident Memory T Cells in Transplantation. Transplantation 2022;106:1132-42. [Crossref] [PubMed]
61. Noble A, Pring ET, Durant L, et al. Altered immunity to microbiota, B cell activation and depleted γδ/resident memory T cells in colorectal cancer. Cancer Immunol Immunother 2022;71:2619-29. [Crossref] [PubMed]
62. Ganusov VV, De Boer RJ. Do most lymphocytes in humans really reside in the gut? Trends Immunol 2007;28:514-8. [Crossref] [PubMed]
63. Huang C, Li F, Wang J, et al. Innate-like Lymphocytes and Innate Lymphoid Cells in Asthma. Clin Rev Allergy Immunol 2020;59:359-70. [Crossref] [PubMed]
64. Thomas CM, Peebles RS Jr. Development and function of regulatory innate lymphoid cells. Front Immunol 2022;13:1014774. [Crossref] [PubMed]
65. Li C, Zhou H, Zhang W, et al. Bacterial lysate treatment in allergic disease: A systematic review and meta-analysis. Pediatr Allergy Immunol 2021;32:1813-23. [Crossref] [PubMed]
66. de Boer GM, Żółkiewicz J, Strzelec KP, et al. Bacterial lysate therapy for the prevention of wheezing episodes and asthma exacerbations: a systematic review and meta-analysis. Eur Respir Rev 2020;29:190175. [Crossref] [PubMed]