Polybacterial immunomodulator Respivax restores the inductive function of innate immunity in patients with recurrent respiratory infections

Immunostimulants versus placebo for preventing exacerbations in adults with chronic bronchitis or chronic obstructive pulmonary disease

BACKGROUND

Individuals with chronic obstructive pulmonary disease (COPD) or chronic bronchitis may experience recurrent exacerbations, which negatively impact prognosis and quality of life, and can impose a significant socioeconomic burden on the individual and wider society. Immunostimulants are a broad category of therapies that may theoretically enhance non-specific immunity against several respiratory insults, thereby reducing exacerbation risk and severity. However, evidence to date for their use in this population is limited.

OBJECTIVES

To determine the efficacy of immunostimulants in preventing respiratory exacerbations in adults with chronic obstructive pulmonary disease, chronic bronchitis, or both.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest literature search was conducted on 25 January 2022.  SELECTION CRITERIA: We included parallel randomised controlled trials (RCTs) that compared immunostimulant therapy, administered by any method and with the intention of preventing (rather than treating) exacerbations, with placebo for a minimum treatment duration of one month in adults with chronic bronchitis or COPD, or both. We excluded participants with other respiratory conditions.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were number of participants with no exacerbations during the study period and all-cause mortality, secondary outcomes were respiratory-related mortality, quality of life, number of participants requiring antibiotics, exacerbation duration, respiratory-related hospitalisation duration and adverse events/side effects. We used GRADE to assess certainty of evidence for each outcome.

MAIN RESULTS

This review included 36 studies involving 6192 participants. Studies were published between 1981 and 2015. Duration ranged from three to 14 months. The mean age of study participants varied between 35.2 and 82 years. Twelve studies examined participants with COPD only. Seventeen studies reported baseline lung function values; most indicated a moderate-to-severe degree of airflow limitation. Nineteen studies indicated inclusion of participants with a mean baseline exacerbation frequency of two or more in the preceding year. Immunostimulants investigated were OM-85, AM3, RU41740 (Biostim), Ismigen, Diribiotine CK, thymomodulin, pidotimod, D53 (Ribomunyl), Lantigen B, Symbioflor, and hyaluronan; routes of administration were oral, sublingual, and subcutaneous. The risk of bias of the included studies was mostly low or unclear. Participants receiving immunostimulants for a mean duration of six months were slightly more likely to be free of exacerbations during that time (odds ratio (OR) 1.48, 95% confidence interval (CI) 1.15 to 1.90; 15 RCTs, 2961 participants; moderate-certainty evidence). The overall number needed to treat with immunostimulants for a mean of six months, to prevent one participant from experiencing an exacerbation, was 11 (95% CI 7 to 29). This outcome was associated with a moderate degree of unexplained heterogeneity (I2 = 53%). Type of immunostimulant, baseline lung function, baseline exacerbation frequency, treatment duration, and follow-up duration did not modify the effect size, although due to heterogeneity and limited study and participant numbers within some subgroups, the validity of the subgroup treatment effect estimates were uncertain. Immunostimulants probably result in little to no difference in all-cause mortality (OR 0.64, 95% CI 0.37 to 1.10; 5 RCTs, 1558 participants; moderate-certainty evidence) and respiratory-related mortality (OR 0.40, 95% CI 0.15 to 1.07; 2 RCTs, 735 participants; low-certainty evidence) compared to placebo; however, the effects were imprecise and data quality limited the certainty of these results.  There was a small improvement in health-related quality of life, as measured by the St George's Respiratory Questionnaire (SGRQ), with immunostimulant compared to placebo (mean difference -4.59, 95% CI -7.59 to -1.59; 2 RCTs, 617 participants; very-low certainty evidence). The effect estimate just met the minimum clinically important difference (MCID) score of 4 units; however, the CI width means the possibility of a non-meaningful difference cannot be excluded. The pooled result from five studies indicated that immunostimulants likely reduce the number of participants requiring antibiotics over a mean duration of six months (OR 0.34, 95% CI 0.18 to 0.63; 542 participants; moderate-certainty evidence). This outcome had a low-to-moderate degree of heterogeneity (I2 = 38%), but the direction of effect was consistent across all studies. There was no evidence of a difference in the odds of experiencing an adverse event with immunostimulant compared to placebo, over a mean duration of six months (OR 1.01, 95% CI 0.84 to 1.21; 20 RCTs, 3780 participants; high-certainty evidence). The CI limits for the associated risk ratio (RR) did not cross thresholds for appreciable harm or benefit (RR 1.02, 95% CI 0.92 to 1.13). An additional seven studies reported no events rates in either study arm. Meta-analyses were not performed for the outcomes of exacerbation duration and respiratory-related hospitalisation duration, due to high levels of heterogeneity across the included studies (exacerbation duration: I2 = 92%; respiratory-related hospitalisation duration: I2 = 83%). Results from an effect direction plot and binomial probability test for exacerbation duration indicated that a significant proportion of studies (94% (95% CI 73% to 99%); P = 0.0002) favoured intervention, possibly indicating that immunostimulants are efficacious in reducing the mean exacerbation duration compared to placebo. However, the degree of uncertainty associated with this estimate remained high due to data quality and heterogeneity. Three studies reported mean duration of respiratory-related hospitalisation, two of which demonstrated a direction of effect that favoured immunostimulant over placebo.

AUTHORS' CONCLUSIONS

In participants with chronic bronchitis or COPD, we are moderately confident that treatment with immunostimulants is associated with a small reduction in the likelihood of having an exacerbation and a moderate reduction in the requirement for antibiotics. Low numbers of events limit interpretation of the effect of immunostimulants on all-cause and respiratory-related mortality. We are uncertain whether immunostimulants improve quality of life, and whether they are associated with a reduction in exacerbation and respiratory-related hospitalisation durations, although immunostimulants were generally associated with a positive effect direction in the studies that examined these outcomes. Immunostimulants appear to be safe and well-tolerated, and are not associated with an increased risk of adverse events.

Immunostimulants for preventing respiratory tract infection in children: A systematic review and meta-analysis

Childhood acute respiratory tract infections (ARTIs) are a significant cause of morbidity and mortality, so, immunostimulants have been used as a preventative measure. Despite this, there is no updated evidence regarding the safety and efficacy of immunostimulant drugs for this purpose. This study aimed to determine the effectiveness and safety of immunostimulants in preventing ARTIs in children based on the most recent scientific evidence. Data sources such as PubMed, Cochrane Central Register of Controlled Trials, Embase, Google Scholar, and Scopus were searched from 1965 to 10 January 2022 to identify randomized controlled trials (RCTs) comparing immunostimulants administered by any method, with placebo to prevent ARTIs on children under 18 years of age without immunodeficiencies, anatomical, genetic, or allergic conditions. In order to analyze data from the studies, we used Review Manager 5.4 (The Cochrane Collaboration, 2020), assessed the certainty of the evidence with Grading of Recommendations, Assessment, Development and Evaluations (GRADE), and assessed the quality and risk of bias of the studies using the RoB tool 1.0. Further, outcomes were combined and analyzed using meta-analysis, subgroup analysis, and sensitivity analysis. Throughout the review, we included 72 placebo-controlled clinical trials involving 12,229 children. The meta-analyses, however, included only 38 studies (52.8%) with 4643 children (38% of the total) with data on mean number of ARTIs. These studies demonstrated a reduction in the ARTIs (MD –1.12 [95%CI –1.39 to −0.85]) and ratio of means of ARTIs (0.61 [95%CI 0.54–0.69]), corresponding to a percentage reduction of 39% (95%CI, 46%–31%) with moderate-quality data. Nevertheless, since there was considerable to substantial heterogeneity and bias was unclear in all domains in 32 out of 72 trials, the quality of the evidence for efficacy was deemed low. Only 14 trials reported adverse events.

The review indicates that immunostimulants reduce the incidence of ARTIs by 40% on average in susceptible children, despite low-quality evidence, heterogeneity, and the possibility of publication bias. However, further studies are needed to establish immunostimulants' safety and efficacy profiles.

This review was conducted without the support of any funding and has no registered number.

Current Stage in the Development of Klebsiella pneumoniae Vaccines

Klebsiella pneumoniae is a bacterium capable of colonizing mucous membranes, causing serious infections. Widespread antibiotic resistance in K. pneumoniae—either through intrinsic mechanisms or via acquisition from different species, especially in hospital environments—limits the therapeutic options against this pathogen, further aggravating the disease burden. To date, there are no vaccines available against K. pneumoniae infection. Although formulations based on capsular polysaccharides have been proposed, the high variability in capsular serotypes limits vaccine coverage. Recombinant vaccines based on surface exposed bacterial antigens are a promising alternative owing to their conservation among different serotypes and accessibility to the immune system. Many vaccine candidates have been proposed, some of which have reached clinical trials. The present review summarizes the current status of K. pneumoniae vaccine development. Different strategies including whole cell vaccines, outer membrane vesicles (OMVs), ribosome, polysaccharide, lipopolysaccharide (LPS), and protein-based formulations are discussed. The contribution of antibody and cell-mediated responses is also presented. In summary, K. pneumoniae vaccines are feasible and a promising strategy to prevent infections and to reduce the antimicrobial resistance burden worldwide.

Lessons from Bacillus Calmette-Guérin: Harnessing Trained Immunity for Vaccine Development

Vaccine design traditionally focuses on inducing adaptive immune responses against a sole target pathogen. Considering that many microbes evade innate immune mechanisms to initiate infection, and in light of the discovery of epigenetically mediated innate immune training, the paradigm of vaccine design has the potential to change. The Bacillus Calmette-Guérin (BCG) vaccine induces some level of protection against Mycobacterium tuberculosis (Mtb) while stimulating trained immunity that correlates with lower mortality and increased protection against unrelated pathogens. This review will explore BCG-induced trained immunity, including the required pathways to establish this phenotype. Additionally, potential methods to improve or expand BCG trained immunity effects through alternative vaccine delivery and formulation methods will be discussed. Finally, advances in new anti-Mtb vaccines, other antimicrobial uses for BCG, and “innate memory-based vaccines” will be examined.

Evaluation of the presence of reduced nicotinamide adenine dinucleotide phosphate in bacterial metabolites used as immunostimulators and its role in nitric oxide induction

Bacterial metabolites that act as immunostimulators have aroused interest because of their therapeutic potential in several immune disorders. These metabolites are complex, heterogeneous, and comprise numerous immune-boosting biomolecules. To better understand their immune stimulatory properties, characterization of their components is essential. An ether extract of metabolites from nine bacterial species was analyzed for the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) or other fluorophores. This metabolite in combination with bile lipids is a licensed immune stimulatory drug. Excitation of the extract at 340 nm resulted in fluorescence with an emission maximum of around 410 nm, which is fairly specific for NADH and NADPH. Reverse-phase-HPLC and electro-spray ionization-mass analysis confirmed the presence of NADPH in the bacterial metabolites. Quantification by glutathione reductase assay indicated 11.90 ± 0.01 µM of NADPH in the metabolites. Further characterization of the individual bacterial extracts of the metabolite confirmed the presence of NADPH. Subsequently, studies were performed to evaluate the role/s of NADPH in immune-stimulatory drugs. NADPH is known to be involved in production of nitric oxide (NO), which has versatile roles in the immune system. The biological function of NADPH in NO induction by RAW 264.7 (mouse macrophage) cells was evaluated and it was found that bacterial NADPH has a significant role in inducing NO and that NADPH from individual bacterial extracts is capable of inducing NO. Investigation on the stability and biological potency of NADPH in bacterial metabolites is important because of NADPH's wide therapeutic applications, most of which are associated with its role in NO induction.

Collagenases in an ether extract of bacterial metabolites used as an immunostimulator induces TNF-α and IFN-γ

Non-specific immunostimulation by bacterial extracts and their components are widely accepted for the prevention and treatment of several infectious diseases. An ether extract of the metabolites of ß-streptococcus, Staphylcoccus albus, Staphylcoccus aureus, Escherichia coli, Haemophilus influenza, Moraxella caterhalis, Salmonella typhi (standard O & H), Salmonella paratyphi (A & B) and Diptheroid bacilli along with bile lipids is used as a licensed drug for immunostimulation. While characterizing the drug, we observed gelatinolytic/collagenolytic activity in the ether extract by zymography. This activity was contributed by each bacterial species as observed by collagen zymography of individual extract. Immuno-blot also confirmed the presence of collagenases in the pooled extract whose activity was estimated to be 0.081 U/ml ± 0.005 by DQ-gelatin assay. The enzyme was purified by immuno-affinity chromatography. Homogeneity of the preparation was demonstrated by SDS-PAGE and SE-HPLC. Degradation of collagen by purified collagenases was visualized by atomic force microscopy and transmission electron microscopy wherein, fragmentation of collagen leading to loss of network structure occurred under physiological conditions. Results indicated that purified collagenases can trigger the release of pro-inflammatory cytokines TNF-α and IFN-γ in-vitro and in-vivo without inducing detectable stress and toxicity on both models. The findings suggest that bacterial collagenases remain stable and biological functional in an organic solvent validating its potential for industrial and medical applications as the enzymes are key regulators of inflammatory and immune responses.

Immunostimulants for preventing respiratory tract infection in children

BACKGROUND

Acute respiratory tract infections (ARTIs) are a major cause of childhood morbidity and mortality. Immunostimulants (IS) may reduce the incidence of ARTIs.

OBJECTIVES

To determine the efficacy and safety of IS in preventing ARTIs in children.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2005); MEDLINE (January 1966 to January 2006); and EMBASE (January 1990 to January 2006); PASCAL (up to January 2006); SciSearch (up to January 2006); and IPA (up to January 2006) for reports of trials. Investigators in the field were also contacted. Ongoing studies were searched in the trial registration web site, metaRegister of Controlled Trials.

SELECTION CRITERIA

All comparative trials which enrolled patients less than 18 years of age were included. The intervention of interest was the use of an IS medication administered by any method for preventing ARTIs. Clinical trials using random or quasi-random allocation and comparing IS medication or medications to placebo were included.

DATA COLLECTION AND ANALYSIS

The outcome on ARTIs was analyzed both as the mean number of ARTIs by group and as a percent change in the rate of ARTIs. Meta-analysis was undertaken using a random-effects model and results were presented as weighted mean differences (WMD) with 95% confidence intervals (CI). The trials search, quality assessment and data extraction were undertaken independently by two authors. A funnel plot suggested there may be publication bias in the trials identified.

MAIN RESULTS

Thirty-four placebo controlled trials (3877 participants) provided data in a form suitable for inclusion in the meta-analysis. When compared with placebo, the use of IS was shown to reduce ARTIs measured as the total numbers of ARTIs (WMD -1.27; 95% CI -1.58 to -0.97) and the difference in ARTIs rates (WMD -39.68%; 95% CI -47.27% to -32.09%). The trial quality was generally poor and a high level of statistical heterogeneity was evident. The subgroup analysis of bacterial IS studies produced similar results, with lower heterogeneity. No difference in adverse events was evident between the placebo and IS groups

AUTHORS' CONCLUSIONS

This review showed that IS reduces the incidence of ARTIs in children, by 40% on average. However, due to significant heterogeneity and the poor quality of the trials this positive result should be interpreted with caution. The safety profile of IS appears to be good. Further high-quality trials are needed and we encourage national health authorities to conduct large, multicenter, double-blind, placebo-controlled trials on the role of IS in the prevention of ARTIs.