The immunostimulant RU41740 from Klebsiella pneumoniae activates human cells in whole blood to potentially stimulate innate and adaptive immune responses

Human vaccine candidates for infections caused by Klebsiella pneumoniae: A systematic review

Background and Aims

There are many difficulties in treating Klebsiella pneumoniae, necessitating the creation of more preventative/therapeutic measures like vaccinations. However, after numerous attempts, there is still no authorized and widely accessible vaccine. The present study aimed to systematically review published studies on K. pneumoniae vaccines in human subjects/samples.

Methods

To find published studies, several electronic databases, including Scopus, PubMed, Web of Science, ClinicalKey, ClinicalTrials.gov, and Cochrane Library were searched without time limitation using the appropriate keywords. Studies were scrutinized, and the information from those that met our inclusion criteria was gathered and analyzed.

Results

In total, 691 studies were found, of which 14 articles were included for systematic review. Bacterial lysate containing K. pneumoniae was the most studied vaccine candidate. As the main indicator of human immune responses to K. pneumoniae, antibody responses were determined by most studies. The antigen amount, the route of immunization, and the immunization schedule were varying in the studies and were chosen based on several factors such as the disease model, the vaccine type, the vaccination setting (prophylactic or therapeutic), and so on.

Conclusion

The majority of studies asserted that their vaccination was efficient and safe, which was demonstrated by a decrease in the rate of infections and the induction of protective antibody, cell-dependent, and/or cytokine responses. Altogether, the information provided here will help researchers examine the K. pneumoniae vaccine candidates more closely and take future actions that will be more consistently successful.

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.

The enhancing effect of Klebsiella pneumoniae lysate on cellular immunity

Cellular immunity plays important roles in clearing intracellular pathogens or tumor cells. It is of significance to develop an adjuvant able to efficaciously induce cellular immunity, but such an approved adjuvant is not currently available. Klebsiella pneumoniae ( K. pneumoniae) possesses lipopolysaccharide and capsular polysaccharide, both of which have been demonstrated to be able to induce humoral immunity. In this study, we investigated the effect of K. pneumoniae on epidermal cellular immunity, in vitro. The effects of K. pneumoniae on the maturation of Langerhans cells (LCs), the capacity to induce T-cell proliferation, and the secretion of interferon gamma (IFN-γ) by T cells were examined. The results showed that K. pneumoniae induced significant upregulation of CD86 and human leukocyte antigen-deterodimer (HLA-DR) levels on LCs, but not CD40 and CD80. K. pneumoniae-loaded LCs induced significant CD4+ and CD8+ T-cell proliferation. Significant increases in extracellular IFN-γ secretion by CD4+ and CD8+ T cells stimulated with K. pneumoniae-pulsed LCs using enzyme-linked immunospot assay (ELISPOT) were demonstrated, while only a part of the subjects showed increases in intracellular secretion of IFN-γ using intracellular staining assay. In sum, K. pneumoniae has the potential to enhance epidermal cellular immunity and may act as a potential adjuvant in intradermal vaccines designed to enhance cellular immunity.

Aloe arborescens Polysaccharides: In Vitro Immunomodulation and Potential Cytotoxic Activity

Different polysaccharides were isolated from the leaves of Aloe arborescens using the gradient power of hydrogen followed by antitumor and immunomodulatory assay. The total polysaccharide content of different fractions, water-soluble polysaccharide (WAP), acid-soluble polysaccharide (ACP), and alkaline-soluble polysaccharide (ALP), was estimated using a phenol-sulfuric acid spectrophotometric method. WAP possessed a higher content of mannose and glucose than either ACP or ALP. In vitro antitumor activity was investigated in three different cancer cell lines, and in vitro immunomodulatory potential was assessed through phagocytosis and lymphocyte transformation assay. The results showed that WAP and ALP exhibited the most significant cytotoxicity against HepG2 human liver cancer cells, with IC₅₀ values of 26.14 and 21.46 μg/mL, respectively. In contrast, ALP was able to enhance lymphocyte transformation, whereas WAP had the most potent phagocytic activity. Molecular weight, total sugar and uronic acid content, Fourier transform-infrared analysis, and linkage type of bioactive polysaccharides were investigated. These findings revealed that the potential antitumor activity of the natural agents WAP and ALP was through an immunomodulation mechanism, which verifies the use of the plant as adjuvant supplement for cancer patients suffering immunosuppression during chemotherapy.

In vitro immunocompetence of two compounds isolated from Polygala tenuifolia and development of resistance against grass carp reovirus (GCRV) and Dactylogyrus intermedius in respective host

The present study was undertaken to isolate some compounds from methanol extract of Polygala tenuifolia and evaluate their immunostimulatory properties and antiviral activity using grass carp Ctenopharyngodon idella kidney (CIK) cells and GCRV. By applying insecticidal bioassay-guided, chromatography techniques and successive recrystallization, two purified compounds were obtained. The changes of expression of selected immune genes (Mx1, IL-1β, TNFα, MyD88 and IgM) in C. idella kidney cell lines were evaluated after exposure to these isolated compounds. The results showed that compound 1 and 2 up-regulated to varying degrees of Mx1, IL-1β, TNFα, and MyD88 in C. idella kidney cells. WST-8 kit assay verified the two compounds has no toxic effects on CIK cell, and furthermore, have in vitro antivirus activity. Especially, that there is keeping 79% cell viability when exposure to compound 2 (100 mg L(-1)). According to in vivo insecticidal assays against Dactylogyrus intermedius, compound 2 exhibited higher efficacy than compound 1, which was found to be 87.2% effective at the concentrations of 5 mg L(-1) and safe to goldfish (Carassius auratus). Besides, the purified compounds were identified by spectral data as: (1) 1,5-Anhydro-D-glucitol and (2) 3,4,5-trimethoxy cinnamic acid. Overall, the results indicate that bath administration of these compounds modulates the immune related genes in C. idella kidney cells and to some extent, eliminate the virus and parasitic infections.

Bacterial extracts for the prevention of acute exacerbations in chronic obstructive pulmonary disease: a point of view

Given the high prevalence of chronic obstructive pulmonary disease (COPD), the impact of exacerbations on quality of life, and the costs incurred, effective ways for the prevention of exacerbations, and for reductions in the severity and duration of COPD symptoms are needed. Bacterial immunostimulation has been advocated as a management strategy in COPD for the purposes of preventing acute exacerbations. In particular, it suggests that the use of oral multicomponent vaccines may reduce the severity and duration of acute episodes. The way in which bacterial extracts may exert their effects is not fully understood although a number of possible specific mechanisms have been suggested. Given the high prevalence of COPD worldwide and the high cost of acute exacerbations, some cost-effectiveness analyses suggest that bacterial immunostimulants may become a key element in the improved control of this condition. Nonetheless, larger and longer clinical trials are needed to investigate efficacy before oral vaccination could be recommended as part of the routine clinical management of COPD, mainly in advanced COPD. It remains also to be investigated whether this protective effect may be additive to the other treatments. In any case, it is well known that for Streptococcus pneumoniae, non-typable Haemophilus influenzae and Moraxella catarrhalis, recurrent infections occur because of strain heterogeneity. Therefore, a single or even multiple strain vaccine with a killed whole cell formulation is possibly not the ideal vaccine. Moreover, the method of inactivation can affect the immunogenicity of essential antigens through denaturation. For this reason, the efficacy of bacterial immunostimulants should not only be assessed but also compared.

The role of G-CSF and IL-6 in the granulopoiesis-stimulating activity of murine blood serum induced by perorally administered ultrafiltered pig leukocyte extract, IMUNOR®

IMUNOR, a low-molecular weight (< 12 kD) ultrafiltered pig leukocyte extract, has been previously found to have significant stimulatory effects on murine hematopoiesis supressed by ionizing radiation or cytotoxic drugs. This communication shows data on the mechanisms of these effects. Using ELISA assay, significantly increased levels of granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) were observed. On the contrary, no detectable levels of granulocyte-macrophage colony-stimulating factor (GM-CFC) and interleukin-3 (IL-3) have been found in blood serum of IMUNOR-treated mice. Incubation of the serum from IMUNOR-treated mice with antibodies against G-CSF caused abrogation of the ability of the sera to stimulate in vitro growth of colonies originating from granulocyte-macrophage progenitor cells (GM-CFC). In contrast, incubation of the serum with antibodies against IL-6 did not change its colony-stimulating activity. It may be inferred from these findings that G-CSF is probably the main cytokine responsible for the granulopoiesis-stimulating effects of IMUNOR. When the serum from IMUNOR-treated mice with G-CSF inactivated by anti-G-CSF antibodies (but with elevated IL-6) was added to cultures of bone marrow cells together with a suboptimum concentration of IL-3, a significant increase in the numbers of GM-CFC colonies was found. Moreover, conjoint inactivation of G-CSF and IL-6 significantly decreased the numbers of GM-CFC colonies in comparison with those observed when only G-CSF was inactivated. This observation strongly suggests that though IMUNOR-induced IL-6 is not able to induce the growth of GM-CFC colonies alone, it is able to potentiate the hematopoiesis-stimulating effect of IL-3. These findings represent a new knowledge concerning the hematopoiesis-stimulating action of IMUNOR, a promising immunomodulatory agent.

Peripheral blood CD161+ T cells from asthmatic patients are activated during asthma attack and predominantly produce IFN-gamma

In humans, T cells expressing the CD161 molecule NKR-P1A constitute around 20% of the circulating CD3(+) cells and are potentially immunoregulatory in several diseases. Their role in asthma is not well known, but they could participate in asthma attacks. To determinate whether activation of CD161(+) T cells and their cytokine production correlate with clinical status of asthma, we analysed blood samples from asthma attack patients (AAP) and stable asthma patients (SAP) in comparison with healthy non-atopic controls (HC). There was a significant higher baseline expression of CD69 on T cells from AAP and the difference was more notorious on CD161(+) T cells; upregulation of CD69 was observed on both CD161(-) and CD161(+) T cells driven by Dermatophagoides pteronyssinus crude extract, whereas polyclonal stimulation with phorbol 12-myristate 13-acetate plus ionomycin predominantly induced IFN-gamma but no IL-4, IL-5 and IL-13 by CD161(+) T cells in all groups; upon polyclonal stimulation, there were more CD161(+) T cells producing IFN-gamma and less CD161(-) T cells producing this cytokine, contrasting with the opposite results observed in SAP and HC groups. Our results indicate that, during asthma attack, CD161(+) T cells are activated and are able to produce predominantly IFN-gamma but no Th2 cytokines. We hypothesize that during an asthma attack, IFN-gamma produced by CD161(+) T cells could help to reestablish the Th1/Th2 equilibrium. These observations may contribute to the understanding of the immune mechanisms involved in asthma attacks.