Immunostimulation by bacterial components: II. Efficacy studies and meta-analysis of the bacterial extract OM-89

The clinical implications of bacterial pathogenesis and mucosal immunity in chronic urinary tract infection

Urinary tract infections (UTIs) exert a significant health and economic cost globally. Approximately one in four people with a previous history of UTI continue to develop recurrent or chronic infections. Research on UTI has primarily concentrated on pathogen behavior, with the focus gradually shifting to encompass the host immune response. However, these are centered on mouse models of Escherichia coli infection, which may not fully recapitulate the infective etiology and immune responses seen in humans. The emerging field of the urobiome also inadvertently confounds the discrimination of true UTI-causing pathogens from commensals. This review aims to present a novel perspective on chronic UTI by linking microbiology with immunology, which is commonly divergent in this field of research. It also describes the challenges in understanding chronic UTI pathogenesis and the human bladder immune response, largely conjectured from murine studies. Lastly, it outlines the shortcomings of current diagnostic methods in identifying individuals with chronic UTI and consequently treating them, potentially aggravating their disease due to mismanagement of prior episodes. This discourse highlights the need to consider these knowledge gaps and encourages more relevant studies of UTIs in humans.

A Retrospective Study of Immunotherapy Treatment with Uro-Vaxom (OM-89®) for Prophylaxis of Recurrent Urinary Tract Infections

OBJECTIVES

To present our experience with the long-term preventive effect of immunotherapy with Uro-Vaxom® on recurrent urinary tract infections (UTI) in adult patients.

MATERIALS AND METHODS

Retrospective analysis of 79 patients with recurrent UTI treated with Uro-Vaxom. Recurrent UTIs were defined as ≥ 2 infections in 6 months or ≥ 3 in 12 months. Patients received a 6 mg Uro-Vaxom capsule daily for 90 days followed by discontinuation for 3 months and then administration for the first 10 days of subsequent months 7, 8 and 9 as a 'booster' regime. The primary outcome measure was the number of UTIs encountered in the 12 months pre-treatment compared to 12 months post-treatment.

RESULTS

There was a significant decrease in the mean number of UTIs in the year following initiation of Uro-Vaxom® compared to the year preceding administration 3.14 versus 1.53 (p < 0.05) respectively.

CONCLUSION

Uro-Vaxom represents a safe and effective treatment option for prophylaxis of recurrent UTIs. In the UK, Uro-Vaxom is currently unlicensed. This study adds to a growing body of evidence in favor of non-antibiotic immune-prophylaxis for recurrent UTI.

Bacterial Lysates as Immunotherapies for Respiratory Infections: Methods of Preparation

Bacterial lysates, prepared from the microorganisms most frequently involved in human Respiratory Tract Infections (RTIs) have been in the market for several decades, and at present, several different brands are available in many countries worldwide. They all claimed to exert local and systemic immunomodulatory effects but different clinical trials show disparate results between them. The lack of consistency of predicted therapeutic effects has undermined their clinical use and hampered licensing in several countries. One explanation for such lack of consistency in the results is that their methods of preparation are also very different. Here, we review the available literature describing methods of preparation of bacterial lysates, including patent disclosure documents. We found a great variety of methodologies of preparation and a lack of standardized procedures among them. The main conclusion of our study is that there is a clear need for standardized protocols of production to obtain comparable results in clinical trials worldwide.

Effect and Analysis of Bacterial Lysates for the Treatment of Recurrent Urinary Tract Infections in Adults

Urinary tract infection (UTI) is a relevant public health problem, economically and socially affecting the lives of patients. The increase of antimicrobial bacterial resistance significantly hinders the treatment of UTIs, raising the need to search for alternative therapies. Bacterial lysates (BL) obtained from Escherichia coli and other pathogens have been used to treat different infectious diseases with promising results. This work aims to evaluate the effect and composition of an autologous BL for the treatment and control of recurrent UTIs in adults. The results show remission in 70% of the patients within the first three months after the administration of BL, while the infection is maintained under control for 6-12 months. The analysis by liquid chromatography-mass spectrometry (LC-MS) of the BL fractions recognized by the sera of patients shows the presence of cytosolic proteins, fimbriae, OMPs, and LPS. Our study demonstrates that the autologous BL contributed to the treatment and control of recurrent UTIs in adults, and its composition shows that different surface components of E. coli are potential immunogens that could be used to create a polyvalent protective vaccine.

Effects of oral immunomodulation therapy on urinary tract infections in individuals with chronic spinal cord injury-A retrospective cohort study

AIMS

To investigate the effect of an oral immunomodulation therapy with E. coli fractions on the frequency of urinary tract infections (UTIs) in patients with spinal cord injury (SCI) in a retrospective cohort study with a follow-up of 12 months.

METHODS

The patient database of a tertiary urologic referral center was screened for patients with chronic (>12 months) SCI who were taking a lyophilized lysate of 18 E. coli strains from 2008 to 2016. Patient characteristics, annual number of patient-reported UTIs and urine culture results were collected. The change in the number of UTIs, categorized as no UTIs, sporadic UTIs (1-2/year) and recurrent UTIs (≥3/year), from before to during immunomodulation therapy was investigated. Furthermore, the effect of different possible confounders (eg, age, duration of SCI, use of catheters, and concurrent antibiotic treatment) was investigated.

RESULTS

The data of 136 individuals with a mean age of 49 ± 14 years and a median time since SCI of 18 (15-22) years were analyzed. The proportion of patients with recurrent UTIs decreased significantly (P < 0.0001) from 93.4% (87.8-96.9%) to 59.6% (50.8-67.9%) during immunomodulation therapy, whereas the proportion of patients without UTIs increased significantly (P < 0.0001) from 2.2% (0.5-6.3%) to 20.6% (14.1-28.4%). The investigated confounders had no significant (P ≥ 0.15) effect on the outcome.

CONCLUSIONS

Oral immunomodulation therapy with E. coli fractions resulted in a significant and clinically relevant decrease in the frequency of UTIs in patients with SCI and thus, seems to be a promising option for the prevention of UTIs.

Preventing urinary tract infections after menopause without antibiotics

Urinary tract infections (UTIs) are the most common bacterial infections in women, and increase in incidence after the menopause. It is important to uncover underlying abnormalities or modifiable risk factors. Several risk factors for recurrent UTIs have been identified, including the frequency of sexual intercourse, spermicide use and abnormal pelvic anatomy. In postmenopausal women UTIs often accompany the symptoms and signs of the genitourinary syndrome of menopause (GSM). Antimicrobial prophylaxis has been demonstrated to be effective in reducing the risk of recurrent UTIs in women, but this may lead to drug resistance of both the causative microorganisms and the indigenous flora. The increasing prevalence of Escherichia coli (the most prevalent uropathogen) that is resistant to antimicrobial agents has stimulated interest in novel non-antibiotic methods for the prevention of UTIs. Evidence shows that topical estrogens normalize vaginal flora and greatly reduce the risk of UTIs. The use of intravaginal estrogens may be reasonable in postmenopausal women not taking oral estrogens. A number of other strategies have been used to prevent recurrent UTIs: probiotics, cranberry juice and d-mannose have been studied. Oral immunostimulants, vaginal vaccines and bladder instillations with hyaluronic acid and chondroitin sulfate are newer strategies proposed to improve urinary symptoms and quality of life. This review provides an overview of UTIs' prophylaxis without antibiotics, focusing on a practical clinical approach to women with UTIs.

Drug and Vaccine Development for the Treatment and Prevention of Urinary Tract Infections

Urinary tract infections (UTI) are among the most common bacterial infections in humans, affecting millions of people every year. UTI cause significant morbidity in women throughout their lifespan, in infant boys, in older men, in individuals with underlying urinary tract abnormalities, and in those that require long-term urethral catheterization, such as patients with spinal cord injuries or incapacitated individuals living in nursing homes. Serious sequelae include frequent recurrences, pyelonephritis with sepsis, renal damage in young children, pre-term birth, and complications of frequent antimicrobial use including high-level antibiotic resistance and Clostridium difficile colitis. Uropathogenic E. coli (UPEC) cause the vast majority of UTI, but less common pathogens such as Enterococcus faecalis and other enterococci frequently take advantage of an abnormal or catheterized urinary tract to cause opportunistic infections. While antibiotic therapy has historically been very successful in controlling UTI, the high rate of recurrence remains a major problem, and many individuals suffer from chronically recurring UTI, requiring long-term prophylactic antibiotic regimens to prevent recurrent UTI. Furthermore, the global emergence of multi-drug resistant UPEC in the past ten years spotlights the need for alternative therapeutic and preventative strategies to combat UTI, including anti-infective drug therapies and vaccines. In this chapter, we review recent advances in the field of UTI pathogenesis, with an emphasis on the identification of promising drug and vaccine targets. We then discuss the development of new UTI drugs and vaccines, highlighting the challenges these approaches face and the need for a greater understanding of urinary tract mucosal immunity.

Immunogenicity and safety of a tetravalent E. coli O-antigen bioconjugate vaccine in animal models

BACKGROUND

Extra-intestinal pathogenic Escherichia coli (ExPEC) are major human pathogens; however, no protective vaccine is currently available. We assessed in animal models the immunogenicity and safety of a 4-valent E. coli conjugate vaccine (ExPEC-4V, serotypes O1, O2, O6 and O25 conjugated to Exotoxin A from Pseudomonas aeruginosa (EPA)) produced using a novel in vivo bioconjugation method.

METHODS

Three doses of ExPEC-4V (with or without aluminum hydroxide) were administered to rabbits (2μg or 20μg per O-antigen, subcutaneously), mice (0.2μg or 2μg per O-antigen, subcutaneously) and rats (0.4μg or 4μg per O-antigen, intramuscularly). Antibody persistence and boostability were evaluated in rats using O6-EPA monovalent conjugate (0.4μg O-antigen/dose, intramuscularly). Toxicity was assessed in rats (16μg total polysaccharide, intramuscularly). Serum IgG and IgM antibodies were measured by ELISA.

RESULTS

Robust antigen-specific IgG responses were observed in all animal models, with increased responses in rabbits when administered with adjuvant. O antigen-specific antibody responses persisted up to 168days post-priming. Booster immunization induced a rapid recall response. Toxicity of ExPEC-4V when administered to rats was considered to be at the no observed adverse effect level.

CONCLUSIONS

ExPEC-4V conjugate vaccine showed good immunogenicity and tolerability in animal models supporting progression to clinical evaluation.

Cellular and Humoral Systemic and Mucosal Immune Responses Stimulated by an Oral Polybacterial Immunomodulator in Patients with Chronic Urinary Tract Infections

An oral polybacterial immunomodulator Urostim (U), composed of killed cells and their lysates from E. coli expressing type 1 and P-pili, E. coli Re mutant, P. mirabilis, K. pneumoniae and E. faecalis was created for immunoprophylaxis and immunotherapy of urinary tract infections (UTIs). In experimental animal models, the stimulating effect of U on lymphocyte functional activity, macrophage phagocytosis and antibody producing cells, was established. In this study the immuno-modulating effects of U on the proliferating capacity and ultrastructural morphologic changes of lymphocytes, cytokine production and specific systemic humoral and mucosal immune responses in patients with UTIs have been evaluated. Patients enrolled in the study, received orally 50 mg U daily for a period of three months. On days 0,30 and 90 a quantitative analysis was performed on lymphoproliferative responses to polyclonal mitogens, IL-2 and the specific antigen U, the production of specific serum and saliva IgA, IgM and IgG antibodies to all components of U and the concentration of pro-inflammatory cytokines. There was significant improvement of non-specific and specific lymphoproliferative responses on days 30 and 90 after the onset of treatment with U, confirmed by electron-microscopic studies. The highest concentrations of serum proinflammatory cytokines TNF-α, IL-1β, and IL-6 were registered at baseline followed by a decrease until the end of the observation period. This finding correlates with the gradual decrease of immune activation as measured by the spontaneous lymphocyte proliferation. Data from the production of specific antibacterial antibodies in serum and saliva show two types of reactions. The first type was registered in patients with low pre-treatment levels in whom the concentration of specific antibodies increased on days 30 and 90. The second type of reaction was observed in patients with high pre-treatment levels, which dropped on day 30 and were usually followed by an increase at the end of the study. These results provide evidence for the immuno-modulating effect of U. Our data show that the oral administration of the polybacterial immunomodulator Urostim stimulates adequate cellular and humoral systemic and mucosal immune responses in patients with chronic UTIs.

Oral vaccine (OM-89) in the recurrent urinary tract infection prophylaxis: a realistic systematic review with meta-analysis

OBJECTIVE

To evaluate the efficacy of Escherichia Coli extract (OM-89) in the prophylaxis of recurrent uncomplicated urinary tract infection (UTI) through a contemporary systematic review and meta-analysis.

METHODS

Inclusion criteria were double-blind randomized trials using orally administrated OM-89, 6mg daily, during three months with a minimum of three months of monitoring. Outcomes were the frequency of bacteriuria in 3 and 6 months, dysuria in 6 months and UTI in 6 months.

DATABASES

PubMed, MEDLINE, Cochrane Collaboration and their key references. After analysis by three independent reviewers, 15 double-blind randomized trials were identified, 10 papers excluded due to methods flaws and 5 used for data analysis due to double blinding and reporting drop-outs.

RESULTS

Among 5 selected studies the date of publication ranged from 1985 to 2005, totalizing 396 patients in the OM-89 group and 392 in the control group. Overall, there were 61 dropouts in the control group and 76 in the OM-89 group. As a major limitation there was no appropriate description of their methodologies and none of the studies described conflict of interest or commitment to the pharmaceutical industry. All studies were multi-centric, except for two, which showed no clarity on allocation concealment. All studies show benefit in favor of vaccine.

CONCLUSIONS

Current literature on prospective randomized controlled trials evaluating the use of oral OM-89 vaccine in the recurrent UTI prophylaxis is of low quality, limited to the first six months only and with variable definition of bacteriuria and UTI. Although all studies show benefit in favor of vaccine, no robust trial was identified, resulting in a high heterogeneity in the data analyzed. Also, publication bias could not be excluded and future higher quality studies are warranted adding intermediate (>12 months) and long-term follow-up.

Enhanced Mucosal Antibody Production and Protection against Respiratory Infections Following an Orally Administered Bacterial Extract

Secondary bacterial infections following influenza infection are a pressing problem facing respiratory medicine. Although antibiotic treatment has been highly successful over recent decades, fatalities due to secondary bacterial infections remain one of the leading causes of death associated with influenza. We have assessed whether administration of a bacterial extract alone is sufficient to potentiate immune responses and protect against primary infection with influenza, and secondary infections with either Streptococcus pneumoniae or Klebsiella pneumoniae in mice. We show that oral administration with the bacterial extract, OM-85, leads to a maturation of dendritic cells and B-cells characterized by increases in MHC II, CD86, and CD40, and a reduction in ICOSL. Improved immune responsiveness against influenza virus reduced the threshold of susceptibility to secondary bacterial infections, and thus protected the mice. The protection was associated with enhanced polyclonal B-cell activation and release of antibodies that were effective at neutralizing the virus. Taken together, these data show that oral administration of bacterial extracts provides sufficient mucosal immune stimulation to protect mice against a respiratory tract viral infection and associated sequelae.

Extraintestinal isolates ofEscherichia coli: identification and prospects for vaccine development

Extraintestinal pathogenic Escherichia coli (ExPEC) cause a wide variety of infections that are responsible for significant morbidity, mortality and costs to our healthcare system. Thereby, the development of an efficacious ExPEC vaccine will minimize disease and may be cost-effective in selected patient groups. Surface polysaccharides, such as capsule, have been traditional targets for vaccine development. Considering that significant antigenic heterogeneity exists among surface polysaccharides present in various ExPEC strains, their use as vaccine candidates will be challenging. Therefore, alternative vaccine candidates/approaches are being identified and evaluated and are discussed in this review. The authors envision that an efficacious ExPEC vaccine will consist of either a polyvalent subunit vaccine or a genetically engineered killed whole-cell vaccine.

Proteomics characterization of outer membrane vesicles from the extraintestinal pathogenic Escherichia coli DeltatolR IHE3034 mutant

Extraintestinal pathogenic Escherichia coli are the cause of a diverse spectrum of invasive infections in humans and animals, leading to urinary tract infections, meningitis, or septicemia. In this study, we focused our attention on the identification of the outer membrane proteins of the pathogen in consideration of their important biological role and of their use as potential targets for prophylactic and therapeutic interventions. To this aim, we generated a DeltatolR mutant of the pathogenic IHE3034 strain that spontaneously released a large quantity of outer membrane vesicles in the culture supernatant. The vesicles were analyzed by two-dimensional electrophoresis coupled to mass spectrometry. The analysis led to the identification of 100 proteins, most of which are localized to the outer membrane and periplasmic compartments. Interestingly based on the genome sequences available in the current public database, seven of the identified proteins appear to be specific for pathogenic E. coli and enteric bacteria and therefore are potential targets for vaccine and drug development. Finally we demonstrated that the cytolethal distending toxin, a toxin exclusively produced by pathogenic bacteria, is released in association with the vesicles, supporting the recently proposed role of bacterial vesicles in toxin delivery to host cells. Overall, our data demonstrated that outer membrane vesicles represent an ideal tool to study Gram-negative periplasm and outer membrane compartments and to shed light on new mechanisms of bacterial pathogenesis.

Intranasal immunization with a colloid-formulated bacterial extract induces an acute inflammatory response in the lungs and elicits specific immune responses

Nonspecific stimulation of lung defenses by repeated oral administration of immunomodulators, such as bacterial extracts, has shown potential for the prevention of respiratory tract infections. Here, we show that intranasal (i.n.) immunization with a bacterial extract formulated as a colloid induces an acute inflammatory response in the lungs characterized by increased production of CCL and CXCL chemokines and a major influx of dendritic cells (DCs) and neutrophils, with a higher proportion of DCs showing an activated phenotype (high CD80/CD86 expression). Cytokine levels measured in bronchoalveolar-lavage samples showed a small increase in the production of tumor necrosis factor alpha and similar levels of the other cytokines measured (interleukin 10 [IL-10], IL-12, and gamma interferon [IFN-gamma]) in immunized mice compared with control mice. However, the recall response of primed animals after antigenic challenge induced increased expression of IL-12 and IFN-gamma mRNAs in lung homogenates. Overall, all these effects were not due to the lipopolysaccharide content in the bacterial extract. Furthermore, we found that three i.n. doses administered 2 to 3 weeks apart were enough to elicit long-lasting specific serum immunoglobulin G (IgG) and secretory IgA antibody responses. Assessment of IgG subclasses showed a balanced pattern of IgG1-IgG2a responses. The serum total IgE concentrations were also elevated in immunized mice 2 weeks after the third dose, but they significantly decreased soon afterwards. Our results suggest that simple formulations of bacterial extracts administered i.n. are highly immunogenic, eliciting local and systemic immune responses, and may serve as the basis for cost-effective immunotherapies for the prevention and treatment of respiratory infections.

Vaccine Development for the Prevention of Urinary Tract Infections

The effectiveness of antibiotic prophylaxis for recurrent urinary tract infections is being compromised as increasing numbers of uropathogens develop resistance to conventional antibiotics. Because one alternative to antibiotic therapy is immunization of susceptible patients to increase innate resistance, several different vaccines are currently being developed. Four of the vaccines contain a mixture of whole bacteria or an antigenic extract and are administered as a vaginal suppository or oral tablet. A parenteral route is being used in clinical trials of the Escherichia coli type 1 fimbrial adhesin and its chaperone protein. The safety of both the mucosal and parenteral vaccines has been demonstrated in phase 1 clinical trials. Phase 2 trials have shown the efficacy of a vaginal mucosal vaccine containing whole bacteria and an oral vaccine prepared from bacterial lysates. Further clinical trials will allow comparisons of the various vaccines and evaluation of their effectiveness relative to prophylactic antibiotic therapy.