Bacillus Calmette-Guérin vaccination and infant mortality

When the bacillus Calmette-Guérin (BCG) vaccine was introduced in the 1920s, it was suggested that BCG occasionally had nonspecific beneficial effects on mortality beyond the specific protection against tuberculosis. Considering that BCG has since then become the most used vaccine in the world, surprisingly few studies have been undertaken into the effect of BCG on general mortality and morbidity. Recent studies suggest that BCG has beneficial nontargeted effects on general infant morbidity and mortality in low-income countries, often with the most pronounced effect among girls. These observational findings are supported by early trials in which children were randomized or alternated to BCG vaccination. Furthermore, a BCG scar and a positive tuberculin reaction are related to better survival among BCG-vaccinated children in low-income countries, especially for girls. The findings are not explained by frailty bias, in other words, that healthy children are more likely to receive BCG vaccination. A nonspecific, gender-differential effect of BCG on general infant mortality may have large implications for tuberculosis vaccine research and routine vaccination policy.     

Field Evaluation of the Efficacy of Mycobacterium bovis Bacillus Calmette-Guérin against Bovine Tuberculosis in Neonatal Calves in Ethiopia

In developing countries, the conventional test and slaughter strategy for the control of bovine tuberculosis is prohibitively expensive, and alternative control methods such as vaccination are urgently required. In this study, the efficacy of Mycobacterium bovis bacillus Calmette-Guérin (BCG) for protection against bovine tuberculosis (bTB) was evaluated in Holstein calves under field conditions in Ethiopia. Thirteen neonatally vaccinated and 14 control calves were exposed for 10 to 23 months to skin test reactor cows. Gamma interferon (IFN-γ) testing, comparative intradermal tuberculin testing, postmortem examination, and bacteriological culture were used for the evaluation of BCG efficacy. The overall mean pathology score was significantly (P < 0.05) higher in control calves than in vaccinated calves. Culture positivity for Mycobacterium bovis was higher in the control calves than in the vaccinated calves, and significantly more BCG-vaccinated animals would have passed a standard meat inspection (P = 0.021). Overall, the protective efficacy of BCG was between 56% and 68%, depending on the parameters selected. Moreover, by measuring gamma interferon responses to the antigens ESAT-6 and CFP-10, which are present in M. bovis but absent from BCG, throughout the experiment, we were able to distinguish between vaccinated animals that were protected against bTB and those animals that were not protected. In conclusion, the present trial demonstrated an encouraging protective effect of BCG against bTB in a natural transmission setting in Ethiopia.Bovine tuberculosis (bTB), caused mainly by Mycobacterium bovis, is characterized by the formation of granulomatous lesions primarily in the lymph nodes (LNs) and lungs. More than 50 million cattle are infected with M. bovis, resulting in economic losses of approximately $3 billion annually worldwide (19), and in developing countries, M. bovis infection is thought to account for 5 to 15% of human TB (2). Conventionally, the control of bTB is based on a test and slaughter strategy, which has reduced the incidence and prevalence of the disease in developed countries, except in those with wildlife reservoirs such as the United Kingdom and New Zealand. However, this method is too costly to be applicable to most of the developing world. Vaccination of cattle represents an alternative intervention strategy to reduce the impact of bTB on livestock productivity and human health in developing countries. The only currently available vaccine against tuberculosis is the human vaccine M. bovis bacillus Calmette-Guérin (BCG). BCG has been used in cattle in a large number of experiments and trials with variable efficacies (reviewed by Buddle et al. [8]). A series of field trials in East Germany and Malawi found no evidence of protection (3, 4, 11). In contrast, field trials in Malawi and Madagascar reported protective efficacies of 25% and 45%, respectively (9, 23), and other workers have reported 50% protection in field trials in Malawi and the United Kingdom, as well as New Zealand (10, 25). Higher levels of protection have been reported in the United Kingdom by Vordermeier et al. (20). Experimental infection studies over the last 15 years using intratracheal or aerosol challenge routes have optimized the use of BCG in cattle and reaffirmed the ability of BCG to protect cattle against bTB (5, 6, 24). However, few recent studies have evaluated the ability of BCG to protect cattle in a more natural cattle-to-cattle transmission setting using naturally infected donor cattle as the source of infection.In this study, we assessed the efficacy of neonatal BCG vaccination in a natural transmission setting by introducing BCG-vaccinated and control calves into a herd composed of tuberculin skin test reactor animals in a farm in central Ethiopia. The farm was managed under routine Ethiopian intensive husbandry conditions, and protective efficacy was determined after 10 to 23 months in contact with infected animals by postmortem examination and M. bovis culture. We also evaluated whether prototype reagents for the differential diagnosis of infected and vaccinated animals (DIVA reagents) were able to distinguish vaccinated and protected animals from those that were vaccinated but not protected.     

Role of bacillus Calmette-Guérin as an immunomodulator for the prevention and treatment of allergy and asthma

PURPOSE OF REVIEW: As an essential part of the hygiene hypothesis, the association between exposure to mycobacterial components and the prevention, development and severity of atopic diseases has not been fully understood. The current status on the causal-effect link of this relationship and the potential use of mycobacterial adjuvants as a preventive or disease-modifying modality in allergic diseases is reviewed in this article. RECENT FINDINGS: Data obtained from human and animal models indicate a discrepancy regarding the preventive and therapeutic effect of bacillus Calmette-Guérin in atopic diseases. Among the issues that require clarification include whether the distinction in T helper type 1/2 cells described in mice can be fully extrapolated to humans. Other factors involved could be caused by genetic variation, optimal timing, dose, route of delivery as well as environmental factors, which affect the degree of natural exposure to pathogenic or saprophytic mycobacteria. SUMMARY: Most of the evidence available to date suggests a need for an improved mycobacterial vaccine administered early in life, by means of alternative routes, preferentially mucosal. As switching away from the T helper type 2 immune response by inducing T helper type 1 is unable to explain the underlying mechanisms of action of mycobacterial antigens, it may be worthwhile to investigate whether T regulatory cells are induced in response to different mycobacterial adjuvants.     

Co-immunization of plasmid DNA encoding IL-12 and IL-18 with Bacillus Calmette-Guérin vaccine against progressive tuberculosis

Purpose

Bacillus Calmette-Guérin (BCG) vaccine has widely been used to immunize against tuberculosis, but its protective efficacy is variable in adult pulmonary tuberculosis, while it is not efficiently protective against progressive infection of virulent Mycobacterium tuberculosis strains. In this study, the protective effects of plasmid DNA vaccine constructs encoding IL-12 or IL-18 with the BCG vaccine were evaluated against progressive infection of M. tuberculosis, using mouse aerosol challenge model.

Materials and Methods

Plasmid DNA vaccine constructs encoding IL-12 or IL-18 were constructed and mice were immunized with the BCG vaccine or with IL-12 DNA or IL-18 DNA vaccine constructs together with the BCG vaccine.

Results

The BCG vaccine induced high level of interferon gamma (IFN-γ) but co-immunization of IL-12 or IL-18 DNA vaccine constructs with the BCG vaccine induced significantly higher level of IFN-γ than a single BCG vaccine. The BCG vaccine was highly protective at early stage of M. tuberculosis infection, but its protective efficacy was reduced at later stage of infection. The co-immunization of IL-12 DNA vaccine constructs with the BCG vaccine was slightly more protective at early stage of infection and was significantly more protective at later stage infection than a single BCG vaccine.

Conclusion

Co-immunization of IL-12 DNA vaccine with the BCG vaccine induced more protective immunity and was more effective for protection against progressive infection of M. tuberculosis.     

Neonatal vaccination with Bacillus Calmette-Guérin elicits long-term protection in mouse-allergic responses

Background:  Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccination has been shown to inhibit allergic airway inflammation in animal models, associated with the regulation of allergen-specific T-cell immunity. However, little is known about whether neonatal BCG treatment could inhibit allergic inflammation by regulating allergen-specific T-cell response in aged mice. This study was aimed to investigate the impact of neonatal BCG treatment on allergic asthma and possible mechanism(s) underlying the action of BCG in different ages of mice.
Methods:  C57BL/6 neonates were vaccinated with BCG on days 1, 7 and 14, sensitized with ovalbumin (OVA) at 5 and 7 weeks of age, and then challenged with allergen at 9 or 45 weeks of age for early- or late-challenged asthma. Their airway inflammation and allergen-specific T-cell responses were characterized.
Results:  Following early-challenge, BCG vaccination inhibited airway hyper-responsiveness (AHR), infiltration of eosinophils and mucous overproduction ( P  <   0.05), and shifted OVA-specific predominant Th2- to Th1-type cytokine responses in both the bronchoalveolar lavage fluid and the splenocyte supernatants ( P  <   0.05). In late-challenged mice, neonatal BCG treatment attenuated AHR and eosinophilia ( P  <   0.05), but failed to modulate allergen-specific cytokine responses.
Conclusions:  Our data suggest that neonatal BCG vaccination has a long-term effect on inhibiting AHR and eosinophilia, which is associated with the modulation of Th1/Th2 cytokine production in early-, but not in late-challenged mice. Thus, different mechanisms may mediate the long-term protective effect of BCG neonatal vaccination differently in younger adult and aged mice.     

Functional characterization of human natural killer cells responding to Mycobacterium bovis bacille Calmette-Guérin

The kinetics of activation and induction of several effector functions of human natural killer (NK) cells in response to Mycobacterium bovis bacille Calmette-Guérin (BCG) were investigated. Owing to the central role of monocytes/macrophages (MM) in the initiation and maintenance of the immune response to pathogens, two different experimental culture conditions were analysed. In the first, monocyte-depleted nylon wool non-adherent (NW) cells from healthy donors were stimulated with autologous MM preinfected with BCG (intracellular BCG). In the second, the NW cells were directly incubated with BCG, which was therefore extracellular. In the presence of MM, CD4+ T lymphocytes were the cell subset mainly expressing the activation marker, CD25, and proliferating with a peak after 7 days of culture. In contrast, in response to extracellular BCG, the peak of the proliferative response was observed after 6 days of stimulation, and CD56+ CD3- cells (NK cells) were the cell subset preferentially involved. Such proliferation of NK cells did not require a prior sensitization to mycobacterial antigens, and appeared to be dependent upon contact between cell populations and bacteria. Following stimulation with extracellular BCG, the majority of interferon-gamma (IFN-gamma)-producing cells were NK cells, with a peak IFN-gamma production at 24-30 hr. Interleukin (IL)-2 and IL-4 were not detectable in NK cells or in CD3+ T lymphocytes at any time tested. IL-12 was not detectable in the culture supernatant of NW cells stimulated with extracellular BCG. Compared to the non-stimulated NW cells, the NW cells incubated for 16-20 hr with BCG induced the highest levels of expression of apoptotic/death marker on the NK-sensitive K562 cell line. BCG also induced expression of the activation marker, CD25, and proliferation, IFN-gamma production and cytotoxic activity, on negatively selected CD56+ CD3- cells. Altogether, the results of this study demonstrate that extracellular mycobacteria activate several NK-cell functions and suggest a possible alternative mechanism of NK-cell activation as the first line of defence against mycobacterial infections.     

Characterization of the culture filtrate-specific cytotoxic T lymphocyte response induced by Bacillus Calmette-Guérin vaccination in H-2b mice

Although CD8+ T cells are supposed to play an important role in protective immunity to mycobacteria, cytotoxic T lymphocyte (CTL) responses in this infection remain poorly characterized. We previously demonstrated that bacillus Calmette-Guérin (BCG) immunization of H-2b mice induced CTL able to recognize and kill macrophages incubated with proteins from mycobacterial culture supernatant [culture filtrate (CF) antigens]. In the present study, we have further characterized the lytic activity of these CTL and the processing pathway used for the presentation of CF proteins. We show that they use the degranulation pathway (secretion of perforins and granzymes) as the main lytic mechanism of cytotoxicity and also secrete IFN-gamma upon incubation with CF-pulsed macrophages. The in vitro presentation of CF proteins to CTL required a processing step inhibited in the cold but insensitive to Brefeldin A. Transporter-associated protein (TAP)-2-deficient RMA-S cells were efficiently recognized and killed by CF-specific CTL, demonstrating the lack of TAP requirement for this presentation. However, recognition of target cells by CTL was abolished when carried out in the presence of chloroquine. These results indicate that a non-classical MHC class I-processing pathway allows the recognition of a CF protein by CTL in BCG-vaccinated H-2b mice.     

Bacillus Calmette-Guérin vaccine to reduce healthcare worker absenteeism in COVID-19 pandemic,a randomized controlled trial

ObjectivesThe COVID-19 pandemic increases healthcare worker (HCW) absenteeism. The bacillus Calmette-Guérin (BCG) vaccine may provide non-specific protection against respiratory infections through enhancement of trained immunity. We investigated the impact of BCG vaccination on HCW absenteeism during the COVID-19 pandemic.MethodsHCWs exposed to COVID-19 patients in nine Dutch hospitals were randomized to BCG vaccine or placebo in a 1:1 ratio, and followed for one year using a mobile phone application. The primary endpoint was the self-reported number of days of unplanned absenteeism for any reason. Secondary endpoints included documented COVID-19, acute respiratory symptoms or fever. This was an investigator-funded study, registered at ClinicalTrials.gov (NCT03987919).ResultsIn March/April 2020, 1511 HCWs were enrolled. The median duration of follow-up was 357 person-days (interquartile range [IQR], 351 to 361). Unplanned absenteeism for any reason was observed in 2.8% of planned working days in the BCG group and 2.7% in the placebo group (adjusted relative risk 0.94; 95% credible interval, 0.78–1.15). Cumulative incidences of documented COVID-19 were 14.2% in the BCG and 15.2% in the placebo group (adjusted hazard ratio (aHR) 0.94; 95% confidence interval (CI), 0.72–1.24). First episodes of self-reported acute respiratory symptoms or fever occurred in 490 (66.2%) and 443 (60.2%) participants, respectively (aHR: 1.13; 95% CI, 0.99–1.28). Thirty-one serious adverse events were reported (13 after BCG, 18 after placebo), none considered related to study medication.ConclusionsDuring the COVID-19 pandemic, BCG-vaccination of HCW exposed to COVID-19 patients did not reduce unplanned absenteeism nor documented COVID-19.     

Mycobacterium bovis Bacillus Calmette-Guérin suppresses inflammatory Th2 responses by inducing functional alteration of TSLP-activated dendritic cells

Allergic diseases such as atopic dermatitis and asthma develop as a consequence of dysregulated T(h)2 responses. Recently, it has been demonstrated that interaction between dendritic cells (DCs) and thymic stromal lymphopoietin (TSLP), an IL-7-like cytokine, is essential for evoking T(h)2 responses in allergy. In this study, we investigated whether Mycobacterium bovis Bacillus Calmette-Guérin (BCG), a strong T(h)1 response-inducing adjuvant, can alter the function of DCs activated by TSLP (TSLP-DCs). We demonstrated that BCG redirects TSLP-DCs away from inducing inflammatory T(h)2 cells that produce IL-4, IL-5, IL-13 and tumor necrosis factor (TNF)-alpha and toward regulatory T(h)1 cells that produce IFN-gamma and IL-10. We also demonstrated that this functional alteration of TSLP-DCs by BCG depended on both production of IL-12 from DCs and down-regulation of OX40 ligand, a member of the TNF family, on DCs. These findings suggest that BCG might be a useful adjuvant for the treatment of allergic diseases that are triggered by TSLP.     

Bacillus Calmette-Guérin Suppresses Asthmatic Responses via CD4+CD25+ Regulatory T Cells and Dendritic Cells

Purpose

Bacillus Calmette-Guérin (BCG) is known to suppress the asthmatic responses in a murine model of asthma and to induce dendritic cells (DCs) maturation. Mature DCs play a crucial role in the differentiation of regulatory T cells (Tregs), which are known to regulate allergic inflammatory responses. To investigate whether BCG regulates Tregs in a DCs-mediated manner, we analyzed in a murine model of asthma.

Methods

BALB/c mice were injected intraperitoneally with BCG or intravenously with BCG-stimulated DCs and then sensitized and challenged with ovalbumin (OVA). Mice were analysed for bronchial hyperresponsiveness (BHR), the influx of inflammatory cells in the bronchoalveolar lavage (BAL) fluid, and histopathological changes in the lung. To identify the mechanisms, IgE, IgG₁ and IgG_2a in the serum were analysed and the CD25₊ Tregs in the mice were depleted with anti-CD25 monoclonal antibody (mAb).

Results

BCG and the transfer of BCG-stimulated DCs both suppressed all aspects of the asthmatic responses, namely, BHR, the production of total IgE and OVA-specific IgE and IgGs, and pulmonary eosinophilic inflammation. Anti-CD25mAb treatment reversed these effects.

Conclusions

BCG can attenuate the allergic inflammation in a mouse model of asthma by a Tregs-related mechanism that is mediated by DCs.     

Cathepsin B is involved in the apoptosis intrinsic pathway induced by Bacillus Calmette-Guérin in transitional cancer cell lines

Bacillus Calmette-Guérin (BCG) is the most effective treatment for superficial and in situ transitional bladder cancer. Although the complete mechanisms for its effect are not fully understood yet, both immunological and direct effects on tumor cells have been proposed. It has been proposed that apoptotic tumor cells could be better inducers of immunity than necrotic ones. Thus, apoptosis of bladder cancer cells could contribute to a global response to BCG. Lysosomal hydrolase cathepsin B (CB) is involved in the apoptotic process and has a key role in breast cancer cell programmed death through the activation of a pro-apoptotic protein BID. Truncated BID participates in the mitochondrial apoptotic pathway that involves the activation of pro-caspase 9. The possibility that CB can be involved in apoptosis of TCC line has not been explored yet. Therefore, we analyzed the participation of CB in BCG-induced apoptosis of human and murine TCC lines. Apoptosis was evaluated by a morphologic assay and CB activity by a substrate-specific colorimetric method. Expression of CB, BID and pro-caspase 9 was determined by Western blotting. BCG induced apoptosis of murine (MBT2, MB49) and human (T24) TCC lines. An increase in both CB activity and protein was also observed. The apoptosis of T24 and MB49 cell lines was mediated by activation of pro-caspase 9 and BID, both proteins are involved in mitochondrial apoptosis. Apoptosis and activation of pro-caspase 9 and BID were inhibited by CA-074Me (CA), a cell permeable CB inhibitor. Thus, CB is involved in BCG-induced apoptosis of TCC lines, using at least in part the mitochondrial pathway.     

Cytologic features of disseminated bacillus Calmette-Guérin (BCG) infection

Disseminated bacillus Calmette-Guérin (BCG) infection is an unusual complication of immunization against Mycobacterium tuberculosis with the bacillus Calmette-Guérin. We report on 4 such cases in which the diagnosis was suspected at the fine-needle aspiration biopsy (FNAB) procedure. Participants were 4 males (mean age, 21.5 mo; range, 8-36 mo) in good general condition, in whom epidemiology data favoring tuberculosis and presence of pulmonary tuberculosis were lacking. Cases 1 and 2 presented with a deep-seated subcutaneous nodule located near the left mamilla and lower aspect of the left scapula, respectively, resulting from lymph node involvement by BCG. Cases 3 and 4 presented as an osteolytic lesion of the ninth right rib and right iliac bone, respectively. FNAB findings showed poorly to moderately cellular smears. Epithelioid histiocytes in a granuloma pattern with occasional multinucleated Langerhans-type giant cells, lymphocytes, and polymorphonuclear leukocytes in a finely granular background with necrotic debris were found in all cases. The presence of isolated calcified spherules interspersed among the cells was found to be a useful finding for diagnosis. When dealing with disseminated BCG infections, clinical and cytological pictures must be evaluated as a whole in order to arrive at an accurate diagnosis.     

Bacillus Calmette-Guérin vaccination at birth and in vitro cytokine responses to non-specific stimulation. A randomized clinical trial

Several studies have shown increased in vitro cytokine responses to non-related pathogens after Bacillus Calmette-Guérin (BCG) vaccination. A total of 158 infants (80 BCG administered within 7 days of birth; 78 controls) were bled 4 days post-randomization, and at age 3 and 13 months. Geometric mean concentrations of IL-1β, TNF-α, IL-6 (24 h stimulation) and IFN-γ, IL-10, IL-17, IL-22 (96 h stimulation) in response to in vitro stimulation with RPMI, LPS, PHA, Escherichia coli, Streptococcus pneumoniae, Candida albicans and BCG were compared among BCG vaccinated children and controls. BCG vaccination did not affect in vitro cytokine production, except IFN-γ and IL-22 response to BCG. Stratifying for ‘age at randomization’ we found a potentiating effect of BCG on cytokine production (TNF-α, IL-6, IL-10) in the 4 days post randomization stimulations, among children who were vaccinated at age 2–7 days versus age 0–1 days. BCG vaccination did not potentiate cytokine production to non-BCG antigens. At 4 days post randomization, BCG was associated with higher cytokine production in the later randomized children.