BCG Protection Research Articles

IL-27 alters inflammatory cytokine expression and limits protective immunity against Mycobacterium tuberculosis in a neonatal BCG vaccination model.

Efforts to control tuberculosis (TB), caused by the pathogen Mycobacterium tuberculosis (Mtb), have been hampered by the immense variability in protection from BCG vaccination. While BCG protects young children from some forms of TB disease, long-term protection against pulmonary disease is more limited, suggesting a poor memory response. New vaccines or vaccination strategies are required to have a realistic chance of eliminating TB disease. In TB endemic areas, routine immunization occurs during the neonatal period and as such, we hypothesized that inadequate protective immunity elicited by BCG vaccination could be the result of the unique early-life immune landscape. Interleukin (IL)-27 is a heterodimeric cytokine with immune suppressive activity that is elevated in the neonatal period. We investigated the impact of IL-27 on regulation of immune responses during neonatal BCG vaccination and protection against Mtb. Here, we used a novel model of neonatal vaccination and adult aerosol challenge that models the human timeline of vaccine delivery and disease transmission. Overall, we observed improved control of Mtb in mice unresponsive to IL-27 (IL-27Rα-/-) that was consistent with altered expression patterns of IFN-γ and IL-17 in the lungs. The balance of these cytokines with TNF-α expression may be key to effective bacterial clearance. Our findings suggest the importance of evaluating new vaccines and approaches to combat TB in the neonatal population most likely to receive them as part of global vaccination campaigns. They further indicate that temporal strategies to antagonize IL-27 during early life vaccination may improve protection.

Significance of PPD Test for the Relationship Between BCG Vaccine and COVID-19 in Patients on Kidney Transplant Waiting List

BackgroundThe aim of this study was to determine the relationship between purified protein derivative of tuberculin (PPD) values, an indicator of BCG protection, and COVID-19 disease in patients with end-stage renal disease (ESRD) on the kidney transplant waiting list.MethodsAge, sex, dialysis type, ERSD etiologies, and PPD values of patients on the renal transplant waiting list were recorded. SARS-CoV-2 PCR data, whether the patients were previously infected with the virus, and, if infected, the severity of the disease were noted. Data were statistically compared.ResultsPCR of 87 (47.02%) of 185 patients were studied; 107 of the patients were male and 78 were female, with a mean age of 52.8 years. The test result was positive for 28 patients. Of the patients for whom PCR was studied, 41 had a negative PPD result, while 46 had a positive PPD result. There was no correlation with SARS-CoV-2 PCR positivity in patients with a PPD ≤ 5 mm and > 5 mm. However, patients with pneumonic infiltration who required hospitalization had a significantly higher PPD value.ConclusionsThe PPD measurement, which is an indicator of BCG protection, might be a significant parameter for predicting the course of the disease in SARS-CoV-2 pneumonia.

BCG vaccination impact on mortality and recovery rates in COVID-19: A meta-analysis.

COVID-19 is a pandemic caused by SARS-CoV-2 virus which is a very worrisome public health emergency. In this study, we compared the mortality rate and recovery rate in countries with and without BCG vaccination policy. The data of mortality of COVID-19 was extracted from worldometer (https://www.worldometers.info/coronavirus/) on 26th July 2020. The data of countries where BCG vaccination is being done for all individuals is taken from BCG world atlas (http://www.bcgatlas.org/index.php), updated in 2017. BCG vaccination policy recommended countries are intervention group versus countries without BCG vaccination policies which are regarded as control group. Pooled analysis of countries with and without BCG vaccination policy revealed mortality rate of 1.31% (95%CI - 1.31% to 1.32%; I2 = 100%, p<0.01) and 3.25% (95%CI - 3.23% to 3.26%; I2 = 100%, p<0.01), respectively. The recovery rates in two country groups were found to be 72.60% (95%CI - 72.57% to 72.63%) and 55.94% (95%CI - 55.90% to 55.98%), respectively. 52 individuals need to be BCG vaccinated to prevent one death (NNT = 52). In BCG vaccination program countries, there is statistically and clinically significant less mortality (p<0.001) as compared to countries without BCG policy. Our findings corroborate the hypothesis that BCG vaccination may provide protection from COVID-19. High quality evidence from randomised controlled trials are required to establish causality between BCG vaccination and protection from severe COVID-19.

Variances in BCG protection against COVID-19 mortality: A global assessment

The BCG vaccine is known to impart nonspecific immunological benefits alongside conferring protection to tuberculosis in endemic regions. It is also known to protect against bladder cancer and other respiratory tract infections. During the coronavirus disease 2019 (COVID-19) pandemic, the BCG vaccine has gained attention due to its role in conferring protective immunity. We demonstrate the potential immunological protective mechanisms that play a role against COVID-19. We conduct a global assessment of the countries that have the highest and lowest mortality rates determined by an a priori methodology. Lastly, we discuss the potential limitations of incorporating BCG vaccines as potential strategies against COVID-19 and provide recommendations regarding their use in ongoing and future epidemics.

BCG Protection Against COVID-19: Is it Reality or Illusion?

BCG Protection Against COVID-19: Is it Reality or Illusion?

Engineering a new vaccine platform for heterologous antigen delivery in live-attenuated Mycobacterium tuberculosis

Live vaccines are attractive vehicles for antigen delivery as a strategy to immunize against heterologous pathogens. The live vaccine MTBVAC is based on rational attenuation of Mycobacterium tuberculosis with the objective of improving BCG protection against pulmonary tuberculosis. However, the development of recombinant mycobacteria as antigen-presenting microorganisms has been hindered due to their fastidious genetic manipulation. In this study, we used MTBVAC as a genetic platform to deliver diphtheria, tetanus, or pertussis toxoids, which are the immunogenic constituents of the DTP vaccine. When using nonoptimal genetic conditions, the expression of these immunogens was barely detectable. Accordingly, we pursued a rational, step-by-step optimization of the genetic components to achieve the expression and secretion of these toxoids. We explored variants of the L5 mycobacteriophage promoter to ensure balanced antigen expression and plasmid stability. Optimal signal sequences were identified by comparative proteomics of MTBVAC and its parental strain. It was determined that proteins secreted by the Twin Arginine Translocation pathway displayed higher secretion in MTBVAC, and the Ag85A secretion sequence was selected as the best candidate. Because the coding regions of diphtheria, tetanus, and pertussis toxoids significantly differ in G + C content relative to mycobacterial genes, their codon usage was optimized. We also placed a 3xFLAG epitope in frame with the C-terminus of these toxoids to facilitate protein detection. Altogether, these optimizations resulted in the secretion of DTP antigens by MTBVAC, as demonstrated by western blot and MRM-MS. Finally, we examined specific antibody responses in mice vaccinated with recombinant MTBVAC expressing DTP antigens.

SARS-CoV-2: Current Perspective on Control, Prevention, and Therapeutic Promise

Background: The novel coronavirus disease (COVID-19) outbreak has halted activities throughout the globe because of its rapid spread. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) a β-coronavirus first detected in China. SARS-CoV-2 has been implicated to be transmitted via direct contact, fomite, respiratory droplets, and possibly aerosol. The spread of the disease is complicated due to the slow onset of symptoms and asymptomatic infected patients.&#x0D; Methods: This narrative communication summarizes the recent researches sourced using sensitive search strategies to identify COVID-19 current perspectives on the control, prevention, and therapeutic promise.&#x0D; Result: Several strategies and multiple control measures have been implemented around the globe to contain COVID-19. Considering the exponential spread of the pandemic, several scientists and physicians have been racing to discover possible therapeutics and vaccines for COVID-19. There are clinical trials to investigate the vaccine designed to protect against the infection and also to substantiate the claim made for BCG protection against COVID-19. Although, there is currently no universally approved medication to treat SARS-CoV-2, there have been random reports of existing medications ameliorating the infection, and these regimens are still under clinical trial. There is also the potential therapeutic prospect of rhinothermy to fight SARS-CoV-2 judging from its success in fighting upper respiratory tract viral infection.&#x0D; Conclusion: The information provided in this communication gives a reliable intellectual grounding regarding the current perspective on COVID-19 control, progress made in the development of vaccines and therapeutic regimen, and where future research in this area should be focused.&#x0D; Key words: COVID-19; SARS-CoV-2; control; WHO; respiratory; cases; tract

BCG Vaccine Protection Against Mycobacterium tuberculosis Infection by Level of Exposure in The Gambia.

In Indonesia, BCG vaccine protection against Mycobacterium tuberculosis infection decreased with increasing exposure to the pathogen. We aimed to validate these findings in Africa. Poisson regression was used to estimate BCG protection, stratified by pathogen exposure using an exposure score, against enzyme-linked immunospot assay conversion at 3 months in 220 Gambian case contacts. Although the interaction between BCG and exposure was not significant (P = .13), BCG protection was strongest in the lowest-exposure tertile (relative risk, 0.35 [95% confidence interval, .15-.82; P = .02] vs 0.50 [.30-.83; P = .008] and 0.71 (.45-1.13; P = .1] for the middle and highest-exposure tertiles, respectively. These results are consistent with those from Indonesia.

Early Clearance of Mycobacterium tuberculosis: The INFECT Case Contact Cohort Study in Indonesia.

Early clearance of Mycobacterium tuberculosis is the eradication of infection before an adaptive immune response develops. We aimed to identify host factors associated with early clearance. Indonesian household contacts patients with smear-positive tuberculosis (TB) had an interferon-γ release assay (IGRA) at baseline and 14 weeks later. Early clearance was defined as a persistently negative IGRA. Contact characteristics, exposure, and disease phenotype were assessed for association with a positive IGRA at each time point. Of 1347 contacts of 462 TB cases, 780 (57.9%) were IGRA positive and 490 (36.3%) were IGRA negative. After 14 weeks, 116 of 445 (26.1%) initially negative contacts were IGRA converters; 317 (71.2%) remained persistently negative. BCG vaccination reduced the risk of a positive baseline IGRA (relative risk [RR], 0.89 [95% confidence interval {CI} .83-.97]; P = .01), and strongly reduced the risk of IGRA conversion (RR, 0.56 [95% CI, .40-.77]; P < .001). BCG protection decreased with increasing exposure (P = .05) and increasing age (P = .004). Risk of IGRA conversion was positively associated with hemoglobin concentration (P = .04). A quarter of household TB case contacts were early clearers. Protection against M. tuberculosis infection was strongly associated with BCG vaccination. Lower protection from BCG with increasing M. tuberculosis exposure and age can inform vaccine development.

IL-10 Dampens the Th1 and Tc Activation through Modulating DC Functions in BCG Vaccination.

BCG, the only registered vaccine against Mycobacterial Tuberculosis (TB) infection, has been questioned for its protective efficacy for decades. Although lots of efforts were made to improve the BCG antigenicity, few studies were devoted to understand the role of host factors in the variability of the BCG protection. Using the IL-10KO mice and pulmonary tuberculosis infection model, we have addressed the role of IL-10 in the BCG vaccination efficacy. The data showed that IL-10-deficient dendritic cells (DCs) could promote the immune responses through upregulation of the surface costimulatory molecule expression and play an orchestra role through activating CD4+T cell. IL-10-deficient mice had higher IFN γ, TNF α, and IL-6 production after BCG vaccination, which was consistent with the higher proportion of IFN γ+CD3+, IFN γ+CD4+, and IFN γ+CD8+ T cells in the spleen. Particularly, the BCG-vaccinated IL-10KO mice showed less inflammation after TB challenge compared to WT mice, which was supported by the promoted Th1 and Tc, as well as the downregulated Treg responses in IL-10 deficiency. In a conclusion, we demonstrated the negative relationship between Th1/Tc responses with IL-10 production. IL-10 deficiency restored the type 1 immune response through DC activation, which provided better protection against TB infection. Hence, our study offers the first experimental evidence that, contrary to the modulation of BCG, host immunity plays a critical role in the BCG protective efficacy against TB.

Cloning, Expression, and Refolding of PPE17 Protein of Mycobacterium Tuberculosis as a Promising Vaccine Candidate.

Tuberculosis as a global health problem requires special attention in the contexts of prevention and control. Subunit vaccines are promising strategies to protect burdens of tuberculosis via increasing the BCG protection. The present study aimed to design a vaccine study by means of high-throughput expression and correct refolding of recombinant protein PPE17. We aimed to clone, express, and refold PPE17 protein of Mycobacterium tuberculosis in bacterial systems as a promising vaccine candidate. The PPE17 (Rv1168c) gene was PCR amplified and inserted into pET-21b(+) vector, cloned in E. coli TOP10, and finally expressed in E. coli BL21(DE3). The expressed recombinant protein was entirely found in insoluble form (inclusion bodies). The insoluble protein was denatured in 6M guanidine-HCl and refolded by descending denaturant concentration dialysis. Moreover, the recombinant protein was purified by Ni-NTA column chromatography. The changing temperature had no effects on solubilizing protein and the maximum expression was achieved at 0.5 mM concentration of isopropyl-D-thiogalactopyranoside (IPTG) induction. Bacterial expression system is a timesaving tool and refolding by descending denaturant concentration dialysis is a rapid and reliable method.

Age-related waning of immune responses to BCG in healthy children supports the need for a booster dose of BCG in TB endemic countries

In the absence of a more effective vaccine against TB and in the interest of developing one, it is essential to understand immune responses associated with BCG protection. We comprehensively characterized T cell populations in BCG-vaccinated children over time. Blood from 78 healthy, BCG-vaccinated children representing four age groups (<1 yr, ≥1 yr <2 yr, ≥2 yr <5 yr, ≥5 yr), was stimulated in vitro for 24 hours and 6 days with live BCG to induce effector and central memory responses. Antigen-specific CD4, CD8, γδ and regulatory T cell populations were phenotyped and intracellular and secreted cytokines measured by flow cytometry and multiplex ELISA respectively. Our results demonstrated that populations of naïve T cells predominated in infants, compared to older children. However, BCG-specific effector CD4 T cell responses were equivalent and antigen-specific CD4 T cell proliferative capacity was increased in infants compared to older children. Increases in innate immune responses including γδ T cell responses and secreted pro-inflammatory cytokines were noted with increasing age. In conclusion, we identified that the capacity to expand and differentiate effector T cells in response to BCG stimulation wanes with increasing age, which may indicate waning central memory immunity. Booster vaccination could be considered to maintain the antigen-specific central memory pool and possibly enhance the duration of protection.

A New Rabbit-Skin Model to Evaluate Protective Efficacy of Tuberculosis Vaccines

Background: BCG protection is suboptimal and there is significant interest to develop new tuberculosis (TB) vaccines. However, there are significant limitations of the current vaccine evaluation systems in the mouse model. Here, we developed a BCG-challenge rabbit skin model as a new way to evaluate the protective efficacy of selected TB subunit vaccine candidates.Methods: Rabbits were immunized with subunit vaccines, including EAMM (ESAT6-Ag85B-MPT64<190−198>-Mtb8.4), MH (Mtb10.4-HspX), and LT70 (ESAT6-Ag85B-MPT64<190−198>-Mtb8.4-Rv2626c) three times subcutaneously every 3-weeks and challenged with the attenuated Mycobacterium bovis BCG intradermally 6-weeks after last immunization. The immune response induced by the vaccine candidates was measured, the histopathology induced by the BCG challenge was studied, and the number of bacilli in the liquefied caseum was determined.Results: The subunit vaccines generated high antigen-specific IgG antibodies and fastened the liquefaction and healing process, and significantly reduced the viable BCG load. The subunit vaccine LT70 and EAMM-MH reduced BCG bacterial load in comparison to proteins EAMM, MH, Rv2626c, and also BCG itself. The Koch phenomena induced by the LT70 and combination of EAMM-MH were the same as that produced by BCG itself and were more rapid than those induced by the other proteins and the saline controls.Conclusions: The subunit vaccines LT70 and the combination of EAMM-MH showed promising protective efficacy as expected in the rabbit skin model, which can serve as a visual and convenient new model for evaluating TB vaccines.

Duration of BCG protection against tuberculosis and change in effectiveness with time since vaccination in Norway: a retrospective population-based cohort study

Little is known about how long the BCG vaccine protects against tuberculosis. We assessed the long-term vaccine effectiveness (VE) in Norwegian-born individuals. In this retrospective population-based cohort study, we studied Norwegian-born individuals aged 12-50 years who were tuberculin skin test (TST) negative and eligible for BCG vaccination as part of the last round of Norway's mandatory mass tuberculosis screening and BCG vaccination programme between 1962 and 1975. We excluded individuals who had tuberculosis before or in the year of screening and those with unknown TST and BCG status. We obtained TST and BCG information and linked it to the National Tuberculosis Register, population and housing censuses, and the population register for emigrations and deaths. We followed individuals up to their first tuberculosis episode, emigration, death, or Dec 31, 2011. We used Cox regressions to estimate VE against all tuberculosis and just pulmonary tuberculosis by time since vaccination, adjusted for age, time, county-level tuberculosis rates, and demographic and socioeconomic indicators. Median follow-up was 41 years (IQR 32-49) for 83 421 BCG-unvaccinated and 44 years (41-46) for 297 905 vaccinated individuals, with 260 tuberculosis episodes. Tuberculosis rates were 3·3 per 100 000 person-years in unvaccinated and 1·3 per 100 000 person-years in vaccinated individuals. The adjusted average VE during 40 year follow-up was 49% (95% CI 26-65), although after 20 years, the VE was not significant (up to 9 years VE [excluding tuberculosis episodes in the first 2 years] 61% [95% CI 24-80]; 10-19 years 58% [27-76]; 20-29 years 38% [-32 to 71]; 30-40 years 42% [-24 to 73]). VE against pulmonary tuberculosis up to 9 years (excluding tuberculosis episodes in the first 2 years) was 67% (95% CI 27-85), 10-19 years was 63% (32-80), 20-29 years was 50% (-19 to 79), and 30-40 years was 40% (-46 to 76). Findings are consistent with long-lasting BCG protection, but waning of VE with time. The vaccine could be more cost effective than has been previously estimated Norwegian Institute of Public Health and London School of Hygiene & Tropical Medicine.

Causes of variation in BCG vaccine efficacy: Examining evidence from the BCG REVAC cluster randomized trial to explore the masking and the blocking hypotheses

BCG protection varies and in some places (nearest the equator) is low or absent. Understanding this variation can inform the efforts to develop new vaccines against tuberculosis. Two main hypotheses are used to explain this variation: under masking, new vaccines are unlikely to increase protection; under blocking new vaccines have a greater potential to be effective when BCG is not. We conducted a cluster randomized trial to explored the masking and blocking hypotheses by studying BCG vaccine efficacy of neonatal vaccination and when administered for the first or a second (revaccination) time at school age in two sites (Manaus close and Salvador further south from the equator). Seven hundred and sixty three state schools were matched on socio economic characteristics of the neighborhood and 239,934 children were randomized to vaccine (BCG vaccination at school age) or control group. Protection by first BCG vaccination at school age was high in Salvador (34%, 95% CI 7–53%, p=0.017) but low in Manaus (8%, 95% CI t0 39–40%, p=0.686). For revaccination at school age, protection was modest in Salvador (19%, 95% CI 3–33%, p=0.022) and absent in Manaus (1%, 95% CI to 27–23%, p=0.932). Vaccine efficacy for neonatal vaccination was similar in Salvador (40%, 95% CI 22–54%, p<0.001) and Manaus (36%, 95% CI 11–53%, p=0.008). Variation in BCG efficacy was marked when vaccine was given at school age but absent at birth, which points towards blocking as the dominant mechanism. New tuberculosis vaccines that overcome or by pass this blocking effect could confer protection in situations where BCG is not protective.The Department of International Development, UK (DFID) and the National Health Foundation, Brazil (FUNASA) funded the trial. It is registered at Controlled Trials (ISRCTN07601391).

Kinship and Leprosy in the Contacts of Leprosy Patients: Cohort at the Souza Araújo Outpatient Clinic, Rio de Janeiro, RJ, 1987–2010

A broad variety of factors have been associated with leprosy among contacts, including socioeconomic, epidemiological, and genetic characteristics. Data from 7,174 contacts of leprosy patients from a leprosy outpatient clinic in Rio de Janeiro, Brazil, 1987–2010, were analyzed to investigate the effects of kinship, individual, and contextual factors on leprosy. Multivariate analyses were performed using a robust estimation method. In the prevalence analysis, close kinship (sibling OR = 2.75, offspring OR = 2.00, and other relatives OR = 1.70), socioeconomic factors, and the duration of exposure to the bacillus were associated to leprosy. In the incidence analysis, significant risks were found for all categories of kinship (parents RR = 10.93, spouse, boyfriend/girlfriend, and bride/groom RR = 7.53, sibling RR = 7.03, offspring RR = 5.34, and other relatives RR = 3.71). Once the treatment of the index case was initiated, other factors lost their significance, and the index case bacteriological index and BCG (Bacillus Calmette-Guérin vaccine) protection had a greater impact. Our findings suggested that both genetic susceptibility and physical exposure play an important role in the epidemiology of leprosy, but it was not possible establishing the role of genetic factor. Analyses of other factors related to the genotype of individuals, such as genetic polymorphisms, are needed.

OP39 Protection by BCG Against Tuberculosis: Systematic Review and Meta-Regression Analysis

SettingReasons for variation in BCG protection against tuberculosis are not well understood. We therefore estimated the protection provided by BCG vaccination against tuberculosis and examined reasons for variation in different...

P176 Does BCG protect against atopic diseases only for a limited time period?

Allergic diseases such as atopic asthma are believed to have their origins in early life1 but the precise mechanisms and timings of the relevant immunoregulation continue to be a focus...

Protection against Tuberculosis in Eurasian Wild Boar Vaccinated with Heat-Inactivated Mycobacterium bovis

Tuberculosis (TB) caused by Mycobacterium bovis and closely related members of the Mycobacterium tuberculosis complex continues to affect humans and animals worldwide and its control requires vaccination of wildlife reservoir species such as Eurasian wild boar (Sus scrofa). Vaccination efforts for TB control in wildlife have been based primarily on oral live BCG formulations. However, this is the first report of the use of oral inactivated vaccines for controlling TB in wildlife. In this study, four groups of 5 wild boar each were vaccinated with inactivated M. bovis by the oral and intramuscular routes, vaccinated with oral BCG or left unvaccinated as controls. All groups were later challenged with a field strain of M. bovis. The results of the IFN-gamma response, serum antibody levels, M. bovis culture, TB lesion scores, and the expression of C3 and MUT genes were compared between these four groups. The results suggested that vaccination with heat-inactivated M. bovis or BCG protect wild boar from TB. These results also encouraged testing combinations of BCG and inactivated M. bovis to vaccinate wild boar against TB. Vaccine formulations using heat-inactivated M. bovis for TB control in wildlife would have the advantage of being environmentally safe and more stable under field conditions when compared to live BCG vaccines. The antibody response and MUT expression levels can help differentiating between vaccinated and infected wild boar and as correlates of protective response in vaccinated animals. These results suggest that vaccine studies in free-living wild boar are now possible to reveal the full potential of protecting against TB using oral M. bovis inactivated and BCG vaccines.

MPT-51/CpG DNA vaccine protects mice against Mycobacterium tuberculosis

Tuberculosis (TB) is a severe infectious disease that kills approximately two million people worldwide every year. Because BCG protection is variable and does not protects adults, there is a great need for a new vaccine against TB that does not represent a risk for immunocompromised patients and that is also capable of protecting adult individuals. MPT-51 is a protein found in the genome of mycobacteria and binds to the fibronectin of the extracellular matrix, which may have a role in host tissue attachment and virulence. In order to test the usefulness of MPT-51 as a subunit vaccine, BALB/c were vaccinated and challenged with Mycobacterium tuberculosis. The infection of BALB/c with M. tuberculosis increased the number of IFN-γ + T lymphocytes specific to MPT-51 in the spleen and lungs. Inoculation with rMPT-51/FIA and with rMPT-51/CpG DNA in non-infected BALB/c increased the amounts of IFN-γ + T lymphocytes. Inoculation with rMPT-51/FIA also induced a humoral response specific to MPT-51. CFU counts of lung tissues done 60 days after infection showed a reduction of about 2 log in the bacteria load in the group of animals inoculated with rMPT-51/CpG DNA. These results make MPT-51 a valuable component to be further evaluated in the development of other subunit vaccines.