Comparison of the safety and immunogenicity of the lyophilized Mérieux seed and the World Health Organization working reference BCG vaccines in school-aged children in Senegal

Neonatal Bacille Calmette-Guérin vaccination and tuberculin skin test reactions at 2- and 6-months: Effects on mortality up to 1 year of age

BACKGROUND

In randomized trials, Bacille Calmette-Guérin (BCG) vaccine has been associated with reduced all-cause mortality. BCG-induced Tuberculin Skin Test (TST) reactions have also been associated with reduced all-cause mortality. We aimed to assess the association between TST responses and subsequent mortality in three birth cohorts and conducted a meta-analysis of existing studies.

METHODS

Observational study within three Guinea-Bissau BCG trial birth cohorts (conducted 2002-04, 2009-2013 and 2014-18) that encompassed children who were BCG-vaccinated within 28 days with TSTs performed at 2- (n = 1389) and 6-months (n = 2635) of age. We evaluated TST reaction determinants by binomial regression and assessed the association between TSTs > 1 mm (reactors) vs. ≤ 1 mm (non-reactors) and subsequent mortality risk up to age 12 months in Cox-models providing Mortality Rate Ratios (MRRs). We searched PubMed for studies to calculate meta-estimates of the association between TST reactivity by age 2- and 6-months and all-cause mortality.

RESULTS

Large post-vaccination wheal size was associated with 6-month TST positivity and so was receiving BCG-Denmark or BCG-Japan, compared with BCG-Russia. By age 2 months, 22% (302/1389) of infants were TST reactors with a 2-12-month mortality risk of 1.7% (5/302) vs. 3.3% (36/1087) for non-reactors, the corresponding reactor/non-reactor MRR = 0.49 (0.19-1.26). By age 6 months, 44% (1149/2635) of infants were reactors and the 6-12-month mortality risk was 0.4% (4/1149) vs. 0.6% (9/1486) for non-reactors, the MRR = 0.87 (0.27-2.86). The literature search provided 3 studies. The meta-analysis revealed a uniform pattern of reduced mortality associated with TST reactivity, a TST response by 2 months being associated with an MRR of 0.59 (0.39-0.90); for 6-month TST responses the MRR was 0.65 (0.43-1.00).

CONCLUSION

Among BCG-vaccinated infants, TST reactions were associated with markedly reduced mortality. Improved vaccination technique and using certain BCG strains could lead to a higher TST reaction prevalence, which would enhance BCG's beneficial non-specific effects.

Early Vaccination With Bacille Calmette-Guérin-Denmark or BCG-Japan Versus BCG-Russia to Healthy Newborns in Guinea-Bissau: A Randomized Controlled Trial

Background

Bacille Calmette-Guérin (BCG) vaccination remains a cornerstone against tuberculosis. Randomized controlled trials (RCTs) have demonstrated that BCG-Denmark lowers all-cause mortality, but a recent RCT found no effect of BCG-Russia. Observational studies indicate that the genetically divergent BCG strains have different effects.

Methods

This was a parallel-group, open-label RCT conducted at the National Hospital in Guinea-Bissau. Healthy neonates were randomized 1:1 to BCG-Denmark (2851 randomized, 2840 analyzed) vs BCG-Russia (2845 randomized, 2837 analyzed). We hypothesized that BCG-Denmark would reduce morbidity (primary outcome) and mortality while inducing more BCG reactions and purified protein derivative (PPD) responses (secondary outcomes). Halfway through the trial, production of BCG-Denmark was halted, and the trial continued comparing BCG-Japan (3191 neonates randomized, 3184 analyzed) with BCG-Russia (3170 randomized, 3160 analyzed). Mortality and morbidity data were collected by telephone, at home visits, and at the National Hospital and assessed in Cox models providing 6-week mortality rate ratios (MRRs) and hospitalization incidence rate ratios (IRRs).

Results

By age 6 weeks, there were 140 and 130 admissions among neonates vaccinated with BCG-Denmark and BCG-Russia, respectively (IRR, 1.08 [95% confidence interval {CI}, .84–1.37]). For BCG-Japan, there were 185 admissions vs 161 admissions for BCG-Russia (IRR, 1.15 [95% CI, .93–1.43]). The 6-week mortality did not differ: BCG-Denmark/BCG-Russia (MRR, 1.15 [95% CI, .74–1.80]); BCG-Japan/BCG-Russia (MRR, 0.71 [95% CI, .43–1.19]). BCG-Denmark and BCG-Japan induced more BCG scars and PPD reactions than BCG-Russia.

Conclusions

BCG strains did not affect morbidity. BCG-Denmark and BCG-Japan were more immunogenic than BCG-Russia by the measures traditionally viewed as surrogates for successful immunization. The implications of strain differences for tuberculosis protection and overall health warrant further study.

Clinical Trials Registration

NCT02447536.

The influence of BCG vaccine strain on mycobacteria-specific and non-specific immune responses in a prospective cohort of infants in Uganda

BACKGROUND

Globally, BCG vaccination varies in efficacy and has some non-specific protective effects. Previous studies comparing BCG strains have been small-scale, with few or no immunological outcomes and have compared TB-specific responses only. We aimed to evaluate both specific and non-specific immune responses to different strains of BCG within a large infant cohort and to evaluate further the relationship between BCG strain, scarring and cytokine responses.

METHODS

Infants from the Entebbe Mother and Baby Study (ISRCTN32849447) who received BCG-Russia, BCG-Bulgaria or BCG-Denmark at birth, were analysed by BCG strain group. At one year, interferon-gamma (IFN-γ), interleukin (IL)-5, IL-13 and IL-10 responses to mycobacteria-specific antigens (crude culture filtrate proteins and antigen 85) and non-mycobacterial stimuli (tetanus toxoid and phytohaemagglutinin) were measured using ELISA. Cytokine responses, scar frequency, BCG associated adverse event frequency and mortality rates were compared across groups, with adjustments for potential confounders.

RESULTS

Both specific and non-specific IFN-γ, IL-13 and IL-10 responses in 1341 infants differed between BCG strain groups including in response to stimulation with tetanus toxoid. BCG-Denmark immunised infants showed the highest cytokine responses. The proportion of infants who scarred differed significantly, with BCG scars occurring in 52.2%, 64.1% and 92.6% of infants immunised with BCG Russia, BCG-Bulgaria and BCG-Denmark, respectively (p<0.001). Scarred infants had higher IFN-γ and IL-13 responses to mycobacterial antigens only than infants without a scar. The BCG-Denmark group had the highest frequency of adverse events (p=0.025). Mortality differences were not significant.

CONCLUSIONS

Both specific and non-specific immune responses to the BCG vaccine differ by strain. Scarring after BCG vaccination is also strain-dependent and is associated with higher IFN-γ and IL-13 responses to mycobacterial antigens. The choice of BCG strain may be an important factor and should be evaluated when testing novel vaccine strategies that employ BCG in prime-boost sequences, or as a vector for other vaccine antigens.

Comparison of tuberculin skin test response after three modalities of neonatal BCG vaccination

The aim of this study was to determine the tuberculin skin test (TST) response to three different BCG modalities [0.1 ml Tokyo (n=104), 0.05 ml Pasteur-Mérieux (n=137) and 0.1 ml Pasteur-Mérieux (n=100)] in a cohort of healthy newborns 5 months after vaccination at birth in Santiago, Chile. Among the 341 infants, 91.2% had a response to TST, and the mean+/-SD TST reaction size was significantly larger in infants receiving the Tokyo strain than in those receiving the 0.05 ml or 0.1 ml Pasteur-Mérieux strains (4.4+/-2.0, 3.5+/-1.3 and 3.1+/-1.4 mm, respectively; P<0.0001). The mean+/-SD of the BCG scar size was significantly lower in infants vaccinated with the Tokyo strain than in those vaccinated with the 0.1 ml Pasteur-Mérieux strain (3.9+/-1.2 vs. 4.3+/-1.1 mm; P=0.03) and no significant difference was found between infants receiving the Tokyo strain and the 0.05 ml Pasteur-Mérieux strain. However, the differences in TST size induced by diverse BCG vaccination modalities may not reflect the quality of the immunologically induced response in terms of TB protection.

New generation of mucosal adjuvants for the induction of protective immunity

Invasion of infectious agents through mucosal surfaces can be prevented by use of the common mucosal immune system (CMIS), which interconnects inductive tissues, including Peyer's patches (PPs) and nasopharyngeal-associated lymphoreticular tissue (NALT), and effector tissues of the intestinal and respiratory tracts. In order for the CMIS to induce maximal protective mucosal immunity, co-administration of mucosal adjuvant has been shown to be essential. When vaccine antigen is administered together with mucosal adjuvant, antigen-specific T-helper (Th) 1 and Th2 cells, cytotoxic T lymphocytes (CTLs) and IgA B cell responses are effectively induced by oral or nasal routes via the CMIS. In the early stages of induction of mucosal immune response, the uptake of orally or nasally administered antigens is achieved through a unique set of antigen-sampling cells, M cells located in follicle-associated epithelium (FAE) of inductive sites. After successful uptake, the antigens are immediately processed and presented by the underlying dendritic cells (DCs). Elucidation of the molecular/cellular characteristics of M cells and mucosal DCs will greatly facilitate the design of a new generation of effective mucosal adjuvants and of a vaccine delivery vehicle that maximises the use of the CMIS. Our recent efforts at mucosal vaccine development have focused on nasal administration of vaccine antigen together with nontoxic mutant-based or cytokine-/chemokine-based adjuvant for the induction of the protective immunity. To this end, a chimeric form of a nontoxic adjuvant combining the merits of mutant cholera toxin A subunit (mCT-A) and heat labile toxin B subunit (LT-B) was created as the second generation of detoxified toxin-based mucosal adjuvant. When a vaccine antigen was coexpressed together with an immune stimulatory/delivery molecule in crop seed, this edible vaccine is not only effective but also extremely practical in that it can be produced in huge quantities and preserved and shipped over long distances at room temperature without altering the quality of the vaccine. Because such qualities would greatly facilitate global vaccination, this new generation edible vaccines with a built-in adjuvant and/or M cell-targeted edible vaccine promises to be a powerful weapon for combating infectious diseases and bioterrorism.

HIV mucosal vaccine: nasal immunization with rBCG-V3J1 induces a long term V3J1 peptide-specific neutralizing immunity in Th1- and Th2-deficient conditions

In the vaccine strategy against HIV, bacillus Calmette-Guérin (BCG), a live attenuated strain of Mycobacterium bovis, is considered to be one of potential vectors for mucosal delivery of vaccine Ag. We analyzed the induction of the Ag-specific Ab response by nasal immunization with recombinant BCG vector-based vaccine (rBCG-V3J1) that can secrete the V3 principal neutralizing epitope of HIV. Mice were nasally immunized with rBCG-V3J1 (10 microg) three times at weekly intervals. Four weeks after the initial immunization, high titers of V3J1-specific IgG Abs were seen in serum. These high levels of HIV-specific serum IgG responses were maintained for >12 mo following nasal immunization without any booster immunization. V3J1-specific IgG-producing cells were detected in mononuclear cells isolated from spleen, nasal cavity, and salivary gland of the nasally vaccinated mice. Nasal rBCG-V3J1 also induced high levels of prolonged HIV-specific serum IgG responses in Th1 (IFN-gamma(-/-))- or Th2 (IL-4(-/-))-immunodeficient mice. Further, IgG3 was highest among V3 peptide-specific IgG subclass Ab responses in these immunodeficient mice as well as in wild-type mice. In addition, this Ag-specific serum IgG Abs induced by nasal immunization with rBCG-V3J1 possessed the ability to neutralize clinical isolate of HIV in vitro. These results suggested that the nasal rBCG-V3J1 system might be used as a therapeutic vaccine in addition to a prophylaxis vaccine for the control of AIDS.