Tuberculosis (TB) infection was evaluated in Brazilian immunocompetent children and adolescents exposed and unexposed (control group) to adults with active pulmonary TB. Both groups were analysed by clinical and radiological assessment, TST, QFT-IT and T-SPOT.TB. The three tests were repeated after 8 weeks in the TB-exposed group if results were initially negative. Individuals with latent tuberculosis infection (LTBI) were treated and tests were repeated after treatment. Fifty-nine TB-exposed and 42 controls were evaluated. Rate of infection was 69·5% and 9·5% for the exposed and control groups, respectively. The exposed group infection rate was 61% assessed by TST, 57·6% by T-SPOT.TB, and 59·3%, by QFT-IT. No active TB was diagnosed. Agreement between the three tests was 83·1% and 92·8% in the exposed and control groups, respectively. In the exposed group, T-SPOT.TB added four TB diagnoses [16%, 95% confidence interval (CI) 1·6–30·4] and QFT-IT added three TB diagnoses (12%, 95% CI 0–24·7) in 25 individuals with negative tuberculin skin test (TST). Risk factors associated to TB infection were contact with an adult with active TB [0–60 days: odds ratio (OR) 6·9; >60 days: OR 27·0] and sleeping in the same room as an adult with active TB (OR 5·2). In Brazilian immunocompetent children and adolescents, TST had a similar performance to interferon-gamma release assays and detected a high rate of LTBI.

National policies regarding the BCG vaccine for tuberculosis vary greatly throughout the international community and several countries are currently considering discontinuing universal vaccination. Detractors of BCG point to its uncertain effectiveness and its interference with the detection and treatment of latent tuberculosis infection (LTBI).

In order to quantify the trade-off between vaccination and treatment of LTBI, a mathematical model was designed and calibrated to data from Brazil, Ghana, Germany, India, Mexico, Romania, the United Kingdom and the United States. Country-specific thresholds for when LTBI treatment outperforms mass vaccination were found and the consequences of policy changes were estimated.

Our results suggest that vaccination outperforms LTBI treatment in all settings but with greatly reduced efficiency in low incidence countries. While national policy statements emphasize BCG’s interference with LTBI detection, we find that reinfection should be more determinant of a country’s proper policy choice.

BalB/C neonate mice and adult BalB/C mice were vaccinated using BCG (Bacille Calmette–Guerin). The pathogenic growth characteristics of BCG in in vitro culture on spleen cells (SPC) were observed and changes in induced expression of IFN (interferon)-γ and IL (interleukin)-4 in SPC were detected using the ELISPOT assay. The results showed that a low dose of BCG (2×103 cfu) exerted 100% immunoprotection on 7-day-old neonate mice and a high dose of BCG (4×104 cfu) exerted 75% immunoprotection. A low dose of BCG (2×103 cfu) exerted 67% immunoprotection on 35-day-old mice. It is also shown that Th1-type cell immunity dominated by IFN-γ was enhanced significantly in the neonate mice injected with a low dose of BCG (2×103 cfu), and Th2-type cell immunity dominated by IL-4 was depressed at the same time. IFN-γ and IL-4 induced by a high dosage of BCG (4×104 cfu) in neonate mice were both increased. IFN-γ and IL-4 induced by a low dose of BCG (2×103 cfu) in 35-day-old mice were also increased. The results indicate that there exists a marked correlation between immunoprotection by BCG in mice and both the immunizing dose and age of the immune animals, which might be relevant to the changes induced by BCG on Th1- and Th2-type cell immunity.

Heterologous immunity, or protection by one invading organism against another across phylogenetic divides, has been recognised for decades. It was initially thought to operate largely through enhancement of phagocytosis, but this explanation became untenable when it was realised it worked extremely well against intraerythrocytic protozoa and killed them while they were free in the circulation. Clearly a soluble mediator was called for. This review summarises the logic that arose from this observation, which led to a wider appreciation of the roles of pro-inflammatory cytokines, and then nitric oxide, in the host's response against invaders, as well as the ability of these mediators to harm the host itself if they are generated too enthusiastically. This has led to a discernable pattern across heterologous immunity as a whole, and its lessons influence a range of areas, including vaccine development.

The protective potential of killed Leishmania major (ALM) along with BCG was evaluated against L. donovani in Indian langur monkeys in single and triple dose schedules. A delayed protection was observed in monkeys after a single dose schedule of ALM (3 mg)+BCG (3 mg) given intradermally 2 months before intravenous challenge with L. donovani. Triple dose schedule each of 1 mg ALM+1 mg BCG was more effective. The status remained unchanged until the end of the experiment (approximately 8 months). The study indicates that a combination of ALM+BCG may be a good candidate vaccine for exploiting against human Kala-azar.