Is the BCG vaccine safe for undernourished individuals?

Abstract

Cellular immunity is critical for protection against tuberculosis, but its integrity is compromised during undernutrition. The present study was designed to evaluate if the attenuated mycobacterium BCG is a safe vaccine for undernourished individuals. An experimental model of undernutrition was established by subjecting BALB/c mice to dietary restriction. These animals received 70% of the amount of food consumed by the healthy control group and exhibited physiological alterations compatible with malnutrition, including body weight loss, reduced levels of triglycerides and glucose, and reduced lymphocyte numbers. Undernourished mice were immunized with BCG, and the mycobacterial loads in lymph nodes, spleen, liver, lungs, and thymus were determined. A much higher proportion of undernourished mice exhibited bacterial dissemination to the lymph nodes, spleen and liver. In addition, only undernourished animals had bacteria in the lungs and thymus. Concomitant with higher mycobacterial loads and more widespread BCG dissemination in undernourished mice, production of TNF-α, IFN-γ, and IL-10 was also diminished in these mice. Taken together, these results indicate that BCG infection is more severe in undernourished mice. Whether a similar phenomenon exists in undernourished children or not remains to be thoroughly investigated.

Figure 1

Effect of undernutrition on BCG dissemination. BALB/c mice were submitted to 10 days of dietary restriction and then immunized with BCG. Bacilli were recovered from the lymph nodes and thymus 15 days after BCG immunization. CFU values represent mean ± standard deviation of 6–10 animals.

Figure 2

Effect of undernutrition on cytokine production by BALB/c mice immunized with BCG. Splenic cells were stimulated with rhsp65 or ConA, and IFN-γ, TNF-α, and IL-10 production were measured by ELISA. Evaluations were performed 25 days after the beginning of dietary restriction, that is, 15 days after BCG immunization. Values represent mean ± standard deviation of 6-7 animals. *P ≤ 0.05.