Effectiveness of BCG vaccination to aged mice

Abstract

Background: The tuberculosis (TB) still increases in the number of new cases, which is estimated to approach 10 million in 2010. The number of aged people has been growing all over the world. Ageing is one of risk factors in tuberculosis because of decreased immune responses in aged people. Mycobacterium bovis Bacillus Calmette Guérin (BCG) is a sole vaccine currently used for TB, however, the efficacy of BCG in adults is still a matter of debate. Emerging the multidrug resistant Mycobacterium tuberculosis (MDR-TB) make us to see the importance of vaccination against TB in new light. In this study, we evaluated the efficacy of BCG vaccination in aged mice.

Results: The Th1 responses, interferon-γ production and interleukin 2, in BCG inoculated aged mice (24-month-old) were comparable to those of young mice (4- to 6-week-old). The protection activity of BCG in aged mice against Mycobacterium tuberculosis H37Rv was also the same as young mice.

Conclusion: These findings suggest that vaccination in aged generation is still effective for protection against tuberculosis.

Figure 1

BCG vaccination to young and aged mice augments Th1 cytokine production by PPD stimulated splenocytes. Young (a, c) and aged (b, d) mice were immunized with 1 × 10⁶ CFU of BCG or phosphate buffered saline (PBS). Eight weeks after immunization, the animals were intravenously challenged with 1 × 10⁵ CFU of M. tuberculosis strain H₃₇Rv. Four weeks after challenge, the levels of IL-2 (a, b) and IFN-γ (c, d) in the culture supernatants of splenocytes stimulated with PBS (open column) or PPD (solid column) were measured by ELISA (BD Biosciences). Data represent mean ± SD of three mice. *, p < 0.05, compared with PBS-stimulation (student's t-test).

Figure 2

BCG protects both young and aged mice against M. tuberculosis infection. Young (a) and aged (b) mice were immunized with 1 × 10⁶ CFU of BCG (solid column) or PBS (open column). Eight weeks after immunization, the mice were intravenously challenged with 1 × 10⁵ CFU of M. tuberculosis strain H₃₇Rv. Four weeks after challenge, the bacterial numbers in the lung and spleen were determined by colony assay. Data represent mean ± SD of three mice. *, p < 0.05, compared with PBS-inoculated control group (student's t-test).