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Tuberculosis (TB) remains a major global public health problem. New immunization methods against TB are urgently needed. Plasmid DNA with a microneedle patch is a potentially attractive strategy to improve the immune effect. A DNA vaccine encoding the secreted protein Ag85B of Mycobacterium tuberculosis was immunized in the skin using microneedles, which can improve protective immunity compared to conventional intramuscular (IM) injection. There is no significant difference between microneedle patch (MNP) and IM immunization when the immunizing dose is low (4.2 μg). However, the results for detecting humoral immunity showed MNP immunization could better provoke an antibody response than IM when the dose is high (12.6 μg). A similar result was observed in cellular immune responses by measuring the cytokines in splenocytes. The effective protection of MNP can also be demonstrated by counting bacteria and analyzing the survival rate. This study indicated that DNA vaccination in the skin using dissolving microneedles may provide a new strategy against TB.

Polysaccharide nucleic acid fractions of bacillus Calmette–Guérin, termed BCG-PSN, have traditionally been used as immunomodulators in the treatment of dermatitis and allergic diseases. While the sales of injectable BCG-PSN have shown steady growth in recent years, no reports of using BCG-PSN powder or its immunotherapeutic effects exist. Here, BCG-PSN powder was applied directly to the skin to evaluate the immunotherapeutic effects on mice infected with Mycobacterium tuberculosis (MTB). In total, 34 μg of BCG-PSN powder could be loaded into a microneedle patch (MNP). Mice receiving BCG-PSN powder delivered via MNP exhibited significantly increased IFN-γ and TNF-α production in peripheral blood CD4 + T cells and improved pathological changes in their lungs and spleens compared to control group mice. The immunotherapeutic effect of BCG-PSN powder delivered via MNP was better than that delivered via intramuscular injection to some extent. Furthermore, MNPs eliminate the side effects of syringes, and this study demonstrated that BCG-PSN can be clinically administrated in powder form.