Background: Microneedles have previously been shown to enhance transdermal delivery of drugs and macromolecules. Their ability to effectively penetrate the dermis over a relatively large surface area offers potential use as minimally-invasive and painless replacements for more conventional parenteral vaccine regimens. In this study we compared the immune responses to HIV CN54gp140 using microneedles alone or a microneedle prime followed by mucosal boosting with monophosphoryl lipid A adjuvanted protein.Methods: Polymeric microneedle arrays that dissolve after piercing the skin were fabricated from poly(methylvinylether/ maleic acid) (Gantrez AN139) using laser-engineered siliconemicromould templates. Three groups of 8 BALB/c mice were primed using microneedles containing CN54gp140 and monophosphoryl lipid A. Three boosts were performed at two week intervals, using either the same microneedle formulation or vaginal or nasal administration of an antigen/adjuvant solution. Another group received four subcutaneous immunisations. Mice were sampled (serum and vaginal wash) prior to each vaccinationand two weeks post final immunization. Antigen-specific IgG and IgA production was assessed in the sera and mucosal lavage samples by quantitative ELISA. Splenocytes were harvested at necropsy and analysed for lymphocyte proliferation.Results: CN54gp140-specific serum IgG and lymphocyte proliferation responses were elicited in the subcutaneous immunization group and in those animals that were primed using microneedle delivery and boosted mucosally via the nasal route. Only the microneedle prime / intranasal boost group mounted a robust IgA response. In this group, IgG1 and IgG2a subtype quantification revealed a strong bias toward IgG2a.Conclusion: We have demonstrated that using a novel microneedle device to prime immunity followed by an intranasal boost elicits significant antigen-specific immune responses. This regimen generated similar serum IgG levels to the subcutaneous inoculations, but in contrast IgA was significantly elevated. This vaccination modality also induced a strong bias toward the IgG2a subtype suggesting a Th1 skewing of the immune response phenotype.