Enhanced humoral and cellular immune responses after sublingual immunization against human papillomavirus 16 L1 protein with adjuvants

Needle-free nonparenteral vaccines offer a number of practical advantages, especially in developing countries. To address the effects of vaccine administration route, we tested mucosal and systemic immune responses against human papillomavirus 16 L1(HPV16L1) protein using intranasal, intravaginal, transdermal, sublingual (SL) and intramuscular routes. The SL route provided the most effective mucosal secretory IgA (sIgA) and serum IgG responses. After a 150 μg antigen dose via the SL route, saliva sIgA levels were 7.2- and 5.8-fold higher than those achieved via intravaginal and transdermal routes, respectively. Notably, SL administration even produced 4.6-fold higher levels of vaginal sIgA levels than did intravaginal delivery of 150 μg antigen. To enhance the immunogenicity of SL vaccines, we tested the adjuvanticity of nine molecules: three toll-like receptor agonists, three nucleotide-binding oligomerization-domain agonists, vitamin D3, poly-γ-glutamic acid and cholera toxin subunit B (CTB). Among the molecules tested, CTB provided the most enhanced mucosal sIgA and systemic IgG induction. SL-applied CTB enhanced the production of interleukin-4 and interferon-γ from stimulated CD4+ T cells. Moreover, interferon-γ-producing CD8+ T cell responses were increased 1.7-fold after co-treatment with SL CTB and HPV16L1. These results suggest the potential of the SL route for delivery of HPV16L1 vaccines using CTB as an adjuvant.