Vaccines save millions of lives each year and are among the greatest achievements of biomedical science and most cost-effective health interventions ever developed. Vaccines for diphtheria, mumps, pertussis, and tetanus are good examples. Recommendation of these vaccines before 1980 contributed to a greater than 92% decline in cases and a 99% or greater decline in deaths. Endemic transmission of poliovirus, measles, and rubella viruses has been eliminated in the United States; smallpox has been eradicated worldwide. Vaccine plays a very important role in disease control and elimination. By improving vaccines, many more lives could be saved each year.

There are still a number of severe diseases that don't have an effective vaccine, such as hepatitis c, tuberculosis, and malaria. Researchers conclude that the reason why most of the vaccines against these diseases failed to simulate effective immunity is due to the lack of T cell immune response. For many infectious diseases, T cells play an important role in naturally acquired protective immune response. T cells have to be activated to trigger humoral and cytotoxic pathways and they are essential to the induction of high-affinity antibodies and immune memory. Optimizing T cell response by vaccination has been the aim of many scientists and is thought to be the future of vaccine development.

To make a breakthrough of the dilemma, we focus on the enhancement of vaccines. Some of the vaccines are used along with immunologic adjuvant to stimulate an effective immune response. Adjuvants are compounds that can be added to vaccines to improve immunogenicity by triggering the innate immune responses and thus accelerate, prolong, or enhance antigen-specific immune response. However, the adjuvants nowadays are deficient in activation of T cell response. This year, we established a new model system to generate antigen-specific Leishmania adjuvant as a T cell stimulator- Leijuvant.