Live attenuated vaccines have been highly effective in controlling human infections such as smallpox, yellow fever, measles, mumps, rubella, and chicken pox. These live vaccines stimulate robust humoral and cell-mediated immunity that can persist for decades after vaccination. Despite their effectiveness, there are disadvantages of using live attenuated vaccines, which include reversion to virulence, severe adverse effects, and contraindication in pregnant and immunocompromised individuals. In light of these risks, vaccine formulations are increasingly based on highly purified subunit antigens and/or antigens produced by recombinant DNA technology. However, subunit antigens are intrinsically poor immunogens and therefore mixed with substances called adjuvants to enhance immunogenicity. There are only a few adjuvants approved for human use and currently used adjuvanted inactivated/subunit vaccines largely elicit humoral immunity, often require repeated immunization to maintain protective levels of immunity, and typically stimulate poor CD8 T cell responses. There is emerging consensus that vaccines against complex pathogens like HIV, M. tuberculosis, and Plasmodium will require both antibodies and CD8 T cells. Development of vaccine formulations that combine the immunogenicity of live vaccines (elicit strong antibody and CD8 T cell immunity) and the safety of subunit vaccines remains a daunting challenge for immunologists. Carbomers (polymers of acrylic acid) have been used in the pharmaceutical industry to achieve controlled release of medications in tablets and as a bioadhesive in mucosal applications. We have identified a carbomer-based adjuvant that stimulated a surprisingly potent CD8 T cell response to a soluble antigen, following a single immunization. Remarkably, the CD8 T cell response elicited by this adjuvant was as strong as those induced by infection with recombinant listeria and vaccinia virus, which are known to stimulate robust cell-mediated immunity. The central hypothesis is that, "Like live vaccines, carbomer-adjuvanted subunit vaccine programs the development of durable and protective CD8 T cell memory that confers long-term immunity against systemic and respiratory viral infections".
The specific aims of this proposal are to: (1) investigate whether differentiation of effector and memory CD8 T cells differs for live replicating and carbomer- adjuvanted subunit non-replicating antigens;(2) determine whether memory CD8 T cells induced by live vaccines and non-replicating carbomer-adjuvanted vaccine differ in their protective abilities against systemic and respiratory viral infections. The proposed studies will provide fundamental insights into the programming of effector and memory CD8 T cells by replicating and non-replicating soluble antigens, and are expected to have high impact in the field of CD8 T cell memory. The highly innovative aspect of this proposal is the potential for developing safe subunit vaccines that are as immunogenic as live vaccines in stimulating cell-mediated immunity against intracellular pathogens of humans.
Development of effective vaccines is the time-tested approach for controlling infectious diseases of humans. Currently used inactivated or subunit vaccines are safe but primarily induce antibodies and fail to stimulate adequate CD8 T cell immunity. It is crucial to develop subunit vaccines that stimulate potent antibodies and CD8 T cell responses to protect against AIDS, tuberculosis, and malaria. Studies in this proposal might lead to the identification of an adjuvant that can stimulate potent humoral and cell-mediated immunity against intracellular pathogens of humans.
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