發展以醣質為抗原之HIV-1疫苗: 設計、合成、以及免疫評估

Abstract

Abstract An HIV vaccine continues to be the best hope to end the HIV pandemics. The challenge of HIV vaccine development is to design the immunogens to induce the antibodies that can have broadly neutralizing activities. An effective mechanism that HIV uses to avoid attacks of neutralizing antibodies is to coat envelope gp120 with heterogeneous N-linked carbohydrate structures. Recently, a class of broadly neutralizing antibodies (bNAbs), isolated from HIV positive donors, was shown to be potent in neutralizing primary HIV-1 strains across clades by targeting the glycan dependent epitopes on gp120 surface, demonstrating the feasibility of inducing such antibodies. Understanding the molecular mechanism of the HIV-gp120 glycan coat recognition by bNAbs may guide effective immunogen design. This thesis describes the efficient chemical and enzymatic syntheses of diverse HIV-1 gp120 related high-mannose, hybrid, and complex type N-glycans. A well defined library of natural and unnatural N-glycan structures was used to develop glycan microarray platform for profiling glycan binding specificities of HIV-1 bNAbs, PG9, PG16, PGTs 121, 128, and 141-145. With the next generation array on aluminium oxide-coated glass (ACG) slide, the critical low affinity antibody-carbohydrate interactions were detected. In addition, we showed that a few highly potent HIV-1 broadly neutralizing antibodies exhibit strong binding to closely spaced hetero-glycans on array surface, suggesting that this phenomenon might be an important adaptation of host immune system to deal with heterogeneously glycosylated HIV-1 spike. The microarray studies of glycan binding specificities of HIV-1 bNAbs established a structural basis for designs of immunogens based on epitopes recognized by these antibodies. Finally, the immunological evaluation of carbohydrate-based immunogens was performed to investigate whether the synthetic glycoconjugates can induce broadly neutralizing antibodies that can cross react with HIV-gp120. Keywords HIV-1 vaccine, N-linked oligosaccharides, carbohydrate-based immunogens, broadly neutralizing antibodies, glycoconjugates, carbohydrate synthesis.