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In recent years the glycan shield of the HIV-1 envelope spike (Env) has emerged as a potential target for microbicide and vaccine design. The densely packed glycans on its surface include an intrinsic population of under-processed oligomannose structures, and a number of lectins and broadly neutralising antibodies (bnAbs) have been isolated which are reactive to these ‘non-self’ glycan structures. The potential value of these agents in therapeutic or vaccine contexts depends upon the prevalence of their glycan targets in nature and their resilience to sequence mutation. Here the prevalence of oligomannose-type glycans on recombinant gp120 was demonstrated across a panel of isolates, revealing subtle cross clade differences. Alanine scanning of all potential N-glycosylation sites (PNGSs) within a model gp120 demonstrated the overall stability of the oligomannose population, but highlighted regions of glycan clusters where individual glycans act to limit the processing of their neighbours. This was formally demonstrated for the N332 ‘site of vulnerability’, where deletion of nearby glycosylation sites led to altered glycan processing at the N332 site. A panel of N332-dependent bnAbs was screened for their ability to tolerate such changes in glycan processing, with differing results. While some displayed promiscuous binding, others were more sensitive to glycan microheterogeneity. Site-specific glycosylation analysis of the PGT135 epitope revealed that an intolerance of certain glycoforms may explain its limited breadth. While a greater understanding of Env glycan microheterogeneity and bnAb promiscuity is required, these findings reveal insights into the architecture of the HIV-1 glycan shield that suggest it is a conserved and robust target for drug and vaccine design.

Les virus Hendra (HeV) et Nipah (NiV) sont des virus émergents appartenant à la famille des Paramyxovirus et au genre des Hénipavirus. Chaque année, ils sont responsables de nombreuses épidémies touchant plusieurs espèces animales dont les hommes, avec une forte morbidité et mortalité. À ce jour, aucun vaccin ni traitement ne sont commercialisés. Ce projet porte sur le développement d’un vaccin génétique pour lutter contre une infection par les Hénipavirus. La stratégie suivie, repose sur l’injection in vivo de vecteurs recombinants dérivés du virus Adéno-Associé (AAVr) codant pour la glycoprotéine d’enveloppe G du virus NiV. Une première expérience réalisée chez la souris, a montré qu’une seule injection de vecteurs AAVr par voie IM permet le développement d’une réponse humorale contre la protéine G, forte et stable dans le temps. Afin de tester le pouvoir protecteur de ce vaccin, des hamsters ont été infectés par les Hénipavirus, compte tenu de leur grande sensibilité à ces infections. L’injection de vecteurs AAVr chez ces animaux a permis de protéger 100 % des animaux infectés par le virus NiV et 50 % des animaux infectés par le virus HeV. Cette étude apporte une nouvelle approche de vaccination et de nouvelles perspectives concernant l’utilisation des vecteurs AAVr pour lutter contre des infections virales émergentes. / Nipah virus (NiV) and Hendra virus (HeV) are closely related, recently-emerged Paramyxoviruses, capable of causing considerable morbidity and mortality in several mammalian species, including humans. Commercially available Henipavirus-specific vaccines are still unavailable and development of novel antiviral strategies to prevent this lethal infection is highly desirable. Here we describe the development of Adeno-Associated Virus (AAV) vaccines expressing the NiV G protein. Characterization of these vaccines in mice demonstrated that a single intramuscular AAV injection was sufficient to induce a potent and long lasting antibody response. Translational studies in hamsters further showed that 100 % of vaccinated animals were protected against a lethal challenge with NiV In addition, this vaccine and induced a cross-neutralizing immune response able to protect 50 % of the animals against a challenge HeV. Altogether, this study presents a new vaccination approach which opens new perspectives toward the evaluation of AAV vectors as a vaccine against these emergent diseases.

HIV-1 is a dangerous retrovirus which represents one of the world's leading health problems. HIV-1 infection is incurable and without proper treatment by antiretroviral therapy it leads to death within several years. Despite intensive research, no HIV vaccine is currently available. This thesis presents a new and unique approach which has not been used for vaccine development yet. The promising strategy is based on small binding proteins that can elicit broadly neutralizing HIV-1 antibodies by mimicking their epitopes. The aim of this project was to select and characterize small binding proteins that can successfully mimic the surface of viral envelope glycoproteins that is recognized by the broadly neutralizing HIV-1 antibodies PGT121 and PGT126. Proteins were selected from a highly complex combinatorial protein library derived from a new type of scaffold called Myomedin. Firstly, the extent of the protein library was narrowed down using the ribosome display. Then the direct sandwich ELISA screening was applied to select scaffold variants that interact with the target antibodies. In total over 200 variants were tested and several promising candidates were found. These Myomedin variants were purified, biochemically and biophysically characterised and the best ones were used to immunize mice....