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Rational HIV vaccine design via mammalian cell display

Final Report Summary - RATIONAL HIV VACCINE (Rational HIV vaccine design via mammalian cell display)

This project aims to investigate one of the greatest challenges in HIV vaccine research: how can broadly neutralizing antibodies be induced by vaccination in humans to target pathogens such as HIV that have been resistant to traditional vaccination approaches?

AIM [i] Identification of HIV antigens that bind germ line and matured broadly neutralizing antibodies. This involved the generation of a panel of antigen variants and testing them for binding to neutralizing and germ line antibodies of this bnAb family and assessment of their ability to stimulate B cells expressing precursor antibodies.

AIM [ii] Optimization of antigens to favour elicitation of broadly neutralizing antibodies. This required the generation of combinatorial antigen libraries for mammalian display and selection of antigens with higher affinity for germ line and mature bnAbs. This work used flow cytometry-based cell sorting and antigen mutagenesis protocols.

AIM [iii] Using selected antigens to mature germ line antibodies to a broadly neutralizing phenotype. This aim involved extensive exploration of different cell sorting strategies and antibody mutagenesis methods. The optimized system was to use FACS to separate B cells that bound the antigen most tightly to enrich populations of cells with mutations that resulted in higher affinity.

•Directed evolution of PGT121 germ line binding antigens via mammalian display which stimulate B cells encoding germ line antibodies[1,2].
•Generation of cell lines expressing bnAb heavy chain precursor and germ line antibodies via endogenous locus replacement system to enable in vitro. maturation[3,4].
•Development of methodology to translate in vitro affinity maturation into naïve human B cells.

[1] Keystone HIV Vaccines meeting 2016: Steichen JM, McCoy LE, Kulp DW et al.
[2] Steichen et al. Immunity, 2016. 45: p. 1–14.
[3] Andrabi et al. Immunity. 2015 Nov 17;43(5):959-73.
[4] Cell and Gene Therapy for HIV Cure 2016: Voss JE, Andrabi R, McCoy LE et al.

FINAL GOAL: Validation of immune stimulation capacity of germline binding antigens to facilitate their development as immunogens.

POTENTIAL IMPACT: In vitro maturation of HIV neutralizing antibodies, which will allow faster iteration of immunogen candidates and the development of potential prophylactics and therapeutics.