  The aim of this thesis is to explore the quantum aspects of Higher Spin
Gravities (HSGRAs) and their underlining algebraic structures. We give a
concise review of HSGRAs followed by three chapters with original results. The
first chapter is dedicated to the study of the vacuum one-loop correction of
holographic HSGRAs in Anti-de Sitter space. We show that there is a remarkable
agreement between the $F$-energy of HSGRAs in the bulk and the predictions
coming from the dual CFTs in integer dimensions. We extend this result to
continuous dimension and show that vacuum one-loop corrections in HSGRA
reproduce the $F$-energy of the Wilson-Fisher CFT in $4-\epsilon$ dimension.
The second part of the thesis explores the quantum properties of Chiral Higher
Spin Gravity - a closed subsector of any other HSGRA in four dimensions. We
show that Chiral Theory is UV-finite at one-loop. Moreover, there is an
interesting relation between one-loop amplitudes in Chiral HSGRA and the
self-dual subsector of QCD. The last part of the thesis is devoted to algebraic
structures of HSGRAs. As an application, we construct a formal bosonic HSGRA in
$AdS_5$ in two different ways: by deforming the Joseph relations and by
deforming the quasi-conformal realization.
