The fermionic coset is a limit of the pure spinor formulation of the AdS 5 ×S 5 sigma model as well as a limit of a nonlinear topological A-model, introduced by Berkovits. We study the latter, especially its symmetries, and map them to higher spin algebras.We show the following. The linear A-model possesses affine pgl (4|4) 0 symmetry at critical level and its psl (4|4) 0 current-current perturbation is the nonlinear model. We find that the perturbation preserves W (2) 4 -algebra symmetry at critical level. There is a topological algebra associated to pgl (4|4) 0 with the properties that the perturbation is BRST-exact. Further, the BRST-cohomology contains world-sheet supersymmetric symplectic fermions and the non-trivial generators of the W (2) 4 -algebra. The Zhu functor maps the linear model to a higher spin theory. We analyze its psl (4|4) action and find finite dimensional short multiplets. *