We recently proposed that specific targeting of PP2A holoenzymes by viral proteins is a general biological strategy, used by various viruses (from DNA tumour viruses to HIV-1) to specifically deregulate intracellular pathways of their hosts. Based on a recent patented observation we proposed a new hypothesis named “The Quinta Columna theory”. This scientific hypothesis predicts that the presence of virally-encoded PP2A-binding sequences in biological fluids of infected patients may deregulate PP2A-dependent homeostasis. This ongoing project is based on development of an ELISA test to analyze the presence of specific viral sequences in biological fluids (serum, and if possible CSF) (see also fig. below).