Fibril formation of naturally occurring prostatic acid phosphatase fragments and their effect on viral infection and transduction

Amyloidogenic peptides present in human semen self-assemble into positively charged fibrils that markedly increase HIV-1 infection by neutralizing the negative charge repulsion between virions and cells. SEVI (semen derived enhancer of viral infection) is the best characterized seminal amyloid and forms out of the prostatic acid phosphatase fragment 248-286. Although the effects of SEVI on viral infection have been analyzed in detail, it was largely unclear how changes in environmental parameters such as temperature or pH affect fibril formation of PAP248-286 and three naturally occurring cleavage products of this peptide. To investigate this, PAP248-286, the N-terminal PAP248-259, the middle PAP260 272 and the C-terminal PAP273-286 fragment were agitated under various conditions and analyzed for fibril yield, surface charge zeta-potential, morphology (transmission electron and atomic force microscopy) and virion attachment (fluorescence microscopy). Additionally, the functional activity in enhancing HIV-1 infection and retroviral transduction were analyzed. These analyses revealed that changes in environmental parameters dramatically affected fibril formation of PAP248-286 and PAP273-186 but had no effect on fibrillization of the PAP260-272 peptide. Overall, the fibrils considerably varied in shape and charge and enhanced viral infection with different efficiencies. A structure function analysis revealed that not the charge or the amount of fibrils but rather the available surface and the surface area to volume ratio are key determinants for amyloid-mediated infectivity enhancement. Thus, a high number of small fibrils is more efficient in boosting viral infection than a comparably low number of larger fibrils. The results presented in this thesis provide novel mechanistically insights in how seminal amyloid promotes HIV-1 infection and will help to develop more effective transduction enhancers to improve retroviral gene transfer