Molecular biology and structure of a novel penaeid shrimp densovirus elucidate convergent parvoviral host capsid evolution

Significance Parvoviruses (PVs) are ssDNA viruses, with T = 1 icosahedral symmetry, infecting deuterostome and protostome animals. Most PVs have a highly conserved phospholipase A2 domain (PLA2) in the N-terminal region of their minor capsid protein. Under acidic pH, during endosomal/lysosomal egress, the PLA2 domain is activated to disrupt vesicle membranes. However, certain PVs lack the PLA2 and thus must use a different escape mechanism. Our study offers insight into this enigma, showing how a recently discovered PV of marine crustacean has evolved a cation-dependent mechanism to accomplish this task. We also show how host-driven convergent evolution pushed two PVs, infecting the same host species, to adopt strikingly similar surface morphologies, despite distinct multimer interactions and lack of sequence similarity.