THE CAPSID DETERMINANT OF FIBROTROPISM FOR THE MVMP STRAIN OF MINUTE VIRUS OF MICE FUNCTIONS VIA VP2 AND NOT VP1

The minute virus of mice, prototype strain MVMp, productively infects cultured murine fibroblasts but not T cells. The immunosuppressive str ain, MVMi, shows the converse tropism, These reciprocal tropisms are m ediated by the viral capsids, in which their determinants have been ma pped to a few specific amino acids in the primary sequence shared by V P1 and VP2. Which of these proteins is relevant in presenting these de terminants during infection is not known. We have approached this ques tion using a recombinant parvovirus system in which a LuIII derived tr ansducing genome, containing the luciferase reporter in place of viral coding sequences, can be packaged by capsid proteins from separate he lper sources. We generated transducing virions by using helper constru cts expressing either VP1 or VP2, containing the MVMp or MVMi tropic d eterminant region, in various combinations, The virions were used to i nfect human NB324K cells and murine A9 fibroblasts, Transduction of th e human cells (permissive for both MVMp and MVMi) required both VP1 an d VP2 and was successful with all combinations of these proteins, In c ontrast, significant transducing activity for A9 cells was detected on ly with recombinant virions containing VP2 of MVMp, while the use of e ither source of VP1 had little effect, We conclude that VP2 from MVMp is necessary to enable infection of murine A9 fibroblasts.