Oxathiolane nucleoside analog resistance in a pathogenic molecular clone of feline immunodeficiency virus and Mapping in vivo replication and pathogenesis determinants of Aleutian mink disease parvovirus

Part I. Antiretroviral drug resistance develops during treatment of human immunodeficiency virus type 1 (HIV-I) infection, but the consequences of drug resistance on HIV-I pathogenesis and the clinical relevance of these consequences have not been thoroughly studied. These questions can be addressed in an animal model of natural lentivirus infection. The present study examined site-directed mutants of a pathogenic molecular clone of feline immunodeficiency virus (FIV), FIV-pPPR, as potential models for studying the effects of (--)-beta-L-2 ',3'-dideoxy-3 '-thiacytidine (3TC, lamivudine) resistance on lentiviral pathogenesis. A methionine-to-valine (M183V) mutation at codon 183 of FIV, located in the highly conserve d YMDD motif of the RT-encoding region of the pol gene, conferred high-level phenotypic resistance to 3TC and cross-resistance to the related compound, (--)-beta-L-2',3 '-dideoxy-5-fluoro-3'-thiacytidine [(--FTC]. 3TC resistance was similar in magnitude to HIV-I with a homologous mutation at codon 184 (M184V) that characteristically develops in 3TC-treated HIV-I-infected patients. This FIV-pPPR M183V mutant will be useful in studying the effects of 3TC resistance on lentiviral pathogenesis.; Part II. The ADV-Utah I biological isolate of Aleutian mink disease parvovirus (ADV) replicates efficiently and is highly pathogenic in mink but cannot be propagated in vitro. The ADV-G molecular clone derived from cell culture-adapted ADV-Utah I does not replicate or cause disease in adult mink but can be propagated to high titers in vitro . Recently, the first chimeric viruses of ADV-Utah I and ADV-G that could replicate both in vitro and in vivo and cause pathogenesis in mink were described. ADV-G/U-8 infection was associated with higher antibody titers and more severe histopathological lesions than ADV-G/U-10. These chimeras, however, differed by only one capsid and three nonstructural protein amino acid changes. The purpose of the current studies was to determine whether differences in in vivo replication and pathogenesis between G/U-8 and G/U-10 were attributable to capsid or nonstructural protein changes. In order to answer this question, additional chimeric viruses were constructed, propagated in vitro, and used to infect mink. Antiviral antibody responses, viremia, hypergammaglobulinemia, and histopathological lesions indicated that codon 352 of the capsid protein influenced in vivo replication and pathogenesis, but the effects of the nonstructural protein likely played an interactive role as well.