The sequence of the CA-SP1 junction accounts for the differential sensitivity of HIV-1 and SIV to the small molecule maturation inhibitor 3-O-{3',3'-dimethylsuccinyl}-betulinic acid.
BACKGROUND
Despite the effectiveness of currently available antiretroviral therapies in the treatment of HIV-1 infection, a continuing need exists for novel compounds that can be used in combination with existing drugs to slow the emergence of drug-resistant viruses. We previously reported that the small molecule 3-O-{3',3'-dimethylsuccinyl}-betulinic acid (DSB) specifically inhibits HIV-1 replication by delaying the processing of the CA-SP1 junction in Pr55Gag. By contrast, SIVmac239 replicates efficiently in the presence of high concentrations of DSB. To determine whether sequence differences in the CA-SP1 junction can fully account for the differential sensitivity of HIV-1 and SIV to DSB, we engineered mutations in this region of two viruses and tested their sensitivity to DSB in replication assays using activated human primary CD4+ T cells.


RESULTS
Substitution of the P2 and P1 residues of HIV-1 by the corresponding amino acids of SIV resulted in strong resistance to DSB, but the mutant virus replicated with reduced efficiency. Conversely, replication of an SIV mutant containing three amino acid substitutions in the CA-SP1 cleavage site was highly sensitive to DSB, and the mutations resulted in delayed cleavage of the CA-SP1 junction in the presence of the drug.


CONCLUSIONS
These results demonstrate that the CA-SP1 junction in Pr55Gag represents the primary viral target of DSB. They further suggest that the therapeutic application of DSB will be accompanied by emergence of mutant viruses that are highly resistant to the drug but which exhibit reduced fitness relative to wild type HIV-1.
Zhou
Jing
J
Department of Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, USA. jing.zhou@vanderbilt.edu
Chen
Chin Ho
CH
Aiken
Christopher
C
D000818:Animals; D019380:Anti-HIV Agents / Q000494:pharmacology*; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D002460:Cell Line; D017931:DNA Primers; D024882:Drug Resistance, Viral; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007668:Kidney; D011268:Pregnancy-Specific beta 1-Glycoproteins / Q000502:physiology; D015302:Simian Immunodeficiency Virus / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D013386:Succinates / Q000494:pharmacology*; D014315:Triterpenes / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects; D053978:Pentacyclic Triterpenes
D019380:Anti-HIV Agents; D017931:DNA Primers; D011268:Pregnancy-Specific beta 1-Glycoproteins; D013386:Succinates; D014315:Triterpenes; C479935:bevirimat; D053978:Pentacyclic Triterpenes