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Genetic characterization of simian immunodeficiency virus isolated from an African mandrill
H Sakai1, J Sakuragi, S Sakuragi
1Institute of Virus Research, Kyoto University, Japan.
Abstract:
We constructed an infectious molecular clone of simian immunodeficiency virus from an African mandrill (SIVMND). Upon transfection, this clone directed the production of progeny virus particles infectious to and cytopathic for CD4+ human leukemia cells. Thirteen frameshift proviral mutants with an alteration in the eight open reading frames of SIVMND were generated by recombinant DNA techniques, and were analyzed biologically and biochemically. While mutations in the structural genes gag, pol, and env abolished viral growth and induction of cytopathology, mutants of the vif, vpr, and nef genes were fully biologically active. Of the tat and rev mutants, only one rev mutant grew in CD4+ cells with delayed kinetics. In reporter-based transient expression systems, transactivation potentials of the tat and rev mutants were evaluated. A mutant lacking 2nd coding exon of tat gene exhibited tat activity similar to that of the wild type clone. The infectious rev mutant was partially defective for rev gene activity.
Insights
Researchers created an infectious simian immunodeficiency virus (SIVMND) clone from mandrills. Mutational analysis revealed essential roles for gag, pol, and env genes, while vif, vpr, and nef were dispensable for viral replication.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Simian immunodeficiency virus (SIV) is a lentivirus that infects non-human primates.
- Understanding SIV gene function is crucial for insights into human immunodeficiency virus (HIV) pathogenesis.
- The SIVMND isolate from African mandrills provides a model for studying lentiviral replication and host interactions.
Purpose of the Study:
- To construct an infectious molecular clone of SIVMND.
- To investigate the biological and biochemical roles of SIVMND open reading frames (ORFs).
- To elucidate the function of accessory genes (vif, vpr, nef, tat, rev) in viral replication and cytopathicity.
Main Methods:
- Construction of an infectious SIVMND molecular clone.
- Generation of frameshift proviral mutants using recombinant DNA techniques.
- Biological assays to assess viral growth and cytopathicity in CD4+ cells.
- Biochemical analyses and reporter-based transient expression systems to evaluate gene function.
Main Results:
- The SIVMND clone produced infectious and cytopathic progeny virus.
- Mutations in gag, pol, and env genes abrogated viral replication and cytopathology.
- Mutants in vif, vpr, and nef genes remained biologically active.
- A rev mutant exhibited delayed replication kinetics and partial defects in rev gene activity.
- A tat mutant lacking the second coding exon showed wild-type tat activity.
Conclusions:
- The structural genes gag, pol, and env are essential for SIVMND replication.
- Accessory genes vif, vpr, and nef are not essential for replication in CD4+ cells.
- The rev gene plays a critical role in viral replication, with partial functional redundancy.
- The tat gene's second coding exon is not essential for transactivation activity.