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Self-limiting, cell type-dependent replication of an integrase-defective human immunodeficiency virus type 1 in human
A Cara1, F Guarnaccia, M S Reitz
1Laboratory of Tumor Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
Abstract:
Integration of retroviral DNA into the host cell genome, catalyzed by the integrase (IN) protein, is thought to be required for replication. We show here that one IN-minus defective mutant of human immunodeficiency virus type 1 (HIV-1) is able to replicate in macrophages but not in peripheral blood lymphocytes (PBLs). Replication of the HIV-1 defective mutant, however, was inefficient and self-limiting. The absence of integration in the HIV-1 IN mutant in contrast to the wild-type implies that the replication of the IN mutant depends on the transcription of the extrachromosomal forms of viral DNA. In both PBLs and macrophages circular forms of DNA were detected at significant levels, indicating that the lack of a complete functional IN protein does not preclude nuclear import of HIV-1 DNA. Cell-associated p24 was absent in the IN-defective-infected PBLs, suggesting a transcriptional block of the extrachromosomal forms of HIV-1. These results show the existence of different strategies for HIV-1 replication depending upon the cell type, and indicate the necessity of integration of viral DNA for the self-maintained progression of the infection.
Insights
Human Immunodeficiency Virus type 1 (HIV-1) replication strategies differ by cell type. Integration of viral DNA is essential for sustained HIV-1 infection progression, particularly in peripheral blood lymphocytes (PBLs).
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Retroviral DNA integration into the host genome, mediated by integrase (IN), is considered crucial for replication.
- Human Immunodeficiency Virus type 1 (HIV-1) relies on this process for its life cycle.
Purpose of the Study:
- To investigate the role of integrase (IN) in HIV-1 replication across different cell types.
- To determine if HIV-1 can replicate without functional integrase and the implications for viral DNA transcription and integration.
Main Methods:
- Utilized an IN-minus defective mutant of HIV-1.
- Compared replication efficiency in macrophages versus peripheral blood lymphocytes (PBLs).
- Analyzed viral DNA forms (circular and integrated) and p24 antigen expression.
Main Results:
- The IN-minus HIV-1 mutant replicated in macrophages but not PBLs, albeit inefficiently.
- Absence of integration suggests replication relied on extrachromosomal viral DNA transcription.
- Circular DNA forms were detected in both cell types, indicating successful nuclear import.
- Lack of cell-associated p24 in PBLs pointed to a transcriptional block of extrachromosomal HIV-1 DNA.
Conclusions:
- HIV-1 employs distinct replication strategies dependent on the host cell type.
- Viral DNA integration is necessary for sustained and self-maintained HIV-1 infection progression.
- Functional integrase is critical for efficient HIV-1 replication in certain cell types like PBLs.