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Neutralizing antibodies modulate replication of simian immunodeficiency virus SIVmac in primary macaque macrophages
M F McEntee1, M C Zink, M G Anderson
1Division of Comparative Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Abstract:
Cultured macaque macrophages are permissive for the replication of SIVmac251, and inoculation with virus is followed by the production of viral p27. Neutralizing macaque polyclonal and murine monoclonal antibodies preincubated with the virus prevented infection but did not prevent cytopathic virus replication when added more than 3 days after inoculation with virus. However, application of the neutralizing antibodies to macrophages 24 h after inoculation with virus resulted in sustained, low-level production of viral antigen. Cell lysates and individual macrophages from treated cultures contained less viral protein by Western blot (immunoblot) and immunocytochemistry than untreated controls. In situ hybridization and polymerase chain reaction procedures for detecting and estimating relative amounts of viral RNA and DNA showed that both viral nucleic acids failed to increase beyond the levels obtained before the addition of neutralizing antibodies. The data suggest that macrophages may need to be infected with a minimum threshold of virus particles in order to reach their full potential for virus replication and that their exposure to neutralizing antibodies prior to reaching this threshold resulted in limited virus replication.
Insights
Neutralizing antibodies limit simian immunodeficiency virus (SIV) replication in macaque macrophages if applied early. Early antibody treatment prevents full viral replication, suggesting a threshold is needed for macrophages to become highly infected.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Cultured macaque macrophages support simian immunodeficiency virus (SIV) replication.
- Viral p27 antigen production follows SIVmac251 inoculation in these cells.
Purpose of the Study:
- To investigate the effect of neutralizing antibodies on SIV replication in macaque macrophages.
- To determine the impact of antibody timing on viral antigen and nucleic acid levels.
Main Methods:
- Using cultured macaque macrophages and SIVmac251.
- Employing neutralizing macaque polyclonal and murine monoclonal antibodies at different time points post-inoculation.
- Analyzing viral protein expression via Western blot and immunocytochemistry.
- Quantifying viral RNA and DNA using in situ hybridization and polymerase chain reaction.
Main Results:
- Pre-incubation of antibodies with SIV prevented infection.
- Antibodies applied >3 days post-inoculation did not inhibit cytopathic replication.
- Antibodies applied 24h post-inoculation resulted in sustained, low-level viral antigen production.
- Western blot, immunocytochemistry, in situ hybridization, and PCR showed reduced viral components in treated cultures compared to controls.
Conclusions:
- Macrophages may require a minimum viral threshold for maximal replication.
- Early exposure to neutralizing antibodies before this threshold limits SIV replication in macrophages.
- Timing of antibody intervention is critical for controlling SIV replication in macrophages.