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Nonproductive infection of guinea pig cells with human cytomegalovirus
Abstract:
Human cytomegalovirus was capable of adsorbing to and penetrating guinea pig cells, but was unable to replicate new virus. Cultures infected with virus inoculum of high titer showed a cytopathic effect (CPE) characterized by cell rounding. This CPE depended upon the presence of infectious virus, and its extent was directly related to the multiplicity of infection. Staining by indirect immunofluorescence by using human convalescent sera was positive as early as 4 h postinfection. Maximal fluorescence was observed 24 h postinfection when 50% of the cells contained fluorescent antigens both in nuclei and cytoplasm. No evidence for viral replication was found, and no defective particles were detected by electron microscopy. Treatment with actinomycin D or with cycloheximide strongly inhibited both the fluorescent antigens and the CPE, whereas 5-fluorodeoxyuridine and bromodeoxyuridine were ineffective.
Insights
Human cytomegalovirus (CMV) can enter guinea pig cells, causing cell rounding (cytopathic effect), but cannot replicate. Viral antigens are detected via immunofluorescence within hours of infection.
Area of Science:
- Virology
- Cell Biology
- Immunology
Background:
- Human cytomegalovirus (CMV) is a common human herpesvirus.
- Understanding CMV interactions with non-human cells is crucial for viral research.
- Guinea pig cells offer a model for studying CMV entry and early events.
Purpose of the Study:
- To investigate the permissiveness of guinea pig cells to human CMV infection.
- To characterize the early cellular responses and viral antigen expression in infected guinea pig cells.
- To determine if viral replication occurs in this experimental system.
Main Methods:
- Infection of guinea pig cell cultures with human CMV.
- Observation of cytopathic effect (CPE) and cell morphology.
- Indirect immunofluorescence staining to detect viral antigens.
- Electron microscopy to identify viral particles.
- Treatment with antiviral drugs (actinomycin D, cycloheximide, 5-fluorodeoxyuridine, bromodeoxyuridine).
Main Results:
- Human CMV adsorbed to and penetrated guinea pig cells.
- A dose-dependent cytopathic effect (cell rounding) was observed.
- Viral antigens were detected by 4 hours post-infection, peaking at 24 hours.
- No evidence of viral replication or defective particles was found via electron microscopy.
- Actinomycin D and cycloheximide inhibited antigen expression and CPE, while nucleoside analogs were ineffective.
Conclusions:
- Guinea pig cells are non-permissive for human CMV replication.
- Human CMV can initiate an early infection cycle in guinea pig cells, including entry and antigen production.
- The inhibition by actinomycin D and cycloheximide suggests a host cell-dependent early event, not viral replication.