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Small virus-like particles bud from the cell membranes of normal as well as HIV-infected human lymphoid cells
R R Dourmashkin1, D Bucher, J S Oxford
1Department of Medical Microbiology, London Hospital Medical College, England.
Abstract:
Electron microscopy (EM) of cell sections showed cell associated virus-like particles (VLP), 50-60 nm in diameter, budding from the membrane of human lymphoid cells in culture. The particles had an envelope continuous with the cell membrane and a dense core that almost filled the particle. Particles 70-80 nm in diameter with prominent external spikes were found in the culture medium by negative staining (medium-associated VLP). Cell-associated VLP were also present in cord lymphocytes, both on initial separation and after culture with or without foetal calf serum, and therefore were considered to be endogenous to the cells and were not bovine diarrhoea virus. VLP were observed in most of the lymphoid cell lines examined. VLP were also found less frequently in established human tumour and nontumour cell lines. Both cell-associated and medium-associated VLP were also present in HIV infected cell cultures, and they could be distinguished from HIV by their characteristic morphology and smaller size. It was not determined whether the 2 types of particle represented the same entity, or whether they were defective virus particles or a cellular secretory product.
Insights
Electron microscopy revealed virus-like particles (VLP) in human lymphoid cells. These endogenous VLP, distinct from HIV, bud from cell membranes and appear in culture medium.
Area of Science:
- Cell Biology
- Virology
- Microscopy
Background:
- Virus-like particles (VLP) are frequently observed in cell cultures.
- Their origin and exact nature can be challenging to ascertain.
- Distinguishing endogenous VLP from exogenous viral infections is crucial.
Purpose of the Study:
- To characterize virus-like particles (VLP) observed in human lymphoid cell cultures using electron microscopy.
- To determine the morphology, origin, and association of these VLP with different cell types.
- To differentiate these VLP from known viruses like HIV and bovine diarrhea virus.
Main Methods:
- Electron microscopy (EM) including negative staining was employed.
- Cell sections and culture medium from human lymphoid cell lines were analyzed.
- Comparison was made with HIV-infected cell cultures.
Main Results:
- Cell-associated VLP (50-60 nm) were observed budding from human lymphoid cell membranes.
- Medium-associated VLP (70-80 nm) with spikes were found in the culture medium.
- VLP were endogenous to cells, present in cord lymphocytes, and not bovine diarrhea virus.
- VLP were found in most lymphoid cell lines and less frequently in tumor/non-tumor cell lines.
- VLP in HIV cultures were morphologically distinct and smaller than HIV particles.
Conclusions:
- Endogenous virus-like particles (VLP) are present in various human lymphoid cell lines.
- These VLP exhibit distinct morphology and size compared to HIV.
- The precise nature of these VLP (defective virus or cellular product) requires further investigation.