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Characterization of the cytotoxin produced by macrophages in response to dengue virus-induced cytotoxic factor
Abstract:
We have observed earlier that dengue type 2 virus-induced cytotoxic factor (CF) induces macrophages to produce a cytotoxin (CF2) which kills mainly the macrophages, some of the T lymphocytes and has no effect on B-lymphocytes of normal mouse spleen. The findings of the present study show that CF2 is heat-labile, trypsin-sensitive and unstable at acid and alkaline pH. It is a low molecular weight product as it is dialysable, non-sedimentable on ultracentrifugation at 103,500 g for 3 h and passes through 0.22 micron Millipore filter. It is adsorbed onto the target normal mouse spleen cells. The properties of CF and CF2 have been compared.
Insights
Dengue type 2 virus triggers cytotoxic factor (CF) production in macrophages, creating a cytotoxin (CF2). This CF2 primarily targets macrophages and T lymphocytes, with its properties indicating a heat-labile, low molecular weight molecule.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Dengue type 2 virus infection can induce cytotoxic factor (CF) production by macrophages.
- This CF stimulates macrophages to release a secondary cytotoxin, termed CF2.
- CF2 exhibits selective toxicity towards macrophages and T lymphocytes, sparing B lymphocytes.
Purpose of the Study:
- To characterize the biochemical and physical properties of the macrophage-derived cytotoxin (CF2).
- To compare the properties of CF2 with its inducing factor, CF.
- To understand the mechanism of CF2-mediated cell death.
Main Methods:
- Assessing CF2 stability under varying conditions: heat, pH (acidic and alkaline), and enzymatic digestion (trypsin).
- Determining molecular weight through dialysis and ultracentrifugation.
- Evaluating cell permeability using Millipore filters.
- Investigating CF2 adsorption to target cells.
Main Results:
- CF2 was found to be heat-labile and trypsin-sensitive.
- It demonstrated instability at both acidic and alkaline pH levels.
- CF2 is a low molecular weight substance, evidenced by its dialyzability, failure to sediment at 103,500 g, and passage through a 0.22-micron filter.
- Adsorption of CF2 onto normal mouse spleen cells was observed.
Conclusions:
- CF2 is a heat-labile, low molecular weight cytotoxin produced by macrophages in response to dengue type 2 virus-induced CF.
- Its properties suggest it is a protein or peptide.
- CF2 selectively targets and potentially mediates cell death in macrophages and T lymphocytes, contributing to the immunopathology of dengue infection.