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Antibody-dependent, complement-mediated homologous and cross-cytolysis of togavirus-infected cells
Abstract:
The appearance of viral induced antigen(s) on Sindbis and Semliki Forest (SF) virus-infected chick embryo cells is detected with homologous mouse anti-viral antibody-dependent, complement-mediated cytolysis in a 51Cr release assay. Such antigen(s) is detected within 3 to 4 hr after infection whereas viral cytopathologic effects do not occur until 10 to 12 hr. In addition, significant heterologous cytolysis (anti-Sindbis on SF virus-infected cells, or, anti-SFV on Sindbis-infected cells) could be observed with serum samples tested. These sera were assayed for neutralizing and hemaggluatination-inhibition activities. Heterologous cytolysis cannot be correlated with hemagglutination-inhibition antibody titers nor is cross-neutralizing antibody detected. The possibility is discussed that another previously undefined antigen on infected cell membranes may be involved in heterologous cytolysis.
Insights
Viral antigens appear on chick embryo cells infected with Sindbis or Semliki Forest (SF) virus within hours. Antibody-dependent complement lysis detects these antigens, revealing potential cross-reactivity between viruses.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Sindbis and Semliki Forest (SF) viruses are alphaviruses that infect chick embryo cells.
- Viral antigens expressed on infected cell surfaces can be targets for immune responses.
- Antibody-dependent complement-mediated cytolysis is a mechanism to eliminate infected cells.
Purpose of the Study:
- To detect early viral antigen expression on Sindbis and SF virus-infected cells.
- To investigate homologous and heterologous antibody-dependent complement-mediated cytolysis.
- To explore the relationship between cytolysis, neutralizing antibodies, and hemagglutination-inhibition (HI) titers.
Main Methods:
- Chick embryo cells were infected with Sindbis or SF virus.
- Homologous and heterologous mouse anti-viral antibody-dependent, complement-mediated cytolysis was measured using a 51Cr release assay.
- Serum samples were assayed for neutralizing and hemagglutination-inhibition activities.
Main Results:
- Viral antigens were detected on infected cells 3-4 hours post-infection, preceding cytopathic effects (10-12 hours).
- Significant heterologous cytolysis was observed (anti-Sindbis on SF-infected cells and vice versa).
- Heterologous cytolysis did not correlate with HI antibody titers or detectable cross-neutralizing antibodies.
Conclusions:
- Early detection of viral antigens on infected cells is possible via antibody-dependent complement lysis.
- Cross-reactivity in cytolysis suggests the involvement of shared or cross-reactive antigens.
- An undefined antigen on infected cell membranes may be responsible for the observed heterologous cytolysis.