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Published on: June 19, 2014
Neutralization sensitivity and accessibility of continuous B cell epitopes of the feline immunodeficiency virus
J Richardson1, I Fossati, A Moraillon
1Génétique des Virus (ICGM-CNRS UPR 0415), Institut Cochin de Génétique Molëculaire, Paris, France.
Insights
Antibodies targeting the V3 region can neutralize feline immunodeficiency virus (FIV). However, most FIV envelope epitopes are poorly exposed on infected cells, limiting antibody neutralization effectiveness.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Feline immunodeficiency virus (FIV) infection in cats elicits antibodies against viral envelope glycoproteins.
- Neutralization of FIV by antibodies is complex, influenced by viral adaptation and cellular substrate.
Purpose of the Study:
- To systematically analyze continuous B cell epitopes of a primary FIV isolate's envelope.
- To evaluate the neutralizing capacity of antibodies against FIV envelope domains in different cell models.
Main Methods:
- Analysis of B cell epitopes on FIV envelope domains.
- Neutralization assays using feline antisera against primary and lab-adapted FIV strains (Wo and Petaluma).
- Comparison of neutralization efficiency in feline peripheral blood mononuclear cells (PBMC) and Crandell feline kidney cells (CrFK).
- Assessment of epitope accessibility on native FIV envelope glycoproteins on infected cells.
Main Results:
- Antibodies against the V3 region neutralized both primary and lab-adapted FIV strains across different cell types.
- Significant discrepancies in neutralization efficiency were observed between PBMC and CrFK cells.
- Most B cell epitopes were poorly accessible on the surface of FIV-infected cells.
- Only the most accessible envelope domain was sensitive to neutralizing antibodies.
Conclusions:
- Antibody neutralization of FIV is influenced by the cellular substrate and viral adaptation.
- Epitope accessibility on the oligomeric envelope glycoprotein complex is a critical factor limiting neutralization by antibodies.
- Inaccessibility of epitopes may explain the reduced sensitivity of many lentivirus B cell epitopes to neutralization.
Abstract:
Antibodies elicited during natural infection of domestic cats by the feline immunodeficiency virus (FIV) recognize continuous epitopes in nine domains of the virus envelope glycoproteins. Whereas antibodies directed against the V3 envelope region can neutralize laboratory-adapted virus, neutralization of FIV has been shown to depend upon cellular substrate, and virus adaptation to laboratory cell lines may alter sensitivity to neutralizing antibodies. We therefore undertook a systematic analysis of the continuous B cell epitopes of the envelope of a primary FIV isolate, Wo. The capacity of feline antisera elicited against nine envelope domains to neutralize primary and laboratory-adapted virus was evaluated in feline peripheral blood mononuclear cells (PBMC). The laboratory-adapted strain Petaluma was used to compare neutralization in PBMC and Crandell feline kidney cells (CrFK). Antibodies specific for the V3 region neutralized both primary and laboratory-adapted virus whether residual infectivity was measured in CrFK or in feline PBMC. However, a large discrepancy in the efficiency of neutralization was observed in these ex vivo models of infection, perhaps reflecting diversity in the interaction between virus and different cellular targets. We also examined the accessibility of epitopes on the functional oligomeric envelope complex of FIV. Most of the epitopes were poorly exposed on native envelope glycoproteins at the surface of live infected cells. The most accessible domain was the only domain sensitive to neutralizing antibodies. These results suggest that inaccessibility on oligomeric envelope glycoproteins may frequently underlie the insensitivity of diverse lentivirus B cell epitopes to neutralization.
