Antibody Response in Cats to the Envelope Proteins of Feline Immunodeficiency Virus: Identification of an Immunodominant Neutralization Domain

Abstract

Overlapping fragments of the envelope protein of feline immunodeficiency virus (FIV) have been expressed in Escherichia coli. Screening of cat sera for antibodies to these fragments revealed that the immunodominant domain of the FIV envelope is localized within the transmembrane protein (amino acids 687-741) and that both the variable region 3 (SU3, aa 385-417) and the COOH-terminus (aa 599-611) of the surface protein (SU) are highly immunogenic. Of all rabbit sera raised to the envelope protein fragments only the serum directed to SU3 was neutralizing. Both FIV-infected and SU3-immunized cats elicited neutralizing antibodies to SU3. Neutralizing antibodies in sera of infected cats could be absorbed by SU3, showing that SU3 is a major neutralization domain of FIV.

Neutralization sensitivity and accessibility of continuous B cell epitopes of the feline immunodeficiency virus envelope

“…This domain, SU2, is located in the V3 region of the SU glycoprotein, which has previously been shown to be sensitive to neutralizing antibodies, as assessed with laboratory-adapted strains during infection of CrFK fibroblasts (Lombardi et al, 1993;de Ronde et al, 1994) but not a lymphoid cell line (Lombardi et al, 1995). We confirm and extend these results in demonstrating that antibodies directed against this region also neutralize the infectivity of primary virus for a more natural cellular target, activated feline PBMC.…”

Monoclonal antibodies to immunodominant and neutralizing domains of the envelope surface protein of feline immunodeficiency virus

“…Interestingly, binding of the neutralizing monoclonal 1El was inhibited by a rabbit serum specific for SU3. This rabbit serum also neutralizes FIV-UTll3 (Table 1; De Ronde et al, 1994). These results indicate that at least part of the epitope is located on this SU3 domain and suggest that the SU3 domain contains neutralizing antibody-inducing epitopes.…”

“…These results indicate that at least part of the epitope is located on this SU3 domain and suggest that the SU3 domain contains neutralizing antibody-inducing epitopes. Recently, both linear and conformational neutralization epitopes have been located in this region (Lombardi et al, 1993 ;De Ronde et al, 1994). However, inhibition of binding of 1El due to steric hindrance or by a change in conformation of the epitope cannot be completely ruled out.…”

Antibodies specific for hypervariable regions 3 to 5 of the feline immunodeficiency virus envelope glycoprotein are not solely responsible for vaccine-induced acceleration of challenge infection in cats

“…Polyclonal rabbit sera raised against bacterial fusion proteins were used to characterize and identify the produced envelope proteins; serum Ra2194 recognized HV4 and serum Ra2279 recognized epitopes located between HV2 and HV3 (de Ronde et al, 1994).…”