Glycosylation of immunodominant linear epitopes in the carboxy-terminal region of the caprine arthritis-encephalitis virus surface envelope enhances vaccine-induced type-specific and cross-reactive neutralizing antibody responses.
This study evaluated type-specific and cross-reactive neutralizing antibodies induced by immunization with modified surface glycoproteins (SU) of the 63 isolate of caprine arthritis-encephalitis lentivirus (CAEV-63). Epitope mapping of sera from CAEV-infected goats localized immunodominant linear epitopes in the carboxy terminus of SU. Two modified SU (SU-M and SU-T) and wild-type CAEV-63 SU (SU-W) were produced in vaccinia virus and utilized to evaluate the effects of glycosylation or the deletion of immunodominant linear epitopes on neutralizing antibody responses induced by immunization. SU-M contained two N-linked glycosylation sites inserted into the target epitopes by R539S and E542N mutations. SU-T was truncated at 518A, upstream from the target epitopes, by introduction of termination codons at 519Y and 521Y. Six yearling Saanen goats were immunized subcutaneously with 30 microg of SU-W, SU-M, or SU-T in Quil A adjuvant and boosted at 3, 7, and 16 weeks. SU antibody titers determined by indirect enzyme-linked immunosorbent assay demonstrated anamnestic responses after each boost. Wild-type and modified SU-induced type-specific CAEV-63 neutralizing antibodies and cross-reactive neutralizing antibodies against CAEV-Co, a virus isolate closely related to CAEV-63, and CAEV-1g5, an isolate geographically distinct from CAEV-63, were determined. Immunization with SU-T resulted in altered recognition of SU linear epitopes and a 2.8- to 4.6-fold decrease in neutralizing antibody titers against CAEV-63, CAEV-Co, and CAEV-1g5 compared to titers of SU-W-immunized goats. In contrast, immunization with SU-M resulted in reduced recognition of glycosylated epitopes and a 2.4- to 2.7-fold increase in neutralizing antibody titers compared to titers of SU-W-immunized goats. Thus, the glycosylation of linear immunodominant nonneutralization epitopes, but not epitope deletion, is an effective strategy to enhance neutralizing antibody responses by immunization.
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA. jdt@vetmed.wsu.edu
J D
JD
Trujillo
N M
NM
Kumpula-McWhirter
K J
KJ
Hötzel
M
M
Gonzalez
W P
WP
Cheevers
D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology*; D000918:Antibody Specificity / Q000276:immunology; D016088:Arthritis-Encephalitis Virus, Caprine / Q000276:immunology*; D015153:Blotting, Western; D003429:Cross Reactions / Q000276:immunology; D006031:Glycosylation; D006041:Goats / Q000276:immunology / Q000821:virology; D016056:Immunodominant Epitopes / Q000737:chemistry* / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000276:immunology; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000276:immunology*; D014765:Viral Vaccines / Q000097:blood / Q000276:immunology*
D000914:Antibodies, Viral; D016056:Immunodominant Epitopes; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D014765:Viral Vaccines