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.
Trujillo
J D
JD
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA. jdt@vetmed.wsu.edu
Kumpula-McWhirter
N M
NM
Hötzel
K J
KJ
Gonzalez
M
M
Cheevers
W P
WP
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