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123 Selected Mutations to Remove the Potential N-Linked Glycosylation Sites at the V1-Loop of HIV-1 Envelope Glycoprotein Were Able to Induce Neutralizing Antibody Responses against the Primary HIV Isolate
S. Wang, I. Mboudjeka, S. Shen, T. Wu-Chou, T. Giehl, J. Brinker, and S. Lu*
Univ. of Massachusetts Med. Sch., Worcester, USA
Background: The overall goal of this study is to induce better anti-HIV neutralizing antibody responses by using partially deglycosylated Env antigens. Our previous data suggested that different primary Env clones had different levels of immunogenicity and that variations of glycosylation may have contributed to such a difference. Most strikingly, the levels of glycosylation within the V1 loop of these primary Env proteins are correlated to the length of V1 loop: the longer the V1 loop, the more the potential sites of N-linked glycosylation.
Methods: In the current study DNA vaccine plasmids were constructed to express the gp140 forms of modified HIV Env (GeneBank accession number U08451) of clade B primary HIV-1 isolate 92US715.6. This Env has a long V1 loop sequence with 7 potential N-linked glycosylation sites. Asn to Gln mutations were made to remove 3 of these N-linked glycosylation sites in the middle of the V1 loop. The expression of modified Env protein was confirmed in 293T cells. Animal sera were prepared by immunization of NZW rabbits with the wild-type and deglycosylated gp140 DNA vaccines.
Results: Both the wild-type and deglycosylated Env antigens were able to induce strong binding antibody responses against wild-type and modified Env antigens as shown by ELISA. Deglycosylated gp140 was slightly more immunogenic than the wild-type gp140. However, only deglycosylated Env induced neutralizing antibody against the autologous HIV 92US715. Our data confirm earlier SIV239 Env studies showing that glycosylation at the V1 region may help SIV escape from immune clearance.
Conclusions: Our data suggested that DNA vaccines expressing modified Env antigens may offer a novel opportunity to induce better neutralizing antibody responses against highly conformation-dependent HIV antigens.
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