A Chimeric HIV-1 Envelope Glycoprotein Trimer with an Embedded Granulocyte-Macrophage Colony-stimulating Factor (GM-CSF) Domain Induces Enhanced Antibody and T Cell Responses

Thijs Van Montfort,Mark Melchers,Gözde Isik,Sergey Menis,Po-Ssu Huang,Katie Matthews,Elizabeth Michael,Ben Berkhout,William R Schief,John P Moore,Rogier W Sanders

doi:10.1074/jbc.m111.229625

Thijs Van Montfort, Mark Melchers + Show 9 more

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https://doi.org/10.1074/jbc.m111.229625

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An effective HIV-1 vaccine should ideally induce strong humoral and cellular immune responses that provide sterilizing immunity over a prolonged period. Current HIV-1 vaccines have failed in inducing such immunity. The viral envelope glycoprotein complex (Env) can be targeted by neutralizing antibodies to block infection, but several Env properties limit the ability to induce an antibody response of sufficient quantity and quality. We hypothesized that Env immunogenicity could be improved by embedding an immunostimulatory protein domain within its sequence. A stabilized Env trimer was therefore engineered with the granulocyte-macrophage colony-stimulating factor (GM-CSF) inserted into the V1V2 domain of gp120. Probing with neutralizing antibodies showed that both the Env and GM-CSF components of the chimeric protein were folded correctly. Furthermore, the embedded GM-CSF domain was functional as a cytokine in vitro. Mouse immunization studies demonstrated that chimeric Env(GM-CSF) enhanced Env-specific antibody and T cell responses compared with wild-type Env. Collectively, these results show that targeting and activation of immune cells using engineered cytokine domains within the protein can improve the immunogenicity of Env subunit vaccines.

Highlights

Design of an HIV-1 envelope glycoprotein complex (Env) Trimer with an Embedded granulocyte-macrophage colony-stimulating factor (GM-CSF) Domain—To generate a trimeric HIV-1 Env immunogen that could be targeted to immune cells and simultaneously stimulate immune activation, we deleted the V1V2 domain of gp120 and replaced it with almost the complete sequence of the GM-CSF cytokine
The mouse or human GM-CSF sequence was inserted after the second cysteine bridge in the V1V2 stem between amino acids 127 and 195
To improve the immunogenicity of HIV-1 Env vaccines, we constructed a chimeric gp140 trimer in which the V1V2 region of gp120 was replaced by the GM-CSF cytokine

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The abbreviations used are

Envelope glycoprotein complex; Ab, antibody(ies); nAb, neutralizing antibody(ies); HIV, human immunodeficiency virus; SHIV, simian-human immunodeficiency virus; GMR, GM-CSF receptor; BAFF, B cell activation factor; rhGM-CSF, recombinant human GM-CSF; CD4i, CD4-induced; bis-Tris, 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol. One immune molecule that can serve as an adjuvant in vaccines is the granulocyte-macrophage colony-stimulating factor (GM-CSF). This cytokine is produced by fibroblasts, activated T lymphocytes, macrophages, and tumor, endothelial, mesothelial, and epithelial cells and functions as a hematopoietic growth factor. Signaling is mediated by the formation of a hexameric complex consisting of two GM-CSF molecules and the four receptor subunits. Two of these GMCSF-GMR hexamers can dimerize to form a dodecameric complex. We investigated whether GM-CSF embedded within the HIV-1 trimeric gp140 can augment Env-specific immune responses. Embedding the cytokine domains is useful for enhancing the immunogenicity of HIV-1 Env-based vaccines

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