eCD4-Ig is a potent and exceptionally broad fusion of the first two domains of CD4 to an antibody Fc domain and a short tyrosine-sulfated coreceptor-mimetic peptide. In rhesus macaques, adeno-associated virus (AAV)-expressed eCD4-Ig mediates consistent and very effective long-term protection against SHIV- AD8 and SIVmac239. eCD4-Ig also has properties that make it especially useful for establishing a functional cure in rhesus macaques and perhaps in humans. These include its potency, breadth, difficulty- of-escape, low immunogenicity when expressed by AAV, consistent expression by AAV, potent intrinsic ADCC activity, and collaboration with serum antibodies to mediate ADCC. These properties allow eCD4- Ig to circumvent two major problems associated with using AAV-expressed antibodies to establish functional cures, namely immune clearance and viral escape. In the forthcoming award period, we will improve the technologies allowing AAV-mediated delivery of eCD4-Ig by optimizing its expression as an AAV transgene, by eliminating residual antibody responses to AAV-delivered eCD4-Ig, and by assessing the role of the eCD4-Ig Fc domain in anti-eCD4-Ig antibody responses and in control an established SIVmac239 infection. These efforts will develop technologies that can be applied to the ongoing efforts by many laboratories to prevent new infections, to provide long- acting alternatives to combined antiretroviral therapies, and to reduce the scale of the viral reservoir.

Public Health Relevance

eCD4-Ig is a potent and exceptionally broad HIV-1 and SIV entry inhibitor that, when delivered by an AAV vector, provides rhesus macaques robust long-term protection from new infections, and by itself suppresses viral replication in the absence of anti-retroviral therapies. Here we seek to optimize and better understand these properties of AAV-delivered eCD4-Ig.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (NSS)
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Conley, Tony J
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Scripps Florida
United States
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Fetzer, Ina; Gardner, Matthew R; Davis-Gardner, Meredith E et al. (2018) eCD4-Ig Variants That More Potently Neutralize HIV-1. J Virol 92:
Otsuka, Yuka; Schmitt, Kimberly; Quinlan, Brian D et al. (2018) Diverse pathways of escape from all well-characterized VRC01-class broadly neutralizing HIV-1 antibodies. PLoS Pathog 14:e1007238
Mou, Huihui; Zhong, Guocai; Gardner, Matthew R et al. (2018) Conditional Regulation of Gene Expression by Ligand-Induced Occlusion of a MicroRNA Target Sequence. Mol Ther 26:1277-1286
Fellinger, Christoph H; Gardner, Matthew R; Bailey, Charles C et al. (2017) Simian Immunodeficiency Virus SIVmac239, but Not SIVmac316, Binds and Utilizes Human CD4 More Efficiently than Rhesus CD4. J Virol 91:
Gardner, Matthew R; Farzan, Michael (2017) Engineering antibody-like inhibitors to prevent and treat HIV-1 infection. Curr Opin HIV AIDS :
Zhong, Guocai; Wang, Haimin; Li, Yujun et al. (2017) Cpf1 proteins excise CRISPR RNAs from mRNA transcripts in mammalian cells. Nat Chem Biol 13:839-841
Zhong, Guocai; Wang, Haimin; Bailey, Charles C et al. (2016) Rational design of aptazyme riboswitches for efficient control of gene expression in mammalian cells. Elife 5:
Gardner, Matthew R; Fellinger, Christoph H; Prasad, Neha R et al. (2016) CD4-Induced Antibodies Promote Association of the HIV-1 Envelope Glycoprotein with CD4-Binding Site Antibodies. J Virol 90:7822-32