Synergistic Inhibition of R5 HIV-1 by the Fusion Protein (FLSC) IgG1 Fc and Maraviroc in Primary Cells: Implications for Prevention and Treatment.
BACKGROUND
Antiretroviral (ARV) drugs targeting retroviral enzymes have been extensively employed to treat HIV-1 infection. Drawbacks of this approach include cost, toxicity, and the eventual emergence of resistant strains that threaten prophylactic and/or therapeutic efficacy. Accordingly, efforts to develop next-generation ARV approaches are warranted, particularly if they can offer a higher threshold of resistance. We have previously shown that FLSC, a fusion protein containing gp120(BAL) and the D1 and D2 domains of human CD4, specifically binds CCR5, an important cellular co-receptor, and inhibits the entry of R5 HIV isolates. (FLSC) IgG1, a fusion of FLSC and the hinge-C(H)2-C(H)3 region of human IgG1, has an increased antiviral activity, likely due to the resultant bivalency.


METHODS
In this study, we show CCR5 reduction upon (FLSC) IgG1 treatment both by standard flow cytometry and visualized using a novel nanoparticle method. A β-lactamase virus-cell fusion assay was used to quantify (FLSC) IgG1 inhibition of HIV-1 entry into both cell lines and primary cells. Synergistic anti-viral activities of (FLSC) IgG1 and MVC in primary cells were evaluated by measuring supernatant p24 levels via ELISA and calculated using the MacSynergy™ II program.


RESULTS
We previously reported that treatment with the CCR5 small molecule antagonist Maraviroc (MVC) increased the apparent exposure of the (FLSC) IgG1 binding sites on CCR5, leading us to wonder if the two compounds used in combination might synergize in their anti-viral activity. Here we show that this is indeed the case. We demonstrate that fusion protein (FLSC) IgG1, strongly synergizes with the CCR5 antagonist Maraviroc to successfully inhibit both MVC-sensitive and MVC-resistant R5 HIV-1.


CONCLUSIONS
Observed synergy between (FLSC) IgG1 and MVC was high in both, cell lines and primary PBMCs. This has relevance for future in vivo studies. In addition, synergy occurred both with MVC-sensitive viruses and MVC-resistant viruses, partially restoring the inhibitory effect of MVC. These findings suggest that a combinatorial treatment based on these two compounds has potential merit and that future in vivo studies are warranted.
Institute of Human Virology, University of Maryland School of Medicine, 725 W. Lombard St., Baltimore, MD 21201, USA. olatinovic@ihv.umaryland.edu.
Olga S
OS
Latinovic
Jian
J
Zhang
Yutaka
Y
Tagaya
Anthony L
AL
DeVico
Timothy R
TR
Fouts
K
K
Schneider
Joseph R
JR
Lakowicz
Alonso
A
Heredia
Robert R
RR
Redfield
D019380:Anti-HIV Agents / Q000627:therapeutic use*; D065100:CCR5 Receptor Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D002460:Cell Line; D003510:Cyclohexanes / Q000494:pharmacology* / Q000627:therapeutic use; D004357:Drug Synergism; D005434:Flow Cytometry; D015658:HIV Infections / Q000188:drug therapy* / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects*; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000494:pharmacology*; D000077592:Maraviroc; D019713:Receptors, CCR5 / Q000187:drug effects* / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology* / Q000627:therapeutic use; D053586:Virus Internalization / Q000187:drug effects
D019380:Anti-HIV Agents; D065100:CCR5 Receptor Antagonists; C584933:CCR5 protein, human; C527276:CXCR4 protein, human; D003510:Cyclohexanes; D007074:Immunoglobulin G; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D011993:Recombinant Fusion Proteins; D014230:Triazoles; D000077592:Maraviroc