Original Article
Time-controlled phagocytosis of asymmetric liposomes: Application to phosphatidylserine immunoliposomes binding HIV-1 virus-like particles

https://doi.org/10.1016/j.nano.2015.06.004Get rights and content

Abstract

Macrophage immune functions such as antibody-mediated phagocytosis are strongly impaired in individuals affected by HIV-1. Nevertheless, infected macrophages are still able to phagocytose apoptotic cells. For this reason, we recently developed antibody-decorated phosphatidylserine (PS)-containing liposomes that bind HIV-1 virus-like particles and, by mimicking apoptotic cells, are efficiently internalized by macrophages. In the context of an in vivo application, it would be extremely important to initially protect immunoliposomes from macrophages, in order to provide enough time to redistribute through the body and achieve maximum virus binding. To this end, we have designed asymmetric immunoliposomes in which the PS is initially confined to the inner leaflet and thus cannot be recognized by macrophages. Spontaneous PS flip-flop to the outer surface leads to a time-delay in internalization by macrophages in vitro. Such a delay can be fine-tuned by altering the molecular composition of the immunoliposomes.

From the Clinical Editor

In the fight against HIV-1, macrophage plays an important role. Ironically, the phagocytic functions of these cells are often impaired by HIV-1. In this interesting article, the authors described the development of asymmetric liposomes, which would bind HIV-1 with prolonged systemic circulation, such that the clearance of virus by macrophages is enhanced. This system represents a promising effective approach to utilize the phagocytic capability of macrophages.

Graphical Abstract

We present a novel asymmetric immunoliposomal system that is able to bind a surface protein of HIV-1. The structural lipid asymmetry (i.e., the lipid phosphatidylserine confined to the inner leaflet) allows the evasion of the immune system long enough to locate and bind the pathogen of interest. After a certain amount of time (e.g., 24 hours), phosphatidylserine will be exposed in the outer leaflet and trigger internalization and disposal of the liposome–pathogen complex by macrophages.

  1. Download : Download high-res image (153KB)
  2. Download : Download full-size image

Section snippets

Methods

See Supplementary Materials.

Fast internalization of symmetric immunoliposomes hinders binding to VLPs

We have previously shown that αEnv-PS-LUVs can bind Env proteins on the VLPs surface and, due to the presence of PS, are promptly phagocytosed by macrophages, together with the bound VLPs.7 Due to the strong interaction between PS-LUVs and macrophages, in our previous work, we let αEnv-PS-LUVs interact with VLPs before the actual measurements. This expedient allowed the binding between liposomes and VLPs to take place in the absence of macrophages, in order to simplify the interpretation of the

Discussion

We have recently described PS-containing LUVs decorated with αEnv antibodies as an approach that could be used to elicit HIV-1 phagocytosis by macrophages in vivo.7 αEnv-PS-LUVs are recognized as apoptotic cells due to the presence of PS8 and are efficiently internalized by macrophages together with previously bound viral particles.7

PS-LUVs (30 mol% PS) are internalized as much as 10 times more efficiently than those without PS.7 This observation suggested a specific recognition of PS by

References (24)

  • A. Filippov et al.

    Sphingomyelin structure influences the lateral diffusion and raft formation in lipid bilayers

    Biophys J

    (2006)
  • P. Iyidogan et al.

    Current perspectives on HIV-1 antiretroviral drug resistance

    Viruses

    (2014)
  • Cited by (10)

    • Liposome-polymer complex for drug delivery system and vaccine stabilization

      2022, Heliyon
      Citation Excerpt :

      A number of surface-functionalized liposomal carrier systems, known as immunoliposomes, have been shown to navigate themselves to pathological cells due to the specific interaction among antibodies that has been attached to the surface of the liposomes and antigen epitopes or small particles that are displayed by the targeted pathogenic cells. Such types of immuneliposomal carriers having the tendency to mimicking the apoptotic cells as a result efficiently internalized by macrophages [227, 228, 229, 230]. For example, recombinant B subunit of cholera toxin (rCTB) was covalently coupled to the outer surface of the small unilamellar liposomes for targeted delivery of encapsulated saliva-binding region (SBR) of Streptococcus mutans antigen I/II (AgI/II) protein to Peyer's patches (aggregated lymphoid nodules) and enhanced the secretory IgA responses in mice.

    • When liposomes met antibodies: Drug delivery and beyond

      2020, Advanced Drug Delivery Reviews
      Citation Excerpt :

      In addition, Woll et al. reported a chemoenzymatic method based on Sortase-A mediated transpeptidation [53]. Non-covalent attachments based on biotin and avidin interactions [54–57] or through a bispecific PEG-engager [58] were also listed. There have been only a few studies that compared the different conjugated structures.

    • Liposomes used as a vaccine adjuvant-delivery system: From basics to clinical immunization

      2019, Journal of Controlled Release
      Citation Excerpt :

      In another study, PS liposomes were demonstrated capable of promoting APC uptake of their carried Ags, as a result of liposome binding to PS-specific receptors on APCs. This conclusion was reinforced by the work from Chiantia's group, which showed that the anti-HIV Env Ab-decorated PS liposomes were bound by HIV VLPs (virus-like particles), which were facilitated, for MP internalization, in a liposome PS-dependent manner [101]. Summarily, PS-containing liposomes are reported by different groups to show complicated, even conflicting, immunostimulatory activities.

    • Enhancement of macrophage uptake via phosphatidylserine-coated acetalated dextran nanoparticles

      2019, Journal of Drug Delivery Science and Technology
      Citation Excerpt :

      The presence of DPPS on the cellular surface is known to cause an “eat-me” signal in cells that are transitioning toward an apoptotic state, causing macrophages to identify and phagocytose the dying cells [1–3,7,11]. Therefore, in terms of recognition, the DPPS coating on the Ac-Dex NP was identified by the macrophages, which produced the necessary phagocytotic action, resulting in cellular uptake of the particles [1,6,7,16,25,27]. In most cases, apoptosis is initiated by the presence DPPS and other signaling pathways such as receptor-ligand interactions or identification of PS binding proteins produced by phagocytes.

    • The current perspectives of nanoparticles in cellular and organ-specific drug targeting in biological system

      2018, Nanostructures for the Engineering of Cells, Tissues and Organs: From Design to Applications
    • Immunoliposomes: A review on functionalization strategies and targets for drug delivery

      2017, Colloids and Surfaces B: Biointerfaces
      Citation Excerpt :

      Also, liposomes bearing Fab’ portions were 2.3-fold less immunogenic than liposomes bearing the entire IgG [58]. In another approach, phosphatidylserine immunoliposomes targeted with antibodies that bind HIV-1 virus-like particles were initially protected from macrophage uptake, in order to provide enough time to circulate through the body and achieve maximum virus binding [128]. Moreover, anti-CD4 conjugated immunoliposomes containing 2 antiretroviral drugs (nevirapine and saquinavir) inhibited viral proliferation at a lower concentration than free drugs [41].

    View all citing articles on Scopus

    S.C. is financed by DFG Grant CH1238/3-1.

    The authors declare no competing financial interests.

    An abstract regarding some of the results described in the manuscript was presented at the Biophysical Society Meeting 2014.

    View full text