On the adhesion of particles to a cell layer under flow

The non-specific adhesion of spherical particles to a cell substrate is analyzed in a parallel plate flow chamber, addressing the effect of the particle size. Differently from other experiments, the total volume of the injected particles has been fixed, rather than the total number of particles, as the diameter d of the particles is changed from 500 nm up to 10 $\mu$m. From the analysis of the experimental data, simple and instructive scaling adhesion laws have been derived showing that (i) the number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d^(-1.7) ; and consequently (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d^(+1.3). These results are of importance in the "rational design" of nanoparticles for drug delivery and biomedical imaging.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Flow chamber analysis of size effects in the adhesion of spherical particles

The non-specific adhesion of spherical micro- and nano-particles to a cell substrate is investigated in a parallel plate flow chamber. Differently from prior in-vitro analyses, the total volume of the particles injected into the flow chamber is kept fixed whilst the particle diameter is changed in the range 0.5–10 μm. It is shown that: (i) the absolute number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d−1.7; (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d+1.3. From these results and considering solely non-specific particles, the following hypothesis are generated (i) use the smallest possible particles in biomedical imaging and (ii) use the largest possible particles in drug delivery

On the adhesion of particles to a cell layer under flow

Bioadhesion, nanoparticles, intravascular deliveryThe non-specific adhesion of spherical particles to a cell substrate is analyzed in a parallel plate flow chamber, addressing the effect of the particle size. Differently from other experiments, the total volume of the injected particles has been fixed, rather than the total number of particles, as the diameter d of the particles is changed from 500 nm up to 10 ìm. From the analysis of the experimental data, simple and instructive scaling adhesion laws have been derived showing that (i) the number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d^(-1.7) ; and consequently (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d^(+1.3). These results are of importance in the ‘rational design’ of nanoparticles for drug delivery and biomedical imaging

Safety and efficacy of anti-PD-L1 therapy in the woodchuck model of HBV infection

<div><p>Immune clearance of Hepatitis B virus (HBV) is characterized by broad and robust antiviral T cell responses, while virus-specific T cells in chronic hepatitis B (CHB) are rare and exhibit immune exhaustion that includes programmed-death-1 (PD-1) expression on virus-specific T cells. Thus, an immunotherapy able to expand and activate virus-specific T cells may have therapeutic benefit for CHB patients. Like HBV-infected patients, woodchucks infected with woodchuck hepatitis virus (WHV) can have increased hepatic expression of PD-1-ligand-1 (PD-L1), increased PD-1 on CD8+ T cells, and a limited number of virus-specific T cells with substantial individual variation in these parameters. We used woodchucks infected with WHV to assess the safety and efficacy of anti-PD-L1 monoclonal antibody therapy (αPD-L1) in a variety of WHV infection states. Experimentally-infected animals lacked PD-1 or PD-L1 upregulation compared to uninfected controls, and accordingly, αPD-L1 treatment in lab-infected animals had limited antiviral effects. In contrast, animals with naturally acquired WHV infections displayed elevated PD-1 and PD-L1. In these same animals, combination therapy with αPD-L1 and entecavir (ETV) improved control of viremia and antigenemia compared to ETV treatment alone, but with efficacy restricted to a minority of animals. Pre-treatment WHV surface antigen (sAg) level was identified as a statistically significant predictor of treatment response, while PD-1 expression on peripheral CD8+ T cells, T cell production of interferon gamma (IFN-γ) upon in vitro antigen stimulation (WHV ELISPOT), and circulating levels of liver enzymes were not. To further assess the safety of this strategy, αPD-L1 was tested in acute WHV infection to model the risk of liver damage when the extent of hepatic infection and antiviral immune responses were expected to be the greatest. No significant increase in serum markers of hepatic injury was observed over those in infected, untreated control animals. These data support a positive benefit/risk assessment for blockade of the PD-1:PD-L1 pathway in CHB patients and may help to identify patient groups most likely to benefit from treatment. Furthermore, the efficacy of αPD-L1 in only a minority of animals, as observed here, suggests that additional agents may be needed to achieve a more robust and consistent response leading to full sAg loss and durable responses through anti-sAg antibody seroconversion.</p></div

In vitro inhibitory activity of wc6D5.

<p>In vitro inhibitory activity of wc6D5.</p

Study design for evaluation of αPD-L1 (15mg/kg) PLUS ETV (0.1 mg/kg/day) in naturally chronically-infected woodchucks.

<p>Study design for evaluation of αPD-L1 (15mg/kg) PLUS ETV (0.1 mg/kg/day) in naturally chronically-infected woodchucks.</p

Antiviral effects of αPD-L1 in naturally infected, ETV-treated woodchucks.

<p>(A) Plasma sAg, (B) viral loads, and (C) eAg in animals receiving ETV plus isotype control antibody (left panel A-C) and ETV plus αPD-L1 antibody (right panel A-C). Controls are shown in red. αPD-L1 treatment responders are in green; αPD-L1 non-responders (define) are in blue. Horizontal axes indicate limits of detection in all plots: 500 copies/ml for viral load, 20 ng/ml for sAg, and 0.5 ng/ml for eAg. (D) Plasma AST and ALT values in treatment-responding animals 7095, 7254, and 7802. (E) ALT values in control animals and non-responder animals treated with αPD-L1.</p

Safety of αPD-L1 in acute WHV infection.

<p>(A) Group geometric mean viral loads in acutely infected woodchucks treated with αPD-L1 at 1 or 15 mg/kg on days 49, 52, 56, and 59. No statistically significant differences were noted. (B) ALT and (C) AST values in acutely infected woodchucks with and without anti-PD-L1. Colors match the groups shown in (A).</p

Viral and immune parameters in WHV+ cohorts.

<p>(A) pre-treatment PD-1 expression on CD8 cells (CD3+CD4-) in animals from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0190058#pone.0190058.g001" target="_blank">Fig 1</a>, compared to uninfected woodchucks (n = 52), a separate cohort of chronic WHV+ animals infected via 10⁷ genome equivalent inoculation neonatally (n = 27), or chronic WHV+ animals infected naturally (n = 24). (B) Viral load in lab-infected and naturally-infected chronic WHV+ animals. (C) sAg in lab-infected versus naturally-infected chronic WHV+ animals. (D) Representative images of liver immunohistochemistry for CD3 (left column), PD-L1 (middle column), and MAC2 (right column) from uninfected (top row), lab infected (middle row) and naturally infected (bottom row) animals. (E) Quantification of CD3, PD-L1 and MAC2 staining in 6mm liver punch biopsies from uninfected (n = 9), lab-infected (n = 7), and naturally-infected (n = 20) woodchucks. All statistical comparisons were performed with two-sided Mann-Whitney test. *, p<0.05, **, p<0.001. In A-C and E, each point represents an individual animal, with horizontal bars indicating group means in (A) and (E) geometric means in (B) and (C).</p