Biodistribution and pharmacokinetics of111In-DTPA-labelled pegylated liposomes in a human tumour xenograft model: implications for novel targeting strategies

The biodistribution and pharmacokinetics of111In-DTPA-labelled pegylated liposomes in tumour-bearing nude mice was studied to examine possible applications of pegylated liposome-targeted anti-cancer therapies. Nude mice received an intravenous injection of 100 μl of111In-DTPA-labelled pegylated liposomes, containing 0.37–0.74 MBq of activity. The t 1/2α and t 1/2β of111In-DTPA-labelled pegylated liposomes were 1.1 and 10.3 h, respectively. Tumour uptake was maximal at 24 h at 5.5 ± 3.0% ID g–1. Significant reticuloendothelial system uptake was demonstrated with 19.3 ± 2.8 and 18.8 ± 4.2% ID g–1at 24 h in the liver and spleen, respectively. Other sites of appreciable deposition were the kidney, skin, female reproductive tract and to a lesser extent the gastrointestinal tract. There was no indication of cumulative deposition of pegylated liposomes in the lung, central nervous system, musculoskeletal system, heart or adrenal glands. In contrast, the t 1/2α and t 1/2β of unencapsulated111In-DTPA were 5 min and 1.1 h, respectively, with no evidence of accumulation in tumour or normal tissues. Incubation of111In-DTPA-labelled pegylated liposomes in human serum for up to 10 days confirmed that they are very stable, with only minor leakage of their contents. The potential applications of pegylated liposomes in the arena of targeted therapy of solid cancers are discussed. © 2000 Cancer Research Campaig

Influence of tumour size on uptake of111In-DTPA-labelled pegylated liposomes in a human tumour xenograft model

The relationship between tumour size and uptake of111In-DTPA-labelled pegylated liposomes has been examined in a human head and neck cancer xenograft model in nude mice. The mean tumour uptake of111In-labelled pegylated liposomes at 24 hours was 7.2 ± 6.6% ID/g. Liposome uptake for tumours < 0.1 g, 0.1–1.0 g and > 1.0 g was 15.1 ± 10.8, 5.9 ± 2.2 and 3.0 ± 1.3% ID/g, respectively. An inverse correlation between tumour weight and liposome uptake was observed by both Spearman’s rank correlation test (r s= – 0.573, P< 0.001) and Pearson’s correlation coefficient (r s= – 0.555, P< 0.001). For 18 tumours with macroscopic central necrosis, the ratio of uptake in the tumour rim relative to the necrotic tumour core was 11.2 ± 6.4. Measurement of tumour vascular volume for tumours of various sizes revealed an inverse correlation between tumour weight and tumour vascular volume (Spearman’s rank correlation test, r s= – 0.598, P< 0.001), consistent with poor or heterogeneous vascularization of larger tumours. These data have important implications for the clinical application of pegylated liposome targeted strategies for solid cancers which are discussed in detail. © 2000 Cancer Research Campaig

Cationic polyelectrolytes: A new look at their possible roles as opsonins, as stimulators of respiratory burst in leukocytes, in bacteriolysis, and as modulators of immune-complex diseases (A review hypothesis)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44497/1/10753_2004_Article_BF00915991.pd

Author Correction: Uncoupling of invasive bacterial mucosal immunogenicity from pathogenicity.

ISSN:2041-172

Uncoupling of invasive bacterial mucosal immunogenicity from pathogenicity.

There is the notion that infection with a virulent intestinal pathogen induces generally stronger mucosal adaptive immunity than the exposure to an avirulent strain. Whether the associated mucosal inflammation is important or redundant for effective induction of immunity is, however, still unclear. Here we use a model of auxotrophic Salmonella infection in germ-free mice to show that live bacterial virulence factor-driven immunogenicity can be uncoupled from inflammatory pathogenicity. Although live auxotrophic Salmonella no longer causes inflammation, its mucosal virulence factors remain the main drivers of protective mucosal immunity; virulence factor-deficient, like killed, bacteria show reduced efficacy. Assessing the involvement of innate pathogen sensing mechanisms, we show MYD88/TRIF, Caspase-1/Caspase-11 inflammasome, and NOD1/NOD2 nodosome signaling to be individually redundant. In colonized animals we show that microbiota metabolite cross-feeding may recover intestinal luminal colonization but not pathogenicity. Consequent immunoglobulin A immunity and microbial niche competition synergistically protect against Salmonella wild-type infection

Innate immunity restricts <i>Citrobacter rodentium</i> A/E pathogenesis initiation to an early window of opportunity

<div><p><i>Citrobacter rodentium</i> infection is a mouse model for the important human diarrheal infection caused by enteropathogenic <i>E</i>. <i>coli</i> (EPEC). The pathogenesis of both species is very similar and depends on their unique ability to form intimately epithelium-adherent microcolonies, also known as “attachment/effacement” (A/E) lesions. These microcolonies must be dynamic and able to self-renew by continuous re-infection of the rapidly regenerating epithelium. It is unknown whether sustained epithelial A/E lesion pathogenesis is achieved through re-infection by planktonic bacteria from the luminal compartment or local spread of sessile bacteria without a planktonic phase. Focusing on the earliest events as <i>C</i>. <i>rodentium</i> becomes established, we show here that all colonic epithelial A/E microcolonies are clonal bacterial populations, and thus depend on local clonal growth to persist. In wild-type mice, microcolonies are established exclusively within the first 18 hours of infection. These early events shape the ongoing intestinal geography and severity of infection despite the continuous presence of phenotypically virulent luminal bacteria. Mechanistically, induced resistance to A/E lesion de-novo formation is mediated by TLR-MyD88/Trif-dependent signaling and is induced specifically by virulent <i>C</i>. <i>rodentium</i> in a virulence gene-dependent manner. Our data demonstrate that the establishment phase of <i>C</i>. <i>rodentium</i> pathogenesis <i>in vivo</i> is restricted to a very short window of opportunity that determines both disease geography and severity.</p></div

Dynamics of <i>Citrobacter rodentium</i> infection in SPF and germ-free wild-type mice.

<p>(<b>A</b>) Schematic of possible routes of epithelial infection shaping A/E lesion development and renewal in the face of continuous epithelial regeneration. Black arrows indicate direction of epithelial cell migration and luminal exfoliation. Green arrows indicate possible routes of bacterial infection, with or without luminal planktonic stage. (<b>B-D</b>) Luminal colonization quantitated by bacterial plating from feces of SPF mice (panel B; n = 12–21 per group and time point) and germ-free mice (panel C; n = 3–15 per group and time point) following inoculation with 10¹⁰ (red squares) and 10⁴ (blue circles) CFU/mouse, respectively. (D) Early colonization in mice (n = 4 per group) sampled every hour during the first 12 hours after gavage. Fitted exponential curves were used to extrapolate the time to reach levels of 2.5x10⁹ CFU/g in the animals inoculated with 10⁴ CFU. The average of these 4 values is represented by the vertical dotted line (at 15.5 h). (<b>E-H</b>) Representative fluorescent microscopy images of distal colon cross sections of SPF (E and G) and germ-free (F and H) mice infected with 10¹⁰ (E and F) and 10⁴ (G and H) CFU/mouse of <i>C</i>. <i>rodentium</i> analyzed on day 7 post infection. All individual mice depicted were infected with a 1:1 mixture of bacteria carrying a mCherry (red) or GFP (green) fluorescent protein expression plasmid. Grey, F-actin stained with phalloidin; green, GFP-expressing <i>C</i>. <i>rodentium</i>; red, mCherry-expressing <i>C</i>. <i>rodentium</i>. Inset indicates area shown in higher magnification panel. Scale bars: 100 μm. (<b>I</b>) Numbers of A/E microcolonies in the distal colon of SPF mice infected with either 10⁴ (blue circles) or 10¹⁰ (red squares) CFU of <i>C</i>. <i>rodentium</i> quantified over a time course of 10 days (n = 3–6 per group and time point, data pooled from 2 independent experiments). Connecting lines indicate means. (<b>J</b>) Numbers of A/E microcolonies in the distal colon of germ-free mice infected with either 10⁴ (blue circles) or 10¹⁰ (red squares) CFU of <i>C</i>. <i>rodentium</i> quantified over a time course of 22 days (n = 2–6 per group and time point, data pooled from 3 independent experiments). Connecting lines connect means; horizontal dotted lines indicate detection limit; ****, p < 0.0001 (Student`s t-test); F-test, Fisher’s test.</p