PEGylated nanoparticles interact with macrophages independently of immune response factors and trigger a non-phagocytic, low-inflammatory response.

Poly-ethylene-glycol (PEG)-based nanoparticles (NPs) - including cylindrical micelles (CNPs), spherical micelles (SNPs), and PEGylated liposomes (PLs) - are hypothesized to be cleared in vivo by opsonization followed by liver macrophage phagocytosis. This hypothesis has been used to explain the rapid and significant localization of NPs to the liver after administration into the mammalian vasculature. Here, we show that the opsonization-phagocytosis nexus is not the major factor driving PEG-NP - macrophage interactions. First, mouse and human blood proteins had insignificant affinity for PEG-NPs. Second, PEG-NPs bound macrophages in the absence of serum proteins. Third, lipoproteins blocked PEG-NP binding to macrophages. Because of these findings, we tested the postulate that PEG-NPs bind (apo)lipoprotein receptors. Indeed, PEG-NPs triggered an in vitro macrophage transcription program that was similar to that triggered by lipoproteins and different from that triggered by lipopolysaccharide (LPS) and group A Streptococcus. Unlike LPS and pathogens, PLs did not increase transcripts involved in phagocytosis or inflammation. High-density lipoprotein (HDL) and SNPs triggered remarkably similar mouse bone-marrow-derived macrophage transcription programs. Unlike opsonized pathogens, CNPs, SNPs, and PLs lowered macrophage autophagosome levels and either reduced or did not increase the secretion of key macrophage pro-inflammatory cytokines and chemokines. Thus, the sequential opsonization and phagocytosis process is likely a minor aspect of PEG-NP - macrophage interactions. Instead, PEG-NP interactions with (apo)lipoprotein and scavenger receptors appear to be a strong driving force for PEG-NP - macrophage binding, entry, and downstream effects. We hypothesize that the high presence of these receptors on liver macrophages and on liver sinusoidal endothelial cells is the reason PEG-NPs localize rapidly and strongly to the liver.

MILK Symposium review: Community-tailored training to improve the knowledge, attitudes, and practices of women regarding hygienic milk production and handling in Borana pastoral area of southern Ethiopia.

Milk and milk products are essential in the diets of the Borana pastoral community in Ethiopia. Traditional handling and processing of dairy products using basic equipment and infrastructure coupled with a preference for raw milk consumption pose potential health risks to consumers. We tested the effect of an intervention designed to improve the hygienic handling and safe consumption of milk on the knowledge, attitudes, and practices (KAP) of women who produce and sell dairy products. The intervention consisted of 16 h of training on good milk production practices and prevention of milk-borne diseases. A total of 120 women were trained and their KAP assessed at baseline (pretraining), immediately after training, and 6 mo after training. Overall, training increased the knowledge score of the participants from 75.6 to 91.4% in the immediate post-training assessment, and to 90.0% at 6 mo post-training. Compared with pretraining (58.8%), we found a statistically significant difference in the overall attitude score at the immediate post-training evaluation (64.7%) but not 6 mo after (61.4%). We observed a similar increase in the understanding of correct practices from 49.5% at pretraining to 64.7% 6 mo following the training. For some desirable attitudes and practices, the proportion of women reporting adoption at pretraining was low and the change derived from training still left one-third of respondents displaying a negative attitude and a quarter of them reporting wrong practices. We recommend that future training interventions be complemented with locally adaptable technologies, provision of incentives, and creation of an enabling environment including improved access to clean water and sanitation facilities to affect not only knowledge, but also attitudes and ultimately practices in the long term.

Role of Streptococcus uberis adhesion molecule in the pathogenesis of Streptococcus uberis mastitis.

Adherence to and internalization into mammary epithelial cells are central mechanisms in the pathogenesis of S. uberis mastitis. Through these pathogenic strategies, S. uberis reaches an intracellular environment where humoral host defenses and antimicrobials in milk are essentially ineffective, thus allowing persistence of this pathogen in the mammary gland. We reported that S. uberis expresses a surface adhesion molecule (SUAM) that has affinity for lactoferrin (LF) and a central role adherence to and internalization of S. uberis into bovine mammary epithelial cells. To define the role of SUAM in the pathogenesis of S. uberis mastitis, we created a sua gene deletion mutant clone of S. uberis UT888 (Δsua S. uberis UT888) unable to express SUAM. When tested in vitro, Δsua S. uberis UT888 was defective in adherence to and internalization into bovine mammary epithelial cells. To prove that the absence of SUAM reduces bacterial attachment, subsequent colonization and infection of bovine mammary glands, the wild type S. uberis UT888 and its isogenic Δsua S. uberis UT888 were infused into mammary quarters of dairy cows. Results showed that fewer mammary glands infused with Δsua S. uberis UT888 become infected than those infused with the isogenic parental strain. Furthermore, mammary glands infused with Δsua S. uberis UT888 had less severe clinical symptoms as compared to those infused with the isogenic parental strain. These results suggest that the SUAM mutant clone was less virulent than the isogenic parental strain which further substantiates the role of SUAM in the pathogenesis of S. uberis mastitis.

Short communication: Conservation of Streptococcus uberis adhesion molecule and the sua gene in strains of Streptococcus uberis isolated from geographically diverse areas.

The objective was to identify and sequence the sua gene (GenBank no. DQ232760; http://www.ncbi.nlm.nih.gov/genbank/) and detect Streptococcus uberis adhesion molecule (SUAM) expression by Western blot using serum from naturally S. uberis-infected cows in strains of S. uberis isolated in milk from cows with mastitis from geographically diverse areas of the world. All strains evaluated yielded a 4.4-kb sua-containing PCR fragment that was subsequently sequenced. Deduced SUAM AA sequences from those S. uberis strains evaluated shared >97% identity. The pepSUAM sequence located at the N terminus of SUAM was >99% identical among strains of S. uberis. Streptococcus uberis adhesion molecule expression was detected in all strains of S. uberis tested. These results suggest that sua is ubiquitous among strains of S. uberis isolated from diverse geographic locations and that SUAM is immunogenic.

Deletion of sua gene reduces the ability of Streptococcus uberis to adhere to and internalize into bovine mammary epithelial cells.

To elucidate the role of Streptococcus uberis adhesion molecule (SUAM) in the pathogenesis of S. uberis mastitis, sua deletion in S. uberis UT888 was achieved by homologous recombination using a thermosensitive plasmid. The deletion mutant was analyzed for sua deletion by PCR, southern blot and DNA sequencing, and was designated Δsua S. uberis UT888. As compared to the isogenic parent strain, Δsua S. uberis UT888 did not produce SUAM based on SDS-PAGE gel and western blot. Deletion of sua and lack of expression of SUAM by Δsua S. uberis UT888 markedly reduced the ability of the sua gene deletion mutant of S. uberis to adhere to and internalize into mammary epithelial cells. These results confirm the central role of SUAM in adherence to and internalization of S. uberis into host cells.