An experimental investigation of the rôle of the blood fluids in connection with phagocytosis. 1903

Diagnostic Role of Opsonic Activity in Acinetobacter baumannii Ventilator-Associated Pneumonia

In this study, we investigated the diagnostic value of opsonic activity against Acinetobacter baumannii in Ventilator-Associated Pneumonia (VAP) among 50 patients, compared to 102 negative and positive controls. Out of the 50 patients, only 33 (66 %) were diagnosed with VAP using the Clinical Pulmonary Infection Score (CPIS). The opsonic activity assay demonstrated three key findings: (i) 95 % sensitivity and 91.7 % specificity, with a Receiver Operating Characteristic (ROC) area of 0.976 for distinguishing A. baumannii culture positives from negatives; (ii) 95 % sensitivity and 78.7 % specificity, with a 0.915 ROC area, in differentiating VAP/blood culture positive patients from colonized/negative groups; (iii) An ROC area of 0.553 for VAP and colonization, as identified by CPIS alone, indicating an indeterminate threshold. These results highlight that CPIS, microbiological, and clinical evaluations were not correlated, suggesting that opsonic activity against A. baumannii could be a potential VAP diagnostic tool, with the need for large-scale validations.

The Interplay between Salmonella and Intestinal Innate Immune Cells in Chickens

Salmonellosis is a common infection in poultry, which results in huge economic losses in the poultry industry. At the same time, Salmonella infections are a threat to public health, since contaminated poultry products can lead to zoonotic infections. Antibiotics as feed additives have proven to be an effective prophylactic option to control Salmonella infections, but due to resistance issues in humans and animals, the use of antimicrobials in food animals has been banned in Europe. Hence, there is an urgent need to look for alternative strategies that can protect poultry against Salmonella infections. One such alternative could be to strengthen the innate immune system in young chickens in order to prevent early life infections. This can be achieved by administration of immune modulating molecules that target innate immune cells, for example via feed, or by in-ovo applications. We aimed to review the innate immune system in the chicken intestine; the main site of Salmonella entrance, and its responsiveness to Salmonella infection. Identifying the most important players in the innate immune response in the intestine is a first step in designing targeted approaches for immune modulation.

How Phagocytes Acquired the Capability of Hunting and Removing Pathogens From a Human Body: Lessons Learned From Chemotaxis and Phagocytosis of Dictyostelium discoideum (Review)

How phagocytes find invading microorganisms and eliminate pathogenic ones from human bodies is a fundamental question in the study of infectious diseases. About 2.5 billion years ago, eukaryotic unicellular organisms–protozoans–appeared and started to interact with various bacteria. Less than 1 billion years ago, multicellular animals–metazoans–appeared and acquired the ability to distinguish self from non-self and to remove harmful organisms from their bodies. Since then, animals have developed innate immunity in which specialized white-blood cells phagocytes- patrol the body to kill pathogenic bacteria. The social amoebae Dictyostelium discoideum are prototypical phagocytes that chase various bacteria via chemotaxis and consume them as food via phagocytosis. Studies of this genetically amendable organism have revealed evolutionarily conserved mechanisms underlying chemotaxis and phagocytosis and shed light on studies of phagocytes in mammals. In this review, we briefly summarize important studies that contribute to our current understanding of how phagocytes effectively find and kill pathogens via chemotaxis and phagocytosis.

Harnessing the immune system for the treatment of Parkinson's disease

Current treatment options for Parkinson's disease (PD) typically aim to replace dopamine, and hence only provide symptomatic relief. However, in the long run, this approach alone loses its efficacy as it is associated with debilitating side effects. Hence there is an unmet clinical need for addressing levodopa resistant symptoms, and an urgency to develop therapies that can halt or prevent the course of PD. The premise that α-syn can transmit from cell-to-cell in a prion like manner has opened up the possibility for the use of immunotherapy in PD. There is evidence for inflammation in PD as is evidenced by microglial activation, as well as the involvement of the peripheral immune system in PD, and peripheral inflammation can exacerbate dopaminergic degeneration as seen in animal models of the disease. However, mechanisms that link the immune system with PD are not clear, and the sequence of immune responses with respect to PD are still unknown. Nevertheless, our present knowledge offers avenues for the development of immune-based therapies for PD. In order to successfully employ such strategies, we must comprehend the state of the peripheral immune system during the course of PD. This review describes the developments in the field of both active and passive immunotherapies in the treatment of PD, and highlights the crucial need for future research for clarifying the role of inflammation and immunity in this debilitating disease.

Nanoparticle modification in biological media: implications for oral nanomedicines

Nanomedicine has shown potential in enabling oral administration of poorly absorbable drugs, such as biologics. As part of the process related to optimisation of the safety and efficacy of nanomedicines, it is imperative that the interaction of nanoparticles with the biological systems – including the gut – is fully characterised. In this article, we provide an overview of the major mechanisms by which nanoparticles may transform upon introduction in biological media. Specifically, the phenomena of association, dissolution and biomolecule adsorption are discussed, together with factors which influence the occurrence of each phenomenon. The implications of these phenomena within the context of therapeutic action of nanomedicines, which includes reduced targeting efficiency, are also explored. Finally, we will comment on nanoparticle modification within the gut environment, including the currently available gastrointestinal models for the study of nano-bio interactions, with implications in the area of nanomedicines for oral administration.

Nanomedicines undergo transformation in biological media, which impacts biological effects. Such transformation in the gut environment has implications in use of nanomedicines for oral administration.

Role of different receptors and actin filaments on Salmonella Typhimurium invasion in chicken macrophages

Bacterial attachment to host cell is the first event for pathogen entry. The attachment is mediated through membrane expressed adhesins present on the organism and receptors on the cell surface of host. The objective of this study was to investigate the significance of Fc receptors (FcRs), actin filament polymerization, mannose receptors (MRs), carbohydrate moieties like N-linked glycans and sialic acid on chicken macrophages for invasion of S. Typhimurium. Opsonisation of S. Typhimurium resulted in three folds more invasion in chicken monocyte derived macrophages. Cytochalasin D, an inhibitor of actin filament polymerization prevented uptake of S. Typhimurium. Pre-incubation of macrophages with cytochalasin D, showed severe decrease (28 folds) in S. Typhimurium invasion. Next we attempted to analyse the role of carbohydrate receptors of macrophages in S. Typhimurium invasion. Treatment of macrophages with methyl α-d-mannopyranoside, PNGase F and neuraminidase, showed 2.5, 5 and 2.5 folds decrease in invasion respectively. Our data suggest that deglycosylation of N-linked glycans including sialic acid by PNGase F is more effective in inhibition of S. Typhimurium invasion than neuraminidase which removes only sialic acid. These findings suggested FcRs, actin filament polymerization, MRs, N-linked glycans and sialic acid may act as gateway for entry of S. Typhimurium.

Phagocytosis and killing of Staphylococcus aureus by human neutrophils

Neutrophils are essential for host defense against Staphylococcus aureus infections. Although significant progress has been made, our understanding of neutrophil interactions with S. aureus remains incomplete. To provide a more comprehensive view of this process, we investigated phagocytosis and killing of S. aureus by human neutrophils using varied assay conditions in vitro. A greater percentage of bacteria were internalized by adherent neutrophils compared to those in suspension, and, unexpectedly, uptake of S. aureus by adherent neutrophils occurred efficiently in the absence of opsonins. An antibody specific for S. aureus promoted uptake of unopsonized bacteria in suspension, but had little or no capacity to enhance phagocytosis of S. aureus opsonized with normal human serum or by adherent neutrophils. Collectively, these results indicate that assay conditions can have a significant influence on the phagocytosis and killing of S. aureus by neutrophils. More importantly, the results suggest a vaccine approach directed to enhance opsonophagocytosis alone is not sufficient to promote increased killing of S. aureus by human neutrophils. With the emergence and reemergence of antibiotic-resistant microorganisms, establishing parameters that are optimal for studying neutrophil-S. aureus interactions will pave the way towards developing immune-directed strategies for anti-staphylococcal therapies.

Recognition of pathogenic microbes by the Drosophila phagocytic pattern recognition receptor Eater

Non-opsonic phagocytosis is a primordial form of pathogen recognition that is mediated by the direct interaction of phagocytic receptors with microbial surfaces. In the fruit fly Drosophila melanogaster, the EGF-like repeat containing scavenger receptor Eater is expressed by phagocytes and is required to survive infections with gram-positive and gram-negative bacteria. However, the mechanisms by which this receptor recognizes different types of bacteria are poorly understood. To address this problem, we generated a soluble, Fc-tagged receptor variant of Eater comprising the N-terminal 199 amino acids including four EGF-like repeats. We first established that Eater-Fc displayed specific binding to broad yet distinct classes of heat- or ethanol-inactivated microbes and behaved similarly to the membrane-bound, full-length Eater receptor. We then used Eater-Fc as a tool to probe Eater binding to the surface of live bacteria. Eater-Fc bound equally well to naive or inactivated Staphylococcus aureus or Enterococcus faecalis, suggesting that in vivo, Eater directly targets live gram-positive bacteria, enabling their phagocytic clearance and destruction. By contrast, Eater-Fc was unable to interact with live, naive gram-negative bacteria (Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa). For these bacteria, Eater-Fc binding required membrane-disrupting treatments. Furthermore, we found that cecropin A, a cationic, membrane-disrupting antimicrobial peptide, could promote Eater-Fc binding to live E. coli, even at sublethal concentrations. These results suggest a previously unrecognized mechanism by which antimicrobial peptides cooperate with phagocytic receptors to extend the range of microbes that can be targeted by a single, germline-encoded receptor.