Complement Opsonization Research Articles

Complement opsonized protein corona activated by precoated immunoglobulin enables neutrophil-hitchhiking for rapid and enhanced drug delivery for acute liver failure recovery

In acute inflammation, the heightened activation and recruitment of immune cells present an opportunity to leverage them as natural carriers for efficient transport of diagnostic probes and nanotherapeutics. Although complement opsonization facilitates the internalization of nanomedicines by activated neutrophils, the development of strategies to specifically augment complement deposition remains a challenge. Herein, we engineer silymarin-loaded liposomes (Lips) coated with immunoglobulin G (IgG) to enhance complement 3 (C3) deposition in the protein corona, thereby enabling neutrophil-mediated, precise targeting to the site of inflammation. Through the examination of various serum proteins, we discover that IgG adsorption, particularly with its Fc portion exposed, prominently promotes C3 enrichment in the protein corona, resulting in C3 cleavage into iC3b. This facilitates the uptake of C3-enriched Lips by activated neutrophils with elevated C3 receptor expression, thus improving the efficiency and specificity of nanomedicine delivery to inflammatory site. Following the formation of neutrophil extracellular traps, the released nanomedicine effectively mitigates hepatocyte damage by eliminating accumulated reactive oxygen species and inducing a shift in macrophage polarization towards the anti-inflammatory M2 phenotype. Our IgG-modified nanomedicine demonstrates significant therapeutic efficacy against acute liver failure by regulating the protein corona and hitchhiking neutrophils, offering a promising strategy for efficient and precise treatment of inflammation.

Validation of dot blot immunoassay for measurement of complement opsonization of nanoparticles

Complement plays a critical role in the immune response toward nanomaterials. The complement attack on a foreign surface results in the deposition of C3, assembly of C3 convertases, the release of anaphylatoxins C3a and C5a, and finally, the formation of membrane attack complex C5b-9. Various technologies can measure complement activation markers in the fluid phase, but measurements of surface C3 deposition are less common. Previously, we developed an ultracentrifugation-based dot blot immunoassay (DBI) to measure the deposition of C3 and other protein corona components on nanoparticles. Here, we validate the repeatability of the DBI and its correlation with pathway-specific and common fluid phase markers. Moreover, we discuss the advantages of DBI, such as cost-effectiveness and versatility, while addressing potential limitations. This study provides insights into complement activation at the nanosurface level, offering a valuable tool for nanomedicine researchers in the field.

The human factor H protein family - an update.

Complement is an ancient and complex network of the immune system and, as such, it plays vital physiological roles, but it is also involved in numerous pathological processes. The proper regulation of the complement system is important to allow its sufficient and targeted activity without deleterious side-effects. Factor H is a major complement regulator, and together with its splice variant factor H-like protein 1 and the five human factor H-related (FHR) proteins, they have been linked to various diseases. The role of factor H in inhibiting complement activation is well studied, but the function of the FHRs is less characterized. Current evidence supports the main role of the FHRs as enhancers of complement activation and opsonization, i.e., counter-balancing the inhibitory effect of factor H. FHRs emerge as soluble pattern recognition molecules and positive regulators of the complement system. In addition, factor H and some of the FHR proteins were shown to modulate the activity of immune cells, a non-canonical function outside the complement cascade. Recent efforts have intensified to study factor H and the FHRs and develop new tools for the distinction, quantification and functional characterization of members of this protein family. Here, we provide an update and overview on the versatile roles of factor H family proteins, what we know about their biological functions in healthy conditions and in diseases.

The Complement System and C4b-Binding Protein: A Focus onthe Promise of C4BPα as a Biomarker to Predict Clopidogrel Resistance.

The complement system plays a dual role in the body, either as a first-line defense barrier when balanced between activation and inhibition or as a potential driver of complement-associated injury or diseases when unbalanced or over-activated. C4b-binding protein (C4BP) was the first circulating complement regulatory protein identified and itfunctions as an important complement inhibitor. C4BP can suppress the over-activation of complement components and prevent the complement system from attacking the host cells through the binding of complement cleavage products C4b and C3b, working in concert as a cofactor for factor I in the degradation of C4b and C3b, and consequently preventing or reducing the assembly of C3 convertase and C5 convertase, respectively. C4BP, particularly C4BP α-chain (C4BPα), exerts its unique inhibitory effects on complement activation and opsonization, systemic inflammation, and platelet activation and aggregation. It has long been acknowledged that crosstalk or interplay exists between the complement system and platelets. Our unpublished preliminary data suggest that circulating C4BPα exerts its antiplatelet effects through inhibition of both complement activity levels and complement-induced platelet reactivity. Plasma C4BPα levels appear to be significantly higher in patients sensitive to, rather than resistant to, clopidogrel, and we suggest that a plasma C4BPα measurement could be used to predict clopidogrelresistance in the clinical settings.

Complement C3 deposition restricts the proliferation of internalized Staphylococcus aureus by promoting autophagy.

Complement C3 (C3) is usually deposited spontaneously on the surfaces of invading bacteria prior to internalization, but the impact of C3 coating on cellular responses is largely unknown. Staphylococcus aureus (S. aureus) is a facultative intracellular pathogen that subverts autophagy and replicates in both phagocytic and nonphagocytic cells. In the present study, we deposited C3 components on the surface of S. aureus by complement opsonization before cell infection and confirmed that C3-coatings remained on the surface of the bacteria after they have invaded the cells, suggesting S. aureus cannot escape or degrade C3 labeling. We found that the C3 deposition on S. aureus notably enhanced cellular autophagic responses, and distinguished these responses as xenophagy, in contrast to LC3-associated phagocytosis (LAP). Furthermore, this upregulation was due to the recruitment of and direct interaction with autophagy-related 16-like 1 (ATG16L1), thereby resulting in autophagy-dependent resistance to bacterial growth within cells. Interestingly, this autophagic effect occurred only after C3 activation by enzymatic cleavage because full-length C3 without cleavage of the complement cascade reaction, although capable of binding to ATG16L1, failed to promote autophagy. These findings demonstrate the biological function of intracellular C3 upon bacterial infection in enhancing autophagy against internalized S. aureus.

Inhibition of acute complement responses towards bolus-injected nanoparticles using targeted short-circulating regulatory proteins.

Effective inhibition of the complement system is needed to prevent the accelerated clearance of nanomaterials by complement cascade and inflammatory responses. Here we show that a fusion construct consisting of human complement receptor 2 (CR2) (which recognizes nanosurface-deposited complement 3 (C3)) and complement receptor 1 (CR1) (which blocks C3 convertases) inhibits complement activation with picomolar to low nanomolar efficacy on many types of nanomaterial. We demonstrate that only a small percentage of nanoparticles are randomly opsonized with C3 both in vitro and in vivo, and CR2-CR1 immediately homes in on this subpopulation. Despite rapid in vivo clearance, the co-injection of CR2-CR1 in rats, or its mouse orthologue CR2-Crry in mice, with superparamagnetic iron oxide nanoparticles nearly completely blocks complement opsonization and unwanted granulocyte/monocyte uptake. Furthermore, the inhibitor completely prevents lethargy caused by bolus-injected nanoparticles, without inducing long-lasting complement suppression. These findings suggest the potential of the targeted complement regulators for clinical evaluation.

Medium supplementation with human, but not fetal calf serum facilitates endocytosis of PLGA nanoparticles by human primary B-lymphocytes via complement opsonization

The “biological identity” of nanoparticles (NPs) is governed by a shell consisting of various biomolecules that is formed upon exposure to biological media, the so-called biomolecule corona. Consequently, supplementation of cell culture media with e.g. different sera is likely to affect interactions between cells and NPs ex-vivo, especially endocytosis. We aimed to investigate the differential impact of human and fetal-bovine serum on the endocytosis of poly (lactic-co-glycolic acid) NPs by human peripheral blood mononuclear cells via flow cytometry. Furthermore, we employed different methods to inhibit endocytosis, providing mechanistic insights. The resulting biomolecule corona was characterized via denaturing gel electrophoresis. We found profound differences between human and fetal bovine serum regarding the endocytosis of fluorescently labeled PLGA nanoparticles by different classes of human leukocytes. Uptake by B-lymphocytes was particularly sensitive. We further present evidence, that these effects are mediated by a biomolecule corona. We demonstrate to our knowledge for the first time that the complement is an important contributor to the endocytosis of non-surface-engineered PLGA-nanoparticles prepared via emulsion solvent evaporation by human immune cells. Our data demonstrates that results obtained with xenogeneic culture supplements such as fetal bovine serum may have to be interpreted with caution.

What is the role of autoantibodies in post-artesunate delayed hemolysis?

We read with great interest the recent publication by Kurth et al.1 that highlights an interesting aspect of post-artesunate delayed hemolysis (PADH) among uncomplicated malaria patients treated with oral artemisinin-based combination therapy (ACT). Post-treatment delayed hemolysis has increasingly been observed, especially among travellers from non-endemic areas.2 Besides the well-known ‘pitting’ mechanism, the article discussed that ACT might produce drug-autoantibodies that contribute to post-treatment hemolysis. We would like to discuss the possible role of autoantibodies against red blood cells (RBC) as a pathophysiologic mechanism of PADH and the clinical implication of corticosteroid therapy for patients with PADH. Camprubí et al. (2019) reported a case of PADH in a splenectomized patient with a positive direct antiglobulin test (DAT); this raised a critical discussion as the ‘pitting’ mechanism cannot explain the hemolysis in this patient.3 The phenomenon may be explained by three hypotheses involving drug-induced immune hemolytic anaemia. First, the drug, acting as a hapten, attaches to the RBC membrane and induces autoantibody reactions. Second, the immune complex mechanism involves anti-drug antibodies produced during artesunate treatment in previous infections. Once artesunate is administered in subsequent infections, a drug-anti-drug immune complex is formed and randomly binds to the RBC surface, which activates complement fixation and opsonization, leading to cell lysis. Lastly, it assumes that the drug may act as a coating for the RBCs. If IgG antibodies against the drug are present, the reaction to the drug-coated RBCs can cause hemolysis. The immune complex mechanism may explain the high levels of autoantibodies found among ‘semi-immune’ patients of African descent who developed PADH in the recent study by Kurth et al.

P917 Intestinal complement interacts with commensal microbiota and provides pattern recognition in Inflammatory Bowel Disease

Abstract Background The complement system is a central humoral part of innate immunity and provides essential pattern recognition capabilities as well as effector functions such as opsonisation and target cell lysis. Its prominent role in infection and immunity is undisputed but its involvement in the pathogenesis of inflammatory bowel diseases remains less clear. Published data point to a role of complement within the intestinal lumen supporting clearance of pathogens1. Methods Expression of complement proteins within the intestinal epithelium was quantified by real-time qPCR on lesional and non-lesional biopsy samples from patients with IBD and healthy controls. The concentration of complement proteins was measured in fecal supernatants using ELISA. Flow cytometry of fecal bacterial single cell suspensions was used to assess complement (C3) and antibody (IgA) opsonisation status. Finally, cytometrically distinct populations were isolated by fluorescence-assisted cell sorting (FACS) and microbial community composition was investigated using 16S rDNA sequencing. Prediction of functional profiles from amplicon data was performed using Tax4Fun2. Results Complement expression in intestinal tissue was increased during active inflammation but certain targets were significantly less expressed in lesional mucosal sites (e.g. C6, C7). Free complement proteins in fecal supernatants were mostly undetectable by ELISA. In contrast, complement opsonisation was verified on fecal bacteria using flow cytometry. The degree of complement deposited on bacterial surfaces was significantly correlated with fecal calprotectin (p < 0.01). The percentage of complement-opsonized bacteria ranged from 0 to 5.3 % and did not correlate with intestinal inflammation while percentages of IgA opsonisation were generally higher (0.4 - 90.1%) and increased with fecal calprotectin (p < 0.01). FACS followed by 16S amplicon sequencing detected differences in bacterial taxa abundance between complement-opsonized, IgA-opsonized and non-opsonized fractions. Functional in-silico profiling revealed associations of complement-opsonization with bacterial virulence factors. Conclusion Luminal and mucosal complement expression and activity is evident in patients with IBD. Complement opsonisation profiles are distinct from IgA opsonisation and show features of specificity regarding recognition of microbial features.

Complement Shields Fc Regions on HIT Immune Complexes and Prevents Recognition By Cellular Fcγ Receptors

Heparin-induced thrombocytopenia (HIT) is a life-threatening immune-mediated thrombotic disorder caused by immune complexes (ICs) containing IgG antibodies to platelet factor 4 (PF4)/heparin complexes. In previous studies, we established that complement opsonization of HIT ICs is essential for cellular binding of ICs and subsequent engagement of Fcγ receptors (FcγRs). We additionally showed that complement inhibition alone prevented FcγR-mediated effector functions, such as neutrophil degranulation, monocyte tissue factor expression, and procoagulant activity (Khandelwal, Blood 2021). As KKO and HIT ICs can also bind FcγRs in media without complement, we undertook these studies to examine the direct effects of complement on IC-FcγR interactions. For these studies, we used THP-1 cells or U937 cells, monocytic cell lines expressing FcγRI and FcγRII, but not complement receptors (CRs). Cells were incubated with AF-647 labeled KKO (50 mg/ml), a HIT-like monoclonal antibody, either alone or with PF4 (25 mg/ml) and heparin (1U/ml) to form in situ KKO ICs. Labeled KKO or KKO ICs were added to RPMI-containing media (lacking complement) or undiluted citrated plasma (source of complement) in the presence or absence of anti-FcγRIIA. Binding of labeled IgG or anti-C3c was examined by flow cytometry. Consistent with prior observations, THP-1 cells incubated in media show robust binding of KKO ICs in a FcγRII dependent manner (70% reduction in binding with anti-FcγRII; Figure 1A). Surprisingly, in undiluted plasma, there was minimal KKO IC binding to THP-1 cells, despite adequate complement generation (Figure 1B). Similar effects of plasma vs. media were seen in confocal experiments using KKO ICs with THP-1 cells (Figure 1C & 1D), HIT ICs incubated with THP-1 cells (containing HIT patient IgG, PF4/heparin; data not shown), or KKO ICs incubated with U937 cells (data not shown). In other studies, we note that binding of KKO ICs was dependent on the source of complement, with undiluted human plasma showing maximal inhibitory effects (100%), while undiluted normal human serum (NHS) and fetal bovine serum (FBS) reduced KKO IC binding by 70% and 50%, respectively (data not shown). To demonstrate that the inhibitory effects of undiluted plasma on KKO IC binding was complement-mediated, THP-1 cells were incubated in plasma containing the complement inhibitors BBK32 (C1r inhibitor) or CP40 (C3 inhibitor) prior to addition of labeled KKO ICs. In other experiments, THP-1 cells were incubated with labeled KKO ICs in media containing human complement proteins (C1+C3+C4). As shown, complement inhibition in plasma restored KKO IC binding to cellular FcγR (Figure 2A). Conversely, addition of purified complement components to media resulted in reduced KKO IC binding (Figure 2B). Similar effects of complement proteins and inhibitors were noted in ELISA-based assays using immobilized FcγRIIA incubated with KKO ICs in plasma or media (data not shown). These studies demonstrate striking inhibitory effects of complement on IC-FcγR interactions. Specifically, complement shields Fc regions on ICs from recognition and binding to cellular FcγRs and this masking effect is reversed by complement inhibition. We additionally show that these masking effects of complement are less apparent in media containing FBS, the most commonly used source of complement for cell-based studies. Taken together with our recent observations showing requirements for complement receptors in binding complement-opsonized KKO ICs, these studies suggest that the masking effects of complement on ICs prevent FcγR activation on cells lacking CRs. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

468 Complement opsonization promotes efficient Mycobacterium avium killing by human neutrophils

468 Complement opsonization promotes efficient Mycobacterium avium killing by human neutrophils

Morphology-driven protein corona manipulation for preferential delivery of lipid nanodiscs

PEGylated lipid-based nanocarriers have significantly improved drug delivery efficiency while reducing toxicity. However, protein corona formation on the nano-surface alters their biological identity, resulting in unpredictable in vivo performance. In particular, binding of pre-existing anti-PEG antibodies can accelerate the blood clearance of PEGylated nanocarriers by complement activation and opsonization, leading to a drop in efficacy and unexpected adverse immune effects. Precisely modulating the composition and function of the protein corona can provide an effective approach to achieve efficient and safe drug delivery. Herein, we unraveled that discoid-shaped lipid nanodiscs displayed a unique protein corona pattern, demonstrating an entirely different biological fate from spherical liposomes. The discoid morphology considerably reduced complement binding and activation, enabling nanodiscs to evade the accelerated blood clearance phenomenon that severely impacts in vivo performance of most PEGylated nanocarriers. Furthermore, apolipoproteins preferentially adsorbed on the discoid surface along with their preserved functions and endowed nanodiscs with distinct brain targeting capability. Overall, the work presented here provides new insights into morphology-driven manipulation of the protein corona on the lipid-based nanocarriers for efficient preferential drug delivery.

Streptococcus pneumoniae interactions with the complement system.

Host innate and adaptive immunity to infection with Streptococcus pneumoniae is critically dependent on the complement system, demonstrated by the high incidence of invasive S. pneumoniae infection in people with inherited deficiency of complement components. The complement system is activated by S. pneumoniae through multiple mechanisms. The classical complement pathway is activated by recognition of S. pneumoniae by C-reactive protein, serum amyloid P, C1q, SIGN-R1, or natural or acquired antibody. Some S. pneumoniae strains are also recognised by ficolins to activate the mannose binding lectin (MBL) activation pathway. Complement activation is then amplified by the alternative complement pathway, which can also be activated by S. pneumoniae directly. Complement activation results in covalent linkage of the opsonic complement factors C3b and iC3b to the S. pneumoniae surface which promote phagocytic clearance, along with complement-mediated immune adherence to erythrocytes, thereby protecting against septicaemia. The role of complement for mucosal immunity to S. pneumoniae is less clear. Given the major role of complement in controlling infection with S. pneumoniae, it is perhaps unsurprising that S. pneumoniae has evolved multiple mechanisms of complement evasion, including the capsule, multiple surface proteins, and the toxin pneumolysin. There is considerable variation between S. pneumoniae capsular serotypes and genotypes with regards to sensitivity to complement which correlates with ability to cause invasive infections. However, at present we only have a limited understanding of the main mechanisms causing variations in complement sensitivity between S. pneumoniae strains and to non-pathogenic streptococci.

Antibody-Dependent Complement Responses toward SARS-CoV-2 Receptor-Binding Domain Immobilized on "Pseudovirus-like" Nanoparticles.

Many aspects of innate immune responses to SARS viruses remain unclear. Of particular interest is the role of emerging neutralizing antibodies against the receptor-binding domain (RBD) of SARS-CoV-2 in complement activation and opsonization. To overcome challenges with purified virions, here we introduce “pseudovirus-like” nanoparticles with ∼70 copies of functional recombinant RBD to map complement responses. Nanoparticles fix complement in an RBD-dependent manner in sera of all vaccinated, convalescent, and naïve donors, but vaccinated and convalescent donors with the highest levels of anti-RBD antibodies show significantly higher IgG binding and higher deposition of the third complement protein (C3). The opsonization via anti-RBD antibodies is not an efficient process: on average, each bound antibody promotes binding of less than one C3 molecule. C3 deposition is exclusively through the alternative pathway. C3 molecules bind to protein deposits, but not IgG, on the nanoparticle surface. Lastly, “pseudovirus-like” nanoparticles promote complement-dependent uptake by granulocytes and monocytes in the blood of vaccinated donors with high anti-RBD titers. Using nanoparticles displaying SARS-CoV-2 proteins, we demonstrate subject-dependent differences in complement opsonization and immune recognition.

Complement C3 deficiency enhances anti-CD47 efficacy in murine ovarian cancer model.

Abstract Epithelial ovarian cancer (OC) is the most lethal gynecological malignancy. While OC is an immunogenic tumor, single-agent anti-PD-1 have limited efficacy in recurrent OC. Blockade of the CD47/SIRPα pathway, a phagocytosis checkpoint in macrophages and other myeloid cells, can enhance myeloid-driven antitumor immunity and tumor control. However, the benefit of targeting CD47/SIRPα in recurrent OC has been limited. Prior work from our lab and others point to complement priming of innate immune responses as a barrier to T-cell-driven anti-tumor immunity. However, in the specific context of anti-CD47 therapy, complement opsonization of tumor cells could augment the capacity of myeloid cells to phagocytose or injure tumor cells. The role of complement deficiency with anti-CD47 therapy in tumor control is a gap in the field, we therefore evaluated the efficacy of anti-CD47 in female wild-type (WT) versus C3−/− and C5aR1−/− with syngeneic OC (ID8). Mice (n=8–10 per group) were administered IP ID8 tumor cells followed by anti-CD47 or isotype twice weekly for 3 weeks and were monitored for the ascites development and survival. On day 84, all WT mice treated with isotype had ascites by visual inspection and 3 of 10 died. The proportion of mice with ascites varied in other groups, C3−/− mice treated with anti-CD47 having the lowest proportion, 4 of 9 mice with ascites and no deaths (Fisher’s test, WT-isotype vs C3−/− + anti-CD47, p= 0.01). A limitation is the potential endogenous complement production by tumor cells, which will be evaluated. These results suggest a potential benefit for dual targeting of the CD47/SIRPα and complement pathways in OC. Additional studies will probe immunologic correlates and survival benefits of these therapies in OC. This work was supported by Roswell Park Cancer Center Support Grant P30CA016056 and Apellis Pharmaceuticals, Inc

Unravelling Heterogeneities in Complement and Antibody Opsonization of Individual Liposomes as a Function of Surface Architecture.

Coating nanoparticles with poly(ethylene glycol) (PEG) is widely used to achieve long-circulating properties after infusion. While PEG reduces binding of opsonins to the particle surface, immunogenic anti-PEG side-effects show that PEGylated nanoparticles are not truly "stealth" to surface active proteins. A major obstacle for understanding the complex interplay between opsonins and nanoparticles is the averaging effects of the bulk assays that are typically applied to study protein adsorption to nanoparticles. Here, a microscopy-based method for directly quantifying opsonization at the single nanoparticle level is presented. Various surface coatings are investigated on liposomes, including PEG, and show that opsonization by both antibodies and complement C3b is highly dependent on the surface chemistry. It is further demonstrated that this opsonization is heterogeneous, with opsonized and non-opsonized liposomes co-existing in the same ensemble. Surface coatings modify the percentage of opsonized liposomes and/or opsonin surface density on the liposomes, with strikingly different patterns for antibodies and complement. Thus, this assay provides mechanistic details about opsonization at the single nanoparticle level previously inaccessible to established bulk assays.

Mannose-binding lectin conjugated to quantum dots as fluorescent nanotools for carbohydrate tracing

Quantum dots (QDs) have stood out as nanotools for glycobiology due to their photostability and ability to be combined with lectins. Mannose-binding lectin (MBL) is involved in the innate immune system and plays important roles in the activation of the complement cascade, opsonization, and elimination of apoptotic and microbial cells. Herein, adsorption and covalent coupling strategies were evaluated to conjugate QDs to a recombinant human MBL (rhMBL). The most efficient nanoprobe was selected by evaluating the conjugate ability to label Candida albicans yeasts by flow cytometry. The QDs-rhMBL conjugate obtained by adsorption at pH 6.0 was the most efficient, labeling ca. 100% of cells with the highest median fluorescence intensity. The conjugation was also supported by Fourier transform infrared spectroscopy, zeta potential, and size analyses. C. albicans labeling was calcium-dependent; 12% and <1% of cells were labeled in buffers without calcium and containing EDTA, respectively. The conjugate promoted specific labeling (based on cluster effect) since, after inhibition with mannan, there was a reduction of 80% in cell labeling, which did not occur with methyl-α-D-mannopyranoside monosaccharide. Conjugates maintained colloidal stability, bright fluorescence, and biological activity for at least 8 months. Therefore, QDs-rhMBL conjugates are promising nanotools to elucidate the roles of MBL in biological processes.

Combating Complement's Deleterious Effects on Nanomedicine by Conjugating Complement Regulatory Proteins to Nanoparticles.

Complement opsonization is among the biggest challenges facing nanomedicine. Nearly instantly after injection into blood, nanoparticles are opsonized by the complement protein C3, leading to clearance by phagocytes, fouling of targeting moieties, and release of anaphylatoxins. While surface polymers such as poly(ethylene glycol) (PEG) partially decrease complement opsonization, most nanoparticles still suffer from extensive complement opsonization, especially when linked to targeting moieties. To ameliorate the deleterious effects of complement, two of mammals' natural regulators of complement activation (RCAs), Factors H and I, are here conjugated to the surface of nanoparticles. In vitro, Factor H or I conjugation to PEG-coated nanoparticles decrease their C3 opsonization, and markedly reduce nanoparticle uptake by phagocytes. In an in vivo mouse model of sepsis-induced lung injury, Factor I conjugation abrogates nanoparticle uptake by intravascular phagocytes in the lungs, allowing the blood concentration of the nanoparticle to remain elevated much longer. For nanoparticles targeted to the lung's endothelium by conjugation to anti-ICAM antibodies, Factor I conjugation shifts the cell-type distribution away from phagocytes and toward endothelial cells. Finally, Factor I conjugation abrogates the severe anaphylactoid responses common to many nanoparticles, preventing systemic capillary leak and preserving blood flow to visceral organs and the brain. Thus, conjugation of RCAs, like Factor I, to nanoparticles is likely to help in nanomedicine's long battle against complement, improving several key parameters critical for clinical success.

Neisseria gonorrhoeae physiology and pathogenesis.

Neisseria gonorrhoeae is an obligate human pathogen that is the cause of the sexually transmitted disease gonorrhoea. Recently, there has been a surge in gonorrhoea cases that has been exacerbated by the rapid rise in gonococcal multidrug resistance to all useful antimicrobials resulting in this organism becoming a significant public health burden. Therefore, there is a clear and present need to understand the organism's biology through its physiology and pathogenesis to help develop new intervention strategies. The gonococcus initially colonises and adheres to host mucosal surfaces utilising a type IV pilus that helps with microcolony formation. Other adhesion strategies include the porin, PorB, and the phase variable outer membrane protein Opa. The gonococcus is able to subvert complement mediated killing and opsonisation by sialylation of its lipooligosaccharide and deploys a series of anti-phagocytic mechanisms. N. gonorrhoeae is a fastidious organism that is able to grow on a limited number of primary carbon sources such as glucose and lactate. The utilization of lactate by the gonococcus has been implicated in a number of pathogenicity mechanisms. The bacterium lives mainly in microaerobic environments and can grow both aerobically and anaerobically with the aid of nitrite. The gonococcus does not produce siderophores for scavenging iron but can utilize some produced by other bacteria, and it is able to successful chelate iron from host haem, transferrin and lactoferrin. The gonococcus is an incredibly versatile human pathogen; in the following chapter, we detail the intricate mechanisms used by the bacterium to invade and survive within the host.

Nanomedicine hitchhikes on neutrophils to the inflamed lung.

Supramolecular arrangement of proteins provides nanoparticles with neutrophil tropism via complement opsonization during an acute inflammation, enabling diagnosis and treatment of acute lung injury.