Alzheimer’s disease (AD) is an age-related dementia, characterized by amyloid plaques, neurofibrillary tangles, neuroinflammation, and neuronal loss in the brain. Components of the complement system, known to produce a local inflammatory reaction, are associated with the plaques and tangles in AD brain, and thus a role for complement-mediated inflammation in the acceleration or progression of disease has been proposed. A complement activation product, C5a, is known to recruit and activate microglia and astrocytes in vitro by activation of a G protein-coupled cell-surface C5aR. Here, oral delivery of a cyclic hexapeptide C5a receptor antagonist (PMX205) for 2–3 mo resulted in substantial reduction of pathological markers such as fibrillar amyloid deposits (49 – 62%) and activated glia (42– 68%) in two mouse models of AD. The reduction in pathology was correlated with improvements in a passive avoidance behavioral task in Tg2576 mice. In 3xTg mice, PMX205 also significantly reduced hyperphosphorylated tau (69%). These data provide the first evidence that inhibition of a proinflammatory receptor-mediated function of the complement cascade (i.e., C5aR) can interfere with neuroinflammation and neurodegeneration in AD rodent models, suggesting a novel therapeutic target for reducing pathology and improving cognitive function in human AD patients.

Biofilm infections often lead to significant morbidity due to their chronicity and recalcitrance to antibiotics. We have demonstrated that methicillin-resistant Staphylococcus aureus (MRSA) biofilms can evade macrophage antibacterial effector mechanisms by skewing macrophages towards an alternatively activated M2 phenotype. To overcome this immune evasion, we have utilized two complementary approaches. In the first, a proinflammatory milieu was elicited by local administration of classically-activated M1 macrophages and second, by treatment with the C5a receptor (CD88) agonist EP67, which invokes macrophage proinflammatory activity. Early administration of M1-activated macrophages or EP67 significantly attenuated biofilm formation in a mouse model of MRSA catheter-associated infection. Several proinflammatory mediators were significantly elevated in biofilm infected tissues from macrophage- and EP67-treated animals, revealing effective reprogramming of the biofilm environment to a proinflammatory milieu. A requirement for macrophage proinflammatory activity was demonstrated by the fact that transfer of MyD88-deficient macrophages had minimal impact on biofilm growth. Likewise, neutrophil administration had no effect on biofilm formation. Treatment of established biofilm infections with M1-activated macrophages also significantly reduced catheter-associated biofilm burdens compared to antibiotic treatment. Collectively, these results demonstrate that targeting macrophage proinflammatory activity can overcome the local immune inhibitory environment created during biofilm infections and represents a novel therapeutic strategy.

A conformationally biased decapeptide agonist of human C5a (C5a55-74Y65,F67,P69,P71,D-Ala73 or YSFKPMPLaR) was used as a functional probe of the C5a receptor (C5aR) in order to understand the conformational features in the C-terminal effector region of C5a that are important for C5aR binding and signal transduction. YSFKPMPLaR was a potent, full agonist of C5a, but at higher concentrations had a superefficacious effect compared to the natural factor. The maximal efficacy of this analogue was 216 +/- 56% that of C5a in stimulating the release of beta-glucuronidase from human neutrophils. C5aR activation and binding curves both occurred in the same concentration range with YSFKPMPLaR, characteristics not observed with natural C5a or more conformationally flexible C-terminal agonists. YSFKPMPLaR was then used as a C-terminal effector template onto which was synthesized various C5aR binding determinants from the N-terminal core domain of the natural factor. In general, the presence of N-terminal binding determinants had little effect on either potency or binding affinity when the C-terminal effector region was presented to the C5aR in this biologically active conformation. However, one peptide, C5a12-20-Ahx-YSFKPMPLaR, expressed a 100-fold increase in affinity for the neutrophil C5aR and a 6-fold increase in potency relative to YSFKPMPLaR. These analyses showed that the peptides used in this study have up to 25% of the potency of C5a in human fetal artery and up to 5% of the activity of C5a in the PMN enzyme release assay.

J. Neurochem. (2010) 113, 389–401. Abstract Alzheimer’s disease (AD), a progressive neurodegenerative disease characterized by the accumulation of amyloid‐β protein and neuronal loss, is the leading cause of age‐related dementia in the world today. The disease is also associated with neuroinflammation, robust activation of astrocytes and microglia, and evidence of activation of the complement system, localized with both fibrillar amyloid‐β (fAβ) plaques and tangles. The observations are consistent with a complement‐dependent component of AD progression. We have previously shown that inhibition of the major complement receptor for C5a (CD88) with the antagonist PMX205 results in a significant reduction in pathology in two mouse models of AD. To further characterize the role of complement in AD‐related neuroinflammation, we examined the age‐ and disease‐associated expression of CD88 in brain of transgenic mouse models of AD and the influence of PMX205 on the presence of various complement activation products using flow cytometry, western blot, and immunohistochemistry. CD88 was found to be up‐regulated in microglia, in the immediate vicinity of amyloid plaques. While thioflavine plaque load and glial recruitment is significantly reduced after treatment with PMX205, C1q remains co‐localized with fAβ plaques and C3 is still expressed by the recruited astrocytes. Thus, with PMX205, potentially beneficial activities of these early complement components may remain intact, while detrimental activities resulting from C5a–CD88 interaction are inhibited. This further supports the targeted inhibition of specific complement mediated activities as an approach for AD therapy.

A series of decapeptide analogues corresponding to the C-terminal region of human C5a anaphylatoxin (C5a65-74) was synthesized with residue substitutions to restrict conformational flexibility in the C-terminus. These conformationally constrained peptides behaved as agonists of C5a in spasmogenic assays (smooth muscle contraction in human fetal artery, guinea pig ileum, and guinea pig lung parenchyma) as well as guinea pig platelet aggregation. There were significant correlations in the potencies of these peptides between the various assays. A structure-function analysis led to the identification of a preferred backbone conformation that correlated with the expression of these biological responses. These backbone structural motifs were consistent with a helix-like conformation for residues 65-69, an elongated structure for residues 70-71, and a beta-turn of either type II or type V for residues (71)72-74. The most potent of these agonists expressed almost 5% of the potency of natural C5a.

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a b s t r a c tVaccines to methamphetamine (meth) were designed by covalently attaching a meth hapten (METH) to peptide constructs that contained a conformationally biased, response-selective molecular adjuvant, YSFKPMPLaR (EP54). Rats immunized with EP54-containing meth vaccines generated serum antibody titers to authentic meth, an immune outcome that altered meth self-administration. Immunization increased meth self-administration suggesting pharmacokinetic antagonism. The ability of immune sera to bind a METH-modified target protein dramatically decreased during and shortly after the meth selfadministration assay, suggesting effective sequestration of free meth. However, the binding ability of immune sera to the METH-modified target protein was recovered 34 days after meth-free clearance time.

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