Distinct roles of the anaphylatoxin receptors C3aR, C5aR1 and C5aR2 in experimental meningococcal infections.

The complement system is pivotal in the defense against invasive disease caused by (, meningococcus), particularly via the membrane attack complex. Complement activation liberates the anaphylatoxins C3a and C5a, which activate three distinct G-protein coupled receptors, C3aR, C5aR1 and C5aR2 (anaphylatoxin receptors, ATRs). We recently discovered that C5aR1 exacerbates the course of the disease, revealing a downside of complement in sepsis.

Modeling Neisseria meningitidis Infection in Mice: Methods and Logistical Considerations for Nasal Colonization and Invasive Disease.

The single greatest barrier to studying the lifestyle of Neisseria meningitidis stems from its exquisite adaptation to life in humans, a specialization which prevents it from infecting other animals. This barrier to modeling meningococcal infection has been overcome by the provision of factors that allow the meningococci to overcome one or more aspects of host restriction, including the use of mice expressing receptors that allow mucosal colonization and/or the inclusion of serum factors that facilitate meningococcal replication during disseminated meningococcal disease. Here we discuss these advances, consider variables that influence the outcome of infection, and detail the technical requirements to establish robust and reproducible nasal colonization or sepsis.

Differential influences of complement on neutrophil responses to Neisseria meningitidis infection.

The complement system is the primary innate immune determinant protecting against invasive diseases caused by the Gram-negative bacterium Neisseria meningitidis (Nme, meningococcus), as evidenced by the extreme susceptibility of individuals with complement deficiencies. In contrast, the role of phagocytes such as neutrophils is much less well understood, although they are recruited in great numbers to the cerebrospinal fluid during meningococcal meningitis. Here, we consider the interaction of Nme with primary human neutrophils using either purified cells or a whole blood model of infection.

Anticoagulants impact on innate immune responses and bacterial survival in whole blood models of Neisseria meningitidis infection.

Neisseria meningitidis (meningococcus) causes invasive diseases such as meningitis or septicaemia. Ex vivo infection of human whole blood is a valuable tool to study meningococcal virulence factors and the host innate immune responses. In order to consider effects of cellular mediators, the coagulation cascade must be inhibited to avoid clotting.

Complement C5a Receptor 1 Exacerbates the Pathophysiology of Sepsis and Is a Potential Target for Disease Treatment.

Sepsis caused by (meningococcus) is a rapidly progressing, life-threatening disease. Because its initial symptoms are rather unspecific, medical attention is often sought too late, i.e.

A native outer membrane vesicle vaccine confers protection against meningococcal colonization in human CEACAM1 transgenic mice.

Background: The effect of protein-based meningococcal vaccines on prevention of nasopharyngeal colonization has been difficult to investigate experimentally because a reliable animal colonization model did not exist.

Methods: Human CEACAM1 transgenic mice, which can be colonized by meningococci, were immunized IP with one of two meningococcal native outer membrane vesicle (NOMV) vaccines prepared from mutants with attenuated endotoxin (lpxL1 knockout) and over-expressed sub-family B Factor H-binding proteins (FHbp). Animals were challenged intranasally two weeks after the third dose with wild-type strain H44/76, or were treated IP with anti-NOMV serum before and during the bacterial challenge.

Sterilizing immunity elicited by Neisseria meningitidis carriage shows broader protection than predicted by serum antibody cross-reactivity in CEACAM1-humanized mice.

Neisseria meningitidis asymptomatically colonizes the human upper respiratory tract but is also the cause of meningitis and severe septicemia. Carriage or disease evokes an immune response against the infecting strain. Hitherto, we have known little about the breadth of immunity induced by natural carriage of a single strain or its implications for subsequent infectious challenge.

In vivo adaptation and persistence of Neisseria meningitidis within the nasopharyngeal mucosa.

Neisseria meningitidis (Nme) asymptomatically colonizes the human nasopharynx, yet can initiate rapidly-progressing sepsis and meningitis in rare instances. Understanding the meningococcal lifestyle within the nasopharyngeal mucosa, a phase of infection that is prerequisite for disease, has been hampered by the lack of animal models. Herein, we compare mice expressing the four different human carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) that can bind the neisserial Opa protein adhesins, and find that expression of human CEACAM1 is necessary and sufficient to establish intranasal colonization.

Invasive potential of nonencapsulated disease isolates of Neisseria meningitidis.

The capsule of Neisseria meningitidis is the major virulence factor that enables this bacterium to overcome host immunity elicited by complement and phagocytes, rendering it capable of surviving in blood. As such, nonencapsulated N. meningitidis isolates are generally considered nonpathogenic.