Differential up-regulation of circulating soluble selectins and endothelial adhesion molecules in Sicilian patients with Boutonneuse fever

Anaphylatoxin signaling activates macrophages to control intracellular Rickettsia proliferation

IMPORTANCE

Pathogenic Rickettsia species are extremely dangerous bacteria that grow within the cytoplasm of host mammalian cells. In most cases, these bacteria are able to overpower the host cell and grow within the protected environment of the cytoplasm. However, a dramatic conflict occurs when Rickettsia encounter innate immune cells; the bacteria can "win" by taking over the host, or the bacteria can "lose" if the host cell efficiently fights the infection. This manuscript examines how the immune complement system is able to detect the presence of Rickettsia and alert nearby cells. Byproducts of complement activation called anaphylatoxins are signals that "activate" innate immune cells to mount an aggressive defensive strategy. This study enhances our collective understanding of the innate immune reaction to intracellular bacteria and will contribute to future efforts at controlling these dangerous infections.

New insight into immunity and immunopathology of Rickettsial diseases

Human rickettsial diseases comprise a variety of clinical entities caused by microorganisms belonging to the genera Rickettsia, Orientia, Ehrlichia, and Anaplasma. These microorganisms are characterized by a strictly intracellular location which has, for long, impaired their detailed study. In this paper, the critical steps taken by these microorganisms to play their pathogenic roles are discussed in detail on the basis of recent advances in our understanding of molecular Rickettsia-host interactions, preferential target cells, virulence mechanisms, three-dimensional structures of bacteria effector proteins, upstream signalling pathways and signal transduction systems, and modulation of gene expression. The roles of innate and adaptive immune responses are discussed, and potential new targets for therapies to block host-pathogen interactions and pathogen virulence mechanisms are considered.

Relative chemokine and adhesion molecule expression in Mediterranean spotted fever and African tick bite fever

OBJECTIVES

Mediterranean spotted fever (MSF) caused by Rickettsia conorii (R. conorii) is a potential lethal disease while African tick bite fever (ATBF) caused by Rickettsia africae is a self-limiting flu-like illness. We hypothesized that different inflammatory potential in endothelial cells could contribute to the different clinical features in these rickettsioses.

METHODS

We analyzed the effect of heat-inactivated R. africae and R. conorii on the mRNA and protein levels of monocyte chemoattractant protein (MCP)-1, interleukin (IL)-8 and adhesion molecules in endothelial cells. Serum samples from patients with MSF (n=16) and ATBF (n=15) were collected before and after therapy.

RESULTS

R. conorii induced a marked increase in MCP-1, IL-8, and adhesion molecules in endothelial cells, involving toll-like receptor 4 activation. In contrast, R. africae induced MCP-1 expression, but only modest or no responses were seen on IL-8 and adhesion molecules. Comparable to the in vitro response, levels of IL-8 and adhesion molecules showed no or only a modest increase in ATBF patients while these inflammatory markers were markedly elevated during MSF.

CONCLUSIONS

Our findings suggest a superior inflammatory potential of R. conorii as compared to R. africae in endothelial cells, potentially related to the more severe inflammation in MSF comparing ATBF.

Differential patterns of endothelial and leucocyte activation in 'typhus-like' illnesses in Laos and Thailand

Scrub typhus is responsible for a large proportion of undifferentiated fevers in south-east Asia. The cellular tropism and pathophysiology of the causative agent, Orientia tsutsugamushi, remain poorly understood. We measured endothelial and leucocyte activation by soluble cell adhesion molecule enzyme-linked immunosorbent assays in 242 Lao and Thai patients with scrub or murine typhus, leptospirosis, dengue, typhoid and uncomplicated falciparum malaria on admission to hospital. Soluble E-selectin (sE-selectin) levels were lowest in dengue, sL-selectin highest in scrub typhus with a high sE-selectin to sL-selectin ratio in leptospirosis patients. In scrub typhus patients elevated sL-selectin levels correlated with the duration of skin rash (P = 0.03) and the presence of eschar (P = 0.03), elevated white blood cell (WBC) count (P = 0.007), elevated lymphocyte (P = 0.007) and neutrophil counts (P = 0.015) and elevated levels of sE-selectin correlated with the duration of illness before admission (P = 0.03), the presence of lymphadenopathy (P = 0.033) and eschar (P = 0.03), elevated WBC (P = 0.005) and neutrophil counts (P = 0.0003). In comparison, soluble selectin levels in murine typhus patients correlated only with elevated WBC counts (P = 0.03 for sE-selectin and sL-selectin). Soluble intercellular adhesion molecule-1 and soluble vascular adhesion molecule-1 levels were not associated significantly with any clinical parameters in scrub or murine typhus patients. The data presented suggest mononuclear cell activation in scrub typhus. As adhesion molecules direct leucocyte migration and induce inflammatory and immune responses, this may represent O. tsutsugamushi tropism during early dissemination, or local immune activation within the eschar.

Mechanisms of immunity against rickettsiae. New perspectives and opportunities offered by unusual intracellular parasites

Investigation of the biology, pathology and immunology of rickettsial diseases offers new insights useful not only for the field of rickettsiology, but more importantly for the understanding of general principles of host-intracellular parasite relationships and, in particular, the immune interaction between endothelial cells and immune cells in the context of infection.

Soluble adhesion molecules, cytokines and cellular markers in serum in patients with acute infections

The aim of this study was to evaluate the diagnostic capacity of a number of blood components such as soluble adhesion molecules, interleukin-6 (IL-6), myeloperoxidase (MPO) and lysozyme in the distinction of acute bacterial and viral infections. Blood was taken from 115 acutely infected patients at admission before any treatment and in some cases on several consecutive days. 35 of the patients had a definite viral cause for their infection and 66 a bacterial cause. All variables were raised in patients with acute bacterial infections. Soluble vascular cell adhesion molecule-1 (sVCAM-1), sE-selectin, lysozyme and MPO were also raised in acute viral infections, but for sE-selectin and MPO less so than in bacterial infections. Evaluation of the diagnostic power showed that for MPO and IL-6 at cut-offs of 1300 microg/l and 100 ng/l, respectively, the positive predictive value was 97% and 100% and the negative predictive value 78% and 76%, respectively, in the classification of acute bacterial infections. In the distinction between viral or bacterial causes of acute infections in otherwise healthy subjects serum measurements of MPO and IL-6 are valuable tools and should be considered as diagnostic aids in the routine setting. The soluble adhesion molecules did not offer any further information in this respect.

Cytokine modifications after tension-free hernioplasty or open conventional inguinal hernia repair

BACKGROUND

The purpose of this study was to evaluate the involvement of proinflammatory cytokines (interferon-gamma [INF-gamma], interleukin [IL]-6) and anti-inflammatory cytokines (IL-4, IL-l0, IL-13) in patients undergoing Lichtenstein tension-free hernioplasty (LH) using polypropylene prosthetic materials or conventional Bassini hernia (BH) repair.

METHODS

Thirty-five male patients (age range 25 to 60 years) with unilateral inguinal hernia without complications or recurrence were included in this study. Randomly, patients underwent conventional operation and had their inguinal hernia repair performed with polypropylene mesh. Peripheral venous blood samples were collected 24 hours prior to surgery and then 6, 24, 48, and 168 hours postoperatively. Fifteen healthy controls were included.

RESULTS

We present evidence that LH patients showed both an increased serum level of Thelper 1 (Th1)-like cytokines (IFN-gamma) and an increase in Thelper 2 (Th2)-like cytokines (IL-6 and IL-l0), associated with a slight reduction of peripheral blood mononuclear cells (PBMC) producing IL-6 and a normal level of PBMC producing IFN-gamma, IL-l0, IL-13, and IL-4. Whereas BH patients showed in part an amplification of Th2-like cells, characterized by the sustained serum production of IL-6 and IL-l0, associated with an increase in IL-l0 secreted by in vitro stimulated PMBC.

CONCLUSIONS

Our data show that LH is associated with a higher production of inflammatory cytokines (IFN-gamma and IL-6) compared with BH, likely induced by the presence of the polypropylene prostheses.