Natural IgM antibodies in the immune defence against neoehrlichiosis

Neoehrlichia mikurensis-A New Emerging Tick-Borne Pathogen in North-Eastern Poland?

Neoehrlichia mikurensis is a new emerging tick-borne Gram-negative bacterium, belonging to the family Anaplasmataceae, the main vector of which in Europe is the tick Ixodes ricinus. N. mikurensis is responsible for neoehrlichiosis, occurring mostly in patients with underlying diseases. In the present study, a total of 348 I. ricinus and Dermacentor reticulatus ticks collected in north-eastern Poland were analyzed for the prevalence of N. mikurensis. A total of 140 questing ticks (124 of I. ricinus ticks and 16 D. reticulatus) collected with the flagging method and 208 ticks (105 and 103 I. ricinus and D. reticulatus, respectively) removed from dogs were selected for the study. cDNA (questing ticks) and total DNA (questing and feeding ticks) were analyzed by qPCR targeting the 16S rRNA gene of N. mikurensis. Positive samples were further analyzed by nested PCR and sequencing. The prevalence differed between ticks collected from vegetation (19.3%; 27/140) and ticks removed from dogs (6.7%; 14/208). The presence of the pathogen in questing and feeding D. reticulatus ticks was proven in Poland for the first time. In summary, our research showed that infections of ticks of both the most common tick species I. ricinus and D. reticulatus in north-eastern Poland are present and ticks collected from urban areas were more often infected than ticks from suburban and natural areas. The detection of N. mikurensis in I. ricinus and D. reticulatus ticks from north-eastern Poland indicates potential transmission risk for tick-bitten humans at this latitude.

Neoehrlichia mikurensis Causing Thrombosis and Relapsing Fever in a Lymphoma Patient Receiving Rituximab

Neoehrlichia (N.) mikurensis, an intracellular tick-borne bacterium not detected by routine blood culture, is prevalent in ticks in Scandinavia, Central Europe and Northern Asia, and may cause long-standing fever, nightly sweats, migrating pain, skin rashes and thromboembolism, especially in patients treated with rituximab. The multiple symptoms may raise suspicion of both infection, inflammation and malignancy, and lead in most cases to extensive medical investigations across many medical specialist areas and a delay of diagnosis. We describe a complex, albeit typical, case of neoehrlichiosis in a middle-aged splenectomised male patient with a malignant lymphoma, receiving treatment with rituximab. The multifaceted clinical picture associated with this tick-borne disease is addressed, and longitudinal clinical and laboratory data, as well as imaging, are provided. Longstanding relapsing fever in combination with thrombosis in superficial and deep veins in an immunocompromised patient living in a tick-endemic region should raise the suspicion of the emerging tick-borne disease neoehrlichiosis. Given the varied clinical presentation and the risk of delay in diagnosis and treatment, we believe it is important to raise clinicians' awareness of this emerging infection, which is successfully treated with doxycycline.

Natural IgM antibodies inhibit microvesicle-driven coagulation and thrombosis

Thrombosis and its associated complications are a major cause of morbidity and mortality worldwide. Microvesicles (MVs), a class of extracellular vesicles, are increasingly recognized as mediators of coagulation and biomarkers of thrombotic risk. Thus, identifying factors targeting MV-driven coagulation may help in the development of novel antithrombotic treatments. We have previously identified a subset of circulating MVs that is characterized by the presence of oxidation-specific epitopes and bound by natural immunoglobulin M (IgM) antibodies targeting these structures. This study investigated whether natural IgM antibodies, which are known to have important anti-inflammatory housekeeping functions, inhibit the procoagulatory properties of MVs. We found that the extent of plasma coagulation is inversely associated with the levels of both free and MV-bound endogenous IgM. Moreover, the oxidation epitope-specific natural IgM antibody LR04, which recognizes malondialdehyde adducts, reduced MV-dependent plasmatic coagulation and whole blood clotting without affecting thrombocyte aggregation. Intravenous injection of LR04 protected mice from MV-induced pulmonary thrombosis. Of note, LR04 competed the binding of coagulation factor X/Xa to MVs, providing a mechanistic explanation for its anticoagulatory effect. Thus, our data identify natural IgM antibodies as hitherto unknown modulators of MV-induced coagulation in vitro and in vivo and their prognostic and therapeutic potential in the management of thrombosis.

'Candidatus Neoehrlichia mikurensis' in Europe

'Candidatus Neoehrlichia mikurensis' is an uncultured emerging bacterium that is provisionally included in the family Anaplasmataceae. In Europe, it is transmitted by Ixodes ricinus ticks. Rodents are the reservoirs. It is widely distributed in mammals (both wild and domestic) and birds. It causes an inflammatory disease in humans with underlying diseases, but the microorganism also affects immunocompetent individuals in which asymptomatic infection has been recognized. A high degree of suspicion and the use of molecular tools are needed for the correct diagnosis. Efforts to cultivate it and to investigate its pathogenesis should be a priority.