Virulent Leptospira interrogans Induce Cytotoxic Effects in Human Platelets in vitro Through Direct Interactions

Abstract

Leptospirosis is a prevalent zoonotic disease, caused by bacteria of the genus Leptospira. Leptospirosis frequently leads to hemostatic disturbances, and the severe cases are marked by hemorrhages and low platelet number in circulation, which is associated with the patients' poor outcomes. Nevertheless, Leptospiraplatelet interactions remain poorly explored. In this study, we performed a series of in vitro experiments evaluating whether leptospires induce human platelet aggregation, activation, and morphological changes. Platelets were incubated with virulent L. interrogans and the platelet outcomes were assessed by aggregometry, flow cytometry, and scanning and transmission electron microscopy. Our results show that leptospires alone do not induce platelet aggregation and activation, and induce platelet cytotoxic effects instead, by clearly inducing platelet disruption and detachment. We show for the first time that virulent leptospires do interact directly with platelets, an event that could trigger pathophysiological effects during the infection. This study might serve as a basis for the development of novel treatments for the disease.

Case of leptospirosis causing pancytopenia

“…It is thought a combination of (1) disseminated intravascular activation (DIC), (2) platelet death induced by Leptospiral toxins, (3) decreased production of platelets by the bone marrow megakaryocytes, (4) platelet overactivation by bacterial components leading to platelet consumption and (5) platelet clearance mediated by platelet autoantibodies. 5 Pancytopenia is reported in only a number of cases as a haematological manifestation in Leptospiral infections, and the true incidence is unknown. A case series described in Israel reported pancytopenia in 28% of patients.…”

Pulmonary haemorrhage as the earliest sign of severe leptospirosis in hamster model challenged with Leptospira interrogans strain HP358

“…It was reported that pathogenic Leptospira spp. could bind to platelets and induce cytotoxic effects resulting in dysfunction and clearance of platelets [ 43 – 47 ]. A low level of platelets noticed in the present study could also play important role in the haemorrhagic presentation as observed in both animal [ 46 ] and human leptospirosis [ 48 – 50 ].…”

Updated ACVIM consensus statement on leptospirosis in dogs

“…Pathogenic leptospires have direct cytotoxic effects on platelets, with platelet destruction and de-adherence noted in vitro. 53 Aseptic meningitis has been described in up to 25% of humans with leptospirosis, 54 and appears to occur in dogs. 55 Histopathological lesions of LPHS lung tissue are characterized by various degrees of intra-alveolar hemorrhage in the absence of a marked inflammatory cell infiltrate or vasculitis.…”

“…Liver dysfunction results from disruption of hepatocyte intercellular junctions by spirochetes, with leakage of bile into the circulation which is reflected biochemically as a cholestatic hepatopathy. Pathogenic leptospires have direct cytotoxic effects on platelets, with platelet destruction and de‐adherence noted in vitro 53 . Aseptic meningitis has been described in up to 25% of humans with leptospirosis, 54 and appears to occur in dogs 55 .…”