The OmpL37 Surface-Exposed Protein Is Expressed by Pathogenic Leptospira during Infection and Binds Skin and Vascular Elastin

Abstract

Pathogenic Leptospira spp. shed in the urine of reservoir hosts into freshwater can be transmitted to a susceptible host through skin abrasions or mucous membranes causing leptospirosis. The infection process involves the ability of leptospires to adhere to cell surface and extracellular matrix components, a crucial step for dissemination and colonization of host tissues. Therefore, the elucidation of novel mediators of host-pathogen interaction is important in the discovery of virulence factors involved in the pathogenesis of leptospirosis. In this study, we assess the functional roles of transmembrane outer membrane proteins OmpL36 (LIC13166), OmpL37 (LIC12263), and OmpL47 (LIC13050), which we recently identified on the leptospiral surface. We determine the capacity of these proteins to bind to host tissue components by enzyme-linked immunosorbent assay. OmpL37 binds elastin preferentially, exhibiting dose-dependent, saturating binding to human skin (Kd, 104±19 nM) and aortic elastin (Kd, 152±27 nM). It also binds fibrinogen (Kd, 244±15 nM), fibrinogen fragment D (Kd, 132±30 nM), plasma fibronectin (Kd, 359±68 nM), and murine laminin (Kd, 410±81 nM). The binding to human skin elastin by both recombinant OmpL37 and live Leptospira interrogans is specifically enhanced by rabbit antiserum for OmpL37, suggesting the involvement of OmpL37 in leptospiral binding to elastin and also the possibility that host-generated antibodies may promote rather than inhibit the adherence of leptospires to elastin-rich tissues. Further, we demonstrate that OmpL37 is recognized by acute and convalescent leptospirosis patient sera and also by Leptospira-infected hamster sera. Finally, OmpL37 protein is detected in pathogenic Leptospira serovars and not in saprophytic Leptospira. Thus, OmpL37 is a novel elastin-binding protein of pathogenic Leptospira that may be promoting attachment of Leptospira to host tissues.

Characterization of Three Novel Adhesins of Leptospira interrogans

“…The high affinity of Lsa23 to laminin (K D = 25.08 ± 4.1 nM), a value of the same order of magnitude as a described Lsa66 adhesin. 15 The K D values of Lsa26 and Lsa36 are similar to the ones described for LenB, 46 TlyC, 47 OmpL37, 48 Lsa20, 16 Lsa33, and Lsa25 17 and Lsa30 18 with the same ligand. PLG acquisition and PLA generation has been reported for several pathogens, including the spirochetes Borrelia spp.…”

OmpL1 Is an Extracellular Matrix- and Plasminogen-Interacting Protein of Leptospira spp

“…Indeed, the OmpL1 protein exhibits extracellular matrix-binding properties. This protein binds laminin and plasma fibronectin, in contrast to the previously reported Lsa24 (4), Lsa27 (38), and Lsa20 (44) adhesins, which are laminin-binding adhesins, but similar to other previously reported adhesins, namely, Len family proteins (64), the LigA and LigB proteins (12), Lsa21 (2), LipL32 (27,28), TlyC (10), OmpL37 (53), and Lsa66 (49), which showed broader-spectrum binding with ECM. The calculated K D values for the binding of OmpL1 to laminin and to plasma fibronectin (2,099.93 Ϯ 871.04 and 1,239.23 Ϯ 506.85 nM, respectively) are, however, higher than the K D values obtained with Lsa66 and the same ECM components (55.4 Ϯ 15.9 nM and 290.8 Ϯ 11.8 nM) (49).…”

“…It was reported previously that several recombinant proteins (4,44,49,53) exhibit an inhibitory effect on the binding of leptospires to PLG and ECM macromolecules. We thus carried out similar experiments to evaluate whether OmpL1 has a similar effect on the adherence of leptospires to laminin, PLG, and plasma fibronectin.…”

Bacterial adhesion to animal tissues: protein determinants for recognition of extracellular matrix components

“…While structure-function analysis remains to be performed, laminin binding has been reported for several additional proteins, e.g. EhaB (enterohemorrhagic E. coli autotransporteur A) (Wells et al, 2009), Tp0136 (Treponema pallidum protein encoded by locus tp0136) (Brinkman et al, 2008), OmpL47 (outer membrane protein of Leptospira of 47 kDa) (Pinne et al, 2010) or Lsa24 (leptospiral surface adhesin of 24 kDa), Lsa27 and Lsa63 (Vieira et al, 2010).…”

“…In LigB, the Ig-like repeats are involved in chargecharge interactions with elastin (Lin et al, 2009). While structure-function analysis is awaited, OmpL37 demonstrates a pronounced specificity for elastin (Pinne et al, 2010).…”