Eyedrop Inoculation Causes Sublethal Leptospirosis in Mice

Abstract

Leptospirosis is potentially a fatal zoonosis acquired by contact of skin and mucosal surfaces with soil and water contaminated with infected urine. We analyzed the outcome of infection of C3H/HeJ mice with Leptospira interrogans serovar Copenhageni using an enzootic mode of transmission, the conjunctival route. Infection led to weight loss and L. interrogans dissemination from blood to urine, and spirochetes were detected in blood and urine simultaneously. The infectious dose that led to consistent dissemination to kidney after conjunctival infection was ϳ10 8 leptospires. Interestingly, a lower number of spirochetes appeared to colonize the kidney, given that we quantified ϳ10 5 and ϳ10 leptospires per l of urine and per g of kidney, respectively. Leptospira-specific IgM and IgG were detected at 15 days postinfection, and isotyping of the Ig subclass showed that the total IgG response switched from an IgG1 response to an IgG3 response after infection with L. interrogans. Histological periodic acid-Schiff D staining of infected kidney showed interstitial nephritis, mononuclear cell infiltrates, and reduced size of glomeruli. Quantification of proinflammatory immunomediators in kidney showed that keratinocyte-derived chemokine, macrophage inflammatory protein 2, RANTES, tumor necrosis factor alpha, gamma interferon, and interleukin-10 were upregulated in infected mice. We show that the kinetics of disease progression after infection via the ocular conjunctiva is delayed compared with infection via the standard intraperitoneal route. Differences may be related to the number of L. interrogans spirochetes that succeed in overcoming the natural defenses of the ocular conjunctiva and transit through tissue.

The route of infection with Leptospira interrogans serovar Copenhageni affects the kinetics of bacterial dissemination and kidney colonization

“…We used Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130 (henceforth Leptospira), culture passage 2 after hamster infection, originally isolated from a patient in Brazil. Leptospira was cultured as previously described [10] and enumerated by dark-field microscopy (Zeiss USA, Hawthorne, NY) that was confirmed by qPCR (StepOne Plus, Life Technologies, Grand Island, NY).…”

“…In this study, we used the C3H-HeJ sublethal model of leptospirosis to determine how exposure to L. interrogans serovar Copenhageni FioCruz L1-130 through the transdermal and oro-nasal routes of infection affect the timing of bacterial dissemination to blood and urine as well as the associated clinical outcomes and kidney pathology. Data are discussed taking into consideration our previous findings using the other route of natural infection, the ocular conjunctiva, CJ [10].…”

“…entrance of Leptospira through skin and mucosa, was recently evaluated in rats and it was found that mucosal infection led to kidney colonization associated with higher excretion of Leptospira [3]. Work on mouse models of leptospirosis using adult mice suggested that serovar, inoculum dose and route of infection affected the kinetics of disease progression [4], [5], [6], [7], [8], [9], [10]. Others have observed the same association between inoculum dose and lethal leptospirosis in hamsters [11], [12].…”

Recent findings related to immune responses against leptospirosis and novel strategies to prevent infection

“…Eye drop inoculation is an interesting route of infection since it mimics a natural route of infection and is considered more physiological than intraperitoneal infection, which bypasses the natural defenses of the skin and mucosa. Recently, the Gomes-Solecki group showed in the C3H/HeJ TLR4 deficient mouse model that eye inoculation with 10 8 L. interrogans leads to acute leptospirosis with kidney lesions and colonization, although with a delay compared to the intraperitoneal route [46].…”

Murine Models for Leptospirosis Kidney Disease

“…Nevertheless, the intraperitoneal route of inoculation does not reflect the entrance of leptospires and the first phases of infection. Recently, a novel mouse model using sensitive C3H/HeJ mice infected through the conjunctival route of inoculation has shown that leptospires disseminate in blood, although with a delay compared to the intraperitoneal route, and provoke nephritis in the kidney, with glomerulus size reduction [18] . This novel model is interesting since it validates the peritoneal model.…”