Hematogenous dissemination of pathogenic and non-pathogenic Leptospira in a short-term murine model of infection

Abstract

Leptospirosis is an emerging zoonosis caused by pathogenic Leptospira spp. Because rodents are natural hosts of Leptospira, rodent models of pathogenesis have been limited, but are valuable to understand infection in reservoir animals even in the absence of disease. Mouse models of infection provide advantages due to genetic tractability, so developing murine models of Leptospira infection is crucial for further understanding the biology of this organism. Previously our laboratory developed a short-term murine model of Borrelia burgdorferi hematogenous dissemination to investigate the role of adhesion proteins on bacterial survival and dissemination within a host. Here we adapt this model to Leptospira. C3H/HeJ mice are anesthetized, inoculated intravenously, and then bacteria are allowed to circulate for up to twenty-four hours. Mice are euthanized, perfused with saline, and tissues are harvested for culture and DNA purification. Bacterial burdens are determined by quantitative PCR. Reproducible burdens of bacteria were found in tissues upon inoculation with pathogens and non-pathogens, demonstrating the utility of this model to probe different Leptospira species and strains. Pathogenic L. interrogans has a significantly higher burden in blood, liver, kidney, and bladder at one-hour post-inoculation when compared to non-pathogenic L. biflexa. Colonization of the kidney is essential to the life cycle of pathogenic Leptospira in nature. Measurable burdens of non-pathogenic L. biflexa were found in numerous organs and live leptospires were recovered from blood samples for at least three hours post-inoculation, contrary to the previous belief that non-pathogenic leptospires are rapidly cleared. This short-term murine model of Leptospira hematogenous dissemination will allow for the interrogation of virulence factors potentially important for tissue colonization and evasion of host defenses, and represents a novel animal model for investigating determinants of Leptospira infection.

Heterologous production of the adhesin LIC13411 from pathogenic Leptospira facilitates binding of non-pathogenic Leptospira in vitro and in vivo

“…Data for L. interrogans sv. Manilae originally appears in an article published in this issue of Frontiers in Cellular and Infection Microbiology and represents three independent experiments per strain with 15 mice per group (except for liver where n = 13) (Surdel et al, 2022). Median ± range is plotted.…”

“…Previously our laboratory developed a short-term model of infection to interrogate adhesin proteins in B. burgdorferi. In a manuscript published in this issue of Frontiers in Cellular and Infection Microbiology, we describe the adaptation of this model to Leptospira (Surdel et al, 2022). To investigate the roles of the candidate adhesins LIC11574 and LIC13411 in vivo, mice were inoculated intravenously with each GOF strain and burdens in numerous organs were quantified by qPCR.…”

“…No. 204057) using primers for Leptospira 16srRNA (Supplementary Table 1) and conditions described in an article published in this issue of Frontiers in Cellular and Infection Microbiology (Surdel et al, 2022). Briefly, each DNA sample was quantified in triplicate or greater on a Bio-Rad CFX96 cycler.…”

“…Mouse experiments were performed and samples harvested after 1 h of incubation, as described in an article published in this issue of Frontiers in Cellular and Infection Microbiology (Surdel et al, 2022).…”

“…We show that pathogenic Leptospira have higher bacterial burdens in the blood, liver, kidney, and bladder, consistent with the kidney being the biologically essential site of colonization for pathogenic Leptospira. In addition, detectable burdens of L. biflexa were identified in numerous organs, suggesting that this model could be useful in interrogating GOF strains developed in non-pathogens (Surdel et al, 2022). Therefore, mice were inoculated with the GOF strains and organs harvested after 1 h. L. biflexa sv.…”