Role of TLR4 in persistentLeptospira interrogansinfection: a comparativein vivostudy in mice

Abstract

<jats:title>Abstract</jats:title><jats:p>Toll-Like Receptor (TLR) 4 plays a central role in the control of leptospirosis and TLR4 deficiency results in lethal infection in mice. Human TLR4 however does not recognize <jats:italic>Leptospira</jats:italic> spp which may allow for their escape from immune recognition. We hypothesized that the replacement of murine TLR4 with human TLR4 may produce an immunocompetent mouse model of sublethal leptospirosis. We infected TLR4/MD-2 humanized transgenic mice (huTLR4) developed on a C57BL/6J TLR4/MD-2 double knock-out background with a sublethal dose of <jats:italic>L. interrogans</jats:italic> serovar Copenhageni (Leptospira). We found that Leptospira disseminated to target organs of huTLR4 mice as shown by the presence of spirochetes in blood, urine and kidney after infection. We did a comparative study between huTLR4 mice and wildtype C57BL/6J (muTLR4) to find out if the differences observed in the humanized TLR4 transgenic model were due to the transgene modification or to other factors. Replacing murine TLR4 with human TLR4 resulted in considerable higher shedding of Leptospira in urine in huTLR4 mice. Regarding inflammation of the kidney, MIP-2 and iNOS were significantly decreased in huTLR4 in comparison to muTLR4, whereas TNF-α and IFN-γ were increased, but there was no difference in RANTES that was increased in both groups of infected mice. In conclusion, our data suggests that human TLR4 may mediate higher susceptibility to leptospirosis that results in kidney pathology associated with downregulation of local MIP-2, antimicrobial iNOS and RANTES which are insuficient to restrict Leptospira and reduce shedding in urine. The TLR4 humanized mouse model of sublethal leptospirosis described is a novel tool to test therapies and vaccines against this neglected re-emerging zoonotic disease.</jats:p>

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

“…C3H/HeJ mice, a strain known to be susceptible to Leptospira, were selected for use in our short-term model of infection (Poltorak et al, 1998;Nally et al, 2005;da Silva et al, 2012;Richer et al, 2015;Shetty et al, 2021;Shetty et al, 2022). It has long been known that TLR4 is important in controlling leptospirosis, as mice lacking TLR4 are susceptible to acute disease (Pereira et al, 1998;Viriyakosol et al, 2006;Nair et al, 2020a). C3H/HeJ mice have a spontaneous proline to histidine mutation at residue 712 which produces a hyporesponsive TLR4, leading to susceptibility to Leptospira infection as well as limiting endotoxic shock induced by lipopolysaccharide (LPS) (Qureshi et al, 1999).…”

“…encode a unique LPS that leads to varied recognition by TLRs in humans and mice (Que-Gewirth et al, 2004;Nahori et al, 2005;Chassin et al, 2009). Importantly, the presence of either mouse or human TLR4 has been shown to be sufficient to control infection by Leptospira (Nair et al, 2020a). In addition to mouse strains, age, sex, and the route of infection contribute to variable disease kinetics induced by Leptospira (Pereira et al, 1998;Nally et al, 2005;Nair et al, 2020b;reviewed in Gomes-Solecki et al, 2017).…”

A Mouse Model of Sublethal Leptospirosis: Protocols for Infection with Leptospira Through Natural Transmission Routes, for Monitoring Clinical and Molecular Scores of Disease, and for Evaluation of the Host Immune Response

“…One of the drawbacks of the C3H‐HeJ mouse model is that, due to the point mutation in TLR4, this mouse is considered immunocompromised. The analogous hyporesponsiveness and non‐resposiveness of C3H‐HeJ and human TLR4 to Leptospira LPS led us to use humanized TLR4 transgenic C57BL‐6J mice to develop an immunocompetent mouse model of Leptospirosis (Nair, Soares Guedes, Hajjar, Werts, & Gomes‐Solecki, 2020). Either using C3H‐HeJ or humanized TLR4 C57BL‐6J, these mouse models of infection can only help increase our knowledge of Leptospira pathogenesis if they are adopted by the research community.…”

Comparative response of dendritic cells to pathogenic and non-pathogenic leptospira spp.

“…Although they are closely related strains, C3H/HeJ mice are characterized by hyporesponsiveness to lipopolysaccharide (LPS) because they have a single point mutation of LPS allele (Lps d ) in the gene encoding Toll-like receptor 4 (TLR4) compared to the C3H/HeN mice (87, 88) These revealed the crucial effects of TLR4 on leptospirosis pathogenesis. The disadvantages of C3H/HeJ mouse model are that it is considered slightly immunocompromised (89) and rather expensive. C3H/HeNJ mice, a result of hybridization mating between C3H/HeJ (TLR4 defective mice) and C3H/HeN (wild-type TLR4) mice, are commercially available at reasonable price.…”