TLR4 competence and mouse models of leptospirosis.

Mice are slowly being accepted as alternative models for investigation of leptospiral infection. The strain most used to analyse sublethal disease (C3H-HeJ) expresses a gene in its immune cells that is hyporesponsive to leptospiral LPS and thus the model is deemed immunocompromised. To help resolve this valid scientific concern we did a study in which we compared infection with serovar Copenhageni Fiocruz in mice expressing fully competent (C3H-HeN, C57BL6) versus hyporesponsive mice (C3H-HeJ) over a period of two weeks.

Proteolytic activity of secreted proteases from pathogenic leptospires and effects on phagocytosis by murine macrophages.

Leptospirosis is a zoonosis caused by spirochete Leptospira. Pathogenic leptospires evade the Complement System, enabling their survival upon contact with normal human serum in vitro. In a previous study, we demonstrated that proteases secreted by pathogenic leptospires cleave several Complement proteins, including C3 and the opsonins C3b and iC3b.

Analysis of Complement Factor H gene polymorphisms and their association with clinical manifestations ofleptospirosis.

Leptospirosis is caused by pathogenic leptospires, posing a significant public health problem. Host susceptibility to Leptospira infection is a multifactorial trait, and the host's genetic background can influence both the establishment of infection and the severity of the disease. Complement Factor H (FH) plays a crucial role in the interaction between pathogenic bacteria and the host.

Murine C3 of the complement system affects infection by Leptospira interrogans.

Leptospirosis is an infectious neglected disease estimated to affect more than one million people worldwide each year. The Complement System plays a vital role in eliminating infectious agents. However, its precise role in leptospirosis remains to be fully understood.

A double edged-sword - The Complement System during SARS-CoV-2 infection.

In the past 20 years, infections caused by coronaviruses SARS-CoV, MERS-CoV and SARS-CoV-2 have posed a threat to public health since they may cause severe acute respiratory syndrome (SARS) in humans. The Complement System is activated during viral infection, being a central protagonist of innate and acquired immunity. Here, we report some interactions between these three coronaviruses and the Complement System, highlighting the central role of C3 with the severity of these infections.

Contribution of Complement System pathways to the killing of Leptospira spp.

The Complement System (CS) plays an important role in the immune response against leptospirosis and can be activated by the Alternative and Lectin Pathways (Innate Immunity) and by the Classical Pathway (Acquired Immunity). Here we analyzed a broad range of nonpathogenic and pathogenic Leptospira strains considering their interaction with each CS pathway. We determined bacterial survival rate and CS protein deposition in the presence of purified proteins, specific component depleted sera and NHS treated with the chelating agents EDTA (inhibits all three activation pathways) or EGTA (inhibits the Classical and Lectin Pathways).