Controle da Leptospirose: imunização passiva ou ativa em modelo animal e diferenças na severidade da doença entre machos e fêmeas

Abstract

Leptospirosis is a widespread zoonotic disease caused by pathogenic spirochetes of the genus Leptospira affecting both humans and animals. The estimates are about 1.03 million cases and 58,900 deaths per year worldwide, and the mortality rate varies from 10% to 70%. In this study, we aimed to propose three potentially effective approaches to help in the control of leptospirosis. 1) Differences among males and females hamsters infected with different doses of L. interrogans were evaluated. Groups of 12 males and 12 females hamsters were infected with 103, 5 x 103, and 104 L. interrogans. Females have shown to be more resistant to the leptospirosis, regarding survival and severity of the disease compared to the males. The males showed a higher level of proinflammatory and inflammatory cytokines and chemokines, a higher burden of bacteria in the kidney and higher tissue damage when compared to the females exposed to the same conditions. 2) The effectiveness and proctection of two different monoclonal antibodies (mAbs) against the OMP LipL32 were tested through in vitro and in vivo passive immunization assays. Goups of 8-week-old female hamsters were immunized with 250 μg mAbs anti-LipL32, and three different immunization strategies were tested. Hamsters inoculated with the mAb3 6 hours prior to the challenge presented a significant survival rate of 61.11% (P < 0.0001). A significant reduction in lung damage (P < 0.05) was observed in the groups that presented survivors. 3) C3H/HeJ mice were orally vaccinated with Escherichia coli expressing the proteins LemA (Ec-LemA), LipL32 (Ec-LipL32) and TolC (Ec-TolC) submitted to sublethal challenge with L. interrogans. As a result, we found that groups vaccinated with Ec-LemA and Ec-LipL32 showed a reduction in the number of L. interrogans shedding, reduction in the bacterial burden in the blood and reduction in weight loss when compared to the control groups. Our results suggest 1) male hamsters infected with L. interrogans are more susceptible to succumb or develop a more severe disease when compare to the females. The immune system orchaestrates a chemokine and cytokine storm that in a prolonged production promotes tissue (renal) damage leading to increase the severity of the disease and further dead of the animals. 2) both monoclonal antibodies anti-LipL32 have potential to inhibit the growth of L. interrogans in vitro, and in vivo significantly protecting hamsters against lethal challenge, only when administered prior to exposure to the pathogen. 3) the oral vaccination of mice showed a promising indication that it is possible to eliminate or at least reduce the bacterial shedding into the urine of mice infected with L. interrogans. Despite the positive data, the repetition of this experiment needs to be performed in order to reach statistical significance to support the data obtained so far.