Vaccination with Leptospiral Outer Membrane Lipoprotein LipL32 Reduces Kidney Invasion of Leptospira interrogans Serovar Canicola in Hamsters

Abstract

bThe Leptospira interrogans vaccines currently available are serovar specific and require regular booster immunizations to maintain protection of the host. In addition, a hamster challenge batch potency test is necessary to evaluate these vaccines prior to market release, requiring the use of a large number of animals, which is ethically and financially undesirable. Our previous work showed that the N terminus of the outer membrane protein LipL32 was altered in Leptospira interrogans serovar Canicola vaccines that fail the hamster challenge test, suggesting that it may be involved in the protective immune response. The aim of this study was to determine if vaccination with LipL32 protein alone could provide a protective response against challenge with L. interrogans serovar Canicola to hamsters. Recombinant LipL32, purified from an Escherichia coli expression system, was assessed for protective immunity in five groups of hamsters (n ‫؍‬ 5) following a challenge with the virulent L. interrogans serovar Canicola strain Kito as a challenge strain. However, no significant survival against the L. interrogans serovar Canicola challenge was observed compared to that of unvaccinated negative controls. Subsequent histological analysis revealed reduced amounts of L. interrogans in the kidneys from the hamsters vaccinated with recombinant LipL32 protein prior to challenge; however, no significant survival against the L. interrogans serovar Canicola challenge was observed compared to that of unvaccinated negative controls. This finding corresponded to a noticeably reduced severity of renal lesions. This study provides evidence that LipL32 is involved in the protective response against L. interrogans serovar Canicola in hamsters and is the first reported link to LipL32-induced protection against kidney invasion.

A Live Attenuated Vaccine Model Confers Cross-Protective Immunity Against Different Species ofLeptospiraspp.

“…Given the limitations of the whole-cell vaccines currently in use, identifying the perfect protein candidate has been a major effort in the field of vaccine development for leptospirosis 3 . Immunization with Lig proteins or LipL32 2,38,39 has been shown to confer protection, albeit not cross-protective immunity, against experimental infection. However, efficacy results have been proven difficult to replicate 2,40 .…”

Leptospiral outer membrane protein LipL32 induces inflammation and kidney injury in zebrafish larvae

“…In hamster model of leptospirosis, immunohistochemical analyses of L. kirschneri–infected kidneys have demonstrated the intense LipL32 expression in proximal tubule cells and the interstitium 16 . Vaccination with LipL32 reduces the severity of kidney inflammation in the hamsters infected with L. interrogans serovar Canicola in hamsters 36 . In this study, we demonstrated that the ectopic expression of LipL32 directly induced an inflammatory reaction and caused kidney injury, suggesting that LipL32 is a virulence factor and plays an important role in mediating the pathogenesis of renal injury in leptospirosis 37 .…”

Leptospiral major outer membrane protein

“…The results of the experiment indicated that LipL32 may have a protective effect against the kidney invasion by the pathogen; histopathological analysis of kidneys indicated that the number of pathogens in the kidney was less in the immunized animals compared with the control. They also reported significant survival of the immunized group [34].…”

“…The heat-labile endotoxin of E. coli further improved the immune response and protected the hamsters when challenged with the pathogenic strain. Humphryes et al [34] used LipL32 expressed in E. coli to immunize hamsters and challenged them with virulent Leptospira interrogans serovar Canicola strain Kito. The results of the experiment indicated that LipL32 may have a protective effect against the kidney invasion by the pathogen; histopathological analysis of kidneys indicated that the number of pathogens in the kidney was less in the immunized animals compared with the control.…”