An investigation on vertical transmission of Leishmania infantum in experimentally infected dogs and assessment of offspring's infectiousness potential by xenodiagnosis

Dogs are the main reservoir host of Leishmania infantum, etiologic agent of human visceral leishmaniasis (HVL) and canine visceral leishmaniasis (CVL). Transmission of L. infantum to humans and dogs is mainly through the bite of infected sand flies. In the Western Mediterranean basin, Phlebotomus perniciosus is the main vector of L. infantum. However, occasional vertical transmission of L. infantum has been reported. This study investigated L. infantum vertical transmission in offspring of experimentally infected dogs. Among 14 surviving puppies from three female beagle dogs that developed CVL following an experimental infection with L. infantum, one was tested positive by indirect immunofluorescence antibody test, by PCR and by xenodiagnosis with a high parasite burden in the spleen at 14 months old. None of the remaining puppies were tested positive for L. infantum. These findings strongly suggest that infected puppies following vertical transmission can sustain infection and contribute in infecting sand flies with L. infantum. Any strategy for controlling CVL should take into consideration the vertical transmission of L. infantum.

Evaluation of antileishmanial, cytotoxic and antioxidant activities of essential oils extracted from plants issued from the leishmaniasis-endemic region of Sned (Tunisia)

In this study, we tested 10 essential oils (EOs) extracted from 10 plants issued from Sned region (Tunisia) to evaluate both their leishmanicidal effects against Leishmania major and L. infantum, and their cytotoxicity against murine macrophage cell line RAW 264.7 (ATCC, TIB-71). The antioxidant activity was also monitored by the DDPH method, while the chemical composition of active EO was assessed by GC-MS analysis. The results showed that the EOs obtained from Thymus hirtus sp. algeriensis (rich on monoterpenoids, especially linalool at 17.62% and camphor at 13.82%) is significantly active against both L. major and L. infantum, whereas Ruta chalepensis EO (rich on 2-undecanone at 84.28%) is only active against L. infantum. Both oil extracts showed low cytotoxicity towards murine macrophages. The characteristic ratios (IC₈₀ Raw264.7 cells/IC₅₀ L. infantum and IC₈₀ Raw264.7 cells/IC₅₀ L. major) were, respectively, 2.7 and 1.57 for T. hirtus sp. algeriensis, and 1.34 and 0.19 for R. chalepensis. However, when measuring the antioxidant effects (DDPH method), the two latter EOs presented a moderate 2,2-diphenyl-2-picrylhydrazyl hydrate scavenging effects compared to EOs from Eucaliptus globulus, Pinus halepensis, Pituranthos tortuosus, Rosmarinus officinalis, Tetraclinis articulata or to BHT.

Differences in the salivary effects of wild-caught versus colonized Phlebotomus papatasi (Diptera: Psychodidae) on the development of zoonotic cutaneous leishmaniasis in BALB/c mice

Preimmunization of mice with salivary gland homogenate (SGH) of long-term colonized (F29) female Phlebotomus papatasi Scopoli (Diptera: Psychodidae) induced protection against Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae) co-inoculated with the same type of SGH. In contrast, preimmunization of mice with SGH of wild-caught female P. papatasi did not confer protection against L. major co-inoculated with the same type of SGH. Similarly, SGH from recently colonized (F1) female P. papatasi did not protect mice against L. major. These results suggest that when developing a sand fly saliva-based vaccine, the natural vector populations should be considered.

[Immuno-modulating effects of eukaryotic expressing vectors of IL-12 and GM-CSF associated to DNA-based vaccination against experimental cutaneous leishmaniasis in BALB/c mouse]

Different works of DNA based vaccination against leishmaniasis highlight the complexity of the induced immune responses to fight against the disease. In this work, we exploited the capacity of IL-12 and GMC-SF to activate immune cell mediators and effectors to induce a Th1 response, more capable of clearing the parasite. To generate these immunomodulating activities, we associated eukaryotic expressing vectors of murine IL-12 and GMC-SF to several DNA based vaccine candidates encoding to several L. (L.) major antigens, in the BALB/c mouse. When mice were challenged with a high parasitic load in the hind footpad, no additional protective effect could be generated. However, when the challenge was carried out in the inner face of the ear with a small parasitic load, the association of plasmids encoding to IL-12 and GMC-SF to DNA based vaccination, the protective effects were increased.