Publication details
Dual role of anti-vector saliva immunity on the outcome of Leishmania infection
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| Year of publication | 2022 |
| Type | Conference abstract |
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| Citation | |
| Description | Leishmaniases are diseases caused by intracellular protozoan parasites of the genus Leishmania. The parasite multiply in monocytes and macrophages and is transmitted by female sand flies during blood feeding. Exposure to vector saliva prior to Leishmania infection has been shown to protect against severe leishmaniasis. This effect is believed to be related to anti-sand fly saliva delayed type hypersensitivity reaction in sensitised host, leading to a more effective immune defense against the Leishmania parasites. The aim of this study was to determine whether the disease outcome might be affected by the timing between the last exposure to vector saliva and Leishmania infection, a factor neglected in so far published studies. Experiments were performed on BALB/c mice sensitised by Phlebotomus duboscqi bites and subsequently co-injected by Leishmania major and P. duboscqi salivary gland lysate, 48 hours or one week after the last exposure to P. duboscqi bites. In agreement with published studies, sensitised mice infected 1 week after the last P. duboscqi exposure were protected against severe leishmaniasis as demonstrated by smaller dermal lesions and lower parasite load in the affected tissue, when compared to non-sensitised controls. Such effect was, however, diminished in mice with shorter timespan (48 hours) between the last exposure to P. duboscqi saliva and the L. major inoculation. Moreover, several immunological parameters were altered by this timing, such as levels of anti-P. duboscqi and anti-L. major specific antibodies as well as the presence of the effector cells controlling Leishmania infection - neutrophils and M1 macrophages. In summary, our results suggest that the disease outcome is strongly influenced by the ongoing anti-vector saliva immune response at the site of Leishmania transmission. The timespan between the last exposure to vector saliva of the sensitised host and the Leishmania transmission is an important, yet neglected, factor affecting the leishmaniasis outcome by changing the host skin immune microenvironment. The understanding of this phenomenon might affect the implementation of control programs, including leishmaniasis vaccine development. |