Sand fly saliva: effects on host immune response and Leishmania transmission

Abstract

Abstract. The feeding success of sand flies (Diptera: Phlebotominae) is linked to the vast array of pharmacological substances in their saliva, which interferes with the host haemostasis and immune response. Modification of feeding site plays also an important role in Leishmania transmission. In naive hosts, co-inoculation of saliva and Leishmania parasites increases the chance of successful transmission. Disease exacerbation seems to be associated with enhanced production of type 2 cytokines and selective inhibition of some macrophage functions including the production of NO and H 2 O 2 . On the other hand, hosts repeatedly exposed to sand fly bites develop anti-saliva immune response that results in a protection against Leishmania infection. This led to a new interesting approach to anti-Leishmania vaccine -using salivary components to block parasite transmission. The review is therefore focused on the interactions that run between immunomodulatory molecules in sand fly saliva and host immune response, with the impact on Leishmania infection development. Recent studies revealed that saliva-based vaccine for leishmaniasis might be effective and feasible, however, several questions still require to be solved. The knowledge based on experimental mouse model cannot be fully extrapolated to dogs or humans and due to differences in salivary antigens between sand fly species the protective effect is species-specific. On the other hand, the specificity of salivary antigens enables the use of anti-saliva antibodies for monitoring the exposure of hosts to sand fly bites and might be used as a marker of risks for Leishmania transmission in endemic areas.

Immunity to a salivary protein of a sand fly vector protects against the fatal outcome of visceral leishmaniasis in a hamster model

“…Notably, the plasmids that were not immunogenic in hamsters were able to produce a cellular or antibody response in mice (data not shown). This finding suggests that the absence of an immune response to some of these plasmids in hamsters may be caused by host specificity (9). However, we cannot exclude a dose-related effect caused by differential expression of plasmids after hamster immunizations.…”

“…Saliva contains a variety of potent and pharmacologically active components that favorably change the environment at the feeding site (4-7). Exposure to sand fly bites or salivary proteins results in strong cellular and/or humoral immunity specific to these components (8)(9)(10)(11). In animal models of CL, mice immunized with Phlebotomus papatasi salivary gland homogenate (SGH) or preexposed to uninfected sand fly bites were protected against Leishmania major infection delivered via needle inoculation (2) or by infected sand flies (12).…”

Measurement of Recent Exposure to Phlebotomus argentipes, the Vector of Indian Visceral Leishmaniasis, by Using Human Antibody Responses to Sand Fly Saliva

“…This saliva is known to contain a variety of anti-hemostatic, vasodilatory, and immunomodulatory compounds 13. Therefore, saliva will always be present during a bite from either an uninfected or infected sand fly.…”

Comparative genomics of Tunisian Leishmania major isolates causing human cutaneous leishmaniasis with contrasting clinical severity

“…Mechanisms and determinants of clinical severity and pathogenicity are not fully understood and might be determined by factors related to the parasite (Banuls et al, 2011; Stuart et al, 2008), the vector (Murray et al, 2005; Rohousova and Volf, 2006) and the host genetic background and immune responses (Kane and Mosser, 2000; Sakthianandeswaren et al, 2009; Schriefer et al, 2008). In Tunisia, a couple of studies showed that various L. major isolates differ in their experimental pathogenicity when injected into the footpad of the genetically susceptible BALB/c mice (Kebaier et al, 2001 and Attia, unpublished data).…”