Lack of Protection of Pre-Immunization with Saliva of Long-Term Colonized Phlebotomus papatasi against Experimental Challenge with Leishmania major and Saliva of Wild-Caught P. papatasi

Abstract

Several studies have shown that pre-immunization of mice with needle-injected saliva or pre-exposure to uninfected bites of Phlebotomus papatasi provided protection against infection with Leishmania major , the etiologic agent of zoonotic cutaneous leishmaniasis (ZCL).1-3 These studies were performed by using long-term laboratory colonized sand flies mainly because of the difficulty of working with wild-caught flies. A puzzling fact is that people in leishmaniasis-endemic areas succumb of ZCL despite the high frequency of uninfected bites compared with infected ones. 4 We showed in a previous study that pre-immunization of mice with salivary gland homogenate (SGH) of wild-caught P. papatasi does not confer protection against L. major co-inoculated with the same type of SGH compared with a significant protection obtained when pre-immunization and challenge were performed with SGH of long-term colonized flies. 5 It was reported that colonized and wild-caught Lutzomyia longipalpis differ in the composition and the amount of salivary proteins and these differences may account for the lower effect observed on the modulation of experimental Leishmania infection by wild-caught SGH. 6,7 Thus, these studies provide good evidence that the outcome of Leishmania infection differs significantly between colonized and wild-caught salivary gland proteins. Our aim in this study was to assess the protective effect of pre-immunization with SGH of long-term colonized P. papatasi on experimental L. major challenge co-inoculated with SGH of wild-caught P. papatasi .Phlebotomus papatasi (Tunisian strain that originated in the Governorate of Sidi Bouzid) have been reared at the Vector Ecology Laboratory of the Institut Pasteur de Tunis since 2003. 8 This colony is maintained without being supplemented periodically with wild-caught P. papatasi . Generation F 39 was used in this study. Wild sand flies were collected using CDC light traps from animal shelters located in the village of Felta (Governorate of Sidi Bouzid), a focus highly endemic for ZCL.9 Preparation of SGH from laboratory-reared and wild-caught P. papatasi was performed as described. 5 A highly virulent strain of L. major , MHOM/TN/95/GLC94, isolated from a patient in Tunisia was used in this study. 5 We used female BALB/c mice (6-8 weeks of age) bred in the animal facility of the Institut Pasteur de Tunis.Mice were immunized intradermally in the right ear with the equivalent of two pairs of salivary glands in 10 µL of phosphate-buffered saline (PBS). Two groups of 10 mice each were pre-immunized with SGH of long-term colonized female P. papatasi (F 39 ), once a week for two weeks. In the fourth week, the first [CSGH (F 39 )-L.m+CSGH (F 39 )] and the second [CSGH (F 39 )-L.m+WSGH] groups were challenged with 10 6 stationary phase L. major promastigotes in 50 µL of PBS co-inoculated subcutaneously in the right hind footpads with SGH of long-term, colonized and SGH of wild-caught, female P. papatasi , respectively. Three control groups of 10 mice each were used in this stud...

Delayed-Type Hypersensitivity to Sand Fly Saliva in Humans from a Leishmaniasis-Endemic Area of Mali Is TH1-Mediated and Persists to Midlife

“…It is pertinent to mention that the DTH responses in this study were induced by saliva from colony-bred sand flies. Assuming that a T H 1-mediated DTH response in humans correlates with protection against leishmaniasis, our observations differ from those in studies of animal models where colonized sand flies lose the ability to induce the protective immune response generated by wild-caught flies (Laurenti, da Matta et al 2009; Ahmed, Kaabi et al 2010). Additionally, Rohoušová et al (Rohousova, Hostomska et al 2011) reported the loss of saliva-mediated protection from CL in BALB/c mice exposed long-term to a large number of sand fly bites.…”

Sand fly saliva: toward a vaccine against leishmaniases

“…Recently it was shown that the colonization of P. papatasi can provide a saliva associated protection. Mice immunized with SGH of F29 labbred female P. papatasi could produce protection against L. major co-inoculated with the same type of SGH while the mice immunized with SGH of the wild-caught sand flies did not produce any protection [33,72,82]. The reason for this may be associated with the different amounts of the salivary proteins in the colonized versus the wild sand flies rather than a genetic variability [42].…”

“…The saliva of a sand fly has a composition which helps it to have a successful blood meal and it also helps the parasite to establish in its vertebrate host [28][29][30][31]. The saliva components are not constant in sand flies with different species, sex, age, generation and physiological stages [32][33][34]. Environmental factors and geographical locations seem to affect the saliva composition [35,36].…”

Immunization with LJM11 salivary protein protects against infection with Leishmania braziliensis in the presence of Lutzomyia longipalpis saliva

“…intermedia . There is evidence showing that the immunomodulatory and protective effect of SGS from wild caught and colonized sand flies can vary due to differences in the amount and composition of salivary proteins (Laurenti et al, 2009a, 2009b; Ahmed et al, 2010 and 2016). However, hamsters immunized with wild caught Lu.…”