Molecular approaches to understand vector-host and vector-pathogen interactions

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

The accomplishments of the section are: 1. We demonstrated an association between humoral and cellular immune response to the sand fly salivary protein rLinB-13 and disease severity of tegumentary leishmaniasis. We have previously shown that seropositivity to rLinB-13, a salivary protein from Lutzomyia intermedia, predicted sand fly exposure and was associated with increased risk of developing cutaneous leishmaniasis. We investigated the cellular immune response in humans to the sand fly recombinant protein rLinB-13. Peripheral blood mononuclear cells (PBMCs) stimulated in vitro with rLinB-13 secreted elevated levels of IL-10, IL-4, IL-1, IL-1, IL-6 and chemokines (CCL3, CCL4, CCL5 and CXCL5). CL, and disseminated leishmaniasis (DL) patients displayed a significantly higher IgG response to rLinB-13, compared to healthy subjects and anti-rLinB-13 IgG was positively correlated with the number of lesions in DL patients. Positive serology to rLinB-13 was also associated with chemotherapy failure. PBMCs from DL patients stimulated with rLINB-13 secreted significantly higher levels IL-10 and IL-1 compared to CL individuals. This study brings evidence that immunity to rLinB-13 influences disease outcome in L. braziliensis infection and results indicate that positive serology to rLinB-13 IgG can be employed as marker of DL, an emerging and severe form of disease caused by L. braziliensis. 2. We participated in a human clinical study to study the importance of sand fly bites in human infection. With new candidate vaccines in or near the clinic, a controlled human challenge model (CHIM) using natural sand fly challenge would provide a method for early evaluation of prophylactic efficacy. We evaluated the biting frequency and adverse effects resulting from exposure of human volunteers to bites of either Phlebotomus papatasi or P. duboscqi, two natural vectors of Leishmania major. 12 healthy participants were recruited (mean age 40.2 11.8 years) with no history of significant travel to regions where L. major-transmitting sand flies are prevalent. Participants were assigned to either vector by 1:1 allocation and exposed to five female sand flies for 30 minutes in a custom biting chamber. Bite frequency was recorded to confirm a bloodmeal was taken. Participant responses and safety outcomes were monitored using a visual analogue scale (VAS), clinical examination, and blood biochemistry. Focus groups were subsequently conducted to explore participant acceptability. All participants had at least one successful sand fly bite with none reporting any serious adverse events, with median VAS scores of 0-1/10 out to day 21 post-sand fly bite. Corresponding assessment of sand flies confirmed that for each participant at least 1/5 sand flies had successfully taken a bloodmeal (overall mean 3.671.03 bites per participant). There was no significant difference between P. papatasi and P. duboscqi in the number of bites resulting from 5 sand flies applied to human participants (3.30.81 vs 3.001.27 bites per participant; p=0.56) . In the two focus groups (n=5 per group), themes relating to positive participant-reported experiences of being bitten and the overall study, were identified. These results validate a protocol for achieving successful sand fly bites in humans that is safe, well-tolerated and acceptable for participants. 3. In collaboration with Erol Fikrig's lab, we compared mRNA lipid nanoparticles (LNPs), plasmid DNA, or recombinant protein platforms to test an anti-tick vaccine. We therefore utilized Salp14 as a model antigen to examine tick immunity using mRNA lipid nanoparticles (LNPs), plasmid DNA, or recombinant protein platforms. salp14 containing mRNA-LNPs vaccination elicited erythema at the tick bite site after tick challenge that occurred earlier, and that was more pronounced, compared with DNA or protein immunizations. Humoral and cellular responses associated with tick immunity were directed towards a 25 amino acid region of Salp14 at the carboxy terminus of the protein, as determined by antibody responses and skin-testing assays. This study demonstrates that the model of antigen delivery, also known as the vaccine platform, can influence the genesis of tick immunity in guinea pigs. mRNA-LNPs may be useful in helping to elicit erythema at the tick bite site, one of the most important early hallmarks of acquired tick resistance. mRNA-LNPs containing tick genes is a useful platform for the development of vaccines that can potentially prevent selected tick-borne diseases. 4. We initiated a human clinical project to study the skin immune responses in humans to tick bites (NCT05036707). We started to collect blood and skin biopsies from human subjects at different time points after tick attachment. Ticks fed on human subjects are being collect for RNA and protein extraction, which will be used for transcriptomic and proteomic analysis. We developed a basophil activation assay using flow cytometry to measure the activation of basophil to tick saliva in the blood of individuals exposed to tick bites. We optimized the Digital Spatial Profiling approach of histological samples from the bite site of the individuals on this study. We will be measuring the expression of proteins from cells recruited at the tick bite site. 5. We expressed and purified a tick salivary recombinant protein that is recognized by sera of individuals previously exposed to tick bites. This recombinant salivary protein will be used as biomarker to assess the risk of exposure to tick bites in Lyme disease endemic areas. We submitted an Employee Invention Report (EIR) for this molecule and its use a novel biomarker for tick exposure.