Imaging Infection by Vector-Borne Protozoan Parasites Using Whole-Mouse Bioluminescence.

Vector-borne protozoan parasites such as Plasmodium spp. Leishmania spp. and Trypanosoma brucei are responsible for several serious diseases. Significant advances in parasitology have been made using rodent models combined with live imaging techniques, including whole-mouse bioluminescence imaging (BLI). This technique has been applied to investigate parasite dissemination, infectivity, and growth. It has also been used in drug and vaccine testing. This chapter focuses on the methods that utilize whole-mouse BLI to (i) evaluate the homing and infectivity of Plasmodium berghei sporozoites; (ii) conduct in vivo testing of promising chemical entities against Leishmania infantum infection; and (iii) study molecular mechanisms of host susceptibility to Trypanosoma brucei brucei infection.

Immunization with CSP and a RIG-I Agonist is Effective in Inducing a Functional and Protective Humoral Response Against Plasmodium.

Malaria is a major public health concern, as a highly effective human vaccine remains elusive. The efficacy of a subunit vaccine targeting the most abundant protein of the sporozoite surface, the circumsporozoite protein (CSP) has been hindered by difficulties in generating an effective humoral response in both quantity and quality. Using the rodent Plasmodium yoelii model we report here that immunization with CSP adjuvanted with 5'ppp-dsRNA, a RIG-I agonist, confers early and long-lasting sterile protection in mice against stringent sporozoite and mosquito bite challenges. The immunization induced high levels of antibodies, which were functional in targeting and killing the sporozoites and were sustained over time through the accumulation of long-lived plasma cells in the bone marrow. Moreover, 5'ppp-dsRNA-adjuvanted immunization with the CSP of P. falciparum was also significantly protective against challenges using a transgenic PfCSP-expressing P. yoelii parasite. Conversely, using the TLR3 agonist poly(A:U) as adjuvant resulted in a formulation that despite inducing high antibody levels was unable to generate equally functional antibodies and was, consequently, less protective. In conclusion, we demonstrate that using 5'ppp-dsRNA as an adjuvant to vaccines targeting CSP induces effective anti-Plasmodium humoral immunity.

MAEBL Contributes to Plasmodium Sporozoite Adhesiveness.

The sole currently approved malaria vaccine targets the circumsporozoite protein-the protein that densely coats the surface of sporozoites, the parasite stage deposited in the skin of the mammalian host by infected mosquitoes. However, this vaccine only confers moderate protection against clinical diseases in children, impelling a continuous search for novel candidates. In this work, we studied the importance of the membrane-associated erythrocyte binding-like protein (MAEBL) for infection by Plasmodium sporozoites. Using transgenic parasites and live imaging in mice, we show that the absence of MAEBL reduces Plasmodium berghei hemolymph sporozoite infectivity to mice. Moreover, we found that maebl knockout (maebl-) sporozoites display reduced adhesion, including to cultured hepatocytes, which could contribute to the defects in multiple biological processes, such as in gliding motility, hepatocyte wounding, and invasion. The maebl- defective phenotypes in mosquito salivary gland and liver infection were reverted by genetic complementation. Using a parasite line expressing a C-terminal myc-tagged MAEBL, we found that MAEBL levels peak in midgut and hemolymph parasites but drop after sporozoite entry into the salivary glands, where the labeling was found to be heterogeneous among sporozoites. MAEBL was found associated, not only with micronemes, but also with the surface of mature sporozoites. Overall, our data provide further insight into the role of MAEBL in sporozoite infectivity and may contribute to the design of future immune interventions.

Structural, thermal, vibrational, solubility and DFT studies of a tolbutamide co-amorphous drug delivery system for treatment of diabetes.

Among the strategies for bioavailability improvement of poorly soluble drugs, co-amorphous systems have revealed to have a significant impact in the increase of the aqueous solubility of the drug, and at the same time increasing the amorphous state stability and dissolution rate when compared with the neat drug. Tolbutamide (TBM) is an oral hypoglycemic drug largely used in the treatment of type II Mellitus diabetes. TBM is a class II drug according to the Biopharmaceutical Classification System, meaning that it has low solubility and higher permeability. The aim of this study was to synthesize a co-amorphous material of tolbutamide (TBM) with tromethamine (TRIS). Density functional theory (DFT), allowed to study the structural, electronic, and thermodynamic properties, as well as solvation effects. In same theory level, several interactions tests were performed to obtain the most thermodynamically favorable drug-coformer intermolecular interactions. The vibrational spectra (mid infrared and Raman spectroscopy) are in accordance with the theoretical studies, showing that the main molecular interactions are due to the carbonyl, sulfonyl, and amide groups of TMB and the alcohol and amine groups of TRIS. X-ray powder diffraction was used to study the physical stability in dry condition at 25 °C of the co-amorphous system, indicating that the material remained in an amorphous state up to 90 days. Differential scanning calorimetry and thermogravimetric results showed a high increase of the Tg when compared with the amorphous neat drug, from 4.3 °C to 83.7 °C, which generally translated into good physical stability. Solubility studies demonstrated an increase in the solubility of TBM by 2.5 fold when compared with its crystalline counterpart.

Toward Chemical Validation of Leishmania infantum Ribose 5-Phosphate Isomerase as a Drug Target.

Neglected tropical diseases caused by kinetoplastid parasites (Trypanosoma brucei, Trypanosoma cruzi, and Leishmania spp.) place a significant health and economic burden on developing nations worldwide. Current therapies are largely outdated, inadequate, and face mounting drug resistance from the causative parasites. Thus, there is an urgent need for drug discovery and development. Target-led drug discovery approaches have focused on the identification of parasite enzymes catalyzing essential biochemical processes, which significantly differ from equivalent proteins found in humans, thereby providing potentially exploitable therapeutic windows. One such target is ribose 5-phosphate isomerase B (RpiB), an enzyme involved in the nonoxidative branch of the pentose phosphate pathway, which catalyzes the interconversion of d-ribose 5-phosphate and d-ribulose 5-phosphate. Although protozoan RpiB has been the focus of numerous targeted studies, compounds capable of selectively inhibiting this parasite enzyme have not been identified. Here, we present the results of a fragment library screening against Leishmania infantum RpiB (LiRpiB), performed using thermal shift analysis. Hit fragments were shown to be effective inhibitors of LiRpiB in activity assays, and several fragments were capable of selectively inhibiting parasite growth in vitro. These results support the identification of LiRpiB as a validated therapeutic target. The X-ray crystal structure of apo LiRpiB was also solved, permitting docking studies to assess how hit fragments might interact with LiRpiB to inhibit its activity. Overall, this work will guide structure-based development of LiRpiB inhibitors as antileishmanial agents.

Physical Interactions With Bacteria and Protozoan Parasites Establish the Scavenger Receptor SSC4D as a Broad-Spectrum Pattern Recognition Receptor.

Since the pioneering discoveries, by the Nobel laureates Jules Hoffmann and Bruce Beutler, that Toll and Toll-like receptors can sense pathogenic microorganisms and initiate, in vertebrates and invertebrates, innate immune responses against microbial infections, many other families of pattern recognition receptors (PRRs) have been described. One of such receptor clusters is composed by, if not all, at least several members of the scavenger receptor cysteine-rich (SRCR) superfamily. Many SRCR proteins are plasma membrane receptors of immune cells; however, a small subset consists of secreted receptors that are therefore in circulation. We here describe the first characterization of biological and functional roles of the circulating human protein SSC4D, one of the least scrutinized members of the family. Within leukocyte populations, SSC4D was found to be expressed by monocytes/macrophages, neutrophils, and B cells, but its production was particularly evident in epithelial cells of several organs and tissues, namely, in the kidney, thyroid, lung, placenta, intestinal tract, and liver. Similar to other SRCR proteins, SSC4D shows the capacity of physically binding to different species of bacteria, and this opsonization can increase the phagocytic capacity of monocytes. Importantly, we have uncovered the capacity of SSC4D of binding to several protozoan parasites, a singular feature seldom described for PRRs in general and here demonstrated for the first time for an SRCR family member. Overall, our study is pioneer in assigning a PRR role to SSC4D.

TRSP is dispensable for the Plasmodium pre-erythrocytic phase.

Plasmodium sporozoites deposited in the skin following a mosquito bite must migrate and invade blood vessels to complete their development in the liver. Once in the bloodstream, sporozoites arrest in the liver sinusoids, but the molecular determinants that mediate this specific homing are not yet genetically defined. Here we investigate the involvement of the thrombospondin-related sporozoite protein (TRSP) in this process using knockout Plasmodium berghei parasites and in vivo bioluminescence imaging in mice. Resorting to a homing assay, trsp knockout sporozoites were found to arrest in the liver similar to control parasites. Moreover, we found no defects in the establishment of infection in mice following inoculation of trsp knockout sporozoites via intravenous and cutaneous injection or mosquito bite. Accordingly, mutant sporozoites were also able to successfully invade hepatocytes in vitro. Altogether, these results suggest TRSP may have a redundant role in the completion of the pre-erythrocytic phase of the malaria parasite. Nonetheless, identifying molecules with paramount roles in this phase could aid in the search for new antigens needed for the design of a protective vaccine against malaria.

Exploiting the 2-Amino-1,3,4-thiadiazole Scaffold To Inhibit Trypanosoma brucei Pteridine Reductase in Support of Early-Stage Drug Discovery.

Pteridine reductase-1 (PTR1) is a promising drug target for the treatment of trypanosomiasis. We investigated the potential of a previously identified class of thiadiazole inhibitors of Leishmania major PTR1 for activity against Trypanosoma brucei (Tb). We solved crystal structures of several TbPTR1-inhibitor complexes to guide the structure-based design of new thiadiazole derivatives. Subsequent synthesis and enzyme- and cell-based assays confirm new, mid-micromolar inhibitors of TbPTR1 with low toxicity. In particular, compound 4m, a biphenyl-thiadiazole-2,5-diamine with IC50 = 16 µM, was able to potentiate the antitrypanosomal activity of the dihydrofolate reductase inhibitor methotrexate (MTX) with a 4.1-fold decrease of the EC50 value. In addition, the antiparasitic activity of the combination of 4m and MTX was reversed by addition of folic acid. By adopting an efficient hit discovery platform, we demonstrate, using the 2-amino-1,3,4-thiadiazole scaffold, how a promising tool for the development of anti-T. brucei agents can be obtained.

Randomized Controlled Trial of a Cognitive Narrative Crisis Intervention for Bereavement in Primary Healthcare.

BACKGROUND AND AIMS: As there are known risks of retraumatization through bereavement crisis interventions, we tailored a new intervention lowering the degree of direct emotional activation. However, we need some evidence on the effects of depression and psychotraumatic symptoms between 1 and 6 months after a loss. METHOD: We conducted a randomized controlled trial with two groups: control group (n = 18) and experimental group (n = 11) in two assessments (1 and 6 months after loss); both included a semi-structured interview (Socio-Demographic Questionnaire, Beck Depression Inventory and the Impact of Events Scale-Revised-IES-R). The experimental group had a cognitive-narrative program with four sessions: recalling; cognitive and emotional subjectivization; metaphorization; and projecting sessions. RESULTS: Participants in the experimental and control groups have lower levels of depression and traumatic stress 6 months after a loss. Statistically significant results in emotional numbing IES-R sub-scale are observed. CONCLUSIONS: A brief narrative-based cost-effective intervention has a positive effect on depression, controlling the traumatic stress and time after a loss.

Randomised controlled trial of a cognitive narrative intervention for complicated grief in widowhood.

OBJECTIVE: The implementation of bereavement interventions is frequently requested, and its effectiveness has been controversial. The aim of this study is to evaluate the effectiveness of a cognitive narrative intervention for complicated grief (CG) for controlling post-traumatic and depressive issues. METHOD: The study is a randomised controlled trial and uses the Socio Demographic Questionnaire (SDQ), the Inventory of Complicated Grief (ICG), the Beck Depression Inventory (BDI) and the Impact of Events Scale-Revised (IES-R). There were three phases in the study: (1) The SDQ and CG evaluations were applied to bereaved elders (n = 82). The bereaved elders with the 40 highest ICG values (≥25) were randomly allocated into two groups: the intervention group (n = 20) and control group (n = 20); (2) participants were evaluated using the BDI and IES-R and the IG gave informed consent to participate in an intervention with four weekly 60-min sessions addressing recall, emotional and cognitive subjectivation, metaphorisation and projecting. (3) Two months later, the ICG, BDI and IES-R assessments were repeated. RESULTS: Outcome measures showed a statistically significant reduction of CG, depressive and traumatic symptoms compared to the controls. Very high effect sizes for the ICG, BDI and IES-R reflect the effectiveness of the intervention along the longitudinal profile. CONCLUSIONS: These results reinforce the importance of brief interventions that combine a reduced number of sessions with lower costs, which is reflected in an increased adherence to the programme along with high effectiveness.