Plasmodium vivax tryptophan-rich antigen reduces type I collagen secretion via the NF-κBp65 pathway in splenic fibroblasts.

BACKGROUND: The spleen plays a critical role in the immune response against malaria parasite infection, where splenic fibroblasts (SFs) are abundantly present and contribute to immune function by secreting type I collagen (collagen I). The protein family is characterized by Plasmodium vivax tryptophan-rich antigens (PvTRAgs), comprising 40 members. PvTRAg23 has been reported to bind to human SFs (HSFs) and affect collagen I levels. Given the role of type I collagen in splenic immune function, it is important to investigate the functions of the other members within the PvTRAg protein family. METHODS: Protein structural prediction was conducted utilizing bioinformatics analysis tools and software. A total of 23 PvTRAgs were successfully expressed and purified using an Escherichia coli prokaryotic expression system, and the purified proteins were used for co-culture with HSFs. The collagen I levels and collagen-related signaling pathway protein levels were detected by immunoblotting, and the relative expression levels of inflammatory factors were determined by quantitative real-time PCR. RESULTS: In silico analysis showed that P. vivax has 40 genes encoding the TRAg family. The C-terminal region of all PvTRAgs is characterized by the presence of a domain rich in tryptophan residues. A total of 23 recombinant PvTRAgs were successfully expressed and purified. Only five PvTRAgs (PvTRAg5, PvTRAg16, PvTRAg23, PvTRAg30, and PvTRAg32) mediated the activation of the NF-κBp65 signaling pathway, which resulted in the production of inflammatory molecules and ultimately a significant reduction in collagen I levels in HSFs. CONCLUSIONS: Our research contributes to the expansion of knowledge regarding the functional role of PvTRAgs, while it also enhances our understanding of the immune evasion mechanisms utilized by parasites.

Effect of moringa extract on parasitemia, monocyte activation and organomegaly among Mus musculus infected by Plasmodium berghei ANKA.

In Indonesia, malaria remains a problem, with 94,610 active cases in 2021 and its current therapy includes chloroquine and artemisinin; however, resistance has been commonly reported. To overcome this problem, studies about potential medicinal plants that can be used as antimalaria, such as moringa (Moringa oleifera) started to receive more attention. The aim of this study was to investigate the effects of moringa in parasitemia, monocyte activation, and organomegaly on animal model malaria. This experimental study used male Mus musculus, infected by Plasmodium berghei ANKA, as an animal malaria model. The extract was made by maceration of dry moringa leaves, which were then divided into three concentrations: 25%, 50%, and 75%. Dihydroartemisinin-piperazine was used as a positive control treatment, and distilled water as a negative control treatment. The animals were observed for six days to assess the parasitemia count and the number of monocyte activation. On day 7, the animals were terminated, and the liver, spleen, and kidney were weighed. The results showed that the effective concentrations in reducing parasitemia and inducing monocyte activation were 50% and 25% of moringa leaf extract, respectively. The smallest liver and spleen enlargement was observed among animals within the group treated with a 50% concentration of M. oleifera extract. In contrast, the smallest kidney enlargement was observed in the group treated with 25% of M. oleifera extract. Further analysis is recommended to isolate compounds with antimalarial properties in moringa leaves.

The neurotropic schistosome vs experimental autoimmune encephalomyelitis: are there any winners?

The incidences of multiple sclerosis have risen worldwide, yet neither the trigger nor efficient treatment is known. Some research is dedicated to looking for treatment by parasites, mainly by helminths. However, little is known about the effect of helminths that infect the nervous system. Therefore, we chose the neurotropic avian schistosome Trichobilharzia regenti, which strongly promotes M2 polarization and tissue repair in the central nervous system, and we tested its effect on the course of experimental autoimmune encephalomyelitis (EAE) in mice. Surprisingly, the symptoms of EAE tended to worsen after the infection with T. regenti. The infection did not stimulate tissue repair, as indicated by the similar level of demyelination. Eosinophils heavily infiltrated the infected tissue, and the microglia number increased as well. Furthermore, splenocytes from T. regenti-infected EAE mice produced more interferon (IFN)-γ than splenocytes from EAE mice after stimulation with myelin oligodendrocyte glycoprotein. Our research indicates that the combination of increased eosinophil numbers and production of IFN-γ tends to worsen the EAE symptoms. Moreover, the data highlight the importance of considering the direct effect of the parasite on the tissue, as the migrating parasite may further tissue damage and make tissue repair even more difficult.

Treatment using vanillin-derived synthetic molecules incorporated into polymeric micelles is effective against infection caused by Leishmania amazonensis species.

Treatment against leishmaniasis presents problems, mainly due to the toxicity of the drugs, high cost, and the emergence of resistant strains. A previous study showed that two vanillin-derived synthetic molecules, 3s [4-(2-hydroxy-3-(4-octyl-1H-1,2,3-triazol-1-yl)propoxy)-3-methoxybenzaldehyde] and 3t [4-(3-(4-decyl-1H-1,2,3-triazol-1-yl)-2-hydroxypropoxy)-3-methoxybenzaldehyde], presented antileishmanial activity against Leishmania infantum, L. amazonensis, and L. braziliensis species. In the present work, 3s and 3t were evaluated to treat L. amazonensis-infected mice. Molecules were used pure or incorporated into Poloxamer 407-based micelles. In addition, amphotericin B (AmpB) and its liposomal formulation, Ambisome®, were used as control. Animals received the treatment and, one and 30 days after, they were euthanized to evaluate immunological, parasitological, and biochemical parameters. Results showed that the micellar compositions (3s/Mic and 3t/Mic) induced significant reductions in the lesion mean diameter and parasite load in the infected tissue and distinct organs, as well as a specific and significant antileishmanial Th1-type immune response, which was based on significantly higher levels of IFN-γ, IL-12, nitrite, and IgG2a isotype antibodies. Drug controls showed also antileishmanial action; although 3s/Mic and 3t/Mic have presented better and more significant parasitological and immunological data, which were based on significantly higher IFN-γ production and lower parasite burden in treated animals. In addition, significantly lower levels of urea, creatinine, alanine transaminase, and aspartate transaminase were found in mice treated with 3s/Mic and 3t/Mic, when compared to the others. In conclusion, results suggest that 3s/Mic and 3t/Mic could be considered as therapeutic candidates to treat against L. amazonensis infection.

Interleukin-7 potentiates MAPK10-elicited host-protective vaccine against Leishmania donovani.

Leishmania donovani causes the potentially fatal disease visceral leishmaniasis for which neither a vaccine nor an adjuvant for human use exists. Although interleukin-7 (IL-7) is implicated in CD4+ T-cell response stabilization, its anti-leishmanial function is uncertain. Therefore, we examined whether IL-7 would potentiate the efficacy of Leishmania major-expressed MAPK10 (LmjMAPK10; M10)-elicited anti-leishmanial host-protective response. We observed that aligning with IL-7R expression, IL-7 increased IFN-γ-secreting TH1 cell but reduced IL-4-producing TH2 cells and production of IL-10 and TGF-ß effectuating anti-leishmanial functions in susceptible BALB/c mouse-derived macrophages. Co-culturing IL-7-pre-treated L. donovani-infected macrophages with L. donovani-infected BALB/c-derived T cells induced IFN-γ-dominated TH1 type anti-leishmanial function. IL-7 treatment of L. donovani-infected BALB/c mice significantly reduced splenic and hepatic parasite loads. Co-culturing CD4+ T cells from IL to 7-treated mice with L. donovani-infected macrophages reduced amastigote numbers suggesting IL-7-elicited host-protective effector T cells. Priming BALB/c with M10 + IL-7 reduced the splenic parasite burden more effectively than that was observed in M10-primed mice. An enhanced protection against L. donovani infection was accompanied by enhanced IL-12 and IFN-γ, but suppressed IL-10 and IL-4, response and host-protective TH1 and memory T cells. These results indicate IL-7-induced leishmanial antigen-specific memory T cell response that protects a susceptible host against L. donovani infection.

Experimental infection of Toxoplasma gondii in specific pathogen-free and commercial broiler chicks.

Toxoplasma gondii is an intracellular protozoan parasite that infects most warm-blooded animals, including humans, and causes toxoplasmosis. In this study, the pathogenicity of RH strain of T. gondii in broiler chicks was investigated and the susceptible tissues of chicks were clarified. Fourteen-day-old broiler chicks were injected intraperitoneally with 1 × 107, 1 × 106, and 1 × 105 tachyzoites of T. gondii, respectively. The results showed that the spleen and lungs were frequently positive for T. gondii DNA. Moreover, in chicks, infection with only 1 × 107 tachyzoites resulted in clinical symptoms, with lower weight gain, higher body temperature, anorexia and apathy, indicating that chicks are insusceptible to T. gondii infection. Then, this study investigated the relationship between T. gondii survival and chick body temperature. In the experiment, the invasion and proliferation of T. gondii were evaluated at 37 °C and 41 °C, respectively, and the survival of the parasites was significantly inhibited at 41 °C. In conclusion, broiler chicks are insusceptible to T. gondii infection, and the higher body temperature compared to other susceptible animals is a key factor in the reduction of T. gondii pathogenicity.

Multi-organ/disseminated echinococcosis in children: Case series and review of the literature.

AIM: Echinococcosis with multi-organ/disseminated involvement is rare in childhood. We aimed to evaluate the clinical and laboratory characteristics and prognosis in paediatric patients with echinococcosis having multiorgan/disseminated involvement. METHOD: We evaluated retrospectively children with echinococcosis with involvement of three or more organs. RESULTS: Thirteen patients were included in the study. The median age was 120 (range 71-189) months. Three (23%) were diagnosed incidentally. Abdominal pain was seen in 5 (38.4%) patients, vomiting in 4 (30.7%), headache in 3 (23%), cough in 2 (15.3%), groin pain in 1 (7.6%), 1 (7.6%) had jaundice and 1 (7.6%) had fever. The median duration of complaints was 48 (0-140) days. The most common tripartite organ was 38.4% (5/13) liver, lung and spleen. Isolated abdominal dissemination was detected in two patients. Two patients had multi-organ involvement and multiple cysts with dissemination. Cyst rupture was observed in three of the patients; recurrent urinary tract infection, hydroureteronephrosis, secondary peritonitis with intra-abdominal abscess, and biliary tract fistula were each observed in one patient. Relapse developed in 3 (23%) patients. CONCLUSION: Echinococcosis is a very slow growing and complex parasitic disease that affects many organs and tissues. In our study, eosinophilia, recurrence, and complications were seen at a higher rate in paediatric patients with multiorgan involvement, who required repetitive surgeries and long-term medical treatment. However, there are scanty data on risk factors, optimum treatment and prognosis.

Immunochemotherapy for visceral leishmaniasis: combinatorial action of Miltefosine plus LBSapMPL vaccine improves adaptative Th1 immune response with control of splenic parasitism in experimental hamster model.

The control of human visceral leishmaniasis (VL) is hard since there are no vaccines available as well as the treatment is hampered by toxicity and resistant parasites. Furthermore, as human, and canine VL causes immunosuppression, the combination of drugs with immunostimulatory agents is interesting to upregulate the immunity, reducing side-effects, improving treatment approaches against disease. Herein, we assessed the immunochemotherapy using miltefosine along with a vaccine formulated by Leishmania braziliensis antigens + saponin + monophosphoryl lipid-A (LBSapMPL) in L. infantum-infected hamsters. Two months after infection, the animals received treatments, and after 15 days they were evaluated for the treatment effect. The potential anti-Leishmania effect of miltefosine + LBSapMPL-vaccine was revealed by a specific immune response activation reflecting in control of spleen parasitism using half the miltefosine treatment time. The treated animals also showed an increase of total and T-CD4 splenocytes producing IFN-γ and TNF-α and a decrease of interleukin-10 and anti-Leishmania circulating IgG. In addition, it was demonstrated that the control of spleen parasitism is related to the generation of a protective Th1 immune response. Hence, due to the combinatorial action of miltefosine with LBSapMPL-vaccine in immunostimulating and controlling parasitism, this immunochemotherapy protocol can be an important alternative option against canine and human VL.

Cluster analysis of splenocyte microRNAs in the pig reveals key signal regulators of immunomodulation in the host during acute and chronic Toxoplasma gondii infection.

BACKGROUND: Toxoplasma gondii is an obligate intracellular protozoan parasite that can cause a geographically widespread zoonosis. Our previous splenocyte microRNA profile analyses of pig infected with T. gondii revealed that the coordination of a large number of miRNAs regulates the host immune response during infection. However, the functions of other miRNAs involved in the immune regulation during T. gondii infection are not yet known. METHODS: Clustering analysis was performed by K-means, self-organizing map (SOM), and hierarchical clustering to obtain miRNA groups with the similar expression patterns. Then, the target genes of the miRNA group in each subcluster were further analyzed for functional enrichment by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome pathway to recognize the key signaling molecules and the regulatory signatures of the innate and adaptive immune responses of the host during T. gondii infection. RESULTS: A total of 252 miRNAs were successfully divided into 22 subclusters by K-means clustering (designated as K1-K22), 29 subclusters by SOM clustering (designated as SOM1-SOM29), and six subclusters by hierarchical clustering (designated as H1-H6) based on their dynamic expression levels in the different infection stages. A total of 634, 660, and 477 GO terms, 15, 26, and 14 KEGG pathways, and 16, 15, and 7 Reactome pathways were significantly enriched by K-means, SOM, and hierarchical clustering, respectively. Of note, up to 22 miRNAs mainly showing downregulated expression at 50 days post-infection (dpi) were grouped into one subcluster (namely subcluster H3-K17-SOM1) through the three algorithms. Functional analysis revealed that a large group of immunomodulatory signaling molecules were controlled by the different miRNA groups to regulate multiple immune processes, for instance, IL-1-mediated cellular response and Th1/Th2 cell differentiation partly depending on Notch signaling transduction for subclusters K1 and K2, innate immune response involved in neutrophil degranulation and TLR4 cascade signaling for subcluster K15, B cell activation for subclusters SOM17, SOM1, and SOM25, leukocyte migration, and chemokine activity for subcluster SOM9, cytokine-cytokine receptor interaction for subcluster H2, and interleukin production, chemotaxis of immune cells, chemokine signaling pathway, and C-type lectin receptor signaling pathway for subcluster H3-K17-SOM1. CONCLUSIONS: Cluster analysis of splenocyte microRNAs in the pig revealed key regulatory properties of subcluster miRNA molecules and important features in the immune regulation induced by acute and chronic T. gondii infection. These results contribute new insight into the identification of physiological immune responses and maintenance of tolerance in pig spleen tissues during T. gondii infection.

Flau-A, a naphthoquinone derivative, is a promising therapeutic candidate against visceral leishmaniasis: A preliminary study.

Visceral leishmaniasis (VL) is a neglected tropical disease found in tropical and subtropical regions in the world. The therapeutics used for the treatment against disease presents problems, mainly related to drug toxicity, route of administration, high cost and/or by emergence of resistant strains. In this context, the search for alternative antileishmanial candidates is desirable. Recently, a naphthoquinone derivative namely 2-(2,3,4-tri-O-acetyl-6-deoxy-ß-L-galactopyranosyloxy)-1,4-naphthoquinone or Flau-A showed an effective in vitro biological action against Leishmania infantum. In the present study, the efficacy of this naphthoquinone derivative was evaluated in an in vivo infection model. BALB/c mice (n = 12 per group) were infected and later received saline or were treated with empty micelles (B/Mic), free Flau-A or it incorporated in Poloxamer 407-based micelles (Flau-A/Mic). The products were administered subcutaneously in the infected animals, which were then euthanized one (n = 6 per group) and 15 (n = 6 per group) days post-therapy, when immunological and parasitological evaluations were performed. Results showed that animals treated with Flau-A or Flau-A/Mic produced significantly higher levels of antileishmanial IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibody, when compared to data found in the control (saline and B/Mic) groups; which showed significantly higher levels of parasite-specific IL-4, IL-10 and IgG1 antibody. In addition, animals receiving free Flau-A or Flau-A/Mic presented also significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, when compared to the controls. A low hepatic and renal toxicity was also found. Overall, Flau-A/Mic showed better immunological and parasitological results, when compared to the use of free molecule. In conclusion, preliminary data suggest that this composition could be considered in future studies as promising therapeutic candidate against VL.

Cryptic erythrocytic infections in Plasmodium vivax, another challenge to its elimination.

Human malaria caused by Plasmodium vivax infection (vivax malaria) is a major global health issue. It is the most geographically widespread form of the disease, accounting for 7 million annual clinical cases, the majority of cases in America and Asia and an estimation of over 2.5 billion people living under risk of infection. The general perception towards vivax malaria has shifted recently, following a series of reports, from being viewed as a benign infection to the recognition of its potential for more severe manifestations including fatal cases. However, the underlying pathogenic mechanisms of vivax malaria remain largely unresolved. Asymptomatic carriers of malaria parasites are a major challenge for malaria elimination. In the case of P. vivax, it has been widely accepted that the only source of cryptic parasites is hypnozoite dormant stages. Here, we will review new evidence indicating that cryptic erythrocytic niches outside the liver, in particular in the spleen and bone marrow, can represent a major source of asymptomatic infections. The origin of such parasites is being controversial and many key gaps in the knowledge of such infections remain unanswered. Yet, as parasites in these niches seem to be sheltered from immune response and antimalarial drugs, research on this area should be reinforced if elimination of malaria is to be achieved. Last, we will glimpse into the role of reticulocyte-derived exosomes, extracellular vesicles of endocytic origin, as intercellular communicators likely involved in the formation of such cryptic erythrocytic infections.

Pitting of malaria parasites in microfluidic devices mimicking spleen interendothelial slits.

The spleen is a hematopoietic organ that participates in cellular and humoral immunity. It also serves as a quality control mechanism for removing senescent and/or poorly deformable red blood cells (RBCs) from circulation. Pitting is a specialized process by which the spleen extracts particles, including malaria parasites, from within circulating RBCs during their passage through the interendothelial slits (IES) in the splenic cords. To study this physiological function in vitro, we have developed two microfluidic devices modeling the IES, according to the hypothesis that at a certain range of mechanical stress on the RBC, regulated through both slit size and blood flow, would force it undergo the pitting process without affecting the cell integrity. To prove its functionality in replicating pitting of malaria parasites, we have performed a characterization of P. falciparum-infected RBCs (P.f.-RBCs) after their passage through the devices, determining hemolysis and the proportion of once-infected RBCs (O-iRBCs), defined by the presence of a parasite antigen and absence of DAPI staining of parasite DNA using a flow cytometry-based approach. The passage of P.f.-RBCs through the devices at the physiological flow rate did not affect cell integrity and resulted in an increase of the frequency of O-iRBCs. Both microfluidic device models were capable to replicate the pitting of P.f.-RBCs ex vivo by means of mechanical constraints without cellular involvement, shedding new insights on the role of the spleen in the pathophysiology of malaria.

Splenic Transcriptional Responses in Severe Visceral Leishmaniasis: Impaired Leukocyte Chemotaxis and Cell Cycle Arrest.

Structural changes in the spleen have been reported in several infectious diseases. In visceral leishmaniasis (VL), a severe parasitic disease caused by Leishmania spp., the loss of white pulp accompanies a severe clinical presentation. Hamster model reproduces aspects of human VL progression. In the early stages, a transcriptomic signature of leukocyte recruitment was associated with white pulp hyperplasia. Subsequently, impaired leukocyte chemotaxis with loss of T lymphocytes in the periarteriolar lymphoid sheath occurred. This differential gene expression was subsequently corroborated by transcriptomic profiling of spleens in severe human VL. At the latest stage, spleen disorganization was associated with increasing clinical signs of VL. White pulp disruption was accompanied by decreased DLK1 expression. The expression of CXCL13, CCR5, CCL19, CCR6, CCR7 and LTA decreased, likely regulated by CDKN2A overexpression. Our findings enlighten a pathway implying cell cycle arrest and decreased gene expression involved in spleen organization.

TLR7 modulating B-cell immune responses in the spleen of C57BL/6 mice infected with Schistosoma japonicum.

B cells played an important role in Schistosoma infection-induced diseases. TLR7 is an intracellular member of the innate immune receptor. The role of TLR7 on B cells mediated immune response is still unclear. Here, C57BL/6 mice were percutaneously infected by S. japonicum for 5-6 weeks. The percentages and numbers of B cells increased in the infected mice (p < 0.05), and many activation and function associated molecules were also changed on B cells. More splenic cells of the infected mice expressed TLR7, and B cells were served as the main cell population. Moreover, a lower level of soluble egg antigen (SEA) specific antibody and less activation associated molecules were found on the surface of splenic B cells from S. japonicum infected TLR7 gene knockout (TLR7 KO) mice compared to infected wild type (WT) mice (p < 0.05). Additionally, SEA showed a little higher ability in inducing the activation of B cells from naive WT mice than TLR7 KO mice (p < 0.05). Finally, the effects of TLR7 on B cells are dependent on the activation of NF-κB p65. Altogether, TLR7 was found modulating the splenic B cell responses in S. japonicum infected C57BL/6 mice.

Ikzf2 Regulates the Development of ICOS+ Th Cells to Mediate Immune Response in the Spleen of S. japonicum-Infected C57BL/6 Mice.

Background: Th cells (helper T cells) have multiple functions in Schistosoma japonicum (S. japonicum) infection. Inducible co-stimulator (ICOS) is induced and expressed in activated T lymphocytes, which enhances the development of B cells and antibody production through the ICOS/ICOSL pathway. It remains unclear about the role and possible regulating mechanism of ICOS+ Th cells in the spleen of S. japonicum-infected C57BL/6 mice. Methods: C57BL/6 mice were infected with cercariae of S. japonicum through the abdomen. The expression of ICOS, activation markers, and the cytokine production on CD4+ ICOS+ Th cells were detected by flow cytometry (FCM) and quantitative real-time PCR (qRT-PCR). Moreover, the differentially expressed gene data of ICOS+ and ICOS- Th cells from the spleen of infected mice were obtained by mRNA sequencing. Besides, Western blot and chromatin immunoprecipitation (ChIP) were used to explore the role of Ikzf2 on ICOS expression. Results: After S. japonicum infection, the expression of ICOS molecules gradually increased in splenic lymphocytes, especially in Th cells (P < 0.01). Compared with ICOS- Th cells, more ICOS+ Th cells expressed CD69, CD25, CXCR5, and CD40L (P < 0.05), while less of them expressed CD62L (P < 0.05). Also, ICOS+ Th cells expressed more cytokines, such as IFN-γ, IL-4, IL-10, IL-2, and IL-21 (P < 0.05). RNA sequencing results showed that many transcription factors were increased significantly in ICOS+ Th cells, especially Ikzf2 (P < 0.05). And then, the expression of Ikzf2 was verified to be significantly increased and mainly located in the nuclear of ICOS+ Th cells. Finally, ChIP experiments and dual-luciferase reporter assay confirmed that Ikzf2 could directly bind to the ICOS promoter in Th cells. Conclusion: In this study, ICOS+ Th cells were found to play an important role in S. japonicum infection to induce immune response in the spleen of C57BL/6 mice. Additionally, Ikzf2 was found to be one important transcription factor that could regulate the expression of ICOS in the spleen of S. japonicum-infected C57BL/6 mice.

Intranasal vaccine from whole Leishmania donovani antigens provides protection and induces specific immune response against visceral leishmaniasis.

Visceral leishmaniasis is a protozoan disease associated with high fatality rate in developing countries. Although the drug pipeline is constantly improving, available treatments are costly and live-threatening side effects are not uncommon. Moreover, an approved vaccine against human leishmaniasis does not exist yet. Using whole antigens from Leishmania donovani promastigotes (LdAg), we investigated the protective potential of a novel adjuvant-free vaccine strategy. Immunization of mice with LdAg via the intradermal or the intranasal route prior to infection decreases the parasitic burden in primary affected internal organs, including the liver, spleen, and bone marrow. Interestingly, the intranasal route is more efficient than the intradermal route, leading to better parasite clearance and remarkable induction of adaptive immune cells, notably the helper and cytotoxic T cells. In vitro restimulation experiments with Leishmania antigens led to significant IFN-γ secretion by splenocytes; therefore, exemplifying specificity of the adaptive immune response. To improve mucosal delivery and the immunogenic aspects of our vaccine strategy, we used polysaccharide-based nanoparticles (NP) that carry the antigens. The NP-LdAg formulation is remarkably taken up by dendritic cells and induces their maturation in vitro, as revealed by the increased expression of CD80, CD86 and MHC II. Intranasal immunization with NP-LdAg does not improve the parasite clearance in our experimental timeline; however, it does increase the percentage of effector and memory T helper cells in the spleen, suggesting a potential induction of long-term memory. Altogether, this study provides a simple and cost-effective vaccine strategy against visceral leishmaniasis based on LdAg administration via the intranasal route, which could be applicable to other parasitic diseases.

Absence of Bim sensitizes mice to experimental Trypanosoma cruzi infection.

Chagas disease is a life-threatening disorder caused by the protozoan parasite Trypanosoma cruzi. Parasite-specific antibodies, CD8+ T cells, as well as IFN-γ and nitric oxide (NO) are key elements of the adaptive and innate immunity against the extracellular and intracellular forms of the parasite. Bim is a potent pro-apoptotic member of the Bcl-2 family implicated in different aspects of the immune regulation, such as negative selection of self-reactive thymocytes and elimination of antigen-specific T cells at the end of an immune response. Interestingly, the role of Bim during infections remains largely unidentified. To explore the role of Bim in Chagas disease, we infected WT, Bim+/-, Bim-/- mice with trypomastigotes forms of the Y strain of T. cruzi. Strikingly, our data revealed that Bim-/- mice exhibit a delay in the development of parasitemia followed by a deficiency in the control of parasite load in the bloodstream and a decreased survival compared to WT and Bim+/- mice. At the peak of parasitemia, peritoneal macrophages of Bim-/- mice exhibit decreased NO production, which correlated with a decrease in the pro-inflammatory Small Peritoneal Macrophage (SPM) subset. A similar reduction in NO secretion, as well as in the pro-inflammatory cytokines IFN-γ and IL-6, was also observed in Bim-/- splenocytes. Moreover, an impaired anti-T. cruzi CD8+ T-cell response was found in Bim-/- mice at this time point. Taken together, our results suggest that these alterations may contribute to the establishment of a delayed yet enlarged parasitic load observed at day 9 after infection of Bim-/- mice and place Bim as an important protein in the control of T. cruzi infections.

The Inflammatory Effects of Dietary Lipids Regulate Growth of Parasites during Visceral Leishmaniasis.

Visceral leishmaniasis is a potentially fatal disease caused by the protozoon Leishmania donovani or L. infantum (Li). Although previous studies revealed that high lipid intake reduces parasite burdens in Leishmania donovani-infected mice, the specific contributions of dietary lipids to Li-associated pathogenesis are not known. To address this, we evaluated parasite growth, liver pathology, and transcriptomic signatures in Li-infected BALB/c mice fed either a control, high-fat, high-cholesterol, or high-fat-high-cholesterol diet. Using quantitative PCR (qPCR), we observed significantly reduced liver parasite burdens in mice fed the high-fat-high-cholesterol diet compared to mice fed the control diet. In contrast to the liver, parasite expansion occurred earlier in the spleens of mice fed the experimental diets. Histological examination revealed an intense inflammatory cell infiltrate in livers predominantly composed of neutrophils caused by the high-fat-high-cholesterol diet specifically. After 8 weeks of infection (12 weeks of diet), Illumina microarrays revealed significantly increased expression of transcripts belonging to immune- and angiogenesis-related pathways in livers of both uninfected and Li-infected mice fed the high-fat-high-cholesterol diet. These data suggest that increased fat and cholesterol intake prior to Li infection leads to a hepatic inflammatory environment and thus reduces the parasite burden in the liver. Defining inflammatory signatures as well as pathology in the liver may reveal opportunities to modify the therapeutic approach to Li infection. IMPORTANCE Leishmaniasis is a spectrum of diseases caused by Leishmania species protozoa that is most common in warm climates, coinciding with impoverished regions. Visceral leishmaniasis is a potentially fatal disease in which parasites infect reticuloendothelial organs and cause progressive wasting and immunocompromise. The distribution and demographics of visceral leishmaniasis have changed over recent years, coinciding with modernizing societies and the increased availability of Western diets rich in lipid content. We report here that increased dietary fat and cholesterol intake affected disease pathogenesis by increasing inflammation and reducing localized parasite burdens in the liver. These diet-induced changes in disease pathogenesis might explain in part the changing epidemiology of visceral leishmaniasis. A relationship between diet and inflammatory responses may occur in leishmaniasis and other microbial or immune-mediated diseases, possibly revealing opportunities to modify the therapeutic approach to microbial infections.

Stereological analysis of liver, spleen and bone of Leishmania infantum-experimentally infected hamsters.

Leishmaniasis is remaining as one of the important health problems of many countries around the world. The histopathology of the disease and the effects of the parasite on various tissues have not yet been fully elucidated. The current study aimed to evaluate the stereological features of the liver, spleen, and bone of hamsters infected with Leishmania infantum. In this experimental study, the L. infantum parasite was mass cultivated in a culture medium. Then, 15 golden hamsters were selected, of which 5 animals were considered as controls and another 10 animals were injected intravenously, with 1 × 108 promastigotes of L. infantum. Four months later, the hamsters were euthanized and impression smears were prepared from the liver and spleen. Moreover, pathology slides were prepared from the spleen, liver, and femur. The orientated method was used to obtain isotropic uniform random (IUR) sections. For stereological evaluation, the tissues were fixed with formalin buffer, and sections (4 and 25 µm thick) were prepared and stained with Heidenhain's AZAN trichrome and hematoxylin-eosin, respectively. The tissue samples were examined by stereological methods and all changes in the samples of the infected hamsters were compared with the control group. The number of hepatocyte and their nuclei volumes were significantly decreased in the Leishmania-infected group, compared to the control group. The number of Kupffer cells and their volume in the liver of the Leishmania-infected group was higher than that of the control group, and the differences were statistically significant. The volume of trabeculae and central arteries in the spleen of the Leishmania-infected group was lower than that of the control group and the number of lymphocytes and macrophages in the spleen of the Leishmania-infected group was increased compared to the control group. The trabecular volume and the number of osteoblasts and osteoclasts of the femur in Leishmania-infected animals decreased, whereas the volume of bone marrow was significantly raised. Leishmaniasis leads to changes in tissue structure and their function in the host by the involvement of various organs of the immune system including the liver, spleen, and bone. Understanding these changes are important in identifying the effective mechanisms of the parasite and host interaction.

Analysis of spleen histopathology, splenocyte composition and haematological parameters in four strains of mice infected with Plasmodium berghei K173.

BACKGROUND: Malaria is a fatal disease that presents clinically as a continuum of symptoms and severity, which are determined by complex host-parasite interactions. Clearance of infection is believed to be accomplished by the spleen and mononuclear phagocytic system (MPS), independent of artemisinin treatment. The spleen filters infected red blood cells (RBCs) from circulation through immune-mediated recognition of the infected RBCs followed by phagocytosis. This study evaluated the tolerance of four different strains of mice to Plasmodium berghei strain K173 (P. berghei K173), and the differences in the role of the spleen in controlling P. berghei K173 infection. METHODS: Using different strains of mice (C57BL/6, BALB/C, ICR, and KM mice) infected with P. berghei K173, the mechanisms leading to splenomegaly, histopathology, splenocyte activation and proliferation, and their relationship to the control of parasitaemia and host mortality were examined and evaluated. RESULTS: Survival time of mice infected with P. berghei K173 varied, although the infection was uniformly lethal. Mice of the C57BL/6 strain were the most resistant, while mice of the strain ICR were the most susceptible. BALB/c and KM mice were intermediate. In the course of P. berghei K173 infection, all infected mice experienced significant splenomegaly. Parasites were observed in the red pulp at 3 days post infection (dpi) in all animals. All spleens retained late trophozoite stages as well as a fraction of earlier ring-stage parasites. The percentages of macrophages in infected C57BL/6 and KM mice were higher than uninfected mice on 8 dpi. Spleens of infected ICR and KM mice exhibited structural disorganization and remodelling. Furthermore, parasitaemia was significantly higher in KM versus C57BL/6 mice at 8 dpi. The percentages of macrophages in ICR infected mice were lower than uninfected mice, and the parasitaemia was higher than other strains. CONCLUSIONS: The results presented here demonstrate the rate of splenic mechanical filtration and that splenic macrophages are the predominant roles in controlling an individual's total parasite burden. This can influence the pathogenesis of malaria. Finally, different genetic backgrounds of mice have different splenic mechanisms for controlling malaria infection.