A defined mechanistic correlate of protection against Plasmodium falciparum malaria in non-human primates

Malaria vaccine design and prioritization has been hindered by the lack of a mechanistic correlate of protection. We previously demonstrated a strong association between protection and merozoite-neutralizing antibody responses following vaccination of non-human primates against Plasmodium falciparum reticulocyte binding protein homolog 5 (PfRH5). Here, we test the mechanism of protection. Using mutant human IgG1 Fc regions engineered not to engage complement or FcR-dependent effector mechanisms, we produce merozoite-neutralizing and non-neutralizing anti-PfRH5 chimeric monoclonal antibodies (mAbs) and perform a passive transfer-P. falciparum challenge study in Aotus nancymaae monkeys. At the highest dose tested, 6/6 animals given the neutralizing PfRH5-binding mAb c2AC7 survive the challenge without treatment, compared to 0/6 animals given non-neutralizing PfRH5-binding mAb c4BA7 and 0/6 animals given an isotype control mAb. Our results address the controversy regarding whether merozoite-neutralizing antibody can cause protection against P. falciparum blood-stage infections, and highlight the quantitative challenge of achieving such protection.

Molecular Epidemiology of Trypanosomatids and Trypanosoma cruzi in Primates from Peru

We determined the prevalence rate and risk of infection of Trypanosoma cruzi and other trypanosomatids in Peruvian non-human primates (NHPs) in the wild (n = 126) and in different captive conditions (n = 183). Blood samples were collected on filter paper, FTA cards, or EDTA tubes and tested using a nested PCR protocol targeting the 24Sα rRNA gene. Main risk factors associated with trypanosomatid and T. cruzi infection were genus and the human-animal context (wild vs captive animals). Wild NHPs had higher prevalence of both trypanosomatids (64.3 vs 27.9%, P < 0.001) and T. cruzi (8.7 vs 3.3%, P = 0.057), compared to captive NHPs, suggesting that parasite transmission in NHPs occurs more actively in the sylvatic cycle. In terms of primate family, Pitheciidae had the highest trypanosomatid prevalence (20/22, 90.9%) and Cebidae had the highest T. cruzi prevalence (15/117, 12.8%). T. cruzi and trypanosomatids are common in Peruvian NHPs and could pose a health risk to human and animals that has not been properly studied.

Ivermectin susceptibility, sporontocidal effect, and inhibition of time to re-feed in the Amazonian malaria vector Anopheles darlingi

BACKGROUND

Outdoor malaria transmission hinders malaria elimination efforts in the Amazon region and novel vector control tools are needed. Ivermectin mass drug administration (MDA) to humans kills wild Anopheles, targets outdoor-feeding vectors, and can suppress malaria parasite transmission. Laboratory investigations were performed to determine ivermectin susceptibility, sporontocidal effect and inhibition of time to re-feed for the primary Amazonian malaria vector, Anopheles darlingi.

METHODS

To assess ivermectin susceptibility, various concentrations of ivermectin were mixed in human blood and fed to An. darlingi. Mosquito survival was monitored daily for 7 days and a non-linear mixed effects model with Probit analysis was used to calculate lethal concentrations of ivermectin that killed 50% (LC₅₀), 25% (LC₂₅) and 5% (LC₅) of mosquitoes. To examine ivermectin sporonticidal effect, Plasmodium vivax blood samples were collected from malaria patients and offered to mosquitoes without or with ivermectin at the LC₅₀, LC₂₅ or LC₅. To assess ivermectin inhibition of mosquito time to re-feed, concentrations of ivermectin predicted to occur after a single oral dose of 200 μg/kg ivermectin were fed to An. darlingi. Every day for 12 days thereafter, individual mosquitoes were given the opportunity to re-feed on a volunteer. Any mosquitoes that re-blood fed or died were removed from the study.

RESULTS

Ivermectin significantly reduced An. darlingi survivorship: 7-day-LC₅₀ = 43.2 ng/ml [37.5, 48.6], -LC₂₅ = 27.8 ng/ml [20.4, 32.9] and -LC₅ = 14.8 ng/ml [7.9, 20.2]. Ivermectin compound was sporontocidal to P. vivax in An. darlingi at the LC₅₀ and LC₂₅ concentrations reducing prevalence by 22.6 and 17.1%, respectively, but not at the LC₅. Oocyst intensity was not altered at any concentration. Ivermectin significantly delayed time to re-feed at the 4-h (48.7 ng/ml) and 12-h (26.9 ng/ml) concentrations but not 36-h (10.6 ng/ml) or 60-h (6.3 ng/ml).

CONCLUSIONS

Ivermectin is lethal to An. darlingi, modestly inhibits sporogony of P. vivax, and delays time to re-feed at concentrations found in humans up to 12 h post drug ingestion. The LC₅₀ value suggests that a higher than standard dose (400-μg/kg) is necessary to target An. darlingi. These results suggest that ivermectin MDA has potential in the Amazon region to aid malaria elimination efforts.

Prevalence of Trypanosoma cruzi and Other Trypanosomatids in Frequently-Hunted Wild Mammals from the Peruvian Amazon

To better understand the ecology of Trypanosoma cruzi in the northeastern Peruvian Amazon, we evaluated the prevalence of T. cruzi and other trypanosomatids in four orders of wild mammals hunted and consumed by inhabitants of three remote indigenous communities in the Peruvian Amazon. Of 300 wild mammals sampled, 115 (38.3%) were infected with trypanosomatids and 15 (5.0%) with T. cruzi. The prevalence of T. cruzi within each species was as follows: large rodents (Cuniculus paca, 5.5%; Dasyprocta spp., 2.6%), edentates (Dasypus novemcinctus, 4.2%), and carnivores with higher prevalence (Nasua nasua, 18.8%). The high prevalence of T. cruzi and other trypanosomatids in frequently hunted wild mammals suggests a sizeable T. cruzi sylvatic reservoir in remote Amazonian locations.

A malaria vaccine protects Aotus monkeys against virulent Plasmodium falciparum infection

The Plasmodium falciparum protein, apical membrane antigen 1 forms a complex with another parasite protein, rhoptry neck protein 2, to initiate junction formation with the erythrocyte and is essential for merozoite invasion during the blood stage of infection. Consequently, apical membrane antigen 1 has been a target of vaccine development but vaccination with apical membrane antigen 1 alone in controlled human malaria infections failed to protect and showed limited efficacy in field trials. Here we show that vaccination with AMA1–RON2L complex in Freund’s adjuvant protects Aotus monkeys against a virulent Plasmodium falciparum infection. Vaccination with AMA1 alone gave only partial protection, delaying infection in one of eight animals. However, the AMA1–RON2L complex vaccine completely protected four of eight monkeys and substantially delayed infection (>25 days) in three of the other four animals. Interestingly, antibodies from monkeys vaccinated with the AMA1–RON2L complex had significantly higher neutralizing activity than antibodies from monkeys vaccinated with AMA1 alone. Importantly, we show that antibodies from animals vaccinated with the complex have significantly higher neutralization activity against non-vaccine type parasites. We suggest that vaccination with the AMA1–RON2L complex induces functional antibodies that better recognize AMA1 as it appears complexed with RON2 during merozoite invasion. These data justify progression of this next generation AMA1 vaccine towards human trials.

A vaccine targeting a protein complex that allows malaria-causing parasite to enter red blood cells has been produced. Malaria caused by the parasite Plasmodium falciparum is an oft-deadly infectious disease without an effective vaccine. A team of researchers at the National Institutes of Health led by Prakash Srinivasan, currently at the Johns Hopkins Malaria Research Institute, United States, demonstrated the efficacy of a vaccine candidate that works by priming a host’s immune system to a parasitic protein complex required to form a junction with red blood cells, allowing entry and proliferation of the pathogen. The group’s vaccine conferred more effective protection in monkeys than prior candidates that targeted only one component of the parasitic protein complex. This research warrants a closer look into how this candidate, and others targeting the protein complex, can be used to prevent malaria in humans.

Eosinophil-derived IL-4 drives progression of myocarditis to inflammatory dilated cardiomyopathy

Diny et al. report a pathogenic role for eosinophils in autoimmune myocarditis and dilated cardiomyopathy. Eosinophils are required for progression of myocarditis to dilated cardiomyopathy and drive severe disease when present in large numbers. Activated cardiac eosinophils mediate this process through IL-4.

Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in children and young adults. DCMi develops in up to 30% of myocarditis patients, but the mechanisms involved in disease progression are poorly understood. Patients with eosinophilia frequently develop cardiomyopathies. In this study, we used the experimental autoimmune myocarditis (EAM) model to determine the role of eosinophils in myocarditis and DCMi. Eosinophils were dispensable for myocarditis induction but were required for progression to DCMi. Eosinophil-deficient ΔdblGATA1 mice, in contrast to WT mice, showed no signs of heart failure by echocardiography. Induction of EAM in hypereosinophilic IL-5Tg mice resulted in eosinophilic myocarditis with severe ventricular and atrial inflammation, which progressed to severe DCMi. This was not a direct effect of IL-5, as IL-5TgΔdblGATA1 mice were protected from DCMi, whereas IL-5^−/− mice exhibited DCMi comparable with WT mice. Eosinophils drove progression to DCMi through their production of IL-4. Our experiments showed eosinophils were the major IL-4–expressing cell type in the heart during EAM, IL-4^−/− mice were protected from DCMi like ΔdblGATA1 mice, and eosinophil-specific IL-4 deletion resulted in improved heart function. In conclusion, eosinophils drive progression of myocarditis to DCMi, cause severe DCMi when present in large numbers, and mediate this process through IL-4.

Unstable Malaria Transmission in the Southern Peruvian Amazon and Its Association with Gold Mining, Madre de Dios, 2001-2012

The reemergence of malaria in the last decade in Madre de Dios, southern Peruvian Amazon basin, was accompanied by ecological, political, and socioeconomic changes related to the proliferation of illegal gold mining. We conducted a secondary analysis of passive malaria surveillance data reported by the health networks in Madre de Dios between 2001 and 2012. We calculated the number of cases of malaria by year, geographic location, intensity of illegal mining activities, and proximity of health facilities to the Peru-Brazil Interoceanic Highway. During 2001-2012, 203,773 febrile cases were identified in Madre de Dios, of which 30,811 (15.1%) were confirmed cases of malaria; all but 10 cases were due to Plasmodium vivax Cases of malaria rose rapidly between 2004 and 2007, reached 4,469 cases in 2005, and then declined after 2010 to pre-2004 levels. Health facilities located in areas of intense illegal gold mining reported 30-fold more cases than those in non-mining areas (ratio = 31.54, 95% confidence interval [CI] = 19.28, 51.60). Finally, health facilities located > 1 km from the Interoceanic Highway reported significantly more cases than health facilities within this distance (ratio = 16.20, 95% CI = 8.25, 31.80). Transmission of malaria in Madre de Dios is unstable, geographically heterogeneous, and strongly associated with illegal gold mining. These findings highlight the importance of spatially oriented interventions to control malaria in Madre de Dios, as well as the need for research on malaria transmission in illegal gold mining camps.

Population genomics studies identify signatures of global dispersal and drug resistance in Plasmodium vivax

Plasmodium vivax is a major public health burden, responsible for the majority of malaria infections outside Africa. We explored the impact of demographic history and selective pressures on the P. vivax genome by sequencing 182 clinical isolates sampled from 11 countries across the globe, using hybrid selection to overcome human DNA contamination. We confirmed previous reports of high genomic diversity in P. vivax relative to the more virulent Plasmodium falciparum species; regional populations of P. vivax exhibited greater diversity than the global P. falciparum population, indicating a large and/or stable population. Signals of natural selection suggest that P. vivax is evolving in response to antimalarial drugs and is adapting to regional differences in the human host and the mosquito vector. These findings underline the variable epidemiology of this parasite species and highlight the breadth of approaches that may be required to eliminate P. vivax globally.

Symptoms and Immune Markers in Plasmodium/Dengue Virus Co-infection Compared with Mono-infection with Either in Peru

Background

Malaria and dengue are two of the most common vector-borne diseases in the world, but co-infection is rarely described, and immunologic comparisons of co-infection with mono-infection are lacking.

Methodology and Principal Findings

We collected symptom histories and blood specimens from subjects in a febrile illness surveillance study conducted in Iquitos and Puerto Maldonado, Peru, between 2002–2011. Nineteen symptoms and 18 immune markers at presentation were compared among those with co-infection with Plasmodium/dengue virus (DENV), Plasmodium mono-infection, and DENV mono-infection. Seventeen subjects were identified as having Plasmodium/DENV co-infection and were retrospectively matched with 51 DENV mono-infected and 44 Plasmodium mono-infected subjects. Those with Plasmodium mono-infection had higher levels of IL-4, IL-6, IL-10, IL-12, IL-13, IL-17A, IFN-γ, and MIP1-α/CCL3 compared with DENV mono-infection or co-infection; those with Plasmodium mono-infection had more cough than those with DENV mono-infection. Subjects with DENV mono-infection had higher levels of TGF-β1 and more myalgia than those with Plasmodium mono-infection. No symptom was more common and no immune marker level was higher in the co-infected group, which had similar findings to the DENV mono-infected subjects.

Conclusions/Significance

Compared with mono-infection with either pathogen, Plasmodium/DENV co-infection was not associated with worse disease and resembled DENV mono-infection in both symptom frequency and immune marker level.

Dengue and malaria are two of the most important diseases spread by mosquitoes. Clinical manifestations of both febrile diseases overlap considerably, and either can be fatal. In addition, they are co-endemic in many places throughout the world. Despite this, only a handful of reports of co-infection with dengue virus and Plasmodium species are reported in the literature. Through our febrile surveillance program in the Peruvian Amazon, we were able to retrospectively identify 17 cases of co-infection with dengue virus and Plasmodium. Our study aimed to assess whether co-infection was associated with more symptoms or a different immune response compared with mono-infection alone. To answer this question, we utilized data and blood specimens collected during the acute presentation of these 17 subjects and compared them to a matched group of subjects with either dengue virus mono-infection or Plasmodium mono-infection. Our findings indicate co-infection with both pathogens was not associated with more symptoms and the immune profile of co-infection resembled dengue virus mono-infection more than Plasmodium mono-infection.

Molecular Epidemiology of Plasmodium falciparum Malaria Outbreak, Tumbes, Peru, 2010-2012

During 2010-2012, an outbreak of 210 cases of malaria occurred in Tumbes, in the northern coast of Peru, where no Plasmodium falciparum malaria case had been reported since 2006. To identify the source of the parasite causing this outbreak, we conducted a molecular epidemiology investigation. Microsatellite typing showed an identical genotype in all 54 available isolates. This genotype was also identical to that of parasites isolated in 2010 in the Loreto region of the Peruvian Amazon and closely related to clonet B, a parasite lineage previously reported in the Amazon during 1998-2000. These findings are consistent with travel history of index case-patients. DNA sequencing revealed mutations in the Pfdhfr, Pfdhps, Pfcrt, and Pfmdr1 loci, which are strongly associated with resistance to chloroquine and sulfadoxine/pyrimethamine, and deletion of the Pfhrp2 gene. These results highlight the need for timely molecular epidemiology investigations to trace the parasite source during malaria reintroduction events.

A PfRH5-based vaccine is efficacious against heterologous strain blood-stage Plasmodium falciparum infection in aotus monkeys

Antigenic diversity has posed a critical barrier to vaccine development against the pathogenic blood-stage infection of the human malaria parasite Plasmodium falciparum. To date, only strain-specific protection has been reported by trials of such vaccines in nonhuman primates. We recently showed that P. falciparum reticulocyte binding protein homolog 5 (PfRH5), a merozoite adhesin required for erythrocyte invasion, is highly susceptible to vaccine-inducible strain-transcending parasite-neutralizing antibody. In vivo efficacy of PfRH5-based vaccines has not previously been evaluated. Here, we demonstrate that PfRH5-based vaccines can protect Aotus monkeys against a virulent vaccine-heterologous P. falciparum challenge and show that such protection can be achieved by a human-compatible vaccine formulation. Protection was associated with anti-PfRH5 antibody concentration and in vitro parasite-neutralizing activity, supporting the use of this in vitro assay to predict the in vivo efficacy of future vaccine candidates. These data suggest that PfRH5-based vaccines have potential to achieve strain-transcending efficacy in humans.

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Vaccines based on the P. falciparum merozoite antigen PfRH5 were tested in Aotus monkeys

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PfRH5-based vaccines afforded protection against heterologous strains of P. falciparum

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Protection correlated with anti-PfRH5 IgG concentration and in vivo neutralization

Comparative genomic analysis of Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis

BACKGROUND

The Leishmania (Viannia) braziliensis complex is responsible for most cases of New World tegumentary leishmaniasis. This complex includes two closely related species but with different geographic distribution and disease phenotypes, L. (V.) peruviana and L. (V.) braziliensis. However, the genetic basis of these differences is not well understood and the status of L. (V.) peruviana as distinct species has been questioned by some. Here we sequenced the genomes of two L. (V.) peruviana isolates (LEM1537 and PAB-4377) using Illumina high throughput sequencing and performed comparative analyses against the L. (V.) braziliensis M2904 reference genome. Comparisons were focused on the detection of Single Nucleotide Polymorphisms (SNPs), insertions and deletions (INDELs), aneuploidy and gene copy number variations.

RESULTS

We found 94,070 variants shared by both L. (V.) peruviana isolates (144,079 in PAB-4377 and 136,946 in LEM1537) against the L. (V.) braziliensis M2904 reference genome while only 26,853 variants separated both L. (V.) peruviana genomes. Analysis in coding sequences detected 26,750 SNPs and 1,513 indels shared by both L. (V.) peruviana isolates against L. (V.) braziliensis M2904 and revealed two L. (V.) braziliensis pseudogenes that are likely to have coding potential in L. (V.) peruviana. Chromosomal read density and allele frequency profiling showed a heterogeneous pattern of aneuploidy with an overall disomic tendency in both L. (V.) peruviana isolates, in contrast with a trisomic pattern in the L. (V.) braziliensis M2904 reference. Read depth analysis allowed us to detect more than 368 gene expansions and 14 expanded gene arrays in L. (V.) peruviana, and the likely absence of expanded amastin gene arrays.

CONCLUSIONS

The greater numbers of interspecific SNP/indel differences between L. (V.) peruviana and L. (V.) braziliensis and the presence of different gene and chromosome copy number variations support the classification of both organisms as closely related but distinct species. The extensive nucleotide polymorphisms and differences in gene and chromosome copy numbers in L. (V.) peruviana suggests the possibility that these may contribute to some of the unique features of its biology, including a lower pathology and lack of mucosal development.

Next-Generation Sequencing of Plasmodium vivax Patient Samples Shows Evidence of Direct Evolution in Drug-Resistance Genes

Understanding the mechanisms of drug resistance in Plasmodium vivax, the parasite that causes the most widespread form of human malaria, is complicated by the lack of a suitable long-term cell culture system for this parasite. In contrast to P. falciparum, which can be more readily manipulated in the laboratory, insights about parasite biology need to be inferred from human studies. Here we analyze the genomes of parasites within 10 human P. vivax infections from the Peruvian Amazon. Using next-generation sequencing we show that some P. vivax infections analyzed from the region are likely polyclonal. Despite their polyclonality we observe limited parasite genetic diversity by showing that three or fewer haplotypes comprise 94% of the examined genomes, suggesting the recent introduction of parasites into this geographic region. In contrast we find more than three haplotypes in putative drug-resistance genes, including the gene encoding dihydrofolate reductase-thymidylate synthase and the P. vivax multidrug resistance associated transporter, suggesting that resistance mutations have arisen independently. Additionally, several drug-resistance genes are located in genomic regions with evidence of increased copy number. Our data suggest that whole genome sequencing of malaria parasites from patients may provide more insight about the evolution of drug resistance than genetic linkage or association studies, especially in geographical regions with limited parasite genetic diversity.

Outbreak of Cutaneous Leishmaniasis in Peruvian Military Personnel Undertaking Training Activities in the Amazon Basin, 2010

Military personnel deployed to the Amazon Basin are at high risk for cutaneous leishmaniasis (CL). We responded to an outbreak among Peruvian Army personnel returning from short-term training in the Amazon, conducting active case detection, lesion sample collection, and risk factor assessment. The attack rate was 25% (76/303); the incubation period was 2–36 weeks (median = 8). Most cases had one lesion (66%), primarily ulcerative (49%), and in the legs (57%). Real-time polymerase chain reaction (PCR) identified Leishmania (Viannia) braziliensis (59/61 = 97%) and L. (V.) guyanensis (2/61 = 3%). Being male (risk ratio [RR] = 4.01; P = 0.034), not wearing long-sleeve clothes (RR = 1.71; P = 0.005), and sleeping in open rooms (RR = 1.80; P = 0.009) were associated with CL. Sodium stibogluconate therapy had a 41% cure rate, less than previously reported in Peru (∼ 70%; P < 0.001). After emphasizing pre-deployment education and other basic prevention measures, trainees in the following year had lower incidence (1/278 = 0.4%; P < 0.001). Basic prevention can reduce CL risk in deployed militaries.

Cardiac fibroblasts mediate IL-17A-driven inflammatory dilated cardiomyopathy

IL-17A stimulates cardiac fibroblasts to produce inflammatory mediators critical for the recruitment and differentiation of myeloid cells during inflammatory dilated cardiomyopathy.

Inflammatory dilated cardiomyopathy (DCMi) is a major cause of heart failure in individuals below the age of 40. We recently reported that IL-17A is required for the development of DCMi. We show a novel pathway connecting IL-17A, cardiac fibroblasts (CFs), GM-CSF, and heart-infiltrating myeloid cells with the pathogenesis of DCMi. Il17ra^−/− mice were protected from DCMi, and this was associated with significantly diminished neutrophil and Ly6Chi monocyte/macrophage (MO/MΦ) cardiac infiltrates. Depletion of Ly6Chi MO/MΦ also protected mice from DCMi. Mechanistically, IL-17A stimulated CFs to produce key chemokines and cytokines that are critical downstream effectors in the recruitment and differentiation of myeloid cells. Moreover, IL-17A directs Ly6Chi MO/MΦ in trans toward a more proinflammatory phenotype via CF-derived GM-CSF. Collectively, this IL-17A–fibroblast–GM-CSF–MO/MΦ axis could provide a novel target for the treatment of DCMi and related inflammatory cardiac diseases.

Plasmodium vivax hospitalizations in a monoendemic malaria region: severe vivax malaria?

Severe malaria caused by Plasmodium vivax is no longer considered rare. To describe its clinical features, we performed a retrospective case control study in the subregion of Luciano Castillo Colonna, Piura, Peru, an area with nearly exclusive vivax malaria transmission. Severe cases and the subset of critically ill cases were compared with a random set of uncomplicated malaria cases (1:4). Between 2008 and 2009, 6,502 malaria cases were reported, including 106 hospitalized cases, 81 of which fit the World Health Organization definition for severe malaria. Of these 81 individuals, 28 individuals were critically ill (0.4%, 95% confidence interval = 0.2-0.6%) with severe anemia (57%), shock (25%), lung injury (21%), acute renal failure (14%), or cerebral malaria (11%). Two potentially malaria-related deaths occurred. Compared with uncomplicated cases, individuals critically ill were older (38 versus 26 years old, P < 0.001), but similar in other regards. Severe vivax malaria monoinfection with critical illness is more common than previously thought.

Fatal eosinophilic myocarditis develops in the absence of IFN-γ and IL-17A

CD4(+) T cells play a central role in inflammatory heart disease, implicating a cytokine product associated with Th cell effector function as a necessary mediator of this pathophysiology. IFN-γ-deficient mice developed severe experimental autoimmune myocarditis (EAM), in which mice are immunized with cardiac myosin peptide, whereas IL-17A-deficient mice were protected from progression to dilated cardiomyopathy. We generated IFN-γ(-/-)IL-17A(-/-) mice to assess whether IL-17 signaling was responsible for the severe EAM of IFN-γ(-/-) mice. Surprisingly, IFN-γ(-/-)IL-17A(-/-) mice developed a rapidly fatal EAM. Eosinophils constituted a third of infiltrating leukocytes, qualifying this disease as eosinophilic myocarditis. We found increased cardiac production of CCL11/eotaxin, as well as Th2 deviation, among heart-infiltrating CD4(+) cells. Ablation of eosinophil development improved survival of IFN-γ(-/-)IL-17A(-/-) mice, demonstrating the necessity of eosinophils in fatal heart failure. The severe and rapidly fatal autoimmune inflammation that developed in the combined absence of IFN-γ and IL-17A constitutes a novel model of eosinophilic heart disease in humans. This is also, to our knowledge, the first demonstration that eosinophils have the capacity to act as necessary mediators of morbidity in an autoimmune process.

A FRET-based real-time PCR assay to identify the main causal agents of New World tegumentary leishmaniasis

In South America, various species of Leishmania are endemic and cause New World tegumentary leishmaniasis (NWTL). The correct identification of these species is critical for adequate clinical management and surveillance activities. We developed a real-time polymerase chain reaction (PCR) assay and evaluated its diagnostic performance using 64 archived parasite isolates and 192 prospectively identified samples collected from individuals with suspected leishmaniasis enrolled at two reference clinics in Lima, Peru. The real-time PCR assay was able to detect a single parasite and provided unambiguous melting peaks for five Leishmania species of the Viannia subgenus that are highly prevalent in South America: L. (V.) braziliensis, L. (V.) panamensis, L. (V.) guyanensis, L. (V.) peruviana and L. (V.) lainsoni. Using kinetoplastid DNA-based PCR as a gold standard, the real-time PCR had sensitivity and specificity values of 92% and 77%, respectively, which were significantly higher than those of conventional tests such as microscopy, culture and the leishmanin skin test (LST). In addition, the real-time PCR identified 147 different clinical samples at the species level, providing an overall agreement of 100% when compared to multilocus sequence typing (MLST) data performed on a subset of these samples. Furthermore, the real-time PCR was three times faster and five times less expensive when compared to PCR - MLST for species identification from clinical specimens. In summary, this new assay represents a cost-effective and reliable alternative for the identification of the main species causing NWTL in South America.

Leishmaniasis is a neglected disease with more than two million new human infections annually worldwide. Tegumentary leishmaniasis, cutaneous and mucocutaneous, is mainly caused by five Leishmania species of the Viannia complex in South America. Different species can cause disease with similar symptoms but have dissimilar prognoses and may need different therapeutic regimens. Identification of Leishmania species traditionally relies on the multilocus enzyme electrophoresis (MLEE) assay, but it can only be applied to culture-positive samples and takes at least six weeks of intense laboratory work. A reliable and rapid assay for species identification can be a valuable tool. Molecular assays are the fastest and most accurate way to identify the etiological agents causing leishmaniasis. This paper describes a novel real-time PCR assay for identification of the five main species that cause tegumentary leishmaniasis in the New World. The assay correctly identified each of these five species of Leishmania directly from clinical samples. Because of its reliability, speed and simplicity, this assay could be used for species identification in routine laboratory diagnosis of leishmaniasis in endemic regions.

Susceptibility to autoimmune myocarditis is associated with intrinsic differences in CD4(+) T cells

A.SW and B10.S mice share the same major histocompatibility complex (MHC) haplotype (H-2(s)). However, A.SW mice are susceptible to experimental autoimmune myocarditis (EAM) and develop severe disease after immunization with myosin, whereas B10.S mice are resistant. We found that naive A.SW mice have intrinsically increased total CD4(+) T cell counts and increased proportions of CD4(+) T cells in their spleens compared to B10.S mice. Among total CD4(+) T cells, naive A.SW mice have a lower relative frequency of forkhead box protein 3 (FoxP3(+))CD25(+) regulatory T cells (T(regs)). A.SW mice also had a higher proportion of CD4(+) T cells and a lower proportion of T(regs) in their hearts and spleen during EAM, with greater T cell activation and proliferation, compared to B10.S mice. These differences in the T cell compartment were not antigen-specific, as ovalbumin/complete Freund's adjuvant (OVA/CFA) or CFA immunization elicited the same differences in CD4(+) T cells and T(regs) between A.SW and B10.S mice. Moreover, A.SW mice had more T helper type 17 (Th17) cells and B10.S had more Th1 cells in their hearts. The higher percentage of CD4(+) T cells and their enhanced potential to differentiate towards the Th17 pathway was also observed in naive A.SW mice. Interleukin (IL)-6 is required for Th17 induction. Interestingly, IL-6Rα expression was greater on naive A.SW CD4(+) T cells, compared to B10.S CD4(+) T cells, indicating that this intrinsic difference, together with a relatively lower T(reg) proportion of CD4(+) T cells, might lead to heightened Th17 responses and greater susceptibility to autoimmunity in A.SW mice.

Natural Leishmania infection of Lutzomyia auraensis in Madre de Dios, Peru, detected by a fluorescence resonance energy transfer-based real-time polymerase chain reaction

Leishmania species of the Viannia subgenus are responsible for most cases of New World tegumentary leishmaniasis. However, little is known about the vectors involved in disease transmission in the Amazon regions of Peru. We used a novel real-time polymerase chain reaction (PCR) to assess Leishmania infections in phlebotomines collected in rural areas of Madre de Dios, Peru. A total of 1,299 non-blood fed female sand flies from 33 species were captured by using miniature CDC light traps. Lutzomyia auraensis was the most abundant species (63%) in this area. Seven of 164 pools were positive by PCR for Leishmania by kinetoplast DNA. The real-time PCR identified four Lu. auraensis pools as positive for L. (Viannia) lainsoni and L. (V.) braziliensis. The minimum infection prevalence for Lu. auraensis was estimated to be 0.6% (95% confidence interval = 0.20-1.42%). Further studies are needed to assess the importance of Lu. auraensis in the transmission of New World tegumentary leishmaniasis in hyperendemic areas of Peru.

C1q/TNF-related protein-12 (CTRP12), a novel adipokine that improves insulin sensitivity and glycemic control in mouse models of obesity and diabetes

Despite the prevalence of insulin resistance and type 2 diabetes mellitus, their underlying mechanisms remain incompletely understood. Many secreted endocrine factors and the intertissue cross-talk they mediate are known to be dysregulated in type 2 diabetes mellitus. Here, we describe CTRP12, a novel adipokine with anti-diabetic actions. The mRNA and circulating levels of CTRP12 were decreased in a mouse model of obesity, but its expression in adipocytes was increased by the anti-diabetic drug rosiglitazone. A modest rise in circulating levels of CTRP12 by recombinant protein administration was sufficient to lower blood glucose in wild-type, leptin-deficient ob/ob, and diet-induced obese mice. A short term elevation of serum CTRP12 by adenovirus-mediated expression improved glucose tolerance and insulin sensitivity, normalized hyperglycemia and hyperinsulinemia, and lowered postprandial insulin resistance in obese and diabetic mice. CTRP12 improves insulin sensitivity in part by enhancing insulin signaling in the liver and adipose tissue. Further, CTRP12 also acts in an insulin-independent manner; in cultured hepatocytes and adipocytes, CTRP12 directly activated the PI3K-Akt signaling pathway to suppress gluconeogenesis and promote glucose uptake, respectively. Collectively, these data establish CTRP12 as a novel metabolic regulator linking adipose tissue to whole body glucose homeostasis through insulin-dependent and independent mechanisms.

Macrophages participate in IL-17-mediated inflammation

The involvement of macrophages (MΦs) in Th17-cell responses is still poorly understood. While neutrophils are thought to be the predominant effector of Th17-cell responses, IL-17 is also known to induce myelotropic chemokines and growth factors. Other T-cell-derived cytokines induce non-classical functions, suggesting that IL-17 sigxnaling may similarly elicit unique MΦ functions. Here, we characterized the expression of subunits of the IL-17 receptor on primary murine MΦs from different anatomical compartments. The greatest expression of IL-17 receptors was observed on mucosal Ly6C(hi) "inflammatory" MΦs. We further observed upregulation of IL-17 receptors in vitro on bone marrow-derived macrophages (BMMΦs) in response to peptidoglycan or CpG oligonucleotide stimuli, and in vivo, upon CFA administration. Macrophages expressing IL-17 receptors were observed infiltrating the hearts of mice with myocarditis, and genetic ablation of IL-17RA altered MΦ recruitment. Treating primary MΦs from a wide variety of different anatomic sources (as well as cell lines) with IL-17A induced the production of unique profiles of cytokines and chemokines, including GM-CSF, IL-3, IL-9, CCL4/MIP-1β and CCL5/RANTES. IL-17A also induced production of IL-12p70; IL-17-signaling-deficient MΦs elicited diminished IFN-γ production by responding DO11.10 CD4(+) T cells when used as APCs. These data indicate that MΦs from different anatomic locations direct IL-17-mediated responses.

Mechanisms of IFNγ regulation of autoimmune myocarditis

A protective effect of interferon-gamma (IFNγ) has been described in a number of models of autoimmune disease, including experimental autoimmune myocarditis (EAM). Some reports have suggested that regulation of apoptosis in autoreactive lymphocytes mediate these protective functions. We examined the potential of IFNγ to regulate apoptotic mechanisms in detail, both in vitro and in vivo in EAM. We observed multiple apoptotic defects in caspase activity, and the expression of TNF superfamily members on CD4(+) T cells. In addition, we observed selective defects in CD4(+) T cell activation in response to antigenic stimulation. These activation and apoptotic defects were CD4(+) cell autonomous, independent of the genotype of APCs. Inhibition of nitric oxide production in vivo did not reproduce the severe form of EAM of IFNγ-deficient mice, indicating that this pathway does not mediate the protective effect of IFNγ. Crosswise adoptive transfer of wild type, IFNγ(-/-), and IFNγR(-/-)EAM demonstrated that IFNγ signaling was critical in CD4(+) cells, but that non-CD4(+) sources of IFNγ production were also involved in the control of disease. Together, these data indicate multiple mechanisms of autonomous and non-autonomous CD4(+) T cell regulation mediated by IFNγ in the control of autoimmune heart disease.

Interleukin-17A is dispensable for myocarditis but essential for the progression to dilated cardiomyopathy

RATIONALE

One-third of myocarditis cases progresses to dilated cardiomyopathy (DCM), but the mechanisms controlling this process are largely unknown. CD4(+) T helper (Th)17 cells have been implicated in the pathogenesis of autoimmune diseases, but the role of Th17-produced cytokines during inflammation-induced cardiac remodeling has not been previously studied.

OBJECTIVE

We examined the importance of interleukin (IL)-17A in the progression of myocarditis to DCM using a mouse model.

METHODS AND RESULTS

Immunization of mice with myocarditogenic peptide in complete Freund's adjuvant induced the infiltration of IL-17A-producing Th17 cells into the inflamed heart. Unexpectedly, IL-17A-deficient mice developed myocarditis with similar incidence and severity compared to wild-type mice. Additionally, IL-17A deficiency did not ameliorate the severe myocarditis of interferon (IFN)gamma-deficient mice, suggesting that IL-17A plays a minimal role during acute myocarditis. In contrast, IL-17A-deficient mice were protected from postmyocarditis remodeling and did not develop DCM. Flow cytometric and cytokine analysis revealed an important role for IL-17A in heart-specific upregulation of IL-6, TNFalpha, and IL-1beta and the recruitment of CD11b(+) monocyte and Gr1(+) granulocyte populations into the heart. Furthermore, IL-17A-deficient mice had reduced interstitial myocardial fibrosis, downregulated expression of matrix metalloproteinase-2 and -9 and decreased gelatinase activity. Treatment of BALB/c mice with anti-IL-17A monoclonal antibody administered after the onset of myocarditis abrogated myocarditis-induced cardiac fibrosis and preserved ventricular function.

CONCLUSIONS

Our findings reveal a critical role for IL-17A in postmyocarditis cardiac remodeling and the progression to DCM. Targeting IL-17A may be an attractive therapy for patients with inflammatory dilated cardiomyopathy.

Sex differences in a murine model of Sjögren's syndrome

Sex differences in a NOD.H2(h4) murine model of Sjögren's syndrome were analyzed. Compared to males, female NOD.H2(h4) mice have increased severity of sialoadenitis and have a significantly increased percentage of CD4(+) T cells in salivary gland infiltrates. CD4(+) T cells in female infiltrates produce more Th2 and Th17 cytokines than in males, while males have greater Th1 responses. Females also have enhanced B cell responses, with higher levels of SSA and SSB serum antibodies, and B cell activation factor F (BAFF). Thus, sex has a strong impact on the severity of murine Sjögren's syndrome by affecting the immune mechanisms driving the autoimmune inflammation.

Interleukin-13 protects against experimental autoimmune myocarditis by regulating macrophage differentiation

We report here that interleukin (IL)-13 protects BALB/c mice from myocarditis, whether induced by peptide immunization or by viral infection. In contrast to mild disease in IL-4 knockout (KO) BALB/c mice, IL-13 KO BALB/c mice developed severe coxsackievirus B3 (CVB3)-induced autoimmune myocarditis and myocarditogenic peptide-induced experimental autoimmune myocarditis. Such severe disease was characterized by increased cardiac inflammation, increased total intracardiac CD45(+) leukocytes, elevated anti-cardiac myosin autoantibodies, and increased cardiac fibrosis. Echocardiography revealed that IL-13 KO mice developed severe dilated cardiomyopathy with impaired cardiac function and heart failure. Hearts of IL-13 KO mice had increased levels of the proinflammatory and profibrotic cytokines IL-1beta, IL-18, interferon-gamma, transforming growth factor-beta1, and IL-4 as well as histamine. The hallmark of the disease in IL-13 KO mice was the up-regulation of T-cell responses. CD4(+) T cells were increased in IL-13 KO hearts both proportionally and in absolute number. Splenic T cells from IL-13 KO mice were highly activated, and myosin stimulation additionally increased T-cell proliferation. CD4(+)CD25(+)Foxp3(+) regulatory T-cell numbers were decreased in the spleens of IL-13 KO mice. IL-13 deficiency led to decreased levels of alternatively activated CD206(+) and CD204(+) macrophages and increased levels of classically activated macrophages. IL-13 KO mice had increased caspase-1 activation, leading to increased production of both IL-1beta and IL-18. Therefore, IL-13 protects against myocarditis by modulating monocyte/macrophage populations and by regulating their function.

IL13 induces IL17 by regulating dendritic cell maturation in autoimmune myocarditis (129.25)

IL13 KO BALB/c mice developed severe myosin-induced experimental autoimmune myocarditis (EAM). This severe disease is characterized by increased inflammation, increased total intracardiac CD45+ leukocytes, and progression to dilated cardiomyopathy. Hearts of IL13 KO mice had increased levels of the proinflammatory and profibrotic cytokines IL1β, IL18, IFNγ, TGFβ1, IL4 and histamine. However, another proinflammatory cytokine, IL17 is significantly decreased in both hearts (p= 0.0005) and spleens of IL13 KO mice on day 21 of EAM. The decrease of IL17 is significantly correlated with decrease of another Th17 cytokine – TNF α in the hearts and spleens of IL13 KO mice. The substantial decrease of the Th17 population in the absence of IL13 is not due to the absence of cytokines required to induce Th17, since IL13 KO mice have increased levels of IL1β and TGFβ. This Th17 defect is also not caused by increased IL27, which is known to impair Th17 development, since IL27 is actually significantly decreased in IL13 KO mice. IL23, which is necessary for sustaining the Th17 population, is significantly decreased in IL13 KO mice. It has been shown that IL13 induces production of IL23 by dendritic cells. We have observed severely impaired DC maturation both in vivo as well as in vitro in IL13 KO mice. Thus, we hypothesize that IL13 is required for maturation and IL23 production by DCs; therefore, IL13 is required for Th17 differentiation.

(Supported by 2R01 HL67290).