Genomic and Phenotypic Characterization of Experimentally Selected Resistant Leishmania donovani Reveals a Role for Dynamin-1-Like Protein in the Mechanism of Resistance to a Novel Antileishmanial Compound

Humans and their pathogens are continuously locked in a molecular arms race during which the eventual emergence of pathogen drug resistance (DR) seems inevitable. For neglected tropical diseases (NTDs), DR is generally studied retrospectively once it has already been established in clinical settings.

An Insight Into Systemic Immune Response in Leishmania donovani Mediated Atypical Cutaneous Leishmaniasis in the New Endemic State of Himachal Pradesh, India

Leishmaniasis continues to afflict known and newer endemic sites despite global efforts towards its control and elimination. In this regard, the emergence of newer endemic sites with unusual disease formats is recognized wherein Leishmania donovani complex classically known to cause visceral disease is demonstrated to cause cutaneous manifestation. In this context, atypical cutaneous leishmaniasis (CL) cases caused by L. donovani genetic variants from the newer endemic state of Himachal Pradesh (HP) in India are beginning to be understood in terms of parasite determinants. The atypical CL manifestation further needs to be explored to define host immune correlates with a possible role in driving the unusual disease progression. In the given study, we performed comprehensive systemic-immune profiling of the atypical CL patients from the study area in HP, India, in comparison with the classical visceral leishmaniasis (VL) patients from the northeast region of India. The systemic immune response was studied using ELISA-based assessment of Th1, Th2, Th17, Treg, and Th22 specific plasma cytokine expression pattern and parasite-specific total serum IgG/IgG subclasses. The specified immune correlates are known to exhibit heterogeneous association with the different infecting parasite species, infection load, and co-lateral host immunopathology in classical CL and VL. In the atypical CL patient group, altered expression of IL-10 emerged as the key finding that could potentially fine-tune the Th1/Th17/Th22 effector cytokine axis towards a localized cutaneous manifestation. A reduced expression of IL-10 along with a high IFN-γ/IL-10 ratio as a readout of effective parasite killing defined atypical cutaneous outcome. In contrast, high circulatory IL-10 levels and a depressed IFN-γ/IL-10 ratio were seen in classical VL patients in line with an ineffective parasite-killing cytokine response. Overall, the study highlights new knowledge on host immune correlates in terms of cytokine expression pattern and IgG subclasses that underline atypical disease manifestation such that L. donovani, a generally visceralizing parasite species cause skin localized cutaneous lesions.

ATIVIDADE ANTIPARASITÁRIA DA Artemisia annua CONTRA ESPÉCIES DE Leishmania

Introdução: A Artemisia annua é uma planta natural da Ásia e foi introduzida em diversos países ao redor do mundo(1). Conhecida há séculos por suas características medicinais, essa planta pode ser utilizada, por exemplo, na forma de óleo essencial ou pó para auxiliar contra diversas patologias, desde uma simples inflamação até mesmo infecção viral e bacteriana, diabetes e cânceres(1,3,4). O amplo espectro de ação da A. annua se deve ao fato de haver em sua composição metabólitos como artemisinina, flavonóides, terpenóides, cumarinas e saponinas(4). A Artemisia annua possui também ação contra a leishmaniose, uma doença causada por mais de 20 agentes etiológicos intracelulares(4). Transmitida por insetos dos gêneros Phlebotomus e Lutzomyia spp, a leishmaniose é considerada uma doença de preocupação global e se divide em três formas, sendo elas a cutânea, mucocutânea e visceral(2,4). Uma vez que os medicamentos que existem atualmente no mercado possuem graves efeitos colaterais, fez-se necessário o melhor entendimento acerca da ação da Artemisia annua sobre as espécies de Leishmania(4). Objetivos: Este resumo tem como objetivo analisar a ação anti-leishmania da Artemisia annua e em quais formas do parasita essa planta é capaz de atuar. Métodos: Foi realizada uma busca nas plataformas de dados PubMed e Google Acadêmico, e os artigos científicos foram encontrados por meio do descritor “artemisia annua AND leishmania”. Resultados: As folhas da Artemisia annua apresentaram ação contra as amastigotas da Leishmania panamensis, agente etiológico da leishmaniose cutânea, e não foi observada cito e genotoxicidade(4). Além disso, as sementes e folhas da A. annua mostraram atividade contra promastigotas e amastigotas de Leishmania donovani, agente causador da leishmaniose visceral. A ação anti-leishmania ocorreu por meio da ativação da morte celular programada, onde foi possível observar a exteriorização de fosfatidilserina e fragmentos de DNA. Os componentes da A. annua identificados na pesquisa foram a cânfora, n-hexano, acetato de alfa-amirina, β-cariofileno e derivados da artemisinina. Ademais, não foi encontrada citotoxicidade nas células de mamíferos(2,3). Conclusões: Em decorrência do que foi exposto, conclui-se que a Artemisia annua possui componentes com ação anti-leishmania, provocando a morte de amastigotas e promastigotas. Com isso, é necessário que pesquisas continuem sendo realizadas com a A. annua para que mais compostos com potencial contra espécies de Leishmania possam ser identificados e, assim, abordagens terapêuticas mais baratas e seguras possam ser aplicadas em indivíduos infectados por esse parasita.

Spatial Point Pattern Analysis Identifies Mechanisms Shaping the Skin Parasite Landscape in Leishmania donovani Infection

Increasing evidence suggests that in hosts infected with parasites of the Leishmania donovani complex, transmission of infection to the sand fly vector is linked to parasite repositories in the host skin. However, a detailed understanding of the dispersal (the mechanism of spread) and dispersion (the observed state of spread) of these obligatory-intracellular parasites and their host phagocytes in the skin is lacking. Using endogenously fluorescent parasites as a proxy, we apply image analysis combined with spatial point pattern models borrowed from ecology to characterize dispersion of parasitized myeloid cells (including ManR+ and CD11c+ cells) and predict dispersal mechanisms in a previously described immunodeficient model of L. donovani infection. Our results suggest that after initial seeding of infection in the skin, heavily parasite-infected myeloid cells are found in patches that resemble innate granulomas. Spread of parasites from these initial patches subsequently occurs through infection of recruited myeloid cells, ultimately leading to self-propagating networks of patch clusters. This combination of imaging and ecological pattern analysis to identify mechanisms driving the skin parasite landscape offers new perspectives on myeloid cell behavior following parasitism by L. donovani and may also be applicable to elucidating the behavior of other intracellular tissue-resident pathogens and their host cells.

Metagenomic Analysis Identifying a Rare Leishmania Infection in an Adult With AIDS

Leishmania belongs to a genus of the protozoan parasites that causes leishmaniasis, and includes cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). In this case, Leishmania amastigotes were found on cytomorphology examination of the bone marrow specimen, followed by 1,076 Leishmania donovani reads using metagenomic next generation sequencing (mNGS). Since being definitely diagnosed with VL/HIV coinfection, the patient was treated with liposomal amphotericin B as the parasite-resistant therapy and was discharged after clinical cure. But nearly a year later, on the mNGS follow-up, L. donovani was detected in the patient’s blood plasma specimen with 941 reads, suggesting that a relapse of leishmaniasis had occurred. These results indicate that leishmaniasis still exists in China and may represent a public health concern. This case could be helpful in the differential diagnosis of leishmaniasis, and for determining disease progression, prevention, and control of vectors and reservoir hosts.

Nonstandard RNA/RNA Interactions Likely Enhance Folding and Stability of Segmented Ribosomes.

The ribosome is the molecular factory that catalyzes all coded protein synthesis in extant organisms. Eukaryotic ribosomes are typically assembled out of four rRNAs, namely 5S, 5.8S, 18S, and 28S. However, the 28S rRNA of some trypanosomatid organisms has been found to be segmented into six independent rRNAs of different sizes. The two largest segments have multiple sites where they jointly form stems comprised of standard base pairs that can hold them together. However, such regions of interaction are not observed among the four smaller RNAs. Early reports suggested that trypanosomatid segmented ribosome assembly was essentially achieved thanks to their association with rProteins. However, examination of Cryo-EM ribosomal structures from Trypanosoma brucei, Leishmania donovani and Trypanosoma cruzi reveals several long-range nonstandard RNA/RNA interactions. Most of these interactions are clusters of individual hydrogen bonds and so are not readily predictable. However, taken as a whole, they represent significant stabilizing energy that likely facilitates rRNA assembly and the overall stability of the segmented ribosomes. In the context of origin of life studies, the current results provide a better understanding of the true nature of RNA sequence space and what might be possible without an RNA replicase.