Leishmania infantum NTPDase1 and NTPDase2 play an important role in infection and nitric oxide production in macrophages.

Leishmania infantum, the causative agent of American Visceral Leishmaniasis (VL), is known for its ability to modulate the host immune response to its own favor. Ecto-nucleoside triphosphate diphosphohydrolase (ENTPDase) represents a family of enzymes that hydrolyze nucleotides and are involved in nucleotide-dependent biological processes. L. infantum has two ENTPDases, namely LiNTPDase1 and LiNTPDase2. Here, we used genetic tools to overexpress or abolish the expression of LiNTPDase1 and -2 to assess their role in parasite growth in culture and macrophage infection. While LiNTPDase1 or 2-overexpressing clones showed no morphological or growth changes in promastigotes, LiNTPDase2 overexpression increased macrophage adhesion and infection by 50% and 30%, respectively. The individual LiNTPDase1 and 2 knockout mutants showed lag in growth profile, which was reversed by the addition of adenine and guanine to the culture media. Moreover, the morphology of the knockout mutants even in supplemented media was changed to an amastigote-like form. The double knockout of both genes was lethal and a mechanism of compensation of deletion of one isoform was detected in these mutants. Correspondingly, the absence of LiNTPDase1 or LiNTPDase2 led to a dramatic reduction in in vitro infection (∼90%). Interestingly, nitric oxide production was decreased in both knockout mutants during infection, which suggests that both LiNTPDases can inhibit macrophage responses against the parasite. Overall, our results show important roles of LiNTPDase1 and -2 concerning in vitro macrophage infection and reinforce their use as potential targets to control Leishmania infections.

Murine macrophages do not support the proliferation of Leishmania (Viannia) braziliensis amastigotes even in absence of nitric oxide and presence of high arginase activity.

Leishmania (Viannia) braziliensis is the main species responsible for American tegumentary leishmaniasis in Brazil. Nevertheless, the use of this parasite species to study Leishmania infection in the murine model has been less conducted when compared with other Leishmania species. The control of murine infection with Leishmania has been associated with nitric oxide (NO) produced by inducible NO synthase (iNOS) from M1 macrophages, while arginase expressed by M2 macrophages is related to Leishmania proliferation. Here we use three different strains of L. (V.) braziliensis and one strain of L. (L.) major to study a 9-day infection of macrophages in vitro. Wild-type bone marrow-derived macrophages (BMDM) supported the proliferation of L. (L) major amastigotes from the 3rd day after infection, while all strains of L. (V.) braziliensis did not proliferate even inside IL-4-treated or iNOS knockout (KO) macrophages. The arginase activity was higher in iNOS KO than IL-4-treated macrophage showing that the absence of proliferation is independent of arginase. Importantly, L. (V.) braziliensis was able to cause uncontrolled disease in iNOS KO mice in vivo demonstrating that murine macrophages present at the site of infection have additional changes beyond inhibition of NO production or stimulation of arginase activity to support parasite proliferation.

Impact of collaborative actions of Leishmania (Viannia) braziliensis subpopulations on the infection profile.

This study focuses on the role of the population structure of Leishmania spp. on the adaptive capacity of the parasite. Herein, we investigate the contribution of subpopulations of the L. (V.) braziliensis Thor strain (Thor03, Thor10 and Thor22) in the profile of murine macrophages infection. Infection assays were performed with binary combinations of these subpopulations at stationary phases. The initial interaction time showed major effects on the combination assays, as demonstrated by the significant increase in the infection rate at 5 h. Based on the endocytic index (EI), Thor10 (EI = 563.6) and Thor03 (EI = 497) showed a higher infection load compared to Thor22 (EI = 227.3). However, the EI decreased in Thor03 after 48 h (EI = 447) and 72 h (EI = 388.3) of infection, and showed changes in the infection level in all Thor10/Thor22 combinations. Assays with CellTrace CFSE-labelled Thor22 promastigotes indicated an increase (~1.5 fold) in infection by this subpopulation in the presence of Thor10 when compared to the infection profile of Thor03/Thor22 combinations in the same proportions. In addition, the potential of these subpopulations, alone or in binary combinations, to modulate the expression of cytokines and nitric oxide (NO) in vitro was investigated. Lower NO and tumour necrosis factor-α production levels were observed for all Thor10/Thor22 combinations at 24 h compared to these subpopulations alone. In contrast, Thor03/Thor22 combination assays increased IL-10 production at this time. Collectively, these results provide in vitro evidence on the potential of L. (V.) braziliensis population structure to play a relevant role in a host infection by this parasite.

In vitro Susceptibility of Human Cell Lines Infection by Bovine Leukemia Virus.

Evidence of the presence of bovine leukemia virus (BLV) in human beings and its association with breast cancer has been published in the literature, proposing it as a zoonotic infection. However, not enough evidence exists about transmission pathways nor biological mechanisms in human beings. This study was aimed at gathering experimental evidence about susceptibility of human cell lines to BLV infection. Malignant and non-malignant human cell lines were co-cultured with BLV-infected FLK cells using a cell-to-cell model of infection. Infected human cell lines were harvested and cultured for 3 to 6 months to determine stability of infection. BLV detection was performed through liquid-phase PCR and visualized through in situ PCR. Seven out of nine cell lines were susceptible to BLV infection as determined by at least one positive liquid-phase PCR result in the 3-month culture period. iSLK and MCF7 cell lines were able to produce a stable infection throughout the 3-month period, with both cytoplasmic and/or nuclear BLV-DNA visualized by IS-PCR. Our results support experimental evidence of BLV infection in humans by demonstrating the susceptibility of human cells to BLV infection, supporting the hypothesis of a natural transmission from cattle to humans.

Long-term infection passaging of Human Adenovirus 36 in monkey kidney cells

ABSTRACT Human Adenovirus 36 (HAdV-36) has been related to diverse effects on metabolism and may attenuate the lipid accumulation in kidneys with increased adiposity. Some of these effects would be related to viral persistence. However, until now, a model of persistent in vitro infection by HAdV-36 is unknown. In this study, we examined the cells of the Vero lineage to explore their permissiveness to long-term HAdV-36 infection. HAdV-36 was productively replicated in Vero cells and maintained long-term infection for up to 35 cell passages. A subculture was obtained from the cells that survived the primary infection at a low MOI (0.5). The production of the extracellular infectious virus with titers ranging from 104 to 106 TCID50/mL and DNA-bearing cells was detected. In long-term infected cells, the intracellular distribution of viral antigen was demonstrated by performing immunolocalization (IFI) and expression of cell-viral antigen in 50% of cells by flow cytometry, using anti-HAdV-36 hyperimmune rabbit serum. Furthermore, E1a and E4orf1 genes in long-term infected passages showed a decreasing trend. Our preliminary results reveal that renal epithelial monkey cells are permissive for the productive infection of HAdV-36. Vero cell culture long-term infection might be a promising model for addressing the fundamental aspects of the HAdV-36 biology that cannot reveal broadly-used cultures, which do not maintain long-term infection in primary or transformed cells.

Frequency and expression of genes involved in adhesion and biofilm formation in Staphylococcus aureus strains isolated from periodontal lesions.

BACKGROUND/PURPOSE: The aim of this study was to characterize the Staphylococcus aureus strains isolated from periodontal lesions of patients, to determine the expression of genes involved in cell adhesion upon their infection of human epithelial cells using an in vitro model, its biofilm formation, and its resistance to antibiotics. METHODS: S. aureus was analysed by PCR, Kirby-Bauer, and pulsed-field gel electrophoresis (PFGE), measuring gene expression by real-time PCR after infection of human cells in vitro. RESULTS: S. aureus was identified in 18.6% (50/268) of the samples. All strains (n = 50) possessed the virulence genes spa (Staphylococcal protein A), coa (coagulase), and icaAB (intercellular adhesin); 96% (n = 48) possessed clfB (clumping factor B), and 88% (n = 44) possessed ebps (elastin-binding protein) and sdrD (serine aspartate repeat protein D). All strains were resistant to methicillin, ampicillin, dicloxacillin, cefotaxime, and penicillin, and were multidrug resistant to 6-12 antibiotics. PFGE analysis showed 37 different pulsed-field types and most strains (60.4%) had a unique pulsed-field type. Twenty-four distinct combinations of virulence genes and antibiotic-resistant phenotypes were identified. CONCLUSION: Although S. aureus has been considered a transient member of the oral microbiota, our results indicate a high-level expression of virulence genes and multidrug resistance in the strains isolated from periodontal lesions. These strains might complicate the successful treatment of the disease.

In silico and in vitro Evaluation of Mimetic Peptides as Potential Antigen Candidates for Prophylaxis of Leishmaniosis.

Antigen formulation is the main feature for the success of leishmaniosis diagnosis and vaccination, since the disease is caused by different parasite species that display particularities which determine their pathogenicity and virulence. It is desirable that the antigens are recognized by different antibodies and are immunogenic for almost all Leishmania species. To overcome this problem, we selected six potentially immunogenic peptides derived from Leishmania histones and parasite membrane molecules obtained by phage display or spot synthesis and entrapped in liposome structures. We used these peptides to immunize New Zealand rabbits and determine the immunogenic capacity of the chimeric antigen. The peptides induced the production of antibodies as a humoral immune response against L. braziliensis or L. infantum. Next, to evaluate the innate response to induce cellular activation, macrophages from the peptide mix-immunized rabbits were infected in vitro with L. braziliensis or L. infantum. The peptide mix generated the IFN-γ, IL-12, IL-4 and TGF-ß that led to Th1 and Th2 cellular immune responses. Interestingly, this mix of peptides also induced high expression of iNOS. These results suggest that the mix of peptides derived from histone and parasites membrane molecules was able to mimic parasites proteins and induce cytokines important to CD4+ T cell Th1 and Th2 differentiation and effector molecule to control the parasite infection. Finally, this peptide induced an immune balance that is important to prevent immunopathological disorders, inflammatory reactions, and control the parasite infection.

Quantification of Parasite Loads by Automated Microscopic Image Analysis.

High content analysis enables automated, robust, and unbiased evaluation of in vitro Leishmania infection. Here, we describe a protocol based on the infection of THP-1 macrophages with Leishmania promastigotes and the quantification of parasite load by high content analysis. The technique is capable of detecting and quantifying intracellular amastigotes, providing a multiparametric readout of the total number of cells, ratio of infected cells, total number of parasites, and number of parasites per infected cells. The technique can be used to quantitate infection of any Leishmania species in virtually all types of permissive host cells and can be applied to quantification of drug activity and studies of the Leishmania intracellular life cycle stage.

Thymus vulgaris L. and thymol assist murine macrophages (RAW 264.7) in the control of in vitro infections by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans.

Microorganisms are capable to combat defense cells by means of strategies that contribute to their stabilization and proliferation in invaded tissues. Frequently antimicrobial-resistant strains appear; therefore, alternative methods to control them must be investigated, for example, the use of plant products. The capacity of the thyme extract (Thymus vulgaris L.) and phytocompound thymol in the control of in vitro infections by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans in murine macrophages (RAW 264.7) was evaluated. Minimal inhibitory concentrations (MIC) of the plant products were used. The effect of these MIC were analyzed in the assays of phagocytosis and immunoregulation by analysis of the production of cytokines (IL-1ß, TNF-α, and IL-10) and nitric oxide (NO). The plant products effectively assisted the macrophages in the phagocytosis of microorganisms, presenting significant reductions of S. aureus and P. aeruginosa. The macrophages also regulated the production of inflammatory mediators in the infections by S. aureus, P. aeruginosa, and C. albicans. In addition, thyme provided a satisfactory effect in response to the bacterial infections, regarding generation of NO. Thus, the effectiveness of the thyme and thymol to control in vitro infections by S. aureus, P. aeruginosa, and C. albicans was observed. HIGHLIGHTS: Phagocytosis of S. aureus by RAW 264.7 was enhanced with thymol Thyme enhanced the phagocytosis of P. aeruginosa by RAW 264.7 Plant products provided immunoregulation of inflammatory cytokines Production of nitric oxide was improved with the treatments in bacterial infections.

Comprehensive expression analysis of pathogenicity genes in uropathogenic Escherichia coli strains.

In this study, we investigated distinct expression patterns of genes encoding iron-acquisition systems, adhesins, protectins, and toxins in human uroepithelial cells infected with 194 uropathogenic Escherichia coli (UPEC) strains in vitro. We assessed the association of these genes with antibiotic resistance genes in this group of UPEC strains, previously characterised by polymerase chain reaction (PCR). Strains were isolated from patients with urinary tract infections (UTIs) from Unidad Médica Familiar de Salud Pública, located in Estado de México, México. Antibiotic resistance genes were identified by PCR, and the expression of virulence genes was detected by reverse-transcriptase-PCR after in vitro infection of cultured A431 human keratinocytes derived from a vulvar epidermoid carcinoma. The most frequently expressed virulence genotypes among the investigated UPEC strains included usp (68%), iha (64.9%), kpsMT (61.3%), fim (58.2%), irp2 (48.4), papC (33.5%), set (31.4%) and astA (30.9%), whereas the most frequently detected antibiotic resistance genes were tet(A) (34%), sul1 (31.4%) and TEM (26.3%). Furthermore, the most abundant pattern of gene expression (irp2/fim/iha/kpsMT/usp), associated with 8 different combinations of antibiotic resistance genotypes, was exhibited by 28 strains (14.4%). Taken together, these results indicate collective participation of distinct virulence UPEC genotypes during in vitro infection of cultured human epithelial cells, suggesting their potential involvement in UTI pathogenesis.

Wharton's jelly cells from sheep umbilical cord maintained with different culture media are permissive to in vitro infection by Small Ruminant Lentiviruses / Células da geleia de Wharton do cordão umbilical ovino mantidas em diferentes meios de cultivo são permissivas à infecção in vitro por lentivírus de pequenos ruminantes

This study aimed to isolate cells from the Wharton's jelly of umbilical cord (WJUC) of sheep collected during natural parturition using different culture media, in addition to reporting for the first time the permissiveness of these cells to in vitro infection by small ruminant lentiviruses. Ten umbilical cords were collected from healthy sheep. Each cord explants were grown in different media consisting of MEM, low glucose DMEM, M199, and RPMI-1640. The permissiveness of infection of sheep cells from WJUC was tested with CAEV-Cork and MVV-K1514 strains, inoculating 0.1 MOI of each viral strain. Four supernatants from each strain were obtained from WJUC sheep cell cultures infected in different media. The results demonstrated the presence of cytopathic effect after the in vitro infection by CAEV-Cork and MVV-K1514 with all of the tested culture media. Nested-PCR detected proviral DNA in all supernatants. Supernatants containing CAEV-Cork viruses had TCID 50/ml titres of 10 5.5 in MEM, 10 4.0 in low glucose DMEM, 105.0 in M199, and 10 5.7 in RPMI-1640. Supernatants containing the MVV-K1514 virus had TCID 50/ml titres of 10 4.3 in MEM, 10 3.5 in low-glucose DMEM, 10 4.7 in M199, and 10 3.5 in RPMI-1640. Sheep cells from WJUC are permissive to in vitro infection by small ruminant lentivirus.(AU)

O objetivo deste estudo foi isolar células da geleia de Wharton do cordão umbilical (GWCU) ovino coletado por ocasião do parto natural, utilizando-se diferentes meios de cultivo, além de relatar, pela primeira vez, sua permissividade à infecção in vitro por lentivírus de pequenos ruminantes (LVPRs). Dez cordões umbilicais foram coletados de ovelhas hígidas e soronegativas para LVPRs pelo teste de imunodifusão em gel de agarose (IDGA). De cada cordão, explantes foram cultivados em quatro meios distintos que consistiram em MEM, DMEM baixa glicose, meio 199 e RPMI-1640, todos acrescidos de 10% de soro fetal bovino em estufa com atmosfera úmida e 5% de CO2 a 37ºC. A permissividade de infecção das células GWCU ovino foi testada frente às cepas CAEV-Cork e MVV-K1514, inoculando-se 0,1 MOI de cada cepa viral e corando as monocamadas com May Grunwald Giemsa para visualização do efeito citopático. Foram obtidos quatro sobrenadantes CAEV-Cork e quatro MVV-K1514, provenientes do cultivo de células GWCU ovino infectadas por 21 dias em meios distintos, dos quais foram realizadas titulação em membrana sinovial caprina e extração do DNA pró-viral para realização de nested-PCR e eletroforese em gel de agarose a 2%. Os resultados demonstraram a presença de efeito citopático na infecção in vitro tanto por CAEV-Cork como por MVV-K1514 em todos os meios de cultivo, sendo visualizados sincícios e lise celular em microscópio invertido. A nested-PCR detectou o DNA pró-viral tanto do CAEV-Cork como do MVV-K1514 em todos os sobrenadantes. Os sobrenadantes contendo o vírus CAEV-Cork apresentaram títulos em TCID50/mL de 10 5,5 em MEM, 10 4,0 em DMEM baixa glicose, 10 5,0 em meio 199 e 10 5,7 em RPMI-1640. Os sobrenadantes contendo o vírus MVV-K1514 apresentaram título em TCID 50/mL de 10 4,3 em MEM, 10 3,5 em DMEM baixa glicose, 10 4,7 em meio 199 e 10 3,5 em RPMI-1640. Células GWCU ovino são permissivas à infecção in vitro pelos lentivírus de pequenos ruminantes CAEV-Cork e MVV-K1514.(AU)

Wharton's jelly cells from sheep umbilical cord maintained with different culture media are permissive to in vitro infection by Small Ruminant Lentiviruses / Células da geleia de Wharton do cordão umbilical ovino mantidas em diferentes meios de cultivo são permissivas à infecção in vitro por lentivírus de pequenos ruminantes

This study aimed to isolate cells from the Wharton's jelly of umbilical cord (WJUC) of sheep collected during natural parturition using different culture media, in addition to reporting for the first time the permissiveness of these cells to in vitro infection by small ruminant lentiviruses. Ten umbilical cords were collected from healthy sheep. Each cord explants were grown in different media consisting of MEM, low glucose DMEM, M199, and RPMI-1640. The permissiveness of infection of sheep cells from WJUC was tested with CAEV-Cork and MVV-K1514 strains, inoculating 0.1 MOI of each viral strain. Four supernatants from each strain were obtained from WJUC sheep cell cultures infected in different media. The results demonstrated the presence of cytopathic effect after the in vitro infection by CAEV-Cork and MVV-K1514 with all of the tested culture media. Nested-PCR detected proviral DNA in all supernatants. Supernatants containing CAEV-Cork viruses had TCID 50/ml titres of 10 5.5 in MEM, 10 4.0 in low glucose DMEM, 105.0 in M199, and 10 5.7 in RPMI-1640. Supernatants containing the MVV-K1514 virus had TCID 50/ml titres of 10 4.3 in MEM, 10 3.5 in low-glucose DMEM, 10 4.7 in M199, and 10 3.5 in RPMI-1640. Sheep cells from WJUC are permissive to in vitro infection by small ruminant lentivirus.(AU)

O objetivo deste estudo foi isolar células da geleia de Wharton do cordão umbilical (GWCU) ovino coletado por ocasião do parto natural, utilizando-se diferentes meios de cultivo, além de relatar, pela primeira vez, sua permissividade à infecção in vitro por lentivírus de pequenos ruminantes (LVPRs). Dez cordões umbilicais foram coletados de ovelhas hígidas e soronegativas para LVPRs pelo teste de imunodifusão em gel de agarose (IDGA). De cada cordão, explantes foram cultivados em quatro meios distintos que consistiram em MEM, DMEM baixa glicose, meio 199 e RPMI-1640, todos acrescidos de 10% de soro fetal bovino em estufa com atmosfera úmida e 5% de CO2 a 37ºC. A permissividade de infecção das células GWCU ovino foi testada frente às cepas CAEV-Cork e MVV-K1514, inoculando-se 0,1 MOI de cada cepa viral e corando as monocamadas com May Grunwald Giemsa para visualização do efeito citopático. Foram obtidos quatro sobrenadantes CAEV-Cork e quatro MVV-K1514, provenientes do cultivo de células GWCU ovino infectadas por 21 dias em meios distintos, dos quais foram realizadas titulação em membrana sinovial caprina e extração do DNA pró-viral para realização de nested-PCR e eletroforese em gel de agarose a 2%. Os resultados demonstraram a presença de efeito citopático na infecção in vitro tanto por CAEV-Cork como por MVV-K1514 em todos os meios de cultivo, sendo visualizados sincícios e lise celular em microscópio invertido. A nested-PCR detectou o DNA pró-viral tanto do CAEV-Cork como do MVV-K1514 em todos os sobrenadantes. Os sobrenadantes contendo o vírus CAEV-Cork apresentaram títulos em TCID50/mL de 10 5,5 em MEM, 10 4,0 em DMEM baixa glicose, 10 5,0 em meio 199 e 10 5,7 em RPMI-1640. Os sobrenadantes contendo o vírus MVV-K1514 apresentaram título em TCID 50/mL de 10 4,3 em MEM, 10 3,5 em DMEM baixa glicose, 10 4,7 em meio 199 e 10 3,5 em RPMI-1640. Células GWCU ovino são permissivas à infecção in vitro pelos lentivírus de pequenos ruminantes CAEV-Cork e MVV-K1514.(AU)

Expression of bacterial virulence factors and cytokines during in vitro macrophage infection by enteroinvasive Escherichia coli and Shigella flexneri: a comparative study

Enteroinvasive Escherichia coli (EIEC) and Shigellaspp cause bacillary dysentery in humans by invading and multiplying within epithelial cells of the colonic mucosa. Although EIEC and Shigellashare many genetic and biochemical similarities, the illness caused by Shigellais more severe. Thus, genomic and structure-function molecular studies on the biological interactions of these invasive enterobacteria with eukaryotic cells have focused on Shigella rather than EIEC. Here we comparatively studied the interactions of EIEC and of Shigella flexneriwith cultured J774 macrophage-like cells. We evaluated several phenotypes: (i) bacterial escape from macrophages after phagocytosis, (ii) macrophage death induced by EIEC and S. flexneri, (iii) macrophage cytokine expression in response to infection and (iv) expression of plasmidial (pINV) virulence genes. The results showed thatS. flexneri caused macrophage killing earlier and more intensely than EIEC. Both pathogens induced significant macrophage production of TNF, IL-1 and IL-10 after 7 h of infection. Transcription levels of the gene invasion plasmid antigen-C were lower in EIEC than in S. flexneri throughout the course of the infection; this could explain the diminished virulence of EIEC compared to S. flexneri.