Development of an amplicon-based sequencing approach in response to the global emergence of mpox.

The 2022 multicountry mpox outbreak concurrent with the ongoing Coronavirus Disease 2019 (COVID-19) pandemic further highlighted the need for genomic surveillance and rapid pathogen whole-genome sequencing. While metagenomic sequencing approaches have been used to sequence many of the early mpox infections, these methods are resource intensive and require samples with high viral DNA concentrations. Given the atypical clinical presentation of cases associated with the outbreak and uncertainty regarding viral load across both the course of infection and anatomical body sites, there was an urgent need for a more sensitive and broadly applicable sequencing approach. Highly multiplexed amplicon-based sequencing (PrimalSeq) was initially developed for sequencing of Zika virus, and later adapted as the main sequencing approach for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Here, we used PrimalScheme to develop a primer scheme for human monkeypox virus that can be used with many sequencing and bioinformatics pipelines implemented in public health laboratories during the COVID-19 pandemic. We sequenced clinical specimens that tested presumptively positive for human monkeypox virus with amplicon-based and metagenomic sequencing approaches. We found notably higher genome coverage across the virus genome, with minimal amplicon drop-outs, in using the amplicon-based sequencing approach, particularly in higher PCR cycle threshold (Ct) (lower DNA titer) samples. Further testing demonstrated that Ct value correlated with the number of sequencing reads and influenced the percent genome coverage. To maximize genome coverage when resources are limited, we recommend selecting samples with a PCR Ct below 31 Ct and generating 1 million sequencing reads per sample. To support national and international public health genomic surveillance efforts, we sent out primer pool aliquots to 10 laboratories across the United States, United Kingdom, Brazil, and Portugal. These public health laboratories successfully implemented the human monkeypox virus primer scheme in various amplicon sequencing workflows and with different sample types across a range of Ct values. Thus, we show that amplicon-based sequencing can provide a rapidly deployable, cost-effective, and flexible approach to pathogen whole-genome sequencing in response to newly emerging pathogens. Importantly, through the implementation of our primer scheme into existing SARS-CoV-2 workflows and across a range of sample types and sequencing platforms, we further demonstrate the potential of this approach for rapid outbreak response.

Bacterial persisters are a stochastically formed subpopulation of low-energy cells.

Persisters represent a small subpopulation of non- or slow-growing bacterial cells that are tolerant to killing by antibiotics. Despite their prominent role in the recalcitrance of chronic infections to antibiotic therapy, the mechanism of their formation has remained elusive. We show that sorted cells of Escherichia coli with low levels of energy-generating enzymes are better able to survive antibiotic killing. Using microfluidics time-lapse microscopy and a fluorescent reporter for in vivo ATP measurements, we find that a subpopulation of cells with a low level of ATP survives killing by ampicillin. We propose that these low ATP cells are formed stochastically as a result of fluctuations in the abundance of energy-generating components. These findings point to a general "low energy" mechanism of persister formation.

Comparative Effectiveness of COVID-19 Vaccines in Preventing Infections and Disease Progression from SARS-CoV-2 Omicron BA.5 and BA.2, Portugal.

We estimated comparative primary and booster vaccine effectiveness (VE) of SARS-CoV-2 Omicron BA.5 and BA.2 lineages against infection and disease progression. During April-June 2022, we implemented a case-case and cohort study and classified lineages using whole-genome sequencing or spike gene target failure. For the case-case study, we estimated the adjusted odds ratios (aORs) of vaccination using a logistic regression. For the cohort study, we estimated VE against disease progression using a penalized logistic regression. We observed no reduced VE for primary (aOR 1.07 [95% CI 0.93-1.23]) or booster (aOR 0.96 [95% CI 0.84-1.09]) vaccination against BA.5 infection. Among BA.5 case-patients, booster VE against progression to hospitalization was lower than that among BA.2 case-patients (VE 77% [95% CI 49%-90%] vs. VE 93% [95% CI 86%-97%]). Although booster vaccination is less effective against BA.5 than against BA.2, it offers substantial protection against progression from BA.5 infection to severe disease.

Epidemiology and genetic diversity of invasive Neisseria meningitidis strains circulating in Portugal from 2003 to 2020.

Invasive meningococcal disease (IMD) continues to be a public health problem due to its epidemic potential, affecting mostly children. We aimed to present a detailed description of the epidemiology of IMD in Portugal, including insights into the genetic diversity of Neisseria meningitidis strains. Epidemiological analysis included data from the Portuguese National Reference Laboratory of Neisseria meningitidis during 2003 to 2020. Since 2012, N. meningitidis isolates have also been assessed for their susceptibility to antibiotics and were characterized by whole genome sequencing. During 2003-2020, 1392 confirmed cases of IMD were analyzed. A decrease in the annual incidence rate was observed, ranging from 1.99 (2003) to 0.39 (2020), with an average case fatality rate of 7.1%. Serogroup B was the most frequent (69.7%), followed by serogroups C (9.7%), Y (5.7%), and W (2.6%). Genomic characterization of 329 isolates identified 20 clonal complexes (cc), with the most prevalent belonging to serogroup B cc41/44 (26.3%) and cc213 (16.3%). Isolates belonging to cc11 were predominantly from serogroups W (77.3%) and C (76.5%), whereas cc23 was dominant from serogroup Y (65.7%). Over the past 4 years (2017-2020), we observed an increasing trend of cases assigned to cc213, cc32, and cc11. Regarding antimicrobial susceptibility, all isolates were susceptible to ceftriaxone and 61.8% were penicillin-nonsusceptible, whereas 1.4% and 1.0% were resistant to ciprofloxacin and rifampicin. This is the first detailed study on the epidemiology and genomics of invasive N. meningitidis infections in Portugal, providing relevant data to public health policy makers for a more effective control of this disease.

Molecular Capture of Mycobacterium tuberculosis Genomes Directly from Clinical Samples: A Potential Backup Approach for Epidemiological and Drug Susceptibility Inferences.

The application of whole genome sequencing of Mycobacterium tuberculosis directly on clinical samples has been investigated as a means to avoid the time-consuming need for culture isolation that can lead to a potential prolonged suboptimal antibiotic treatment. We aimed to provide a proof-of-concept regarding the application of the molecular capture of M. tuberculosis genomes directly from positive sputum samples as an approach for epidemiological and drug susceptibility predictions. Smear-positive sputum samples (n = 100) were subjected to the SureSelectXT HS Target Enrichment protocol (Agilent Technologies, Santa Clara, CA, USA) and whole-genome sequencing analysis. A higher number of reads on target were obtained for higher smear grades samples (i.e., 3+ followed by 2+). Moreover, 37 out of 100 samples showed ≥90% of the reference genome covered with at least 10-fold depth of coverage (27, 9, and 1 samples were 3+, 2+, and 1+, respectively). Regarding drug-resistance/susceptibility prediction, for 42 samples, ≥90% of the >9000 hits that are surveyed by TB-profiler were detected. Our results demonstrated that M. tuberculosis genome capture and sequencing directly from clinical samples constitute a potential valid backup approach for phylogenetic inferences and resistance prediction, essentially in settings when culture is not routinely performed or for samples that fail to grow.

Genome-Scale Characterization of Mycobacterium abscessus Complex Isolates from Portugal.

The Mycobacterium abscessus complex (MABC) is an emerging, difficult to treat, multidrug-resistant nontuberculous mycobacteria responsible for a wide spectrum of infections and associated with an increasing number of cases worldwide. Dominant circulating clones (DCCs) of MABC have been genetically identified as groups of strains associated with higher prevalence, higher levels of antimicrobial resistance, and worse clinical outcomes. To date, little is known about the genomic characteristics of MABC species circulating in Portugal. Here, we examined the genetic diversity and antimicrobial resistance profiles of 30 MABC strains isolated between 2014 and 2022 in Portugal. The genetic diversity of circulating MABC strains was assessed through a gene-by-gene approach (wgMLST), allowing their subspecies differentiation and the classification of isolates into DCCs. Antimicrobial resistance profiles were defined using phenotypic, molecular, and genomic approaches. The majority of isolates were resistant to at least two antimicrobials, although a poor correlation between phenotype and genotype data was observed. Portuguese genomes were highly diverse, and data suggest the existence of MABC lineages with potential international circulation or cross-border transmission. This study highlights the genetic diversity and antimicrobial resistance profile of circulating MABC isolates in Portugal while representing the first step towards the implementation of a genomic-based surveillance system for MABC at the Portuguese NIH.

Global gene expression analysis of Streptococcus agalactiae at exponential growth phase.

A comparative overview of the global gene expression levels of S. agalactiae reference strain NEM316 at the exponential growth phase was done through RNA-sequencing. The expression levels of 47 genes potentially linked to virulence evidenced that: i) the major nuclease, GBS_RS03720/gbs0661, presented higher mean expression values than the remainder of DNase genes; ii) the genetic pilus island PI-2a genes presented higher mean expression values than PI-1 coding genes; and, iii) three virulence-associated genes ranked among the top-100 most expressed genes (GBS_RS07760, GBS_RS09445 and GBS_RS03485). Among this top-100, genes encoding proteins involved in "Translation, ribosomal structure and biogenesis" represented 46%. Curiously, genes with no assigned function were grouped in the category of highly expressed genes. As very little is known about the molecular mechanisms behind the release of DNases, preliminary assays were developed to understand whether direct DNA exposure would affect gene expression at the exponential growth phase. No differentially expressed genes were detected, indicating that follow-up studies are needed to disclose the complex molecular pathways (and stimuli) triggering the release of DNases. In general, our insights on the global expression levels of NEM316 at exponential growth phase with and without DNA exposure should open novel research lines to decipher S. agalactiae puzzling adaptation and virulence mechanisms, such as DNase production.

Tracking SARS-CoV-2 lineage B.1.1.7 dissemination: insights from nationwide spike gene target failure (SGTF) and spike gene late detection (SGTL) data, Portugal, week 49 2020 to week 3 2021.

We show that the SARS-CoV-2 B.1.1.7 lineage is highly disseminated in Portugal, with the odds of B.1.1.7 proportion increasing at an estimated 89% (95% confidence interval: 83-95%) per week until week 3 2021. RT-PCR spike gene target late detection (SGTL) can constitute a useful surrogate to track B.1.1.7 spread, besides the spike gene target failure (SGTF) proxy. SGTL/SGTF samples were associated with statistically significant higher viral loads, but not with substantial shift in age distribution compared to non-SGTF/SGTL cases.

EMA Review of Daratumumab (Darzalex) for the Treatment of Adult Patients Newly Diagnosed with Multiple Myeloma.

The use of daratumumab in combination with established regimens for the treatment of newly diagnosed multiple myeloma has recently been authorized by the European Medicines Agency based on results from three separate phase III randomized, active controlled, open-label studies that have confirmed enhanced efficacy and tolerability in both transplant-ineligible (MMY3008 and MMY3007) and transplant-eligible (MMY3006) patients, without compromising transplant ability. Trial MMY3008 showed an improvement in progression-free survival (PFS) when daratumumab was added to lenalidomide and dexamethasone compared with lenalidomide and dexamethasone; the median PFS had not been reached in the daratumumab arm and was 31.9 months in the control arm (hazard ratio [HR], 0.56; 95% confidence interval [CI], 0.43-0.73; p < .0001). Trial MMY3007 showed an improvement in PFS when daratumumab was added to bortezomib, melphalan, and prednisone compared with bortezomib, melphalan, and prednisone; PFS had not been reached in the daratumumab arm and was 18.1 months in the control arm (HR, 0.5; 95% CI, 0.38-0.65; p < .0001). In trial MMY3006, daratumumab added to bortezomib, thalidomide, and dexamethasone was compared with bortezomib, thalidomide, and dexamethasone as induction and consolidation treatment prior to autologous stem cell transplant. The stringent complete response rate at day 100 after transplant in the daratumumab group was 29% compared with 20% in the control group (odds ratio, 1.60; 1.21-2.12 95% CI; p = .0010). Overall adverse events were manageable, with an increased rate of neutropenia and infections in the daratumumab arms. Regulatory assessment of efficacy and safety results from trials MMY3006, MMY3007, and MMY3008 confirmed a positive benefit-risk ratio leading to an approval of the extensions of indication. IMPLICATIONS FOR PRACTICE: A set of extensions of indication was recently approved for daratumumab (Darzalex) in the setting of newly diagnosed multiple myeloma in combination with established regimens. Results of the MMY3006, MMY3007, and MMY3008 trials have shown enhanced efficacy and a favorable side effect profile of several daratumumab-based combinations in patients both ineligible and eligible for transplant, without compromising transplant ability. The combinations of daratumumab with either lenalidomide and low-dose dexamethasone or bortezomib, melphalan, and prednisone were approved for transplant-ineligible patients. The combination of daratumumab with bortezomib, thalidomide, and dexamethasone was approved for transplant-eligible patients. These combinations are expected to improve the survival outlook for patients with multiple myeloma, without an unacceptable risk of increase in adverse events, and updated information on progression-free survival and overall survival is expected from the above trials.

Cephalosporin-Resistant Neisseria gonorrhoeae Isolated in Portugal, 2019.

We report a multidrug-resistant Neisseria gonorrhoeae exhibiting resistance to ceftriaxone and cefixime, isolated in Portugal in 2019. Whole-genome sequencing was performed for typing and identification of genetic determinants of antimicrobial resistance. Because of its antimicrobial susceptibility profile, awareness should be raised for the circulation of this strain.

Quality of life in patients with systemic lupus erythematosus: the mediator role of psychological morbidity and disease activity.

Patients with systemic lupus erythematosus (SLE) experience chronic symptoms that negatively impact their quality of life (QoL). This study analyzed the variables that contributed to QoL in patients with SLE, including the mediating role of psychological morbidity and disease activity. This study used a transversal design and included 104 women with SLE. Participants answered several instruments assessing fatigue, psychological morbidity (depression and anxiety), body image, disease activity, and quality of life. The results showed that disease activity, fatigue severity, psychological morbidity and body image were associated with all domains of QoL. Additionally, psychological morbidity and disease activity mediated the relationship between body image and psychological morbidity. Also, disease activity mediated the relationship between body image and fatigue severity. According to the results, intervention in patients with SLE should focus on patients' psychological morbidity, particularly in the active phase of the disease. Body image, fatigue severity and psychological morbidity should be monitored in patients with SLE in order to promote QoL.

Changes in aortic pulse wave components, pulse pressure amplification, and hemodynamic parameters of children and adolescents with type 1 diabetes.

BACKGROUND/OBJECTIVE: Type 1 diabetes mellitus (DM1) presents important risk factors for cardiovascular events. OBJECTIVE: To compare the components of the aortic pulse wave (APW) and the hemodynamic parameters among children and adolescents with DM1 and healthy individuals. METHODS: This is a cross-sectional study, with 36 children and adolescents diagnosed with DM1 (11.9 ± 3.2 years) matched by sex and age with the control group (n = 36, 12.4 ± 2.9 years). The components of the APW and the hemodynamic parameters were evaluated non-invasively, using Mobil-O-Graph. RESULTS: On the week of the evaluation, DM1 patients presented glycated hemoglobin (hemoglobin A1C [HbA1c]) of 9.48 ± 2.22% and fasting glycemia of 222.58 ± 93.22 mg/dL. Augmentation index (AIx@75), reflection coefficient, and augmentation pressure (AP) were significantly higher in the DM1 group (29.0 ± 9.7%, 63.0 ± 7.9, and 7.8 ± 2.7 mm Hg, respectively) compared with the control group (20.6 ± 7.9%, 53.4 ± 9.1 and 4.9 ± 2.1 mm Hg, respectively). The systolic volume (52.6 ± 11.9 and 60 ± 12.4 mL) and the cardiac output (4.3 ± 0.5 and 4.6 ± 0.5 L/min) decreased in the DM1 group in relation to the control group. The pulse pressure amplification (PPA) was significantly lower in the DM1 group (1.4 ± 0.15) compared with the control group (1.6 ± 0.17). PPA correlated negatively with total vascular resistance (TVR), AP and reflection coefficient, and positively with cardiac index in both groups. In the DMI group, the AIx@75 correlated negatively with age, height, systolic volume, and PPA, and correlated positively with the TVR and reflection coefficient. CONCLUSIONS: These results confirm the presence of arterial stiffness in this population and extend the knowledge, showing, for the first time, the reduction of PPA in the DM1 group.

Evolutionary Origins of Rhizarian Parasites.

The SAR group (Stramenopila, Alveolata, Rhizaria) is one of the largest clades in the tree of eukaryotes and includes a great number of parasitic lineages. Rhizarian parasites are obligate and have devastating effects on commercially important plants and animals but despite this fact, our knowledge of their biology and evolution is limited. Here, we present rhizarian transcriptomes from all major parasitic lineages in order to elucidate their evolutionary relationships using a phylogenomic approach. Our results suggest that Ascetosporea, parasites of marine invertebrates, are sister to the novel clade Apofilosa. The phytomyxean plant parasites branch sister to the vampyrellid algal ectoparasites in the novel clade Phytorhiza. They also show that Ascetosporea + Apofilosa + Retaria + Filosa + Phytorhiza form a monophyletic clade, although the branching pattern within this clade is difficult to resolve and appears to be model-dependent. Our study does not support the monophyly of the rhizarian parasitic lineages (Endomyxa), suggesting independent origins for rhizarian animal and plant parasites.

Identification of a type I nitroreductase gene in non-virulent Trypanosoma rangeli.

Trypanosomatid type I nitroreductases (NTRs), i.e., mitochondrial enzymes that metabolise nitroaromatic pro-drugs, are essential for parasite growth, infection, and survival. Here, a type I NTR of non-virulent protozoan Trypanosoma rangeli is described and compared to those of other trypanosomatids. The NTR gene was isolated from KP1(+) and KP1(-) strains, and its corresponding transcript and 5' untranslated region (5'UTR) were determined. Bioinformatics analyses and nitro-drug activation assays were also performed. The results indicated that the type I NTR gene is present in both KP1(-) and KP1(+) strains, with 98% identity. However, the predicted subcellular localisation of the protein differed among the strains (predicted as mitochondrial in the KP1(+) strain). Comparisons of the domains and 3D structures of the NTRs with those of orthologs demonstrated that the nitroreductase domain of T. rangeli NTR is conserved across all the strains, including the residues involved in the interaction with the FMN cofactor and in the tertiary structure characteristics of this oxidoreductase protein family. mRNA processing and expression were also observed. In addition, T. rangeli was shown to be sensitive to benznidazole and nifurtimox in a concentration-dependent manner. In summary, T. rangeli appears to have a newly discovered functional type I NTR.

Association of metabolic syndrome and chronic periodontitis in Colombians.

BACKGROUND: Metabolic syndrome (MetS) is a common chronic condition that increases the cardiovascular disease risk and is also linked to periodontitis. The study aim was to determine if a relationship exists between MetS and chronic periodontitis in adult Colombians. METHODS: Participants were 220 healthy-gingivitis subjects and 431 periodontitis patients coming from the three largest Colombian cities. Periodontal status and MetS were determined in subjects. Univariate analysis and odds ratio were calculated within the 95 % confidence intervals and chi2 test compared the groups. Variables were compared among the clinical periodontal groups and MetS by Wilcoxon and multivariate analysis, and logistic regression was performed for MetS and periodontitis. RESULTS: MetS had higher prevalence in periodontitis group (6.3 %) versus controls (3.2 %). In multivariate analysis, periodontitis was associated with MetS (adjusted OR = 2.72, 95 % CI 1.09-6.79), glucose intolerance with another component of MetS (adjusted OR = 1.78, 1.16 to 2.72), glucose resistance (adjusted OR = 11.46, 95 % CI 1.41-92.88), smoking (OR = 1.72, 95 % CI 1.09-2.71), and city of origin (2.69, 95 % CI 1.79-4.04). CONCLUSION: The study confirmed the positive association between MetS and periodontitis, being glucose sensitivity the strongly associated component. CLINICAL RELEVANCE: MetS must be taken into account by the dentist when evaluating risk factors for periodontitis, being useful for dentists to evaluate glycemia, lipidic profile, central obesity, and high blood pressure in patients. Interdisciplinary treatment must be recommended when a patient with MetS and periodontitis is being treated.

Dietary Apigenin Exerts Immune-Regulatory Activity in Vivo by Reducing NF-κB Activity, Halting Leukocyte Infiltration and Restoring Normal Metabolic Function.

The increasing prevalence of inflammatory diseases and the adverse effects associated with the long-term use of current anti-inflammatory therapies prompt the identification of alternative approaches to reestablish immune balance. Apigenin, an abundant dietary flavonoid, is emerging as a potential regulator of inflammation. Here, we show that apigenin has immune-regulatory activity in vivo. Apigenin conferred survival to mice treated with a lethal dose of Lipopolysaccharide (LPS) restoring normal cardiac function and heart mitochondrial Complex I activity. Despite the adverse effects associated with high levels of splenocyte apoptosis in septic models, apigenin had no effect on reducing cell death. However, we found that apigenin decreased LPS-induced apoptosis in lungs, infiltration of inflammatory cells and chemotactic factors' accumulation, re-establishing normal lung architecture. Using NF-κB luciferase transgenic mice, we found that apigenin effectively modulated NF-κB activity in the lungs, suggesting the ability of dietary compounds to exert immune-regulatory activity in an organ-specific manner. Collectively, these findings provide novel insights into the underlying immune-regulatory mechanisms of dietary nutraceuticals in vivo.

Comparative analysis on natural spawning of F1 meagre, Argyrosomus regius, with wild broodstock spawns in Portugal.

The purpose of this study was to describe and compare the reproductive success and egg and larvae quality between wild and first-generation (F1) breeders of Argyrosomus regius. Wild broodstock were adapted to captivity, and good-quality spawns were obtained in 2009-2010, after GnRH treatment. In 2012, the F1 meagre (3 years old) spawned naturally at IPMA's Aquaculture Research Station facilities. From each spawning event, the following parameters were determined: number of floating and non-floating eggs, egg size, hatching success and larval total length. Eggs size and percentage of hatching obtained from F1 breeders (1.04 ± 0.10 mm and 90.5 ± 6.4%) were significantly higher when compared with wild breeders (0.97 ± 0.13 mm and 17.0 ± 12.7%). Although wild breeder spawns exhibited 2.7 ± 0.2 mm for larval total length, F1 breeder spawns presented 2.6 ± 0.2 mm. The wild and F1 breeder spawns exhibit a good egg and larval quality, indicating a promising starting point for a successful meagre hatchery production.

Assessing the potential of native copepods in Guatemala for Aedes vector control.

BACKGROUND: In this study we examine the feeding efficiency of copepods locally found in Guatemala on first instar Aedes aegypti larvae. Copepods are a potential tool for Aedes vector control that has shown promising results in the laboratory and in community-based field trials. METHODS: Four different copepod species from different habitat types were included in the laboratory assays of this study. RESULTS: All four tested copepod species decreased the number of the first instar Aedes larvae that were inserted into the glass vessels compared with controls. However, average predation rates between the tested species were highly different, with Thermocyclops crassus and Mesocyclops longisetus achieving the highest, with 31.0% (standard deviation [SD] 18.9) and 28. 9% (SD 11.2), respectively. CONCLUSIONS: The copepod species with identified high predation rates are potential candidates for planned and other future field trials for community-based Aedes vector control with copepods in the region.

Glycogen phase separation drives macromolecular rearrangement and asymmetric division in E. coli.

Bacteria often experience nutrient limitation in nature and the laboratory. While exponential and stationary growth phases are well characterized in the model bacterium Escherichia coli, little is known about what transpires inside individual cells during the transition between these two phases. Through quantitative cell imaging, we found that the position of nucleoids and cell division sites becomes increasingly asymmetric during transition phase. These asymmetries were coupled with spatial reorganization of proteins, ribosomes, and RNAs to nucleoid-centric localizations. Results from live-cell imaging experiments, complemented with genetic and 13C whole-cell nuclear magnetic resonance spectroscopy studies, show that preferential accumulation of the storage polymer glycogen at the old cell pole leads to the observed rearrangements and asymmetric divisions. In vitro experiments suggest that these phenotypes are likely due to the propensity of glycogen to phase separate in crowded environments, as glycogen condensates exclude fluorescent proteins under physiological crowding conditions. Glycogen-associated differences in cell sizes between strains and future daughter cells suggest that glycogen phase separation allows cells to store large glucose reserves without counting them as cytoplasmic space.

Differences in systemic and skin migrating-specific CD4 T cells in papular urticaria by flea bite.

BACKGROUND: Papular urticaria by flea bite is a chronic allergic condition in which clinical improvement may occur at the age of 7 years, thus representing a natural model of acquired immunologic tolerance in humans. The aim of this study was to characterize regulatory cells and specific responses to flea antigens of CD4(+) T lymphocytes expressing cutaneous migration markers in patients with papular urticaria caused by flea bite and with different disease evolution times. METHODS: Cell populations were characterized by flow cytometry in samples from patients and healthy controls. Specific cell stimulation was performed with a complete flea body extract. The Mann-Whitney U test was used for comparisons. RESULTS: Total dendritic cells were lower in patients than in healthy controls. No quantitative differences were found in CD4 regulatory T cells. CD4(+) T cells from patients produced more IL-4, lL-10, IL-17, and IFN-γ. Patients who experienced the onset of symptoms within the first 5 years of age showed a greater percentage of local (cutaneous lymphocyte antigen +) IL-4- and IL-17-producing cells, while patients who experienced the onset of symptoms after the age of 5 years had a higher percentage of systemic (cutaneous lymphocyte antigen -) IL-10-producing cells. CONCLUSION: Analysis of the cellular immune response against whole flea antigen in patients with papular urticaria by flea bites suggests a possible participation of inflammatory cytokines in the skin reaction (Th17) and a systemic control mechanism (IL-10). This pattern of cytokine production in patients could be a consequence of an impaired dendritic cell population.