Predominance of CD137+ And TNF-α Expressing CD8+ Central Memory T Cells in Mild COVID-19 Recovered Patients Upon SARS-CoV-2 Re-Exposure.

INTRODUCTION: Memory CD8+ T cells are essential for long-term immune protection in viral infections, including COVID-19. METHODS: This study examined the responses of CD8+ TEM, TEMRA, and TCM subsets from unvaccinated individuals who had recovered from mild and severe COVID-19 by flow cytometry. RESULTS AND DISCUSSION: The peptides triggered a higher frequency of CD8+ TCM cells in the recovered mild group. CD8+ TCM and TEM cells showed heterogeneity in CD137 expression between evaluated groups. In addition, a predominance of CD137 expression in naïve CD8+ T cells, TCM, and TEM was observed in the mild recovered group when stimulated with peptides. Furthermore, CD8+ TCM and TEM cell subsets from mild recovered volunteers had higher TNF-α expression. In contrast, the expression partner of IFN-γ, IL-10, and IL-17 indicated an antiviral signature by CD8+ TEMRA cells. These findings underscore the distinct functional capabilities of each memory T cell subset in individuals who have recovered from COVID-19 upon re-exposure to SARS-CoV-2 antigens.

Is IFN expression by NK cells a hallmark of severe COVID-19?

Natural Killer cells (NK) are crucial in host defense against viruses. There are many unanswered questions about the immune system in COVID-19, especially the mechanisms that contribute to the development of mild or severe forms of the disease. Although NK cells may have an essential role in the pathogenesis of COVID-19, the mechanisms involved in this process are not yet fully elucidated. Here, we demonstrate that CD3-CD56+ NK cells frequency in the volunteers who recovered from mild COVID-19 (Mild CoV) presented a significant increase compared to the healthy control (HC) and individuals recovering from severe COVID-19 (Severe CoV) groups. Furthermore, distinct IFN profiles in recovered COVID-19 patients with mild or severe clinical forms of the disease were observed in the total NK cells (CD3-CD56+). In the first group, NK cells express increased levels of IFN-α compared to the severe CoV, while higher production of IFN-γ in severe CoV was found. Moreover, NK cells in mild CoV express more cytolytic granules depicted by granzyme B and perforin. Compared to HC, PBMCs from mild CoV presented higher Ki-67 and TIM-3 production after Pool CoV-2 and Pool Spike CoV-2 peptides stimulus. In addition, non-stimulated PBMCs in the mild CoV group had higher NK TIM-3+ frequency than severe CoV. In the mild CoV group, Pool Spike CoV-2 and Pool CoV-2 peptides stimuli elicited higher granzyme B and perforin coexpression and IFN-α production by PBMCs. However, in severe CoV, Pool Spike CoV-2 reduced the coexpression of granzyme B, perforin, and CD107a suggesting a decrease in the cytotoxic activity of NK cells. Therefore, our study shows that NK cells may have a crucial role in COVID-19 with the involvement of IFN-α and cytotoxic properties that aid in developing qualified immune responses. Furthermore, the data suggest that higher amounts of IFN-γ may be linked to the severity of this disease.

Phenotypical characterization of regulatory T cells in acute Zika infection.

Zika virus (ZIKV), alongside Dengue virus (DENV), Chikungunya virus (CHIKV), and Yellow Fever Virus (YFV) are prevalent arboviruses in the Americas. Each of these infections is associated with the development of associated disease immunopathology. Immunopathological processes are an outcome of counter-balancing impacts between effector and regulatory immune mechanisms. In this context, regulatory T cells (Tregs) are key in modulating the immune response and, therefore, in tissue damage control. However, to date, Treg phenotypes and mechanisms during acute infection of the ZIKV in humans have not been fully investigated. The main aim of this work was to characterize Tregs and their immunological profile related to cytokine production and molecules that are capable of controlling the exacerbated inflammatory profile in acute Zika infected patients. Using whole blood analyses of infected patients, an ex vivo phenotypical characterization of Tregs, circulating during acute Zika virus infection, was conducted by flow cytometry. We found that though there are no differences in absolute Treg frequency between infected and healthy control groups. However, pro-inflammatory cytokine up-regulation such as IFN-γ and LAP was observed in the acute disease. Furthermore, acute ZIKV patients expressed increased levels of CD39/CD73, perforin/granzyme B, PD-1, and CTLA-4, all markers involved in mechanisms used by Tregs to attempt to control strong inflammatory responses. Thus, the data indicates a potential contribution of Tregs during the inflammatory ZIKV infection response.

Spotted fever group Rickettsia and Borrelia sp. cooccurrence in Amblyomma sculptum in the Midwest region of Brazil.

More than 70 tick species are found in Brazil, distributed over five genera and including main vectors of infectious disease agents affecting both animals and humans. The genus Amblyomma is the most relevant for public health in Brazil, wherein Amblyomma aureolatum, Amblyomma ovale and Amblyomma sculptum have been incriminated as vectors of Rickettsia and Borrelia pathogens. The objective of this study was to investigate the presence of Rickettsia spp. and Borrelia spp. in ticks in the Brazilian mid-western savannah. DNA extraction, PCR for Borrelia spp. (flgE gene) and Rickettsia spp. (ompA and gltA genes) and subsequent sequencing were performed. A total of 1875 ticks were collected and identified as A. sculptum except for two Amblyomma coelebs ticks. Molecular evidence for Borrelia spp. and Rickettsia parkeri was found in A. sculptum. This is the first molecular evidence for R. parkeri in A. sculptum ticks in the Midwest region and Borrelia spp. circulating in a tick of the Amblyomma genus in Brazil.

Correlation between Rhipicephalus microplus ticks and Anaplasma marginale infection in various cattle breeds in Brazil.

The tick Rhipicephalus microplus is responsible for the transmission of Anaplasma marginale, which causes hemolytic anemia, abortion, decreased production, and mortality in cattle in Brazil. However, A. marginale can also persist in cattle herds without any clinical signs. This study investigated the relationship between the number of ticks present on each cattle and the circulating number of A. marginale msp1ß gene copies in the blood of Brangus and Nellore cattle reared in the Brazilian Cerrado through a year period. Twenty-three animals (11 Brangus and 12 Nellore) were raised for 12 months with ticks counted every 18 days, and blood collected every 36 days. Blood sera was used for total antigen iELISA, genomic DNA was extracted from whole blood by the phenol/chloroform method and then analyzed by PCR to confirm A. marginale presence with the msp5 gene. Positive samples were quantified by qPCR using msp1ß gene. Brangus cattle presented 4.5 fold more ticks than Nellore group. Although Brangus cattle carried a higher overall A. marginale msp1ß gene presence than Nellore cattle, no relationship of tick count and copy number could be achieved due to high variability in copy number. Moreover, both breeds showed similar weight gain and a similar serological pattern throughout the year. None of the animals showed any clinical signs of anaplasmosis during the experimental period, indicating that a low level of tick infestation may be sufficient to maintain a stable enzootic situation.

Differential regulatory T cell signature after recovery from mild COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is characterized by a range of symptoms in which host immune response have been associated with disease progression. However, the putative role of regulatory T cells (Tregs) in determining COVID-19 outcomes has not been thoroughly investigated. Here, we compared peripheral Tregs between volunteers not previously infected with SARS-CoV-2 (healthy control [HC]) and volunteers who recovered from mild (Mild Recovered) and severe (Severe Recovered) COVID-19. Peripheral blood mononuclear cells (PBMC) were stimulated with SARS-CoV-2 synthetic peptides (Pool Spike CoV-2 and Pool CoV-2) or staphylococcal enterotoxin B (SEB). Results of a multicolor flow cytometric assay showed higher Treg frequency and expression of IL-10, IL-17, perforin, granzyme B, PD-1, and CD39/CD73 co-expression in Treg among the PBMC from the Mild Recovered group than in the Severe Recovered or HC groups for certain SARS-CoV-2 related stimulus. Moreover, Mild Recovered unstimulated samples presented a higher Tregs frequency and expression of IL-10 and granzyme B than did that of HC. Compared with Pool CoV-2 stimuli, Pool Spike CoV-2 reduced IL-10 expression and improved PD-1 expression in Tregs from volunteers in the Mild Recovered group. Interestingly, Pool Spike CoV-2 elicited a decrease in Treg IL-17+ frequency in the Severe Recovered group. In HC, the expression of latency-associated peptide (LAP) and cytotoxic granule co-expression by Tregs was higher in Pool CoV-2 stimulated samples. While Pool Spike CoV-2 stimulation reduced the frequency of IL-10+ and CTLA-4+ Tregs in PBMC from volunteers in the Mild Recovered group who had not experienced certain symptoms, higher levels of perforin and perforin+granzyme B+ co-expression by Tregs were found in the Mild Recovered group in volunteers who had experienced dyspnea. Finally, we found differential expression of CD39 and CD73 among volunteers in the Mild Recovered group between those who had and had not experienced musculoskeletal pain. Collectively, our study suggests that changes in the immunosuppressive repertoire of Tregs can influence the development of a distinct COVID-19 clinical profile, revealing that a possible modulation of Tregs exists among volunteers of the Mild Recovered group between those who did and did not develop certain symptoms, leading to mild disease.

T Cell Response in Tuberculosis-Infected Patients Vaccinated against COVID-19.

Many studies have focused on SARS-CoV-2 and Mycobacterium tuberculosis (Mtb) co-infection consequences. However, after a vaccination plan against COVID-19, the cases of severe disease and death are consistently controlled, although cases of asymptomatic and mild COVID-19 still happen together with tuberculosis (TB) cases. Thus, in this context, we sought to compare the T cell response of COVID-19-non-vaccinated and -vaccinated patients with active tuberculosis exposed to SARS-CoV-2 antigens. Flow cytometry was used to analyze activation markers (i.e., CD69 and CD137) and cytokines (IFN-γ, TNFα, IL-17, and IL-10) levels in CD4+ and CD8+ T cells upon exposure to SARS-CoV-2 peptides. The data obtained showed that CD8+ T cells from non-vaccinated TB patients present a high frequency of CD69 and TNF-α after viral challenge compared to vaccinated TB donors. Conversely, CD4+ T cells from vaccinated TB patients show a high frequency of IL-10 after spike peptide stimulus compared to non-vaccinated patients. No differences were observed in the other parameters analyzed. The results suggest that this reduced immune balance in coinfected individuals may have consequences for pathogen control, necessitating further research to understand its impact on clinical outcomes after COVID-19 vaccination in those with concurrent SARS-CoV-2 and Mtb infections.

Seasonal fluctuations of Babesia bigemina and Rhipicephalus microplus in Brangus and Nellore cattle reared in the Cerrado biome, Brazil.

BACKGROUND: The tick Rhipicephalus microplus (Ixodida: Ixodidae, Canestrini, 1888) causes substantial economic and health losses in cattle production and is the main vector of Babesia bigemina (Piroplasmidae: Babesidae, Smith & Kilborne, 1893). Babesia bigemina is responsible for a tick-borne disease known as babesiosis that can cause hemolytic anemia, fever and death. In the study reported here, we investigated the relationship between the number of ticks per animal and the number of B. bigemina cytochrome b gene (cbisg) copies in the blood of Brangus and Nellore cattle reared without acaricidal treatment in the Brazilian Cerrado biome over a 1-year period. METHODS: Ticks on 19 animals (9 Brangus and 10 Nellore cattle) were counted every 18 days, and blood was collected every 36 days for 12 months. Serological samples were analyzed with an indirect enzyme-linked immunosorbent assay, and genomic DNA was analyzed by conventional PCR and quantitative PCR. The PCR products were sequenced by the Sanger method. RESULTS: The Brangus and Nellore breeds showed similar weight development and no clinical signs of babesiosis. Statistically significant differences (P < 0.05) between the breeds were observed for the number of ticks and the number of B. bigemina cbisg gene copies. CONCLUSIONS: No correlation between the number of ticks and the number of circulating copies of cbisg was observed, although Nellore cattle presented with fewer ticks than Brangus cattle and the number of cbisg copies was higher for Nellore cattle than for Brangus cattle.

Serological and molecular detection of Neospora caninum and Toxoplasma gondii in human umbilical cord blood and placental tissue samples.

Neosporosis primarily affects cattle and dogs and is not currently considered a zoonotic disease. Toxoplasmosis is a zoonosis with a worldwide distribution that is asymptomatic in most cases, but when acquired during pregnancy, it can have serious consequences. The seropositivity rates determined by the indirect fluorescent antibody test for Neospora caninum (N. caninum) and Toxoplasma gondii (T. gondii) were 24.3% (49 samples) and 26.8% (54 samples), respectively. PCR positivity for N. caninum was observed in two samples of cord blood (1%) using the Nc5 and ITS1 gene, positivity for T. gondii was observed in 16 samples using the primer for the B1 gene (5.5% positivity in cord blood and 2.5% positivity in placental tissue). None of the samples showed structures characteristic of tissue cysts or inflammatory infiltrate on histopathology. Significant associations were observed only between N. caninum seropositivity and the presence of domestic animals (p = 0.039) and presence of dogs (p = 0.038) and between T. gondii seropositivity and basic sanitation (p = 0.04). This study obtained important findings regarding the seroprevalence and molecular detection of N. caninum and T. gondii in pregnant women; however, more studies are necessary to establish a correlation between risk factors and infection.

Prediction of Conserved Peptides of Paracoccidioides for Interferon-γ Release Assay: The First Step in the Development of a Lab-Based Approach for Immunological Assessment during Antifungal Therapy.

Impaired antigen-specific cell-mediated immunity (CMI) is a primary immunological disturbance observed in individuals that develop paracoccidioidomycosis (PCM) after exposure to Paracoccidioides spp. Restoration of Paracoccidioides-specific CMI is crucial to stop the antifungal treatment and avoid relapses. A convenient and specific laboratory tool to assess antigen specific CMI is required for the appropriate clinical treatment of fungal infections, in order to decrease the time of antifungal therapy. We used an interferon-γ release assay strategy, used in the diagnosis of latent tuberculosis infection, to address our aims in this study. Information on proteins secreted by two well-studied representative strains-Paracoccidioides brasiliensis (Pb18) and P. lutzii (Pb-01)-were explored using PubMed or MEDLINE. From 26 publications, 252 proteins were identified, of which 203 were similar according to the Basic Local Alignment Search Tool. This enabled a selection of conserved peptides using the MEGA software. The SignalP-5.0, TMHMM, IEDB, NetMHC II, and IFNepitope algorithms were used to identify appropriate epitopes. In our study, we predicted antigenic epitopes of Paracoccidioides that could bind to MHC class II and induce IFN-γ secretion. These T cell epitopes can be used in the development of a laboratory tool to monitor the CMI of patients with PCM.

Serological evaluation of Neospora caninum in pregnant women treated at referral center for prenatal screening in Mato Grosso do Sul, Brazil.

Neospora caninum is an obligate intracellular protozoan with canids (Canis domesticus, Canis lupus dingo, Canis latrans, Canis lupus) as its definitive hosts. The objective of this study was to detect anti-N. caninum antibodies in pregnant women seen at referral center for prenatal screening in the state of state Mato Grosso do Sul, Brazil. A total of 188 serum samples from pregnant women provided by the Instituto de Pesquisa, Ensino e Diagnósticos da APAE de Campo Grande (IPED/ APAE) were subjected to IFA test and western blot analysis. The samples were divided into three groups: 23/99 samples from the seropositive group for toxoplasmosis were positive for anti-N. caninum IgG antibodies, and 9/99 positive for IgM; in the HIV group, 7/33 were positive for IgG; and in the HIV+toxoplasmosis group, 13/56 were positive for IgG and two positive for IgM. The seropositivity for IgG was assessed by western blot by testing 43 IFA test positive samples using rNcSRS2 (Nc-p43) as antigen. The serological results of the present study suggest that exposure of these pregnant women to the parasite N. caninum and presence of IgM antibodies are indicative of recent infection. Further studies are needed to establish the possibility of active infection.

Amblyomma scalpturatum Neumann, 1906 (Acari: Ixodidae): confirmation in Acre State, Brazil, and description of parasitism in a human.

Amblyomma scalpturatum is a tick species that is unique to South America. It is commonly associated with the Amazon biome and has been reported in some Brazilian states. This tick species exhibits host specificity: it parasitizes tapirs and suidae. Its role in transmitting pathogens to humans is still unknown. Amblyomma scalpturatum is known to be a human-biting tick; however, there is only one report showing that humans make suitable hosts for this species. The knowledge of tick fauna is lacking in the Acre State. This study collected free-living ticks with the aim of finding new records in Acre State. Collections were carried out in Amazon forest fragments in Rio Branco municipality. An A. scalpturatum specimen was identified and submitted sequencing of the ITS-2 gene. This study presents the first molecular confirmation of A. scalpturatum collected in situ in Acre State, North Region, Brazil. This study also presents the first record of a successfully completed feeding by an A. scalpturatum nymph on a human host in the North region of Brazil. Further investigation is needed to ascertain the complete life cycle of this tick species, its seasonality in the environment, and its relationship to pathogens and competence to transmit them.

Molecular characterization of the recombinant protein RmLTI-BmCG-LTB: Protective immunity against Rhipicephalus (Boophilus) microplus.

The bovine tick Rhipicephalus (Boophilus) microplus is found in several tropical and subtropical regions of the world. This parasite transmits pathogens that cause disease, such as babesiosis (Babesia bovis and B. bigemina) and anaplasmosis (Anaplasma marginale). Tick infestations cause enormous livestock losses, and controlling tick infestations and the transmission of tick-borne diseases remains a challenge for the livestock industry. Because the currently available commercial vaccines offer only partial protection against R. (B.) microplus, there is a need for more efficient vaccines. Several recombinant antigens have been evaluated using different immunization strategies, and they show great promise. This work describes the construction and immunological characterization of a multi-antigen chimera composed of two R. (B.) microplus antigens (RmLTI and BmCG) and one Escherichia coli antigen (B subunit, LTB). The immunogenic regions of each antigen were selected and combined to encode a single polypeptide. The gene was cloned and expressed in E. coli. For all of the experiments, two groups (treated and control) of four Angus heifers (3-6 months old) were used. The inoculation was performed via intramuscular injection with 200 µg of purified recombinant chimeric protein and adjuvated. The chimeric protein was recognized by specific antibodies against each subunit and by sera from cattle inoculated with the chimera. Immunization of RmLTI-BmCG-LTB cattle reduced the number of adult female ticks by 6.29% and vaccination of cattle with the chimeric antigen provided 55.6% efficacy against R. (B.) microplus infestation. The results of this study indicate that the novel chimeric protein is a potential candidate for the future development of a more effective vaccine against R. (B.) microplus.

New records of tick-associated spotted fever group Rickettsia in an Amazon-Savannah ecotone, Brazil.

Human rickettsiosis has been recorded in the Amazon Biome. However, the epidemiological cycle of causative rickettsiae has not been fully accounted for in the Amazon region. This study investigates the presence of spotted fever group (SFG) Rickettsia spp. in free-living unfed ticks of the Amblyomma genus. The study was conducted in seven municipalities in Rondonia State, Brazil, where the main biomes are Amazon forest, Brazilian Savannah and their ecotones (areas of ecological tension between open ombrophilous forest and savannah). The following tick species were collected: Amblyomma cajennense (sensu lato) s.l., A. cajennense (sensu stricto) s.s., A. coelebs, A. naponense, A. oblongoguttatum, A. romitii, A. scalpturatum and A. sculptum. A total of 167 adults, 248 nymphs and 1004 larvae were subjected to DNA extraction and polymerase chain reaction (PCR) to determine the presence of SFG Rickettsia spp. PCR-positive samples included: one A. cajennense s.s. female and one A. cajennense s.l. male from a rural area in Vilhena Municipality; 10 nymphs and a sample of larvae of A. cajennense s.l. from a peri-urban area in Cacoal Municipality; and an A. oblongoguttatum adult male from a rural area of Pimenta Bueno Municipality. All sequences obtained exhibited 100% identity with Rickettsia amblyommatis sequences. This is the first confirmation of SFG Rickettsia in an A. oblongoguttatum tick. Furthermore, this is the first record of SFG Rickettsia in the municipalities targeted by this study. These results warn that SFG Rickettsia circulation poses a threat in Rondonia State (among Amazon-Savannah ecotones), and that this threat is increased by the fact that SFG Rickettsia infect a human-biting tick species hitherto unconfirmed as a vector.

Analysis of Bm86 conserved epitopes: is a global vaccine against Cattle Tick Rhipicephalus microplus possible?

The cattle tick Rhipicephalus microplus causes significant economic losses in agribusiness. Control of this tick is achieved mainly through the application of chemical acaricides, often resulting in contamination of animal food products and of the environment. Another major concern associated with acaricide use is the increasing reports of resistance of this tick vector against the active ingredients of many commercial products. An alternative control method is vaccination. However, the commercially available vaccine based on a protein homologous to Bm86 exhibits variations in efficacy relative to the different geographical locations. This study aimed to identify antigenic determinants of the sequences of proteins homologous to Bm86. Phylogenetic analyses were performed to determine the extent of divergence between different populations of R. microplus to identify the sequence that could be used as a universal vaccine against the multiple geographically distinct populations of R. microplus and related tick species. Considering the extensive sequence and functional polymorphism observed among strains of R. microplus from different geographical regions, we can conclude that it may be possible to achieve effective vaccination against these cattle ticks using a single universal Bm86-based antigen.

New insights from molecular characterization of the tick Rhipicephalus (Boophilus) microplus in Brazil.

The Rhipicephalus (Boophilus) microplus complex currently consists of five taxa, namely R. australis, R. annulatus, R. (B.) microplus clade A sensu, R. microplus clade B sensu, and R. (B.) microplus clade C sensu. Mitochondrial DNA-based methods help taxonomists when they are facing the morpho-taxonomic problem of distinguishing members of the R. (B.) microplus complex. The purpose of this study was to perform molecular characterization of ticks in all five regions of Brazil and infer their phylogenetic relationships. Molecular analysis characterized 10 haplotypes of the COX-1 gene. Molecular network analysis revealed that haplotype H-2 was the most dispersed of the studied populations (n = 11). Haplotype H-3 (n = 2) had the greatest genetic differentiation when compared to other Brazilian populations. A Bayesian phylogenetic tree of the COX-1 gene obtained strong support. In addition, it was observed that the population of R. (B.) microplus haplotype H-3 exhibited diverging branches among the other Brazilian populations in the study. The study concludes that the different regions of Brazil have R. (B.) microplus tick populations with distinct haplotypes.

Spotted fever group Rickettsia in Amblyomma dubitatum tick from the urban area of Campo Grande, Mato Grosso do Sul, Brazil.

Rickettsia infection of each tick was evaluated by the hemolymph test and polymerase chain reaction (PCR) targeting gltA and ompA genes. All hemolymph tests were negative and PCR of one A. dubitatum detected both Rickettsia genes. Sequence of ompA exhibited a 99% identity with Rickettsia parkeri and R. africae and a 98% identity with R. sibirica. Rickettsia of the spotted fever group in A. dubitatum is described for the first time in an urban area within the municipality of Campo Grande in the state of Mato Grosso do Sul (MS), Brazil. This finding reinforces the importance of more detailed studies to determine the role of A. dubitatum in the transmission of spotted fever agents.

Geographical distribution of Trypanosoma cruzi in triatomine vectors in the State of Mato Grosso do Sul, Brazil.

INTRODUCTION: This work presents the initial findings of a molecular epidemiological investigation of Trypanosoma cruzi in triatomine insects in State of Mato Grosso do Sul. METHODS: A total of 511 triatomines from different regions of the state were examined. Deoxyribonucleic acid (DNA) was extracted from the intestinal contents of the insects using phenol-chloroform-isoamyl alcohol (25:24:1). Polymerase chain reaction (PCR) using primers 121/122 targeting DNA kinetoplast (kDNA) was then performed to identify T. cruzi, and positive samples were subjected to PCR using the primer pair TcSC5D-F/R followed by restriction fragment length polymorphism (RFLP) with the restriction enzymes SphI and HpaI (1 U/reaction), cloning and sequencing. RESULTS: One hundred samples were positive for T. cruzi, and three discrete typing units (DTUs) were identified (TcI, TcII, and TcBat). Triatoma sordida had the highest T. cruzi occurrence (83.3%), and DTUs were found in three samples: 58.3% of the samples were TcI, 33.3% were TcII and 8.3% were TcBat. There was a clear geographical distribution of the DTUs throughout the state, with TcI, TcII and TcBat located in the center, TcI located in the east, and TcII located in the west. CONCLUSIONS: This study showed the occurrence of overlapping DTUs in State of Mato Grosso do Sul. The distributions of the DTUs were different, with TcI, TcII and TcBat in the center of the state, TcI predominantly in the east, and TcII in the west. Further studies may reveal a more defined mosaic distribution of DTUs in MS.

Amblyomma scalpturatum Neumann, 1906 (Acari: Ixodidae): confirmation in Acre State, Brazil, and description of parasitism in a human / Amblyomma scalpturatum Neumann, 1906 (Acari: Ixodidae): confirmação no Estado do Acre, Brasil, e descrição de parasitismo em um humano

Abstract Amblyomma scalpturatum is a tick species that is unique to South America. It is commonly associated with the Amazon biome and has been reported in some Brazilian states. This tick species exhibits host specificity: it parasitizes tapirs and suidae. Its role in transmitting pathogens to humans is still unknown. Amblyomma scalpturatum is known to be a human-biting tick; however, there is only one report showing that humans make suitable hosts for this species. The knowledge of tick fauna is lacking in the Acre State. This study collected free-living ticks with the aim of finding new records in Acre State. Collections were carried out in Amazon forest fragments in Rio Branco municipality. An A. scalpturatum specimen was identified and submitted sequencing of the ITS-2 gene. This study presents the first molecular confirmation of A. scalpturatum collected in situ in Acre State, North Region, Brazil. This study also presents the first record of a successfully completed feeding by an A. scalpturatum nymph on a human host in the North region of Brazil. Further investigation is needed to ascertain the complete life cycle of this tick species, its seasonality in the environment, and its relationship to pathogens and competence to transmit them.

Resumo Amblyomma scalpturatum é uma espécie de carrapato que ocorre apenas na América do Sul. Está comumente associada ao bioma da Amazônia e tem sido relatada em alguns estados brasileiros. Esta espécie de carrapato apresenta especificidade a hospedeiros: parasita antas e suídeos. Sua competência em transmitir agentes patogênicos a seres humanos é ainda desconhecida. Amblyomma scalpturatum é também conhecido por picar seres humanos; entretanto, há apenas um relato que evidencie que seres humanos sejam capazes de serem hospedeiros adequados. Ainda existem lacunas no conhecimento sobre a ixodofauna no estado do Acre. Neste estudo foram coletados carrapatos de vida livre com o objetivo de encontrar novos registros para o estado do Acre. Coletas de carrapatos foram realizadas em fragmentos de floresta Amazônica no município de Rio Branco. Um exemplar de A. scalpturatum foi identificado e submetido a sequenciamento do gene ITS-2. Este estudo apresenta a primeira confirmação molecular de A. scalpturatum coletado in situ no estado do Acre, região Norte, Brasil. Este estudo também apresenta o primeiro relato de parasitismo completo de uma ninfa de A. scalpturatum em um hospedeiro humano na região Norte do Brasil. Mais investigações são necessárias para elucidar o ciclo de vida completo dessa espécie de carrapato, a sazonalidade de seus estádios no meio ambiente, sua relação a agentes patogênicos e competência em transmiti-los.

Analysis of Bm86 conserved epitopes: is a global vaccine against Cattle Tick Rhipicephalus microplus possible? / Análise de epítopos conservados da Bm86: é possível uma vacina global contra Carrapato-do-Boi Rhipicephalus microplus?

Abstract The cattle tick Rhipicephalus microplus causes significant economic losses in agribusiness. Control of this tick is achieved mainly through the application of chemical acaricides, often resulting in contamination of animal food products and of the environment. Another major concern associated with acaricide use is the increasing reports of resistance of this tick vector against the active ingredients of many commercial products. An alternative control method is vaccination. However, the commercially available vaccine based on a protein homologous to Bm86 exhibits variations in efficacy relative to the different geographical locations. This study aimed to identify antigenic determinants of the sequences of proteins homologous to Bm86. Phylogenetic analyses were performed to determine the extent of divergence between different populations of R. microplus to identify the sequence that could be used as a universal vaccine against the multiple geographically distinct populations of R. microplus and related tick species. Considering the extensive sequence and functional polymorphism observed among strains of R. microplus from different geographical regions, we can conclude that it may be possible to achieve effective vaccination against these cattle ticks using a single universal Bm86-based antigen.

Resumo O carrapato Rhipicephalus microplus é responsável por perdas significativas no agronegócio. O controle deste carrapato é feito principalmente por meio da aplicação de acaricidas químicos, geralmente resultando na contaminação de produtos de origem animal e do meio ambiente. Outra preocupação importante associada ao uso de acaricidas é o crescente aumento de relatos sobre a resistência deste carrapato a princípios ativos de vários produtos comerciais. Uma alternativa de controle é por meio de vacinação. Porém, a vacina comercializada contendo proteína homóloga à Bm86, apresenta variações de eficácia em relação às diferentes localizações geográficas. Este estudo buscou identificar determinantes antigênicos das sequencias de proteínas homólogas a Bm86. As análises filogenéticas foram feitas para determinar a extensão da divergência entre diferentes populações de R. microplus com o objetivo de identificar a sequência que poderia ser usada como vacina universal contra as múltiplas populações geograficamente distintas de R. microplus e espécies de carrapatos relacionados. Considerando-se a extensa sequência e o polimorfismo observados entre linhagens de R. microplus de diferentes regiões geográficas, podemos concluir que pode ser possível obter uma vacinação efetiva contra esses carrapatos bovinos utilizando um único antígeno universal baseado em Bm86.