The influence of intestinal parasites on Plasmodium vivax-specific antibody responses to MSP-119 and AMA-1 in rural populations of the Brazilian Amazon.

BACKGROUND: Polyparasitism is a common condition in humans but its impact on the host immune system and clinical diseases is still poorly understood. There are few studies of the prevalence and the effect of malaria-intestinal parasite co-infections in the immune response to malaria vaccine candidates. The present study determines whether the presence of malaria and intestinal parasites co-infection is associated with impaired IgG responses to Plasmodium vivax AMA-1 and MSP-119 in a rural population of the Brazilian Amazon. METHODS: A cross-sectional survey was performed in a rural area of Rondonia State and 279 individuals were included in the present study. At recruitment, whole blood was collected and Plasmodium and intestinal parasites were detected by microscopy and molecular tests. Blood cell count and haemoglobin were also tested and antibody response specific to P. vivax AMA-1 and MSP-119 was measured in plasma by ELISA. The participants were grouped according to their infection status: singly infected with Plasmodium (M); co-infected with Plasmodium and intestinal parasites (CI); singly infected with intestinal parasites (IP) and negative (N) for both malaria and intestinal parasites. RESULTS: The prevalence of intestinal parasites was significantly higher in individuals with malaria and protozoan infections were more prevalent. IgG antibodies to PvAMA-1 and/or PvMSP-119 were detected in 74 % of the population. The prevalence of specific IgG was similar for both proteins in all four groups and among the groups the lowest prevalence was in IP group. The cytophilic sub-classes IgG1 and IgG3 were predominant in all groups for PvAMA-1 and IgG1, IgG3 and IgG4 for PvMSP-119. In the case of non-cytophilic antibodies to PvAMA-1, IgG2 was significantly higher in IP and N group when compared to M and CI while IgG4 was higher in IP group. CONCLUSIONS: The presence of intestinal parasites, mainly protozoans, in malaria co-infected individuals does not seem to alter the antibody immune responses to P. vivax AMA-1 and MSP-119. However, IgG response to both AMA1 and MSP1 were lower in individuals with intestinal parasites.

Clinical and parasitological protection in a Leishmania infantum-macaque model vaccinated with adenovirus and the recombinant A2 antigen.

BACKGROUND: Visceral leishmaniasis (VL) is a severe vector-born disease of humans and dogs caused by Leishmania donovani complex parasites. Approximately 0.2 to 0.4 million new human VL cases occur annually worldwide. In the new world, these alarming numbers are primarily due to the impracticality of current control methods based on vector reduction and dog euthanasia. Thus, a prophylactic vaccine appears to be essential for VL control. The current efforts to develop an efficacious vaccine include the use of animal models that are as close to human VL. We have previously reported a L. infantum-macaque infection model that is reliable to determine which vaccine candidates are most worthy for further development. Among the few amastigote antigens tested so far, one of specific interest is the recombinant A2 (rA2) protein that protects against experimental L. infantum infections in mice and dogs. METHODOLOGY/PRINCIPAL FINDINGS: Primates were vaccinated using three rA2-based prime-boost immunization regimes: three doses of rA2 plus recombinant human interleukin-12 (rhIL-12) adsorbed in alum (rA2/rhIL-12/alum); two doses of non-replicative adenovirus recombinant vector encoding A2 (Ad5-A2) followed by two boosts with rA2/rhIL-12/alum (Ad5-A2+rA2/rhIL12/alum); and plasmid DNA encoding A2 gene (DNA-A2) boosted with two doses of Ad5-A2 (DNA-A2+Ad5-A2). Primates received a subsequent infectious challenge with L. infantum. Vaccines, apart from being safe, were immunogenic as animals responded with increased pre-challenge production of anti-A2-specific IgG antibodies, though with some variability in the response, depending on the vaccine formulation/protocol. The relative parasite load in the liver was significantly lower in immunized macaques as compared to controls. Protection correlated with hepatic granuloma resolution, and reduction of clinical symptoms, particularly when primates were vaccinated with the Ad5-A2+rA2/rhIL12/alum protocol. CONCLUSIONS/SIGNIFICANCE: The remarkable clinical protection induced by A2 in an animal model that is evolutionary close to humans qualifies this antigen as a suitable vaccine candidate against human VL.

In situ characterization of the granulomatous immune response with time in nonhealing lesional skin of Leishmania braziliensis-infected rhesus macaques (Macaca mulatta).

We have recently introduced a macaque (Macaca mulatta) model of Leishmania braziliensis-induced self-healing cutaneous leishmaniasis in which the T cell-mediated inflammatory response effectively promotes parasite clearance and granuloma resolution. Here we show that macaques infected with a highly pathogenic L. braziliensis strain displayed longstanding granulomatous lesions which lasted until the end of the observation period (52 weeks). Immunoperoxidase staining of representative tissue sections indicated that distinct cell populations (CD3, CD4, CD8, CD20, Foxp3, CD20, CD68, HLA-DR, CCL2, and CXCL-10) change uniformly during infection, suggesting that the same components of the local immune response are working in unison. This model also confirmed that granuloma formation is orchestrated by diverse inflammatory mediators that are important for T helper type 1 (Th1) cell development and macrophage effector functions. Cytometry analysis of ex vivo granuloma-derived leukocytes revealed accumulation of distinct functional subsets of effector and regulatory T cells into the inflamed skin. We provide evidence that local interleukin (IL)-10 production by both Foxp3(+) and Foxp3(-) CD4(+) T subsets is likely important in promoting lesional granuloma maintenance. Further studying the immune suppression mechanisms that induces granulomas in L. braziliensis-infected macaques may reveal new opportunities for therapeutic control of this important human disease.

Impact of 3 years ivermectin treatment on onchocerciasis in Yanomami communities in the Brazilian Amazon.

In the current study, it was assessed, for the first time, the effect of ivermectin treatment administered twice a year on the prevalence and morbidity of onchocerciasis in the hyperendemic Yanomami communities of the Roraima State (Brazil). Physical and parasitological examinations were carried out every 6 months until six drug rounds of treatment were completed. The coverage during the six rounds of ivermectin treatment ranged from 89% to 92% of the eligible Yanomami population. Overall, comparison of results at pre-treatment with results after six rounds of treatment, the prevalence of infection had declined from 87% to 42% (P<0.0001, CI 95%=0.05-0.22); the community microfilarial load (CMFL) fell from 1.17 to 0.53Mf/mg of skin; and the crude intensity of infection (MFL-Total) decreased from 18.95 to 1.96Mf/mg of skin during the same period (P<0.0001, for both microfilarial loads). Although no significant difference was observed between microfilarial densities in skin snips from iliac crest and scapula after the 6th round of ivermectin treatment it was observed that the prevalence of positive skin snips was significantly higher when skin snips were taken from iliac crest (42%) than from scapula (8%) (P=0.001, CI 95%=3.41-22.67). After six rounds of ivermectin treatments, no significant differences were observed in the prevalences of palpable nodules and of onchodermatitis in relation to pre-treatment prevalences, from 45% to 41% and from 17% to 20% (P>0.05, for both). These findings suggest that mass population treatment should continue without interruption and achieve higher levels of drug coverage in order to alleviate disease manifestations and interrupt infection transmission to hasten the elimination of onchocerciasis in Yanomami communities. In addition, the sensitivity of iliac crest snips for parasitological assessment in epidemiological surveillance of Yanomami communities may increase the acceptance of the population in biopsy sampling and seems to be a good choice for assessing the success of control programs.

A biologia da Leishmania (Viannia) braziliensis no modelo experimental primata Macaca mulatta / The biology of the Leishmania (Viannia) braziliensis in the experimental model primate Macaca mulatta

Infecções naturais com o protozoário parasita Leishmania (Viannia) braziliensis Vianna 1911 (Kinetoplastida: Trypanosomatidae) causam doença humana em várias áreas (sub )tropicais no continente Americano (em pelo menos 15 países), constituindo um importante problema de saúde pública. A leishmaniose cutânea (LC) pela L. (V.) braziliensis distingue-se de outras formas da doença pela maior cronicidade, latência e morbidade da infecção, com tendência para ocorrer lesões metastáticas na pele e/ou mucosa nasofaríngea. Estudos taxonômicos têm revelado o polimorfismo genético em populações naturais de L. (V.) braziliensis, porém os fatores de risco envolvidos na expressão clínica diferenciada da doença são ainda obscuros. Nossos estudos sobre infecções com L. (V.) braziliensis em macacos rhesus (Macaca mulatta) foram feitos para caracterizar a evolução de diferentes cepas do patógeno e as respostas imunes adaftativas neste modelo experimental. Um inóculo padronizado de promastigotas (10 ) foi injetado, via intradérmica, na arcada superciliar ou no antebraço de cada macaco. As infecções de longa duração (25-33 meses) reproduziram as úlceras cutâneas auto-resolutivas ou persistentes, assim como a LC crônica recidivante devido à reativação da infecção latente. O decurso da lesão primária foi muito variável, não somente para os isolados mostrando diferenças moleculares, mas também para animais individuais em grupos infectados com a mesma cepa do parasito.

Entretanto, 80% dos símios infectados com o isolado de lesão disseminada desenvolveram lesões metastáticas persistentes na pele e/ou mucosa. Digno de nota, o comprometimento granulomatoso da mucosa nasal foi observado em 2 de 33 (6%) dos rhesus infectados. A persistência do parasito em lesões ativas ou cicatrizadas foi documentada na maioria dos primatas. Foram caracterizados genótipos específicos representando parasitos isolados de humanos e macacos (contudo, sem ter havido qualquer relação aparente com fenótipos clínicos específicos), confirmando assim a estrutura genética multiclonal de L. (V.) braziliensis. Respostas imunes adaptativas específicas (Le., anticorpos anti-Leishmania e reações in vivo e in vitro de linfócitos T específicos) foram induzidas no decurso das infecções. A resistência clínica à L. (V.) braziliensis foi aparentemente associada com a resposta T H1 específica, e os animais curados da infecção primária adquiriram imunidade protetora sólida contra re-infecção homóloga (Parasitology 2003, 127:437-447). Em outro estudo (Am J Trop Med Hyg 2004, 71 :297-305), demonstramos a variabilidade relativa em ensaios de proteção cruzada entre diferentes espécies ou cepas variantes de Leishmania em macacos rhesus.

A investigação mais detalhada da resposta imune neste sistema primata poderá esclarecer fatores relevantes influenciando a proteção heteróloga. O modelo macaco rhesus-L. (V.) braziliensis foi também explorado para avaliar a eficácia leishmanicida do antimoniato de Nmetillglucamina (J Parasitol 2005, 91:976-978). As respostas terapêuticas nos animais experimentais usando doses reduzida e convencional (5 e 20 mg/kg/dia por 28 dias, respectivamente) de Sbv foram similares aos de pacientes com LC. Os primatas curaram suas lesões após o tratamento, porém com parasitismo críptico e/ou recidiva. Concluindo, como a resposta granulomatosa à L. (V.) braziliensis em M. mulatta reproduz a patologia humana, este modelo torna-se útil para estudar a fisiopatologia/eventos imunoregulatórios associados com a evolução da doença, assim como em testes pré-clínicos de novas drogas e vacinas candidatas.

Inquérito sorológico para a infecção por Toxoplasma gondii em ameríndios isolados, Mato Grosso / Serological survey of Toxoplasma gondii infection in isolated Amerindians, Mato Grosso

Este estudo determinou a ocorrência de anticorpos anti-Toxoplasma gondii em população indígena do Mato Grosso, os Enawenê-Nawê. Estes habitam uma vasta região selvagem, com raros contatos com não-índios. Não apresentam animais domésticos, inclusive gatos. A dieta é baseada em insetos, mandioca, milho, mel e fungos e não se alimentam de carne, exceto de peixe. Com base no exposto, desenvolveu-se análise sorológica, por meio de ELISA - IgG e IFI - IgG e IgM. De 148 soros, 80,4 por cento foram ELISA ou IFI- IgG positivos. Não foram detectados casos de IgM reagentes. Nesse grupo as taxas de soropositividade aumentaram significativamente com a idade, de 50 por cento a 95 por cento. Analisando-se os hábitos e costumes, aliados à alta soropositividade encontrada, sugere-se que a presença de felinos silvestres nas imediações da aldeia e coleções de água poderia ter papel importante como fonte de infecção, contaminando o solo e, conseqüentemente, os insetos e fungos consumidos pelos índios.

Human retroviruses (HIV and HTLV) in Brazilian Indians: seroepidemiological study and molecular epidemiology of HTLV type 2 isolates.

To investigate serological, epidemiological, and molecular aspects of HTLV-1, HTLV-2, and HIV-1 infections in Amerindian populations in Brazil, we tested 683 and 321 sera from Tiriyo and Waiampi Indians, respectively. Both HIV-1 and HTLV-2 infections were detected at low prevalence among the Tiriyos whereas only HTLV-1 was present among the Waiampis, also at low prevalence. Analysis of the nucleotide sequence of the 631 bp of the env gene obtained from the three HTLV-2 isolates detected among the Tiriyos demonstrated by restriction fragment length polymorphism that these viruses belong to subtype IIa. Phylogenetic analysis of this same fragment showed that these sequences cluster closer to HTLV-2 isolates from intravenous drug users living in urban areas of southern Brazil than to the same gene sequence studied in another Brazilian tribe, the Kayapos. Our results confirm the distribution of Brazilian HTLV-2 sequences in a unique cluster I and cluster IIa and suggest that there is a considerable degree of diversity within this cluster. We also report for the first time HIV-1 infection among Brazilian Amerindians.