The causative agent of malignant tertian malaria, Plasmodium falciparum undergoes an arrested growth phenotype of its erythrocytic stage when under drug-stress. Recent artemisinin treatment failures seem to be indicative of such induction followed by recrudescence rather than actual therapeutic failure. Likewise, P. vivax hypnozoites are the prototypic dormants and the latent infections for which they are responsible prove most difficult to treat. Dihydroartemisinin, an artemisinin-derivative, can be used to exploit this mechanism by inducing a dormant state in ring-stage P. falciparum parasites and in turn, their recovery may be used as a screening period for compounds that inhibit or foster growth. Specifically, parasites stably transfected with luciferase were used to quantitatively observe growth (or lack thereof) response of parasites to the phytohormone gibberellic acid and the herbicide, fluridone. Using their behavior as comparative controls, the Medicines for Malaria Venture (MMV) Malaria Box was screened for similar activity. The most active compound, 1,2,3,4-tetrahydroacridin-9-ol a quinoline-derivate caused cells to wake even earlier than expected. Since quinine and other such drugs have historically been most effective in treating malaria, it seems appropriate that such a finding was made. Following this the MMV Box was screened again against uninduced 3D7 parasites to determine if any were capable of causing a dormant response under the hypothesis that such a reaction is a defensive adaptation of P. falciparum. Four compounds were found to be active of which two appear to be inducing dormancy in the second cycle rather than the first akin to DHA. These quiescent periods also appear to be shorter indicating that the latter is more efficient. It is possible that given the length of interaction with artemisinin, P. falciparum is more adept to respond to its derivatives likewise the mechanism of action may be different enough to change the nature of the response.

Neste trabalho, usamos um modelo murino de recrudescência da malária associada à gravidez, com camundongos BALB/c infectados por Plasmodium berghei ANKAGFP com o objetivo de avaliar a resposta imune associada ao recrudescimento da infecção. Observando as populações de células do baço por citometria de fluxo notou-se um aumento no percentual de células CD4+, CD19+, TCR <font face=\"Symbol\">g<font face=\"Symbol\">d+, GR1+ nos animais infectados, em relação aos controles não infectados. Não foram observadas diferenças no percentual de leucócitos placentários. Além disso, nossos resultados mostraram que no baço, linfócitos TCD4+ e TCD8+ estão mais ativados em fêmeas recrudescentes, enquanto que na placenta, estes animais apresentaram um aumento na ativação de células TCD4+. A relação IgG2a/IgG1 em animais ecrudescentes e não recrudescentes indicou um aumento de 3 vezes na produção de IgG2a que indica um padrão Th1 de resposta imune. A análise de qRT-PCR concomitantemente à citometria de fluxo evidenciou que células dendríticas são os reservatórios do parasita durante o estágio crônico da doença, que antecede o recrudescimento. Juntos, esses dados sugerem que a recrudescência durante a gestação está diretamente ligada ao dano tecidual, provavelmente relacionado a uma exacerbada resposta Th1 na placenta. / In this work, we used a murine model of recrudescence of malaria associated with pregnancy, consisting of BALB / c mice infected with Plasmodium berghei ANKAGFP to evaluate the immune response associated with the recrudescence of the disease. Observing the spleen cell populations by flow cytometry, an increase in the percentage of CD4+, CD19+, TCR <font face=\"Symbol\">g<font face=\"Symbol\">d+, GR1+ cells was observed in the infected animals, compared to the uninfected controls. No differences were observed in the percentage of placental leukocytes. Furthermore, our results showed that in the spleen, CD4+ and CD8+ cells were in a more active state in recrudescent females, while in the placenta, these animals exhibited an increase in CD4+ T cell activation. The ratio IgG2a/IgG1 in recrudescent vs non-recrudescent animals showed a 3-fold increase in the production of IgG2a indicating a Th1 immune response. qRT-PCR analysis, together with flow cytometry, showed that dendritic cells were the reservoirs of the parasite during the chronic stage of the disease, preceding the recrudescence. Together, these data suggest that recrudescence during pregnancy is directly linked to tissue damage, probably related to an exacerbated Th1 response in the placenta.

Neste trabalho, usamos um modelo murino de recrudescência da malária associada à gravidez, com camundongos BALB/c infectados por Plasmodium berghei ANKAGFP com o objetivo de avaliar a resposta imune associada ao recrudescimento da infecção. Observando as populações de células do baço por citometria de fluxo notou-se um aumento no percentual de células CD4+, CD19+, TCR <font face=\"Symbol\">g<font face=\"Symbol\">d+, GR1+ nos animais infectados, em relação aos controles não infectados. Não foram observadas diferenças no percentual de leucócitos placentários. Além disso, nossos resultados mostraram que no baço, linfócitos TCD4+ e TCD8+ estão mais ativados em fêmeas recrudescentes, enquanto que na placenta, estes animais apresentaram um aumento na ativação de células TCD4+. A relação IgG2a/IgG1 em animais ecrudescentes e não recrudescentes indicou um aumento de 3 vezes na produção de IgG2a que indica um padrão Th1 de resposta imune. A análise de qRT-PCR concomitantemente à citometria de fluxo evidenciou que células dendríticas são os reservatórios do parasita durante o estágio crônico da doença, que antecede o recrudescimento. Juntos, esses dados sugerem que a recrudescência durante a gestação está diretamente ligada ao dano tecidual, provavelmente relacionado a uma exacerbada resposta Th1 na placenta. / In this work, we used a murine model of recrudescence of malaria associated with pregnancy, consisting of BALB / c mice infected with Plasmodium berghei ANKAGFP to evaluate the immune response associated with the recrudescence of the disease. Observing the spleen cell populations by flow cytometry, an increase in the percentage of CD4+, CD19+, TCR <font face=\"Symbol\">g<font face=\"Symbol\">d+, GR1+ cells was observed in the infected animals, compared to the uninfected controls. No differences were observed in the percentage of placental leukocytes. Furthermore, our results showed that in the spleen, CD4+ and CD8+ cells were in a more active state in recrudescent females, while in the placenta, these animals exhibited an increase in CD4+ T cell activation. The ratio IgG2a/IgG1 in recrudescent vs non-recrudescent animals showed a 3-fold increase in the production of IgG2a indicating a Th1 immune response. qRT-PCR analysis, together with flow cytometry, showed that dendritic cells were the reservoirs of the parasite during the chronic stage of the disease, preceding the recrudescence. Together, these data suggest that recrudescence during pregnancy is directly linked to tissue damage, probably related to an exacerbated Th1 response in the placenta.