Cellular immune response of humans to the circumsporozoite protein of Plasmodium vivax

The cellular immune response to the circumsporozoite (CS) protein of plasmodium vivax of individuals from malaria-endemic areas of Brazil was studied. We examined the in vitro proliferative response of the peripheral blood mononuclear cells (PBMC) of 22 individuals when stimulated with a CS recombinant protein (rPvCS-2) and two other synthetic peptides based on the sequenceof the P. vivax CS protein. Seven of the individuals from malaria-endemic area displayed an antigen specific in vitro proliferative responseto the recombinant protein PvCS-2 and one out of 6, proliferative response to the peptide 308-320. In contrast, none of the individuals displayed a proliferative reponse when stimulated with the D/A peptide which represent some of the repeated units present in this CS protein. Our study, therefore, provides evidence for the presence, withinthe major surface antigen of P. vivax sporozoites, of epitopes capble to induce proliferation of human PBMC.

An outbreak of human Leishmania (Viannia) braziliensis infection

The occurence of acute cutaneous leishmaniasis among inhabitants of 10 farms within 10 Km of the hamlet of Corte de Pedra, Bahia, Brazil was studied prospectively from 1984-l989. A mean population of 1,056 inhabitants living in 146 houses were visited every 6 months and the number of sKin ulcers recorded. A leishmanin skin test survey was done people with suggestive skin scars or active disease in l984. The incidence of skin ulcers due to Leishmania (Viannia) brasiliensis (Vlb) reached 83/1,000 inhabitants but declined sharply in the subsequent 2 years. Retrospective data shows that leishamiasis is a sporadic endemic disease. Although the reasons for this epidemic are unclear some possible aetiological factors are discussed.

Are dead Triatoma infestans a competent vector of Trypanosoma cruzi?

After Triatoma infestans death, Trypanosoma cruzi survived several days, maintaining the ability to infect a vertebrate host. Dead bugs from an endemic area collected during an official spraying comapign showed mobile rectal tripanosomes up to 14 days after vector death. Two days after vector death2, 760 tripomastigotes were found alive in its rectal material. However, the number of mobile tripomastigotes decreased significantly from the 5th day after death. Laboratory proofs with third and fifth nymphal stage showed similar results. Living tripanosomes were found in their rectal material at 10 days in third stage and even at 30 days in fifth nymphal stage. The mean number of tripomastigotes had no changes up to 10 days in third nymphal stage and increased significantly from 1 to 10 days in the fifth stage. Conjuctival instillation as well as intraperitoneal innoculation to mice, of metacyclic forms from dead T. infestans produced infection in the vertebrate host. Present results show that human contact with dead vector highly probable in summer and living and infective T. cruzi are available for transmision in the vector.

The epidemiological significance of Chagas' disease in womem

Little is known about the risks associated with Trypanosoma cruzi infection in non-pregnant and pregnant women. From a limited number of studies it appears that in rural areas, parasite rates and rates of serological positivity are similar in both sexes. Abnormal ECG tracings are consistently more frequent in men suggesting that immunity to T. cruzi may be different in females. Complications arising from Chagas' disease in pregnancy are only infrequently reported. Evidence for increased risk of abortion or prematurity is inconclusive except in cases of congenital infection. Most cases of congenital Chagas' disease have been reported from non-endemic areas and there is a suggestion that parasitemic episodes during pregnancy may influence pregnancy outcome. Preliminary evidence indicates that chronic infection can result in in-utero sensitization via passively acquired maternal antibodies. The review concludes that maternal T. cruzi infection carries risks for the child and these warrant systematic research because of their public health significance.