Prevalence of antibodies to the repeat epitope of the circumsporozoite protein of Plasmodium vivax in San Luis Potosi, Mexico

The prevalence of antibodies against the repeat epitope of the circumsporozoite protein (cs) of the standard (PV210) and variant (PVK247) strain of Plasmodium vivax was determined by ELISA in 1170 sera from individual residents of seven localities of the Region Huasteca of San Luis Potosi, Mexico. The capture antigens were the synthetic peptides DDAAD and (ANGAGNQPG)4 that correspond to the repeats of the PV210 and PVK247 cs proteins, respectively. Of the analyzed serum samples, 34.1 percent (400/1170) were positive with one or both of these antigens. Of the sera, 18.2 percent (214/1170) reacted with the DDAADF peptide and 6.6 percent (78/1170) were positive with the variant synthetic peptide. Additionally, 9.2 percent (108/1170) of the samples reacted with both peptides. A sample of 10 percent of positive sera for the variant cs repeat (18/78) was tested with the cs repeat peptide of P. malariae/P. brasilianum (NAAG); almost all of them (16/18, 89 percent) being positive. These results confirm that the transmission of the variant strain of P. vivax is a common Phenomenon in endemic regions in Latin America, as well as in other tropical regions of the world. These findings may have implications for the development of a P. vivax vaccine since that based on the standard cs repeat only would not be universally protective

A study on the pathogenesis of human cerebral malaria and cerebral babesiosis

Cerebral complications are important, but poorly understood pathological features of infections caused by some species of Plasmodium and Babesia. Patients dying from P. falciparum were classified as cerebral or non-cerebral cases according to the cerebral malaria coma scale. Light microscopy revealed that cerebral microvessels of cerebral malaria patients were field with a mixture of parazited and unparazited erythrocytes, with 94% of the vessels showing parasitized red blood cell (PRBC) sequestration. Some degree of PRBC sequestration was also found in non-cerebral malaria patients, but the percentage of microvessls with sequestered PRBC was only 13% Electron microscopy demonstrated knobs on the membrane of PRBC that formed focal junctions with the capillary endothelium. A number of host cell molecules such as CD36, thrombospondim (TSP) and intracellular adhesion molecule I (ICAM-1) may function as endothelial cell surfacereports for P. falciparum-infected erythrocytes. Affinity labeling of CD36 and TSP to the PRBC surface showed these molecules specifically bind to the knobs. Babesia bovis infected erythrocytes procedure projections of the erythrocyte membrane that are similar to knobs. When brain tissue from B. bovis-infected cattle was examined, cerebral capillaries were packed with PRBC. Infected erythrocytes formed focal attachments with cerebral endothelial cells at the site of these knob-like projections. These findings indicate that cerebral pathology caused by B. bovis is similar to human cerebral malaria. A search for cytoadherence proteins in the endothelial cells may lead to a better understanding of the pathogenisis of cerebral babesiosis