Genotype comparison of Plasmodium vivax and Plasmodium falciparum clones from pregnant and non-pregnant populations in North-west Colombia

ABSTARCT: Placental malaria is the predominant pathology secondary to malaria in pregnancy, causing substantial maternal and infant morbidity and mortality in tropical areas. While it is clear that placental parasites are phenotypically different from those in the peripheral circulation, it is not known whether unique genotypes are associated specifically with placental infection or perhaps more generally with pregnancy. In this study, genetic analysis was performed on Plasmodium vivax and Plasmodium falciparum parasites isolated from peripheral and placental blood in pregnant women living in North-west Colombia, and compared with parasites causing acute malaria in non-pregnant populations. Methods: A total of 57 pregnant women at delivery with malaria infection confirmed by real-time PCR in peripheral or placental blood were included, as well as 50 pregnant women in antenatal care and 80 men or non-pregnant women with acute malaria confirmed by a positive thick smear for P. vivax or P. falciparum. Five molecular markers per species were genotyped by nested PCR and capillary electrophoresis. Genetic diversity and the fixation index FST per species and study group were calculated and compared. Results: Almost all infections at delivery were asymptomatic with significantly lower levels of infection compared with the groups with acute malaria. Expected heterozygosity for P. vivax molecular markers ranged from 0.765 to 0.928 and for P. falciparum markers ranged from 0.331 to 0.604. For P. vivax infections, the genetic diversity was similar amongst the four study groups and the fixation index from each pairwise comparison failed to show significant genetic differentiation. For P. falciparum, no genetic differentiation was observed between placental and peripheral parasites from the same woman at delivery, but the parasites isolated at delivery showed significant genetic differentiation compared with parasites isolated from subjects with acute malaria. Conclusions: In North-west Colombia, P. vivax parasites have high genetic diversity that is equivalent in pregnant and non-pregnant populations as well as in symptomatic and asymptomatic infections. For P. falciparum, the overall genetic diversity is lower, with specific genotypes associated with asymptomatic infections at delivery

Functional antibodies against VAR2CSA in nonpregnant populations from Colombia exposed to Plasmodium falciparum and Plasmodium vivax

RESUMEN: En el embarazo, se observa inmunidad dependiente de la paridad en respuesta a la infección placentaria con Plasmodium falciparum. Los anticuerpos reconocen el antígeno de superficie, VAR2CSA, expresado en glóbulos rojos infectados e inhiben la citoadherencia al tejido placentario. En la mayoría de los entornos de endemicidad del paludismo, los anticuerpos contra VAR2CSA se observan predominantemente en las mujeres multigravidias y con poca frecuencia en hombres, niños y mujeres nulligráficas. Sin embargo, en Colombia, se detectaron anticuerpos contra múltiples constructos de VAR2CSA entre hombres y niños con infección aguda por P. falciparum y Plasmodium vivax. La mayoría de los hombres y niños (> 60%) tenían altos niveles de IgG contra tres dominios recombinantes de VAR2CSA: DBL5ε, DBL3X e ID1-ID2. Sorprendentemente, estos anticuerpos se observaron sólo en mujeres embarazadas, hombres y niños expuestos a P. falciparum oa P. vivax. Además, los anticuerpos anti-VAR2CSA son de alta avidez e inhiben eficazmente la adherencia de glóbulos rojos infectados al condroitín sulfato A in vitro, lo que sugiere que son específicos y funcionales. Estos resultados inesperados sugieren que puede haber diferencias genotípicas o fenotípicas en los parásitos de esta región o en la respuesta del huésped a la infección por P. falciparum o P. vivax fuera del embarazo. Estos hallazgos pueden tener relevancia clínica significativa para la fisiopatología y el resultado de las infecciones de malaria en esta región.ABSTRACT: In pregnancy, parity-dependent immunity is observed in response to placental infection with Plasmodium falciparum. Antibodies recognize the surface antigen, VAR2CSA, expressed on infected red blood cells and inhibit cytoadherence to the placental tissue. In most settings of malaria endemicity, antibodies against VAR2CSA are predominantly observed in multigravid women and infrequently in men, children, and nulligravid women. However, in Colombia, we detected antibodies against multiple constructs of VAR2CSA among men and children with acute P. falciparum and Plasmodium vivax infection. The majority of men and children (>60%) had high levels of IgGs against three recombinant domains of VAR2CSA: DBL5ε, DBL3X, and ID1-ID2. Surprisingly, these antibodies were observed only in pregnant women, men, and children exposed either to P. falciparum or to P. vivax. Moreover, the anti-VAR2CSA antibodies are of high avidity and efficiently inhibit adherence of infected red blood cells to chondroitin sulfate A in vitro, suggesting that they are specific and functional. These unexpected results suggest that there may be genotypic or phenotypic differences in the parasites of this region or in the host response to either P. falciparum or P. vivax infection outside pregnancy. These findings may hold significant clinical relevance to the pathophysiology and outcome of malaria infections in this region

Regulation of Cdc18 and Cdt1 restricts S phase to once per cell cycle in fission yeast

In all eukaryotes, it is essential that cells maintain a strict control over S phase to ensure that DNA replication occurs once, and only once, per cell division cycle. To achieve this, cells must promote DNA replication during the G1 phase and then repress DNA replication during the G2 phase. In the fission yeast Schizosaccharomyces pombe, two proteins required for the initiation of DNA replication, Cdcl8 and Cdt1, may be important for this control over DNA replication. Cdcl8 and Cdt1 are both upregulated in G1 and have an essential function in initiation, and are then efficiently downregulated in G2. In this thesis, I have tested whether the downregulation of these initiation factors is important to repress DNA synthesis in G2. I have found that the accumulation of high levels of Cdcl8 are sufficient to induce origin firing in G2 cells and drive re-replication in the absence of mitosis. This re-replication is potentiated by the co-expression of Cdt1, which may be mediated by the stabilisation of Cdc18 on chromatin by Cdt1. Biochemical characterisation of these re-initiation events revealed that certain aspects of this re-replication are similar to those observed in wild type S phase cells, such as the requirement for the MCMs and the cyclin-dependent kinase Cdc2. However, these cells fail to undergo complete and efficient replication of the chromosomes suggesting that Cdc18 and Cdt1 can override the normal controls that block initiation, but this mechanism does not fully mimic initiation in a G1 cell. The findings presented in this thesis have identified and characterised multiple, overlapping mechanisms that downregulate Cdc18 and Cdt1 in G2. If these mechanisms are disrupted and Cdc18 and Cdt1 are allowed to accumulate in G2, replication competence can be re-established and cells re-replicate. Therefore, Cdc18 and Cdt1 form the core of the control which licenses chromosomes for replication

Regulation of Cdc18 and Cdt1 restricts S phase to once per cell cycle in the fission yeast Schizosaccharomyces pombe

SIGLEAvailable from British Library Document Supply Centre- DSC:DXN058856 / BLDSC - British Library Document Supply CentreGBUnited Kingdo