Comparisons of the topographic characteristics and electrical charge distributions among <i>Babesia‐</i>infected erythrocytes and extraerythrocytic merozoites using AFM

Terrón

et al. 2020

mSphere

Babesia is an apicomplexan parasite of significance that causes the disease known as babesiosis in domestic and wild animals and in humans worldwide. Babesia infects vertebrate hosts and reproduces asexually by a form of binary fission within erythrocytes/red blood cells (RBCs), yielding a complex pleomorphic population of intraerythrocytic parasites. Seven of them, clearly visible in human RBCs infected with Babesia divergens, are considered the main forms and named single, double, and quadruple trophozoites, paired and double paired pyriforms, tetrad or Maltese Cross, and multiparasite stage. However, these main intraerythrocytic forms coexist with RBCs infected with transient parasite combinations of unclear origin and development. In fact, little is understood about how Babesia builds this complex population during its asexual life cycle. By combining cryo-soft X-ray tomography and video microscopy, main and transitory parasites were characterized in a native whole cellular context and at nanometric resolution. The architecture and kinetics of the parasite population was observed in detail and provide additional data to the previous B. divergens asexual life cycle model that was built on light microscopy. Importantly, the process of multiplication by binary fission, involving budding, was visualized in live parasites for the first time, revealing that fundamental changes in cell shape and continuous rounds of multiplication occur as the parasites go through their asexual multiplication cycle. A four-dimensional asexual life cycle model was built highlighting the origin of several transient morphological forms that, surprisingly, intersperse in a chronological order between one main stage and the next in the cycle. IMPORTANCE Babesiosis is a disease caused by intraerythrocytic Babesia parasites, which possess many clinical features that are similar to those of malaria. This worldwide disease is increasing in frequency and geographical range and has a significant impact on human and animal health. Babesia divergens is one of the species responsible for human and cattle babesiosis causing death unless treated promptly. When B. divergens infects its vertebrate hosts, it reproduces asexually within red blood cells. During its asexual life cycle, B. divergens builds a population of numerous intraerythrocytic (IE) parasites of difficult interpretation. This complex population is largely unexplored, and we have therefore combined three- and four-dimensional imaging techniques to elucidate the origin, architecture, and kinetics of IE parasites. Unveiling the nature of these parasites has provided a vision of the B. divergens asexual cycle in unprecedented detail and is a key step to develop control strategies against babesiosis.

Section: Discussionsupporting

confidence: 73%

Four-Dimensional Characterization of the Babesia divergens Asexual Life Cycle, from the Trophozoite to the Multiparasite Stage

Conesa

Terrón

et al. 2020

mSphere

“…This time was also comparable to the time required for the paired-pyriforms when developed through a synchronized budding to tetrads (Table 1). Our results definitely indicated that multiparasite stages initially originated from a single trophozoite, confirming that the polyparasitism phenomenon is due to continuous rounds of multiplication (17,18) rather than multiple infections of the same RBC.…”

Section: The Paired-pyriform Dominates the Asexual Cycle Of B Divergenssupporting

confidence: 73%

Four-dimensional characterization of theBabesia divergensasexual life cycle: from the trophozoite to the multiparasite stage

Conesa

Terrón

et al. 2020

Preprint

Babesia is an apicomplexan parasite of significance that causes the disease known as babesiosis in domestic and wild animals and in humans worldwide. Babesia infects vertebrate hosts and reproduces asexually by a form of binary fission within erythrocytes/red blood cells (RBCs), yielding a complex pleomorphic population of intraerythrocytic parasites. Seven of them, clearly visible in human RBCs infected with Babesia divergens, are considered the main forms and named single, double and quadruple trophozoites, paired and double paired-pyriforms, tetrad or Maltese Cross, and multiparasite stage. However, these main intraerythrocytic forms coexist with RBCs infected with transient parasite combinations of unclear origin and development. In fact, little is understood about how Babesia builds this complex population during its asexual life cycle. By combining the emerging technique cryo soft X-ray tomography and video microscopy, main and transitory parasites were characterized in a native whole cellular context and at nanometric resolution. As a result, the architecture and kinetic of the parasite population has been elucidated. Importantly, the process of multiplication by binary fission, involving budding, was visualized in live parasites for the first time, revealing that fundamental changes in cell shape and continuous rounds of multiplication occur as the parasites go through their asexual multiplication cycle. Based on these observations, a four-dimensional (4D) asexual life cycle model has been designed highlighting the origin of the tetrad, double paired-pyriform and multiparasite stages and the transient morphological forms that, surprisingly, intersperse in a chronological order between one main stage and the next along the cycle.IMPORTANCEBabesiosis is a disease caused by intraerythrocytic Babesia parasites, which possess many clinical features that are similar to those of malaria. This worldwide disease, is increasing in frequency and geographical range, and has a significant impact on human and animal health. Babesia divergens is one of the species responsible for human and cattle babesiosis causing death unless treated promptly. When B. divergens infects its vertebrate hosts it reproduces asexually within red blood cells. During its asexual life cycle, B. divergens builds a population of numerous intraerythrocytic (IE) parasites of difficult interpretation. This complex population is largely unexplored, and we have therefore combined three and four dimensional (3D and 4D) imaging techniques to elucidate the origin, architecture, and kinetic of IE parasites. Unveil the nature of these parasites have provided a vision of the B. divergens asexual cycle in unprecedented detail and a key step to develop control strategies against babesiosis

“…Free merozoites were not observed to invade cells that were already parasitized. This phenomenon has been associated recently with a possible electrical mechanism of repulsion that could prevent free Babesia merozoites from interacting with already infected erythrocytes 20 . This fact also suggests that the polyparasitism observed in multiple parasites stages probably results from continuous cycles of division from an original invading parasite rather than by multiple infections of the same erythrocyte.…”

Section: Discussionmentioning

confidence: 97%

Kinetics of the invasion and egress processes of Babesia divergens, observed by time-lapse video microscopy

González

Luque

et al. 2018

Sci Rep

Based on confocal fluorescence and bright field video microscopy, we present detailed observations on the processes of invasion and egress of erythrocytes by the apicomplexan parasite Babesia divergens. Time-lapse images reveal numerous unexpected findings associated with the dynamics of B. divergens and its ability to manipulate the erythrocyte during both processes in its asexual cycle under in vitro conditions. Despite the speed at which these processes occur and the small size of the parasite, we capture infective merozoites moving vigorously and causing striking deformations in the erythrocyte's plasma membrane during an active invasion. We also observed intraerythrocytic dynamic stages as paired pyriforms, double paired pyriforms, tetrads, unattached pyriform sister cells and multiple parasite stages resulting in the release of large numbers of merozoites over a short period. Of considerable interest is that time-lapse images reveal a novel mechanism of egress used by B. divergens to exit the human erythrocyte. The release occurs when B. divergens parasites establish contacts with the plasma membrane of the erythrocyte from within, before exiting the cell. Visualization and analysis of the images enabled us to obtain useful information and broaden our knowledge of complex and crucial events involved with parasitisation of human erythrocytes by B. divergens.