Erythrocyte Membrane Alterations Associated with the Attachment and Replication of Eperythrozoon suis: A Light and Electron Microscopic Study

Abstract

Abstract. Erythrocytes from pigs with experimental porcine eperythrozoonosis were examined using light microscopy and scanning and transmission electron microscopy. Three distinct forms of Eperythrozoon suis were attached to the plasma surface of erythrocyte membrane. Erythrocytes were initially parasitized by one or several immature forms. Immature forms enlarged and developed into juvenile and mature forms. The parasite replicated by budding of small immature forms from larger immature forms, juvenile forms, and mature forms. Small immature forms attached to adjacent membrane of the same erythrocyte or a nonparasitized erythrocyte. E. suis organisms were intimately associated with, but distinctly separated from erythrocyte membrane by a 30-nm electron lucent zone. Cell membrane in this area was denser than adjacent nonparasitized membrane. Early interaction between erythrocyte membrane and small immature forms resulted in no membrane deformation, but as this form enlarged, it later became embedded in a deep cup-like membrane invagination. As the immature form developed into the juvenile form a shallow, broad-based depression was observed in the membrane. A similar depression that covered a greater surface area was observed in the membrane parasitized by the mature form. The interaction between the parasitic forms and erythrocyte membrane resulted ultimately in severe membrane deformation. Parasite-membrane interactions may play an important role in the development of misdirected immune responses in experimental porcine eperythrozoonosis.Experimental porcine eperythrozoonosis is a unique system to study parasitic Materials and MethodsTen four-week-old crossbred pigs from the same litter were splenectomized and divided equally at random into control and experimental groups. Pigs were acclimated for two weeks following surgery. Control and expenmental pigs were housed in identical adjacent isolation rooms and were provided food and water ad libitum. Control pigs were bled before experimental pigs to prevent cross infection.Control and experimental group inocula were produced in a three-month-old crossbred splenectomized pig. Blood was obtained prior to inoculation with E. suis from the anterior vena cava, mixed with a glycerine-polyvinylpyrrolidone solution, stored in 4 ml aliquots at -70"C, and labeled as control group inoculum. This pig was then inoculated intramuscularly with 2 ml of E. suis-infected blood (> 90% parasitemia), and at the peak of parasitemia six days later blood was collected and processed as described previously for control inoculum. The number of parasitized erythrocytes was greater than 90% and this blood was labeled as expenmental inoculum. Control pigs were inoculated intramuscularly with 2 ml of E. suis-free blood and experimental pigs intramuscularly with 2 ml of E. suis-infected blood. All pigs were bled at the time of inoculation, at the peak of parasitemia one week later, I64

Insights into the Gene Expression Profile of Uncultivable Hemotrophic Mycoplasma suis during Acute Infection, Obtained Using Proteome Analysis

“…If so, phosphatidylcholine could be produced. The restricted lipid metabolism supports earlier findings that described the removal of host membrane parts by hemotrophic mycoplasmas, i.e., M. haemofelis and M. suis, to coat itself and evade the host immune system (52,87).…”

Two Genetic Clusters in Swine Hemoplasmas Revealed by Analyses of the 16S rRNA and RNase P RNA Genes

“…Currently only two hemoplasma species, Eperythrozoon parvum and Mycoplasma suis previously known as E. suis, are recognized in pigs (Sus scrofa domestica) [11,12,18]. Hemoplasmas parasitize the cell surface of swine erythrocyes, where it causes membrane deformation and damage [10,25]. Damaged erythrocytes are subsequently removed from the blood circulation, resulting in hemolytic anemia and icterus in pig [10].…”

Hemobartonella-like Parasites in Cynomolgus Monkeys (Macaca fascicularis)

“…19 The different forms may be developmental stages. 22 These organisms have few internal ultrastructural features but usually contain aggregates of electron-dense granules. Spherical forms sometimes contain internal membranous structures that are most likely indentations of their external membrane.…”

“…Hemobartonella species reside on the erythrocyte surface, but they usually are in deep indentations that can appear as vacuoles if cross sectioned.2L Eperythrozoon species also reside in deep indentations on the erythrocyte surface, but they also occur free in the plasma. 13,22 In this report, we describe the clinical pathologic, light microscopic, and electron microscopic features of Hemobartonella-like red blood cell parasites associated with anemic episodes in five female cynomolgus monkeys (Macaca fascicularis).…”