In vitro replicas of bone marrow can potentially provide a continuous source of blood cells for transplantation and serve as a laboratory model to examine human immune system dysfunctions and drug toxicology. Here we report the development of an in vitro artificial bone marrow based on a 3D scaffold with inverted colloidal crystal (ICC) geometry mimicking the structural topology of actual bone marrow matrix. To facilitate adhesion of cells, scaffolds were coated with a layer of transparent nanocomposite. After seeding with hematopoietic stem cells (HSCs), ICC scaffolds were capable of supporting expansion of CD34+ HSCs with B-lymphocyte differentiation. Three-dimensional organization was shown to be critical for production of B cells and antigen specific-antibodies. Functionality of bone marrow constructs was confirmed by implantation of matrices containing human CD34+ cells onto the backs of severe combined immunodeficiency (SCID) mice with subsequent generation of human immune cells.

Four pregnant Macaca nemestrina dams at 140-145 days of gestation received an intraamniotic inoculation of group B streptococci (GBS). All four premature infants were born by cesarean delivery, were bacteremic at birth, and showed symptoms of GBS sepsis similar to infected human infants with early-onset disease. Three infants did not receive antibiotics and died of GBS sepsis by 10 h of age despite mechanical ventilation and fluids for blood pressure support. Penicillin treatment of the fourth infant prolonged survival and decreased the requirement for supportive therapy. Quantitative cultures and histopathology were done on all four infants. Transmission electron microscopy of lung tissue demonstrated GBS within membrane-bound vacuoles of type I and II alveolar epithelium and interstitial fibroblasts. This model should be useful for studying the early steps in the pathogenesis of early-onset GBS infections. GBS may enter alveolar epithelial cells to transit this barrier and ultimately disseminate via the blood-stream.

Blood smear evaluation of two baboons (Papio cynocephalus) experiencing acute hemolytic crises following experimental stem cell transplantation revealed numerous intraerythrocytic organisms typical of the genus Babesia. Both animals had received whole-blood transfusions from two baboon donors, one of which was subsequently found to display rare trophozoites of Entopolypoides macaci. An investigation was then undertaken to determine the prevalence of hematozoa in baboons held in our primate colony and to determine the relationship, if any, between the involved species. Analysis of thick and thin blood films from 65 healthy baboons (23 originating from our breeding facility, 26 originating from an out-of-state breeding facility, and 16 imported from Africa) for hematozoa revealed rare E. macaciparasites in 31%, with respective prevalences of 39, 35, and 12%. Phylogenetic analysis of nuclear small-subunit rRNA gene sequences amplified from peripheral blood of a baboon chronically infected withE. macaci demonstrated this parasite to be most closely related to Babesia microti (97.9% sequence similarity); sera from infected animals did not react in indirect fluorescent-antibody tests with Babesia microti antigen, however, suggesting that they represent different species. These results support an emerging view that the genusEntopolypoides Mayer 1933 is synonymous with that of the genus Babesia Starcovici 1893 and that the morphological variation noted among intracellular forms is a function of alteration in host immune status. The presence of an underrecognized, but highly enzootic, Babesia sp. in baboons may result in substantial, unanticipated impact on research programs. The similarity of this parasite to the known human pathogen B. microti may also pose risks to humans undergoing xenotransplantation, mandating effective screening of donor animals.

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