Robert B. Fraser

Carboxypeptidase A5 identifies a novel mast cell lineage in the zebrafish providing new insight into mast cell fate determination

Mast cells (MCs) play critical roles in allergy and inflammation, yet their development remains controversial due to limitations posed by traditional animal models. The zebrafish provides a highly efficient system for studying vertebrate hematopoiesis. We have identified zebrafish MCs in the gill and intestine, which resemble their mammalian counterparts both structurally and functionally. Carboxypeptidase A5 (cpa5), a MC-specific enzyme, is expressed in zebrafish blood cells beginning at 24 hours post fertilization (hpf). At 28 hpf, colocalization is observed with pu.1, mpo, l-plastin, and lysozyme C, but not fms or cepbalpha, identifying these early MCs as a distinct myeloid population arising from a common granulocyte/monocyte progenitor. Morpholino knock-down studies demonstrate that transcription factors gata-2 and pu.1, but not gata-1 or fog-1, are necessary for early MC development. These studies validate the zebrafish as an in vivo tool for studying MC ontogeny and function with future capacity for modeling human MC diseases.

Bilateral adrenal EBV-associated smooth muscle tumors in a child with a natural killer cell deficiency.

EBV-associated smooth muscle tumors are found in immunocompromised patients, most commonly HIV/AIDS. We present a 12-year-old girl with the first documented case of EBV-related smooth muscle tumors in the presence of a rare classic NK cell deficiency. This sheds light on the role of NK cells in controlling EBV-related smooth muscle tumors.

CD4+CD25+Foxp3+ Regulatory T Cells Promote Th17 Responses and Genital Tract Inflammation upon Intracellular Chlamydia muridarum Infection

The functional role of CD4+CD25+Foxp3+ regulatory T cells (Tregs) in host responses to intracellular bacterial infection was investigated in an in vitro coculturing system and a murine model of Chlamydia muridarum genital tract infection. Remarkably, C. muridarum infection subverted the immune suppressive role of CD4+CD25+Foxp3+ Tregs; instead of hampering immune responses, Tregs not only promoted Th17 differentiation from conventional CD4+ T cells but also themselves converted into proinflammatory Th17 cells in both in vitro and in vivo settings. Anti-CD25 mAb PC61 treatment to deplete ∼50% of pre-existing Tregs prior to C. muridarum genital tract infection markedly reduced the frequency and the total number of Th17 but not Th1 CD4+ cells at both immune induction and memory phases. Most importantly, Treg-depleted mice displayed significantly attenuated inflammation, neutrophil infiltration, and reduced severity of oviduct pathology upon C. muridarum genital infection. To our knowledge, this is the first report demonstrating that the level of pre-existing CD4+CD25+Foxp3+ Tregs in Chlamydia-infected hosts has a major impact on the development Chlamydia-associated diseases.

Eosinophilic/T-cell chorionic vasculitis.

nChorionic vasculitis is the hallmark of a fetal response in chorioamnionitis. There are five highly characteristic findings: (1) leukocyte migration is not concentric but rather radiates toward the infected amniotic fluid; (2) the infiltrate is primarily neutrophils; (3) multiple chorionic vessels, first veins and then arteries, are usually involved; (4) the infiltrate never extends into the vasculature of stem villi; and (5) it is rare in the absence of chorioamnionitis (or its precursors). Here we describe a new form of chorionic vasculitis characterized by an infiltrate composed primarily of eosinophils and CD3+ T lymphocytes that very focally involves a single chorionic vessel (artery or vein), that radiates away from the amniotic fluid (i.e., toward the intervillous spaces), and that may extend into the stem villous vasculature; this lesion occurs in the absence of any evidence of chorioamnionitis. During the past 7+ years, using accepted placental review criteria, we have examined 7104 placentas and identified 14 cases of eosinophilic/T-cell chorionic vasculitis (or related lesions). Although the frequency of diagnosis in the placentas examined was 0.197%, its true incidence cannot be estimated because of its very focal nature and the limited nature of placental disk sampling. Its etiology and significance are unknown, but it may represent a focal immune-mediated vasculitis.n

Cutaneous ciliated cyst of the abdominal wall: a case report with a review of the literature and discussion of pathogenesis.

A cutaneous ciliated cyst is a rare lesion typically found on the lower extremity of young girls shortly after puberty. Here, we report a case involving a previously unreported site (i.e., abdominal wall) in a 14-year-old girl. We also describe immunohistochemical and ultrastructural findings, review and analyze the world literature, and offer insights as to the pathogenesis of this lesion.

Liposome encapsulation of a soluble recombinant fragment of the respiratory syncytial virus (RSV) G protein enhances immune protection and reduces lung eosinophilia associated with virus challenge

Respiratory syncytial virus (RSV) is a leading cause of bronchiolitis and pneumonia in young children and infants. Previous animal studies have shown that immunizing intramuscularly or intraperitoneally with the RSV G protein has elicited protective as well as harmful immune responses upon RSV challenge. In an RSV immunization strategy designed to target the respiratory tract directly (the site of RSV replication), we immunized BALB/c mice intranasally with a liposome-encapsulated, prokaryotically expressed thioredoxin fusion protein consisting of amino acids 128-229 of the RSV G protein (Trx-G(128-229)). Upon intranasal challenge with RSV, a 100 to 500-fold reduction in lung RSV replication was observed in mice immunized with liposome-encapsulated Trx-G(128-229) compared to a sham-immunized control group. Analysis of bronchoalveolar lavage fluids revealed an influx of eosinophils (18% of total cells) in mice immunized with Trx-G(128-229) alone. Such eosinophilic infiltration was diminished (to 4.5% of total cells), however, in mice immunized with liposome-encapsulated Trx-G(128-229). Histological analysis of lung tissue revealed an accumulation of cells around the bronchioles and vessels in mice immunized with Trx-G(128-229) alone followed by RSV challenge which was not increased further in mice immunized with liposome-encapsulated Trx-G(128-229). These results show that intranasal immunization of BALB/c mice with Trx-G(128-229), when encapsulated in liposomes, can reduce the level of RSV replication in the lung as well as specifically reduce the degree of eosinophilic infiltration compared to mice immunized with Trx-G(128-229) alone. This demonstrates the potential of liposomes and particular recombinant fragments of the RSV G protein as an effective combination in RSV vaccine studies.

Nodular fasciitis in the parotid region of a child

Nodular fasciitis is a common pathologic entity in the limbs of adults but rare in the head and neck of children. It is defined by the World Health Organization as a benign and probably reactive fibroblastic growth extending as a solitary nodule from superficial fascia into subcutaneous tissue. Treatment is local excision, and recurrence is rare.

Voriconazole treatment of presumptive disseminated Aspergillus infection in a child with acute leukemia.

Invasive fungal infection continues to pose a significant threat to immunocompromised patients. The authors describe a pediatric patient receiving chemotherapy for acute undifferentiated leukemia who developed presumptive Aspergillus species infection disseminated to lung, liver, spleen, and bone. The authors report the successful treatment of this infection with the addition of voriconazole, a triazole antimycotic, to treatment with amphotericin and surgical debridement, in the setting of ongoing intensive chemotherapy.

Parental views on tissue banking in pediatric oncology patients.

Research using banked tissue is key to advancing risk‐stratification and treatment of children with cancer. Knowledge of parental attitudes to ethical issues arising in tissue banking is very limited but essential in obtaining respectful consent.

MONOAMNIOTIC TWINS DELIVERED LIVEBORN WITH A FORKED UMBILICAL CORD

Monoamniotic twins are rare and are associated with high intrauterine mortality rates. This case appears to represent the first report of liveborn monoamniotic monochorionic twins delivered with a bifurcated umbilical cord. Pathological and angiographic studies of the placenta demonstrated a marginally inserted two-vessel umbilical cord that bifurcated at 8.4 cm from the disk into three-vessel umbilical cords supplying each twin. This probably represents the last opportunity for cleavage of the embryo prior to the formation of conjoined twins. A review of eight prior reports of monoamniotic twins with a single, bifurcating umbilical cord is provided.