Natalia Paciorkowski

Brugian infections in the peritoneal cavities of laboratory mice: kinetics of infection and cellular responses.

Standard, immunocompetent, inbred strains of mice are non-permissive for infection with the human filarial nematode, Brugia malayi or the closely related Brugia pahangi. This non-permissiveness allows one to address the mechanism(s) that might be used by mammalian hosts to eliminate large, multicellular, metazoan, extracellular invertebrate pathogens. We describe here the time course of intraperitoneal Brugian infections in naïve and primed +/+ mice from two commonly used, inbred laboratory strains (C57BL/6J and BALB/cByJ). We believe that this documentation of the course of infection in normal mice will serve as a reference for future studies using mice with gene-targeted immunological deficits or which have been pharmacologically or immunologically manipulated to manifest such deficits. Our data show that even though both strains of mice eliminate the parasite before the onset of patency, there are significant differences in the time course of infection and in the fractions of input larvae that can be recovered at any time after infection. In a secondary infection, the time course of elimination is accelerated. We examined the cells in the peritoneal cavity, the site of infection, by flow microfluorimetry using forward and side scatter properties and cell surface antigen expression using fluorescent antibodies. These studies reveal a complex cellular pattern, predominated by B lymphocytes, macrophages, and eosinophils. The most notable gross morphological findings at necropsy during the phase of elimination of the parasite are nodules of tissue containing larvae, which appear viable in some cases and undergoing various stages of disintegration in others. These nodules, which are histologically granulomas, are primarily composed of macrophages and eosinophils, with few if any lymphocytes. Transmission electron micrographs reveal that eosinophils can penetrate under the cuticles of the larvae and be seen in close approximation with internal structures. These granulomas may represent an important mechanism by which worms are eliminated.

Primed Peritoneal B Lymphocytes Are Sufficient To Transfer Protection against Brugia pahangi Infection in Mice

ABSTRACT Lymphatic filariasis is a tropical disease caused by the nematode parasites Wuchereria bancrofti and Brugia malayi. Whereas the protective potential of T lymphocytes in filarial infection is well documented, investigation of the role of B lymphocytes in antifilarial immunity has been neglected. In this communication, we examine the role of B lymphocytes in antifilarial immunity, using Brugia pahangi infections in the murine peritoneal cavity as a model. We find that B lymphocytes are required for clearance of primary and challenge infections with B. pahangi third-stage larvae (L3). We assessed the protective potential of peritoneal B lymphocytes by adoptive transfer experiments. Primed but not naïve peritoneal B cells from wild-type mice that had been immunized with B. pahangi L3 protected athymic recipients from challenge infection. We evaluated possible mechanisms by which B cells mediate protection. Comparisons of cytokine mRNA expression between B-lymphocyte-deficient and immunocompetent mice following B. pahangi infection suggest that B cells are required for the early production of Th2-type cytokines by peritoneal cells. In addition, B-cell-deficient mice demonstrate a defect in inflammatory cell recruitment to the peritoneal cavity following B. pahangi infection. The data demonstrate a critical role of B lymphocytes in antifilarial immunity in naïve mice and in the memory response in primed mice.

Cellular Immunity, but Not Gamma Interferon, Is Essential for Resolution of Babesia microti Infection in BALB/c Mice

ABSTRACT A new strain of Babesia microti (KR-1) was isolated from a Connecticut resident with babesiosis by hamster inoculation and adapted to C3H/HeJ and BALB/c mice. To examine the relative importance of humoral and cellular immunity for the control of B. microti infection, we compared the course of disease in wild-type BALB/c mice with that in BALB/c SCID mice, JHD-null (B-cell-deficient) mice, and T-cell receptor αβ (TCRβ−/−) or gamma interferon (IFN-γ) (IFN-γ−/−) knockout mice following inoculation with the KR-1-strain. SCID mice and TCRαβ knockouts sustained a severe but nonlethal parasitemia averaging 35 to 45% infected erythrocytes. IFN-γ-deficient mice developed a less severe parasitemia but were able to clear the infection. In contrast, in six of eight JHD-null mice, the levels of parasitemia were indistinguishable from those in the wild-type animals. These data indicate that cellular immunity is critical for the clearance of B. microti in BALB/c mice but that disease resolution can occur even in the absence of IFN-γ.

Ascorbic Acid Is a Requirement for the Morphogenesis of the Human Filarial Parasite Brugia malayi

The nematode parasites Wuchereria bancrofti, Brugia malayi, and B. timori cause a disease in humans known as lymphatic filariasis, which afflicts approximately 120 million people worldwide. The parasites enter the human host from the mosquito either as L3 or as infective larvae and subsequently differentiate through 2 molts. In this article, we show that B. malayi depends on an exogenous source of vitamin C to complete the L3 to L4 molt, a critical morphogenic step in its life cycle. Brugia malayi apparently belongs to a small group of living organisms that depend on an exogenous source of vitamin C. This group includes only primates (including man) and guinea pigs among mammals.

Survey of academic pediatric hospitalist programs in the US: organizational, administrative, and financial factors.

BACKGROUND Many pediatric academic centers have hospital medicine programs. Anecdotal data suggest that variability exists in program structure. OBJECTIVE To provide a description of the organizational, administrative, and financial structures of academic pediatric hospital medicine (PHM). METHODS This online survey focused on the organizational, administrative, and financial aspects of academic PHM programs, which were defined as hospitalist programs at US institutions associated with accredited pediatric residency program (n = 246) and identified using the Accreditation Council for Graduate Medical Education (ACGME) Fellowship and Residency Electronic Interactive Database. PHM directors and/or residency directors were targeted by both mail and the American Academy of Pediatrics Section on Hospital Medicine LISTSERV. RESULTS The overall response rate was 48.8% (120/246). 81.7% (98/120) of hospitals reported having an academic PHM program, and 9.1% (2/22) of hospitals without a program reported plans to start a program in the next 3 years. Over a quarter of programs provide coverage at multiple sites. Variability was identified in many program factors, including hospitalist workload and in-house coverage provided. Respondents reported planning increased in-house hospitalist coverage coinciding with the 2011 ACGME work-hour restrictions. Few programs reported having revenues greater than expenses (26% single site, 4% multiple site). CONCLUSIONS PHM programs exist in the majority of academic centers, and there appears to be variability in many program factors. This study provides the most comprehensive data on academic PHM programs and can be used for benchmarking as well as program development.

Acute but not chronic macrophage recruitment in filarial infections in mice is dependent on C‐C chemokine ligand 2

Macrophages play an important role in the formation of granulomas and the clearance of Brugia pahangi infections in mice. However, the factors responsible for the recruitment of these cells to the site of infection are not known. In this study we examined the role of the C‐C chemokine ligand 2 (CCL2; also known as macrophage chemotactic factor – MCP1) in macrophage recruitment in intraperitoneal infections with B. pahangi. We observed that CCL2 was expressed by peritoneal exudate cells and was present in the sera of wild‐type mice. Serum levels of CCL2 peaked twice during the immune response, once during the early, acute phase and again during the late, chronic phase. To further elucidate the role of this chemokine in the anti‐filarial immune response, we compared CCL2 deficient (CCL2−/–) mice to wild‐type mice. We observed that macrophage recruitment was impaired only during the acute phase in the former. While macrophage recruitment was unaffected during the chronic phase, increased accumulation of B and T lymphocytes was seen in these mice. We further report that larval clearance and the in vitro adhesion of PECs to larvae were unimpaired in these mice.