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Biomedical subjects

M K Hostetter

Publications and source records attributed to M K Hostetter.

At least 19 recordsLinked to original sources
PubMed2000

C3 as substrate for adhesion of Streptococcus pneumoniae.

The ability of choline-binding protein A (CbpA) of Streptococcus pneumoniae to bind the third component of complement (C3) suggests possible interactions with opsonic C3 in the bloodstream or with C3 secreted by epithelial cells. The latter possibility was investigated by measuring C3 in supernatants of resting and cytokine-activated monolayers of type II pulmonary epithelial cells (A549 cells). Expression of C3 on the epithelial cell surface was confirmed by immunofluorescence. Epithelially produced C3 bound to CbpA, as determined by Western blot test. cbpa(-) mutants and lysates therefrom failed to bind C3, were completely deficient in adhesion to a matrix in which C3 was the sole substrate, and demonstrated a moderate yet significant decrease in adhesion to type II pulmonary epithelial cells. These results confirm the interaction of the pneumococcal protein CbpA and its substrate, C3, in 2 in vitro models of adhesion.

Bacterial Adhesion↗
PubMed2000

Novel purification scheme and functions for a C3-binding protein from Streptococcus pneumoniae.

To isolate microbial proteins capable of binding the third component of complement (C3), we coupled the free sulfhydryl group of methylamine-inactivated C3 to a thiolSepharose matrix. This simple technique facilitated the purification of the first C3-binding protein isolated from a bacterium (Streptococcus pneumoniae). Both metastable (native) and thioester-disrupted C3 were recognized by this protein; binding of C3 was noncovalent, independent of thioester conformation, and preferential for the C3 alpha-chain. Sequencing of amino-terminal and internal peptides from the C3-binding protein disclosed a proline-rich region spanning approximately 20 amino acids and a signal peptide that had not been previously reported. The gene was isolated from a library of genomic DNA from laboratory strain CP1200 by screening with a 1200 bp PCR product amplified from degenerate oligonucleotides encoding the amino terminal sequence and the internal proline-rich sequence. The open reading frame spanned 1692 bp; all peptide sequences were identified in the translated gene product, which also contained at least three choline-binding repeats at the carboxy-terminus. The gene was conserved, and the translated protein was functionally active in pneumococcal clinical isolates of serotypes 1, 3, 4, 14, and 19F. Serum from a patient recovering from acute pneumococcal infection contained IgG antibodies specific for this protein by immunoblot. Wide conservation among clinical isolates, saturable binding of C3, and the ability to stimulate the human immune response have not previously been reported for this choline-binding protein. A similar biochemical approach should enable the identification of other C3-binding proteins in microorganisms able to elude complement-mediated host defense.

Amino Acid Sequence↗
PubMed2000

A pneumococcal protein that elicits interleukin-8 from pulmonary epithelial cells.

To understand how neutrophils are recruited to the lung in pneumococcal pneumonia, the ability of pneumococcal components to elicit the chemokine interleukin (IL)-8 from monolayers of cultured human type II cells was assessed. Heat-killed clinical and laboratory strains of Streptococcus pneumoniae and secreted proteins from exponentially growing pneumococci elicited significant quantities of IL-8 from A549 cells. All strains that elicited IL-8 production secreted a protein ( approximately 90 kDa) that comigrated on SDS-PAGE with a C3-binding protein previously identified in S. pneumoniae. As little as 7 pmol of the purified 90-kDa protein readily elicited levels of IL-8 production equivalent to those obtained with 1 U of IL-1alpha. Supernatant proteins and heat-killed cells of an isogenic mutant that failed to produce the C3-binding protein elicited significantly less IL-8 than did supernatant proteins or heat-killed cells of the parent strain. These results implicate the C3-binding protein of S. pneumoniae in a novel pathway of pulmonary inflammation.

Bacterial Proteins↗
PubMed2000

RGD-mediated adhesion in fungal pathogens of humans, plants and insects.

Progress in the understanding of fungal adhesion has led to the identification of novel proteins recognizing the RGD tripeptide in matrix proteins and to the characterization of what appears to be an emerging subset of fungal adhesins that themselves contain an RGD sequence.

Amino Acid Sequence↗
PubMed1999

Integrin-like proteins in Candida spp. and other microorganisms.

The vertebrate integrins provide a paradigm for cell surface proteins involved in adhesion and morphogenesis. However, homologs of integrins have been found in more primitive organisms. This review will discuss the evidence for surface proteins in Candida albicans and Candida tropicalis that contain motifs reminiscent of integrins and will analyze the contributions of one of these proteins, Int1p, to adhesion, morphogenesis, and virulence. Other microorganisms thought to express integrin-like proteins will also be addressed.

Animals↗
PubMed1999

Effect of INT1 gene on Candida albicans murine intestinal colonization.

BACKGROUND: Increased intestinal colonization with Candida albicans is believed to be a major factor predisposing immunocompromised and postsurgical patients to systemic candidiasis, although the mechanisms facilitating C. albicans colonization remain unclear. Because previous studies have linked the C. albicans INT1 gene to filament formation, epithelial adherence, and mouse virulence, experiments were designed to evaluate the effect of INT1 on intestinal colonization. MATERIALS AND METHODS: Mice were orally inoculated with either the parent strain (CAF2, INT/INT1), an int1 heterozygote (CAG1, INT1/int1), an int1 homozygote (CAG3, int1/int1), or a reintegrant (CAG5, int1/int1 + INT1), and sacrificed 3 and 7 days later for quantitative analysis of cecal C. albicans. RESULTS: Following oral inoculation with 10(3) C. albicans, only small numbers of each strain were recovered from the cecal flora of normal mice. However, in mice pretreated with oral antibiotics, cecal colonization of each strain was increased (P < 0.01). In addition, cecal colonization was reduced for all int1 mutant strains compared with the parent strain (P < 0.05). By light microscopy, all four C. albicans strains were easily observed in the ileal lumen as both budding yeast and filamentous forms, although only occasional yeast forms appeared adherent to the intestinal epithelium. CONCLUSIONS: C. albicans readily colonized and replicated in the ceca of antibiotic-treated mice. The presence of two functional copies of INT1 appeared to facilitate C. albicans cecal colonization, suggesting that intestinal colonization may be another virulence factor associated with INT1 and that the gene product may be an attractive target to control C. albicans intestinal colonization.

Animals↗
PubMed1999

Systemic infection following intravenous inoculation of mice with Candida albicans int1 mutant strains.

The Candida albicans gene INT1 is associated with epithelial adhesion, hyphal formation, and virulence. C. albicans strains carrying two, one, or no functional INT1 alleles were used to assess the association between mortality and C. albicans persistence in the liver and kidney of intravenously inoculated mice. Mice were injected with 10(5) C. albicans CAF2 (parent strain, INT1/INT1), C. albicans CAG3 (homozygous disruptant, Int1/int1), or C. albicans CAG5 (heterozygous reintegrant, int1/int1 + INT1). Mortality was monitored and mice were sacrificed on Days 1, 7, 14, and 21 for quantitative analysis of kidney and liver microbes, with histologic analysis of these tissues as well. Mortality was highest for mice injected with the wild-type strain CAF2 (INT1/INT1) and lowest for mice injected with the homozygous disruptant CAG3 (int/int1). Yeast were readily cleared from the liver of all mice injected with any of the three C. albicans strains. Although the mutant strains CAG3 and CAG5 are defective for hyphal formation in vitro, there was histological evidence of abundant hyphal formation in the renal pelvis of mice injected with these strains. Compared to the wild-type strain, mutant strains were associated with reduced mortality but increased C. albicans persistence in the kidney. Thus, the absolute ability to form hyphae in the kidney did not appear to modulate either C. albicans-induced mortality or the course of progressive infection in the kidney. In addition, reduced virulence was paradoxically associated with increased, not decreased, persistence of C. albicans in the kidney.

Animals↗
PubMed1999

Infectious diseases in internationally adopted children: findings in children from China, Russia, and eastern Europe.

Conditions in many orphanages provide a fertile environment for infectious diseases uncommonly encountered in industrialized nations. Moreover, health care providers may be unfamiliar with the need to test for these conditions in internationally adopted children. Pediatric infectious disease specialists provide much-needed expertise for parents and providers alike.

Adolescent↗
PubMed1998

Linkage of adhesion, filamentous growth, and virulence in Candida albicans to a single gene, INT1.

Adhesion and the ability to form filaments are thought to contribute to the pathogenicity of Candida albicans, the leading cause of fungal disease in immunocompromised patients. Int1p is a C. albicans surface protein with limited similarity to vertebrate integrins. INT1 expression in Saccharomyces cerevisiae was sufficient to direct the adhesion of this normally nonadherent yeast to human epithelial cells. Furthermore, disruption of INT1 in C. albicans suppressed hyphal growth, adhesion to epithelial cells, and virulence in mice. Thus, INT1 links adhesion, filamentous growth, and pathogenicity in C. albicans and Int1p may be an attractive target for the development of antifungal therapies.

Animals↗
PubMed1997

Health of children adopted from the former Soviet Union and Eastern Europe. Comparison with preadoptive medical records.

CONTEXT: Children born in the countries of the former Soviet Union and Eastern Europe are now a main source of international adoptions in the United States, but often little information is available about these children prior to adoption. OBJECTIVE: To analyze the preadoptive medical reports of children adopted from Eastern Europe and the former Soviet Union and to compare these reports with their evaluations after arrival in the United States. DESIGN: Case series. SUBJECTS AND SETTING: A total of 56 children adopted from Eastern Europe and the former Soviet Union were evaluated in 2 international adoption clinics. Preadoptive medical records were available for 47 of these children. RESULTS: There were 43 (91%) of 47 medical reports available from the children's birth countries that included multiple unfamiliar neurologic diagnoses. Evaluations in the International Adoption Clinics frequently revealed growth delays (zscore < or = -1 for weight in 44% of children, height in 68%, and head circumference in 43%). Children had 1 month of linear growth lag for every 5 months in an orphanage (r=-0.48, P<.001). Developmental delays were also common (gross motor delays in 70% of children, fine motor in 82%, language in 59%, and social-emotional in 53%). While serious medical problems were found or corroborated in 11 (20%) of the 56 children evaluated in our clinics, neurologic diagnoses cited in preadoptive medical reports were not confirmed. CONCLUSIONS: Preadoptive medical records from these international adoptees included multiple diagnoses suggesting severe neurologic impairment. Although these diagnoses were not confirmed when the children were evaluated in the United States, substantial growth and developmental delays were identified.

Adoption↗
PubMed1996

An integrin-like protein in Candida albicans: implications for pathogenesis.

Candida albicans is the foremost fungal pathogen in neonates, diabetics and immunocompromised people. The discovery of integrin-like proteins in this yeast and the involvement of these proteins in adhesion, morphogenesis and signal transduction suggest important roles for primitive integrins in the pathogenesis of infectious diseases, and as paradigms for signaling and differentiation in vertebrate cells.

Amino Acid Sequence↗
PubMed1996

Evidence for a beta 1 integrin fibronectin receptor in Candida tropicalis.

The binding of Candida tropicalis to fibronectin (FN) was studied in order to characterize the FN receptor in this species. FN binding was saturable at a concentration of 1.8 x 10(-9) M and exhibited a Kd of 2.3 x 10(-9) M and a receptor density of 854 receptors per cell. Extracts of C. tropicalis cell membrane at dilutions of 1:100-1:1000 significantly inhibited the binding of 3H-labeled FN to C. tropicalis cells (P < .03). Purified FN, antibodies to the integrin alpha 5 beta 1 (FN receptor on human placenta), and antibodies specific for the integrin beta 1 subunit recognized a C. tropicalis membrane protein of 125 +/- 25 kDa on immunoblots. Immunoprecipitation of radiolabeled proteins from C. tropicalis with purified human FN yielded a protein of 105 +/- 15 kDa. Thus, C. tropicalis expresses a protein with antigenic and functional similarity to the vertebrate beta 1 integrin FN receptor.

Candida↗