Monoclonal antibodies against Enterocytozoon bieneusi of human origin

Enterocytozoon bieneusi is clinically the most significant among the microsporidia infecting humans, causing chronic diarrhea, wasting, and cholangitis in individuals with human immunodeficiency virus/AIDS. The lack of immune reagents is largely due to the absence of methods for laboratory propagation of E. bieneusi. We recently described a procedure for the concentration and purification of spores from diarrheic stool of infected humans. Purified spores were used to immunize mice for production and screening of monoclonal antibodies (MAbs) against E. bieneusi. The eight immunoglobulin M MAbs generated and fully characterized did not cross-react with other human microsporidia or with other microorganisms normally present in stool. One of the MAbs, 2G4, reacted with E. bieneusi spores in stools from monkeys and humans, without background fluorescence, which makes it an ideal diagnostic reagent. It also recognizes intracellular stages of the parasite and will be suitable for determining tissue distribution of E. bieneusi in infected hosts. At least two immunodominant antigens of E. bieneusi of 33,000 and 35,000 Da exist, which were recognized by rabbit and mouse antisera. The availability of MAbs against E. bieneusi will simplify considerably the diagnosis of this infection in humans and will provide tools for epidemiologic investigations regarding the true prevalence of the infection in various human and mammalian populations and the environmental sources of infection.     

Concurrent de novo interstitial deletion of band 2p22 and reciprocal translocation (3;7)(p21;q22).

A child is described with a de novo interstitial deletion of band 2p22 and a reciprocal translocation (3;7)(p21;q22). The child has mild developmental delay, coloboma of the right eye, and Hirschsprung's disease. The clinical and cytogenetic findings are described.     

Sequence analysis of cDNAs for the human and bovine ATP synthase β subunit: mitochondrial DNA genes sustain seventeen times more mutations

We have cloned and sequenced human and bovine cDNAs for the subunit of the ATP synthase (ATP-synß), a nuclear DNA (nDNA) encoded oxidative phosphorylation (OXPHOS) gene. The two cDNAs were found to share 99% amino acid homology and 94% nucleotide homology. The evolutionary rate of ATPsynß was then compared with that of two mitochondrial DNA (mtDNA) ATP synthase genes (ATPase 6 and 8), seven other mtDNA OXPHOS genes, and a number of nuclear genes. The synonymous substitution rate for ATPsynß proved to be 1.9 × 10^–9 substitutions per site per year (substitutions × site^–1 × year^–1) (SSY). This is less than 1/2 that of the average nDNA gene, 1/12 the rate of ATPase 6 and 8, and 1/17 the rate of the average mtDNA gene. The synonymous and replacement substitution rates were used to calculate a new parameter, the selective constraint ratio. This revealed that even the most variable mtDNA protein was more constrained than the average nDNA protein. Thus, the high substitution mutation rate and strong selective constraints of mammalian mtDNA proteins suggest that mtDNA mutations may result in a disproportionately large number of human hereditary diseases of OXPHOS.     

Receptor-binding function of type 1 pili effects bladder colonization by a clinical isolate of Escherichia coli.

The role of type 1 pili in promoting bladder colonization was examined by constructing two mutant strains of a clinical Escherichia coli isolate. One mutant was isogenic to the parental strain save for a lesion in a gene required for pilus receptor binding; the other mutant was isogenic save for a lesion in the gene encoding the pilus structural subunit. Using mixed infections of the parental and mutant strains in an ascending rat cystitis model, we found that type 1-piliated mutants that lacked the receptor-binding function were as ineffective in bladder colonization as were mutants lacking the entire organelle.     

Apoptosis prevention as a mechanism of immune evasion

When cells are infected with viruses, they may trigger their apoptosis programs. In unicellular organisms, this may have protected cell populations by limiting viral replication from infected cells. Multicellular organisms can also trigger the apoptosis program after viral infection. In response, viruses have evolved a wide variety of inhibitors of apoptosis. In higher organisms, the outcome of viral infections is largely determined by the immune system. Since apoptosis is intimately linked to the function and regulation of the immune system, the ability of viruses to inhibit apoptosis could profoundly alter the immune response. Viral antiapoptotic proteins could protect infected cells from apoptosis induced by cytotoxic lymphocytes, alter antigen cross-presentation and the priming of the immune response, or modulate the expression of danger signals from sites of infection. The virus/host interaction is likely to provide useful lessons regarding the workings of the mammalian immune system.     

Identification of a gene from Xp21 with similarity to the tctex-1 gene of the murine t complex

Long range physical mapping within the p21 region of the X chromosomeIdentified a CpG rich Island approximately 180 kb centromericto the chronic granulomatous disease (CGD) locus. The segmentsadjacent to the CpG Island hybridized to discrete bands In DNAsof several species and when used to screen retinal cDNA librariesled to the Identification of cDNAs that detected a mRNA of 2.1kb in many tissues. Molecular characterization of correspondinggenomic clones of this novel human gene confirmed the originof the cDNA clones and Indicated a genomic structure with fiveexons spanning a total of 9 kb. The complete cDNA sequence revealedthat this gene contained a putative open reading frame of 116amino acids with a 3' untranslated region of 1.74 kb. The aminoacid sequence shows a high degree of similarity to the predictedproduct of the tctex-1 gene of the mouse t complex. As linkagestudies and patients with deletions have Implicated the Xp21region as containing the retInltls plgmentosa defect (RP3),the gene was assessed as a candidate disease gene In RP3 families.A single base pair polymorphism was Identified within the codingregion but no disease associated changes were found by singlestrand conformational polymorphism and sequencing analysis ofamplified exons of 20 RP patients. Analysis of a dinucleotiderepeat polymorphism within this gene In families affected withRP3 suggested refinement of the RP3 region.     

The Immune Reactivity Role of HCV-Induced Liver Infiltrating Lymphocytes in Hepatocellular Damage

Liver infiltrating lymphocytes (LIL) were isolated from HCV-positive (+) and HCV-negative (–) end-stage livers. Phenotypic analysis and functional studies using proliferative and lymphocytotoxic assays were performed with the isolated LIL. Two CD3+ lymphocyte populations were found in LIL using FITC anti-CD3 monoclonal antibodies (mAb). One was a bright fluorescence intensity population (as in PBL), and the other dim. We calculated the number of FITC-anti-CD3 mAbs bound per lymphocyte on PBL and LIL and found 80,040 ± 4628 and 39,615 ± 3932, respectively. Therefore, HCV+ and HCV– patient PBL contained approximately twice the number of CD3 molecules per cell than patient CD3+ LIL. LIL also contained approximately a threefold higher concentration of TCR+, CD4–CD8–, and CD56,16 (NK) cells than the patient PBL. Thus, a major subset of LIL is phenotypically similar to mouse NK1.1+ intermediate T cells. LIL freshly isolated from HCV+ livers exhibited weak CTL activity against EBV- or Con A-transformed lymphoblast targets infected with vaccinia–HCV recombinant virus (rHCV) or primary hepatocyte cultured cells. However, after in vitro coculture of LIL with rHCV, these cells developed a strong cytotoxicity for the above targets. In contrast, LIL from HCV– livers were not cytotoxic against the same targets. Histochemical studies (in situ) demonstrated that these hepatocytes express CD95, and stains demonstrated apoptosis. The HCV+ hepatocytes also express class I MHC molecules and ICAM-1. The addition of mAb specific for these adhesion molecules inhibited CML activity. Short-term cultured hepatocytes (targets) from HCV+ and HCV– patients produced low levels of cytokines IL-1, IL-2, IL-6, TNF, and IFN- but a high level of IL-8. It is speculated that LIL expressing reduced numbers of CD3 molecules may even function as immune regulators as proposed for intermediate T cells in mice.     

Tissue engineering of arteries by directed remodeling of intact arterial segments

Traditional approaches to generating tissue-engineered arteries in vitro rely on expansion of cells in culture to seed appropriate scaffolds. In most envisioned applications, small autologous blood vessels would be harvested and used as a source for these cells. We propose that small autologous arteries, not the cells derived from them, may be an attractive starting point for engineered arteries. This approach capitalizes on the ability of intact arteries to grow and remodel in response to chronic changes in their mechanical environment. Carotid arteries from juvenile (approximately 30-kg) pigs were stretched longitudinally in an ex vivo perfusion system over 9 days. This resulted in a 40% increase in artery length at physiological longitudinal stress and a 20 +/- 3% increase when unstressed. Control arteries were perfused for 9 days ex vivo at their physiological loaded length. Control and elongated arteries displayed native appearance (macroscopic and histological), excellent viability (cellularity and mitochondrial activity), normal vasoactivity, and similar mechanical properties (ultimate stress and ultimate strain) as compared with freshly harvested arteries. Growth, as opposed to just redistribution of existing mass, contributed to elongation as evidenced by an increase in artery weight. Results on elongation of arteries from neonatal and adolescent pigs are also presented and discussed.