Cytochrome b5 and a recombinant protein containing the cytochrome b5 hydrophobic domain spontaneously associate with the plasma membranes of cells.

Both cytochrome b5, isolated from rabbit liver microsomes, and LacZ:HP, a recombinant protein consisting of enzymatically active Escherichia coli beta-galactosidase coupled to the C-terminal membrane-anchoring hydrophobic domain of cytochrome b5, were shown to spontaneously associate with the plasma membranes of erythrocytes and 3T3 cells. Association was promoted by low pH values, but proceeded satisfactorily over several hours at physiological pH and temperature. About 150,000 cytochrome b5 molecules or 100,000 LacZ:HP molecules could be associated per erythrocyte. These proteins were not removed from the membrane by extensive washing, even at high ionic strength. After incubation with fluorescently labeled cytochrome b5 or LacZ:HP, cells displayed fluorescent membranes. The lateral mobility of fluorescently labeled cytochrome b5 and LacZ:HP was measured by photo-bleaching techniques. In the plasma membrane of erythrocytes and 3T3 cells, the apparent lateral diffusion coefficient D ranged from 1.0.10(-9) to 8.10(-9) cm2 s-1 with a mobile fraction M between 0.4 and 0.6. The lateral mobility of these proteins closely resembled that reported for lipid-anchored proteins and was much higher than that reported for Band 3, an erythrocyte membrane-spanning protein with a large cytoplasmic domain. These results suggest that the hydrophobic domain of cytochrome b5 could be employed as a universal, laterally mobile membrane anchor to associate a variety of diagnostically and therapeutically useful recombinant proteins with cells.

Elevated relapse rates in pediatric compared to adult MS persist for at least 6 years.

OBJECTIVE: To compare relapse rates in pediatric-onset multiple sclerosis (POMS) and adult-onset multiple sclerosis (AOMS) over the first 6-years of disease. METHODS: Patients with relapsing-remitting disease onset were identified from the Partners Pediatric MS Center, Massachusetts General Hospital and Partners MS Center, Brigham and Women's Hospital. 84 POMS and 258 AOMS patients were included. Annualized relapse rates (ARR) for each individual year from year 1 to year 6, after first attack were compared using Poisson regression, as was expanded disability status scale (EDSS) score at the visit closest to each year interval. RESULTS: ARR was significantly higher in POMS compared to AOMS at individual years (except year 4), and was not significantly affected by adjustment for gender, race and proportion of time on treatment. Despite a 2.30 times higher relapse rate over 6-years, EDSS between groups did not differ. ARR in years 1-5 did not impact year 5 disability measured by EDSS in POMS. CONCLUSIONS: Our findings demonstrate that higher ARR in POMS relative to AOMS is sustained over 6-years, suggesting a more inflammatory nature and potential disconnect between relapses and disability measured by EDSS early in POMS. This data may be useful when designing clinical trials for POMS.

Entry of Bartonella bacilliformis into erythrocytes.

Bartonella bacilliformis, which causes the human diseases Oroya fever and verruga peruana, binds to human erythrocytes in vitro and produces substantial and long-lasting deformations in erythrocyte membranes, including cone-shaped depressions, trenches, and deep invaginations. The deforming force is probably provided by the polar flagella of these highly motile bacteria. Deep invaginations containing bacteria are commonly seen, and membrane fusion at the necks of the invaginations leads to the formation of intracellular vacuoles containing bacteria. Fluorescent compounds present externally render the vacuoles fluorescent and, occasionally, lightly fluorescent cells are seen, suggesting that the vacuoles sometimes rupture to admit the bacteria to the cytoplasm. Vacuoles present in fluorescent erythrocytes prepared by preloading the erythrocytes with fluorescent compounds are seen as dark areas from which the fluorescent marker is excluded. Entry of the bacteria appears to be the result of a process of forced endocytosis.

New use of BCG for recombinant vaccines.

BCG, a live attenuated tubercle bacillus, is the most widely used vaccine in the world and is also a useful vaccine vehicle for delivering protective antigens of multiple pathogens. Extrachromosomal and integrative expression vectors carrying the regulatory sequences for major BCG heat-shock proteins have been developed to allow expression of foreign antigens in BCG. These recombinant BCG strains can elicit long-lasting humoral and cellular immune responses to foreign antigens in mice.