Clinical and serological studies were carried out on 114 patients admitted to hospital in Havana, Cuba with Dengue Haemorrhagic Fever and Dengue Shock Syndrome (DHF/DSS). Serological confirmation of dengue was obtained in 90% of cases, with 5% of cases primary and 95% secondary. Fever, haemorrhagic manifestations, vomiting and headache were the most frequent signs and symptoms. Among haemorrhagic manifestations, petechiae and vaginal bleeding were reported in a larger number of patients. 21 patients presented shock and, of these, 20 were secondary infections. The disease appeared more frequently in white persons and in women. The aetiopathogenicity of the syndromes is discussed. 95% of the cases could be explained on the basis of the secondary infection hypothesis.

Selected cellular immune parameters were studied in 20 patients with sickle cell anaemia (SCA). A moderate absolute lymphocytes was observed in SCA patients compared with the control group. There was no significant difference between patients and controls in the mean E-rosette percentage and absolute number. PHA transformation was decreased in 50% of SCA patients, and some of them showed cutaneous anergy. It was suggested that impaired cell-mediated immunity is another factor to be included among defective SCA host-defense mechanism.

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Many marine bacteria demonstrate antibiotic activity against organisms of terrestrial origin. Low molecular weight antibiotics have been extracted and, in some cases, purified, but few attempts have been made to isolate high molecular weight antibiotics produced by marine bacteria. In the study reported here, a high molecular weight antibiotic was extracted from whole cells ofAlteromonas strain P18 (NCMB 1890) grown on 2216E medium. Purification included ammonium sulfate precipitation, ultracentrifugation, chromatography on DEAE cellulose, and gel filtration on Ultrogel. A rapid method for measuring specific activity of the antibiotic was developed.

SUMMARYIn the present study we describe the expression and functional activity of the a 4 b 1 heterodimer molecule on human natural killer (NK) cells. Flow cytometric analyses showed that fresh and activated NK cells expressed high levels of very late activation antigen-4 (VLA-4) molecules. These cells bound to ®bronectin (FN) and to its 38 000-MW proteolytic fragment through the VLA-4 integrin that was blocked with HP2/1 anti-a 4 monoclonal antibodies (mAbs) and with the FN peptide fragment CS1. No inhibitory effects were observed in the presence of anti-a 5 mAb, FN peptide fragment CS2 or other irrelevant mAb. Fresh NK cells were unable to aggregate, despite their expression of VLA-4, and only activated (cultured and lymphocyte-activated killer cells) NK cells showed homotypic aggregation with HP1/7 and HP2/4 anti-a 4 mAb related to cellular activation. These results underline new evidence of how NK cells in different states of activation maintain different constitutive levels of a 4 b 1 integrin activity, and highlight the possibility of a different functional regulation by the cells bearing VLA-4, in the expression of these epitopes and their ability to interact with their ligands.

A new bacteriocin produced by Aerococcus viridans was purified. Bacteria grown on liquid medium synthesized a bacteriocin, viridicin, which can be extracted from the cells by treatment with 0.86 M NaCl solution. Viridicin production was not induced by ultraviolet irradiation or by treatment with mitomycin C. The bacteriocin was purified by ultrafiltration, gel filtration, and preparative polyacrylamide disc gel electrophoresis. The molecular weight was between 100,000 and 120,000. The purified viridicin was homogeneous on polyacrylamide gel electrophoresis. The viridicin was composed of protein, carbohydrate, and lipid.Bacteriocins are high-molecular-weight bactericidal substances which are synthesized by many bacteria. The specificity of their action and their nature distinguish them from most of the classical antibiotics. It has been well established over the years that various strains of most species of bacteria produce these inhibitory substances (8, 14, 22, 23).Intensive work has been done on the bacteriocins of gram-negative bacteria, the best studied of which are the colicins (8,19,20).A recent review reported the physiochemical properties of some gram-positive bacterial bacteriocins (23).The bacteriocins produced by the gram-positive species are less well known than those of gram-negative species, and many concepts drawn from studies on colicins are not consistent with results obtained with the gram-positive organisms.Recently, we showed that the gram-positive bacterium Aerococcus viridans synthesizes a bacteriocin that we have called viridicin (1).A crude preparation of this macromolecule was not inactived by heating for 1 hour at 50°C and was sensitive to the action of protease, lipase, and catalase. Bacteriocin activity was not suppressed by trypsin, chymotrypsin, lysozyme, a-amylase, phospholipase C, lipase, f-glucuronidase, deoxyribonuclease, and ribonuclease. Growth of a large number of gram-negative and gram-positive bacteria was inhibited by viridicin.MATERIALS AND METHODS Microorganisms. The viridicin-producing strain A. viridans was isolated at

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