1. The inclusion of formic and propionic acids in the form of Bio-Add to the food of hens made no difference to the pH of the intestinal tract, but resulted in higher concentrations of these acids in the contents of the crop and gizzard. 2. Organic acids in the crop contents were bactericidal for Salmonella serotype Enteritidis PT4 in vitro, and also caused sub-lethal damage because fewer cells were recovered on selective salmonella media (brilliant green phenol red agar) than on non-selective media (nutrient agar). 3. Inclusion of Bio-Add in the food at 12g/kg may reduce the number of lactic acid-producing bacteria in the crop, and hence the amount of naturally produced organic acids.

Foetal, adult seronegative, and cotton-top marmoset lymphocytes have been transformed into cell lines by EB virus from the malignant epithelial cells of two nasopharyngeal carcinomas. The nature of the cell lines was checked by karyotyping and by light and electron microscopy, and the presence of the EB virus genome was demonstrated by immunofluorescence tests. Immunofluorescence also showed the incidence of EB virus-producing cells in each line and this was checked by electron microscopy and the use of a lymphocyte transformation assay. Two foetal-derived lines did not produce virus spontaneously, could not be activated with various inducers, and were found by DNA reassociation kinetics to carry only small numbers of genome copies per cell. An adult-derived line produced virus, could be activated to produce more, and provided enough infectivity to transform marmoset cells. The resulting marmoset line made profuse transforming virus; it thus provides the first abundant source of NPC-derived infectious EB virus for comparative studies. The results are discussed in relation to the interactions with comparable target cells of EB virus from normal individuals and from patients with other diseases.

The purifiedMr 340,0M 0 glycoprotein component of Epstein-Barr (EB)-virus-induced membrane antigen complex incorporated into liposomes was shown to be a potent immunogen in mice. High-titer antisera were induced that (i) are specific for membrane antigen components without absorption, (ii) bind the antigens induced by three different EB virus isolates, and(iii) neutralize the ability of the virus to transform fetal cord blood lymphocytes in vitro. The development of this immunogenic form of purified antigen provides an important step towards a potential subunit vaccine against Epstein-Barr virus infection.It has been suggested in recent years that a vaccine capable of preventing Epstein-Barr (EB) virus infection in man might be able to reduce the incidence of EB. virus-associated disease in the vaccinated population (1, 2). When developed, such a vaccine might be tested initially for its protective effect against primary EB virus infection accompanied by infectious mononucleosis (3) and subsequently could be investigated for its capacity to modify the incidence of endemic Burkitt lymphoma in high-risk areas (4, 5); hopefully, in the longterm, it might be tested for possible efficacy in the much more difficult system of nasopharyngeal carcinoma (5, 6).There are substantial reasons for considering that any vaccine against EB virus for use in man should be based on polypeptide immunogens free of virus DNA (1, 2, 5), and several recent studies have sought to define those antigens of the virus envelope that engender virus-neutralizing antibodies and that, therefore, might provide the basis for a subunit vaccine (7-9). It is now clear that antibody to large viral glycoproteins expressed both on the viral envelope and as part ofthe membrane antigen (MA) complex on virus-producing lymphoid cell lines (7) can neutralize virus in the absence of complement (7-9).MA has been extensively studied, and general agreement exists that it comprises at least three glycoproteins, of Mrs 340,000,.270,000, and 85,000 conveniently designated gp340, gp270, and gp85, respectively (7, 10-16). Although small variations in molecular weight, relative abundance of the two largest glycoproteins, and distribution of antigenic determinants have been reported between MA expressed on different cell lines (7,10,12,(15)(16)(17)(18)(19)(20), both experimental antisera and monoclonal antibodies induced by the MA ofone EB virus isolate will neutralize other isolates of the virus (8, 9, 21).A simple and efficient procedure for the purification of the gp340 components of MA has been developed in this laboratory (22). Although the preparations obtained have considerable antigenicity, they are only weakly immunogenic as compared to enveloped EB virus particles when administered to experimental animals in Freund's adjuvant, and it would seem that the reduced immunogenicity may be ascribed to the influence ofdetergent solutions used in the presentation ofthe glycoprotein.The present communication reports evidence which demonstrates that removal of d...

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The size of Escherichia coli and Salmonella enteritidis PT4 cells was measured using both transmission electron micrographs and image analysis. Incubation in the presence of formic and propionic acids resulted in larger cells, possibly as a result of DNA inhibition, with no apparent damage to the cell membranes. Bacteria incubated with propionic acid were more resistant to shrinkage after fixation, possibly as a result of altered phospholipid and fatty acid composition.