Multiple cell wall blebs were observed on the surface of three strains of N. meningitidis taken from log phase cultures. The blebs originated as evaginations of the outer layer of the cell wall. Bleb production was noted on both defined or complex media either as broth or a solid medium. The addition of 10% normal bovine serum to the various media did not affect the production and release of these surface blebs. However, as broth cultures progressed into the stationary phase of growth, the blebs disappeared from the surface of the cells. Blebs were present in substantial quantities in culture supernatant fluids and on cell surfaces and were readily isolated by ultracentrifugation. Analysis for 2-keto-3-deoxyoctonate in cultures revealed that 18% of the total endotoxin of log phase cultures was present in blebs from the cell wall.

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The nasopharynx of known meningococcal carriers without signs of acute meningococcal disease as well as cerebrospinal fluid from patients with acute meningococcal disease were cultured on Thayer-Martin agar. Pili were observed in negatively stained preparations of over 80% cells from all primary cultures of both nasopharnyx and cerebrospinal fluids. Although pili were abundant on cells from all primary cultures, all pili were lost on serial subculture in the laboratory. This loss of pili from the cell surface on laboratory subculture was not accompanied by a concomitant loss of cell wall blebs.

The 38,200-molecular weight (unreduced)/41,900-molecular-weight (reduced) glycoprotein of bovine rotavirus, isolate C486, was identified as the major neutralizing antigen. This glycoprotein as well as the corresponding glycoprotein of another bovine rotavirus serotype also specifically attached to cell monolayers under normal conditions for virus adsorption in vitro. Further support for this glycoprotein being directly responsible for virus attachment to cells was that (i) infectious virus of both serotypes could compete with the C486 glycoprotein for cell surface receptors, and (ii) neutralizing monospecific antiserum and neutralizing monoclonal antibodies directed toward the glycoprotein could block this virus-cell interaction. Preliminary epitope mapping of the glycoprotein with monoclonal antibodies further localized the neutralization-adsorption domain to a peptide with an approximate molecular weight of 14,000. The effect of two protein modifications, glycosylation and disulfide bridging, on the reactivity of this peptide with antibodies and cell surface receptors was investigated. It was demonstrated that, whereas glycosylation did not appear to affect these reactivities, disulfide bridging seemed to be essential.

SUMMARYSix monoclonal antibodies (MAbs) to bovine coronavirus (BCV, Quebec isolate) E2 and E3 glycoproteins which were found previously to be neutralizing in vitro were examined for virus-neutralizing activity in vivo. Surgically ligated intostinal loops of newborn colostrum-deprived calves were virus-inoculated, mock-inf6cted or inoculated with a mixture of virus and antibody. Of the six BCV-specific MAbs, four were found to be protective against a virulent field isolate of BCV, as indicated by a reduction in villous atrophy. These MAbs were specific to antigenic domain A and antigenic domains A1 and A2 on the E2 and E3 glycoproteins respectively. MAbs to antigenic domains B and C on the E2 and E3 glycoproteins, respectively, were not protective.

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Bovine rotavirus grown in the presence or absence of tunicamycin was analyzed with respect to yield of infectious virus, the ratio of complete to incomplete particles, and polypeptide composition. Tunicamycin at a concentration of 1 Fg/ml reduced virus yields by 4 logs and completely prevented the incorporation of [3H]uridine into complete rotavirus particles, as determined by cesium chloride gradient analysis. Concomitant with a reduction in complete particles, three rotavirus polypeptides shifted in their relative position on poly

In a survey of negatively stained preparations of' the prototype strains of' Neisseria meningitidis, pili were detected on three strains. However, these pili were detected on fewer than 5%(of' cells in populations of' these three strains. Those individual cells with pili were seldom observed to contain more than two or three pili per cell. In contrast, nearly all cells of' the nonprototype group B strain ATCC 13090 had numerous pili on their surfaces. When viewed in frozen-etched replicas, a f'ew pili were observed lying on the cell surface of' this latter strain. An annular structure was also found in frozen-etched replicas. This structure usually consisted of a series of concentric rings that were always found on the flat side of these bean-shaped cells. It is concluded that such structures represent a differentiated portion of the cell wall, which is involved in cross-wall formation during synthesis of the cell septum in dividing cells.