Two neutralizing monoclonal antibodies (MCAs), R63 and B69, were used in antigen-capture enzyme immunoassays to verify the presence of infectious bursal disease virus (IBDV) in infected bursal tissues. The intra-serotype-common neutralization site defined by the R63 MCA was present on all IBDV isolates and laboratory strains tested. However, the neutralization site defined by the B69 MCA was found on only classic or older IBDV strains; it was not found on recently isolated variants of IBDV or on a majority of recent field viruses examined. The data suggest that a major antigenic shift in IBDV has occurred in the field and that this shift involves, at a minimum, the deletion or alteration of one of two neutralization sites previously found on classic IBDV strains.

Two somatic cell hybridizations were performed utilizing splenocytes from mice immunized with one or more strains of infectious bursal disease virus (IBDV). Supernatants from hybridoma cell lines were initially screened by the enzyme-linked immunosorbent assay (ELISA) against multiple strains of IBDV. Cell lines that secreted antibodies with ELISA reactivity patterns of interest were cloned, and their monoclonal antibodies (MCAs) were subsequently tested in cross-virus-neutralization tests. Two of the nine MCAs selected exhibited strong neutralizing activity and precipitated IBDV antigens in agar gel precipitin tests as well. MCA B69 significantly neutralized only the cloned D78 strain of IBDV, whereas MCA R63 neutralized all IBDV strains (representing both serotype I and II viruses) against which it was tested. Results of competitive ELISAs that used the R63 and B69 MCAs showed that the two neutralization sites on the D78 strain were not overlapping.

Bovine mammary secretory cells, isolated at necropsy, were cultured in vitro and used as a model to study the mode of adherence of Staphylococcus aureus to mammary epithelium. Cultured cells were characterized by their morphology and physiology as secretory epithelial cells. Cells showed characteristic growth patterns when grown on polystyrene, fibronectin, laminin, collagen, and reconstituted basement membrane from the Engelbreth-Holm-Swarm murine sarcoma. Cells cultured on collagen formed confluent monolayers and were the most suitable for bacterial adherence studies. Cultured cells stained intensely for cytokeratin and for specific milk proteins, i.e., alpha-casein, beta-casein, alpha-lactalbumin, beta-lactoglobulin, and lactoferrin. The effect of frozen storage for 10 mo on cell viability or presence of milk proteins was minimal. Staphylococcus aureus showed large affinity for extracellular matrix components, i.e., fibronectin, laminin, and collagen. Adherence to confluent cell monolayers was minimal. In preconfluent cell monolayers, most S. aureus adhered more readily to the exposed matrix than to the epithelial cells. Overnight exposure to staphylococcal alpha-toxin greatly increased adherence of S. aureus to confluent monolayers. However, whether bacteria adhered to alpha-toxin damaged cells or to exposed matrix is not clear. Unencapsulated S. aureus adhered in larger numbers than did encapsulated S. aureus.

The constant-virus variable-serum neutralization test in chicken tracheal organ cultures was employed in cross-neutralization tests with the following infectious bronchitis viruses: Massachusetts 41, Connecticut, Iowa 97, Iowa 609, Holte, JMK, Clark 333, SE 17, Florida, and Arkansas 99. These viruses all proved serologically distinct by this method. Chickens immunized with the Connecticut strain and later challenged with Arkansas 99 were not protected against it.

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