SUMMARYThe electrophoretic mobilities of the two genome segments and the structural polypeptides of the chicken strain Cu-1 (serotype I) and the turkey isolate 23/82 (serotype II) of infectious bursal disease virus were compared. There is a close antigenic relationship between the smaller of the two major structural proteins (32K) of both strains. Neutralizing monoclonal antibodies are induced by the larger protein (40K in Cu-1) which differentiates between the two serotypes. The 40K structural protein also has epitopes which do not induce neutralizing antibodies and which are common to both strains. There is evidence that the antigenic region responsible for the production of neutralizing antibodies is highly conformation-dependent. Passively administered neutralizing antibodies directed against the 40K structural polypeptide of Cu-1 confer protective immunity to susceptible chickens, whereas antibodies directed against the 32K structural protein do not have any protective effect. INTRODUCTIONThe basic structure of the infectious bursal disease virus (IBDV), the aetiological agent of a disease of chickens which results in the destruction of the bursa of Fabricius, has been elucidated (Nick et al., 1976; M/iller et al., 1979) and has been shown to exhibit the structural characteristics of the Birnaviridae (Dobos et al., 1979;Brown, 1986). During the past few years isolates of IBDV from turkeys have been reported to be essentially identical to the chicken strains, but the turkey isolates were not pathogenic and could be distinguished by neutralization (McNulty et al., 1979;Jackwood et al., 1982); a second serotype was therefore established (McFerran et al., 1980). In order to localize the antigenic determinants on the structural proteins of IBDV which are responsible for the induction of neutralizing antibodies, a more detailed comparative analysis of the two types of viruses was necessary. Attempts were therefore made to obtain more precise information about the size of the two genomic segments ofdsRNA and the structural proteins of the turkey strain in relation to the known elements of the chicken virus. The antigenic sites which both types of viruses have in common and those which permit their distinction were traced with monoclonal antibodies. The need for a more precise analysis of the antigenic structure of IBDV was underlined by the attempts of other authors to describe antigenic regions which would lend themselves to the production of a vaccine in Escherichia coli or by peptide synthesis (Fahey et al., 1985a,b;Azad et al., 1986;Hudson et al., 1986).

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SUMMARYA seroepidemiological study of naturally occurring antibodies to the human syncytial virus has been carried out by means of an indirect immunofluorescence test on 639 East Africans, consisting of 493 normal Ugandans, 66 Kenyan patients with nasopharyngeal carcinoma (NPC), and 80 Kenyan and Tanzanian patients with various other tumours or non-cancerous conditions. It was found that 3"4% of the normal individuals had antibodies to the virus and serial serum samples were available from I4 of these, permitting the study of antibody class in seroconversion and antibody persistence. As in an earlier survey, a significantly higher incidence of antibodies was found amongst NPC patients. Blocking and indirect immunofluorescence tests with simian foamy viruses (SFV) showed some cross-reactivity between SFV 6 and the human syncytial virus, but not identity. The results are discussed in relation to the very real occurrence of natural infection by human syncytial virus in certain geographical regions.

According to a recommendation from WHO (World Health Organisation) for prevention of a possible rabies infection, active vaccination has to be combined with application of immunoglobulin to get a fast protective effect. At present, preparations of purified human or equine rabies-specific immunoglobulin are used. We have generated a human rabies-specific monoclonal antibody (huMAb) by immortalization of human B-cells with Epstein Barr Virus (EBV), followed by fusion with a mouse myeloma cell. The resulting clone TW-1 secrets an IgG1 lambda huMAb which specifically reacts in ELISA with 5 laboratory rabies virus strains of serotype 1 and DUV3 (Duvenhage, serotype 4). Western Blot analysis revealed fine specificity for the G glycoprotein (gp67) of rabies virus. HuMAb TW-1 neutralizes rabies virus in vitro (RFFIT) as well as in vivo and protects rabies infected mice. Compared to polyclonal human rabies immunoglobulins, huMAb TW-1 is advantageous, because of its defined specificity and the very low amounts of total protein needed for therapeutic effects.

The reactivity of chicken, human, rat and mouse lymphoid tissues with human serum containing smooth muscle antibody was studied by indirect immunofluorescence. In bursal follicles, strong fluorescence was observed predominantly in the lymphocytes and reticular epithelial cells of the medulla, the basement membrane and a row of undifferentiated epithelial cells at the corticomedullary junction. Reticular epithelial cells in lymphocyte-depleted bursas from cyclophosphamide-treated chickens and cultures of bursal and thymic reticular epithelial cells also reacted with smooth muscle antibody. The thymus of all species showed only medullary staining; lymph nodes, spleen and gut-associated lymphoid tissue showed extensive cell staining of both T and B lymphocyte dependent areas, with weak reactivity in germinal centres. Embryologically, the time of appearance of bursal and thymic lymphocyte staining coincided with the development of medullary lymphocytes. In organ imprints and cell smears of bursa, thymus, lymph node and spleen, and in cell smears of bone marrow and peripheral blood lymphocytes, immunofluorescent staining was restricted to cells in close contact with each other. Suspensions of dispersed viable lymphoid cells were negative. Specificity of the staining reaction was established by its prevention after neutralization: absorption of the serum with homogenates of smooth muscle or actin derived from the same source. It is concluded that an actin-like protein is present in mature B and T lymphocytes and in reticular epithelial cells and that its expression in lymphocytes appears dependent on cell-to-cell contact. The presence of the actin-like protein in mature lymphocytes may provide a means of lymphocyte motility in vivo.