Relation between neutralization of Epstein-Barr virus and antibodies to cell-membrane antigens-induced by the virus

The neutralization of Epstein-Barr virus (EBV) infectivity by sera with known antibody activities against EBV-associated antigens was investigated in experimentally infected Raji and RPMI 64-10 cells. Antibodies against EBV-induced cell-membrane antigens were apparently responsible for neutralization of viral infectivity. Antibodies against EBV capsid antigens and EBV-induced early antigens were not involved. The implication of these results on the relationship of the membrane antigens to the infectious virus particle is discussed.

Reactivity of radioiodinated serum antibody from Burkitt's lymphoma and nasopharyngeal carcinoma patients against culture lines derived from Bukrkitt's lymphoma

The IgG serum immunoglobulin fraction of two Burkitt's lymphoma (Mutua and Kiliopa) and one African nasopharyngeal carcinoma patient (Kipkoech) was conjugated to iodine-131 (¹³¹I). It is known from previous studies with fluorescein labelled conjugates that all three sera contain antibody against the Epstein–Barr virus (EBV)-associated membrane antigen complex, present on the surface of lymphoblastoid cells in EBV-carrier cultures. All three radioiodinated conjugates attached to live cells of an EBV-carrying Burkitt line (Maku), but not to EBV-free Raji cells. A Swedish control serum (Berith) did not block the binding of any of the three conjugates, whereas unconjugated sera of Mutua, Kiliopa and Kipkoech showed various degrees of blocking and cross-blocking. The blocking patterns were in good agreement with previous tests, performed with the same sera against their fluorescein conjugated derivatives.

Antibody release tests, involving preincubation of live cells with one of the three conjugates, followed by incubation with unlabelled serum revealed a certain `hierarchy' between the three sera with regard to their ability to displace radioiodinated surface-coupled immunoglobulin. This ability could be related to the competitive behaviour of the same sera in the cross blocking tests. The results are believed to reflect differences in the affinity of the three antibodies, due either to differences in fit in relation to the surface antigen(s) carried by the Maku target cell, or to differences in the duration of immunization in the three patients.

The presence of Moloney virus induced antigen on antibody-producing cells

Mice infected at birth with Moloney virus were stimulated with an unrelated antigen (sheep red blood cells) during the lag period before the outbreak of leukaemia. Their spleen cell suspensions were incubated with anti-Moloney serum and complement before plating by the Jerne technique. This treatment—compared with incubation with normal serum and complement—caused a decrease in number of plaque forming cells in one-fourth of the infected mice, indicating that their antibody producing cells contained virus specific surface antigen.

Epstein-Barr virus-associated antibody patterns in carcinoma of the post-nasal space

Sera from African patients with tumours of the post-nasal space, Hong Kong Chinese patients with carcinomas of the post-nasal space and from Indian donors with buccal, oro- and hypopharyngeal carcinomas, as well as African control sera from healthy persons and individuals with various non-neoplastic and neoplastic diseases were tested for anti-Epstein–Barr virus titres and for antibodies capable of blocking the direct membrane immunofluorescence reaction obtained between Epstein-Barr virus carrying lymphoblastoid cell lines and two different fluorescein conjugated reference sera; one from a patient with Burkitt lymphoma (F-Mutua conjugate) and the other from a patient with carcinoma of the post-nasal space (F-Kipkoech conjugate). Ninety per cent or more of the African and Chinese patients with carcinoma of the post-nasal space gave at least one high test, and 60% were high in all three assays. In contrast, African patients with post-nasal space tumours other than carcinomas, African controls and Indian buccal, oro- and hypopharyngeal carcinomas gave high reactions in all three assays in less than 20%.