The specificity of effector T cells activated by tumours induced by murine oncornaviruses

Detection of immunologically cross-reacting capsid protein of alphaviruses on the surfaces of infected L929 cells

Hyperimmune, but not normal immune, monospecific antiserum made to capsid protein of Sindbis virus (SIN) was found to cause cytolysis equally well of both SIN- and Semliki Forest virus-infected L929 cells in antibody-dependent, complement-mediated cytotoxicity assays. The cell surface reactivity of the hyperimmune antiserum was also demonstrated by solid-phase radioimmune assays with unfixed infected cells or infected cells fixed with low concentrations of glutaraldehyde (0.025%) before reactivity with antisera. Higher concentrations of glutaraldehyde lowered the sensitivity of detection. Purified SIN capsid protein specifically inhibited antibody-dependent, complement-mediated cytotoxicity by the monospecific anti-capsid protein serum on SIN- and Semliki Forest virus-infected target cells. That hyperimmune anti-SIN serum also cross-reacts with capsid protein on the surface of Semliki Forest virus-infected cells was suggested by the fact that capsid protein inhibited cross-cytolysis in the antibody-dependent, complement-mediated cytotoxicity assay. The latter antiserum was collected after repeated injections of purified virions over a 9-month period. The results suggest that hyperimmune monospecific antisera made to SIN capsid protein or hyperimmune antisera to SIN or Semliki Forest virions detect homologous and cross-reacting capsid protein determinants on the surface of infected cells.

Adoptive T cell immunotherapy of MSV-induced tumours in nude mice. Part II. Sequential analysis of serum immune complexes and blocking activity in reconstituted mice in relation to tumour biology

In seven separate experiments, nude (nu/nu) mice carrying established murine sarcoma virus (MSV) tumours were reconstituted with syngeneic (+/+) immune splenic T cells. These immune protected mice were randomly divided to provide smaller groups for serial exsanguination. At various time points mice were individually bled and CIC concentration and blocking activity of each individual serum was determined. Control sera were obtained from nu/nu and adult +/+ mice inoculated with tumour cells only, and from nu/nu mice protected with normal +/+ spleen cells. In all the mice studied, CIC and blocking appeared to be mutually independent parameters throughout the MSV tumour course. On the other hand, in immune protected mice considered alone or together with the control groups, CIC and time after tumour cell inoculation, but not tumour size, were significantly correlated. A significant relationship between blocking and tumour size was also established, although this only applied to immune protected mice. However, analysis of the combined data from sequentially bled immune protected mice in relation to different phases of tumour behaviour, did not support the notion that blocking, and more particularly the persistence of CIC, contribute to tumour regrowth and dissemination.