Immune enhancement of the tumorigenicity of hamster brain tumor cells persistently infected with measles virus

Newcastle disease virus (NDV): brief history of its oncolytic strains

BACKGROUND

While genetically engineered viruses are now being tested for the virus therapy of human cancers, some naturally occurring viruses display unmatched oncolytic activity. Newcastle disease virus (NDV) excels as an oncolytic agent.

OBJECTIVES

As its virulence versus attenuation can be explained on molecular biological bases, it may be possible to develop or select highly oncolytic strains of NDV without adverse toxicity.

STUDY DESIGN

Questions are posed as to the mechanisms of viral oncolysis, the appropriateness of tests to predict oncolytic activity of a given NDV strain and the best modes of administration for oncolytic effects. Answers are provided based on specific data or on considerations drawn from experience (the authors use NDV oncolysates to immunize against melanoma and kidney carcinoma) or from analogous clinical situations (therapeutic use of mumps or measles viruses).

RESULTS AND CONCLUSIONS

NDV oncolysates probably suit better for immunotherapy (providing also active tumor-specific immunization) than massive repeated inoculations of NDV strains, especially when the NDV strain used is not proven to be oncolytic by appropriate pre-clinical tests.

Augmented immunogenicity of Lewis lung carcinoma by infection with herpes simplex virus type 2

In vitro, LLT cells sustain HSV-2 replication without evidence of lysis. Simultaneously, multiplication of the cells is stimulated. These xenogenized cells were tested for their immunopotentiating capacity: three-step immunization with xenogenized viable cells conferred significantly augmented transplantation resistance to a challenge graft with 4 x 10(4) intact LLT cells. Latency periods preceding tumor formation were increased and 15% of the mice failed to form primary tumors. Metastasis was likewise decreased and 25% of the mice had healthy lungs. Immunopotentiation, however, did not suffice to significantly protect against a challenge with 6 x 10(4) intact cells. The presence of virus-specific neoantigens on HSV-2-infected viable cells was demonstrated by the progressively increasing number of rejections of 4 x 10(4) xenogenized cells during the successive immunization steps. Immunization with non-viable LLT cells did not augment resistance to challenge.

Hamster brain tumor cells persistently infected with measles-subacute sclerosing panencephalitis virus

A persistent infection was established in a cell line derived from a hamster brain tumor (HBT) with the HBS strain of measles-subacute sclerosing panencephalitis (SSPE) virus. The persistently infected cells (HBT-M) were studied with regard to their growth in vitro and their transplantability in vivo. Although the growth of the HBT-M cells paralleled that of the HBT cells in vitro their transplantability was decreased in weanling hamsters. Hydrocortisone treatment of the hamsters abrogated the lowered transplantability restoring the tumor-producing capacity to levels comparable to the HBT cells. The decreased cell growth of the HBT-M cells in vivo was attributed to the acquisition of measles virus (MV) antigens and the host immune response directed against these new antigens.