An Interference Phenomenon Associated with a Measles Virus SSPE Isolate (Halle)

Abstract

SUMMARYA measles virus (Halle SSPE isolate) induced ring plaque phenomenon (concentric rings of living and dead cells) has been shown to be associated with the temperaturedependent production of interfering particles. The interfering particles have been purified by potassium tartrate linear gradient centrifugation and have buoyant densities of 1.15 g/ml (M particle) and 1-06 g/ml (L particle) respectively. Both interfering particle populations have been shown to decrease the yield of wild-type measles virus from infected cells by 50% when co-infection experiments were performed. Neither the M or L particle population interfered with the growth of VSV in the same host-cell system.Measles virus (MV), a member of the Paramyxoviridae family (genus Morbillivirus) is currently undergoing extensive investigation, particularly with regard to its possible involvement in the aetiology of certain neurological diseases and/or disorders (ter Meulen & Hall, 1978). Several measles-like viruses (strains?) have been isolated by laboratory co-cultivation techniques, from cases of subacute sclerosing panencephalitis (SSPE) (Horta-Barbosa et al., 1969;Payne et al., 1969).During an investigation of the growth properties of an MV SSPE isolate, designated Halle (MVH), a temperature-dependent plaquing phenomenon (termed ring plaques) was observed. A study of the ring plaque growth phenomenon led to the isolation of MV interfering particles. This communication describes and discusses the possible implications of the phenomenon observed.The MVH isolate (obtained from Dr T. F. Wild, INSERM, Lyon, France) was twice plaque-purified in cultures of Vero cells (ATCC CCL81; Flow Laboratories). As many laboratories have noted that certain strains of MV grow to higher titres at 32 °C than at 37 °C (T. F. Wild, personal communication; A. Salmi, personal communication; this study), the MVH isolate was grown at 32 °C, 37 °C and 39 °C and examined at regular intervals for plaque production. At 5 days post-infection, the virus grown at 37 °C showed plaques with clear centres surrounded by a ring of cells (Fig. 1). As incubation progressed (up to 20 days post-infection) more rings appeared as the plaques enlarged until a concentric ring pattern appeared (ring plaques). Vital dye (neutral red) staining indicated that the ring plaques consisted of alternating, concentric rings of living and dead cells. Plaques observed at 32 °C and 39 °C were distinct from those seen at 37 °C (Fig. i) and at no time were the characteristic ring plaques seen at 32 °C or 39 °C. Use of alternate host-cell systems for plaque titration of the MVH isolate (BSC-1, ATCC CCL26; HEp-2, ATCC CCL23; KB, ATCC CCL17) gave similar results, although the ring plaques produced were considerably smaller in size (not shown). Such results would indicate that the phenomenon is not host-cell dependent. The larger plaque size observed in the Vero host-cell system can be related to the greater efficiency of MV replication in that particular cell system. Plaque titration of the MV LEC SSPE isolat...

Measles Virus Strain-dependent Variation in Outcome of Infection of Human Blood Mononuclear Cells

“…At an m.o.i, of 0.1, the virus released from the few originally infected cells would have the opportunity to undergo several cycles of replication in proliferating cells. The growth of the Hall6 strain to higher titres in Vero cells at 32 °C than at 37 °C has been reported earlier and is associated with the temperature-dependent production of defective interfering particles (Tsang et al, 1981).…”