A Hypothesis Accounting for the Effect of the Host Cell on Neutralization-resistant Virus

Abstract

SUMMARYEvidence is presented showing thata monkey anti-enterovirus 71 immune serum contains several antibody populations which differ in their mode of function. One population reduces infectivity, although inefficiently, by interactions at exposed antigenic sites and can be detected by measuring residual virus infectivity after mixtures of virus and antibody have been all0wed_.to interact. Another antibody population, which is unaffected by the immunosorbent Staphylococcus aureus (Cowan I strain), appears to attach to its antigenic site(s) only after interactions between enterovirus 71 and host cells have already begun. In view of the transience of (presumed) conformational changes in the invading viruses, demonstration of this type of antibody activity requires a particular host cell system. This second type of antibody neutralization could be detected on RD cells but not on green monkey kidney cells.In comparative plating experiments with partly neutralized vesicular stomatitis virus and echovirus 4, a marked difference in response was found between the two cell types used (Kjell6n & Schlesinger, 1959; Kjell6n &von Zeipel, 1984). The obvious dependence of plaque assay results upon the cells used may help to shed light on controversial questions regarding the nature of the interactions between virus and antibody that result in neutralization.Enterovirus 71 was used in the present study. The strain 52343, notorious for its large 'nonneutralizable' fraction on Vero and green monkey kidney (GMK) cells (von Zeipel, 1979) and the monkey hyperimmune serum, C-898, were kindly supplied by Dr G. von Zeipel (Stockholm, Sweden). Monolayers of cells were prepared and plaque assays performed as described previously (Kjell6n &von Zeipel, 1984). Simultaneous titrations of stocks of enterovirus 71 yielded a similar number of plaques (p.f.u./ml) on monolayers of either GMK cells (GMK-AH1 ; G/inalp, 1965) or rhabdomyosarcoma cells (RD;McAllister et al., 1969). Nine triplicate titrations of a stock of enterovirus 71 yielded on average 5.65 × 105 p.f.u./ml on RD cells and 5.89 x 105 on GMK-AH1 cells with a range of 0.55 to 1.50 in the ratio of these titres.To ascertain the neutralizing capacity of the heat-inactivated immune serum (IS), a suspension of about l0 s p.f.u, of enterovirus 71 was mixed with IS dilutions in phosphatebuffered saline (PBS) of 10 -2, 10 -3 and 10 -4 in a total volume of 2 ml; mixtures were then incubated for 2 h to complete virus-antibody combinations and seeded onto monolayers of GMK or RD cells. The hyperimmune serum neutralized virus infectivity, with a nonneutralizable fraction in all mixtures of about 10 -2 and 10 -1 of control virus for RD and GMK cells respectively. All mixtures showed surviving non-neutralizable fractions of virus which were independent of antibody concentration over the range studied, indicating excess of antibody at all dilutions (Dulbecco et al., 1956). The differences in surviving fractions of infectivity (SFI) between the two cell strains were statistically highly significan...

Insights into neutralization of animal viruses gained from study of influenza virus

“…The way in which a cell type reacts with neutralized virus has received little attention. The erythrocyte is one example but other cells which show quantitative or qualitative differences in neutralization flag this as a factor meriting closer attention [50][51][52]. For example, one monoclonal IgG neutralized La Crosse virus on BHK cells but not on a mosquito cell line while a second monoclonal IgG to the same protein neutralized on mosquito but not BHK cells [53].…”

Mechanism and Significance of Cell Type-Dependent Neutralization of Flaviviruses

“…Antibody-mediated neutralization of viruses may be influenced by the cellular substrates used in in vitro assays, including those employed in the evaluation of vaccines (26)(27)(28)(29)(30)(31)(32). To investigate the underlying mechanism for cell type-dependent neutralization of flaviviruses, we studied the potency of previously characterized monoclonal antibodies (MAbs) on multiple cell types (25,31).…”

“…Cell type-dependent neutralization describes the differential capacity of antibodies to inhibit virus infection when assayed using different cellular substrates, and it has been observed in multiple viral systems (26)(27)(28)(29)(30)32), including flaviviruses (31). Because of the potential for cell type-dependent patterns of neutralization to impact assays of vaccine efficacy, we investigated the underlying mechanism of this phenomenon, of which many have been proposed.…”

“…The use of a very high concentration of virions in neutralization studies may markedly reduce the concentration of free antibody and prevent steady-state binding conditions; under these conditions, viruses escape from neutralization simply because free antibody is depleted (56). Neutralizing antibodies that recognize epitopes uniquely displayed on the virion during the process of viral entry may also contribute to patterns of antibody recognition as a result of virus-cellular factor interactions (28,57).…”

“…The extent of virion maturation is one factor shown to govern how many antibodies bind the virion at a given concentration of antibody (25). In several instances, the results of neutralization assays have been shown to vary when the assays are performed on multiple cellular substrates (26)(27)(28)(29)(30)(31)(32). Interest in cell type-dependent patterns of neutralization is heightened by results of the first large-scale phase IIb clinical study of a tetravalent DENV vaccine (33).…”