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Antibody-mediated growth of influenza A NWS virus in macrophagelike cell line P388D1
H Ochiai1, M Kurokawa, K Hayashi
1Department of Virology, Toyama Medical and Pharmaceutical University, Japan.
Abstract:
We investigated the internalization and growth of influenza A NWS virus in macrophagelike P388D1 cells. Flow cytometric analysis using fluorescein isothiocyanate-labeled virus showed that the attachment of normal rabbit serum-exposed virus (NS-V) to neuraminidase (NA)-treated cells was noticeably limited compared with that to untreated cells. However, rabbit antiserum-exposed virus (AS-V) could attach equally well to both cells. Virus coated with Fab prepared from antiviral immunoglobulin G could not attach. These data suggest that the NWS virus can infect P388D1 cells in one of two ways, via viral or via Fc receptors, depending on the presence of antibodies. The NS-V could grow in the untreated cells, but not in the NA-treated cells. The highest growth of AS-V in the NA-treated cells was observed at an antibody concentration showing 50% plaque reduction titer. Growth was exponentially decreased toward the lower and higher dilutions of antibodies. By using three different immunoglobulin G subclasses of monoclonal antibodies against hemagglutinin, it was demonstrated that both Fc receptors I and II could take part in this phenomenon. The presence of 20 mM NH4Cl inhibited the growth of both AS-V and NS-V, suggesting that the intracellular pathways after internalization via Fc or viral receptors are similar. These data indicate that the concentration of antibodies has a critical role on the antibody-mediated growth of influenza virus in macrophages.
Insights
Influenza virus infects macrophages via viral or Fc receptors, depending on antibody presence. Antibody concentration critically impacts virus growth, suggesting targeted therapies for influenza.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Influenza A virus infects various cell types, including macrophages.
- Macrophage Fc receptors can bind antibody-opsonized particles, influencing immune responses.
- Understanding virus-macrophage interactions is crucial for developing antiviral strategies.
Purpose of the Study:
- To investigate the mechanisms of influenza A NWS virus internalization and replication in macrophage-like P388D1 cells.
- To determine the role of antibodies and Fc receptors in influenza virus infection of macrophages.
- To elucidate the impact of antibody concentration on virus growth in macrophages.
Main Methods:
- Flow cytometry using fluorescein isothiocyanate-labeled influenza A virus.
- Treatment of cells with neuraminidase (NA) to remove viral receptors.
- Exposure of virus to normal serum (NS-V) or antiserum (AS-V) and Fab fragments.
- Assessment of virus attachment and growth in P388D1 cells.
- Utilizing immunoglobulin G subclasses and monoclonal antibodies against hemagglutinin.
- Inhibition studies using ammonium chloride (NH4Cl).
Main Results:
- Influenza virus attachment to macrophages occurs via viral receptors (neuraminidase-sensitive) or Fc receptors (antibody-dependent).
- Neuraminidase treatment of cells limits attachment of non-opsonized virus but not antibody-opsonized virus.
- Antibody-mediated virus growth in macrophages is dependent on antibody concentration, with optimal growth at specific titers.
- Both Fc receptors I and II are involved in the antibody-mediated uptake and growth of influenza virus.
- Inhibition of intracellular pathways with NH4Cl suggests similar post-internalization routes regardless of receptor type.
Conclusions:
- Influenza virus employs dual entry pathways into macrophages: viral receptors and Fc receptors.
- Antibody concentration is a critical determinant of influenza virus replication in macrophages.
- Fc receptor-mediated entry and subsequent replication highlight a potential target for therapeutic intervention in influenza infections.