Edmonston measles virus prevents increased cell surface expression of peptide-loaded major histocompatibility complex...

Area of Science:

• Immunology
• Virology

Background:

• Interferon-gamma (IFN-γ) upregulates MHC expression, while Interferon-alpha/beta (IFN-α/β) can suppress MHC class II. Measles virus (MV) is known to induce IFN-α/β and has been reported to upregulate MHC class II.
• A paradox exists regarding MV's effect on MHC class II expression, as it induces IFN-α/β, which typically suppresses MHC class II.

Purpose of the Study:

• To investigate the surface expression of MHC class I and class II proteins in MV-infected peripheral monocytes.
• To resolve the apparent paradox of MV's influence on MHC class II expression in the presence and absence of IFN-α/β.

Main Methods:

• Purified monocytes were infected with Edmonston B MV.
• Surface expression of MHC class I (HLA-A, -B, -C) and class II (HLA-DR) proteins was analyzed.
• IFN-α/β and IFN-γ levels in supernatant fluids were measured.
• Monocytes were cocultured with peripheral blood mononuclear cell (PBMC) supernatant.

Main Results:

• MV infection of monocytes increased cell surface expression of MHC class I proteins but had no effect on MHC class II expression.
• MV-infected monocytes produced IFN-α/β, with no detectable IFN-γ.
• MV infection of PBMCs also increased MHC class I expression, without affecting MHC class II expression.
• MV suppressed class II protein expression independently of IFN-α/β presence.

Conclusions:

• MV interferes with the expression of peptide-loaded MHC class II complexes on monocytes.
• This interference may alter CD4(+) T-cell proliferation and regulate cell-mediated immune responses.
• The findings suggest a mechanism by which MV modulates the host immune system beyond the known effects of IFN-α/β.