The E5 protein of human papillomavirus type 16 perturbs MHC class II antigen maturation in human foreskin keratinocytes treated with interferon-γ

ABSTRACT Extracellular Yersinia pseudotuberculosis employs a type III secretion system (T3SS) for translocating virulence factors (Yersinia outer proteins [Yops]) directly into the cytosol of eukaryotic cells. Recently, we used YopE as a carrier molecule for T3SS-dependent secretion and translocation of listeriolysin O (LLO) from Listeria monocytogenes. We demonstrated that translocation of chimeric YopE/LLO into the cytosol of macrophages by Yersinia results in the induction of a codominant antigen-specific CD4 and CD8 T-cell response in orally immunized mice. In this study, we addressed the requirements for processing and major histocompatibility complex (MHC) class II presentation of chimeric YopE proteins translocated into the cytosol of macrophages by the Yersinia T3SS. Our data demonstrate the ability of Yersinia to counteract exogenous MHC class II antigen presentation of secreted hybrid YopE by the action of wild-type YopE and YopH. In the absence of exogenous MHC class II antigen presentation, an alternative pathway was identified for YopE fusion proteins originating in the cytosol. This endogenous antigen-processing pathway was sensitive to inhibitors of phagolysosomal acidification and macroautophagy, but it did not require the function either of the proteasome or of transporters associated with antigen processing. Thus, by an autophagy-dependent mechanism, macrophages are able to compensate for the YopE/YopH-mediated inhibition of the endosomal MHC class II antigen presentation pathway for exogenous antigens. This is the first report demonstrating that autophagy might enable the host to mount an MHC class II-restricted CD4 T-cell response against translocated bacterial virulence factors. We provide critical new insights into the interaction between the mammalian immune system and a human pathogen.

Download Full-text

H2-M and H2-O as Targeting Vehicles for the MHC Class II Processing Compartment Promote Antigen-Specific CD4+ T Cell Activation

Vaccines ◽

10.3390/vaccines9101053 ◽

2021 ◽

Vol 9 (10) ◽

pp. 1053

Author(s):

Lucia Lapazio ◽

Monika Braun ◽

Kaj Grandien

Keyword(s):

T Cell ◽

Mhc Class Ii ◽

T Cell Activation ◽

Cell Activation ◽

Class Ii ◽

Cd4 T Cell ◽

Antigen Presentation Pathway ◽

Presentation Pathway ◽

Class Ii Antigen ◽

Mhc Class Ii Antigen

CD8 and CD4 T cell activation are both required for a strong and long-lasting T cell immune response. Endogenously expressed proteins are readily processed by the MHC class I antigen presentation pathway, enabling activation of CD8+ T cells. However, the MHC class II antigen presentation pathway, necessary for CD4+ T cell activation, is generally not sufficiently accessible to endogenously expressed proteins, limiting the efficiency of mRNA- or DNA-based vaccines. In the current study, we have evaluated the feasibility of using antigen sequences fused to sequences derived from the H2-M and H2-O proteins, two complexes known to participate in MHC class II antigen processing, for the enhancement of CD4 T-cell activation. We analyzed T cell activation after genetic immunization with mRNA-encoding fusion proteins with the model antigen ovalbumin and sequences derived from H2-M or H2-O. Our results show that H2-M- or H2-O-derived sequences robustly improve antigen-specific CD4 T-cell activation when fused to the antigen of interest and suggest that the approach could be used to improve the efficiency of mRNA- or DNA-based vaccines.

Download Full-text

Release of granulocyte-macrophage colony stimulating factors from major histocompatibility complex class II antigen-positive monocytes is enhanced by human gamma interferon

Blood ◽

10.1182/blood.v66.6.1343.bloodjournal6661343 ◽

1985 ◽

Vol 66 (6) ◽

pp. 1343-1351

Author(s):

W Piacibello ◽

L Lu ◽

M Wachter ◽

B Rubin ◽

HE Broxmeyer

Keyword(s):

T Lymphocytes ◽

Mhc Class Ii ◽

Human Peripheral Blood ◽

Class Ii ◽

Gamma Interferon ◽

Colony Stimulating Factors ◽

Gm Csf ◽

Macrophage Colony ◽

Class Ii Antigen ◽

Mhc Class Ii Antigen

Human gamma interferon (HuIFN gamma) was assessed for its capacity to enhance release of granulocyte-macrophage colony stimulating factors (GM-CSF) from human peripheral blood monocytes. Natural HuIFN gamma (2 X 10(7) NIH reference units per milligram) at concentrations as low as 0.01 U/mL to 10 U/mL reproducibly enhanced release of GM-CSF. This enhancement was detected when T lymphocytes were depleted from monocyte preparations and when T lymphocytes and monocytes were depleted from populations of human bone marrow cells stimulated by monocyte- conditioned media to form colonies and clusters. T lymphocytes alone or in the presence of HuIFN gamma did not release GM-CSF. The enhancing activity of HuIFN gamma was removed by preincubating HuIFN gamma with neutralizing concentrations of monoclonal anti-HuIFN gamma, and recombinant HuIFN gamma mimicked the effects of natural HuIFN gamma, suggesting that the effects were due to HuIFN gamma itself. HuIFN gamma suppression of the release of inhibitory activity from monocytes was ruled out as a reason for the noted enhancing activity of HuIFN gamma. The enhancing activity of HuIFN gamma was confined to the MHC class II antigen-positive population of monocytes. Removal of these cells with monoclonal antibody plus complement (c') ablated the enhancing activity, high concentrations of certain monoclonal antibodies in the absence of c' blocked the enhancing activity and, when monocytes were sorted into MHC class II antigen-positive and -negative cells by fluorescence-activated cell sorting, it was only the positive cell fraction that responded to the enhancing activity of HuIFN gamma.

Download Full-text