CD1d Expression and Invariant NKT Cell Responses in Herpesvirus Infections

Varicella Zoster Virus Downregulates Expression of the Nonclassical Antigen Presentation Molecule CD1d

BACKGROUND

The nonclassical antigen presentation molecule CD1d presents lipid antigens to invariant natural killer T (iNKT) cells. Activation of these cells triggers a rapid cytokine response providing an interface between innate and adaptive immune responses. The importance of CD1d and iNKT cells in varicella zoster virus (VZV) infection has been emphasized by clinical reports of individuals with CD1d or iNKT cell deficiencies experiencing severe, disseminated varicella postvaccination.

METHODS

Three strains of VZV (VZV-S, rOka, and VZV rOka-66S) were used to infect Jurkat cells. Flow cytometry of VZV- and mock-infected cells assessed the modulatory impact of VZV on CD1d protein. Infected cell supernatant and transwell co-culture experiments explored the role of soluble factors in VZV-mediated immunomodulation. CD1d transcripts were assessed by reverse-transcription polymerase chain reaction.

RESULTS

Surface and intracellular flow cytometry demonstrated that CD1d was strikingly downregulated by VZV-S and rOka in both infected and VZV antigen-negative cells compared to mock. CD1d downregulation is cell-contact dependent and CD1d transcripts are targeted by VZV. Mechanistic investigations using rOka-66S (unable to express the viral kinase ORF66) implicate this protein in CD1d modulation in infected cells.

CONCLUSIONS

VZV implements multiple mechanisms targeting both CD1d transcript and protein. This provides evidence of VZV interaction with and manipulation of the CD1d-iNKT cell axis.

Navigating the Role of CD1d/Invariant Natural Killer T-cell/Glycolipid Immune Axis in Multiple Myeloma Evolution: Therapeutic Implications

Multiple myeloma (MM) is an incurable B-cell malignancy. The immunotherapeutic approach for MM therapy is evolving. The Cd1d/invariant natural killer T-cell/glycolipid immune axis belongs to the innate immunity, and we have highlighted role in myeloma pathogenesis in the present study. The recent development of the chimeric antigen receptor (CAR19)-invariant natural killer T-cells resulted in our renewed interest in this immune system and offer new perspectives for future anti-MM immunotherapies.

CD1d highly expressed on DCs reduces lung tumor burden by enhancing antitumor immunity

Dendritic cells (DCs), as professional antigen-presenting cells are essential for the initial activation of adaptive antitumor immunity. CD1d is considered to present phospholipid and glycosphingolipid antigens to NKT cells. However, it is currently unknown whether CD1d expression on DCs is capable of enhancing antitumor immunity, particularly T-cell related immunity. We observed that CD1d was predominantly expressed on DCs in 3LL tumor-bearing mice, whilst a deficiency of CD1d promoted tumor growth. Notably, CD1d expression on DCs was not only required for presenting antigen to NKT cells, but also markedly promoted CD4⁺T and CD8⁺T cell activation, particularly cytotoxic T cells. All the T cells (NKT, CD4⁺T and CD8⁺T cells) upregulated CD69, CD107a and IFN-γ after the adoptive transfer of CD1d-positive DCs (CD1d⁺DCs) and tumor growth was suppressed. With regard to the mechanism, we revealed that CD1d⁺DCs were concomitant with a higher expression of costimulatory molecules (CD40, CD80 and CD86) and MHCI/II, which are essential for DCs to present antigens to T cells. Consistently, CD1d⁺DCs displayed stronger activation-associated-ERK1/2 and NF-κB signals; whereas JAK2-STAT3/6 signaling was required for maintaining a high level of CD1d on DCs. In lung cancer patients, the antitumor activities of all the T cells were enhanced with the increase of CD1d⁺DCs. Analysis of TCGA data revealed that high levels of CD1d indicated better outcomes for patients. Collectively, CD1d enhanced DC-based antitumor immunity, not only by targeting NKT, but also by activating CD4⁺T and CD8⁺T cells. CD1d⁺DCs may be superior to the bulk population of DCs in cancer immunotherapy.

Functional Invariant Natural Killer T Cells Secreting Cytokines Are Associated With Non-Progressive Human Immunodeficiency Virus-1 Infection but Not With Suppressive Anti-Retroviral Treatment

Background

CD1d restricted invariant natural killer T (iNKT) cells are important in the activation and regulation of immune responses. Limited information is available regarding the functional role of iNKT cells in the human immunodeficiency virus (HIV) disease progression.

Methodology

α-GalCer stimulated iNKT cells were characterized for their functionality in terms of cytokine production (IFN-γ, TNF-α, IL-2, IL-4, and IL-21) and CD107a expression in HIV-1 infected [23 long-term non progressors (LTNPs), 28 progressors, 18 patients before and after suppressive anti-retroviral treatment (ART)] along with 25 HIV-1 negative subjects using multicolor flow cytometry.

Results

The functional profile of α-GalCer stimulated iNKT cells was similar in LTNPs and healthy controls. The number of LTNPs showing functional response in terms of secretion of cytokines (IFN-γ/IL2/TNF-α) and CD107a expression was significantly higher than seen in the progressors. The cytokine secretion by the stimulated iNKT cells was predominantly Th1 type. The frequencies of iNKT cells showing secretion of IFN-γ or IL2 or TNF-α or expression of CD107a were higher in LTNPs (p < 0.05 for all) and also significantly associated with lower plasma viral load (p value ranged from 0.04 to 0.003) and higher CD4 count (p value ranged from 0.02 to <0.0001). The functional profile of the iNKT cells before and after ART did not differ significantly indicating absence of restoration of iNKT cells functionality after suppressive ART. The IL-4 and IL-21 secreting iNKT cells were rare in all study populations.

Conclusion

The presence of functional iNKT cells secreting number of cytokines in non-progressive HIV infection could be one of the multiple factors required to achieve HIV control and hence have relevance in understanding the immunity in HIV infection. The failure of restoration of the iNKT functionality after ART should be potential area of future research.

CD1-Restricted T Cells During Persistent Virus Infections: "Sympathy for the Devil"

Some of the clinically most important viruses persist in the human host after acute infection. In this situation, the host immune system and the viral pathogen attempt to establish an equilibrium. At best, overt disease is avoided. This attempt may fail, however, resulting in eventual loss of viral control or inadequate immune regulation. Consequently, direct virus-induced tissue damage or immunopathology may occur. The cluster of differentiation 1 (CD1) family of non-classical major histocompatibility complex class I molecules are known to present hydrophobic, primarily lipid antigens. There is ample evidence that both CD1-dependent and CD1-independent mechanisms activate CD1-restricted T cells during persistent virus infections. Sophisticated viral mechanisms subvert these immune responses and help the pathogens to avoid clearance from the host organism. CD1-restricted T cells are not only crucial for the antiviral host defense but may also contribute to tissue damage. This review highlights the two edged role of CD1-restricted T cells in persistent virus infections and summarizes the viral immune evasion mechanisms that target these fascinating immune cells.