Immune ontogeny and lymphocyte responses to primary herpesvirus infections in Ugandan infants

Herpesviruses cytomegalovirus (CMV) and Epstein-Barr virus (EBV) cause an enormous burden of disease worldwide. Congenital CMV (cCMV) is the most common congenital infection in the world and can cause deafness and intellectual disability. EBV is the causal agent of Burkitt’s lymphoma (most common pediatric cancer in Africa), infectious mononucleosis, and associated with several autoimmune diseases. Age-related differences in symptoms and diseases caused by all herpesviruses likely reflect immune variation early in life, however lymphocyte responses to EBV and CMV are not well documented in young children. Gamma delta (γδ) T cells develop early in gestation and may be important for controlling CMV infection before alpha beta T cell immunity develops. Indeed, a “public” (shared among many individuals) γδ T cell receptor (TCR) clone has been associated with cCMV and may represent an important early response to the virus. In this study we aimed to describe general immune ontogeny and lymphocyte responses to herpesvirus infections in infancy and comprehensively characterize γδ T cell responses to CMV infection in infants. Following a birth cohort of 32 Ugandan infants and their mothers during their first year of life, we captured 20 CMV and 10 EBV primary infections. Using standard flow cytometry, we characterized a wide range of innate and adaptive lymphocytes and further characterized the γδ T cells from a subset of the cohort with a 21-color spectral flow cytometry panel and extracted RNA for TCR sequencing. In the first year of life, there were significant ontological changes within all lymphocyte subsets tested (natural killer (NK) cells, B cells, T cells). NK and T cell compartments experienced the most dramatic changes with CMV infection. Age and CMV infection were correlated with γδ T cells and EBV was not. Unsupervised clustering analyses revealed CMV-specific adaptive-like γδ T cell subsets with effector phenotypes in infants and adults. Our findings provide evidence of the cell types involved in primary herpesvirus infections during infancy and support the notion that γδ T cells are participating in the immune response to CMV infection in early life, providing insight for novel new vaccine designs to more effectively prevent CMV-related disease.Medicine, Faculty ofExperimental Medicine, Division ofGraduat

Characterization of Adaptive-like γδ T Cells in Ugandan Infants during Primary Cytomegalovirus Infection

Gamma-delta (γδ) T cells are unconventional T cells that help control cytomegalovirus (CMV) infection in adults. γδ T cells develop early in gestation, and a fetal public γδ T cell receptor (TCR) clonotype is detected in congenital CMV infections. However, age-dependent γδ T cell responses to primary CMV infection are not well-understood. Flow cytometry and TCR sequencing was used to comprehensively characterize γδ T cell responses to CMV infection in a cohort of 32 infants followed prospectively from birth. Peripheral blood γδ T cell frequencies increased during infancy, and were higher among CMV-infected infants relative to uninfected. Clustering analyses revealed associations between CMV infection and activation marker expression on adaptive-like Vδ1 and Vδ3, but not innate-like Vγ9Vδ2 γδ T cell subsets. Frequencies of NKG2C⁺CD57⁺ γδ T cells were temporally associated with the quantity of CMV shed in saliva by infants with primary infection. The public γδ TCR clonotype was only detected in CMV-infected infants <120 days old and at lower frequencies than previously described in fetal infections. Our findings support the notion that CMV infection drives age-dependent expansions of specific γδ T cell populations, and provide insight for novel strategies to prevent CMV transmission and disease.Science, Faculty ofNon UBCReviewedFacultyResearche

Autoreactivity to sulfatide by human invariant NKT cells

Invariant NKT (iNKT) cells are innate-like lymphocytes that recognize lipid Ags presented by CD1d. The prototypical Ag, alpha-galactosylceramide, strongly activates human and mouse iNKT cells, leading to the assumption that iNKT cell physiology in human and mouse is similar. In this article, we report the surprising finding that human, but not mouse, iNKT cells directly recognize myelinderived sulfatide presented by CD1d. We propose that sulfatide is recognized only by human iNKT cells because of the unique positioning of the 3-O-sulfated beta-galactose headgroup. Surface plasmon resonance shows that the affinity of human CD1d-sulfatide for the iNKT cell receptor is relatively low compared with CD1d-alpha-galactosylceramide (K-D of 19-26 mu M versus 1 mu M). Apolipoprotein E isolated from human cerebrospinal fluid carries sulfatide that can be captured by APCs and presented by CD1d to iNKT cells. APCs from patients with metachromatic leukodystrophy, who accumulate sulfatides due to a deficiency in arylsulfataseA, directly activate iNKT cells. Thus, we have identified sulfatide as a self-lipid recognized by human iNKT cells and propose that sulfatide recognition by innate T cells may be an important pathologic feature of neuroinflammatory disease and that sulfatide in APCs may contribute to the endogenous pathway of iNKT cell activation