PubMed Health⌕ Search

Biomedical subjects

Johan K Sandberg

Publications and source records attributed to Johan K Sandberg.

At least 19 recordsLinked to original sources
PubMed2006

Detection of macaque perforin expression and release by flow cytometry, immunohistochemistry, ELISA, and ELISpot.

Simian immunodeficiency virus (SIV)-infection in macaques provides an important animal model for human immunodeficiency virus-1 (HIV-1) infection. The involvement of perforin (PFN), released by cytotoxic cells to mediate killing of virus-infected cells, has been difficult to assess in this experimental model due to a lack of reagents. We therefore evaluated monoclonal antibodies (mAbs) Pf-80, Pf-164 and Pf-344, previously raised against human PFN, for cross-reactivity with macaque PFN. Mabs Pf-164 and Pf-344 reacted with intracellular PFN in peripheral blood mononuclear cells (PBMC) from cynomolgus and rhesus macaques by flow cytometry and stained PFN in rhesus lymphoid tissue by immunohistochemistry (IHC). Moreover, PFN capture enzyme-linked immunosorbent (ELISA) and enzyme-linked immunospot (ELISpot) assays utilizing mAbs Pf-164/Pf-80 for capture and mAb Pf-344 for detection were used to quantify PFN release by mitogen-stimulated cynomolgus and rhesus PBMC. The PFN ELISpot was further used to quantify antigen-specific CD8+ T cells by ex vivo stimulation of PBMC from cynomolgus macaques immunized against SIV/HIV-1. These macaque PFN-reactive mAbs and immunoassays will be valuable new tools for investigation of cytotoxic T lymphocyte (CTL) responses in non-human primate models of infectious diseases as well as for vaccine development.

Animals↗
PubMed2006

CD8 T cell effector maturation in HIV-1-infected children.

HIV-1 infection generates maturational responses in overall CD4 and CD8 T cell populations in adults, with elevated expression of lytic effector molecules perforin and granzyme B, and reduced expression of CCR7 and CD45RA. Here, we have found that these marked effects were significantly less pronounced in children, both in terms of the skewed CCR7/CD45RA expression profile as well as the increased perforin expression. Similar to adults, HIV-specific CD8 cells in children were largely CD27+ CD45RA- and lacked perforin. However, one pediatric subject with late-stage infection displayed robust expansion of Gag 77-85-specific CD8 T cells which were perforin+ and lytic, but lacked expression of CD27 and IFNgamma. Our data indicate that the T cell effector maturation induced by HIV-1 infection is markedly weaker in children as compared to adults. The data also suggest, however, that the perforin-deficient state of HIV-specific CD8 T cells in children may be reversible.

Adolescent↗
PubMed2006

Perforin expression in the gastrointestinal mucosa is limited to acute simian immunodeficiency virus infection.

Perforin-mediated cytotoxicity is a major effector function of virus-specific CD8 T cells. We have investigated the expression of perforin in the gut, an important site of simian immunodeficiency virus (SIV) pathogenesis, during experimental SIV infection of rhesus macaques. We observed significant increases in perforin protein and mRNA expression levels in the colons of SIV-infected macaques as early as 21 days after infection. However, during chronic infection, despite ongoing viral replication, perforin expression returned to levels similar to those detected in SIV-naïve animals. These findings demonstrate the presence of a robust perforin-positive response in gastrointestinal CD8 T cells during acute, but not chronic, SIV infection.

Acute Disease↗
PubMed2005

Expansion of CD1d-restricted NKT cells in patients with primary HIV-1 infection treated with interleukin-2.

Innate CD1d-restricted natural killer T (NKT) cells are infected and lost in HIV-1-infected patients, and this could contribute to HIV-1 pathogenesis because NKT cells play an important role in directing both adaptive and innate immunity. Administration of interleukin-2 (IL-2) to HIV-1-infected patients leads to substantial and sustained CD4+ T-cell expansion, involving both naive and memory cells. We investigated whether IL-2 treatment could restore the NKT cell compartment in patients with primary HIV-1 infection. We show that IL-2 combined with effective antiretroviral therapy (ART) resulted in significant expansion of CD1d-restricted NKT cells. Expansion occurred in both the CD4- and CD4+ subsets of NKT cells, and expanded cells expressed the CD161 maturation marker while expression of the HIV coreceptor CCR5 was reduced. These data indicate that IL-2 treatment in combination with effective ART is beneficial for the restoration of innate NKT cell immunity in patients with primary HIV-1 infection.

Adult↗
PubMed2005

Higher frequency of HIV-1-specific T cell immune responses in African American children vertically infected with HIV-1.

The progression of human immunodeficiency virus (HIV) disease and plasma levels of HIV may differ between racial groups. We compared HIV-specific T cell responses between vertically HIV-1-infected Hispanic and African American children. Subjects were matched for sex, age, viral load, and CD4(+) cell count in 18 pairs; T cell responses were measured by cytokine-enhanced interferon- gamma assay. Peripheral blood mononuclear cells were stimulated with HIV consensus peptides from Gag, Nef, and Tat. The influence of ethnicity, sex, age, viral load, and CD4(+) cell count on T cell responses was determined through linear regression analyses. After adjustment for CD4(+) count, age, and log(10) viral load, African American children demonstrated significantly higher Gag responses (average, 486 spot-forming cells higher; P=.01) than Hispanic children; this was significantly driven by robust responses in African American girls near the age of puberty, many of whom carried the human leukocyte antigen class I B*58 allele.

Adolescent↗
PubMed2005

Development and function of CD1d-restricted NKT cells: influence of sphingolipids, SAP and sex.

Natural killer T (NKT) cells are innate-like lymphocytes with immunoregulatory properties. They express an invariant and conserved T-cell receptor that recognizes glycolipids presented by CD1d. Manipulation, activation or loss of NKT cells has profound effects on diverse immune functions and can influence desirable responses to infectious organisms and tumors, as well as undesirable responses to autoantigens. Here, we discuss recent progress in the identification of natural endogenous and exogenous CD1d-presented antigens, the understanding of factors that regulate development of NKT cells in the thymus and of factors that influence their function in the periphery. Clinical implications of these findings are briefly touched on.

Animals↗
PubMed2004

Expansion of CD7(low) and CD7(negative) CD8 T-cell effector subsets in HIV-1 infection: correlation with antigenic load and reversion by antiretroviral treatment.

The antiviral response of CD8 T cells involves the differentiation of naive T cells into distinct types of effector and memory cells, which may be distinguished by the level of CD7 expression. We have investigated CD8 T cells in adults and children infected with HIV-1 to determine the disease relevance of cell subsets defined by CD7. CD8 T cells from patients infected with HIV-1 displayed profound down-modulation of CD7 expression as compared with healthy subjects, with expansion of both CD7(low) and CD7(negative) effector subsets. Loss of CD7(high) cells correlated directly with HIV-1 load and was particularly pronounced in patients with rapid disease progression. CD8 T cells specific for HIV-1, as well as Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were predominantly found in the CD7(low) effector cell subset. Furthermore, recovery of CD4 counts on antiretroviral therapy was associated with reversion of the skewed CD7 profile in CD8 T cells. Thus, effector CD8 T-cell subsets distinguished by lowered CD7 expression expand in a manner that correlates with the magnitude of HIV-1, EBV, and CMV antigenic challenge and contract in response to successful antiretroviral treatment. The results are discussed in relation to the dual roles of CD7 as a receptor of both costimulation and cell death.

Adult↗
PubMed2004

Abundant expression of granzyme A, but not perforin, in granules of CD8+ T cells in GALT: implications for immune control of HIV-1 infection.

Because GALT is a major portal of entry for HIV-1 and reservoir for viral replication, we hypothesized that an ineffective cellular immune response in intestinal mucosa might partially explain the failure of immune control in AIDS. In this study, we demonstrate that the vast majority of CD8+ T cells in rectal tissue, including HIV-1-specific cells, fail to express the cytolytic protein, perforin. However, rectal CD8+ T cells do express granzyme A, and are also capable of releasing IFN-gamma upon stimulation with cognate peptide. Confocal microscopy showed that granzyme A was located in intracellular granules in the absence of perforin. The majority of rectal CD8+ T cells exhibit an effector memory phenotype, expressing CD45RO but not CCR7. Quantitative real-time PCR analysis demonstrated that perforin RNA is expressed in rectal CD8+ T cells from healthy and HIV-1-positive individuals. In HIV-1-positive individuals, similar amounts of perforin RNA were detected in CD8+ T cells from rectal tissue and PBMC, despite a relative absence of perforin protein in rectal tissue. These findings demonstrate an important difference in perforin expression between CD8+ T cells in blood and mucosa. Furthermore, the relative absence of armed effector cells may serve to protect the integrity of rectal mucosa under normal conditions, but might also provide an early advantage to HIV-1 and other sexually transmitted viruses.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Development of innate CD4+ alpha-chain variable gene segment 24 (Valpha24) natural killer T cells in the early human fetal thymus is regulated by IL-7.

Natural killer (NK) T cells are innate CD1d-restricted immune cells involved in regulation of immune tolerance, tumor immunity, and immunity to infectious pathogens. Human alpha-chain variable gene segment 24 (Valpha24) NK T cells exist in the periphery as two functionally distinct subsets: one CD4+ and one CD4- subset. However, the developmental pathway of human Valpha24 NK T cells is not well understood. Here, we show that Valpha24 NK T cells develop in the fetal thymus. The relative number of intrathymic NK T cell precursors decline in a linear manner with gestational age, and they are very rare in the neonatal thymus, indicating that these cells preferentially develop in the early fetal thymus. Their restriction element, CD1d, is expressed by a vast majority of thymocytes. A majority of intrathymic Valpha24 NK T cell progenitors are CD4+, whereas a minority are CD4/8(+/+). CD4+ Valpha24 NK T cell precursors show features of mature NK T cells, such as high levels of their semiinvariant T cell receptor and CD3 and some expression of CD161, whereas the CD4/8(+/+) precursors seem less mature. The cytokine IL-7 shows a biphasic effect on Valpha24 NK T cell progenitors in fetal thymic organ culture, with high doses driving proliferation of immature CD161-progenitors and low doses supporting survival and maturation. Thus, the data demonstrate that human Valpha24 NK T cells of the CD4+, but not the CD4-, subset develop in the early fetal thymus. Furthermore, data suggest an intrathymic pathway of CD4+ Valpha24 NK T cell development that is regulated by IL-7.

CD4 Antigens↗
PubMed2003

Changes in CD4+ T-cell differentiation phenotype during structured treatment interruption in patients with chronic HIV-1 infection.

Markers of maturation and activation were measured on peripheral CD4+ T cells in chronically HIV-1-infected patients in a randomized, controlled pilot study of structured treatment interruption (STI). Eight subjects underwent 2 cycles of 1 month off and 1 month on highly active antiretroviral therapy (HAART), followed by a final 3-month interruption. During STI, CD4+ T-cell percentage remained relatively stable in 4 of 8 subjects. The remaining 4 STI subjects had significant rapid decline in CD4+ T-cell percentage during STI, followed by return to pre-STI baseline while on HAART. Changes in overall CD4+ T-cell percentage corresponded with fluctuations in the CD45RA+CCR7+ naive and CD45RA-CCR7+ central memory subsets. Subjects with variable CD4+ T-cell percentages tended to have higher pre-HAART plasma HIV-1 RNA set-points and experienced higher levels of plasma HIV-1 RNA rebound during STI. These results suggest that interruptions should be avoided whenever possible in patients on HAART with high plasma HIV-1 RNA set-points.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Presence of human immunodeficiency virus-1-specific CD4 and CD8 cellular immune responses in children with full or partial virus suppression.

The present study assessed antiviral T cell immune responses in 48 human immunodeficiency virus (HIV)-infected children with a stable or decreasing CD4(+) T cell counts and different levels of viral control, in the presence or absence of antiretroviral therapy. Children with full (<40 copies/mL) or partial (<50,000 copies/mL) virus suppression and with a history of stable CD4(+) T cell counts had significantly increased levels of anti-HIV CD4(+) T cell lymphoproliferative responses, lower levels of CD38(+), and higher CD8(+)/CD28(+) T cell percentage, compared with those in treated children with a lack of virus suppression (>50,000 copies/mL). Levels of anti-HIV CD8(+) T cell activity, although higher in treated children with a lack of virus suppression, were not significantly different between the groups. Although levels of anti-HIV CD4(+) and CD8(+) T cell responses were not associated, these levels of responses were associated with the percentage of specific T cell subsets. Overall, a history of stable CD4(+) T cell counts, as a result of therapy that imparted full or partial virus suppression, was associated with increased levels of anti-HIV CD4(+) T helper responses and decreased T cell activation.

Adolescent↗
PubMed2003

HIV-specific CD8+ T cell function in children with vertically acquired HIV-1 infection is critically influenced by age and the state of the CD4+ T cell compartment.

The immunology of vertical HIV transmission differs from that of adult infection in that the immune system of the infant is not fully matured, and the factors that influence the functionality of CD8(+) T cell responses against HIV in children remain largely undefined. We have investigated CD8(+) T cell responses in 65 pediatric subjects with vertically acquired HIV-1 infection. Vigorous, broad, and Ag dose-driven CD8(+) T cell responses against HIV Ags were frequently observed in children who were older than 3 years of age and maintained CD4(+) T cell counts >400 cells/ micro l. In contrast, younger age or a CD4(+) T cell count <400 cells/ micro l was associated with poor CD8(+) T cell responses and high HIV loads. Furthermore, subjects with a severely depleted and phenotypically altered CD4(+) T cell compartment had circulating Gag-specific CD8(+) T cells with impaired IFN-gamma production. When viral load was not suppressed by antiviral treatment, subjects that fell below the putative age and CD4(+) T cell count thresholds had significantly reduced CD8(+) T cell responses and significantly higher viral loads. Thus, the data suggest that fully effective HIV-specific CD8(+) T cell responses take years to develop despite an abundance of Ag in early life, and responses are further severely impaired, independent of age, in children who have a depleted or skewed CD4(+) T cell compartment. The results are discussed in relation to differences between the neonatal and adult immune systems in the ability to respond to HIV infection.

Adolescent↗
PubMed2003

CD7 is a differentiation marker that identifies multiple CD8 T cell effector subsets.

The adaptive immune response of human CD8 T cells to invading pathogens involves the differentiation of naive cells into memory and effector cells. However, the lineage relationship between memory and effector cells and the differentiation of CD8 T cells into distinct subsets of effector cell subpopulations are subjects of considerable debate. CD7 identifies three populations of CD8 T cells: CD7 high (CD7(high)), low (CD7(low)), and negative (CD7(neg)) that translate into subsets with distinct functional properties. The CD7(high) subset contains naive and memory cells and the CD7(low) and CD7(neg) subsets contain effector cells. The effector cells can functionally be divided into cytokine-secreting effector CD8 T cells and lytic effector CD8 T cells. These data provide a model of human CD8 T cell differentiation in which specialized distinct subpopulations can be identified by expression of CD7.

Antigens, CD7↗
PubMed2003

Dominant effector memory characteristics, capacity for dynamic adaptive expansion, and sex bias in the innate Valpha24 NKT cell compartment.

Valpha24 natural killer T (NKT) cells are innate immune cells that recognize self and nonself glycolipids presented by CD1d molecules, and play immunoregulatory roles in autoimmunity and tumor immunity. We have investigated the circulating Valpha24 NKT cells in a large cohort of human subjects. CCR7(-) CD45RO(+) effector memory cells dominated both CD4(+) and CD4() NKT subsets, while a minority displayed a central memory phenotype. CD4(-) central memory NKT cells, however, were atypical in that they largely lacked CD62L expression. Overall, CD4(-) NKT cells displayed a functional phenotype with effector characteristics, while the CD4(+) subset appeared immunoregulatory. Interestingly, NKT cell numbers in blood varied widely between subjects, and elevated numbers of these cells were much more common in women than in men. The CD4(+) subset dominated the NKT cell compartment in both sexes, while circulating NKT cell numbers above 0.1% were associated with an expanded CD4(-) subset. Although NKT cell numbers were generally stable over time, we describe a dynamic fivefold expansion that was associated with a skewing of the NKT CD4(+):CD4(-) ratio that persisted after numbers returned to base line. Thus, the two NKT cell subsets display different properties and dynamics that will influence their function as innate immunoregulatory and effector cells.

CD4 Antigens↗
PubMed2003

Trafficking of human immunodeficiency virus type 1-specific CD8+ T cells to gut-associated lymphoid tissue during chronic infection.

Gut-associated lymphoid tissue (GALT) is a significant but understudied lymphoid organ, harboring a majority of the body's total lymphocyte population. GALT is also an important portal of entry for human immunodeficiency virus (HIV), a major site of viral replication and CD4(+) T-cell depletion, and a frequent site of AIDS-related opportunistic infections and neoplasms. However, little is known about HIV-specific cell-mediated immune responses in GALT. Using lymphocytes isolated from rectal biopsies, we have determined the frequency and phenotype of HIV-specific CD8(+) T cells in human GALT. GALT CD8(+) T cells were predominantly CD45RO(+) and expressed CXCR4 and CCR5. In 10 clinically stable, chronically infected individuals, the frequency of HIV Gag (SL9)-specific CD8(+) T cells was increased in GALT relative to peripheral blood mononuclear cells by up to 4.6-fold, while that of cytomegalovirus (CMV)-specific CD8(+) T cells was significantly reduced (P = 0.012). Both HIV- and CMV-specific CD8(+) T cells in GALT expressed CCR5, but only HIV-specific CD8(+) T cells expressed alpha E beta 7 integrin, suggesting that mucosal priming may account for their retention in GALT. Chronically infected individuals exhibited striking depletion of GALT CD4(+) T cells expressing CXCR4, CCR5, and alpha E beta 7 integrin, but CD4(+)/CD8(+) T-cell ratios in blood and GALT were similar. The percentage of GALT CD8(+) T cells expressing alpha E beta 7 was significantly decreased in infected individuals, suggesting that HIV infection may perturb lymphocyte retention in GALT. These studies demonstrate the feasibility of using tetramers to assess HIV-specific T cells in GALT and reveal that GALT is the site of an active CD8(+) T-cell response during chronic infection.

Adult↗
PubMed2002

Generation of CD3+CD8low thymocytes in the HIV type 1-infected thymus.

Infection with the HIV type 1 (HIV-1) can result both in depletion of CD4(+) T cells and in the generation of dysfunctional CD8(+) T cells. In HIV-1-infected children, repopulation of the peripheral T cell pool is mediated by the thymus, which is itself susceptible to HIV-1 infection. Previous work has shown that MHC class I (MHC I) molecules are strongly up-regulated as result of IFN-alpha secretion in the HIV-1-infected thymus. We demonstrate in this study that increased MHC I up-regulation on thymic epithelial cells and double-positive CD3(-/int)CD4(+)CD8(+) thymocytes correlates with the generation of mature single-positive CD4(-)CD8(+) thymocytes that have low expression of CD8. Treatment of HIV-1-infected thymus with highly active antiretroviral therapy normalizes MHC I expression and surface CD8 expression on such CD4(-)CD8(+) thymocytes. In pediatric patients with possible HIV-1 infection of the thymus, a low CD3 percentage in the peripheral circulation is also associated with a CD8(low) phenotype on circulating CD3(+)CD8(+) T cells. Furthermore, CD8(low) peripheral T cells from these HIV-1(+) pediatric patients are less responsive to stimulation by Ags from CMV. These data indicate that IFN-alpha-mediated MHC I up-regulation on thymic epithelial cells may lead to high avidity interactions with developing double-positive thymocytes and drive the selection of dysfunctional CD3(+)CD8(low) T cells. We suggest that this HIV-1-initiated selection process may contribute to the generation of dysfunctional CD8(+) T cells in HIV-1-infected patients.

CD3 Complex↗
PubMed2002

A structural basis for LCMV immune evasion: subversion of H-2D(b) and H-2K(b) presentation of gp33 revealed by comparative crystal structure.Analyses.

LCMV infection of H-2(b) mice generates a CD8(+) CTL response mainly directed toward three immunodominant epitopes. One of these, gp33, is presented by both H-2D(b) and H-2K(b) MHC class I molecules. The virus can escape immune recognition in the context of both these MHC class I molecules through single mutations of the peptide. In order to understand the underlying structural mechanism, we determined the crystal structures of both complexes. The structures reveal that the peptide is presented in two diametrically opposed manners by H-2D(b) and H-2K(b), with residues used as anchor positions in one MHC class I molecule interacting with the TCR in the other. Importantly, the peptide's N-terminal residue p1K protrudes from the binding cleft in H-2K(b). We present structural evidence that explains the functional consequences of single mutations found in escape variants.

Animals↗