T lymphocyte anergy during acute infectious mononucleosis is restricted to the clonotypic receptor activation pathway

Limited Utility of Serology and Heterophile Test in the Early Diagnosis of Epstein–Barr Virus Mononucleosis in a Child after Renal Transplantation

Background: Epstein–Barr virus (EBV) infection is associated with significant morbidity and mortality in renal transplant (RT) recipients. The spectrum of illness ranges from infectious mononucleosis (IM) to post-transplant lymphoproliferative disorder (PTLD). In association with clinical signs and symptoms, virus-specific serology and heterophile antibody tests are widely used in confirming the diagnosis of IM in the general population. However, these tests may have a limited role in immunosuppressed RT recipients from seropositive donor, especially in children who were EBV-seronegative prior to the transplant. The aim of this study is to evaluate the utility of these tests in the early diagnosis of IM in this subset of patients. Methods: This is a case study with a review of literature. Results: Here, we present a 14-year-old male with hemophilia B who presented with fever, fatigue, sore throat, palatal petechial rash, exudative tonsillitis and cervical lymphadenopathy 3 months post-RT. He was EBV seronegative prior to RT and received a deceased donor kidney transplant from a seropositive donor. Induction was done with Thymoglobulin and maintenance immunosuppression consisted of tacrolimus and mycophenolate. Initial heterophile antibody test (monospot) was negative, but became positive at 5 months and remained positive at 9 months follow-up post-RT. EBV viral capsid antigens (VCA) IgM and IgG, early antigen (EA) and nuclear antigen (EBNA) were all negative at the time of presentation. VCA IgM and IgG both became positive at 5 months and peaked at 9 months follow-up, however the EA and EBNA remained negative. EBV viral load as measured by polymerase chain reaction (PCR) was negative for the first 3 months post-RT but became positive at presentation, peaked at 6 months and started declining thereafter. Peripheral blood smear examination showed no absolute and atypical lymphocytosis. Cytomegalovirus PCR in the blood and throat culture for streptococcus were negative. There was no splenomegaly. He was managed conservatively with intravenous fluids, bed rest, antipyretics and reduction of immunosuppression. Conclusions: EBV serological markers have a limited role in the early diagnosis of EBV-IM following RT in prior seronegative children. Initial heterophile antibody test may also be negative, and hence a repeat test may be necessary. Once becoming positive, the VCA IgM may remain persistently elevated for prolonged duration. In addition to the suppressed cellular immunity secondary to immunosuppression, humoral response to viral infections is also delayed in transplant recipients, especially in the early transplant period. Hence, routine monitoring with PCR is superior to serology in diagnosing IM early and monitoring the EBV infection post-RT for timely evaluation and management.

T cell receptor signaling pathway is overexpressed in CD4(+) T cells from HAM/TSP individuals

Human T-lymphotropic virus type 1 (HTLV-1) is a human retrovirus related to the chronic neuroinflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). CD4⁺ T cells activation appears to play a key role on HTLV-1 infection. Here we investigated the expression of genes associated to T cell activation CD3e molecule, epsilon (CD3ɛ), lymphocyte-specific protein tyrosine kinase (LCK), vav 1 guanine nucleotide exchange factor (VAV1), and zeta-chain (TCR) associated protein kinase 70 kDa (ZAP70) on T lymphocytes of HTLV-1-infected individuals and compared to healthy uninfected individuals (CT). We observed that CD3ɛ, LCK, ZAP70, and VAV1 gene expression were increased in CD4⁺ T cells from HAM/TSP group compared to HTLV-1 asymptomatic patients (HAC). Moreover, ZAP70 and VAV1 were also upregulated in HAM/TSP compared to CT group. We detected a positive correlation among all these genes. We also observed that CD3ɛ, LCK, and VAV1 genes had a positive correlation with the proviral load (PVL) and Tax expression. These results suggest that PVL and Tax protein could drive CD3ɛ, LCK, and VAV1 gene expression in CD4⁺ T cells, and these genes function on a synchronized way on the CD4⁺ T cell activation. The elucidation of the mechanisms underlying T cell receptor signaling pathway is of considerable interest and might lead to new insights into the mechanism of HAM/TSP.

Clinical significance of variations in levels of Epstein-Barr Virus (EBV) antigen and adaptive immune response during chronic active EBV infection in children

Pediatric patients were recruited to analyze differences in Epstein-Barr virus (EBV) copy numbers and adaptive immune reactions in children with chronic active vs acute EBV infection (CAEBVI vs AEBVI), as well as to examine the relationship between these parameters and the pathogenesis of CAEBVI. Fluorescent qPCR was used to assess EBV-DNA levels, while ELISA, antibody affinity, flow cytometry, and heterophil agglutination (HA) assays were used to evaluate patient EBV-adaptive humoral and cellular immunity. Lastly, ELISPOT was employed to assess interferon (IFN)-γ secretory functions of EBV-specific cytotoxic T-lymphocytes (CTL) as a marker of subject EBV-specific adaptive cellular immunity. The results indicated that, compared with AEBVI patients or normal children, there was a dramatic elevation in viral copy levels, viral capsid antigen (VCA)-IgA, early antigen (EA)-IgA, and EA-IgG, but a lack of EBV nuclear antigen (EBNA)-IgG and a negative HA in CAEBVI patients (p < 0.01). These subjects also had decreased CD4(+), CD8(+) (naïve), CD8(+)CD38(+), and effective memory T-lymphocyte levels compared with AEBVI patients (p < 0.01), and decreased EBV-specific CTL function compared with normal children (p < 0.01). These results suggest that there is a disturbance in EBV antigen availability and in both the adaptive humoral and cellular immune responses in patients with CAEBVI, and that these outcomes may be associated with the chronic active re-infection process itself associated with CAEBVI.

The lymph node in HIV pathogenesis

Since the earliest days of the AIDS epidemic, clinicians and researchers have recognized the importance of lymphoid tissue both in the clinical manifestations of disease and in its pathogenesis. Generalized lymphadenopathy was one of the earliest harbingers of AIDS in the United States and over the past 27 years an increasing body of evidence has implicated the lymphoid organs as central to the pathogenesis of immune deficiency in chronic HIV-1 infection. In this essay, we will review some of the data that have been accumulated and propose a testable model that may reconcile them.

Use of granulocyte-macrophage colony-stimulating factor to reverse anergy in otherwise immunologically healthy children

BACKGROUND

T-cell anergy, as measured by delayed hypersensitivity skin testing, is associated with increased susceptibility to infection. Because the repertoire of effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) includes enhancement of antigen processing and presentation by antigen-presenting cells, GM-CSF has been used to augment immune function in human immunodeficiency virus-induced and other viral illness-induced immune dysfunction and to affect positively immune function in a wide variety of disorders.

OBJECTIVE

To attempt reversal of T-cell anergy using GM-CSF in 3 otherwise immunologically healthy children with severe recurrent and persistent viral respiratory tract infections and in one child with recurrent bacterial sepsis.

METHODS

After written informed consent and baseline data were obtained, the study participants were administered 3 two-week cycles of GM-CSF. Delayed hypersensitivity skin testing and laboratory tests were repeated 2 weeks after the third cycle and subsequently as clinically indicated.

RESULTS

All 4 children developed delayed hypersensitivity by skin testing, and all demonstrated markedly decreased number and severity of infection. Improvement persisted in all patients for at least 1 year. A single cycle of additional treatment in 2 patients reestablished delayed hypersensitivity and decreased infection, both of which persisted throughout the follow-up period of 4 or more years.

CONCLUSIONS

GM-CSF treatment reversed T-cell anergy in 4 children. Reestablishment of delayed hypersensitivity was associated with a significant decrease in infection. Although further studies will be needed, use of GM-CSF should be considered as an immune modulator in patients with T-cell anergy and recurrent infections.

Primary human herpesvirus 8 infection generates a broadly specific CD8(+) T-cell response to viral lytic cycle proteins

Human herpesvirus 8 (HHV-8) is a recently discovered gammaherpesvirus that is the etiologic agent of Kaposi sarcoma (KS). The natural history of primary HHV-8 infection, including clinical outcome and host immune responses that may be important in preventing disease related to HHV-8, has not been elucidated. The present study characterized the clinical, immunologic, and virologic parameters of primary HHV-8 infection in 5 cases detected during a 15-year longitudinal study of 108 human immunodeficiency virus type 1 seronegative men in the Multicenter AIDS Cohort Study. Primary HHV-8 infection was associated with mild, nonspecific signs and symptoms of diarrhea, fatigue, localized rash, and lymphadenopathy. There were no alterations in numbers of CD4(+) or CD8(+) T cells or CD8(+) T-cell interferon gamma (IFN-gamma) production to mitogen or nominal antigen. CD8(+) cytotoxic T-lymphocyte precursor (CTLp) and IFN-gamma reactivity were detected during primary HHV-8 infection, with broad specificity to 5 lytic cycle proteins of HHV-8 encoded by open reading frame 8 (ORF 8; glycoprotein B homolog of Epstein-Barr virus), ORF 22 (gH homolog), ORF 25 (major capsid protein homolog), ORF 26 (a minor capsid protein homolog), or ORF 57 (an early protein homolog), in association with increases in serum antibody titers and appearance of HHV-8 DNA in blood mononuclear cells. CD8(+) T-cell responses to HHV-8 decreased by 2 to 3 years after primary infection. This antiviral T-cell response may control initial HHV-8 infection and prevent development of disease.

Glycidol modulation of the immune responses in female B6C3F1 mice

The immunotoxic potential of glycidol was evaluated in female B6C3F1 mice using a battery of functional assays and three host resistance models. Glycidol was administered to the animals by oral gavage as a solution in sterile distilled water daily for 14 days at doses of 25, 125 and 250 mg/kg. In tier I, we observed that glycidol exposure produced a dose-related decrease in splenocyte IgM antibody-forming cell response to sheep red blood cells (sRBC); the spleen natural killer (NK) cell activity was also decreased. A decrease in B cell proliferative responses to anti-IgM F(ab')2 and/or interleukin-4 (IL-4) was observed while the splenocyte proliferative responses to T cell mitogen ConA and B cell mitogen LPS were not affected. The splenocyte proliferative response to allogeneic cells as evaluated in the mixed leukocyte reaction (MLR) to DBA/2 spleen cells was not affected. In tier II, we found that exposure to glycidol decreased the number and percentage of B cells and the absolute number of CD4+ T cells in the spleen while the number of total T cells, CD8+ T cells and CD4+CD8+ T cells was not affected. The cytotoxic T lymphocyte (CTL) response to mitomycin C-treated P815 mastocytoma was not affected; the cytotoxic activity of peritoneal macrophages was not suppressed. Moreover, the host resistance to Listeria monocytogenes was not affected although a slight increase in host resistance to Streptococcus pneumoniae was observed. However, exposure to glycidol decreased host resistance to the B16F10 melanoma tumor model with the maximal tumor formation in lung observed in the high dose group. Overall, these dada support the finding that glycidol is an immunosuppressive agent in female B6C3F1 mice.

Inactivation of NF-κB by EBV BZLF-1-Encoded ZEBRA Protein in Human T Cells

We have previously shown that the EBV ZEBRA protein (also denoted EB1, Z, or Zta) encoded by the BZLF open reading frame is expressed in primary human thymocytes and in human T lymphoblastoid cell lines infected by EBV. Expression of EBV-encoded gene products in T lymphocytes could contribute to viral pathogenesis during acute EBV infection as well as in individuals coinfected with EBV and HIV. HPB-ALL and Jurkat T lymphoblastoid cell lines transiently and stably expressing ZEBRA were characterized in this work. Expression of ZEBRA protein in human T lymphoblastoid cells was associated with decreased expression of an NF-κB reporter gene, altered expression of the NF-κB p50 protein subunit, and decreased DNA binding by components of NF-κB. These observations suggest that inactivation of NF-κB transcription by ZEBRA in EBV-infected T cells may be a novel mechanism of viral pathogenesis analogous in part to over-expression of the endogenous cytoplasmic inhibitor of NF-κB, IκBα.

Epstein-Barr Virus Induces Fas (CD95) in T Cells and Fas Ligand in B Cells Leading to T-Cell Apoptosis

Epstein-Barr virus (EBV) acute infectious mononucleosis (AIM) is characterized by transient immunosuppression in vivo and increased T-cell apoptosis after ex vivo culture of AIM peripheral blood mononuclear cells. We undertook experiments to test whether EBV or purified virion envelope glycoprotein gp350 could contribute to Fas-mediated T-cell apoptosis. Our in vitro results indicate that EBV increased Fas expression in CD4+ T cells and Fas ligand (FasL) expression in B cells and macrophages. Purified gp350 was also shown to significantly increase CD95 expression in CD4+ T cells. When T-cell CD95 was cross-linked, EBV-stimulated T cells underwent apoptosis. The induction of T-cell CD95 by EBV followed by CD95 cross-linking with anti-CD95 monoclonal antibody resulted in a loss in the number of T cells responding to the T-cell mitogens, anti-CD3 antibody, and interleukin-2. These results indicate that, in addition to serving as a principal ligand for the attachment of virus to target cells, gp350 may also act as an immunomodulatory molecule that promotes T-cell apoptosis.

Suppressor macrophages mediate depressed lymphoproliferation in chickens infected with avian reovirus

A previous study indicated that spleens from reovirus-infected chickens contained macrophages that were primed to produce nitric oxide (NO). The presence of these primed macrophages correlated with depressed in vitro T cell mitogenesis. The current studies indicated that splenic adherent macrophages from virus-exposed chickens inhibited concanavalin A (ConA) induced proliferation of normal spleen cells. ConA-stimulated spleen cells from uninfected chickens, but not virus-exposed chickens, produced large quantities of interleukin-2 (IL-2) and a factor that induced NO production. This factor was tentatively named NO inducing factor (NOIF). The removal of macrophages from the spleens of virus-exposed chickens by plastic adherence resulted in partial recovery of ConA-induced proliferation and the production of normal levels of IL-2 and increased levels of NOIF, although these remained below normal. However, nonadherent spleen cells produced substantial quantities of NO, which indicated an incomplete removal of macrophages. Because removal by plastic adherence did not result in the depletion of all macrophages, spleen cells were panned with anti-CD3 antibody to obtain an almost pure population of T cells. Fractionated T cells from virus-exposed chickens proliferated vigorously to ConA and produced normal levels of IL-2 and NOIF. When splenic adherent cells from virus-exposed chickens were added to purified T cells, the T cells failed to respond to ConA. Addition of splenic adherent cells from virus-free chickens did not induce mitogenic inhibition. Further, the addition of purified T cells from the spleens of reovirus-infected chickens to T cells from virus-free birds did not adversely affect T cell mitogenesis. These data indicated that reovirus infection in chickens does not compromise the functional capabilities of T cells but induces suppressor macrophages that inhibit T cell functions.

Defective functional response to membrane stimuli in lymphocytes from patients with benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a local disturbance in the prostate that may involve an inflammatory infiltrate predominantly composed of activated lymphocytes and macrophages. The activation and proliferative response of T lymphocytes to different mitogenic signals has been analysed in peripheral blood mononuclear cells (PBMC) from 45 patients with BPH and 55 healthy controls. The PBMC obtained from the patients showed a significant specific impairment in proliferation, CD25 expression and IL-2 production in response to stimulation with lectins (phytohaemagglutinin (PHA), concanavalin A (Con A)), that was not corrected by the addition of IL-2 or of phorbol esters (phorbol myristate acetate (PMA)). Also, the CD28 response was defective in patient PBMC. Activation with anti-CD3 or anti-CD2 MoAbs was normal, but the addition of PMA to these stimuli provoked a significant defective response. Only the use of transmembrane stimuli (PMA and ionomycin) elicited responses similar to those found in the control group. The results indicate that peripheral T lymphocytes from BPH patients show a functional impairment that is mainly explained by an alteration of membrane signals (PHA, CD28) and is distal to protein kinase C (PKC) activation.

Activation of a varicella-zoster virus-specific IgA response during acute Epstein-Barr virus infection

The influence of an acute Epstein-Barr virus (EBV) infection on the serological parameters of persistent varicella-zoster virus (VZV) and herpes simplex virus (HSV) was studied. Sera from 161 patients with infectious mononucleosis caused by EBV and 178 age-matched controls were tested for HSV- and VZV-specific IgA. 98.7 percent of VZV-IgG-positive controls were negative for VZV-IgA, pointing to the stringent control of latent VZV in healthy individuals. During acute EBV infection, 33.8% of VZV-IgG-positive infectious mononucleosis patients produced VZV-specific IgA. This result may be explained either by reactivation of VZV due to transient suppression of cellular immune functions during acute EBV infection or by polyclonal stimulation caused by EBV. Due to the high incidence of HSV-IgA in healthy HSV-IgG-positive individuals, only a marginal effect of acute EBV infection on the appearance of HSV-specific IgA was found.

Epstein-Barr virus, infectious mononucleosis, and posttransplant lymphoproliferative disorders

PTLD may be considered as an "opportunistic cancer" in which the immunodeficiency state of the host plays a key role in fostering the environment necessary for abnormal lymphoproliferation. The following discussion reflects our own current thoughts regarding events which may result in PTLD and its sequelae. Many of the individual steps have not been rigorously proved or disproved at this point in time. Following transplantation and iatrogenic immunosuppression, the host:EBV equilibrium is shifted in favor of the virus. Most seronegative patients will become infected either via the graft or through natural means; seropositive patients will begin to shed higher levels of virus and may become secondarily superinfected via the graft. There is a "grace" period of approximately one month posttransplant before increased viral shedding begins. PTLD is almost never seen during this interval. In many cases infection continues to be silent whereas in rare individuals there is an overwhelming polyclonal proliferation of infected B lymphocytes. This is the parallel of infectious mononucleosis occurring in patients with a congenital defect in virus handling (X-linked lymphoproliferative disorder). It is possible that transplant patients with this presentation also suffer a defect in virus handling. In other cases excessive iatrogenic immunosuppression may paralyze their ability to respond to the infection. With CsA and FK506 regimens, individual tumors may occur within a matter of months following transplant. The short time of incubation suggests that these are less than fully developed malignancies. It may be that local events conspire to allow outgrowth of limited numbers of B-lymphocyte clones. A cytokine environment favoring B-lymphocyte growth may be one factor and differential inhibition by the immuno-suppressive drugs of calcium-dependent and -independent B-cell stimulation may be another. In addition, there is some evidence that CsA itself may inhibit apoptosis within B cells. Since most patients do not develop PTLDs, an additional signal(s) for B-cell stimulation may be required. Indeed, it is possible that the virus may simply serve to lower the threshold for B-cell activation and/or provide a survival advantage to these cells. The ability of individual cell clones to evade a weakened immune system may set into play a Darwinian type of competition in which the most rapidly proliferating cells with the least number of antigenic targets predominate. In this regard, differences in host HLA types may determine the repertoire of viral antigens which are subject to attack.(ABSTRACT TRUNCATED AT 400 WORDS)

Selective impairment of T lymphocyte activation through the T cell receptor/CD3 complex after cytomegalovirus infection

Cytomegalovirus (CMV) infection is reported to cause transient immunosuppression in man. In this study we have analysed the effect of CMV on T lymphocyte function in 29 children diagnosed for acute CMV infection. Peripheral blood mononuclear cells (PBMC) obtained from the patients showed a significant specific impairment in their proliferative response to enterotoxins A and C1, to concanavalin A and to the anti-CD3 MoAb OKT3. The impaired responses were corrected with exogenous IL-2. In contrast, stimulation using phytohaemagglutinin, as well as activation signals delivered through the surface molecules CD26 or CD28, elicited normal proliferative responses in CMV PBMC. The results indicate that the T cell anergy associated with CMV infection is restricted to the T cell receptor/CD3 activation pathway.

Human T-cell activation deficiencies

The increasing understanding of T-cell activation is paralleled by the recognition of a growing range of 'experiments of nature' that cause T-cell activation deficiencies. Analysis of these deficiencies is, in turn, contributing to the understanding of T-cell function in vivo. Here, José Regueiro, Antonio Arnaiz-Villena and colleagues review current knowledge of structural and functional T-cell defects and the implications of these for T-cell biology.