A positive correlation between the precursor frequency of cytotoxic lymphocytes to autologous Epstein-Barr virus-transformed B cells and antibody titer level against Epstein-Barr virus-associated nuclear antigen in healthy seropositive individuals

The impact of environmental infections (parasites) on MS activity

MS incidence has significantly increased during the second half of the 20th century, generating considerable interest in analyzing the basis for this rise in the developed world. Particular emphasis is being placed on the role infections might play in exacerbating or preventing disease onset. Epidemiological data suggest that improvement in sanitation conditions and reduced exposure to infection might explain, at least in part, these changes. The hygiene hypothesis is not new and is currently used to explain the increasing incidence of allergies and other autoimmune diseases. Because helminths are powerful modulators of host immunity, some authors hypothesize that reduced parasite exposure due to improved hygiene conditions may favor MS development. We discuss epidemiological, experimental, clinical and molecular data supporting the protective role of helminthes against MS. Better understanding of host–parasite interactions caused by specific parasite molecules with immunomodulatory effects will help combat allergies and autoimmune disease without the price of untoward infection as a side-effect.

No evidence for intrathecal IgG synthesis to Epstein Barr virus nuclear antigen-1 in multiple sclerosis

BACKGROUND

Recent studies suggest an intrathecal IgG response against Epstein Barr virus (EBV) in multiple sclerosis (MS), implicating a pathogenic role for the virus in MS.

OBJECTIVES

To determine the spectrum of anti-EBV antibodies and B-cell epitopes within EBV nuclear antigen-1 (EBNA-1). Furthermore, to determine whether EBNA-1-specific IgG is produced intrathecally.

STUDY DESIGN

Immunoblot analysis was used to study the anti-EBV IgG response in serum and cerebral spinal fluid (CSF) in MS and controls. EBNA-1 B-cell epitopes were identified by immunoscreening of 12 residue long peptides, with 11 residue overlap, spanning EBNA-1. Thirteen peptides containing all immunoreactive regions were constructed and used in paired serum and CSF of MS patients (n=17) and controls (n=18). Subsequently, reactivity to the identified immunodominant peptide was analysed in a large cohort of serum and CSF of MS patients (n=114) and disease controls (n=62).

RESULTS

No difference was observed in the overall anti-EBV antibody diversity, but EBNA-1 reactivity was increased in MS patients versus controls for immunoblot and ELISA (p<0.0001). Epitope analysis on EBNA-1 revealed one immunodominant region covering residues 394-451: EBNA-1(394-451). Anti-EBNA-1(394-451) IgG levels in serum and CSF were significantly higher in MS patients compared to controls. However, normalization for total IgG content of paired serum and CSF samples abrogated this disease association.

CONCLUSIONS

MS patients have normal overall anti-EBV antibody responses with increased reactivity to EBNA-1(394-451). No evidence was found for intrathecal EBNA-1-specific IgG synthesis in MS.

Environmental risk factors in multiple sclerosis

OBJECTIVES

Multiple sclerosis (MS) likely results from an interaction between genetic and exogenous factors. While genetics shapes the overall population MS susceptibility, observed epidemiological patterns strongly suggest a role for the environment in disease initiation and modulation.

RESULTS

Findings from studies on seasonality in MS patients' birth, disease onset and exacerbations, as well as apparent temporal trends in incidence and gender ratio support an influential effect of viruses, metabolic and lifestyle factors on MS risk. Epstein-Barr virus, vitamin D status, and smoking are factors that may explain such epidemiological patterns.

CONCLUSIONS

Further epidemiological investigations are encouraged and opportunities to use data from existing cohort studies as well as the design of new studies should be pursued. In particular, the development of new large multicentre population-based case-control studies which incorporate the study of the role of environment and genetics, including epigenetic mechanisms, in determining MS risk is proposed.

Environmental risk factors for multiple sclerosis. Part II: Noninfectious factors

As discussed in Part I of this review, the geographic distribution of multiple sclerosis (MS) and the change in risk among migrants provide compelling evidence for the existence of strong environmental determinants of MS, where "environmental" is broadly defined to include differences in diet and other behaviors. As we did for infections, we focus here primarily on those factors that may contribute to explain the geographic variations in MS prevalence and the change in risk among migrants. Among these, sunlight exposure emerges as being the most likely candidate. Because the effects of sun exposure may be mediated by vitamin D, we also examine the evidence linking vitamin D intake or status to MS risk. Furthermore, we review the evidence on cigarette smoking, which cannot explain the geographic variations in MS risk, but may contribute to the recently reported increases in the female/male ratio in MS incidence. Other proposed risk factors for MS are mentioned only briefly; although we recognize that some of these might be genuine, evidence is usually sparse and unpersuasive.

Vitamin D status modulates the immune response to Epstein Barr virus: Synergistic effect of risk factors in multiple sclerosis

MS risk is associated with low vitamin D status prior to disease, and Epstein Barr virus (EBV) infection seems to be a prerequisite for MS. EBV could activate autoreactive T cells by several mechanisms, but it is not clear why this leads to MS. Only a small proportion of those infected with EBV develops MS, whereas autoreactive T cells are present in the normal T cell repertoire. Genetic factors cannot explain this enigma alone, because the genetic predisposition to MS in most cases is quite weak. Vitamin D receptors are expressed on EBV infected B cells, antigen presenting cells and activated lymphocytes, and the bioactive vitamin D metabolite dihydroxyvitamin D(3) suppresses antibody production and T cell proliferation and skews T cells towards a less detrimental Th2 phenotype. EBV infected B cells constitute a constant challenge to the immune system, also during seasonal periods of relative low vitamin D status. I propose that vitamin D modulates the immune response to EBV, and that detrimental activation of autoreactive T cells leading to MS is more likely if the vitamin D status is suboptimal.

Use and specificity of breast cancer antigen/milk protein BA46 for generating anti-self-cytotoxic T lymphocytes by recombinant adeno-associated virus-based gene loading of dendritic cells

Antigen-targeted immunotherapy is an emerging treatment for breast cancer. However, useful breast cancer antigens are only found in a subset of cancer patients. BA46, also known as lactadherin, is a membrane-associated glycoprotein that is expressed in most breast cancer cells but not in general hematopoietic cell populations. Moreover, it is much more difficult to generate CTLs against self-antigens. We wished to determine if the use of recombinant adeno-associated virus (rAAV) type 2 vectors for gene-loading of dendritic cells (DCs) could generate rapid, effective cytotoxic T lymphocytes (CTLs) against BA46. We were able to demonstrate that AAV/BA46/Neo-loading of DCs resulted in: (1) BA46 expression in DCs, (2) chromosomal integration of the AAV/BA46/Neo vector within DCs, (3) strong, rapid BA46-specific, MHC class I-restricted CTLs in only 1 week, (4) T-cell populations with significant interferon-gamma (IFN-gamma) expression but low IL-4 expression, (5) high CD80 and CD86 expression in DCs, and (6) high CD8:CD4 and CD8:CD56 T cell ratios. These data suggest that rAAV-loading of DCs may be useful for immunotherapeutic protocols against self-antigens in addition to viral antigens and that the BA46 antigen is potentially appropriate for cell-mediated immunotherapeutic protocols addressing ductal breast cancer.

Elevated stress hormone levels relate to Epstein-Barr virus reactivation in astronauts

OBJECTIVE

The objective of this study was to determine the effects of stress and spaceflight on levels of neuroendocrine hormones and Epstein-Barr virus (EBV)-specific antibodies in astronauts.

METHODS

Antiviral antibody titers and stress hormones were measured in plasma samples collected from 28 astronauts at their annual medical exam (baseline), 10 days before launch (L-10), landing day (R+0), and 3 days after landing (R+3). Urinary stress hormones were also measured at L-10 and R+0.

RESULTS

Significant increases (p <.01) in EBV virus capsid antigen antibodies were found at all three time points (L-10, R+0, and R+3) as compared with baseline samples. Anti-EBV nuclear antigen antibodies were significantly decreased at L-10 (p <.05) and continued to decrease after spaceflight (R+0 and R+3, p <.01). No changes were found in antibodies to the nonlatent measles virus. The 11 astronauts who showed evidence of EBV reactivation had significant increases in urinary epinephrine and norepinephrine as compared with astronauts without EBV reactivation.

CONCLUSION

These findings indicate that physical and psychological stresses associated with spaceflight resulted in decreased virus-specific T-cell immunity and reactivation of EBV.

Possible role of natural killer cells in negative selection of mutant lymphocytes that fail to express the human leukocyte antigen-A2 allele

Increased frequencies of cells carrying mutations at several loci have been found in the blood cells of atomic-bomb (A-bomb) survivors upon testing four or five decades after the bombing. Interestingly, though, we have been unable to demonstrate any radiation-associated increases in the frequencies of mutant blood cells in which human leukocyte antigen (HLA)-A expression has been disrupted; this is true both of preliminary tests on the T cells of a small subset of A-bomb survivors and of the much more extensive study reported here in which we screened a much larger group of survivors for HLA-A2 loss mutations in B cells and granulocytes as well as in T cells. In attempting to explain our inability to detect any increases in HLA-A2-negative cell numbers in HLA-A2 heterozygous individuals exposed to A-bomb irradiation, we decided to test the hypothesis that HLA-A mutant lymphocytes might well have been induced by radiation exposure in much the same way as every other type of mutant we encountered, but may subsequently have been eliminated by the strong negative selection associated with their almost inevitable exposure to autologous natural killer (NK) cells in the bloodstream of each of the individuals concerned. We now report that mutant B lymphocyte cell lines that have lost the ability to express the HLA-A2 antigen do indeed appear to be much more readily eliminated than their parental heterozygous counterparts during co-culture in vitro with autologous NK cells. We make this claim first because we have observed that adding autologous NK cells to in vitro cultures of HLA-A2 heterozygous B or T cell lines appeared to cause a dose-dependent decrease in the numbers of HLA-A2-negative mutants that could be detected over a period of 3 days, and second because when we used peripheral blood HLA-A2 heterozygous lymphocyte cultures from which most of the autologous NK cells had been removed we found that we were able to detect newly-arising HLA-A2 mutant T cells in substantial numbers. Taken together, these results strongly support the hypothesis that autologous NK cells are responsible for eliminating mutant lymphocytes that have lost the ability to express self-HLA class I molecules in vivo, and may well therefore explain why we have been unable to detect increased frequencies of HLA-A2 mutants in samples from any of the 164 A-bomb survivors whose HLA-A2 heterozygote status made their lymphocytes suitable for our tests.

T-cell responses to mitogens in atomic bomb survivors: a decreased capacity to produce interleukin 2 characterizes the T cells of heavily irradiated individuals

Significant decreases in the fraction of lymphocytes that are CD4(+) and increases in serum levels of some classes of immunoglobulin have been reported to occur in atomic bomb (A-bomb) survivors and in victims of the Chernobyl nuclear plant accident. To investigate the long-term effects of nuclear radiation on cellular immunity in more detail, we used limiting dilution assays with peripheral blood mononuclear cell preparations to analyze the T-cell responses of 251 A-bomb survivors exposed to less than 0.005 Gy and 159 survivors exposed to more than 1.5 Gy. The percentages of CD2-positive cells that were capable of proliferating in response to phytohemagglutinin (PHA) in the presence of exogenous interleukin 2 (IL2) did not differ substantially between distally exposed and more heavily exposed survivors. The heavily exposed survivors appeared to possess fewer T cells that were capable of proliferating in response to concanavalin A (Con A) or of producing interleukin 2. Assuming that CD4 T cells were the ones primarily responsible for producing IL2 in response to Con A, we were able to estimate how many cells in any given CD4 T-cell population were actually producing IL2. The results indicated that peripheral blood samples from heavily exposed survivors contained significantly fewer IL2-producing CD4 T cells than did similar samples from distally exposed survivors, indicating that significant exposure to A-bomb radiation may have a long-lasting negative effect on the capacity of CD4 T-cell populations to produce IL2.

Biology and adoptive cell therapy of Epstein-Barr virus-associated lymphoproliferative disorders in recipients of marrow allografts

Epstein-Barr virus (EBV) is an ubiquitous herpesvirus which is carried as a latent infection of B lymphocytes and salivary gland epithelial cells in over 90% of normal adults. Latently infected EBV-transformed B cells circulate at low frequency in the blood for the life of the host. These transformed B cells stimulate a heterogeneous and complex host cell response, ultimately leading to the development and maintenance of high frequencies of HLA-restricted T cells specific for the EBV-encoded nuclear antigens EBNA2-EBNA6 and the latency membrane proteins LMP-1 and LMP-2. Responses to latent EBV-encoded proteins are hierarchical with responses to certain epitopes predominating, dependent upon the HLA genotype of the host. Profound suppression of T-cell immunity may permit the emergence of polyclonal, oligoclonal or monoclonal EBV antigen-expressing lymphoproliferative disorders or malignant B-cell lymphomas expressing these latent EBV antigens. Adoptive transfer of small numbers of peripheral blood mononuclear cells or HLA-partially matched T cells from in vitro expanded EBV-specific T-cell lines derived from a seropositive marrow donor has induced durable regressions of bulky, widely metastatic monoclonal EBV lymphomas in a high proportion of cases. This review describes the current state of knowledge and hypothesis regarding the biology and immunology of EBV infection in the normal host, the features of donor, host and virus which contribute to the development of EBV-associated lymphoproliferative diseases and the mechanisms whereby they are controlled by adoptive transfer of immune T cells.

Late effects of radiation on the human immune system: an overview of immune response among the atomic-bomb survivors

The studies of the late effects of atomic-bomb (A-bomb) radiation on the immune system were started about 20 years after the bombings in 1945. The most remarkable late effects of radiation are the functional and quantitative abnormalities of T and B cells in survivors exposed to high doses (> or = 1.0 Gy). Abnormalities of T-cell immunity include (1) a decreased proportion of CD3+ T cells in peripheral blood lymphocytes, particularly the proportion of CD4+ CD45RA+ naive T cells (study period 1987-91); (2) an increased frequency of CD4- and CD8- (double negative) alpha beta + T cells (1987-91); and (3) functional defects in T-cell responses to mitogens and alloantigens (1974-85). B-cell abnormalities include: (1) a significant increase in the proportion of B cells among peripheral lymphocytes (1987-91); (2) an increase in serum immunoglobulin A levels in females and immunoglobulin M and the incidence of rheumatoid factor in both sexes (1987-89); and (3) an increased level of anti-Epstein-Barr virus antibody titer (1987-90). In contrast, suggestive (0.05 < p < 0.1) or not significant (p > 0.1) dose effects were observed for the number and function of natural killer cells (1983-91), and benign monoclonal gammopathy (1979-87). In addition, studies initiated sooner after the bombing such as the incidence of autoimmune diseases (1958-87), systemic bacterial infections (1954-67), and granulocyte functions (1947-79) also show little dose-effects. Thus, A-bomb radiation induced the alteration of the balance/interaction between the T- and B-cell subsets--specifically, a decrease in the T-cell population and an increase in the B-cell population in the periphery.

EBV gene expression, EBNA antibody responses and EBV+ peripheral blood lymphocytes in post-transplant lymphoproliferative disease

Epstein-Barr virus (EBV) is associated with the development of several B cell malignancies including Burkitt's lymphoma (BL), post-transplant lymphoproliferative disease (PTLD), and AIDS-related lymphomas. The latter two diseases result from EBV-driven B cell proliferation in the absence of normal immunosurveillance and as such, represent a heterogenous family of lymphoproliferative disorders. This article reviews studies on EBV gene expression and antibody development in PTLD and introduces recent information on the levels of EBV+ peripheral blood lymphocytes to discuss possible mechanisms of pathogenesis under varying conditions of immunosuppression.

Frequent occurrence of in vivo clonal expansion of CD4- CD8- T cells bearing T cell receptor alpha beta chains in adult humans

We have previously reported 2 cases of healthy men showing in vivo monoclonal expansion of mature CD4- CD8- alpha beta T cells. In the present study, an additional 3 adults were found to exhibit such an expansion, among a total 464 adult donors studied. These 5 individuals were otherwise physiologically normal, with no history of severe illness and autoimmune disease at the time of examination. To investigate the mechanisms of the clonal expansion, further characterization of the clonal cells was attempted. No apparent preference for usage of the T cell receptor beta chain variable region was observed in the clonal T cells. These clonal T cells showed lectin-dependent or redirected antibody-dependent cell-mediated cytotoxicities, whereas they could not lyse autologous lymphoblastoid cell lines. Failure of Fas antigen expression was not observed for any of these clones. These results suggest that clonal expansion of CD4- CD8- alpha beta T cells frequently occurs in the periphery without any T cell abnormalities.