Acute Phase Of Infectious Mononucleosis Research Articles

Infection of Epstein-Barr virus in children in NortheasternPoland

<br><b>Introduction:</b> Infectious mononucleosis is an acute, mild infection occurring mainly in childrenand adolescents. A characteristic feature is the presence of a symptomatic which includedfever, cervical or generalized lymphadenopathy, tonsillitis, coryzam and characteristic whitecoating on the surface. Laboratory tests show changes in the amount of leukocytes and theappearance of virocytes in peripheral blood as well as an increase in liver enzymes. The virusmainly infects epithelial cells and B lymphocytes. In B lymphocytes it intensively multiplies,leading to their transformation into plasma cells and, as a result, the production of specificIgM class antibodies. The produced antibodies activate T lymphocytes (CD8+). During theinfection, the humoral response is also activated. It works by producing antibodies directedagainst early antigen (EA), nuclear antigen (EBNA) and capsid antigen (VCA).</br><br><b>Aim:</b> The objective of the current study was to assess the occurrence of IgM and IgG antibodiesagainst the Epstein-Barr virus in children hospitalized in the Podlaskie Voivodeship.</br><br><b>Material and methods:</b> The levels of antibody were determined in serum patients serum usingthe ELFA method (Enyzme Liked Fluorescent Assay) using the VIDAS analyzer.</br><br><b>Results:</b> Based on preliminary studies, it shown that children aged 4-10 and 15-18 are the mostvulnerable group. The analysis of the conducted studies also showed that the acute phase ofinfectious mononucleosis is more often observed in female children.</br><br><b>Conclusions:</b> In order to better illustrate the seroepidemiological status of EBV infection,similar analysis should be performed in children all over Poland. In order to precisely identifythe target age group of children for possible vaccination, these studies should be extended.</br>

Study of surface activation markers on CD3- CD16+ NK cells and their correlation with clinical manifestations in children with infectious mononucleosis.

This study aimed to investigate the proportion of surface activation markers on natural killer (NK) cells in children with infectious mononucleosis (IM) and to explore its clinical relevance. A total of 17 children hospitalized with IM were included in this study as the experimental group. Meanwhile, healthy children matched for age and gender served as controls. First, we isolated peripheral blood mononuclear cells from children with IM and healthy children. Then, NK cell surface markers were stained with monoclonal antibodies and analyzed by flow cytometry. The results showed that the percentage of CD3- CD16+ NK cells was higher in peripheral blood lymphocytes from children with IM than that from healthy children (t = -4.52, P < 0.05). And the expression of the surface activation markers CD69 and CD25 on CD3- CD16+ NK cells was also higher in children with IM (t = -7.729, P < 0.05; t = -5.068, P < 0.05). There was a positive correlation between the percentage of CD3- CD16+ NK cells in peripheral blood and the duration of fever in children with IM (r = 0.530, P < 0.05). Therefore, the proportion of NK cell subsets in children's peripheral blood changes in the acute phase of IM, suggesting that NK cells enhance their cytotoxicity and play a role in the control of infection in children with IM. Higher levels of CD3- CD16+ NK cells and the association with disease progression suggest that these cells might be a useful index to help evaluate the disease course.

A 2D COS study of lymphocytes in the course of infectious mononucleosis

Activation of lymphocytes during contact with the Epstein–Barr virus (EBV) was studied. The lymphocytes were obtained from patients treated due to the acute phase of infectious mononucleosis in the Jagiellonian University Hospital in Krakow. The changes in the averaged Raman spectra of the lymphocytes during their treatment, on the 1st, 3rd, 5th, 9th and 12th day of hospitalization, were analyzed using the 2D-COS method. The most interesting activation marker was the Raman band at 520 cm−1 attributed to the formation of immunoglobulins. This band does not occur in the control group samples. The 2D-COS analysis revealed some additional details of lymphocyte activation. In the 2D synchronous maps, the greatest changes occur for auto-peaks at 2929 cm−1, due to the CH vibrations in the methyl groups of lipids and proteins, at 1638 cm−1, corresponding to the changes in α -helix amide I, 1585 cm−1 corresponding to nucleic acids and some amino acids, Trp, Phe and Gln, indicating cell remodeling. 2D synchronous maps monitor the formation of a receptor complex, as a subsequent functional lymphocyte maturation. 2D asynchronous maps point to the B-cell development towards immune response, i.e., the formation of immunoglobulins.

Subclinical Epstein-Barr Virus Primary Infection and Lytic Reactivation Induce Thyrotropin Receptor Autoantibodies.

Epstein-Barr virus (EBV) is a herpes virus that mainly infects in B lymphocytes and occasionally reactivates lytically. Most individuals have been infected with EBV primarily in their childhood with no symptoms, and the virus persists latently for life. We have previously reported that EBV-infected B cells with thyrotropin receptor autoantibodies (TRAbs) on their surface [TRAb(+) EBV(+) cells] were present in the peripheral blood mononuclear cells (PBMCs) of healthy adult controls and patients with Graves' disease, and that TRAbs released in the culture medium of PBMCs containing TRAb(+) EBV(+) cells by EBV reactivation. EBV lytic reactivation induced the differentiation of host B cells into plasma cells and antibody production. Various autoantibodies have been detected during the acute phase of infectious mononucleosis (IM) that is the symptomatic primary infection of EBV. Therefore, the autoantibody production may be induced by the asymptomatic primary infection. In this study, we examined the presence of TRAb(+) cells, EBV(+) cells, and TRAb(+) EBV(+) cells in PBMCs from 29 healthy or subclinical children without Graves' disease and one cord blood that were divided into six age groups, and also measured plasma TRAb levels. The results obtained demonstrated that low levels of TRAb production occurred with EBV primary infection and lytic reactivation in children without symptoms of IM. Furthermore, the populations of TRAb(+) cells, EBV(+) cells, and TRAb(+) EBV(+) cells were small in the period of primary infection, but they potentially expand with repeated EBV lytic reactivation. This may partly explain why the onset of Graves' disease often occurs in young adults, but rarely in infancy.

Asymptomatic Primary Infection with Epstein-Barr Virus: Observations on Young Adult Cases.

ABSTRACTEpstein-Barr virus (EBV) is typically acquired asymptomatically in childhood. In contrast, infection later in life often leads to infectious mononucleosis (IM), a febrile illness characterized by anti-EBV IgM antibody positivity, high loads of circulating latently infected B cells, and a marked lymphocytosis caused by hyperexpansion of EBV-specific CD8+ T cells plus a milder expansion of CD56dim NKG2A+ KIR− natural killer (NK) cells. How the two situations compare is unclear due to the paucity of studies on clinically silent infection. Here we describe five prospectively studied patients with asymptomatic infections identified in a seroepidemiologic survey of university entrants. In each case, the key blood sample had high cell-associated viral loads without a marked CD8 lymphocytosis or NK cell disturbance like those seen in patients during the acute phase of IM. Two of the cases with the highest viral loads showed a coincident expansion of activated EBV-specific CD8+ T cells, but overall CD8+ T cell numbers were either unaffected or only mildly increased. Two cases with slightly lower loads, in whom serology suggests the infection may have been caught earlier in the course of infection, also showed no T or NK cell expansion at the time. Interestingly, in another case with a higher viral load, in which T and NK cell responses were undetectable in the primary blood sample in which infection was detected, EBV-specific T cell responses did not appear until several months later, by which time the viral loads in the blood had already fallen. Thus, some patients with asymptomatic primary infections have very high circulating viral loads similar to those in patients during the acute phase of IM and a cell-mediated immune response that is qualitatively similar to that in IM patients but of a lower magnitude. However, other patients may have quite different immune responses that ultimately could reveal novel mechanisms of host control.IMPORTANCE Epstein-Barr virus (EBV) is transmitted orally, replicates in the throat, and then invades the B lymphocyte pool through a growth-transforming latent infection. While primary infection in childhood is usually asymptomatic, delayed infection is associated with infectious mononucleosis (IM), a febrile illness in which patients have high circulating viral loads and an exaggerated virus-induced immune response involving both CD8+ T cells and natural killer (NK) cells. Here we show that in five cases of asymptomatic infection, viral loads in the blood were as high as those in patients during the acute phase of IM, whereas the cell-mediated responses, even when they resembled those in patients during the acute phase of IM in timing and quality, were never as exaggerated. We infer that IM symptoms arise as a consequence not of the virus infection per se but of the hyperactivated immune response. Interestingly, there were idiosyncratic differences among asymptomatic cases in the relationship between the viral load and the response kinetics, emphasizing how much there is still to learn about primary EBV infection.

ROLE OF CD95 AND DR3 RECEPTORS IN NA VE T-LYMPHOCYTES APOPTOSIS IN CHILDREN WITH INFECTIOUS MONONUCLEOSIS DURING CONVALESCENCE

Infectious mononucleosis is a widespread disease caused by certain members of Herpesviridae family. Acute infectious mononucleosis develops predominantly in children and is accompanied by an increase of the number of circulating naive CD4+ and naive CD8+ T-lymphocytes in the peripheral blood. The normalization of immunological parameters is achieved within 4–6 months after recovery and that is an indicator of a proper functioning of the immune system. CD95 and DR3 death receptors are involved in the initiation of apoptosis of naive T-lymphocytes in healthy people and in patients with infectious mononucleosis. The aim of the study was to evaluate the ability of CD95 and DR3 receptors to initiate apoptosis of naive CD4+ and naive CD8+ T-lymphocytes in children with infectious mononucleosis during convalescence. The material for the study was the samples of the peripheral blood of children who previously had infectious mononucleosis. The blood sampling was carried out again after 4–6 months after the disease. At the time of the study, children did not display clinical and laboratory signs of infectious mononucleosis. Same children who were examined earlier in the period of the development of acute infectious mononucleosis, as well as relatively healthy children were used as the comparison groups. Isolation of naive CD4+ and naive CD8+ T-lymphocytes was performed by negative magnetic immunoseparation. For specific stimulation of CD95 and DR3 receptors monoclonal antibodies were used. The level of apoptosis and expression of death receptors were evaluated by flow cytometry. Freshly isolated cells were analyzed, as well as cells cultured with the addition of appropriate monoclonal antibodies. It was shown that the recovery period was accompanied by increased apoptosis of freshly isolated naive CD4+ and naive CD8+ T-lymphocytes compared with the acute phase of infectious mononucleosis. Thus in both populations of naive T-cells showed an increase of CD95+ cells’ susceptibility to apoptosis. CD95 stimulation in the cell culture did not lead to the change in the level of apoptosis of naive CD4+ and naive CD8+ T-lymphocytes. The freshly isolated naive CD4+ and naive CD8+ T-lymphocytes DR3+ cells were resistant to apoptosis, and in the process of cultivating their sensitivity varied depending on the subpopulation belonging. Thus in the culture of naive CD4+ T-lymphocytes DR3 was not involved in the transfer of pro-apoptotic signal. In the culture of naive CD8+ T-lymphocytes DR3+ cells were possible to increase the apoptosis of DR3-negative cells. At the same time the DR3 activation by monoclonal antibodies in the culture caused the death of DR3+ naive CD8+ T-lymphocytes that naturally associated with decreased proapoptotic activity of these cells and resulted in inhibition of apoptosis of total pool of naive CD8+ T-lymphocytes. Thus, the functional ability of CD95 and DR3 receptors to trigger an apoptosis of naive T-lymphocytes in children during convalescence of infectious mononucleosis varied and depended on their belonging to naive CD4+ or naive CD8+ T-lymphocytes.

Clinical and Laboratory Features of Infectious Mononucleosis in Children Depending on the Etiology of the Disease

Study of clinical and laboratory features of infectious mononucleosis (IM) in children depending on the etiological variant of the disease. The study involved 94 children aged 4 months to 15 years old with a diagnosis of «infectious mononucleosis». The study analyzed the etiologic structure of IM, clinical and laboratory features of its individual etiological variants. The findings showed that the most common cause of myocardial infarction in children under the age of 15 years is HHV-6, which is more common as monoinfection (51.06% of the total number of patients with IM), at least — in association with EBV and CMV. IM mixed etiology recorded in 29.79% of cases. The acute phase of infectious mononucleosis, regardless of the etiology of the disease is accompanied by a moderate leukocytosis, accelerated erythrocyte sedimentation rate, an increase in alkaline phosphatase activity. The level of IL-4 in the blood varies depending on the etiology of the disease and is the highest at the infarction caused by EBV. Severity of the clinical picture varies depending on the etiology of the disease. The most pronounced intoxication, lymphoproliferative and hepatolienalis syndromes were identified in children with IM-EBV, IM-HHV-6 and IM mixed etiology (version «EBV + HHV-6»). Determination of etiologic variant of IM is relevant for the diagnosis of disease, prediction of its course and possible complications.

Production of thyrotropin receptor antibodies in acute phase of infectious mononucleosis due to Epstein-Barr virus primary infection: a case report of a child.

Various autoantibodies have been reported to be detected during the progression of infectious mononucleosis. We observed a case of infectious mononucleosis due to Epstein–Barr virus primary infection for 2 months, and noticed the transiently increased titer of thyrotropin receptor autoantibodies detected at the acute phase on the 3rd day after admission. At that time, real-time quantitative PCR also revealed the mRNA expressions of an immediate early lytic gene, BZLF1, and a latent gene, EBNA2. The expression of BZLF1 mRNA means that Epstein–Barr virus infects lytically, and EBNA2 protein has an important role in antibody production as well as the establishment of Epstein–Barr virus latency. These results suggest that Epstein–Barr virus lytic infection is relevant to thyrotropin receptor autoantibody production. Thyrotropin receptor autoantibodies stimulate thyroid follicular cells to produce excessive thyroid hormones and cause Graves’ disease. Recently, we reported the thyrotropin receptor autoantibody production from thyrotropin receptor autoantibody-predisposed Epstein–Barr virus-infected B cells by the induction of Epstein–Barr virus lytic infection in vitro. This case showed in vivo findings consistent with our previous reports, and is important to consider the pathophysiology of Graves’ disease and one of the mechanisms of autoimmunity.

IMMUNOLOGIC INDEXES, ENZYME STATUS OF LYMPHOCYTES AND FUNCTIONAL ACTIVITY OF BLOOD NEUTROPHILS IN CHILDREN WITH INFECTIOUS MONONUCLEOSIS CAUSED BY EPSTEIN–BARR VIRUS

Explore the immunological parameters, levels of activity of NAD(P)-dependent dehydrogenases lymphocytes, interferon status parameters, phagocytic activity and chemiluminescence response of neutrophils in the blood of children in the acute phase of infectious mononucleosis caused by the Epstein-Barr virus. 65 children at the age of 4-6 years old with infectious mononucleosis caused by EBV in acute phase were observed. Such indexes as cell-mediated, humoral and interferon immunity, NAD(P)-depended dehydrogenases activity in blood lymphocyte, phagocytes activity, levels of spontaneous and induced chemiluminescence ofperipheral blood neutrophils were studied. Children with EVB-infection have immunophenotype spectrum changes and changes of enzymes status of blood lymphocytes against the increasing in leucocytes and the useful increasing in lymphocytes. The useful increasing in IgA, IgM, IgG contenting in serum blood were found. The decreasing of spontaneous production of IFN alpha and the decreasing of induced production of IFNalpha, IFNgamma were determined. The breach of phagocytes activity and chemiluminescent response of blood neutrophils were found. The children in the acute phase of infectious mononucleosis caused by the Epstein-Barr virus, there are changes in the immune status, changes the activity of NAD(P)-dependent dehydrogenases in blood lymphocytes, marked changes in functional and metabolic state of peripheral blood neutrophils.

Chronic Fatigue Syndrome After Infectious Mononucleosis in Adolescents

The goal was to characterize prospectively the course and outcome of chronic fatigue syndrome in adolescents during a 2-year period after infectious mononucleosis. A total of 301 adolescents (12-18 years of age) with infectious mononucleosis were identified and screened for nonrecovery 6 months after infectious mononucleosis by using a telephone screening interview. Nonrecovered adolescents underwent a medical evaluation, with follow-up screening 12 and 24 months after infectious mononucleosis. After blind review, final diagnoses of chronic fatigue syndrome at 6, 12, and 24 months were made by using established pediatric criteria. Six, 12, and 24 months after infectious mononucleosis, 13%, 7%, and 4% of adolescents, respectively, met the criteria for chronic fatigue syndrome. Most individuals recovered with time; only 2 adolescents with chronic fatigue syndrome at 24 months seemed to have recovered or had an explanation for chronic fatigue at 12 months but then were reclassified as having chronic fatigue syndrome at 24 months. All 13 adolescents with chronic fatigue syndrome 24 months after infectious mononucleosis were female and, on average, they reported greater fatigue severity at 12 months. Reported use of steroid therapy during the acute phase of infectious mononucleosis did not increase the risk of developing chronic fatigue syndrome. Infectious mononucleosis may be a risk factor for chronic fatigue syndrome in adolescents. Female gender and greater fatigue severity, but not reported steroid use during the acute illness, were associated with the development of chronic fatigue syndrome in adolescents. Additional research is needed to determine other predictors of persistent fatigue after infectious mononucleosis.

Absence of Epstein-Barr virus-specific, HLA class II-restricted CD4+ cytotoxic T lymphocytes in infectious mononucleosis

Cytotoxic T lymphocytes (CTL) with the CD4+ phenotype that recognize major histocompatibility complex (MHC) class II antigens are detectable very frequently in cultures of human alloreactive or virus-specific T cells. The significance of these CD4+ CTL for an immune reaction in vivo is not clear. Since Epstein-Barr virus (EBV) transformed B cells express HLA-class I and class II antigens equally well both CD8+ and CD4+ CTL should be stimulated during an acute EBV infection. We analysed the MHC specificity and the phenotype of EBV-specific CTL from patients with infectious mononucleosis (IM). When tested directly without any previous culture, T cells from patients in the acute phase of IM showed specific MHC-restricted cytotoxicity against the autologous B cell line. Addition of a HLA class I specific monoclonal antibody (MoAb) but not of a HLA class II specific MoAb resulted in a complete blocking of the lytic activity. Cell sorting revealed that the entire cytotoxic activity was present in the CD8+ fraction whereas no specific CTL were detectable in the CD4+ fraction. The absence of cytotoxicity in CD4+ cells was not due to a lack of activation of these cells since both CD8+ and CD4+ cells were activated in situ, showing spontaneous growth in interleukin-2 (IL-2) and expressing the activation marker TP103. Frequency estimation revealed that 1/300-1/600 CD8+ but only 1/2000-1/4000 CD4+ T cells gave rise to a specific CTL colony after 10 days. If CD4+ colonies were tested repeatedly for cytotoxicity we found that CD4+ CTL acquired their cytotoxicity during in vitro culture. In addition, we isolated EBV-specific CD4+ T cell clones able to lyse their stimulator cells in the presence but not in the absence of lectin, even after a long period of culture. Taken together our results show that cytotoxicity mediated by CD4+ T cells does not play a role in an anti-viral immune response.

Elevation of soluble CD23 in sera from patients with infectious mononucleosis.

CD23 is induced in B cells upon infection by Epstein-Barr virus (EBV) and a soluble form (soluble CD23: sCD23) is found in culture supernatants from EBV-transformed B cell lines. Based on these observations, we measured serum sCD23 levels in patients with infectious mononucleosis (IM) caused by EBV infection. Sera from patients with IM at the time of diagnosis contained more sCD23 than sera from normal control subjects. Changes in serum sCD23 levels during the course of disease showed that serum sCD23 levels were elevated at the time of diagnosis and they decreased to the normal levels during the convalescent phase defined by the improvement of symptoms of IM. These results indicate that the elevated levels of sCD23 were observed at the acute phase of IM and may be useful in diagnosing IM.

Influenza A virus hemagglutinin is a B cell-superstimulatory lectin

Primary Epstein-Barr virus (EBV) infection in childhood is usually asymptomatic, but sometimes causes infectious mononucleosis (IM). Very occasionally, IM develops into a life-threatening EBV-associated hemophagocytic syndrome (EBV-AHS). We studied the importance and usefulness of measuring cell-free viral DNA in the serum of patients with these primary EBV infections. Using real-time quantitative polymerase chain reaction, cell-free EBV-DNA was quantified in the serum of nine children with IM and three with EBV-AHS. In the acute phase of IM, an average of 10(2.4) copies/ml of EBV-DNA was detected in 95% of sera. The EBV load gradually decreased and disappeared within 1 month. Patients with EBV-AHS had an extremely high viral load in their sera (10(5.5)-10(7.4) copies/ ml). The viral load persisted longer in these patients, although it decreased in parallel with the improvement of symptoms. These results indicate that cell-free EBV-DNA was frequently detected in patients with primary EBV infection and could, therefore, be used as a marker for EBV infection. Measuring the cell-free EBV-DNA is useful for monitoring the primary EBV infection, especially in EBV-AHS.

Cytokine production in a whole-blood assay after Epstein-Barr virus infection in vivo.

Epstein-Barr virus (EBV) has a marked tropism for cells of the immune system, and infection can result in profound immunomodulatory effects. In order to examine the role of cytokines during the acute phase of infectious mononucleosis, we studied the levels of different interleukins (ILs), interferons (IFNs), and the soluble IL-2 receptor (sIL-2R) in serum samples of 20 patients. We found elevated levels of IL-2, IL-6, sIL-2R, and IFN-gamma. Whereas the peak of IL-2 and IL-6 concentration occurred during the first week (P < 0.01), the largest amounts of sIL-2R were measured during the second week (P < 0.01). IFN-gamma levels were only enhanced during the first week. In addition, we investigated the ability to produce cytokines in response to mitogenic stimulation in a whole-blood assay of 11 patients compared with healthy blood donors. In the whole-blood assay of patients compared with controls after stimulation with lipopolysaccharide, we measured more than 10-fold elevated levels of tumor necrosis factor alpha (P < 0.01), 3-fold elevated levels of IL-1 beta (P < 0.01), and about 2-fold increased amounts of IL-6 (P < 0.01). A significant enhancement in sIL-2R and IFN-gamma concentration was found in the assay after stimulation with phytohemagglutinin after 24 h of incubation (P < 0.01). Collectively, our data seem to indicate that monocytes are strongly activated during infectious mononucleosis. Monocytes and monocyte-derived factors may play an important role in the pathogenesis of infectious mononucleosis and, together with T lymphocytes, may be partly responsible for clinical symptoms.

Epstein-Barr Virus gp350-Specific Antibody Titers And Antibody-Dependent Cellular Cytotoxic Effector Function In Different Groups Of Patients: A Study Using Cloned gp350-Expressing Transfected Human T Cell Targets

An NK cell activity-resistant human lymphoid T cell line (CEM-NKr) expressing the transfected Epstein-Barr virus (EBV) gp350 gene was used in membrane immunofluorescence (MIF) and antibody-dependent cellular cytotoxicity (ADCC) assays to analyze the gp350-specific humoral and ADCC responses in groups of EBV-seropositive persons. Results show that there is no correlation between gp350-specific ADCC-mediating antibody titers and MIF or EBV neutralizing antibody titers. For example, sera from patients in the acute phase of infectious mononucleosis, while positive by MIF assay or EBV neutralization test, were not reactive in the ADCC assay. Results also show that nasopharyngeal carcinoma (NPC) patients on MIF present high IgG titers against gp350 compared with healthy persons. Anti-gp350 IgA antibodies were detected in all groups tested; however, titers were highest in the NPC group.

Microbiology of tonsillar surfaces in infectious mononucleosis.

To compare the cultures of tonsillar surface aerobic and anaerobic bacterial flora taken during the acute phase of infectious mononucleosis with the repeated cultures taken 2 months later. Fourteen patients with pharyngotonsillitis associated with infectious mononucleosis. A total of 121 bacterial isolates (ie, 84 anaerobes and 37 facultatives and aerobes) were isolated in the acute stage, and 75 isolates (ie, 42 anaerobes and 33 aerobes) were recovered 2 months later. The reduction in the number of organisms in the second specimen was mostly due to the decrease in the recovery of Prevotella intermedia (13 in the first culture, compared with four in the second) and Fusobacterium nucleatum (12 vs four, respectively). The study illustrates that the surfaces of tonsils of patients with infectious mononucleosis contain more species of anaerobic organisms during the illness than following it. The potential role of these organisms in the inflammation process warrants further study.

Serum levels of lymphokines and soluble cellular receptors in primary Epstein-Barr virus infection and in patients with chronic fatigue syndrome.

The immunopathology in primary Epstein-Barr virus (EBV) infections and in chronic fatigue syndrome was studied by examining serum levels of interleukins (IL) and of soluble T cell receptors in serum samples. Serum samples were from patients during and 6 months after primary EBV-induced infectious mononucleosis and from patients with chronic fatigue syndrome and serologic evidence of EBV reactivation. Markers for T lymphocyte activation (soluble IL-2 and CD8) and for monocyte activation (neopterin) were significantly elevated during acute infectious mononucleosis but not in patients with chronic fatigue syndrome. Interferon-alpha, IL-1 beta, and IL-6 levels were not significantly increased in any patient group but inferferon-gamma levels were significantly increased during the acute phase of infectious mononucleosis. The levels of IL-1 alpha were significantly higher than in controls both in patients with infectious mononucleosis and in those with chronic fatigue syndrome. In the latter, the lack of most markers for lymphocyte activation found in patients with infectious mononucleosis makes it less likely that EBV reactivation causes symptoms.

Antibodies to histones in infectious mononucleosis.

A polyspecific human monoclonal (auto)antibody, isolated from a patient in the acute phase of infectious mononucleosis, was found to react with all subfractions (H1, H2A, H2B, H3 and H4) of histones. This finding prompted us to study the occurrence of antibodies to histones in sera of patients with infectious mononucleosis. It was found that IgM binding to histones was detectable both in control and patient sera; however, sera from patients showed binding values of IgM antibodies to histones significantly higher than those of healthy controls; moreover, both in control and patient groups anti-histone IgM activity was found to correlate with serum IgM concentration. These findings suggest that anti-histone IgM antibodies belong to the class of antibodies defined as "natural antibodies" and that their increase during infectious mononucleosis is due to Epstein-Barr virus-induced polyclonal B cell activation.

Acute Appendicitis Complicating Infectious Mononucleosis: Case Report and Review

Acute appendicitis is an uncommon complication of infectious mononucleosis (IM) and can readily be misdiagnosed because of the acute abdominal pain with which patients with IM occasionally present. A case report is presented of a patient with IM who developed acute appendicitis during the acute phase of the illness. The appendicitis progressed to the formation of an abscess, which was evacuated at surgery. Histologic examination of the appendix showed absence of lymphoid follicles in the mucosal layer and intense lymphoid infiltration of the mucosa and submucosa by a mixed diffuse proliferation of lymphoid cells with groups of immunoblasts scattered among them. The lymphoid infiltrate was mainly composed of T lymphocytes; the anticomplementary immunofluorescent staining of the appendix for EBNA (Epstein-Barr nuclear antigen) was negative. Three cases of appendicitis complicating IM published in the literature are reviewed. All had clinical and histopathologic features similar to those of our patient and were cured after surgery. Our case report together with the literature review confirms that appendicitis in the acute phase of IM has distinct clinical and histopathologic features and thus has to be considered a true complication of IM rather than merely a simultaneous disease.

Lysis of P3HR-1 cells induced to enter the viral cycle by antibody-dependent and independent immunological mechanisms

The P3HR-1 Burkitt lymphoma line carries the Epstein-Barr virus (EBV) genome and a small proportion of the cells (1–3%) enter the lytic cycle spontaneously. Treatment with TPA and n-butyrate elevates considerably the number of virus-producing cells (25–35%). Cells which enter the lytic cycle express the EBV early antigen EA, the viral capsid antigen VCA, and the membrane antigen MA. Antibodies against these antigens are present in EBV-immune human sera. The expression of virus envelope protein on the plasma membrane renders the cells sensitive to immune effector mechanisms. These were shown to be initiated by the alternative complement pathway (ACP)-activating capacity of the cells and by their reactivity with antibodies directed to the MA. When incubated with EBV-immune or nonimmune human serum, the induced (P3HR-1-V) cells activated C3 through ACP and fixed the generated C3 fragments. The efficiency of opsonization was higher in immune serum. By varying the experimental conditions we showed the damage of the induced cells by the complement system and by blood lymphocytes, and analysed the involvement of antibodies and the activated C3 fragments in the lymphocyte-mediated lysis. P3HR-1-V cells were lysed by immune serum and also by nonimmune serum though with lower efficiency. The induced cells had elevated sensitivity to the NK effect which was potentiated if the conditions allowed their opsonization. In the presence of antibodies the lymphocyte-mediated lysis was considerably higher and the ADCC mechanism was also potentiated by opsonization. These experiments suggest that B cells which enter the virus-producing cycle may be eliminated in EBV nonimmune host by NK cells. After the antibody response against the virus develops, the attack on these cells is more efficient through complement and lymphocyte-mediated antibody-dependent mechanisms. These effector mechanisms are enhanced by opsonization which is the consequence of the C3-activating capacity of the cells. The multiple ways of the immune attack on the B cells prepared to produce EBV may explain the absence of EA and VCA positive B cells in tumor cell populations and during the acute phase of infectious mononucleosis.