Epstein-Barr virus (EBV) can display different forms of latent infection in B-cell lines in vitro; however, the types of infection normally established by the virus in vivo remain largely unexplored. Here we have approached this question by analyzing the types of viral RNAs present in mononuclear cells freshly isolated from the blood of 14 infectious mononucleosis patients undergoing primary EBV infection and 6 long-term virus carriers. Reverse transcription-PCR amplifications were carried out with a panel of oligonucleotide primers and probes which specifically detect (i) the EBER1 RNA common to all forms of latency, (ii) transcripts either from the Cp and Wp promoters generating all six nuclear antigen (EBNA1, -2, -3A, -3B, -3C, -LP) mRNAs or from the Fp promoter generating a uniquely spliced EBNA1 mRNA, (iii) the latent membrane protein (LMP1 and 2A) mRNAs, and (iv) the BZLF1 mRNA, an immediate-early marker of lytic cycle. Viral transcription in infectious mononucleosis mononuclear cells (and in the B-cell-enriched fraction) regularly included the full spectrum of latent RNAs seen during EBV-induced B-cell growth transformation in vitro, i.e., EBER1, Cp/Wp-initiated EBNA mRNAs, and LMP1/LMP2 mRNAs, in the absence of lytic BZLF1 transcripts. In addition, transcripts with the splice pattern of Fp-initiated EBNA1 mRNA, hitherto seen only in vivo in certain EBV-positive tumors, were frequently detected. In long-term virus carriers, the mononuclear cells were again positive for latent (EBER1) and negative for lytic (BZLF1) markers; Cp/Wp-initiated RNAs were not detected in these samples, but in several individuals it was possible to amplify both Fp-initiated EBNA1 mRNA and LMP2A mRNA signals. We suggest (i) that primary infection is associated with a transient virus-driven expansion of the infected B-cell pool through a program of virus gene expression like that seen in in vitro-transformed cells and (ii) that long-term virus carriage is associated with a switch from Cp/Wp to Fp usage and thus to a more restricted form of latent protein expression that may render the infected cells less susceptible to recognition by the virus-specific cytotoxic T-cell response.

Epstein-Barr virus latency in blood mononuclear cells: analysis of viral gene transcription during primary infection and in the carrier state.

This study used a prospective design to examine the influence of examination stress and loneliness on herpesvirus latency as measured by changes in antibody levels to three herpesviruses, Epstein-Barr virus (EBV), Herpes simplex type I (HSV-1), and cytomegalovirus (CMV). Three blood samples were obtained from 49 first-year medical students, with the first sample drawn 1 month before final examinations, the second on the first day of final examinations, and the third during the first week after their return from summer vacation. A median split on the UCLA Loneliness Scale divided subjects into high- and low-scoring loneliness groups. There were significant changes in the antibody titers to all three herpesviruses across the sample points, with the lowest levels found in the third (low stress) sample. High-loneliness subjects had significantly higher EBV antibody titers than low-loneliness subjects. These data suggest that stress-related immunosuppression can significantly modulate herpesvirus latency.

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Stress, loneliness, and changes in herpesvirus latency.

Healthy Epstein-Barr virus (EBV) seropositive undergraduates (N = 57) completed a personality inventory, provided blood samples, and were randomly assigned to write or talk about stressful events, or to write about trivial events, during three weekly 20-min sessions, after which they provided a final blood sample. Individuals assigned to the verbal/stressful condition had significantly lower EBV antibody titers (suggesting better cellular immune control over the latent virus) after the intervention than those in the written/stressful group, who had significantly lower values than those in the written/trivial control group. Subjects assigned to the written/stressful condition expressed more negative emotional words than the verbal/stressful and control groups and more positive emotional words than the verbal/stressful group at each time point. The verbal/stressful group expressed more negative emotional words compared with the control group at baseline. Content analysis indicated that the verbal/stressful group achieved the greatest improvements in cognitive change, self-esteem, and adaptive coping strategies.

Emotional disclosure through writing or speaking modulates latent Epstein-Barr virus antibody titers.

Immune regulation in Epstein-Barr virus-associated diseases.

Viruses may cause immunosuppression by a variety of mechanisms. This review delineates four categories. First, immunosuppression can result from the direct effects of viral replication on lymphocyte functions. Either all classes of lymphocytes can be affected, as occurs in measles, or the effect can be restricted to a cell subtype, as is the case with human T cell-lymphotropic virus type III. Second, the activity of soluble factors of viral or host origin released from infected cells can affect immunosuppression. A third mechanism results from viral infection of macrophages and affects the function of these cells in natural and acquired immunity. Finally, immunosuppression may result from viral triggering of an imbalance in immune regulation, which culminates in the overactivity of suppressor cells. A detailed knowledge of the mechanisms by which viruses are involved in immunosuppression may help in the design of strategies to reverse the effect.

Immunosuppression in Viral Infections

Under appropriate culture conditions, EB virus infection of lymphocytes from seropositive donors leads to regression of transformation, and this was shown previously to be due to activation in a secondary immune response of T lymphocytes inhibitory for the autologous lymphoblastoid cell line. Regression can be quantified by determining the number of cells required for its expression. To investigate the development of memory T cells with EB‐virus specificity in the primary infection, a comparison was made of the capacity for regression of lymphocytes from 16 cases of infectious mononucleosis (IM) and 13 normal donors. With 9 normal seropositive donors a mean lymphocyte concentration of 4.6 × 10/ml was required to achieve 50% regression. In contrast, with 8 cases of IM tested within I week of onset, a much higher mean lymphocyte concentration (3.7 × 10/ml) was necessary. Six of these IM cases, and another not tested in the first week, were tested on several occasions between 5 and 23 weeks after onset, and showed a slight reduction in the mean cell concentration required for regression (1.5 × 1O/ml). Six additional IM cases were tested 23–83 weeks after onset by which time the cell concentration required for 50% regression (mean = 4.5 × 1O/ml) had reached the level shown by normal seropositive donors. Regression did not occur with lymphocytes from seronegative donors, even at the highest cell concentration. Recombination cultures of T‐cell‐de‐pleted and T‐cell‐enriched lymphocyte populations from 3 IM cases in ratios of 1:7 to 7:1 showed that the failure of regression in acute IM was not due simply to lack of sufficient numbers of T cells. The results indicate that EB‐virus‐specific memory T‐cell activity as detected by the regression test is absent in the acute phase of IM, becomes evident at low levels 5–23 weeks after onset, and reaches a maximum after about 6 months.

A. B. Rlckinson

Papers

Long-term T-cell-mediated immunity to Epstein-Barr virus in man. IV. Development of T-cell memory in convalescent infectious mononucleosis patients.