Chronic fatigue syndrome: thoughts on pathogenesis

Sleep and fatigue in mice infected with murine gammaherpesvirus 68

Fatigue, a common symptom of many acute and chronic medical conditions, reduces both quality of life and workplace productivity and can be disabling. However, the pathophysiologic mechanisms that underlie fatigue can be difficult to study in human populations due to the patient heterogeneity, the variety of underlying causes and potential triggering events, and an inability to collect samples that may be essential to elucidation of mechanisms (e.g., brain). Although the etiology of chronic fatigue syndrome (CFS) remains elusive, some studies have implicated viral infections, including Epstein-Barr virus (EBV), a human gammaherpesvirus, as a potential factor in the pathogenesis of CFS. Murine gammaherpesvirus 68 (γHV68) is a mouse pathogen that shares many similarities with human γHVs, including EBV. In this study, we use γHV68-infected C57BL/6J mice as a model system for studying the impact of chronic viral infection on sleep-wake behavior, activity patterns, and body temperature profiles. Our data show that γHV68 alters sleep, activity, and temperature in a manner suggestive of fatigue. In mice infected with the highest dose used in this study (40,000plaque forming units), food intake, body weight, wheel running, body temperature, and sleep were normal until approximately 7days after infection. These parameters were significantly altered during days 7 through 11, returned to baseline levels at day 12 after infection, and remained within the normal range for the remainder of the 30-day period after inoculation. At that time, both infected and uninfected mice were injected with lipopolysaccharide (LPS), and their responses monitored. Uninfected mice given LPS developed a modest and transient febrile response during the initial light phase (hours 12 through 24) after injection. In contrast, infected mice developed changes in core body temperatures that persisted for at least 5days. Infected mice showed an initial hypothermia that lasted for approximately 12h, followed by a modest fever that persisted for several hours. For the remainder of the 5-day recording period, they showed mild hypothermia during the dark phase. Running wheel activity of infected mice was reduced for at least 5days after injection of LPS, but for only 12h in uninfected mice. Collectively, these observations indicate that (1) physiologic and behavioral processes in mice are altered and recover during an early phase of infection, and (2) mice with latent γHV68 infection have an exacerbated response to challenge with LPS. These findings indicate that laboratory mice with γHV68 infections may provide a useful model for the study of fatigue and other physiologic and behavioral perturbations that may occur during acute and chronic infection with gammaherpesviruses.

Psychosocial and immunological factors in neurasthenia

BACKGROUND

Neurasthenia is a disorder whose pathogenesis is still unknown.

OBJECTIVE

The authors sought to examine the relationships between neurasthenia and possible psychosocial and immunological correlates.

METHOD

A sample of 30 Chinese neurasthenic patients was compared with a matched sample of 30 control subjects for 1) the level of serum Epstein-Barr virus (EBV) gamma G immunoglobulin (IgG) and gamma M immunoglobulin (IgM); 2) scores on the Eysenck Personality Questionnaire (EPQ); 3) the Symptom Checklist-90; and 4) the Life Event Scale (LES); 27 of the 30 neurasthenia patients were treated with medication and psychotherapy for a 4-month period, with measures taken pre- and posttreatment.

RESULTS

As compared with the control group, neurasthenic patients exhibited higher EPQ scores for neuroticism, higher levels of introversion, and a higher number of negative life events. Within the neurasthenia sample, scores for neuroticism and the SCL-90 Global Severity Index were significantly lower at follow-up than at baseline.

CONCLUSION

As compared with control subjects, neurasthenia patients were characterized by greater neuroticism and introversion, and they reported a higher rate of negative life events. Moreover, the positive rate of EBV in neurasthenic patients was higher, which may be associated with higher EBV activation under states of stress.

Chronic fatigue syndrome and the treatment process

Fatigue is a common complaint in general practice and is often associated with psychiatric and psychosocial problems and demoralization. Although the Centers for Disease Control definition of chronic fatigue syndrome (CFS) excludes pre-existing psychiatric illness, common psychosocial problems short of a clinical disorder (such as irritability, difficulty in thinking, inability to concentrate, depression and sleep disturbance) overlap with the criteria for CFS. Psychological states can affect the course of CFS or become confused in the patient's and doctor's mind with the course of infection. The core dilemma in practice is how aggressively to pursue a possible basis for CFS when it persists in the absence of an identifiable external cause. Possibilities for exploration are numerous and potentially expensive. In practice, the persistence of doctors depends on the patient's illness behaviour, on financial and organizational factors, and on the culture of medical care and practice styles. It is essential to differentiate the appropriate management of CFS from scientific study where intensive investigation may be warranted. In practice doctors should proceed in a manner that conveys concern, supports function, and avoids dysfunctional illness behaviour and inadvertent legitimization and reinforcement of disability.

Autologous Epstein-Barr virus (EBV)-specific cytotoxic T cells for the treatment of persistent active EBV infection

Chronic active Epstein-Barr virus (CAEBV) infection syndrome is a heterogeneous EBV-related disorder characterized by chronic fatigue, fever, lymphadenopathy, and/or hepatosplenomegaly, associated with abnormal patterns of antibody to EBV. CAEBV can range from disabling mild/moderate forms to rapidly lethal disorders. Even patients with mild/moderate disease frequently suffer adverse effects from long-term anti-inflammatory agents and have a quality of life that progressively deteriorates. It is still unknown why these individuals are unable to produce an effective immune response to control EBV, and no effective treatment is currently available. Since ex vivo-expanded EBV-specific cytotoxic T lymphocytes (EBV-CTLs) can safely restore EBV-specific cellular immune responses in immunodeficient patients, we assessed the possibility that adoptive immunotherapy might also effectively treat CAEBV infection. Following stimulation with irradiated EBV-transformed lymphoblastoid cell lines (LCLs), EBV-CTLs were successfully generated from 8 of 8 patients with the mild/moderate form of CAEBV infection. These CTLs were predominantly CD3(+) CD8(+) cells and produced specific killing of the autologous LCLs. There were 5 patients with 1- to 12-year histories of disease who were treated with 1 to 4 injections of EBV-CTLs. Following infusion, there was resolution of fatigue and malaise, disappearance of fever, and regression of lymphadenopathy and splenomegaly. The pattern and titers of anti-EBV antibodies also normalized. No toxicity was observed. There were 4 patients who did not show any relapse of disease within 6 to 36 months follow-up; one patient had recurrence of fatigue and myalgia one year after CTL infusion. We suggest that adoptive immunotherapy with autologous EBV-CTLs may represent a safe and feasible alternative treatment for patients affected with mild/moderate CAEBV infection and that this approach should be evaluated in the more severe forms of the disease.

Cytokine and other immunologic markers in chronic fatigue syndrome and their relation to neuropsychological factors

The literature is reviewed and data are presented that relate to a model we have developed to account for the perpetuation of the perplexing disorder currently termed chronic fatigue syndrome (CFS). In patients with CFS there is chronic lymphocyte overactivation with cytokine abnormalities that include perturbations in plasma levels of proinflammatory cytokines and decrease in the ratio of Type 1 to Type 2 cytokines produced by lymphocytes in vitro following mitogen stimulation. The initiation of the syndrome is frequently sudden and often follows an acute viral illness. Our model for the subsequent chronicity of this disorder holds that the interaction of psychological factors (distress associated with either CFS-related symptoms or other stressful life events) and the immunologic dysfunction contribute to (a) CFS-related physical symptoms (e.g., perception of fatigue and cognitive difficulties, fever, muscle and joint pain) and increases in illness burden and (b) impaired immune surveillance associated with cytotoxic lymphocytes with resulting activation of latent herpes viruses.

Course and outcome of chronic fatigue in children and adolescents

PURPOSE

To describe the epidemiology, symptoms, and psychosocial characteristics of children and adolescents evaluated in a chronic fatigue program and determine the course and outcome of the syndrome in these patients.

METHODS

During the summer of 1994, chart review was performed for the 58 patients evaluated between 1990 and 1994 and a telephone follow-up was conducted with 42 of the 58 families. Patients were predominantly female (71%) and white (94%), with 50% between the ages of 7 and 14 years and 50% between the ages of 15 and 21 years (mean age 14.6 years).

RESULTS

At time of presentation, 50% of patients had been fatigued for 1 to 6 months and 50% had been fatigued for 7 to 36 months. Sixty percent indicated the fatigue had begun with an acute illness and 60% had a history of allergies. Most commonly reported symptoms were fatigue (100%), headache (74%), sore throat (59%), abdominal pain (48%), fever (36%), and difficulties with concentration and/or memory (33%). Most patients had a worsening of school performance and a decrease in social activities. On follow-up, there was significant improvement in many patients during the summer after the first visit, with continued improvement in most patients during the second and third years. At time of the follow-up telephone call, 43% of families considered their child "cured" and 52% considered their child "improved," whereas only 5% considered their child to be "the same." Statistical analyses demonstrated no demographic or clinical factors that distinguished between those who did or did not participate in the follow-up study, or between those who did or did not do well on follow-up.

CONCLUSIONS

These data demonstrate that children and adolescents with chronic fatigue have a syndrome that is similar to that described in adults, but that the syndrome differs in several ways, most specifically, presentation earlier in the course of the illness and a more optimistic outcome.

Physical symptoms of chronic fatigue syndrome are exacerbated by the stress of Hurricane Andrew

This study examined the effects of Hurricane Andrew on physical symptoms and functional impairments in a sample of chronic fatigue syndrome (CFS) patients residing in South Florida. In the months after Hurricane Andrew (September 15-December 31, 1992), 49 CFS patients were assessed for psychosocial and physical functioning with questionnaires, interviews, and physical examinations. This sample was made up of 25 CFS patients living in Dade county, a high impact area, and 24 patients in Broward and Palm Beach counties, areas less affected by the hurricane. Based on our model for stress-related effects on CFS, we tested the hypothesis that the patients who had the greatest exposure to this natural disaster would show the greatest exacerbation in CFS symptoms and related impairments in activities of daily living (illness burden). In support of this hypothesis, we found that the Dade county patients showed significant increases in physician-rated clinical relapses and exacerbations in frequency of several categories of self-reported CFS physical symptoms as compared to the Broward/Palm Beach county patients. Illness burden, as measured on the Sickness Impact Profile, also showed a significant increase in the Dade county patients. Although extent of disruption due to the storm was a significant factor in predicting relapse, the patient's posthurricane distress response was the single strongest predictor of the likelihood and severity of relapse and functional impairment. Additionally, optimism and social support were significantly associated with lower illness burden after the hurricane, above and beyond storm-related disruption and distress responses. These findings provide information on the impact of environmental stressors and psychosocial factors in the exacerbation of CFS symptoms.