Pathogenesis of measles immunodeficiency and encephalomyelitis: parallels to AIDS

Central nervous system virion detection in acute measles: histopathological, ultrastructural and pathogenetic aspects

Histopathological and ultrastructural studies of 23 patients who died with clinical diagnosis of measles were carried out. In 12 cases viral nucleocapsids were searched by electron microscopy and detected in 100% of the cases in the lungs and in 50% of the cases in the central nervous system. They were mostly intranuclear. Histopathological changes associated to neurological alterations and the detection of virion are discussed in relation to acute and delayed clinical manifestations.

The Soriano Award Lecture. Emerging infections of the nervous system

The epidemic of acquired immunodeficiency disease [AIDS] has focused interest on the origins of "new" infectious agents. Great plagues are well known from the distant past, but a number of novel diseases affecting the nervous system infections have emerged in recent years. The causes of such new disorders are diverse: whereas rapid mutations of microbes allow the evolution of truly novel agents, the appearance of new diseases is more often due to changes in human or vector populations or changes in societal mores that result in dissemination of preexistent microbes. Examples of recently emerging infections that involve the nervous system include the enterovirus 70 epidemics with poliomyelitis-like disease, the appearance of California virus encephalitis in the midwestern United States, the rapid spread of Lyme disease with its many neurological complications in the eastern United States, and the outbreak of bovine spongiform encephalopathy in the United Kingdom, in addition to the devastating epidemic of human immunodeficiency virus (HIV), which will cause nervous system disease in over half of those infected. As the world population increases and modern transportation brings us closer into a "global village" more new agents will emerge and more will be sustained. Knowledge of the molecular biology and ecology of the agents and awareness of how our actions can alter their behavior are our best defense.

Vaccinology, immunology, and comparative pathogenesis of measles in the quest for a preventative against AIDS

Current approaches to the prevention and control of AIDS by vaccines and by chemotherapy have failed to provide satisfactory solutions to this important medical problem and have failed, in addition, to provide definitive guidelines for future research endeavor. Vaccine research must and will continue but it is possible that a safe and effective vaccine may never be developed and it may be timely to explore, in addition, alternative means for immunological intervention in AIDS. Both immunoprophylactic and immunotherapeutic efforts might be assisted by manipulating the T helper 1 (Th1) and T helper 2 (Th2) subsets of CD4+ T helper cells, which is therefore worthy of exploration. Selective control of immune response by the two T helper subsets is by release of different cytokines that promote either cellular or humoral immunity, the latter of which may be associated with inappropriate immune responses and with immune dysfunction. Discovery of the Th1 and Th2 subsets and definition of the cytokines they release provide a new avenue toward possible development of a safe and effective vaccine and an approach, in addition, to correction of immune dysfunction by selective cytokine administration or by cytokine ablation by antagonists or antibodies. AIDS pathogenesis and immune dysfunction are complex and understanding them may be overwhelmed by an excess of possibilities. Simplification of the endeavor might benefit from comparative studies of the pathogenesis of measles, in which there also is immune deficiency but usually with spontaneous viral clearance, reversal of immune dysfunction, and total recovery. In addition, measles presents as a single disease and is caused by antigenically stable virus. Identification of the process whereby measles immunodeficiency is spontaneously reversed might be of importance in attempting to devise means for similar reversal in AIDS.

Immune activation in measles

Measles is associated with alterations in immune regulation that sometimes lead to secondary infections or autoimmune encephalomyelitis. Simultaneously, an effective measles virus-specific immune response develops. To relate immune activation to measles and its complications, we studied the spontaneous proliferation of blood mononuclear cells and circulating levels of soluble interleukin-2 receptor and CD8 T-cell antigens in 126 patients with complicated or uncomplicated measles at various stages of the disease. Spontaneous proliferation of mononuclear cells, which was present through the first week of the rash, was greater in cells from patients with measles (8787 +/- 1403 cpm) than in those from healthy children (1529 +/- 237 cpm, P less than 0.0001). Levels of soluble interleukin-2 receptor (3385 +/- 195 units per milliliter) and CD8 (4145 +/- 437 units per milliliter) were higher in patients with measles than in those with other infectious diseases (2377 +/- 440, P = 0.003; 2399 +/- 771, P = 0.0374) or in healthy children (865 +/- 138, P less than 0.0001; 1026 +/- 169, P less than 0.0001). Levels of soluble interleukin-2 receptor were elevated before the onset of the rash and remained elevated for several weeks. In contrast, levels of soluble CD8 increased only when the rash appeared, and subsided quickly. Spontaneous proliferation of mononuclear cells and levels of soluble CD8 were similar in patients with uncomplicated disease, pneumonia, or encephalomyelitis, but soluble interleukin-2 receptor levels were lower in patients with encephalomyelitis (2312 +/- 314 vs. 3455 +/- 247 units per milliliter in uncomplicated measles; P = 0.01). In patients with encephalomyelitis, cerebrospinal fluid levels of soluble CD8 (686 +/- 350 units per milliliter), but not interleukin-2 receptor (9 +/- 8.3 units per milliliter), were increased. We conclude that the proliferative phase of the immune response, as measured by the release of soluble interleukin-2 receptor, begins before the rash appears, continues for several weeks in those without complications, but does not occur within the nervous system. In contrast, the effector phase of the immune response, as measured by the release of soluble CD8, coincides with the appearance and disappearance of the rash and occurs within the nervous system during encephalomyelitis.