Measles virus vaccination of measles seropositive individuals suppresses lymphocyte proliferation and chemotactic factor production

Measles virus infection of human keratinocytes: Possible link between measles and atopic dermatitis

BACKGROUND

Measles virus (MV) infection is marked with a skin rash in the acute phase of the disease, which pathogenesis remains poorly understood. Moreover, the association between measles and progression of skin diseases, such as atopic dermatitis (AD), is still elusive.

OBJECTIVE

We have thus analysed the susceptibility of human keratinocytes to MV infection and explore the potential relationship between MV vaccination and the pathogenesis the AD.

METHODS

We performed immunovirological characterisation of MV infection in human keratinocytes and then tested the effect of live attenuated measles vaccine on the progression of AD in adult patients, in a prospective, double-blind study.

RESULTS

We showed that both human primary keratinocytes and the keratinocyte cell line HaCaT express MV receptors and could be infected by MV. The infection significantly modulated the expression of several keratinocyte-produced cytokines, known to be implicated in the pathogenesis of inflammatory allergic diseases, including AD. We then analysed the relationship between exposure to MV by vaccination and the progression of AD in 20 adults during six weeks. We found a significant decrease in CCL26 and thymic stromal lymphopoietin (TSLP) mRNA in biopsies from acute lesions of vaccinated patients, suggesting MV-induced modulation of skin cytokine expression. Clinical analysis revealed a transient improvement of SCORAD index in vaccinated compared to placebo-treated patients, two weeks after vaccination.

CONCLUSIONS

Altogether, these results clearly demonstrate that keratinocytes are susceptible to MV infection, which could consequently modulate their cytokine production, resulting with a beneficial effect in the progression of AD. This study provides thus a proof of concept for the vaccination therapy in AD and may open new avenues for the development of novel strategies in the treatment of this allergic disease.

Safety and immunogenicity of early measles vaccination in children born to HIV-infected mothers in the United States: results of Pediatric AIDS Clinical Trials Group (PACTG) protocol 225

BACKGROUND.: ACTG (Pediatric AIDS Clinical Trials Group) 225, a multicenter, randomized, open-label trial in the United States evaluated reactogenicity and immunogenicity of 2 vaccination regimens: monovalent measles vaccine (Attenuvax) at 6 months of age and measles, mumps, and rubella, live attenuated (MMRII) vaccine at 12 months of age (2D), or only MMRII at 12 months of age (1D) in human immunodeficiency virus-infected (HIV-infected) (POS) and uninfected (NEG) children in the pre-highly active antiretroviral therapy (pre-HAART) period.

METHODS

Plaque-reduction neutralization (PRN) of measles-neutralizing antibody titers were evaluated at study weeks 0, 6, 26, 32, 52, and 130 (∼3 years of age).

RESULTS

The 110 subjects included: 65 2DNEG; 30 1DNEG; 7 2DPOS and 8 1DPOS. Vaccinations (n=175) were associated with no adverse experiences >Grade 2 except for Grade 3 fever (n=2, 1 1DPOS and 1 1DNEG). Six weeks after Attenuvax, all 2DPOS subjects (7/7) seroresponded (PRN titers ≥120 mIU/mL) with median titers significantly exceeding 2DNEG titers (2115 vs 628 mIU/mL, respectively; P=.023). At ∼3 years of age, 67% 1DPOS (4/6) and 83% 2DPOS (4/5) subjects maintained titers ≥120 mIU/mL. Prevaccination titers ≥25 mIU/mL among 2DNEG subjects correlated inversely with the likelihood of achieving titers ≥120 mIU/mL (56% vs 90%; P=.004).

CONCLUSIONS

Among HIV-infected children pre-HAART, Attenuvax at 6 months was well tolerated and immunogenic. These data support the current World Health Organization (WHO) recommendation to administer a first dose of measles vaccine at 6 months of age to HIV-infected children.

Influence of measles vaccination on the progression of atopic dermatitis in infants

Atopic dermatitis (AD) is a chronic inflammatory skin disease, affecting 10-20% of children. Measles vaccination has been reported to have contradictory effects on incidence of AD in children. Therefore, we performed the first prospective, double-blind, placebo-controlled study to analyze the evolution of AD in infants after measles vaccination. The study included 12 infants (10-14 months old) with AD, randomly assigned to two groups: while the first group received a single dose of a standard measles vaccine ROUVAX, the second was treated with placebo (vehicle). Infants were followed-up for 6 months after administration of ROUVAX/placebo for the clinical signs associated with AD, by determination of SCORAD index. In addition, serum was taken before vaccination and 1 month later to determine the presence of seroconversion and to analyze the progression of serum levels of CCL18 (PARC) and E-selectin, known to be distinct serum markers that reflect clinical features of AD. In the vaccinated group, five of six children seroconverted 1 month after treatment and one infant showed a 50% improvement of SCORAD. Serum levels of CCL18 were significantly decreased in two treated infants (of four analyzed for this group) and E-selectin slightly decreased in one infant (of three analyzed by this test). In placebo-treated group the SCORAD improved in one patient and serum levels of CCL18 and E-selectin did not change. These data suggest that measles vaccination not only does not aggravate AD, but may also improve some of the immunological parameters of this allergic disease. Inclusion of a higher number of patients in a similar study should give a more comprehensive overview of the benefit of measles vaccination on the clinical evolution of AD patients, and potentially open new avenues to the clinical application of the anti-inflammatory effect of measles virus proteins.

Alterations in cell-mediated immune response in subacute sclerosing panencephalitis

To investigate T cell responses in subacute sclerosing panencephalitis (SSPE), we analyzed proliferation and cytokine secretion of cells from 35 patients and 42 healthy controls (HC) in response to central nervous system (CNS) antigens. The proliferation in response to myelin basic protein (MBP), myelin oligodendrocyte-glycoprotein (MOG) and alphaB-crystallin did not differ between groups. There was a trend towards a decrease in IL-12 production in response to MBP and in vitro IL-12 secretion of SSPE patients to measles virus vaccine (MVV) was lower than controls. Proliferation, as well as IFN-gamma, IL-12 and IL-10 production in response to purified protein derivate (PPD) was impaired in SSPE patients. The results did not demonstrate any by-stander cellular response against myelin antigens, implicating that CNS is not a predominant target of an autoimmune response in SSPE. The recall responses were lower in SSPE as reported in measles before.

Immunity against vaccine-preventable potentially neurotropic diseases in children treated for malignant brain tumours with HIT-91 chemo- and radiotherapy

Following surgery, chemotherapy and/or irradiation, patients with malignant brain tumours are at risk of neurotropic diseases, although these are partly vaccine-preventable. In a retrospective, controlled, observational study, the impact of the German-Austrian chemo- and radiotherapy protocol (HIT-91) on antibody concentrations against vaccine-preventable diseases and on vaccination behaviour was analysed. A significant level of seronegativity for measles- and mumps-IgG, and a reduced protection induced by inactivated vaccines was observed after HIT-91 therapy. Failure of seroconversion following measles and mumps live vaccinations was assessed in the HIT-91-treated group and in a group with benign brain tumours (BBT). Analysis of cellular immunological parameters revealed significant aberrations in the HIT-91-treated group 36 months after completion of HIT-91 therapy. A retrospective analysis of the patient's vaccination history revealed an incorrect risk perception concerning the choice of vaccinations. We therefore recommend clinical vaccination with serosurveillance in patients who have undergone treatment for brain tumours.

Cytokine production patterns and antibody response to measles vaccine

Cytokines play an important role in the immune response to live measles virus immunization. To gain further insight into the cytokine production profile in response to measles vaccination, we studied interferon-gamma (IFN-gamma), tumor necrosis factor (TNF-alpha), soluble IL-2 receptor (sIL-2R), interleukin-2 (IL-2), interleukin-4 (IL-4), and interleukin-6 (IL-6) in both supernatants from peripheral blood mononuclear cells (PBMC) stimulated with phytohaemagglutinin (PHA), and plasma. We enrolled 57 healthy infants and children residing in an area where no measles virus circulated in their lifetimes. Overall analysis of cytokines in supernatants from PBMC showed that a predominant Th1 cytokine pattern occurs after the second dose of measles immunization. However, plasma levels of Th1 cytokines (IFN-gamma, sIL-2R and TNF-alpha) were preferentially activated by measles virus after the first dose of measles vaccination. Median IFN-gamma plasma levels were 1.73 pg/ml for infants compared to 0.63 pg/ml for older children (P = 0.003). These data suggest that after the first and the second dose of measles virus immunization, there is a predominant Th1-type directed immune response, but the Th1 cytokine pattern seems to be stronger in previously unvaccinated children. There was no correlation between cytokine production by PBMC supernatants after PHA stimulation and circulating levels of plasma cytokines. No relationship was found between any specific cytokine level and measles antibody level.

The effect of measles-mumps-rubella (MMR) immunization on the immune responses of previously immunized primary school children

Current policies for measles control call for administration of a second dose of vaccine to immunize those who failed to respond to the initial dose and to boost the responses of those with low levels of antibody. However, there has been concern expressed publicly that reimmunization may have adverse immunologic consequences. To determine the effects of reimmunization on immune responses, primary school children (N=38, mean age=6.14+/-0.35 years) with documented previous measles-mumps-rubella vaccine (MMR) immunization during infancy 4-5 years earlier were studied before and 1 month after receiving MMR as a part of routine reimmunization in Beer-Sheva, Israel. A substantial number of children were seronegative to measles (24%), mumps (34%) and rubella (44%). On reimmunization all seroconverted to mumps and rubella and all but one (92%) seroconverted to measles. The geometric mean titer of measles virus neutralizing antibody increased from 171 to 724 and the greatest increases occurred in those with the lowest pre-immunization titers. Moderate increases in levels of total IgM, IgG and IgE were detected in those with increases in antibody to measles virus. After reimmunization leukocyte counts decreased significantly from (5.8 x 10(6))+/-2.3 to (3.4 x 10(6))+/-0.7 ml(-1) (P=0.0001). The percentages of both CD4(+) and CD8(+) T cells decreased while the CD4:CD8 ratio remained unchanged. The percentage of CD56(+) natural killer (NK) cells increased from 5.2+/-2.7 to 7.2+/-2.8 (P=0.01). Functional assays showed improved lymphoproliferation in response to stimulation with phytohemagglutinin and tetanus toxoid and stable NK lytic activity. Therefore, reimmunization was accompanied by decreased leukocyte counts, but leukocyte function was unchanged or improved.

Immune responses to measles and measles vaccine: challenges for measles control

Most strategies for reducing global measles morbidity and mortality and eliminating measles are based on the ability to enhance immune responses to measles virus. Challenges to measles elimination and eradication are based in part on the need to sustain high levels of population immunity to interrupt transmission of measles virus. We review aspects of the immunology of measles and measles vaccination with the aim of demonstrating how knowledge of the immune responses is essential to furthering the goals of reducing measles morbidity and mortality and the elimination of measles. Better understanding of the mechanisms of immune suppression after measles, the potential for alternative vaccination strategies to induce immunity in young infants, and the immunologic basis of atypical measles, increased mortality after high-titer measles vaccine, and waning immunity will lead to improved strategies for measles control and elimination.

Addressing parents' concerns: do multiple vaccines overwhelm or weaken the infant's immune system?

Recent surveys found that an increasing number of parents are concerned that infants receive too many vaccines. Implicit in this concern is that the infant's immune system is inadequately developed to handle vaccines safely or that multiple vaccines may overwhelm the immune system. In this review, we will examine the following: 1) the ontogeny of the active immune response and the ability of neonates and young infants to respond to vaccines; 2) the theoretic capacity of an infant's immune system; 3) data that demonstrate that mild or moderate illness does not interfere with an infant's ability to generate protective immune responses to vaccines; 4) how infants respond to vaccines given in combination compared with the same vaccines given separately; 5) data showing that vaccinated children are not more likely to develop infections with other pathogens than unvaccinated children; and 6) the fact that infants actually encounter fewer antigens in vaccines today than they did 40 or 100 years ago.

Induction of cytokine mRNA in peripheral blood mononuclear cells of infants after the first dose of measles vaccine

To better characterize the cytokine response to measles virus vaccine, we examined the levels of IL-2, IL-4, IL-5, IL-10, IL-12 and gamma-interferon (gamma-IFN) in measles virus-stimulated peripheral blood mononuclear cells from 18 donors before and 2 weeks after vaccination. Donors were grouped as seropositive or seronegative on the basis of measles-specific IgM antibody present at 2 weeks postvaccination. After vaccination, similar levels of upregulation of IL-2 and gamma-IFN mRNA were observed in the two groups. The majority of donors in both groups did not exhibit an increase in measles specific IL-4 or IL-10 mRNA after vaccination. IL-12 mRNA was not induced by measles virus in any of the donors. A statistically significant upregulation of IL-5 mRNA was observed among seropositive (9/13) compared with seronegative (1/5) donors after vaccination (P=0.09, one tailed Fisher's test). The observed measles specific induction of IL-5 mRNA is suggestive of a possible association between IL-5 production and an antibody response to measles virus.

Safety of modified vaccinia virus Ankara (MVA) in immune-suppressed macaques

Modified vaccinia virus Ankara (MVA)-based recombinant viruses have been shown to be potent vaccine candidates for several infectious and neoplastic diseases. Since a major application of these live, replication-deficient vectors would be their use in immunocompromised or potentially immunocompromised individuals, a preclinical safety study was carried out. Macaques were inoculated with high doses of MVA (10(9)) via various routes, after immune-suppression by total-body irradiation, anti-thymocyte globulin treatment, or measles virus (MV) infection. No clinical, haematological or pathological abnormalities related to MVA inoculation were observed during a 13-day follow-up period. The presence of MVA genomes was demonstrated by nested PCR during the course of the experiment in all macaques, but from none of these animals replication competent MVA could be reisolated. These data suggest that MVA can safely be used as a basis for recombinant human vaccines, and that it is also safe for use in immunocompromised individuals.

Measles: immunosuppression, interleukin-12, and complement receptors

Measles virus, the first pathogen recognized to cause immunosuppression, induces profound and prolonged abnormalities in cellular immune responses in infected hosts. The ability of measles virus to specifically ablate monocyte/macrophage and dendritic cell production of interleukin (IL)-12 provides a potentially unifying mechanism for many of these in vivo and in vitro abnormalities. Cross-linking of the cellular receptor for measles virus, the complement regulatory protein CD46, is sufficient to inhibit IL-12 production. CD46-mediated downregulation of IL-12 has turned out to be a specific instance of a more general pattern of tight inhibitory control over IL-12 production effected by complement and phagocytic receptors on antigen-presenting cells. Exploitation of these pathways by other intracellular pathogens is likely.

Use of licensed vaccines for active immunization of the immunocompromised host

The latter part of the 20th century has witnessed an unprecedented rise in the number of individuals with impaired immunity. This is primarily attributable to the increased development and use of antineoplastic therapy for malignancies, organ and bone marrow transplantation, and the AIDS epidemic. Individuals with impaired immunity are often at increased risk for infections, and they can experience more severe and complicated courses of infection. The lack of therapy for a variety of viruses and the rise in antimicrobial resistance of many pathogens have focused attention on vaccination to prevent infectious diseases. The efficacy of most licensed vaccines has been established in immunocompetent hosts. However, there is also considerable experience with most vaccines in those with impaired immunity. We reviewed the use of licensed live, inactivated, and polysaccharide vaccines in this group, and several themes emerged: (i) most vaccines are less immunogenic in those with impaired immunity than in normal individuals; (ii) live vaccines are generally contraindicated in this group; and (iii) the efficacy of many commonly used vaccines has not been established in people with impaired immunity. This review suggests that for most vaccines there are little or no efficacy data in those with impaired immunity but their use in this patient group is generally safe.

Measles virus-induced immune suppression in the cotton rat (Sigmodon hispidus) model depends on viral glycoproteins

Immune suppression during measles accounts for most of the morbidity and mortality associated with the virus infection. Experimental study of this phenomenon has been hampered by the lack of a suitable animal model. We have used the cotton rat to demonstrate that mitogen-induced proliferation of spleen cells from measles virus-infected animals is impaired. Proliferation inhibition is seen in all lymphocyte subsets and is not dependent on viral replication. Cells which express the viral glycoproteins (hemagglutinin and fusion protein) transiently by transfection induce proliferation inhibition after intraperitoneal inoculation, whereas application of a recombinant measles virus in which measles virus glycoproteins are replaced with the vesicular stomatitis virus G protein does not have an antiproliferative effect. Therefore, in vivo expression of measles virus glycoproteins is sufficient and necessary to induce inhibition of lymphocyte proliferation.

Mechanism of suppression of cell-mediated immunity by measles virus

The mechanisms underlying the profound suppression of cell-mediated immunity (CMI) accompanying measles are unclear. Interleukin-12 (IL-12), derived principally from monocytes and macrophages, is critical for the generation of CMI. Measles virus (MV) infection of primary human monocytes specifically down-regulated IL-12 production. Cross-linking of CD46, a complement regulatory protein that is the cellular receptor for MV, with antibody or with the complement activation product C3b similarly inhibited monocyte IL-12 production, providing a plausible mechanism for MV-induced immunosuppression. CD46 provides a regulatory link between the complement system and cellular immune responses.

Immune responses during measles virus infection

The characteristic disease features of measles--fever and rash--are associated with the immune response to infection and are coincident with virus clearance. MV-specific antibody and CD4 and CD8 T cell responses are generated and contribute to virus clearance and protection from reinfection. During this same phase of immune activation immunologic abnormalities are also apparent. There is a generalized suppression of cellular immune responses that may contribute to increased susceptibility to other infections. Autoimmune disease may appear in the form of acute disseminated encephalomyelitis. If virus-specific immune responses are inadequate infection may progress with pulmonary or CNS manifestations, but without a rash. The pathogenesis of the rare disease SSPE, that occurs many years after primary infection is not clear, but immune responses show increased antibody to measles and cellular immune responses similar to those seen after uncomplicated infection.

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.

Early signal transduction in measles virus-infected lymphocytes is unaltered, but second messengers activate virus replication

In order to understand measles virus-lymphocyte interactions, we have started to analyze factors and events which regulate measles virus infection in peripheral blood mononuclear cells (PBMC). We analyzed the initiation of cell proliferation, induced by phytohemagglutinin, in infected and control PBMC by measuring intracellular free Ca2+ by using fura-2. Measles virus-infected and control PBMC responded similarly with an increase in the amount of cytosolic free Ca2+, indicating that the early activation events are not affected and are not involved in immunosuppression. The activation signals, Ca2+ and protein kinase C, induced specifically and independently by Ca ionophore A23187 or 12-O-tetradecanoylphorbol-13-acetate (TPA), changed the restricted measles virus infection to a productive one. The combination of TPA and A23187 was the most potent activator of measles virus replication. TPA and A23187 operate through different activation mechanisms, and it is evident that measles virus replication depends on the activation of cellular signal pathways. Depletion of adherent cells enhanced virus replication, especially at the early stage of infection, indicating the inhibitory role of monocytes. Monocytes were strongly infected, but they supported complete measles virus replication only at a very low level, and virus replication could not be enhanced with TPA and/or A23187.

Cytokine production in vitro and the lymphoproliferative defect of natural measles virus infection

In natural measles virus infection, evidence of intense immune system activation is present simultaneously with clinically relevant immune suppression. While evidence of activation is most prominent early in the disease, skin test responses and in vitro lymphoproliferation are depressed for weeks after the onset of the rash. It is not known whether the prolonged period of reduced immune responsiveness results from a single defect or a succession of different abnormalities. To gain further insight into measles-induced immune suppression we studied the production of soluble IL-2 receptor (sIL-2R), interferon-gamma (IFN-gamma), IL-1 beta, and tumor necrosis factor (TNF alpha) by peripheral blood mononuclear cells (PBMC) isolated from measles patients at various times after the onset of the rash. Studies included addition of supplemental recombinant IL-1 beta (rIL-1 beta) or recombinant IL-2 (rIL-2) or suppression of prostaglandin synthesis by indomethacin (IM). Proliferation in response to phytohemagglutin (PHA) was abnormal at all stages of disease. During the acute phase (first week after the onset of the rash) spontaneous production of sIL-2R was increased (76 +/- 54 vs. controls 4 +/- 4; P less than 0.03), suggesting in vivo T cell activation while PHA-induced sIL-2R was decreased (228 +/- 43 vs. control 582 +/- 127; P less than 0.002), suggesting that the capacity to produce IL-2 in response to mitogen was limited. Supplementation of PHA-stimulated cultures with rIL-2 improved but did not normalize both proliferation (58,600 +/- 4900 to 70,700 +/- 4400 vs. control 97,700 +/- 15,500; P less than 0.03) and sIL-2R levels (114 +/- 58 to 309 +/- 87 vs. control 582 +/- 127; P less than 0.003). Both spontaneous (25 +/- 18 vs. control 237 +/- 92; P less than 0.002) and PHA-induced (20 +/- 20 vs. control 604 +/- 129; P less than 0.004) TNF alpha levels were subnormal and were not improved with rIL-2, rIL-1 beta, or IM, suggesting a block in monocyte TNF alpha production. Spontaneous and PHA-induced IFN-gamma and IL-1 beta levels were normal. During the convalescent phase (greater than 2 weeks after the onset of the rash), spontaneous levels of sIL-2R were normal and PHA-induced levels were completely normalized with supplemental rIL-2 but proliferation remained below normal.(ABSTRACT TRUNCATED AT 400 WORDS)

Child mortality after high-titre measles vaccines: prospective study in Senegal

The use of Edmonston-Zagreb high-titre (EZ-HT) vaccine at age 6 months has been recommended for countries in which measles before the age of 9 months is a substantial cause of death, but little is known about the long-term effects of high-titre live measles vaccines given early in life. In a randomised vaccine trial in a rural area of Senegal, children were randomly assigned at birth to three vaccine groups: EZ-HT at 5 months (n = 336); Schwarz high-titre (SW-HT) at 5 months (n = 321); and placebo at 5 months followed by standard low-titre Schwarz vaccine at 10 months (standard: n = 358). All children were prospectively followed for 24-39 months in a well-established demographic surveillance system. Child mortality after immunisation was significantly higher in the two groups which received high-titre vaccines than in the group given the standard vaccine. The relative risk of death was 1.80 (95% confidence interval [CI] 1.18-2.74; p = 0.007) in the EZ-HT group and 1.51 (0.97-2.34; p = 0.07) in the SW-HT group compared with the standard group. The three vaccine groups were comparable as regards various social, family, and health characteristics, and there was no difference in mortality between children who received the standard vaccine and those who were eligible for the trial but did not take part for various reasons. The higher risk of death in the two high-titre vaccine groups remained significant in multivariate analyses. These findings suggest a need to reconsider the use of high-titre measles vaccines early in life in less developed countries.

The effects of long-term administration of recombinant alpha-2 interferon on lymphocyte subsets, proliferation, and suppressor cell function in multiple sclerosis

The immunological effects of long-term treatment with recombinant alpha-2 interferon (rIFN-alpha 2) were investigated in multiple sclerosis (MS) patients treated with 2 X 10(6) units of IFN or a placebo three times per week for one year. A mild lymphopenia was observed in IFN patients who also showed a decrease in the absolute number of total T cells in the blood (OKT3 binding cells); however, the percentage of cells reacting with OKT3, OKT4, and OKT8 antibodies did not change significantly during the study. The percentage of cells reacting with the Leu-7 antibody, which recognizes NK cells, was unchanged. During MS exacerbations, placebo patients showed a tendency for decreased levels of OKT3 and OKT8 cells. In contrast, IFN patients did not demonstrate a decrease in either OKT3 or OKT8 cells during disease attacks. Concanavalin A (ConA)-induced suppressor cell activity was depressed in both IFN and placebo-treated patients during attacks. Lymphoproliferative responses to phytohemagglutinin, pokeweed mitogen, and ConA were unchanged. These studies demonstrate that long-term treatment with rIFN-alpha 2 induces a generalized T-cell lymphopenia, but at this dose does not significantly affect the profiles of T-cell subsets and suppressor cell function in MS patients.

Virus-related pathology: is the continued presence of the virus necessary?

This chapter examines the effect of viruses in inducing modifications in chromosomes, immune system interactions, and cell metabolism to support such a hypothesis that virus may no longer be present when the pathology appears. When vaccines were available to protect the population against the major epidemics, then chronic, recurrent, or persistent infections came into focus. Viruses are everywhere and all organisms are permanently exposed to them. The result of this contact depends on the particular moment a t which a given cell is exposed to the virus. Rubella, for example, provokes a very benign disease in adults, but can induce abnormalities in the differentiating fetus. Although interferon is active against virus aggression, excess interferon has a toxic effect and can block differentiation. The capacity of several viruses to act as cellular mutagens by modifying chromosomes is well established, whatever the molecular mechanism may be. Mutations at the cellular level were carefully analyzed for their tumorigenic potential.

Viruses disrupt functions of human lymphocytes. Effects of measles virus and influenza virus on lymphocyte-mediated killing and antibody production

We present experimental data that offer, in part, a better understanding of the immunosuppression that accompanies measles virus infection. We note that measles virus "silently" infects human lymphocytes and that the infection does not alter lymphocyte survival in vitro. Yet such infected lymphocytes fail to generate natural killer (NK) cell activity or synthesize immunoglobulins (Ig). Thus, the presence of virus within lymphocytes impairs their specific immune functions in the absence of cytolysis. Influenza virus also infects human lymphocytes. In contrast to measles virus infection of resting lymphocytes in which viral antigen is rarely expressed, influenza virus infection of these cells yields viral antigens expressed in the cytoplasm and on the cell surface. Influenza virus-infected lymphocytes have normal NK cell activity but fail to synthesize IgG or IgM.

Cellular immune responses during complicated and uncomplicated measles virus infections of man

Lymphocytes from patients with measles showed profound and prolonged suppression of proliferative responses to mitogens. The degree of suppression was similar in patients with uncomplicated measles virus infection and in those with pneumonia or postinfectious encephalitis. Despite this suppression, lymphocyte responses to measles antigen and PPD were demonstrated in patients with encephalitis and uncomplicated disease, even early in infection. Most patients with pneumonia did not have demonstrable antigen-specific responses. The proportions of T helper (OKT 4) and T suppressor (OKT 8) cells and functional tests of Con A suppressor cell activity showed no significant difference between control and measles patients but, in contrast to controls, cells from measles patients cultured in the absence of any stimulant significantly suppressed the proliferation of allogeneic responder cells. Nine of 20 supernatant fluids from these cultures possessed a soluble suppressor factor. These studies indicate varied disruptions of immune reactivity during measles.

Measles encephalomyelitis--clinical and immunologic studies

We studied 19 patients with postinfectious encephalomyelitis complicating natural measles-virus infections, and our results support the hypothesis that this demyelinating disease has a pathogenesis similar to that of experimental allergic encephalomyelitis. Early myelin destruction was demonstrated by the presence of myelin basic protein in cerebrospinal fluid, and lymphocyte proliferative responses to myelin basic protein were found in 8 of 17 patients tested. A lack of intrathecal synthesis of antibody against measles virus suggests that measles encephalomyelitis may not be dependent on virus replication within the central nervous system. Similar lymphoproliferative responses to myelin basic protein of lymphocytes from single patients with encephalomyelitis after rabies vaccine or after varicella or rubella virus infections suggest a common immune-mediated pathogenesis for the perivenular demyelinating disease that can follow the injection of neural tissues or infection by a variety of viruses.

T-lymphocyte subpopulations in relation to immunosuppression in measles and varicella

Patients with measles or varicella were studied during the acute phase (first week) of illness and, after recovery, by lymphocyte stimulation tests and determination of T-lymphocyte subpopulations, using the monoclonal antibodies Leu 2a and Leu 3a directed at the suppressor/cytotoxic and the helper T-cell subsets, respectively. Low proliferative responses to phytohemagglutinin were found during the acute phase of both diseases. The response to purified protein derivate of tuberculin was also low in all measles patients tested and in some of the varicella patients. In both infections increased spontaneous DNA synthesis was demonstrated. In the acute phase of measles there was T lymphocytopenia but no change of the ratio between T lymphocytes of helper and suppressor/cytotoxic cell phenotypes. In the acute phase of varicella the percentage and the absolute number of Leu 2-positive (suppressor/cytotoxic) T cells were increased. Measurement of the size of the lymphocytes indicated activation of this subset. Cryopreserved blood mononuclear cells from the acute phase of varicella could suppress the phytohemagglutinin response of autologous convalescent-phase cells. This was not seen when cells from measles patients were tested. The suppression of the lymphocyte stimulation response in varicella is probably in part caused by activation of suppressor cells, whereas the suppression of the stimulation response in measles seems to be due mainly to other mechanisms.