Measles virus suppresses cell-mediated immunity by interfering with the survival and functions of dendritic and T cells

Secondary infections due to a marked immunosuppression have long been recognized as a major cause of the high morbidity and mortality rate associated with acute measles. The mechanisms underlying the inhibition of cell-mediated immunity are not clearly understood but dysfunctions of monocytes as antigen-presenting cells (APC) are implicated. In this report, we demonstrate that measles virus (MV) replicates weakly in the resting dendritic cells (DC) as in lipopolysaccharide-activated monocytes, but intensively in CD40-activated DC. The interaction of MV-infected DC with T cells not only induces syncytia formation where MV undergoes massive replication, but also leads to an impairment of DC and T cell function and cell death. CD40-activated DC decrease their capacity to produce interleukin (IL) 12, and T cells are unable to proliferate in response to MV-infected DC stimulation. A massive apoptosis of both DC and T cells is observed in the MV pulsed DC-T cell cocultures. This study suggests that DC represent a major target of MV. The enhanced MV replication during DC-T cell interaction, leading to an IL-12 production decrease and the deletion of DC and T cells, may be the essential mechanism of immunosuppression induced by MV.

Viral pneumonias in adults: radiologic and pathologic findings

Numerous viruses, including influenza virus, measles virus, Hantavirus, adenovirus, herpesviruses, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus, can cause lower respiratory tract infection in adults. Viral pneumonia in adults can be classified into two clinical groups: so-called atypical pneumonia in otherwise healthy hosts and viral pneumonia in immunocompromised hosts. Influenza virus types A and B cause most cases of viral pneumonia in immunocompetent adults. Immunocompromised hosts are susceptible to pneumonias caused by cytomegalovirus, herpesviruses, measles virus, and adenovirus. The radiographic findings, which consist mainly of patchy or diffuse ground-glass opacity with or without consolidation and reticular areas of increased opacity, are variable and overlapping. Computed tomographic findings, which are also overlapping, consist of poorly defined centrilobular nodules, ground-glass attenuation with a lobular distribution, segmental consolidation, or diffuse ground-glass attenuation with thickened interlobular septa. The radiologic findings reflect the variable extents of the histopathologic features: diffuse alveolar damage (intraalveolar edema, fibrin, and variable cellular infiltrates with a hyaline membrane), intraalveolar hemorrhage, and interstitial (intrapulmonary or airway) inflammatory cell infiltration. Clinical information such as patient age, immune status, community outbreaks, symptom onset and duration, and presence of a rash remain important aids in diagnosis of viral causes.

Measles virus infects human dendritic cells and blocks their allostimulatory properties for CD4+ T cells

Measles causes a profound immune suppression which is responsible for the high morbidity and mortality induced by secondary infections. Dendritic cells (DC) are professional antigen-presenting cells required for initiation of primary immune responses. To determine whether infection of DC by measles virus (MV) may play a role in virus-induced suppression of cell-mediated immunity, we examined the ability of CD1a+ DC derived from cord blood CD34+ progenitors and Langerhans cells isolated from human epidermis to support MV replication. Here we show that both cultured CD1a+ DC and epidermal Langerhans cells can be infected in vitro by both vaccine and wild type strains of MV. DC infection with MV resulted within 24-48 h in cell-cell fusion, cell surface expression of hemagglutinin, and virus budding associated with production of infectious virus. MV infection of DC completely abrogated the ability of the cells to stimulate the proliferation of naive allogeneic CD4+ T cell as early as day 2 of mixed leukocyte reaction (MLR) (i.e., on day 4 of DC infection). Mannose receptor-mediated endocytosis and viability studies indicated that the loss of DC stimulatory function could not be attributed to the death or apoptosis of DC. This total loss of DC stimulatory function required viral replication in the DC since ultraviolet (UV)-inactivated MV or UV-treated supernatant from MV-infected DC did not alter the allostimulatory capacity of DC. As few as 10 MV- infected DC could block the stimulatory function of 10(4) uninfected DC. More importantly, MV-infected DC, in which production of infectious virus was blocked by UV treatment or paraformaldehyde fixation, actively suppressed allogeneic MLR upon transfer to uninfected DC-T-cultures. Thus, the mechanisms which contribute to the loss of the allostimulatory function of DC include both virus release and active suppression mediated by MV-infected DC, independent of virus production. These data suggest that carriage of MV by DC may facilitate virus spreading to secondary lymphoid organs and that MV replication in DC may play a central role in the general immune suppression observed during measles.

Measles virus: cellular receptors, tropism and pathogenesis

Measles virus(MV), a member of the genusMorbillivirusin the familyParamyxoviridae, is an enveloped virus with a non-segmented, negative-strand RNA genome. It has two envelope glycoproteins, the haemagglutinin (H) and fusion proteins, which are responsible for attachment and membrane fusion, respectively. Human signalling lymphocyte activation molecule (SLAM; also called CD150), a membrane glycoprotein of the immunoglobulin superfamily, acts as a cellular receptor for MV. SLAM is expressed on immature thymocytes, activated lymphocytes, macrophages and dendritic cells and regulates production of interleukin (IL)-4 and IL-13 by CD4+T cells, as well as production of IL-12, tumour necrosis factor alpha and nitric oxide by macrophages. The distribution of SLAM is in accord with the lymphotropism and immunosuppressive nature of MV.Canine distemper virusandRinderpest virus, other members of the genusMorbillivirus, also use canine and bovine SLAM as receptors, respectively. Laboratory-adapted MV strains may use the ubiquitously expressed CD46, a complement-regulatory molecule, as an alternative receptor through amino acid substitutions in the H protein. Furthermore, MV can infect SLAM−cells, albeit inefficiently, via the SLAM- and CD46-independent pathway, which may account for MV infection of epithelial, endothelial and neuronal cellsin vivo. MV infection, however, is not determined entirely by the H protein–receptor interaction, and other MV proteins can also contribute to its efficient growth by facilitating virus replication at post-entry steps. Identification of SLAM as the principal receptor for MV has provided us with an important clue for better understanding of MV tropism and pathogenesis.

Altered transcription of a defective measles virus genome derived from a diseased human brain

Measles virus (MV) is a negative strand RNA virus which usually causes acute disease, but in rare cases its persistence in the human brain induces the lethal disease subacute sclerosing panencephalitis (SSPE). The transcription of MV and of a defective MV derived from autopsy material of a SSPE case was studied in cultured cells. In the lytic infection the levels of the MV mRNAs decreased progressively with the distance of the six cognate genes from the 3' end of the genome, reflecting transcriptional attenuation at every gene junction. Transcripts covering two or three adjacent genes accounted for up to 20% of single gene transcripts; incidentally the MV intergenic transcription signals were found to be less conserved than the analogous signals of other negative strand RNA viruses. Although the analysed SSPE-derived defective MV showed a localized transcription defect at the phosphoprotein--matrix gene junction (substitution of the mRNAs by readthrough transcripts), the corresponding intergenic 'consensus' sequence and the surrounding nucleotides were not altered. This implies that factor(s) involved in the transcription of this defective SSPE virus fail to recognize this particular signal sequence, a constellation which in this and other cases might be causally related to the development of MV persistence.

Production of atypical measles in rhesus macaques: evidence for disease mediated by immune complex formation and eosinophils in the presence of fusion-inhibiting antibody

The severe disease atypical measles occurred when individuals immunized with a poorly protective inactivated vaccine contracted measles, and was postulated to be due to a lack of fusion-inhibiting antibodies. Here, rhesus macaques immunized with formalin-inactivated measles vaccine developed transient neutralizing and fusion-inhibiting antibodies, but no cytotoxic T-cell response. Subsequent infection with measles virus caused an atypical rash and pneumonitis, accompanied by immune complex deposition and an increase in eosinophils. Fusion-inhibiting antibody appeared earlier in these monkeys than in non-immunized monkeys. These data indicate that atypical measles results from previous priming for a nonprotective type 2 CD4 T-cell response rather than from lack of functional antibody against the fusion protein.

Experimental measles. I. Pathogenesis in the normal and the immunized host

An animal model to study measles pathogenesis and the correlates of protective immunity was established using rhesus monkeys. A measles isolate, obtained during an epidemic of measles in the primate colony at the University of California, Davis, was passaged through rhesus monkeys and amplified in rhesus mononuclear cells to create a pathogenic virus stock. Sequence analysis of the nucleoprotein and hemagglutinin genes of this isolate revealed strong homology with the Chicago 89 strain of measles virus. Conjunctival/intranasal inoculation of juvenile rhesus monkeys with this virus resulted in skin rash, pneumonia, and systemic infection with dissemination to other mucosal sites and to the lymphoid tissues. Inflammation and necrosis occurred in the lungs and lymphoid tissues and many cell types were infected with measles virus on Day 7 postinoculation (p.i.). The most commonly infected cell type was the B lymphocyte in lymphoid follicles. Measles antigen was found in follicular dendritic cells on Day 14 p.i. In contrast to naive monkeys infected with measles virus, animals vaccinated with the attenuated Moraten strain did not develop clinical or pathologic signs of measles after challenge. However, moderate to marked hyperplasia occurred in the lymph nodes and spleen of a vaccinated animal on Day 7 after pathogenic virus challenge, suggesting that an effective measles vaccine limits but does not prevent infection with wild-type measles virus.

Subacute sclerosing panencephalitis: propagation of measles virus from brain biopsy in tissue culture

Measles virus was propagated in monolayer cultures established from brain tissue of a patient with subacute sclerosing panencephalitis. Syncytial cells were rendered fluorescent with measles specific antiserums only, by means of an indirect technique. The ultrastructural appearance of the microtubular aggregates was identical in brain tissue and in the cultured cells. Fusion experiments produced a cytopathic effect in humnan embryonic kidney and VERO cell cultures. The virus was identified by hemiagglutination-inhibition, but only in the supernatant of disrupted cultured cells.

Virucidal activity of a scorpion venom peptide variant mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses

Outbreaks of SARS-CoV, influenza A (H5N1, H1N1) and measles viruses in recent years have raised serious concerns about the measures available to control emerging and re-emerging infectious viral diseases. Effective antiviral agents are lacking that specifically target RNA viruses such as measles, SARS-CoV and influenza H5N1 viruses, and available vaccinations have demonstrated variable efficacy. Therefore, the development of novel antiviral agents is needed to close the vaccination gap and silence outbreaks. We previously identified mucroporin, a cationic host defense peptide from scorpion venom, which can effectively inhibit standard bacteria. The optimized mucroporin-M1 can inhibit gram-positive bacteria at low concentrations and antibiotic-resistant pathogens. In this investigation, we further tested mucroporin and the optimized mucroporin-M1 for their antiviral activity. Surprisingly, we found that the antiviral activities of mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses were notably increased with an EC₅₀ of 7.15 μg/ml (3.52 μM) and a CC₅₀ of 70.46 μg/ml (34.70 μM) against measles virus, an EC₅₀ of 14.46 μg/ml (7.12 μM) against SARS-CoV and an EC₅₀ of 2.10 μg/ml (1.03 μM) against H5N1, while the original peptide mucroporin showed no antiviral activity against any of these three viruses. The inhibition model could be via a direct interaction with the virus envelope, thereby decreasing the infectivity of virus. This report provides evidence that host defense peptides from scorpion venom can be modified for antiviral activity by rational design and represents a practical approach for developing broad-spectrum antiviral agents, especially against RNA viruses.

An immunohistochemical study of the distribution of the measles virus receptors, CD46 and SLAM, in normal human tissues and subacute sclerosing panencephalitis

We have compared the expression of the known measles virus (MV) receptors, membrane cofactor protein (CD46) and the signaling lymphocyte-activation molecule (SLAM), using immunohistochemistry, in a range of normal peripheral tissues (known to be infected by MV) as well as in normal and subacute sclerosing panencephalitis (SSPE) brain. To increase our understanding of how these receptors could be utilized by wild-type or vaccine strains in vivo, the results have been considered with regard to the known route of infection and systemic spread of MV. Strong staining for CD46 was observed in endothelial cells lining blood vessels and in epithelial cells and tissue macrophages in a wide range of peripheral tissues, as well as in Langerhans' and squamous cells in the skin. In lymphoid tissues and blood, subsets of cells were positive for SLAM, in comparison to CD46, which stained all nucleated cell types. Strong CD46 staining was observed on cerebral endothelium throughout the brain and also on ependymal cells lining the ventricles and choroid plexus. Comparatively weaker CD46 staining was observed on subsets of neurons and oligodendrocytes. In SSPE brain sections, the areas distant from lesion sites and negative for MV by immunocytochemistry showed the same distribution for CD46 as in normal brain. However, cells in lesions, positive for MV, were negative for CD46. Normal brain showed no staining for SLAM, and in SSPE brain only subsets of leukocytes in inflammatory infiltrates were positive. None of the cell types most commonly infected by MV show detectable expression of SLAM, whereas CD46 is much more widely expressed and could fulfill a receptor function for some wild-type strains. In the case of wild-type stains, which are unable to use CD46, a further as yet unknown receptor(s) would be necessary to fully explain the pathology of MV infection.

Sustained autophagy contributes to measles virus infectivity

The interplay between autophagy and intracellular pathogens is intricate as autophagy is an essential cellular response to fight against infections, whereas numerous microbes have developed strategies to escape this process or even exploit it to their own benefit. The fine tuned timing and/or selective molecular pathways involved in the induction of autophagy upon infections could be the cornerstone allowing cells to either control intracellular pathogens, or be invaded by them. We report here that measles virus infection induces successive autophagy signallings in permissive cells, via distinct and uncoupled molecular pathways. Immediately upon infection, attenuated measles virus induces a first transient wave of autophagy, via a pathway involving its cellular receptor CD46 and the scaffold protein GOPC. Soon after infection, a new autophagy signalling is initiated which requires viral replication and the expression of the non-structural measles virus protein C. Strikingly, this second autophagy signalling can be sustained overtime within infected cells, independently of the expression of C, but via a third autophagy input resulting from cell-cell fusion and the formation of syncytia. Whereas this sustained autophagy signalling leads to the autophagy degradation of cellular contents, viral proteins escape from degradation. Furthermore, this autophagy flux is ultimately exploited by measles virus to limit the death of infected cells and to improve viral particle formation. Whereas CD150 dependent virulent strains of measles virus are unable to induce the early CD46/GOPC dependent autophagy wave, they induce and exploit the late and sustained autophagy. Overall, our work describes distinct molecular pathways for an induction of self-beneficial sustained autophagy by measles virus.

Autophagy is an evolutionarily conserved lysosomal dependent degradative pathway for recycling of long-lived proteins and damaged organelles. Autophagy is also an essential cellular response to fight infection by destroying infectious pathogens trapped within autophagosomes and plays a key role in the induction of both innate and adaptive immune responses. Numerous viruses have evolved strategies to counteract autophagy in order to escape from degradation or/and to inhibit immune signals. The kinetic and molecular pathways involved in the induction of autophagy upon infections might determine if cells would be able to control pathogens or would be invaded by them. We showed that measles virus (MeV) infection induces successive autophagy signallings in cells via distinct molecular pathways. A first autophagy wave is induced by the engagement of the MeV cellular receptor CD46 and the scaffold protein GOPC. A second wave is initiated after viral replication by the expression of the non-structural MeV protein C and is sustained overtime within infected cells thanks to the formation of syncytia. This sustained autophagy is exploited by MeV to limit the death of infected cells and to improve viral particle formation. We describe new molecular pathways by which MeV hijacks autophagy to promote its infectivity.

Role of CD8(+) lymphocytes in control and clearance of measles virus infection of rhesus monkeys

The creation of an improved vaccine for global measles control will require an understanding of the immune mechanisms of measles virus containment. To assess the role of CD8(+) cytotoxic T lymphocytes in measles virus clearance, rhesus monkeys were depleted of CD8(+) lymphocytes by monoclonal anti-CD8 antibody infusion and challenged with wild-type measles virus. The CD8(+) lymphocyte-depleted animals exhibited a more extensive rash, higher viral loads at the peak of virus replication, and a longer duration of viremia than did the control antibody-treated animals. These findings indicate a central role for CD8(+) lymphocytes in the control of measles virus infections and the importance of eliciting a cell-mediated immune response in new measles vaccine strategies.

Lymphatic dissemination and comparative pathology of recombinant measles viruses in genetically modified mice

The dissemination of the Edmonston measles virus (Ed-MV) vaccine strain was studied with genetically modified mice defective for the alpha/beta interferon receptor and expressing human CD46 with human-like tissue specificity and efficiency. A few days after intranasal infection, macrophages expressing Ed-MV RNA were detected in the lungs, in draining lymph nodes, and in the thymus. In lymph nodes, large syncytia which stained positive for viral RNA and for macrophage surface marker proteins were found and apoptotic cell death was monitored. In the thymus, smaller syncytia which stained positive for macrophage and dendritic cell markers were detected. Thus, macrophages appear to be the main vectors for dissemination of MV infection in these mice; human macrophages may have a similar function in the natural host. We then compared the pathogenicities of two recombinant viruses lacking the C or V nonstructural proteins to that of the parental strain, Ed-MV. These viruses were less effective in spreading through the lymphatic system and, unlike Ed-MV, were not detected in the liver. After intracerebral inoculation the recombinant viruses caused lethal disease less often than Ed-MV and induced distinctive patterns of gliosis and inflammation. Ed-MV was reisolated from brain tissue, but its derivatives were not. C- and V-defective viruses should be considered as more-attenuated MV vaccine candidates.

The Immune Response in Measles: Virus Control, Clearance and Protective Immunity

Measles is an acute systemic viral infection with immune system interactions that play essential roles in multiple stages of infection and disease. Measles virus (MeV) infection does not induce type 1 interferons, but leads to production of cytokines and chemokines associated with nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) signaling and activation of the NACHT, LRR and PYD domains-containing protein (NLRP3) inflammasome. This restricted response allows extensive virus replication and spread during a clinically silent latent period of 10–14 days. The first appearance of the disease is a 2–3 day prodrome of fever, runny nose, cough, and conjunctivitis that is followed by a characteristic maculopapular rash that spreads from the face and trunk to the extremities. The rash is a manifestation of the MeV-specific type 1 CD4⁺ and CD8⁺ T cell adaptive immune response with lymphocyte infiltration into tissue sites of MeV replication and coincides with clearance of infectious virus. However, clearance of viral RNA from blood and tissues occurs over weeks to months after resolution of the rash and is associated with a period of immunosuppression. However, during viral RNA clearance, MeV-specific antibody also matures in type and avidity and T cell functions evolve from type 1 to type 2 and 17 responses that promote B cell development. Recovery is associated with sustained levels of neutralizing antibody and life-long protective immunity.

An Immunocompetent Murine Model for Oncolysis with an Armed and Targeted Measles Virus

An immunocompetent model is required to test therapeutic regimens for clinical trials with the oncolytic measles virus (MV). Toward developing this model, a retargeted MV that enters murine colon adenocarcinoma cells forming tumors in syngeneic C57BL/6 mice was generated. Since MV infection tends to be less efficient in murine than in human cells, the targeted virus was also armed with the prodrug convertase, purine nucleoside phosphorylase (PNP), and named MV-PNP-antiCEA. We have shown before that in cultured cells, infection with this virus activated the prodrug, 6-methylpurine-2'-deoxyriboside (MeP-dR), causing extensive cytotoxicity. When injected intratumorally (IT), MV-PNP-antiCEA inhibited subcutaneous tumor growth marginally, but subsequent administration of the prodrug enhanced the oncolytic effect. Systemic delivery of MV-PNP-antiCEA alone had no substantial oncolytic effects, but in combination with the prodrug it was therapeutic, revealing synergistic effects between virus and prodrug. Immunosuppression with cyclophosphamide (CPA) retarded the appearance of MV neutralizing antibodies and enhanced oncolytic efficacy: survival was 100%, with 9 out of 10 animals going into complete remission. This immunocompetent murine model facilitates the testing of therapeutic regimens for clinical trials.

Virological aspects of measles virus-induced encephalomyelitis in Lewis and BN rats

Lewis and Brown Norway (BN) rats which are susceptible or resistant to autoimmune reactions against brain antigen, respectively, were inoculated intracerebrally with a neurotropic measles virus. Suckling rats died from a rapidly fatal acute encephalopathy (AE). With increasing age Lewis rats developed a subacute measles encephalomyelitis (SAME) whereas BN rats showed a clinically silent encephalitis (CSE). Infectious virus could occasionally be recovered from SAME animals using cocultivation techniques but not from BN rats with CSE. With monoclonal antibodies against measles virus, viral proteins were localized in brain tissue. Nucleocapsid and phosphoprotein were detected in infected brain cells of all animals with AE, SAME and CSE, whereas measles virus haemagglutinin, fusion and matrix proteins were either reduced or absent, suggesting a restricted synthesis of measles virus envelope proteins. These data suggest that the different diseases of the two rat strains are related to the immunogenetic background rather than to the replication of measles virus in the central nervous system. This animal model provides the opportunity to investigate further the events occurring during establishment of measles virus persistence in the brain, and the genetic control of associated immunological and immunopathological reactions.

Measles rash. I. Light and electron microscopic study of skin eruptions

Measles skin lesions were studied by light and electron microscopy. In the epidermis multinucleated giant cells were observed just beneath the hypertrophic horney layer at the maximum stage of rash; they were believed to result by an abnormal process of hyper- or parakeratosis. Neither typical inclusions nor viral nucleocapsids could be detected in any part of the epidermal layer. Most characteristical changes were dermal edema and spongiosis with mononuclear cell infiltration as well as the detection of measle virus-like microtubular structures (nucleocapsids) in the endothelium of dermal capillaries. Is is assumed that measles exanthema is a manifestation of an Arthus reaction elicited by viral antigen in the endothelium of dermal capillaries.

Disseminated measles infection after vaccination in a child with a congenital immunodeficiency

An infant boy with a congenital immunodeficiency had fatal disseminated measles after administration of a live attenuated measles vaccine. This rare complication was confirmed with molecular virologic techniques. Although efforts to expand availability of vaccinations are critically important, caution is warranted in children with potentially severe immunologic dysfunction.

Pathology of measles in rhesus monkeys

Skin biopsies were taken from 16 monkeys with measles rash. Histopathological changes consisted of multinucleated epithelial giant cells in the epidermis and hair follicles, proliferative and degenerative changes of the epidermis, and mild inflammation of the dermis. Necropsies were performed on two monkeys with a typical rash and on 26 additional monkeys that died during outbreaks in the colony. Lesions attributable to rubeola virus were found in the respiratory system, lymphoid system, gastrointestinal tract, salivary glands, thyroid gland, liver, pancreas, and urinary system. In these organs the finding that was characteristic of measles was the presence of syncytial giant cells, some of which contained both intranuclear and cytoplasmic inclusions. The significance of syncytia and the mechanism of their formation are discussed.

The H gene of rodent brain-adapted measles virus confers neurovirulence to the Edmonston vaccine strain

Molecular determinants of neuropathogenesis have been shown to be present in the hemagglutinin (H) protein of measles virus (MV). An H gene insertion vector has been generated from the Edmonston B vaccine full-length infectious clone of MV. Using this vector, it is possible to insert complete H open reading frames into the parental (Edtag) background. The H gene from a rodent brain-adapted MV strain (CAM/RB) was inserted into this vector, and a recombinant virus (EdtagCAMH) was rescued by using a modified vaccinia virus which expresses T7 RNA polymerase (MVA-T7). The recombinant virus grew at an equivalent rate and to similar titers as the CAM/RB and Edtag parental viruses. Neurovirulence was assayed in a mouse model for MV encephalitis. Viruses were injected intracerebrally into the right cortex of C57/BL/6 suckling mice. After infection mice inoculated with the CAM/RB strain developed hind limb paralysis and ataxia. Clinical symptoms were never observed with an equivalent dose of Edtag virus or in sham infections. Immunohistochemistry (IHC) was used to detect viral antigen in formalin-fixed brain sections. Measles antigen was observed in neurons and neuronal processes of the hippocampus, frontal, temporal, and olfactory cortices and neostriatum on both sides of symmetrical structures. Viral antigen was not detected in mice infected with Edtag virus. Mice infected with the recombinant virus, EdtagCAMH, became clinically ill, and virus was detected by IHC in regions of the brain similar to those in which it was detected in animals infected with CAM/RB. The EdtagCAMH infection had, however, progressed much less than the CAM/RB virus at 4 days postinfection. It therefore appears that additional determinants are encoded in other regions of the MV genome which are required for full neurovirulence equivalent to CAM/RB. Nevertheless, replacement of the H gene alone is sufficient to cause neuropathology.