Impact of measles virus dendritic-cell infection on Th-cell polarization in vitro

Cytokine imbalance after measles virus infection has no correlation with immune suppression

Measles virus infection leads to immune suppression. A potential mechanism is the reduction of interleukin 12 (IL-12) secretion during acute measles, resulting in a TH2 response. Studies in humans have reported conflicting results, detecting either a TH2 or a TH1 response. We have investigated the correlation between a TH2 response and immune suppression in specific-pathogen-free inbred cotton rats which were infected with measles vaccine and wild-type viruses. After infection of bone marrow-derived macrophages with wild-type virus, IL-12 secretion was reduced in contrast to the level for vaccine virus infection. In bronchoalveolar lavage cells, IL-12 secretion was suppressed after infection with both wild-type and vaccine virus on days 2, 4, and 6 and was detectable on days 8 and 10. After stimulation of mediastinal lymph node and spleen cells with UV-inactivated measles virus at various time points after infection, gamma interferon but no IL-4 was found. After stimulation with phorbol myristate acetate-ionomycin, high gamma interferon and low IL-4 levels were detected. To investigate whether the secretion of IL-4 contributes to immune suppression, a recombinant vaccine virus was created which secretes cotton rat IL-4. After infection with this recombinant virus, IL-4 secretion was enhanced. However, neither inhibition of concanavalin A-stimulated spleen cells nor keyhole limpet hemocyanin-specific proliferation of spleen cells was altered after infection with the recombinant virus in comparison to the levels with the parental virus. Our data indicate that measles virus infection leads to a decrease in IL-12 secretion and an increase in IL-4 secretion, but this does not seem to correlate with immune suppression.

Measles virus modulates chemokine release and chemotactic responses of dendritic cells

Interference with dendritic cell (DC) maturation and function is considered to be central to measles virus (MV)-induced immunosuppression. Temporally ordered production of chemokines and switches in chemokine receptor expression are essential for pathogen-driven DC maturation as they are prerequisites for chemotaxis and T cell recruitment. We found that MV infection of immature monocyte-derived DCs induced transcripts specific for CCL-1, -2, -3, -5, -17 and -22, CXCL-10 and CXCL-11, yet did not induce CXCL-8 (interleukin-8) and CCL-20 at the mRNA and protein level. Within 24 h post-infection, T cell attraction was not detectably impaired by these cells. MV infection failed to promote the switch from CCR5 to CCR7 expression and this correlated with chemotactic responses of MV-matured DC cultures to CCL-3 rather than to CCL-19. Moreover, the chemotaxis of MV-infected DCs to either chemokine was compromised, indicating that MV also interferes with this property independently of chemokine receptor modulation.

Measles virus-induced immunosuppression

Immunosuppression is the major cause of infant death associated with acute measles and therefore of substantial clinical importance. Major hallmarks of this generalized modulation of immune functions are (1) lymphopenia, (2) a prolonged cytokine imbalance consistent with suppression of cellular immunity to secondary infections, and (3) silencing of peripheral blood lymphocytes, which cannot expand in response to ex vivo stimulation. Lymphopenia results from depletion, which can occur basically at any stage of lymphocyte development, and evidently, expression of the major MV receptor CD150 plays an important role in targeting these cells. Virus transfer to T cells is thought to be mediated by dendritic cells (DCs), which are considered central to the induction of T cell silencing and functional skewing. As a consequence of MV interaction, viability and functional differentiation of DCs and thereby their expression pattern of co-stimulatory molecules and soluble mediators are modulated. Moreover, MV proteins expressed by these cells actively silence T cells by interfering with signaling pathways essential for T cell activation.

Lack of association between measles virus vaccine and autism with enteropathy: a case-control study

Background

The presence of measles virus (MV) RNA in bowel tissue from children with autism spectrum disorders (ASD) and gastrointestinal (GI) disturbances was reported in 1998. Subsequent investigations found no associations between MV exposure and ASD but did not test for the presence of MV RNA in bowel or focus on children with ASD and GI disturbances. Failure to replicate the original study design may contribute to continued public concern with respect to the safety of the measles, mumps, and rubella (MMR) vaccine.

Methodology/Principal Findings

The objective of this case-control study was to determine whether children with GI disturbances and autism are more likely than children with GI disturbances alone to have MV RNA and/or inflammation in bowel tissues and if autism and/or GI episode onset relate temporally to receipt of MMR. The sample was an age-matched group of US children undergoing clinically-indicated ileocolonoscopy. Ileal and cecal tissues from 25 children with autism and GI disturbances and 13 children with GI disturbances alone (controls) were evaluated by real-time reverse transcription (RT)-PCR for presence of MV RNA in three laboratories blinded to diagnosis, including one wherein the original findings suggesting a link between MV and ASD were reported. The temporal order of onset of GI episodes and autism relative to timing of MMR administration was examined. We found no differences between case and control groups in the presence of MV RNA in ileum and cecum. Results were consistent across the three laboratory sites. GI symptom and autism onset were unrelated to MMR timing. Eighty-eight percent of ASD cases had behavioral regression.

Conclusions/Significance

This study provides strong evidence against association of autism with persistent MV RNA in the GI tract or MMR exposure. Autism with GI disturbances is associated with elevated rates of regression in language or other skills and may represent an endophenotype distinct from other ASD.

Differential response of human naive and memory/effector T cells to dendritic cells infected by respiratory syncytial virus

In vitro studies have contributed substantially to the understanding of immunopathology of respiratory syncytial virus (RSV)-mediated disease. In the present study we compared the effect of RSV-infected dendritic cells on the time-course of the primary and memory/effector T cell response in vitro. Cultures with uninfected dendritic cells known to elicit T helper 2 (Th2) responses and with polyinosinic-polycytidylic acid (poly-IC)-stimulated dendritic cells known to elicit Th1 responses served as controls. At day 1 after stimulation there was a high proportion of interleukin (IL)-2 and tumour necrosis factor (TNF)-alpha-producing T cells with no difference in number of producing T cells as well as concentration of secreted cytokines between RSV-infected and control cultures. However, up to day 3 generation of IFN-gamma was reduced markedly. In addition, there was a reduced proliferation in RSV cultures. At day 7 the RSV-treated cultures showed a preponderance of IL-4 generation. At days 21-24, after three rounds of restimulation, memory/effector T cells matured under the influence of RSV were still not fully polarized but in contrast to the primary response displayed a predominance of Th1 cytokines. Contact with RSV-infected HEp-2 cells inhibited proliferation of T cells; memory effector T cells were less sensitive to contact inhibition than naive T cells. In addition, RSV inhibited the stimulated rearrangement of cortical actin more effectively in naive compared to memory T cells. In summary, we have shown that RSV infection of dendritic cells has a distinct modulatory effect on the primary response and a less pronounced effect on the memory response.

Immune synapses formed with measles virus-infected dendritic cells are unstable and fail to sustain T cell activation

Interaction with dendritic cells (DCs) is considered as central to immunosuppression induced by viruses, including measles virus (MV). Commonly, viral infection of DCs abrogates their ability to promote T cell expansion, yet underlying mechanisms at a cellular level are undefined. We found that MV-infected DCs only subtly differed from LPS-matured with regard to integrin activation, acquisition of a migratory phenotype and motility. Similarly, the organization of MV-DC/T cell interfaces was consistent with that of functional immune synapses with regard to CD3 clustering and MHC class II surface recruitment. The majority of MV-DC/T cell conjugates was, however, unstable and only promoted abortive T cell activation. Thus, MV-infected DCs retain activities required for initiating, but not sustaining T cell conjugation and activation. This is partially rescued if surface expression of the MV glycoproteins on DCs is abolished by infection with a recombinant MV encoding VSV G protein instead, indicating that these contribute directly to synapse destabilization and thereby act as effectors of T cell inhibition.

Transduction with a fiber-modified adenoviral vector is superior to non-viral nucleofection for expressing tumor-associated Ag mucin-1 in human DC

BACKGROUND

DC-presenting tumor Ag are currently being developed to be used as a vaccine in human cancer immunotherapy. To increase the chances for successful therapy it is important to deliver full-length tumor Ag instead of loading single peptides. Methodologically, several recombinant DNA delivery techniques have been used.

METHODS

In this study we compared nucleofection, an optimized form of electroporation, and adenoviral transduction regarding their efficiency to transduce human monocyte-derived (Mo-) DC in vitro. Expression of the tumor-associated Ag mucin-1 (MUC1) after adenoviral transduction (rAd5Fib35-MUC1) was determined using two MAb.

RESULTS

We showed that the viability of cells and percentage of green fluorescent protein (GFP)-positive cells after transduction with a fiber-modified adenoviral vector (rAd5F35-GFP) was much higher than after nucleofection. Furthermore, phenotype and function of DC were not impaired by infection with adenovirus particles. Cells matured normally; up-regulation of CD40, CD80, CD83, CD86 and HLA-DR was not affected by adenoviral transduction. The capacity to stimulate naive T-cell proliferation was preserved and no change in IL-10 production was observed. Production of IL-12 increased up to 500-fold upon adenoviral transduction, considered to contribute positively to an anti-tumor immune response. Non-transduced mature DC expressed low levels of endogenous MUC1. After transduction with the rAd5F35-MUC1 adenoviral vector, a 100-fold increase in MUC1 expression by DC was observed.

DISCUSSION

The use of the fiber-modified adenoviral vector presented here may therefore be favorable compared with non-viral gene delivery systems for DC that will be used in cancer immunotherapy.

Flow cytometry assay of myeloid dendritic cells (mDCs) in peripheral blood during acute hepatitis C: Possible pathogenetic mechanisms

AIM: To asses the expression of myeloid dendritic cells (CD11c+) subset during acute HCV hepatitis and its possible involvement in natural history of the infection.

METHODS: We enrolled 11 patients with acute hepatitis C (AHC) (Group A), 10 patients with acute hepatitis A (AHA) (as infective control-Group B) and 10 healthy donors (group C) in this study. All patients underwent selective flow cytometry gating strategies to assess the peripheral number of the myeloid dendritic cells (mDCs) to understand the possible role and differences during acute hepatitis.

RESULTS: Eight of 11 patients with acute HCV hepatitis did not show any increase of mDCs compared to healthy individuals, while a significant decrease of mDCs was found in absolute cell count (z = -2.37; P < 0.05) and percentage (z= -2.30; P < 0.05) as compared with AHA. On the contrary, The remaining three patients of the group A had a higher mDCs number and percentage as occur in group B. Interestingly, after six months, those patients did not show any increase of mDCs subset were chronically infected. while the three subjects with an increase of peripheral mDCs, as in HAV acute infection, resolved the illness.

CONCLUSION: The lack of increase of mDCs during acute hepatitis C might be an important factor involved in chronicization of the infection.

Correlations among measles virus-specific antibody, lymphoproliferation and Th1/Th2 cytokine responses following measles-mumps-rubella-II (MMR-II) vaccination

Immunity to measles is conferred by the interplay of humoral and cellular immune responses, the latter being critical in maintaining long-term recall response. Therefore, it is important to evaluate measles-specific humoral and cellular immunity in populations several years after vaccination and understand the correlations among these measures of immunity. We examined measles-specific antibodies, lymphoproliferation and the Th1/Th2 signature cytokines, interferon (IFN)-gamma and interleukin (IL)-4, in a population-based cohort of healthy children from Olmsted County, Minnesota after two doses of measles-mumps-rubella-II (MMR-II) vaccine. We detected positive measures of measles-specific cellular and humoral immunity in the majority of our study population. However, a small proportion of subjects demonstrated an immune response skewed towards the Th2 type, characterized by the presence of either IL-4 and/or measles-specific antibodies and a lack of IFN-gamma production. Further, we observed a significant positive correlation between lymphoproliferation and secretion of IFN-gamma (r = 0.20, P = 0.0002) and IL-4 (r = 0.15, P = 0.005). Measles antibody levels were correlated with lymphoproliferation (r = 0.12, P = 0.03), but lacked correlation to either cytokine type. In conclusion, we demonstrated the presence of both long-term cellular and humoral responses after MMR-II vaccination in a significant proportion of study subjects. Further, a positive correlation between lymphoproliferation and IL-4 and IFN-gamma suggests that immunity to measles may be maintained by both Th1 and Th2 cells. We speculate that the Th2 biased response observed in a subset of our subjects may be insufficient to provide long-term immunity against measles. Further examination of the determinants of Th1 versus Th2 skewing of the immune response and long-term follow-up is needed.

Immune activation at effector and gene expression levels after measles vaccination in healthy individuals: a pilot study

Cellular immunity to measles vaccination is not fully understood at the effector response and gene expression levels. We enrolled 15 healthy individuals (15-25 years old) previously vaccinated with two doses of measles-mumps-rubella-II vaccine to characterize their cellular immunity. We detected a spectrum of lymphoproliferative response (median stimulation indices of 3.4), low precursor frequencies of interferon-gamma (median 0.11%) and interleukin-4 (median 0.05%) by Elispot, and cosecretion of Th1 and Th2 cytokines after measles virus stimulation. Further, global gene expression was examined in five subjects from this cohort after vaccination with an additional dose of measles vaccine (Attenuax, Merck) to identify the genes involved in measles immunity. Linear mixed effect models were used to identify genes significantly up or downregulated in vivo between baseline and Days 7 and 14 after measles vaccination. Measles vaccination induced upregulation of a set of 80 genes, which play a role in measles immunity, signal transduction, apoptosis, cell proliferation, and metabolic pathways. Among the 34 genes that were downregulated, only interferon-alpha is known to have a direct role in measles immunity. This study suggests that measles vaccination leads to activation of multiple cellular mechanisms that can override the immunosuppressant effects of the measles virus and induce immunity.