Measles virus-induced modulation of host-cell gene expression

Proteome Modulation in Peripheral Blood Mononuclear Cells of Peste des Petits Ruminants Vaccinated Goats and Sheep

In the present study, healthy goats and sheep (n = 5) that were confirmed negative for peste des petits ruminants virus (PPRV) antibodies by monoclonal antibody-based competitive ELISA and by serum neutralization test and for PPRV antigen by s-ELISA were vaccinated with Sungri/96. A quantitative study was carried out to compare the proteome of peripheral blood mononuclear cells (PBMCs) of vaccinated goat and sheep [5 days post-vaccination (dpv) and 14 dpv] vs. unvaccinated (0 day) to divulge the alteration in protein expression following vaccination. A total of 232 and 915 proteins were differentially expressed at 5 and 14 dpv, respectively, in goats. Similarly, 167 and 207 proteins were differentially expressed at 5 and 14 dpv, respectively, in sheep. Network generated by Ingenuity Pathway Analysis was “infectious diseases, antimicrobial response, and inflammatory response,” which includes the highest number of focus molecules. The bio functions, cell-mediated immune response, and humoral immune response were highly enriched in goats at 5 dpv and at 14 dpv. At the molecular level, the immune response produced by the PPRV vaccine virus in goats is effectively coordinated and stronger than that in sheep, though the vaccine provides protection from virulent virus challenge in both. The altered expression of certain PBMC proteins especially ISG15 and IRF7 induces marked changes in cellular signaling pathways to coordinate host immune responses.

MicroRNA Expression Profile in Peripheral Blood Lymphocytes of Sheep Vaccinated with Nigeria 75/1 Peste Des Petits Ruminants Virus

Peste des petits ruminants (PPR) is one of the highly contagious transboundary viral diseases of small ruminants. Host microRNA (miRNA) expression patterns may change in response to virus infection, and it mainly works as a post-transcriptional moderator in gene expression and affects viral pathogenesis and replication. In this study, the change of miRNA expression profile in peripheral blood lymphocyte (PBMC) from sheep inoculated with PPR vaccine virus in vivo as well as primary sheep testicular (ST) cells inoculated with PPR vaccine virus in vitro were determined via deep sequencing technology. In PBMC cells, 373 and 115 differentially expressed miRNAs (DEmiRNAs) were identified 3 days and 5 days post inoculated (dpi), respectively. While, 575 DEmiRNAs were identified when comparing miRNA profiles on 5 dpi with 3 dpi. Some of the DEmiRNAs were found to change significantly via time-course during PPR vaccine virus inoculated. Similarly, in ST cells, 136 DEmiRNAs were identified at 3 dpi in comparison with mock-inoculation. A total of 12 DEmiRNAs were validated by real-time quantitative PCR (RT-qPCR). The oar-miR-150, oar-miR-370-3p and oar-miR-411b-3p were found common differentially expressed in both PPR vaccine virus-inoculated PBMC cells and ST cells. Targets prediction and functional analysis of the DEmiRNAs uncovered mainly gathering in antigen processing and presentation pathways, protein processing in endoplasmic reticulum pathways and cell adhesion molecules pathways. Our study supplies information about the DEmiRNAs in PPR vaccine virus-inoculated PBMC cells and ST cells, and provides clues for further understanding the function of miRNAs in PPR vaccine virus replication.

Contrasting Gene Expression Profiles of Monocytes and Lymphocytes From Peste-Des-Petits-Ruminants Virus Infected Goats

In this study, transcriptome analysis of PPRV infected PBMC subsets-T helper cells, T cytotoxic cells, monocytes, and B lymphocytes was done to delineate their role in host response. PPRV was found to infect lymphocytes and not monocytes. The established receptor for PPRV-SLAM was found downregulated in lymphocytes and non-differentially expressed in monocytes. A profound deviation in the global gene expression profile with a large number of unique upregulated genes (851) and downregulated genes (605) was observed in monocytes in comparison to lymphocytes. ISGs-ISG15, Mx1, Mx2, RSAD2, IFIT3, and IFIT5 that play a role in antiviral response and the genes for viral sensors-MDA5, LGP2, and RIG1, were found to be upregulated in lymphocytes and downregulated in monocytes. The transcription factors-IRF-7 and STAT-1 that regulate expression of most of the ISGs were found activated in lymphocytes and not in monocytes. Interferon signaling pathway and RIG1 like receptor signaling pathway were found activated in lymphocytes and not in monocytes. This contrast in gene expression profiles and signaling pathways indicated the predominant role of lymphocytes in generating the antiviral response against PPRV in goats, thus, giving us new insights into host response to PPRV.

Manipulation of Non-canonical NF-κB Signaling by Non-oncogenic Viruses

Nuclear factor (NF)-κB is a major regulator of antiviral response. Viral pathogens exploit NF-κB activation pathways to avoid cellular mechanisms that eliminate the infection. Canonical (classical) NF-κB signaling, which regulates innate immune response, cell survival and inflammation, is often manipulated by viral pathogens that can counteract antiviral response. Oncogenic viruses can modulate not only canonical, but also non-canonical (alternative) NF-κB activation pathways. The non-canonical NF-κB signaling is responsible for adaptive immunity and plays a role in lymphoid organogenesis, B cell development, as well as bone metabolism. Thus, non-canonical NF-κB activation has been linked to lymphoid malignancies. However, some data strongly suggest that the non-canonical NF-κB activation pathway may also function in innate immunity and is modulated by certain non-oncogenic viruses. Collectively, these findings show the importance of studying the impact of different groups of viral pathogens on alternative NF-κB activation. This mini-review focuses on the influence of non-oncogenic viruses on the components of non-canonical NF-κB signaling.

MicroRNA expression profiling of goat peripheral blood mononuclear cells in response to peste des petits ruminants virus infection

Peste des petits ruminants virus (PPRV) belongs to the genus Morbillivirus that causes an acute and highly contagious disease in goats and sheep. Virus infection can trigger the change in the cellular microRNA (miRNA) expression profile, which play important post-transcriptional regulatory roles in gene expression and can greatly influence viral replication and pathogenesis. Here, we employed deep sequencing technology to determine cellular miRNA expression profile in goat peripheral blood mononuclear cells (PBMC) infected with Nigeria 75/1 vaccine virus, a widely used vaccine strain for mass vaccination programs against Peste des petits ruminants. Expression analysis demonstrated that PPRV infection can elicit 316 significantly differentially expressed (DE) miRNA including 103 known and 213 novel miRNA candidates in infected PBMC at 24 hours post-infection (hpi) as compared with a mock control. Target prediction and functional analysis of these DEmiRNA revealed significant enrichment for several signaling pathways including TLR signaling pathways, PI3K-Akt, endocytosis, viral carcinogenesis, and JAK-STAT signaling pathways. This study provides a valuable basis for further investigation of the roles of miRNA in PPRV replication and pathogenesis.

Transcriptome analysis reveals common differential and global gene expression profiles in bluetongue virus serotype 16 (BTV-16) infected peripheral blood mononuclear cells (PBMCs) in sheep and goats

Bluetongue is an economically important infectious, arthropod borne viral disease of domestic and wild ruminants, caused by Bluetongue virus (BTV). Sheep are considered the most susceptible hosts, while cattle, buffalo and goats serve as reservoirs. The viral pathogenesis of BTV resulting in presence or absence of clinical disease among different hosts is not clearly understood. In the present study, transcriptome of sheep and goats peripheral blood mononuclear cells infected with BTV-16 was explored. The differentially expressed genes (DEGs) identified were found to be significantly enriched for immune system processes - NFκB signaling, MAPK signaling, Ras signaling, NOD signaling, RIG signaling, TNF signaling, TLR signaling, JAK-STAT signaling and VEGF signaling pathways. Greater numbers of DEGs were found to be involved in immune system processes in goats than in sheep. Interestingly, the DEHC (differentially expressed highly connected) gene network was found to be dense in goats than in sheep. Majority of the DEHC genes in the network were upregulated in goats but down-regulated in sheep. The network of differentially expressed immune genes with the other genes further confirmed these findings. Interferon stimulated genes - IFIT1 (ISG56), IFIT2 (ISG54) and IFIT3 (ISG60) responsible for antiviral state in the host were found to be upregulated in both the species. STAT2 was the TF commonly identified to co-regulate the DEGs, with its network showing genes that are downregulated in sheep but upregulated in goats. The genes dysregulated and the networks perturbed in the present study indicate host variability with a positive shift in immune response to BTV in goats than in sheep.

Genomic analysis of host - Peste des petits ruminants vaccine viral transcriptome uncovers transcription factors modulating immune regulatory pathways

Peste des petits ruminants (PPR), is an acute transboundary viral disease of economic importance, affecting goats and sheep. Mass vaccination programs around the world resulted in the decline of PPR outbreaks. Sungri 96 is a live attenuated vaccine, widely used in Northern India against PPR. This vaccine virus, isolated from goat works efficiently both in sheep and goat. Global gene expression changes under PPR vaccine virus infection are not yet well defined. Therefore, in this study we investigated the host-vaccine virus interactions by infecting the peripheral blood mononuclear cells isolated from goat with PPRV (Sungri 96 vaccine virus), to quantify the global changes in the transcriptomic signature by RNA-sequencing. Viral genome of Sungri 96 vaccine virus was assembled from the PPRV infected transcriptome confirming the infection and demonstrating the feasibility of building a complete non-host genome from the blood transcriptome. Comparison of infected transcriptome with control transcriptome revealed 985 differentially expressed genes. Functional analysis showed enrichment of immune regulatory pathways under PPRV infection. Key genes involved in immune system regulation, spliceosomal and apoptotic pathways were identified to be dysregulated. Network analysis revealed that the protein - protein interaction network among differentially expressed genes is significantly disrupted in infected state. Several genes encoding TFs that govern immune regulatory pathways were identified to co-regulate the differentially expressed genes. These data provide insights into the host - PPRV vaccine virus interactome for the first time. Our findings suggested dysregulation of immune regulatory pathways and genes encoding Transcription Factors (TFs) that govern these pathways in response to viral infection.

Enhanced antitumor effects of an engineered measles virus Edmonston strain expressing the wild-type N, P, L genes on human renal cell carcinoma

Measles virus Edmonston strain (MV-Edm) is thought to have remarkable oncolytic activity that selectively destroys human tumor cells. The P/V/C protein of wild-type MV was shown to resist the antiviral effects of interferon (IFN)-alpha. Here, we engineered new MVs by arming MV-Edm tag strain (a V-defective vaccine-lineage strain, MV-Etag) with the P or N, P, and L genes of wild-type MV (MV-P and MV-NPL, respectively). The oncolytic activities of the MVs were determined in human renal cell carcinoma (RCC) cell lines and primary human RCC cells by the MTT assay. The antitumor efficacy of the MVs was evaluated in A-498 xenografts in nude mice. IFN-alpha effectively inhibited the replication of MV-Etag and MV-P, but not MV-NPL. MV-NPL more efficiently induced cytopathic effects (CPEs) in OS-RC-2 cells, even in the presence of human IFN-alpha. MV-NPL replicated more rapidly than MV-P and MV-Etag in A-498 cells. Apoptosis was induced earlier in A-498 cells by MV-NPL than MV-Etag and MV-P. MV-NPL showed more significant antitumoral effects and had prolonged replication compared to MV-Etag and MV-P. In this study, we demonstrated that the newly engineered MV-NPL has more effective oncolytic activity and may help establish an innovative cancer therapy.

Impaired cholesterol biosynthesis in a neuronal cell line persistently infected with measles virus

Measles virus remains a substantial cause of morbidity and mortality, producing acute infection with a potential for development of viral persistence. To study the events underlying acute and persistent measles virus infection, we performed a global transcriptional analysis on murine neuroblastoma cells that were acutely or persistently infected with measles virus. In general, we found that acute infection induced significantly more gene expression changes than did persistent infection. A functional enrichment analysis to identify which host pathways were perturbed during each of these infections identified several pathways related to cholesterol biosynthesis, including cholesterol metabolic processes, hydroxymethylglutaryl-coenzyme A (CoA) reductase activity, and acetyl-CoA C-acetyltransferase activity. We also found that measles virus colocalized to lipid rafts in both acute and persistent infection models and that the majority of genes associated with cholesterol synthesis were downregulated in persistent infection relative to acute infection, suggesting a possible link with the defective viral budding in persistent infection. Further, we found that pharmacological inhibition of cholesterol synthesis resulted in the inhibition of viral budding during acute infection. In summary, persistent measles viral infection was associated with decreased cholesterol synthesis, a lower abundance of cholesterol and lipid rafts in the cell membrane, and inhibition of giant-cell formation and release of viral progeny.

Detection of gene expression in an individual cell type within a cell mixture using microarray analysis

BACKGROUND

A central issue in the design of microarray-based analysis of global gene expression is the choice between using cells of single type and a mixture of cells. This study quantified the proportion of lipopolysaccharide (LPS) induced differentially expressed monocyte genes that could be measured in peripheral blood mononuclear cells (PBMC), and determined the extent to which gene expression in the non-monocyte cell fraction diluted or obscured fold changes that could be detected in the cell mixture.

METHODOLOGY/PRINCIPAL FINDINGS

Human PBMC were stimulated with LPS, and monocytes were then isolated by positive (Mono+) or negative (Mono-) selection. The non-monocyte cell fraction (MonoD) remaining after positive selection of monocytes was used to determine the effect of non-monocyte cells on overall expression. RNA from LPS-stimulated PBMC, Mono+, Mono- and MonoD samples was co-hybridised with unstimulated RNA for each cell type on oligonucleotide microarrays. There was a positive correlation in gene expression between PBMC and both Mono+ (0.77) and Mono- (0.61-0.67) samples. Analysis of individual genes that were differentially expressed in Mono+ and Mono- samples showed that the ability to detect expression of some genes was similar when analysing PBMC, but for others, differential expression was either not detected or changed in the opposite direction. As a result of the dilutional or obscuring effect of gene expression in non-monocyte cells, overall about half of the statistically significant LPS-induced changes in gene expression in monocytes were not detected in PBMC. However, 97% of genes with a four fold or greater change in expression in monocytes after LPS stimulation, and almost all (96-100%) of the top 100 most differentially expressed monocyte genes were detected in PBMC.

CONCLUSIONS/SIGNIFICANCE

The effect of non-responding cells in a mixture dilutes or obscures the detection of subtle changes in gene expression in an individual cell type. However, for studies in which only the most highly differentially expressed genes are of interest, separating and analysing individual cell types may be unnecessary.

Innate immune modulation by RNA viruses: emerging insights from functional genomics

By providing a global and integrated view of the host response to infection, functional genomic and systems-biology approaches are contributing to our understanding of RNA virus–host interactions. One area in which these approaches are being put to particularly good use is in shedding new light on the components of innate antiviral defence mechanisms and the viral strategies used to regulate or overcome them.

Genomic analyses have helped to reveal virus-specific differences in the way that viral recognition through pathogen-recognition receptors (PRRs) initiates intracellular signalling cascades. Whereas influenza virus appears to signal primarily through retinoic-acid-inducible gene I (RIG-I), West Nile virus signals through both RIG-I and melanoma differentiation-associated gene 5 (MDA5). Both viruses induce the expression of interferon (IFN)-regulatory factor 3 (IRF3) target genes and IFN-stimulated genes (ISGs).

Genomic analyses have provided a comprehensive view of the transcriptional programmes that are induced by Toll-like receptor (TLR) activation. One transcriptional profile is universally activated by all TLRs and a second profile is specific to TLR3 and TLR4. Nuclear factor-κB (NF-κB) is the key regulator of the universal response, which occurs early after TLR stimulation, and the IFN-stimulated response element (ISRE) is the key component of the TLR3/TLR4 response, which is induced after the NF-κB response.

Some highly virulent viruses, such as Ebola virus and rabies virus, are successful at inhibiting ISG expression, resulting in the marked suppression of genes in key innate antiviral pathways, including those mediated by IRF3. There seems to be a correlation between the antagonism of the IFN response and virulence.

Genomic analyses of the host response to the reconstructed 1918 pandemic influenza virus have revealed similarities and differences to contemporary influenza virus infection. Contemporary and 1918 influenza viruses each trigger an innate immune response that includes the expression of NF-κB and IRF3 target genes, and both viruses trigger a robust cytokine response that attracts immune-cell infiltration to infected tissues. Unlike contemporary virus strains, in which the early response to infection is resolved, the innate immune response triggered by the 1918 influenza virus is characterized by a strong and sustained induction that is associated with massive tissue damage and death.

Global gene-expression profiling has revealed that many effective, attenuated live-virus vaccines transiently induce a stronger type I IFN response than the cognate pathogen, and therefore implicates modulation of this response as an important strategy in rational vaccine design.

By providing a global view of the host response to infection, functional genomic approaches are proving useful in deciphering complex virus–host interactions. Here, the authors reveal how such approaches are being used to better understand viral triggering and regulation of host innate immune responses.

Although often encoding fewer than a dozen genes, RNA viruses can overcome host antiviral responses and wreak havoc on the cells they infect. Some manage to evade host antiviral defences, whereas others elicit an aberrant or disproportional immune response. Both scenarios can result in the disruption of intracellular signalling pathways and significant pathology in the host. Systems-biology approaches are increasingly being used to study the processes of viral triggering and regulation of host immune responses. By providing a global and integrated view of cellular events, these approaches are beginning to unravel some of the complexities of virus–host interactions and provide new insights into how RNA viruses cause disease.

Measles virus induces cell-type specific changes in gene expression

Measles virus (MV) causes various responses including the induction of immune responses, transient immunosuppression and establishment of long-lasting immunity. To obtain a comprehensive view of the effects of MV infection on target cells, DNA microarray analyses of two different cell-types were performed. An epithelial (293SLAM; a 293 cell line stably expressing SLAM) and lymphoid (COBL-a) cell line were inoculated with purified wild-type MV. Microarray analyses revealed significant differences in the regulation of cellular gene expression between these two different cells. In 293SLAM cells, upregulation of genes involved in the antiviral response was rapidly induced; in the later stages of infection, this was followed by regulation of many genes across a broad range of functional categories. On the other hand, in COBL-a cells, only a limited set of gene expression profiles was modulated after MV infection. Since it was reported that V protein of MV inhibited the IFN signaling pathway, we performed a microarray analysis using V knockout MV to evaluate V protein's effect on cellular gene expression. The V knockout MV displayed a similar profile to that of parental MV. In particular, in COBL-a cells infected with the virus, no alteration of cellular gene expression, including IFN signaling, was observed. Furthermore, IFN signaling analyzed in vitro was completely suppressed by MV infection in the COBL-a cells. These results reveal that MV induces different cellular responses in a cell-type specific manner. Microarray analyses will provide us useful information about potential mechanisms of MV pathogenesis.

Canine distemper virus infection of primary hippocampal cells induces increase in extracellular glutamate and neurodegeneration

The canine distemper virus (CDV) belongs to the Morbillivirus genus which includes important human pathogens like the closely related measles virus. CDV infection can reach the nervous system where it causes serious malfunctions. Although this pathology is well described, the molecular events in brain infection are still poorly understood. Here we studied infection in vitro by CDV using a model of dissociated cell cultures from newborn rat hippocampus. We used a recombinant CDV closely related to the neurovirulent A75/17 which also expresses the enhanced green fluorescent protein. We found that infected neurons and astrocytes could be clearly detected, and that infection spreads only slowly to neighboring cells. Interestingly, this infection causes a massive cell death of neurons, which includes also non-infected neurons. Antagonists of NMDA-type or alpha-amino-3-hydroxy-5-methylisoxazole-4-propinate (AMPA)-type glutamate receptors could slow down this neuron loss, indicating an involvement of the glutamatergic system in the induction of cell death in infected and non-infected cells. Finally, we show that, following CDV infection, there is a steady increase in extracellular glutamate in infected cultures. These results indicate that CDV infection induces excitotoxic insults on neurons via glutamatergic signaling.

Analysis of gene expression in Lassa virus-infected HuH-7 cells

The pathogenesis of Lassa fever is poorly understood. As the liver is a major target organ of Lassa virus, gene expression in Lassa virus-infected HuH-7 cells, a differentiated human hepatoma cell line, was studied. Cellular mRNA levels were measured at the late phase of acute infection, when virtually all cells expressed large amounts of nucleoprotein, and virus RNA concentration had reached>10(8) copies (ml supernatant)-1. Two types of transcription array were used: cDNA-based macroarrays with a set of 3500 genes (Atlas Human 1.2 arrays; Clontech) and oligonucleotide-based microarrays covering 18,400 transcripts (Human Genome U133A array; Affymetrix). Data analysis was based on statistical frameworks controlling the false-discovery rate. Atlas array data were considered relevant if they could be verified by U133A array or real-time RT-PCR. According to these criteria, there was no evidence for true changes in gene expression. Considering the precision of the U133A array and the number of replicates tested, potential expression changes due to Lassa virus infection are probably smaller than twofold. To substantiate the array data, beta interferon (IFN-beta) gene expression was studied longitudinally in Lassa virus-infected HuH-7 and FRhK-4 cells by using real-time RT-PCR. IFN-beta mRNA levels increased only twofold upon Lassa virus infection, although there was no evidence that the virus inhibited poly(I:C)-induced IFN-beta gene expression. In conclusion, Lassa virus interferes only minimally with gene expression in HuH-7 cells and poorly induces IFN-beta gene transcription.

Distinct gene expression profiles in peripheral blood mononuclear cells from patients infected with vaccinia virus, yellow fever 17D virus, or upper respiratory infections

Gene expression in human peripheral blood mononuclear cells was systematically evaluated following smallpox and yellow fever vaccination, and naturally occurring upper respiratory infection (URI). All three infections were characterized by the induction of many interferon stimulated genes, as well as enhanced expression of genes involved in proteolysis and antigen presentation. Vaccinia infection was also characterized by a distinct expression signature composed of up-regulation of monocyte response genes, with repression of genes expressed by B and T-cells. In contrast, the yellow fever host response was characterized by a suppression of ribosomal and translation factors, distinguishing this infection from vaccinia and URI. No significant URI-specific signature was observed, perhaps reflecting greater heterogeneity in the study population and etiological agents. Taken together, these data suggest that specific host gene expression signatures may be identified that distinguish one or a small number of virus agents.

Gene expression changes in peripheral blood mononuclear cells during measles virus infection

Measles virus continues to cause morbidity and mortality despite the existence of a safe and efficacious vaccine. Measles is associated with induction of both a long-lived protective immune response and immunosuppression. To gain insight into immunological changes during measles virus infection, we examined gene expression in blood mononuclear cells from children with acute measles and children in the convalescent phase compared to uninfected control children. There were 13 significantly upregulated and 206 downregulated genes. Upregulated genes included the immune regulatory molecules interleukin 1beta (IL-1beta), CIAS-1, tumor necrosis factor alpha, PDE4B, PTGS2, IL-8, CXCL2, CCL4, ICAM-1, CD83, GOS-2, IER3 (IEX-1), and TNFAIP3 (A20). Plasma levels of IL-1beta and IL-8 were elevated during measles virus infection. Downregulated genes mainly involved three gene ontology biological processes, transcription, signal transduction, and the immune response, and included IL-16 and cell surface receptors IL-4R, IL-6R, IL-7R, IL-27RA, CCR2, and CCR7. Most mRNAs had not returned to control values 1 month after discharge, consistent with prolonged immune response abnormalities during measles virus infection.

[Microarray-based transcriptome analyses in infectious diseases. A new diagnostic method]

The complex interaction between a pathogen and a host is the molecular basis of infectious diseases. Microarray technology is a powerful tool to investigate the crosstalk between pathogen and the host as it assesses whole genome expression profiles in response to disease. Deciphering the molecular details on both sides of the host-pathogen interaction will increase our understanding of the pathogenesis of infectious diseases and offer improvements in their diagnosis, treatment, prognosis, and prevention.

Gene expression patterns in dendritic cells infected with measles virus compared with other pathogens

Gene expression patterns supply insight into complex biological networks that provide the organization in which viruses and host cells interact. Measles virus (MV) is an important human pathogen that induces transient immunosuppression followed by life-long immunity in infected individuals. Dendritic cells (DCs) are potent antigen-presenting cells that initiate the immune response to pathogens and are postulated to play a role in MV-induced immunosuppression. To better understand the interaction of MV with DCs, we examined the gene expression changes that occur over the first 24 h after infection and compared these changes to those induced by other viral, bacterial, and fungal pathogens. There were 1,553 significantly regulated genes with nearly 60% of them down-regulated. MV-infected DCs up-regulated a core of genes associated with maturation of antigen-presenting function and migration to lymph nodes but also included genes for IFN-regulatory factors 1 and 7, 2'5' oligoadenylate synthetase, Mx, and TNF superfamily proteins 2, 7, 9, and 10 (TNF-related apoptosis-inducing ligand). MV induced genes for IFNs, ILs, chemokines, antiviral proteins, histones, and metallothioneins, many of which were also induced by influenza virus, whereas genes for protein synthesis and oxidative phosphorylation were down-regulated. Unique to MV were the induction of genes for a broad array of IFN-alphas and the failure to up-regulate dsRNA-dependent protein kinase. These results provide a modular view of common and unique DC responses after infection and suggest mechanisms by which MV may modulate the immune response.

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.

Interferon-induced exonuclease ISG20 exhibits an antiviral activity against human immunodeficiency virus type 1

Interferons (IFNs) encode a family of secreted proteins that provide the front-line defence against viral infections. It was recently shown that ISG20, a new 3'-->5' exoribonuclease member of the DEDD superfamily of exonucleases, represents a novel antiviral pathway in the mechanism of IFN action. In this report, it was shown that ISG20 expression is rapidly and strongly induced during human immunodeficiency virus type 1 (HIV-1) infection. In addition, it was demonstrated that the replication kinetics of an HIV-1-derived virus expressing the ISG20 protein (HIV-1(NL4-3ISG20)) was delayed in both CEM cells and peripheral blood mononuclear cells. No antiviral effect was observed in cells overexpressing a mutated ISG20 protein defective in exonuclease activity, suggesting that the antiviral effect was due to the exonuclease activity of ISG20. Paradoxically, despite the antiviral activity of ISG20 protein, virus rescue observed in HIV-1(NL4-3ISG20)-infected cells was not due to mutation or partial deletion of the ISG20 transgene, suggesting that the virus was able to counteract the cellular defences. In addition, HIV-1-induced apoptosis was significantly reduced in HIV-1(NL4-3ISG20)-infected cells suggesting that emergence of HIV-1(NL4-3ISG20) was associated with the inhibition of HIV-1-induced apoptosis. Altogether, these data reflect the ineffectiveness of virus replication in cells overexpressing ISG20 and demonstrate that ISG20 represents a new factor in the IFN-mediated antiviral barrier against HIV-1.

Antigen-specific gene expression profiles of peripheral blood mononuclear cells do not reflect those of T-lymphocyte subsets

Advances in microarray technology have allowed for the monitoring of thousands of genes simultaneously. This technology is of particular interest to immunologists studying infectious diseases, because it provides tremendous potential for investigating host-pathogen interactions at the level of immune gene expression. To date, many studies have focused either on cell lines, where the physiological relevance is questionable, or on mixed cell populations, where the contributions of individual subpopulations are unknown. In the present study, we perform an intrasubject comparison of antigen-stimulated immune gene expression profiles between a mixed population of peripheral blood mononuclear cells (PBMC) and the two predominant cell types found in PBMC, CD4+ and CD8+ T lymphocytes. We show that the microarray profiles of CD4+ and CD8+ T lymphocytes differ from each other as well as from that of the mixed cell population. The independence of the gene expression profiles of different cell types is demonstrated with a ubiquitous antigen (Candida albicans) as well as with a disease-specific antigen (human immunodeficiency virus p24). This study has important implications for microarray studies of host immunity and underscores the importance of profiling the expression of specific cell types.

Rotavirus-induced murine biliary atresia is mediated by nuclear factor-kappaB

BACKGROUND/PURPOSE

Intraperitoneal inoculation of rhesus rotavirus (RRV) was shown to cause atretic-appearing segments of the extrahepatic bile ducts (EHBDs) in a murine model. The factors responsible for the injury of bile ducts, however, remain unknown. In this study, the morphologic status of nuclear factor- kappa B (NF- kappa B) activation in the liver and in the EHBDs from murine model of biliary atresia induced by intraperitoneal injection of rotavirus was investigated.

METHODS

Within the first 24 hours of life, the newborn mice were infected through intraperitoneal route with a volume of 50 microL containing different titers of RRV. The pups were killed on days 5, 10, 15, 21, and 28 after inoculation and prepared under a dissecting microscope with photographic documentation. Consecutive sections of specimens were stained with H & E and used for histopathologic studies. The methods of modified Vision immunohistochemical staining was used to detect viral antigen of VP7 and active NF- kappa B. The distribution and intensity of staining were analyzed by image analysis software (GT-2 model, Huakang Co, Chengdu, China).

RESULTS

The viral antigen was detected by immunohistochemical staining in specimens from experimental groups on day 5 after infection. The occlusion of the EHBDs could be visualized after intraperitoneal injection of 10(7) plaque-forming unit (pfu) of RRV, whereas the incidence of cholestasis was reduced with an infection dosage of 10(6) pfu or less. Obliteration of the EHBDs did not occur when the injection dosage of RRV was reduced to 10(5) pfu or when inoculation of 10(7) pfu of RRV was combined with pyrolidine dithiocarbamate (PDTC), a chemical inhibitor of active NF- kappa B. The antigen of active NF- kappa B was detected by immunohistochemical staining in the liver and in the EHBDs from pups after inoculation of 10(7), 10(6), and 10(5) pfu RRV. Low or no expression of active NF- kappa B was noted in the specimens obtained from the control group. As the inflammatory reaction in the liver and in the EHBDs gradually subsided on day 28 after inoculation, the expression of active NF- kappa B also decreased. The expression of active NF- kappa B after injection of RRV combined with PDTC was similar to the expression in the control group on days 5 and 10 after infection.

CONCLUSIONS

The authors found that occlusion of the EHBDs could be noted in pups after inoculation of 10(7) pfu RRV. Meanwhile, the expression of active NF- kappa B in the liver and in the EHBDs was increased after inoculation of RRV. Simultaneous intraperitoneal injection of PDTC, however, was shown to prevent the obstruction of EHBDs secondary to inoculation of RRV. These results show that the murine biliary atresia induced by RRV is mediated by active NF- kappa B.

Differential expression of immunoregulatory genes in male and female Norway rats following infection with Seoul virus

Males of many species are more susceptible than females to infections caused by parasites, bacteria, fungi, and viruses. Following inoculation with Seoul virus, male rats have more virus present in target organs and shed virus longer than females. The goal of this study was to test the hypothesis that variation in the expression of genes associated with immune function mediates sex differences in hantavirus infection. Using DNA microarrays, we examined changes in gene expression in lung tissue during the early (when animals are viremic and shedding virus; Day 15 post-inoculation (p.i.)) and late (animals have low levels of infectious virus, but high antibody titers; Day 40 p.i.) phases of infection in adult male and female rats. After normalizing the gene expression levels from infected animals to the gene expression levels from same-sex uninfected controls, our data revealed that 1,813 genes were differentially expressed between the sexes during infection. The expression of key transcriptional factors (e.g., eIF-2 alpha, NF-kappa B, IRF-1, NF-IL-6, and STAT6) and genes that encode for proinflammatory (e.g., TNF alpha R, IL-1R, and IL-1RAcP), antiviral (e.g., IFN gamma R and Mx proteins), T cell (e.g., CD3 and TCR), and Ig superfamily (e.g., IgM, IgG, and MHC class I and II) proteins was higher in females than males. Conversely, males had higher expression of heat shock protein genes (e.g., hsp70) suggesting that cellular stress is elevated in males. These data provide candidate genes and cellular pathways that may underlie sex differences in responses to Seoul virus and possibly other hemorrhagic fever viruses.

Measles: immune suppression and immune responses

Measles is a highly contagious viral disease that remains the leading vaccine-preventable cause of child mortality worldwide. Deaths from measles are due largely to an increased susceptibility to secondary bacterial and viral infections, attributed to a prolonged state of immune suppression. Several abnormalities of the immune system have been described, including changes in lymphocyte number and function, shifts in cytokine responses, immunomodulatory effects of interleukin-10, down regulation of interleukin-12, impaired antigen presentation, and altered interferon alpha/beta signaling pathways. Although the current vaccine is very effective, knowledge of the molecular basis of the immune responses to measles virus could contribute to the development of a safer, more immunogenic measles vaccine. However, the safety of new measles vaccines must be carefully investigated, as two measles vaccines have resulted in unintended immunologic consequences: atypical measles following administration of the formalin-inactivated measles vaccine and increased mortality in girls following administration of high-titer measles vaccines.

Microarray analysis reveals characteristic changes of host cell gene expression in response to attenuated modified vaccinia virus Ankara infection of human HeLa cells

The potential use of the modified vaccinia virus Ankara (MVA) strain as a live recombinant vector to deliver antigens and elicit protective immune responses against infectious diseases demands a comprehensive understanding of the effect of MVA infection on human host gene expression. We used microarrays containing more than 15,000 human cDNAs to identify gene expression changes in human HeLa cell cultures at 2, 6, and 16 h postinfection. Clustering of the 410 differentially regulated genes identified 11 discrete gene clusters with altered expression patterns after MVA infection. Clusters 1 and 2 (accounting for 16.59% [68 of 410] of the genes) contained 68 transcripts showing a robust induction pattern that was maintained during the course of infection. Changes in cellular gene transcription detected by microarrays after MVA infection were confirmed for selected genes by Northern blot analysis and by real-time reverse transcription-PCR. Upregulated transcripts in clusters 1 and 2 included 20 genes implicated in immune responses, including interleukin 1A (IL-1A), IL-6, IL-7, IL-8, and IL-15 genes. MVA infection also stimulated the expression of NF-kappaB and components of the NF-kappaB signal transduction pathway, including p50 and TRAF-interacting protein. A marked increase in the expression of histone family members was also induced during MVA infection. Expression of the Wiskott-Aldrich syndrome family members WAS, WASF1, and the small GTP-binding protein RAC-1, which are involved in actin cytoskeleton reorganization, was enhanced after MVA infection. This study demonstrates that MVA infection triggered the induction of groups of genes, some of which may be involved in host resistance and immune modulation during virus infection.

Molecular signatures for diagnosis of infection: application of microarray technology

Technological developments such as microarray-based DNA, RNA and protein detection have opened new fields in genomics and proteomics. This review aims to highlight the potential value and limitation of this methodology to design and extract signature-based diagnostic markers for infectious disease.

Chips with everything: DNA microarrays in infectious diseases

Two developments are set to revolutionise research in and clinical management of infectious diseases. First, the completion of the human genome project together with the sequencing of many pathogen genomes, and second, the development of microarray technology. This review explains the principles underlying DNA microarrays and highlights the uses to which they are being put to investigate the molecular basis of infectious diseases. Pathogen studies enable identification of both known and novel organisms, understanding of genetic evolution, and investigation of determinants of pathogenicity. Host studies show the complexities of development and activation of both innate and adaptive immunity. Host-pathogen studies allow global analysis of gene expression during pathogenesis. Microarray technology will accelerate our understanding of the complex genetic processes underlying the interaction between microorganisms and the host, with consequent improvements in the diagnosis, treatment, and prevention of infectious diseases.

Endoplasmic reticulum stress is a determinant of retrovirus-induced spongiform neurodegeneration

FrCas(E) is a mouse retrovirus that causes a fatal noninflammatory spongiform neurodegenerative disease with pathological features strikingly similar to those induced by transmissible spongiform encephalopathy (TSE) agents. Neurovirulence is determined by the sequence of the viral envelope protein, though the specific role of this protein in disease pathogenesis is not known. In the present study, we compared host gene expression in the brain stems of mice infected with either FrCas(E) or the avirulent virus F43, differing from FrCas(E) in the sequence of the envelope gene. Four of the 12 disease-specific transcripts up-regulated during the preclinical period represent responses linked to the accumulation of unfolded proteins in the endoplasmic reticulum (ER). Among these genes was CHOP/GADD153, which is induced in response to conditions that perturb endoplasmic reticulum function. In vitro studies with NIH 3T3 cells revealed up-regulation of CHOP as well as BiP, calreticulin, and Grp58/ERp57 in cells infected with FrCas(E) but not with F43. Immunoblot analysis of infected NIH 3T3 cells demonstrated the accumulation of uncleaved envelope precursor protein in FrCas(E)- but not F43-infected cells, consistent with ER retention. These results suggest that retrovirus-induced spongiform neurodegeneration represents a protein-folding disease and thus may provide a useful tool for exploring the causal link between protein misfolding and the cytopathology that it causes.

Reovirus-induced alteration in expression of apoptosis and DNA repair genes with potential roles in viral pathogenesis

Reoviruses are a leading model for understanding cellular mechanisms of virus-induced apoptosis. Reoviruses induce apoptosis in multiple cell lines in vitro, and apoptosis plays a key role in virus-induced tissue injury of the heart and brain in vivo. The activation of transcription factors NF-kappaB and c-Jun are key events in reovirus-induced apoptosis, indicating that new gene expression is critical to this process. We used high-density oligonucleotide microarrays to analyze cellular transcriptional alterations in HEK293 cells after infection with reovirus strain T3A (i.e., apoptosis inducing) compared to infection with reovirus strain T1L (i.e., minimally apoptosis inducing) and uninfected cells. These strains also differ dramatically in their potential to induce apoptotic injury in hearts of infected mice in vivo-T3A is myocarditic, whereas T1L is not. Using high-throughput microarray analysis of over 12,000 genes, we identified differential expression of a defined subset of genes involved in apoptosis and DNA repair after reovirus infection. This provides the first comparative analysis of altered gene expression after infection with viruses of differing apoptotic phenotypes and provides insight into pathogenic mechanisms of virus-induced disease.

Biological threat detection via host gene expression profiling

With the increased threat posed by biological weapons, detection techniques for biothreat pathogens are critically needed to monitor and assess the severity of the illness once exposure has occurred. Current approaches for detecting biological threats are either time-consuming or highly specific but provide little information regarding pathogenicity. Genotyping of pathogens by PCR provides a fast and definitive means for identifying pathogens, but reliance on pathogen genotypic endpoints has several limitations. Current progress in DNA microarrays technology provides an alternative way to address the issues faced by traditional detection systems through host gene expression profiles of peripheral blood cells. We discuss the advantages and critical issues facing the use of host gene expression profiling for biological threat detection.

STAT protein interference and suppression of cytokine signal transduction by measles virus V protein

Measles virus, a paramyxovirus of the Morbillivirus genus, is responsible for an acute childhood illness that infects over 40 million people and leads to the deaths of more than 1 million people annually (C. J. Murray and A. D. Lopez, Lancet 349:1269-1276, 1997). Measles virus infection is characterized by virus-induced immune suppression that creates susceptibility to opportunistic infections. Here we demonstrate that measles virus can inhibit cytokine responses by direct interference with host STAT protein-dependent signaling systems. Expression of the measles V protein prevents alpha, beta, and gamma interferon-induced transcriptional responses. Furthermore, it can interfere with signaling by interleukin-6 and the non-receptor tyrosine kinase, v-Src. Affinity purification demonstrates that the measles V protein associates with cellular STAT1, STAT2, STAT3, and IRF9, as well as several unidentified partners. Mechanistic studies indicate that while the measles V protein does not interfere with STAT1 or STAT2 tyrosine phosphorylation, it causes a defect in IFN-induced STAT nuclear accumulation. The defective STAT nuclear redistribution is also observed in measles virus-infected cells, where some of the STAT protein is detected in cytoplasmic bodies that contain viral nucleocapsid protein and nucleic acids. Interference with STAT-inducible transcription may provide a novel intracellular mechanism for measles virus-induced cytokine inhibition that links innate immune evasion to adaptive immune suppression.

Cellular gene expression survey of vaccinia virus infection of human HeLa cells

Vaccinia virus (VV) is a cytocidal virus that causes major changes in host cell machinery shortly after infecting cells. To define the consequences of virus infection on host gene expression, we used microarrays of approximately 15,000 human cDNAs to examine expression levels of mRNAs isolated at 2, 6, and 16 h postinfection from cultures of infected HeLa cells. The majority of profiling changes during VV infection corresponded to downregulation of genes at 16 h postinfection. Differentially expressed genes were clustered into seven groups to identify common regulatory pathways, with most of them (90%) belonging to clusters 6 and 7, which represent genes whose expression was repressed after infection. Cluster 1, however, contained 37 transcripts (2.81%) showing a robust pattern of induction that was maintained during the course of infection. Genes in cluster 1 included those for Wiskott-Aldrich syndrome protein (WASP) family member WASF1, thymosine, adenosine A2a receptor, glutamate decarboxylase 2, CD-80 antigen, KIAA0888 protein, selenophosphate synthetase, pericentrin, and attractin as well as several expressed sequence tags. We analyzed in more detail the fate of WASP protein in VV-infected cells, because a related family member, N-WASP, is involved in viral motility. WASP protein accumulated in the course of infection; its increase required viral DNA replication and de novo protein synthesis, and it localized in cytoplasmic structures distinct from uninfected cells. This study is the first quantitative analysis of host gene expression following VV infection of cultured human cells, demonstrating global changes in the expression profile, and identifies upregulated genes with potential roles in the virus replication cycle.

Transcriptional analysis of the response of poultry species to respiratory pathogens

Respiratory tract diseases are the single most important cause of economic loss due to infections among poultry populations worldwide. However, the molecular mechanisms of the host response to infections remain unknown. Here, we review the literature and describe the adoption of a conceptually simple approach to understand the genetic and biochemical responses of host cells during infection with respiratory pathogens, such as avian pneumovirus (APV). The strategy that we have adopted integrates the powerful techniques of cDNA subtraction hybridization and microarray analysis for global transcriptional profiling. The results of our investigations identify the specific transcriptional alterations in host-cell gene expression that result from an attempt by the host to combat and limit the spread of the pathogen or by the pathogen to enhance its own survival and ability to reproduce. Our studies suggest that a molecular description of host-pathogen interactions in terms of differential gene expression will provide key insights on the molecular basis of disease pathogenesis, pathogen virulence, and host immunity. In addition, the results suggest that the identification of genes and pathways with a role in host response to infection has considerable practical implications for the future design and development of effective immunomodulators and vaccines.

Association of stress proteins with autoantigens: a possible mechanism for triggering autoimmunity?

Patterns of autoantibody production are diagnostic of many autoimmune disorders; the recent observation of additional autospecificities towards stress-induced proteins may also provide insight into the mechanisms by which such responses arise. Grp78 (also known as BiP) is a target of autoaggressive B and T cell responses in our murine model of anti-Ro (SS-A) autoimmunity and also in rheumatoid arthritis. In this report we demonstrate reciprocal intermolecular spreading occurs between Ro52 and Grp78 in immunized mice, reflecting physiological association of these molecules in vivo. Moreover, we provide direct biochemical evidence that Grp78 associates with the clinically relevant autoantigen, Ro52 (SS-A). Due to the discrete compartmentalization of Ro52 (nucleocytoplasmic) and Grp78 (endoplasmic reticulum; ER) we propose that association of these molecules occurs either in apoptotic cells, where they have been demonstrated indirectly to co-localize in discrete apoptotic bodies, or in B cells themselves where both Ro52 and Grp78 are known to bind to immunoglobulin heavy chains. Tagging of molecules by association with Grp78 may facilitate receptor mediated phagocytotsis of the complex; we show evidence that exogenous Grp78 can associate with cell surface receptors on a subpopulation of murine splenocytes. Given the likelihood that Grp78 will associate with viral glycoproteins in the ER it is possible that it may become a bystander target of the spreading antiviral immune response. Thus, we propose a model whereby immunity elicited towards Grp78 leads to the selection of responses towards the Ro polypeptides and the subsequent cascade of responses observed in human disease.

Contrasting effects of matrix protein on apoptosis in HeLa and BHK cells infected with vesicular stomatitis virus are due to inhibition of host gene expression

Vesicular stomatitis virus (VSV) is a potent inducer of apoptosis in host cells. Recently, it has been shown that two VSV products are involved in the induction of apoptosis, the matrix (M) protein, and another viral product that has yet to be identified (S. A. Kopecky et. al., J. Virol. 75:12169-12181, 2001). Comparison of recombinant viruses containing wild-type (wt) or mutant M proteins showed that wt M protein accelerates VSV-induced apoptosis in HeLa cells, while wt M protein delays apoptosis in VSV-infected BHK cells. Our hypothesis to explain these results is that both effects of M protein are due to the ability of M protein to inhibit host gene expression. This hypothesis was tested by infecting cells with an M protein mutant virus defective in the inhibition of host gene expression (rM51R-M virus) in the presence or absence of actinomycin D, another inhibitor of host gene expression. Actinomycin D accelerated induction of apoptosis of HeLa cells infected with rM51R-M virus and delayed apoptosis in BHK cells infected with rM51R-M virus, similar to the effects of wt M protein. The idea that the induction of apoptosis by M protein in HeLa cells is due to its ability to inhibit host gene expression was further tested by comparing the activation of upstream caspase pathways by M protein versus that by actinomycin D or 5,6-dichlorobenzimidazole riboside (DRB). Expression of M protein activated both caspase-8 and caspase-9-like enzymes, as did treatment with actinomycin D or DRB. Induction of apoptosis by M protein, actinomycin D, and DRB was inhibited in stably transfected HeLa cell lines that overexpress Bcl-2, an antiapoptotic protein that inhibits the caspase-9 pathway. A synthetic inhibitor of caspase-8, Z-IETD-FMK, did not inhibit induction of apoptosis by M protein, actinomycin D, or DRB. Taken together, our data support the hypothesis that the induction of apoptosis by M protein is caused by the inhibition of host gene expression and that the caspase-9 pathway is more important than the caspase-8 pathway for the induction of apoptosis by M protein and other inhibitors of host gene expression.

Autoreactivity against induced or upregulated abundant self-peptides in HLA-A*0201 following measles virus infection

Infectious agents have been implied as causative environmental factors in the development of autoimmunity. However, the exact nature of their involvement remains unknown. We describe a possible mechanism for the activation of autoreactive T cells induced by measles virus (MV) infection. The display of HLA-A*0201 associated peptides obtained from MV infected cells was compared with that from uninfected cells by mass spectrometry. We identified two abundant self peptides, IFI-6-16(74-82) and Hsp90beta(570-578), that were induced or upregulated, respectively, following infection. Their parental proteins, the type I interferon inducible protein IFI-6-16, and the beta chain of heat shock protein 90, have not been involved in MV pathogenesis. MV infection caused minor and major changes in the intracellular expression patterns of these proteins, possibly leading to altered peptide processing. CD8+ T cells capable of recognizing the self-peptides in the context of HLA-A*0201 were detectable at low basal levels in the neonatal and adult human T cell repertoire, but were functionally silent. In contrast, peptide-specific producing IFN-gamma producing effector cells were present in MV patients during acute infection. Thus, MV infection induces an enhanced display of self-peptides in MHC class I, which may lead to the temporary activation of autoreactive T cells.

The dual-function CD150 receptor subfamily: the viral attraction

The CD150 subfamily within the CD2 family is a growing group of dual-function receptors that have within their cytoplasmic tails a characteristic signaling motif. The ITSM (immunoreceptor tyrosine-based switch motif) enables these receptors to bind to and be regulated by small SH2 domain adaptor proteins, including SH2D1A (SH2-containing adaptor protein SH2 domain protein 1A) and EAT-2 (EWS-activated transcript 2). A major signaling pathway through the prototypic receptor in this subfamily, CD150, leads to the activation of interferon-gamma, a key cytokine for viral immunity. As a result, many viruses have designed strategies to usurp or alter CD150 functions. Measles virus uses CD150 as a receptor and Molluscum contagiosum virus encodes proteins that are homologous to CD150. Thus, viruses use CD150 subfamily receptors to create a favorable environment to elude detection and destruction. Understanding the CD150 subfamily may lead to new strategies for vaccine development and antiviral therapies.