Assessment of interferon gamma and indoleamine 2,3-dioxygenase 1 analysis during respiratory syncytial virus infection in infants in Italy: an observational case-control study.

OBJECTIVES: The aim of this study was to measure interferon gamma (IFN-γ) and indoleamine 2,3-dioxygenase 1 (IDO1) values in the White blood cells of infants during respiratory tract infections and to compare these with healthy age-matched controls. DESIGN: This was a prospective, observational case-control study conducted in 2019-2020. SETTING: The study took place at Regina Margherita Children's Hospital, Turin, Italy. PARTICIPANTS: The study comprised 63 infants, including 26 patients hospitalised for bronchiolitis due to a respiratory syncytial virus (RSV) infection and 37 age-matched controls. The inclusion criteria included a positive RSV test for an infant with bronchiolitis. METHODS: We collected peripheral blood and measured the relative quantification of messenger RNA (mRNA) expression of IFN-γ and IDO1 with TaqMan real-time PCR amplification. The data were collected on the first day of admission. RESULTS: The mean age of the 26 patients with RSV bronchiolitis (53.8% female) was 85 (9-346) days when they were admitted to the hospital. Their mean gestational age at birth was 38 weeks and their mean birth weight was 3100 (2780-3730) g. The expression of IFN-γ was significantly reduced in patients with bronchiolitis RSV compared with healthy controls (p=0.0132). However, there was no significant difference between the two groups when the IDO1 mRNA expression values in their WCC were measured (p=0.0642). CONCLUSION: Our findings did not clarify whether IDO1 expression was related to the early stage of the disease or to the young age of the infants. The data provide evidence that IFN-γ was significantly reduced in infants with bronchiolitis due to RSV, compared with age-matched healthy controls, but the IDO1 was not different. New investigations that focus on subjects infected with RSV at different stages of infancy would help to clarify whether IDO1 expression can be related to age.

Assessment of Interferon Gamma-Induced Protein 10 mRNA Release Assay for Detection of Latent Tuberculosis Infection in Egyptian Pediatric Household Contacts.

OBJECTIVES: Current diagnostic tests for tuberculosis (TB) in children living in low-endemic countries are limited by low specificity and the inability of the current tests to differentiate between active TB and latent TB infection (LTBI). This study aimed to evaluate the blood IP-10 mRNA expression level to detect LTBI in Egyptian pediatric household contacts (PHC). METHODS: TB-specific IP-10 and IFN-γ mRNA levels were assessed by real-time quantitative PCR (RT-qPCR) in 72 Egyptian PHC of active pulmonary TB cases. All study participants were also assessed by Tuberculin Skin Test (TST) and Quantiferon gold in tube (QFN-GIT) assay. RESULTS: IP-10 and IFN-γ mRNA expression levels were significantly higher in PHC with active TB or LTBI than TB negative (p < 0.0001). The level of IP-10 mRNA expression was significantly higher in PHC with active TB than LTBI (p = 0.0008). In contrast, there was no significant differences in the IFN-γ mRNA expression between PHC with active TB compared to LTBI (p = 0.49). The sensitivity and specificity of the IP-10 RT-qPCR were 94.2% and 95.2%, respectively, in PHC with active TB compared to 85.7% and 81.8% in PHC with LTBI. The negative and positive predictive values and accuracy of IP-10 RT-qPCR for distinguishing active TB from LTBI were 85.2%, 58.3%, and 72.6% respectively. CONCLUSION: Blood IP-10 mRNA expression level may be a potential diagnostic marker to help distinguish active TB from LTBI in PHC.

Assessment of Immune Responses in an Animal Model of Wheat Food Allergy via Epicutaneous Sensitization.

Wheat allergy is a pathological event involving immunocompetent cells against ingested wheat allergen and is clearly associated with transdermal sensitization. However, the molecular mechanisms involved in the disease etiology are not completely understood. A complex cellular and tissue network linking to food allergy makes it difficult to understand the molecular mechanism of allergenicity. Animal models are valuable tools to deduce basic principles of human disease without invasive intervention trials. A mouse model of wheat allergy has provided insights into effects of skin exposure to wheat protein; it is a plausible route of human sensitization for wheat anaphylaxis. Further investigation of this model will capture the essential occurrence and flow of events, bringing useful clues to develop effective treatment and control strategies against wheat allergy. Here, we describe a method for analyzing the expression of cell surface molecules in single cells isolated from lymphoid tissue with flow cytometry. Sensitization by wheat extracts significantly increases antigen-specific T cells in the spleen. Collecting information regarding the contribution of immune cells to allergic sensitization in the development of wheat allergy would be useful in preventing and treating food allergies.

Assessment of expression of interferon γ (IFN-G) gene and its antisense (IFNG-AS1) in breast cancer.

BACKGROUND: The role of long non-coding RNAs has been extensively appreciated in the contexts of cancer. Interferon γ-antisense RNA1 (IFNG-AS1) is an lncRNA located near to IFN-γ-encoding (IFNG) gene and regulates expression of IFNG in Th1 cells. METHODS: In the present study, we evaluated expression of IFNG and IFNG-AS1 in 108 breast samples including tumoral tissues and their adjacent non-cancerous tissues (ANCTs) using real-time PCR. IFNG-AS1 was significantly upregulated in tumoral tissues compared with ANCTs (expression ratio = 2.23, P = 0.03). RESULTS: Although the expression of IFNG was higher in tumoral tissues compared with ANCTs (relative expression = 1.89), it did not reach the level of significance (P = 0.07). IFNG expression was significantly higher in HER2-negative tumoral tissues compared with HER2-positive ones (P = 0.01) and in grade 1 samples compared with grade 2 ones (P = 0.03). No other significant difference was found in expressions of genes between other groups. CONCLUSION: Significant strong correlations were detected between expression of IFNG and IFNG-AS1 in both tumoral tissues and ANCTs. The present study provides evidences for participation of IFNG and IFNG-AS1 in the pathogenesis of breast cancer and warrants future studies to elaborate the underlying mechanism.

In vitro assessment of silver nanoparticles immunotoxicity.

This study aimed to characterize unwanted immune effects of nanoparticles (NP) using THP-1 cells, human whole blood and enriched peripheral blood monocytes. Commercially available silver NP (AgNP < 100 nm, also confirmed by Single Particle Extinction and Scattering) were used as prototypical NP. Cells were treated with AgNP alone or in combination with classical immune stimuli (i.e. LPS, PHA, PWM) and cytokine assessed; in addition, CD54 and CD86 expression was evaluated in THP-1 cells. AgNP alone induced dose-related IL-8 production in all models, with higher response observed in THP-1 cells, possibly connected to different protein corona formation in bovine versus human serum. AgNP potentiated LPS-induced IL-8 and TNF-α, but not LPS-induced IL-10. AgNP alone induced slight increase in IL-4, and no change in IFN-γ production. While responses to PHA in term of IL-4 and IFN-γ production were not affected, increased PWM-induced IL-4 and IFN-γ production were observed, suggesting potentiation of humoral response. Reduction in PHA-induced IL-10 was observed. Overall, results indicate immunostimulatory effects. THP-1 cells work as well as primary cells, representing a useful and practical alternative, with the awareness that from a physiological point of view the whole blood assay is the one that comes closest to reality.

Molecular, biochemical characterization and assessment of immunogenic potential of cofactor-independent phosphoglycerate mutase against Leishmania donovani: a step towards exploring novel vaccine candidate.

Despite immense efforts, vaccine against visceral leishmaniasis has yet not been developed. Earlier our proteomic study revealed a novel protein, cofactor-independent phoshoglycerate mutase (LdiPGAM), an important enzyme in glucose metabolism, in T helper cells type 1 (Th1) stimulatory region of soluble Leishmania donovani antigen. In this study, LdiPGAM was biochemically and molecularly characterized and evaluated for its immunogenicity and prophylactic efficacy against L. donovani. Immunogenicity of recombinant LdiPGAM (rLdiPGAM) was initially assessed in naïve hamsters immunized with it by analysing mRNA expression of inducible nitric oxide (NO) synthase (iNOS) and other Th1/T helper cells type 2 cytokines, which revealed an upregulation of Th1 cytokines along with iNOS. Immunogenicity of rLdiPGAM was further evaluated in lymphocytes of treated Leishmania-infected hamsters and peripheral blood mononuclear cells of Leishmania patients in clinical remission by various parameters, viz. lymphoproliferation assay and NO production (hamsters and patients) and levels of various cytokines (patients). rLdiPGAM induced remarkable Lymphoproliferative response and NO production in treated Leishmania-infected hamsters as well as in patients and increase in interferon gamma (IFN-γ), interleukin-12 (IL-12p40) responses in Leishmania patients in clinical remission. Vaccination with rLdiPGAM exerted considerable prophylactic efficacy (73%) supported by increase in mRNA expression of iNOS, IFN-γ and IL-12p40 with decrease in transforming growth factor beta and interleukin-10. Above results indicate the importance of rLdiPGAM protein as a potential vaccine candidate against visceral leishmaniasis.

HDAC4 mediates IFN-γ induced disruption of energy expenditure-related gene expression by repressing SIRT1 transcription in skeletal muscle cells.

Metabolic homeostasis is achieved through balanced energy storage and output. Impairment of energy expenditure is a hallmark event in patients with obesity and type 2 diabetes. Previously we have shown that the pro-inflammatory cytokine interferon gamma (IFN-γ) disrupts energy expenditure in skeletal muscle cells via hypermethylated in cancer 1 (HIC1)-class II transactivator (CIITA) dependent repression of SIRT1 transcription. Here we report that repression of SIRT1 transcription by IFN-γ paralleled loss of histone acetylation on the SIRT1 promoter region with simultaneous recruitment of histone deacetylase 4 (HDAC4). IFN-γ activated HDAC4 in vitro and in vivo by up-regulating its expression and stimulating its nuclear accumulation. HIC1 and CIITA recruited HDAC4 to the SIRT1 promoter and cooperated with HDAC4 to repress SIRT1 transcription. HDAC4 depletion by small interfering RNA or pharmaceutical inhibition normalized histone acetylation on the SIRT1 promoter and restored SIRT1 expression in the presence of IFN-γ. Over-expression of HDAC4 suppressed the transcription of genes involved in energy expenditure in a SIRT1-dependent manner. In contrast, HDAC4 knockdown/inhibition neutralized the effect of IFN-γ on cellular metabolism by normalizing SIRT1 expression. Therefore, our data reveal a role for HDAC4 in regulating cellular energy output and as such provide insights into rationalized design of novel anti-diabetic therapeutics.

Up-to date knowledge on the in vivo transcriptomic effect of the Mediterranean diet in humans.

The present review discusses and summarizes the up-to-date body of knowledge concerning human nutrigenomic studies with Mediterranean diet (MedDiet) and olive oil (OO) interventions, at real-life doses and conditions. A literature review was carried out until March 2012. Original articles assessing the nutrigenomic effect of the MedDiet and its main source of fat, OO, on gene expression were selected. State-of-the-art data in this field, although scarce, are promising. Despite a great diversity among studies, the attributed health benefits of the MedDiet and its components, such as OO, could be explained by a transcriptomic effect on atherosclerosis, inflammation, and oxidative stress-related genes (i.e. ADRB2, IL7R, IFNγ, MCP1, TNFα). Gene expression changes toward a protective mode were often associated with an improvement in systemic markers for oxidation and inflammation. The suggested underlying molecular pathways responsible for these changes, and the extent to which evidence exists of a MedDiet and OO nutrigenomic effect, are also discussed.

IL-22 mediates host defense against an intestinal intracellular parasite in the absence of IFN-γ at the cost of Th17-driven immunopathology.

The roles of Th1 and Th17 responses as mediators of host protection and pathology in the intestine are the subjects of intense research. In this study, we investigated a model of intestinal inflammation driven by the intracellular apicomplexan parasite Eimeria falciformis. Although IFN-γ was the predominant cytokine during E. falciformis infection in wild-type mice, it was found to be dispensable for host defense and the development of intestinal inflammation. E. falciformis-infected IFN-γR(-/-) and IFN-γ(-/-) mice developed dramatically exacerbated body weight loss and intestinal pathology, but they surprisingly harbored fewer parasites. This was associated with a striking increase in parasite-specific IL-17A and IL-22 production in the mesenteric lymph nodes and intestine. CD4(+) T cells were found to be the source of IL-17A and IL-22, which drove the recruitment of neutrophils and increased tissue expression of anti-microbial peptides (RegIIIß, RegIIIγ) and matrix metalloproteinase 9. Concurrent neutralization of IL-17A and IL-22 in E. falciformis-infected IFN-γR(-/-) mice resulted in a reduction in infection-induced body weight loss and inflammation and significantly increased parasite shedding. In contrast, neutralization of IL-22 alone was sufficient to increase parasite burden, but it had no effect on body weight loss. Treatment of an E. falciformis-infected intestinal epithelial cell line with IFN-γ, IL-17A, or IL-22 significantly reduced parasite development in vitro. Taken together, to our knowledge these data demonstrate for the first time an antiparasite effect of IL-22 during an intestinal infection, and they suggest that IL-17A and IL-22 have redundant roles in driving intestinal pathology in the absence of IFN-γ signaling.

Assessment of bioactivity of a recombinant chicken interferon-gamma expressed using a baculovirus expression system.

The full-length coding sequence of chicken interferon-γ (ChIFN-γ) was cloned into a baculovirus nonfusion vector, pFastBacDual, and expressed in Sf21 insect cells. Recombinant ChIFN-γ (rChIFN-γ) protein was found to be expressed both intracellularly as well as in the culture supernatants. The affinity-purified rChIFN-γ contained 14, 17, and 28 kDa proteins, possibly representing both glycosylated and nonglycosylated protein forms of ChIFN-γ. The bioactivity of rChIFN-γ was confirmed in vitro by production of nitric oxide in a chicken macrophage cell line (HD11) and antiviral activity against vesicular stomatitis virus in primary chicken embryonic fibroblast cells. Further, HD11 cells stimulated with rChIFN-γ showed significant upregulation of inducible nitric oxide synthases, IFN-γ, interleukin-1ß, interleukin-12p35, signal transducers and activators of transcription 1, class II, major histocompatibility complex, transactivator, and major histocompatibility complex II-ß chain (BL-B) transcripts. In conclusion, the present study provides information on the ability of functionally active rChIFN-γ expressed in a baculovirus system in inducing significant transcriptional upregulation of various immune system-related genes, including those that encode cytokines, antigen-presenting molecules, and transcription factors involved in the major histocompatibility complex and IFN-signaling pathway.

Amended recombinant cells (ARCs) expressing bovine IFN-gamma: an economical and highly effective adjuvant system.

Interferon-gamma (IFN-gamma) has potent immune stimulatory activity, but purifying recombinant protein is expensive, soluble cytokine delivery is inefficient, and high doses of IFN-gamma cause adverse systemic effects. We've shown, however, that chemically fixed, amended recombinant Pseudomonas fluorescens cells (ARCs), expressing soluble bovine IFN-gamma (BGI/ARCs), provide an effective production and delivery vehicle for highly active cytokine. In this report we investigate the immune enhancing activity of BGI/ARCs in the presence or absence of two other adjuvants which enhance cell recruitment and protein uptake. Adjuvant activity and immune-mediated protection was evaluated using recombinant, truncated glycoprotein-D (tgD) and a bovine herpesvirus-1 (BHV-1) disease challenge. Our initial dose-titration study showed that 100 microg of recombinant IFN-gamma in BGI/ARCs significantly increased both IgG1 and IgG2 tgD-specific antibody titres and IgG1/IgG2 ratios were significantly reduced with as little as 1.0 microg IFN-gamma. Vaccine formulation studies, using 20 microg tgD/vaccine dose and 100 microg IFN-gamma delivered in BGI/ARCs, formulated in phosphate buffered saline (PBS), induced significantly increased antibody responses, following both primary and secondary immunization, and immune-mediated protection following a BHV-1 respiratory infection. Co-formulating BGI/ARCs with either an oil and water emulsion (Emulsigen) or a polyphosphazene polymer (PCPP) did not significantly enhance tgD-specific antibody titres or disease protection when compared with BGI/ARCs alone. Surprisingly, co-delivering a single dose of BGI/ARCs with tgD protein in PBS had optimal adjuvant activity and the dose of IFN-gamma delivered was four-fold less than the dose previously shown to induce adverse systemic responses.

Computational investigations into the origins of short-term biochemical memory in T cell activation.

Recent studies have reported that T cells can integrate signals between interrupted encounters with Antigen Presenting Cells (APCs) in such a way that the process of signal integration exhibits a form of memory. Here, we carry out a computational study using a simple mathematical model of T cell activation to investigate the ramifications of interrupted T cell-APC contacts on signal integration. We consider several mechanisms of how signal integration at these time scales may be achieved and conclude that feedback control of immediate early gene products (IEGs) appears to be a highly plausible mechanism that allows for effective signal integration and cytokine production from multiple exposures to APCs. Analysis of these computer simulations provides an experimental roadmap involving several testable predictions.

Risk assessment in haematopoietic stem cell transplantation: pre-transplant patient and donor factors: non-HLA genetics.

Non-HLA genetics involving the study of single-nucleotide polymorphisms (SNPs) and microsatellites of cytokine and cytokine receptor genes, and as well as genes associated with response to infection and therapeutic drugs, are currently being studied for associations with diseases, including autoimmune disease, cancer and solid-organ transplant rejection. This chapter will summarize the potential role of non-HLA genetics in predicting outcome of haematopoietic stem-cell transplantation (HSCT) and how genotyping for non-HLA genes may give insight into the immunobiology of HSCT complications, including GvHD and infectious episodes. Future directions - including the role of pharmacogenomics, use of the research results for individualized medicine, and interpretation of data - will also be discussed.

Assessment of Sarcocystis neurona sporocyst viability and differentiation between viable and nonviable sporocysts using propidium iodide stain.

Sarcocystis neurona has become recognized as the major causative agent of equine protozoal myeloencephalitis (EPM) in the Americas. At least 3 pathogenic species of Sarcocystis, including S. neurona, can be isolated from opossums. Methods are needed to ascertain whether these isolates are viable and capable of causing infections. In this study, the nuclear stain propidium iodide (PI) was used to differentiate between live (viable) and heat-killed (nonviable) S. neurona sporocysts. PI was excluded by live sporocysts but penetrated compromised sporocyst membrane and stained sporozoite nuclei of dead sporocysts. After live and dead sporocysts were mixed at various ratios, the number of unstained sporocysts detected after the staining procedure correlated significantly (r2 = 0.9978) with the expected numbers of live sporocysts. Sporocyst mixtures were also assayed for in vitro excystation and development in tissue cultures. The correlation between the percentage of plaques formed in tissue cultures and the percentage of expected infectious (live) sporocysts in each mixture was r2 = 0.6712. By analysis of variance, no statistically significant difference was measured between the percentage of viable sporocysts and the percentage of infectious sporocysts (P = 0.3902) in each mixture. In addition, there was evidence of a relation between PI impermeability of sporocysts and animal infectivity. These results suggest that the PI dye-exclusion technique can be a useful tool in identifying viability and potential infectivity of S. neurona sporocysts and in differentiating between viable and nonviable sporocysts.

Quantification of cytokine gene expression using an economical real-time polymerase chain reaction method based on SYBR Green I.

Assessment of cytokine expression has become crucial to understand host responses to infections as well as autoimmunity. Several approaches including Northern blot, RNase protection assay and enzyme-linked immunosorbent assay have been used for this purpose, but they are time consuming, labour intense, and relatively large quantity of the samples is usually required. Recently, a technique termed real-time reverse transcriptase-polymerase chain reaction (RT-PCR) has been developed to determine genetic expression with great sensitivity and specificity; however, specialized instrumentation and costly reagents are usually needed. We aimed at using low-cost reagents for real-time PCR. This was achieved by adapting a conventional RT-PCR protocol to the quantitative real-time format, by the addition of the SYBR Green I reagent. We validated the approach by assessing the cytokine gene expression of murine splenocytes upon stimulation with phorbol 12-myristate 12-acetate (PMA)-ionomycin. The results using this technique were compared with those obtained with the well-established gene array method. We conclude that the use of the SYBR Green I reagent during real-time RT-PCR provides a highly specific and sensitive method to quantify cytokine expression with accuracy and no post-PCR manipulation.

Allele frequencies for an interferon-gamma microsatellite in a population of Brazilian leprosy patients.

A group of Brazilian leprosy patients and controls were genotyped for a CA-repeat microsatellite polymorphism within the interferon (IFN)-gamma gene. A significantly higher frequency of alleles 5-7 was observed in this patient population, indicating that IFN-gamma gene polymorphism may contribute to the course of leprosy post-infection.

Variation in immune response genes and chronic Q fever. Concepts: preliminary test with post-Q fever fatigue syndrome.

Acute primary Q fever is followed by various chronic sequelae. These include subacute Q fever endocarditis, granulomatous reactions in various organs or a prolonged debilitating post-infection fatigue syndrome (QFS). The causative organism, Coxiella burnetii, persists after an initial infection. The differing chronic outcomes may reflect variations within cytokine and accessory immune control genes which affect regulation of the level of persistence. As a preliminary test of the concept we have genotyped QFS patients and controls for gene variants spanning 15 genes and also examined HLA-B and DR frequencies. QFS patients exhibited a significantly increased frequency of HLA-DR-11 compared with controls and also significant differences in allelic variant frequencies within the NRAMP, and IFNgamma genes. These results indicate a possible genetic role in the expression of overt chronic Q fever. Further studies will be undertaken to increase sample sizes, to survey other forms of chronic Q fever and to examine Q fever patients who have recovered without sequelae.

Allele frequencies of polymorphisms of TNFA, IL-6, IL-10 and IFNG in an Italian Caucasian population.

Polymorphisms in the regulatory and intronic regions of several cytokines have been associated with differential cytokine production. In this paper we genotyped, using the polymerase chain reaction-sequence-specific primers (PCR-SSP) method, a series of 363 healthy Italian Caucasians with the aim of obtaining a reference population for further studies on the role of cytokines in the inflammatory and immune responses. We also compared the results to those for other populations. The polymorphisms analysed were those of tumour necrosis factor alpha (TNFA), interleukin 6 (IL-6), interleukin 10 (IL-10) and interferon gamma (IFNG). We found that the frequency of allele TNFA*1 at position -380 was 87.7% and that of TNFA*2 was 12.4%, significantly different from those of the UK and Japanese populations but not different from that of a population in Gambia. For IL-10 the frequencies of alleles -1082A and -1082G were 63.0% and 37.0% and those of alleles -819C, - 819T, -592C and -592A were 70.8, 29.2, 70.8 and 29.2%, respectively, significantly different from those observed in south-east England, in Manchester and in an Oriental population from southern China. The frequencies of IL-6 alleles - 174C and -174G were 29.0 and 71.0%, respectively; for IFNG polymorphisms at position -874, in the population under evaluation, the alleles -874T and -874A were present in 44.7 and 55.3% of the subjects, respectively. Genotype frequencies of IL-6 were significantly different from those observed in populations from Germany and from the UK. The analysis carried out by our group indicates that there is heterogeneity in the frequencies of the cytokine polymorphisms among the different Caucasian populations, and this underlines the importance of a 'local' reference population when evaluating the clinical relevance of cytokine gene polymorphisms.

Immune status assessment by abundance of IFN-alpha and IFN-gamma mRNA in chicken blood.

Avian diseases, including such viral infection as infectious bursal disease, infectious anemia, and Marek's disease, often cause immunosuppression, leading to more severe infection, problems with secondary infection, and inadequate responses to vaccination. Immunosuppression thus causes serious economic losses in commercial poultry production. To date, methods for assessing immune status have been too slow to be of practical help. Reasoning that immunosuppression should be reflected by reduced production of interferons (IFN) in response to a viral antigen, we have developed competitive nucleic acid hybridization microtiter plate assays for chicken IFN-alpha (ChIFN-alpha) and ChIFN-gamma mRNA. To evaluate the assay, chickens were challenged with inactivated Newcastle disease virus (iNDV). Whole blood samples were collected at various times subsequently and preserved with a cationic detergent. Later, total RNA was extracted, and mRNA for both ChIFN-alpha and ChIFN-gamma was measured. Both rose from undetectable levels to reach a peak by 4 h, remained high for about 3 days, and fell to undetectable levels by day 5. Results were similar in chickens aged between 1 and 28 days. In later experiments, blood was collected 4 h after viral challenge. When chickens were immunosuppressed by administering 4-5 mg cyclophosphamide (CY) daily for 3 days and challenged with iNDV, they transcribed less ChIFN-alpha and ChIFN-gamma mRNA, and their antibody response was impaired. Our results suggest that suspected immunosuppression in a commercial flock could be assessed within 2-3 days by challenging birds with iNDV and measuring the amounts of ChIFN-alpha and ChIFN-gamma mRNA in blood obtained 2-4 h later.

Comparative assessment of virulence of recombinant vaccinia viruses expressing IL-2 and IL-15 in immunodeficient mice.

IL-2 and -15 belong to the four alpha-helix bundle family of cytokines and display a spectrum of overlapping immune functions because of shared signal transducing receptor components of the IL-2 receptor complex. However, recent evidence suggests a nonredundant unique role for IL-15 in the establishment and perhaps maintenance of peripheral natural killer (NK) cell populations in vivo. To explore the contribution of locally released IL-15 on peripheral NK-cell-mediated innate immune responses, we generated a recombinant vaccinia virus that expresses IL-15 and evaluated the course of vaccinial disease in athymic nude mice. Coexpression of IL-15 resulted in the attenuation of virulence of vaccinia virus, and mice inoculated with 10(5) plaque-forming units or less resolved the infection successfully. In contrast, mice inoculated with a similar dose of the control vaccinia virus failed to eliminate the virus and died of generalized vaccinial disease. Enhanced expression of IL-12 and IFN-gamma as well as induction of chemokines were evident in the mice inoculated with IL-15-expressing vaccinia virus in addition to an increase in NK cells in the spleen. However, in this model system, the degree of attenuation in viral virulence attained with coexpression of IL-15 was much less than that achieved with coexpression of IL-2, suggesting that the peripheral NK-cell-mediated events are more responsive to IL-2 than to IL-15.