Biomedical subjects

Z Xing

Publications and source records attributed to Z Xing.

At least 19 recordsLinked to original sources

PubMed2006

The isozyme-specific effects of cyclooxygenase-deficiency on bone in mice.

Prostaglandin E(2) (PGE(2)) plays a critical role in skeletal physiology and bone loss. PGE(2) production is regulated in vivo by at least two cyclooxygenase (COX) isozymes, COX-1 and COX-2. The purpose of this study was to investigate the in vivo effects of the selective deletion of COX-1 or COX-2 on bone mineral density (BMD), bone microarchitecture and bone strength in wild type (WT), COX-1(-/-) and COX-2(-/-) mice. Using a LUNAR PIXImus, BMD was measured in 18 (WT), 18 COX-1(-/-) and 16 COX-2(-/-) mice. COX-1(-/-) mice exhibited significantly higher BMD (0.0506 g/cm(2) +/- 0.0014 g/cm(2)) than either WT (0.0493 g/cm(2) +/- 0.0019, P < or = 0.05) or COX-2(-/-) (0.0473 g/cm(2) +/- 0.0034, P < or = 0.01) mice. COX-2(-/-) mice had significantly lower BMD than WT (P < or = 0.01) or COX-1(-/-) (P < or = 0.01). Flexure stress of the femurs, determined by breaking the bones with three-point bending, correlated with bone density. Although plasma levels of both Ca(2+) and PTH were comparable in wild type and COX-1(-/-) mice, both were elevated in COX-2(-/-) mice consistent with primary hyperparathyroidism. These studies suggest that COX enzymes are important regulators of BMD and bone strength in mice. The beneficial effect of absence of the COX-1 enzyme on skeletal parameters may be secondary to decreases in PGE(2). On the other hand, primary hyperparathyroidism and lower bone magnesium content may account for the lower BMD and impairments in bone strength of COX-2(-/-) mice. Further elucidation of the effects of the COX pathway on bone remodeling may provide important information on potential therapeutic targets for preventing and/or treating osteoporosis.

Animals↗

PubMed2006

Manipulation of dendritic cells for host defence against intracellular infections.

Dendritic cells (DCs) are an important innate immune cell type which is the bridge between innate and adaptive immunity. Mounting experimental evidence suggests that manipulating DCs represents a powerful means to enhance host defence against intracellular infectious diseases. We have developed several strategies to manipulate DCs either in vivo or in vitro for the purpose of enhancing the effect of vaccination or immunotherapeutics. In vivo delivery of transgene encoding GM-CSF (granulocyte/macrophage colony-stimulating factor), a DC-activating cytokine, increases the number and activation status of DCs at various tissue sites and enhances antimicrobial immune responses in murine models. Co-expression or co-delivery of GM-CSF gene transfer vector with an antimicrobial vaccine enhances microbial antigen-specific T-cell responses and immune protection. Murine bone marrow-derived DCs are being manipulated in vitro and exploited as a vaccine delivery system. Transduction of DCs with a virus-vectored tuberculosis vaccine is a powerful way to activate T-cells in vivo. Such genetically modified DC vaccines can be administered either parenterally or mucosally via the respiratory tract.

Adjuvants, Immunologic↗

PubMed2003

Pulmonary fluorodeoxyglucose uptake in infants of very low birth weight with and without intrauterine inflammation.

OBJECTIVE: We compared early pulmonary (18)fluorodeoxyglucose ((18)FDG) uptake in infants who had very low birth weight with and without exposure to intrauterine inflammation by using positron emission tomography (PET). A secondary goal was to correlate (18)FDG uptake with later death or bronchopulmonary dysplasia. METHODS: Within 72 hours of birth, 22 singleton infants between 25 and 30 weeks of gestation had a thoracic PET scan after intravenous (18)FDG. Influx constants (K(i)) for (18)FDG were determined. Placental histology assessed exposure to intrauterine inflammation. RESULTS: Chorioamnionitis was found in 13 infants. Seven of these infants also had evidence of funisitis. No inflammation was detected in the remaining nine infants. Median (minimum, maximum) thoracic K(I) was 0.008 (0.006, 0.011) mL/min/mL in infants with funisitis, 0.006 (0.002, 0.008) in infants with chorioamnionitis only, and 0.006 (0.001, 0.015) in infants with no evidence of intrauterine inflammation (P=.16). No relation was found between K(i) and later death or bronchopulmonary dysplasia. Cord blood interleukin-6 was elevated in newborns with placental inflammation (P=.014). CONCLUSION: Early thoracic PET scanning for metabolically active inflammatory cells does not differ between infants with and without exposure to intrauterine inflammation. Evidence of early intrapulmonary sequestration of inflammatory cells in some infants without chorioamnionitis points to the complex etiology of postnatal inflammation.

Bronchopulmonary Dysplasia↗

PubMed2001

Enhanced protection against fatal mycobacterial infection in SCID beige mice by reshaping innate immunity with IFN-gamma transgene.

Humans with immune-compromised conditions such as SCID are unable to control infection caused by normally nonpathogenic intracellular pathogens such as Mycobacterium bovis bacillus Calmette-Guérin. We found that SCID beige mice lacking both lymphocytes and NK cells had functionally normal lung macrophages and yet a selectively impaired response of type 1 cytokines IFN-gamma and IL-12, but not TNF-alpha, during M. bovis bacillus Calmette-Guérin infection. These mice succumbed to such infection. A repeated lung gene transfer strategy was designed to reconstitute IFN-gamma in the lung, which allowed investigation of whether adequate activation of innate macrophages could enhance host defense in the complete absence of lymphocytes. IFN-gamma transgene-based treatment was initiated 10 days after the establishment of mycobacterial infection and led to increased levels of both IFN-gamma and IL-12, but not TNF-alpha, in the lung. Lung macrophages were activated to express increased MHC molecules, type 1 cytokines and NO, and increased phagocytic and mycobactericidal activities. Activation of innate immunity markedly inhibited otherwise uncontrollable growth of mycobacteria and prolonged the survival of infected SCID hosts. Thus, our study proposes a cytokine transgene-based therapeutic modality to enhance host defense in immune-compromised hosts against intracellular bacterial infection, and suggests a central effector activity played by IFN-gamma-activated macrophages in antimycobacterial cell-mediated immunity.

Adenoviridae↗

PubMed2001

Transient transgene expression of decorin in the lung reduces the fibrotic response to bleomycin.

Pulmonary fibrosis is a chronic progressive disease with no effective therapy. Transforming growth factor beta (TGF-beta) is thought to be a key profibrotic mediator and blocking its activity is therefore one of the targets of new treatment strategies for fibrosis. Decorin is an endogenous proteoglycan and one of the known inhibitors of TGF-beta. The short half-life of peptide-based therapeutics makes gene transfer a promising approach to achieve prolonged protein levels in the lung. Replication-deficient adenovirus was used to deliver decorin transgene (AdDec) to the airways by a single intranasal injection in a murine bleomycin model of lung fibrosis. The ability of vector-derived decorin to inhibit TGF-beta was examined in a bioassay and its effect on bleomycin-induced pulmonary fibrosis was determined by histomorphology and lung hydroxyproline. In vitro, supernatant from cells infected with AdDec abrogated the bioactivity of TGF-beta in a dose-dependent manner whereas control virus (AdDL70) had no effect. In vivo, treatment of bleomycin-injected mice with AdDec substantially reduced the fibrogenic response compared with control virus (hydroxyproline: bleomycin/AdDec, 1.96 microg/mg; bleomycin/AdDL70, 3.05 microg/mg; p = 0.0005). These results suggest that a single administration of AdDec was able to generate a local pulmonary environment that effectively blocked the fibrogenic response to bleomycin by inhibition of TGF-beta.

Adenoviridae↗

PubMed2001

The hunt for new tuberculosis vaccines: anti-TB immunity and rational design of vaccines.

Tuberculosis (TB) remains to be a leading infectious cause of death worldwide. Apparently, the current BCG vaccine that has been used for 80 years, has failed to control the TB epidemic. Hunting for improved TB vaccine formulations represents a daunting task to TB research community. Anti-TB host defense requires T cell-mediated immunity and we are in desperate need of enhanced understanding of how to develop a new generation of TB vaccines that are able to provoke potent and long-lasting protective cell-mediated immunity, different from almost all of the vaccines currently in use. It is of importance to successful TB vaccine development to identify the key cellular and molecular events governing the generation of anti-TB immunity, but unfortunately little has been understood as to why 90% of infected humans never develop active TB. However, waiting would not help us to win the battle and an ever-intensifying effort is being made to develop various new formulations according to the immunology that we have been learning, in large part, from experimental models. This review article attempts to unite the current understanding of anti-TB immunity with the rational design of anti-TB vaccines. It examines what may have confounded the immunogenicity of current BCG vaccine and the major obstacles to successful development of TB vaccines. It also discusses about antigen presentation, activation of Th1 and Tc1 cells, anti-TB immune effectors and the generation of memory T cells. The vaccine section describes four types of major TB vaccines under development: mycobacterial-, subunit-, plasmid DNA- and viral-based vaccines. A special section is dedicated to the rationale and current design of cytokine-based adjuvant formulations for TB vaccines. We also take this opportunity to introduce our recent development in cytokine transgene adjuvanted BCG vaccination and recombinant adenoviral-based TB vaccines.

Antigens, Bacterial↗

PubMed2001

Breach of IL-12 monopoly in the initiation of type 1 immunity to intracellular infections: IL-12 is not required.

IL-12 is believed to play an important role in type 1 T-cell differentiation and type 1 cytokine IFN-gamma release by T- and NK-cells and macrophages in host defense against intracellular infections by bacteria, parasites, fungi and viruses. However, recent studies by us and others have provided unequivocal evidence that while IL- 12 is critically required for the development of type 1 immunity to the majority of intracellular bacterial, parasitic and fungal infections, it is not required for anti-viral type 1 immune responses. These findings have provoked our re-thinking about the role of IL-12 in type 1 immunity and the search for additional cytokines capable of initiating anti-viral type 1 immunity. We hypothesize that there exist multiple cytokines including IL-12 which play a redundant role in the initiation of type 1 immunity against viral infection. These cytokines are likely released from not only antigen-presenting macrophages/dendritic cells but many other cell types, which suits the mode of viral infection. The existence of multiple factors capable of driving type 1 immunity endows the host with additional safeguards to cope with prevalent viral foes.

Animals↗

PubMed2001

[Assay of trace elements and heavy metals in different growth stages of Ganoderma lucidum].

The trace elements and heavy metals in the different growth stages of Ganoderma lucidum were analyzed by ICP-MS, AFS and AAS. The fermented mycelia, fruiting bodies and spore contained all kinds of detected trace elements and heavy metals, the contents of which were higher in spore. The content of Se was same in different growth stages. Ganoderma lucidum had the ability of bio-enrichment of Ge.

Fruit↗

PubMed2001

[Linkage of allergic rhinitis with HLA-DRB alleles polymorphism].

OBJECTIVE: To investigate whether susceptibility or resistance to allergic rhinitis associated with HLA-DRB alleles. METHOD: Using PCR-SSP (sequence-specific primer polymerase chain reaction), we tested the frequency distribution of HLA-DRB alleles in 41 patients with allergic rhinitis (AR) and 41 healthy controls from Beijing China. RESULT: The frequence of HLA-DRB1 * 0301.2 and HLA-DRB4 * 0101 was lower in AR than in controls (2.44% vs 17.07%, P < 0.05; 29.27% vs 51.22%, P < 0.05). CONCLUSION: HLA-DRB1 * 0301.2 and HLA-DRB4 * 0101 alleles might confer protection against AR.

Adult↗

PubMed2001

[Endoscopic surgery for nasal inverted papilloma].

OBJECTIVE: To study and perfect the endoscopic surgery for nasal inverted papilloma(IP) and to decrease the recurrence after operation. METHODS: Forty-seven cases who were diagnosed as nasal IP were divided into two groups according to the tumor extension and operated upon and observed for 12-40 months (average 24.6 months). 51% of all cases had been operated on for 1-3 times before the treatment. Thirty-six cases in which the tumor had invaded the lateral nasal wall, middle meatus, partial or total ethmoid and/or sphenoid and infiltrated around the natural ostium of the maxillary sinus had performed transnasal endoscopic surgical procedures(TNESP). Another group (9 cases) in which involvement of the IP had further extended, into the maxillary sinus, had been treated by combination transnasal and Caldwell-Luc endoscopic surgical procedures (CTESP). In order to decrease bleeding during the operation, the body and bases of the IP were irradiated with YAG laser. The tumor was removed using the shaver system. The bony attachment of the IP and neighboring tissues were irradiated in all cases. RESULTS: Forty-five (95.7%) cases were not recurrent. The recurrence of the IP was identified in two cases (4.3%). But in 6 cases (12.8%), during postoperative follow-up management (1-3 months postoperatively) small mass of the IP (pathologically identified) were observed and removed and irradiated with YAG laser immediately. The recurrence was not observed in the one year follow-up period. CONCLUSION: Endoscopic surgical technique combining the irradiation of YAG laser and the application of shaver system is recommended. This procedure was effective and led to a decreased recurrence rate.

Adolescent↗

PubMed2000

IL-10 is necessary for the expression of airway hyperresponsiveness but not pulmonary inflammation after allergic sensitization.

Cytokines play an important role in modulating inflammatory responses and, as a result, airway tone. IL-10 is a regulatory cytokine that has been suggested for treatment of asthma because of its immunosuppressive and anti-inflammatory properties. In contrast to these suggestions, we demonstrate in a model of allergic sensitization that mice deficient in IL-10 (IL-10-/-) develop a pulmonary inflammatory response but fail to exhibit airway hyperresponsiveness in both in vitro and in vivo assessments of lung function. Reconstitution of these deficient mice with the IL-10 gene fully restores development of airway hyperresponsiveness comparable to control mice. These results identify an important role of IL-10, downstream of the inflammatory cascade, in regulating the tone of the airways after allergic sensitization and challenge.

Aerosols↗

PubMed2000

Transgenic expression of granulocyte-macrophage colony-stimulating factor induces the differentiation and activation of a novel dendritic cell population in the lung.

The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the differentiation of dendritic cells (DCs) during pulmonary viral infection was investigated by using a mouse model of GM-CSF transgene expression established with an adenoviral vector (AdGM-CSF). GM-CSF gene transfer resulted in increased levels of GM-CSF in the lung, which peaked at day 4 and remained increased up to day 19. A striking cellular response composed predominantly of macrophage-like cells was observed in the lung receiving AdGM-CSF but not control vector. By FACS analysis, the majority of these cells were identified at an early time point as macrophages and later as mature/activated myeloid DCs characterized by CD11b(bright), CD11c(bright), MHC class II(bright), and B7.1(bright). In contrast, GM-CSF had a weak effect on a small DC population that was found present in normal lung and was characterized by CD11c(bright) and CD11b(low). By immunohistochemistry staining for MHC II, the majority of activated antigen-presenting cells were localized to the airway epithelium and peribronchial/perivascular areas in the lung. A concurrently enhanced Th1 immune response was observed under these conditions. The number of CD4 and CD8 T cells was markedly increased in the lung expressing GM-CSF, accompanied by increased release of interferon (IFN)gamma in the lung. Furthermore, lymphocytes isolated from either lung parenchyma or local draining lymph nodes of these mice but not the control mice released large amounts of IFNgamma on adenoviral antigen stimulation in vitro. These findings reveal that GM-CSF promotes the differentiation and activation of a myeloid DC population primarily by acting on macrophages during pulmonary immune responses.

Adenoviridae↗

PubMed2000

IL-12-independent Th1-type immune responses to respiratory viral infection: requirement of IL-18 for IFN-gamma release in the lung but not for the differentiation of viral-reactive Th1-type lymphocytes.

We demonstrated that IL-12 was induced during primary or secondary pulmonary adenoviral infection in wild-type (wt) mice. However, cellular responses were not compromised in the lungs of IL-12-/- mice. The level of IFN-gamma in the lung was similar in wt and IL-12-/- mice during pulmonary viral infection. Upon Ag stimulation in vitro, lymphocytes from draining lymph nodes or spleen of infected IL-12-/- mice released large amounts of IFN-gamma, but not IL-4, which were comparable to those released by wt lymphocytes. Furthermore, a predominantly IgG2a response to adenoviral infection was unimpaired in IL-12-/- mice. These significant anti-adenoviral Th1-type responses in IL-12-/- mice led to an efficient clearance of virus-infected cells in the lung. Whether IL-18 was involved in IL-12-independent anti-adenoviral immune responses was investigated. Abrogation of endogenous IL-18 by an Ab resulted in diminished IFN-gamma release and lymphocytic infiltrate in the lung during adenoviral infection. Nevertheless, the development of lymphocytes of the Th1 phenotype was unimpaired in the absence of both IL-12 and IL-18. In contrast to their intact ability to mount Th1-type responses to viral infection, IL-12-/- mice suffered impaired Th1-type immune responses to pulmonary mycobacterial infection. Our findings suggest that IL-12, although induced, is not required for Th1-type responses to respiratory viral infection, in contrast to mycobacterial infection. IL-18 is required for the optimal release of IFN-gamma in the lung during viral infection, but is not required for the generation of virus-reactive Th1-type lymphocytes. Th1 differentiation during respiratory adenoviral infection may involve molecules different from IL-12 or IL-18.

Adenoviridae Infections↗

PubMed2000

Intra-articular IL-10 gene transfer regulates the expression of collagen-induced arthritis (CIA) in the knee and ipsilateral paw.

We studied the effects of local IL-10 application, introduced by a recombinant human type 5 adenovirus vector, in the mouse knee joint during the early phase of CIA. One intra-articular injection with the IL-10-expressing virus (Ad5E1mIL-10) caused substantial over-expression of IL-10 in the mouse knee joint, using virus dosages which did not induce distracting inflammation. High expression of IL-10 was noted for a few days, being maximal at day 1. One intra-articular injection of Ad5E1mIL-10 in the knee joints of collagen type II (CII)-immunized mice, before onset of CIA was noted, reduced the incidence of collagen arthritis in that knee. Of high interest, the protective effect of local IL-10 expression by Ad5E1mIL-10 was not restricted to the knee joint alone. The arthritis incidence in the ipsilateral paw was highly suppressed. In contrast, local IL-10 over-expression was not effective when treatment was started after onset of CIA. Further analysis in the acute streptococcal cell wall-induced arthritis model revealed that local IL-10 over-expression markedly suppressed the production of tumour necrosis factor-alpha (TNF-alpha) and IL-1alpha, but had no significant effect on IL-1beta and IL-12 production in the inflamed synovium. These data indicate that local over-expression of IL-10 in the knee joint of mice regulates the expression of collagen arthritis, probably through down-regulation of TNF-alpha.

Adenoviruses, Human↗

PubMed2000

Expression of cytokine genes in Marek's disease virus-infected chickens and chicken embryo fibroblast cultures.

The role of cytokines in the pathogenesis and immunity of Marek's disease (MD), a herpesvirus-induced T-cell lymphoma in chickens, is poorly understood. Two different experiments were used to examine the potential role of particular cytokines in the pathogenesis and immune responses of MD. First, chicken embryo fibroblasts (CEF) were stimulated with lipopolysaccharide (LPS) and/or recombinant chicken interferon-gamma (rChIFN-gamma) and used to develop techniques for examining transcription of IFN-alpha, IFN-gamma, inducible nitric oxide synthase (iNOS), interleukin (IL)-1beta, IL-2, IL-6 and IL-8 by reverse transcription-polymerase chain reaction (RT-PCR). Addition of LPS and/or rChIFN-gamma resulted in the up-regulation of mRNA for iNOS, IL-1beta and IL-6, while IFN-gamma was up-regulated by LPS alone. IL-2 was down-regulated by the treatments. Second, to determine the effects of Marek's disease herpesvirus (MDV) infection on cytokine transcription in vivo, chickens were infected with MDV at 21 days of age and examined at 7 days post-infection (p.i.) (exp. 1) or were infected with MDV at 1 day of age and examined from 3 to 15 days p.i. (exp. 2). In MDV-infected chickens, IFN-gamma transcription was up-regulated as early as 3 days p.i. until the termination of the experiment at 15 days p.i., while iNOS and IL-1beta were up-regulated between 6 and 15 days p.i. Infection of 1-day-old chicks increased levels of mRNA for IFN-gamma and iNOS between 16- and 64-fold at 9 days p.i. These results suggest that IFN-gamma and iNOS may play an important role in the pathogenesis of MD.

Animals↗

PubMed2000

Contrasting effects of myeloid dendritic cells transduced with an adenoviral vector encoding interleukin-10 on organ allograft and tumour rejection.

Mouse bone marrow-derived myeloid dendritic cells (DC) propagated in granulocyte-macrophage colony-stimulating factor and transforming growth factor-beta1 (TGF-beta1) (so-called 'TGF-beta DC') are phenotypically immature, and prolong allograft survival. Interleukin-10 (IL-10) has been shown to inhibit the maturation of DC by down-regulating surface major histocompatibility complex (MHC) class II, co-stimulatory and adhesion molecule expression. Genetic engineering of TGF-beta DC to overexpress IL-10 might enhance their tolerogenic potential. In this study, adenoviral (Ad) vectors encoding the mouse IL-10 gene were transduced into B10 (H2b) TGF-beta DC. Transduction with Ad-IL-10 at a multiplicity of infection (MOI) of 50-100 resulted in a modest reduction in the incidence of DC expressing surface MHC class II, CD40, CD80 and CD86. Paradoxically, Ad-IL-10 transduction enhanced the allostimulatory activity of DC in mixed leucocyte reactions and cytotoxic T lymphocyte assays, and increased their natural killer cell stimulatory activity. Systemic injection of normal C3H recipients with Ad-IL-10-transduced B10-DC 7 days before organ transplantation, exacerbated heart graft rejection and augmented circulating anti-donor alloantibody titres. Contrasting effects were observed in relation to tumour growth. All mice preimmunized with Ad-IL-10-transduced, tumour antigen (B16F10)-pulsed DC developed palpable tumours, associated with significant inhibition of splenic anti-tumour cytotoxic T lymphocyte generation. Animals pretreated with control Ad-LacZ-transduced, B16F10-pulsed DC however, remained tumour free. These findings are consistent with the multifunctional immunomodulatory properties of mammalian IL-10.

Adenoviruses, Human↗

PubMed2000

Genetically determined disparate innate and adaptive cell-mediated immune responses to pulmonary Mycobacterium bovis BCG infection in C57BL/6 and BALB/c mice.

The current study was designed to investigate the impact of genetic heterogeneity on host immune responses to pulmonary intracellular infection by using two mouse strains of distinct genetic background, C57BL/6 and BALB/c mice, and a model intracellular pathogen, Mycobacterium bovis BCG. Upon infection, compared to C57BL/6 mice, BALB/c mice developed an earlier response of interleukin 12 (IL-12), gamma interferon (IFN-gamma), tumor necrosis factor alpha, and macrophage chemoattractive protein 1, and greater neutrophilic influx to the lung by days 7 and 14. However, the level of these cytokines at days 27, 43, and 71 was much lower in BALB/c mice than in C57BL/6 mice. The magnitude of cellular responses was also much lower in the lung of BALB/c mice around day 27. Histologically, while C57BL/6 mice developed lymphocytic granulomas, BALB/c mice displayed atypical granulomas in the lung. Of importance, the level of type 2 cytokines IL-4 and IL-10 remained low and similar in the lung of both C57BL/6 and BALB/c mice throughout. Furthermore, lymphocytes isolated from systemic and local lymphoid tissues of infected BALB/c mice demonstrated a markedly lower antigen-specific IFN-gamma recall response. While the number of mycobacterial bacilli recovered from both the lung and spleen of BALB/c mice was similar to that in C57BL/6 mice at day 14, it was higher than that in C57BL/6 mice at day 43. However, it was eventually leveled off to that in C57BL/6 counterparts later. These results suggest the following: (i) genetic heterogeneity can lead to differential innate and adaptive cell-mediated immune responses to primary pulmonary mycobacterial infection; (ii) it is the level of adaptive, but not innate, immune response that is critical to host resistance; and (iii) a lower type 1 immune response in BALB/c mice is not accompanied by a heightened type 2 response during pulmonary mycobacterial infection.

Animals↗

PubMed2000

Inhibitory effects of nitric oxide and gamma interferon on in vitro and in vivo replication of Marek's disease virus.

The replication of Marek's disease herpesvirus (MDV) and herpesvirus of turkeys (HVT) in chicken embryo fibroblast (CEF) cultures was inhibited by the addition of S-nitroso-N-acetylpenicillamine, a nitric oxide (NO)-generating compound, in a dose-dependent manner. Treatment of CEF culture, prepared from 11-day-old embryos, with recombinant chicken gamma interferon (rChIFN-gamma) and lipopolysaccharide (LPS) resulted in production of NO which was suppressed by the addition of N(G)-monomethyl L-arginine (NMMA), an inhibitor of inducible NO synthase (iNOS). Incubation of CEF cultures for 72 h prior to treatment with rChIFN-gamma plus LPS was required for optimal NO production. Significant differences in NO production were observed in CEF derived from MDV-resistant N2a (major histocompatibility complex [MHC], B(21)B(21)) and MDV-susceptible S(13) (MHC, B(13)B(13)) and P2a (MHC, B(19)B(19)) chickens. N2a-derived CEF produced NO earlier and at higher levels than CEF from the other two lines. The lowest production of NO was detected in P2a-derived CEF. NO production in chicken splenocyte cultures followed a similar pattern, with the highest levels of NO produced in cultures from N2a chickens and the lowest levels produced in cultures from P2a chickens. Replication of MDV and HVT was significantly inhibited in CEF cultures treated with rChIFN-gamma plus LPS and producing NO. The addition of NMMA to CEF treated with rChIFN-gamma plus LPS reduced the inhibition. MDV infection of chickens treated with S-methylisothiourea, an inhibitor of iNOS, resulted in increased virus load compared to nontreated chickens. These results suggest that NO may play an important role in control of MDV replication in vivo.

Aging↗