Potentiation of humoral immune responses to vaccine antigens by recombinant chicken IL-18 (rChIL-18)

Mammalian interleukin-18 (IL-18) is one of the pro-inflammatory cytokines involved in innate immune responses to microbial infection preceding the induction of both cellular and humoral immune responses. We assessed the potential of Escherichia coli-expressed His-tag purified recombinant chicken IL-18 (rHis-ChIL-18) as a potentiator of vaccine-induced immune responses in 3 week-old SPF chickens and compared it with several commonly used traditional immunostimulating adjuvants. We found that rHis-ChIL-18 significantly enhanced antibody responses to Clostridium perfringens alpha-toxoid and Newcastle disease virus (NDV) antigens, comparable to the Al(OH)3-gel, Miglyol and chitosan adjuvant. However, antibody responses were lower than water-in-oil (w/o) emulsions and combinations of rHis-ChIL-18 with Al(OH)3-gel, Miglyol or chitosan. Improved HI-titers for infectious bronchitis virus (IBV) were not noted. We conclude that rHis-ChIL-18, when delivered in the proper context, is a novel and safe immunostimulator in chickens.     

Ascaridia galli infection influences the development of both humoral and cell-mediated immunity after Newcastle Disease vaccination in chickens

Potent vaccine efficiency is crucial for disease control in both human and livestock vaccination programmes. Free range chickens and chickens with access to outdoor areas have a high risk of infection with parasites including Ascaridia galli, a gastrointestinal nematode with a potential influence on the immunological response to vaccination against other infectious diseases. The purpose of this study was to investigate whether A. galli infection influences vaccine-induced immunity to Newcastle Disease (ND) in chickens from an MHC-characterized inbred line. Chickens were experimentally infected with A. galli at 4 weeks of age or left as non-parasitized controls. At 10 and 13 weeks of age half of the chickens were ND-vaccinated and at 16 weeks of age, all chickens were challenged with a lentogenic strain of Newcastle disease virus (NDV). A. galli infection influenced both humoral and cell-mediated immune responses after ND vaccination. Thus, significantly lower NDV serum titres were found in the A. galli-infected group as compared to the non-parasitized group early after vaccination. In addition, the A. galli-infected chickens showed significantly lower frequencies of NDV-specific T cells in peripheral blood three weeks after the first ND vaccination as compared to non-parasitized chickens. Finally, A. galli significantly increased local mRNA expression of IL-4 and IL-13 and significantly decreased TGF-ß4 expression in the jejunum two weeks after infection with A. galli. At the time of vaccination (six and nine weeks after A. galli infection) the local expression in the jejunum of both IFN-? and IL-10 was significantly decreased in A. galli-infected chickens. Upon challenge with the NDV LaSota strain, viral genomes persisted in the oral cavity for a slightly longer period of time in A. galli-infected vaccinees as compared to non-parasitized vaccinees. However, more work is needed in order to determine if vaccine-induced protective immunity is impaired in A. galli-infected chickens.     

Immunization of cattle with recombinant Newcastle disease virus expressing bovine herpesvirus-1 (BHV-1) glycoprotein D induces mucosal and serum antibody responses and provides partial protection against BHV-1

Bovine herpesvirus-1 (BHV-1) is a major cause of respiratory tract diseases in cattle. Vaccination of cattle against BHV-1 is a high priority. A major concern of currently modified live BHV-1 vaccines is their ability to cause latent infection and subsequent reactivation resulting in many outbreaks. Thus, there is a need for alternative strategies. We generated two recombinant Newcastle disease viruses (NDVs) expressing the glycoprotein D (gD) of BHV-1 from an added gene. One recombinant, rLaSota/gDFL, expressed gD without any modification. The other recombinant, rLaSota/gDF, expressed a chimeric gD in which the ectodomain of gD was fused with the transmembrane domain and cytoplasmic tail of the NDV fusion F glycoprotein. Remarkably, the native gD expressed by rLaSota/gDFL virus was incorporated into the NDV virion 2.5-fold more efficiently than the native NDV proteins, whereas the chimeric gD was not detectably incorporated even though it was abundantly expressed on the infected cell surface. The expression of gD did not increase the virulence of the rNDV vectors in chickens. A single intranasal and intratracheal inoculation of calves with either recombinant NDV elicited mucosal and systemic antibodies specific to BHV-1, with the responses to rLaSota/gDFL being higher than those to rLaSota/gDF. Following challenge with BHV-1, calves immunized with the recombinant NDVs had lower titers and earlier clearance of challenge virus compared to the empty vector control, and reduced disease was observed with rLaSota/gDFL. Following challenge, the titers of serum antibodies specific to BHV-1 were higher in the animals immunized with the rNDV vaccines compared to the rNDV parent virus, indicating that the vaccines primed for secondary responses. Our data suggest that NDV can be used as a vaccine vector in bovines and that BHV-1 gD may be useful in mucosal vaccine against BHV-1 infection, but might require augmentation by a second dose or the inclusion of additional BHV-1 antigens.     

Regulatory Effects of Quercetin on M1/M2 Macrophage Polarization and Oxidative/Antioxidative Balance

Macrophage polarization plays essential and diverse roles in most diseases, such as atherosclerosis, adipose tissue inflammation, and insulin resistance. Homeostasis dysfunction in M1/M2 macrophage polarization causes pathological conditions and inflammation. Neuroinflammation is characterized by microglial activation and the concomitant production of pro-inflammatory cytokines, leading to numerous neurodegenerative diseases and psychiatric disorders. Decreased neuroinflammation can be obtained by using natural compounds, including flavonoids, which are known to ameliorate inflammatory responses. Among flavonoids, quercetin possesses multiple pharmacological applications and regulates several biological activities. In the present study, we found that quercetin effectively inhibited the expression of lipocalin-2 in both macrophages and microglial cells stimulated by lipopolysaccharides (LPS). The production of nitric oxide (NO) and expression levels of the pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, were also attenuated by quercetin treatment. Our results also showed that quercetin significantly reduced the expression levels of the M1 markers, such as interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β, in the macrophages and microglia. The M1 polarization-associated chemokines, C–C motif chemokine ligand (CCL)-2 and C-X-C motif chemokine ligand (CXCL)-10, were also effectively reduced by the quercetin treatment. In addition, quercetin markedly reduced the production of various reactive oxygen species (ROS) in the microglia. The microglial phagocytic ability induced by the LPS was also effectively reduced by the quercetin treatment. Importantly, the quercetin increased the expression levels of the M2 marker, IL-10, and the endogenous antioxidants, heme oxygenase (HO)-1, glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modifier subunit (GCLM), and NAD(P)H quinone oxidoreductase-1 (NQO1). The enhancement of the M2 markers and endogenous antioxidants by quercetin was activated by the AMP-activated protein kinase (AMPK) and Akt signaling pathways. Together, our study reported that the quercetin inhibited the effects of M1 polarization, including neuroinflammatory responses, ROS production, and phagocytosis. Moreover, the quercetin enhanced the M2 macrophage polarization and endogenous antioxidant expression in both macrophages and microglia. Our findings provide valuable information that quercetin may act as a potential drug for the treatment of diseases related to inflammatory disorders in the central nervous system.     

Molecular and phylogenetic characterization based on the complete genome of a virulent pathotype of Newcastle disease virus isolated in the 1970s in Brazil

Newcastle disease (ND) is caused by the avian paramyxovirus type 1 (APMV-1) or Newcastle disease virus (NDV) that comprises a diverse group of viruses with a single-stranded, negative-sense RNA genome. ND is one of the most important diseases of chickens, because it severely affects poultry production worldwide. In the 1970s, outbreaks of virulent ND were recorded in Brazil, and the strain APMV-1/Chicken/Brazil/SJM/75 (SJM) of NDV was isolated. This strain was characterized as highly pathogenic for chickens but not pathogenic for other bird species. Here we present the complete genome of NDV strain SJM and investigate the phylogenetic relationships of this virus with other NDV strains in terms of genome and proteins composition, as well as characterizing its evolution process. The NDV strain SJM is categorized as a velogenic virus and the complete genome is 15,192 nucleotides in length, consisting of six genes in the order 3′-NP-P-M-F-HN-L-5′. The presence of the major pathogenic determinant of NDV strains (¹¹²R-R-Q-K-R↓F¹¹⁷) was identified in the Fusion protein of the NDV strain SJM. In addition, phylogenetic analysis classified the NDV strain SJM as a member of class II, genotype V, and indicates that this virus help us in the understanding of the evolutionary process of strains belonging to this genotype. This study contributes to the growing interest involving the characterization of NDV isolates to improve our current understanding about the epidemiology, surveillance and evolution of the pathogenic strains.     

Characterization of thermostable Newcastle disease virus recombinants expressing the hemagglutinin of H5N1 avian influenza virus as bivalent vaccine candidates

Newcastle disease virus (NDV) has been used as a vector in the development of vaccines and gene delivery. In the present study, we generated the thermostable recombinant NDV (rNDV) expressing the different forms of hemagglutinin (HA) of highly pathogenic avian influenza virus (HPAIV) H5N1 based on the full-length cDNA clone of thermostable TS09-C strain. The recombinant thermostable Newcastle disease viruses, rTS-HA, rTS-HA1 and rTS-tPAs/HA1, expressed the HA, HA1 or modified HA1 protein with the tissue plasminogen activator signal sequence (tPAs), respectively. The rNDVs displayed similar thermostability, growth kinetics and pathogenicity compared with the parental TS09-C virus. The tPAs facilitated the expression and secretion of HA1 protein in cells infected with rNDV. Animal studies demonstrated that immunization with rNDVs elicited effective H5N1- and NDV-specific antibody responses and conferred immune protection against lethal H5N1 and NDV challenges in chickens and mice. Importantly, vaccination of rTS-tPAs/HA1 resulted in enhanced protective immunity in chickens and mice. Our study thus provides a novel thermostable NDV-vectored vaccine candidate expressing a soluble form of a heterologous viral protein, which will greatly aid the poultry industry in developing countries.     

The interaction between vitamin A status and Newcastle disease virus infection in chickens

Newcastle disease virus (NDV) infection in chickens differing in vitamin A status has been selected as a model to examine the interrelationship between marginal vitamin A deficiency and the severity of consequences of measles infection in humans. Day-old chickens with limited vitamin A reserves, the progeny of marginally vitamin A-deficient hens, were fed purified diets containing either marginal (120 retinol equivalents/kg diet, ad libitum) or adequate (1200 retinol equivalents/kg diet, ad libitum or pair-fed) levels of vitamin A for a period of 10 wk. At 4 wk of age, half of the chickens in each group were infected intraocularly with the lentogenic, i.e., mildly pathogenic, La Sota strain of NDV. Within 1 wk of infection, plasma retinol levels in the infected, marginally vitamin A-deficient chickens showed a significant and persistent decrease compared to their noninfected counterparts fed the same diet. Moreover, infection with NDV resulted in increased rates of morbidity in the marginally vitamin A-deficient chickens compared with nondeficient chickens. The results of this study indicate that pre-existing marginal vitamin A status increases the severity of disease following NDV infection, and that infection with NDV reduces marginal plasma vitamin A levels to levels which can be regarded as deficient.     

mRNA expression and functional analysis of chicken IFIT5 after infected with Newcastle disease virus

Innate immunity is the first line against the invasion of pathogenic microorganisms. Over the past several years, the antiviral activity and mechanisms of the IFIT5 gene have been confirmed in mammals. However, more information is needed on the role of IFIT5 in response to viral infection in chickens. In this study, we examined the mRNA expression profile of chicken IFIT5 (chIFIT5) in different tissues and explored how chIFIT5 transduces upstream signaling to the downstream adaptor. Relative mRNA expression level of chIFIT5 was the highest in spleen and expression level of chIFIT5 was significantly up-regulated following Newcastle disease virus (NDV) infection, and polyinosinic:polycytidylic acid [poly (I:C)]- and poly(deoxyadenylic-thymidylic) [poly (dA:dT)]-triggered antiviral immune responses. Chicken MDA5, MAVS, and IRF7 positively regulated the mRNA expression of chIFIT5. Overexpression of chIFIT5 could promote IRF7- and NF-κB-mediated gene expression following NDV infection or transfection with poly (I:C). These results suggested that chIFIT5 is an important enhancer of the innate immunity response.     

Cytokine gene haplotypes with a potential effect on susceptibility to malaria in sympatric ethnic groups in Mali

Cytokines are important players in the immune responses, and an unbalance in pro- and anti-inflammatory cytokine responses may affect parasitemia and pathology in a Plasmodium falciparum infection. Polymorphisms in cytokine genes may affect not only the levels of the protein, but many down-stream functions, such as production of C-reactive protein and immunoglobulin isotype switching. Susceptibility to malaria has been shown to differ between individuals with different genetic backgrounds, as indicated by studies in Fulani and non-Fulani ethnic groups. The aim of this study was to investigate possible interethnic differences in totally twelve single nucleotide polymorphisms (SNPs) in the genes encoding the cytokines IL-1β, IL-6, IL-10 and TNF. These SNPs are present in the promoter region of the genes, and have previously been associated with cytokine expression and with disease outcome in malaria. The results from the present study suggest that the Fulani ethnic group has a more pro-inflammatory response, due to high frequencies of high-producing alleles of IL1β and low-producing alleles of IL10. IL-6 could potentially also contribute to the relatively lower susceptibility to malaria in the Fulani ethnic group, whereas the TNF polymorphisms analysed in this study rather seem to associate with the severity of the infection and not the susceptibility for the infection itself. We therefore suggest that the polymorphisms analysed in this study all show a potential to influence the relatively lower susceptibility to malaria seen in the Fulani ethnic group as compared to the other sympatric ethnic groups.     

腹主动脉瘤腔内修复术后感染病原菌及Hippo信号通路基因改变

目的探讨腹主动脉瘤腔内修复术(EVAR)后医院感染病原特点及Hippo信号通路基因、白细胞介素-17(Interleukin-17,IL-17)、IL-23改变。方法选择天津医院血管外科2017年5月-2020年3月收治腹主动脉瘤EVAR术后医院感染患者49例作为感染组,选择同期医院进行EVAR术后未发生医院感染患者60例作为非感染组。采用实时荧光定量逆转录聚合酶链反应(RT-PCR)法检测Hippo通路基因yap、taz、mst1相对表达水平,采用酶联免疫吸附法检测其辅助型T细胞17(Th17)促炎细胞因子白细胞介素-17(IL-17)、IL-23水平。结果49例患者共发生肺部感染33例(67.35%),尿路感染10例(20.41%),手术切口感染4例(8.16%),移植物感染2例(4.08%);感染病原以革兰阳性菌为主,共25株,占51.02%,革兰阴性菌共22株,占44.90%,真菌2株,占4.08%;感染组yap、taz、mst1基因相对表达水平和IL-17、IL-23水平高于非感染组(P<0.05)。结论腹主动脉瘤EVAR术后医院感染以肺部感染、尿路感染为主,应及时予以针对性预防;Hippo通路参与了感染发生过程,通过Th17促炎途径诱导炎症反应,其机制仍有待研究。     

Helicobacter pylori seropositive subjects do not show a pronounced systemic inflammatory response even in the presence of the interleukin-1 receptor antagonist gene polymorphism

The aim of this analysis was to evaluate the effects of the presence of the IL-1RA gene polymorphism and H. pylori infection on markers of a systemic inflammatory response taking into account virulence markers of this infection. Serum concentrations of interleukin (IL)-6, IL-8, and tumour-necrosis factor (TNF)-alpha of 479 occasional blood donors were not statistically significantly higher in subjects having antibodies against H. pylori, or more specifically against CagA and VacA, and being homozygous for the pro-inflammatory IL-1RN*2 allele compared to others after adjustment for covariates. The findings suggest that the possible pro-inflammatory effect of the IL-1RN*2 allele in combination with H. pylori infection is limited to the mucosal level.     

Ginseng and Salviae herbs play a role as immune activators and modulate immune responses during influenza virus infection

We have investigated the adjuvant roles of common herbal medicines (ginseng, Salviae) and their effects on early immune responses during influenza virus infection in a mouse model. Intranasal co-administration with inactivated influenza virus A (PR8) and ginseng or Salviae extract increased the levels of influenza virus specific antibodies and neutralizing activities compared to immunization with PR8 alone, and provided protective immunity. Salviae co-administration significantly enhanced IFN-gamma and IL-2 cytokine producing splenocytes while ginseng induced high levels of IL-4 and IL-5 cytokine producing cells after challenge infection. Cells expressing an early activation marker CD69 and levels of a pro-inflammatory cytokine IL-6 were highly elevated in lungs from na?ve mice during challenge virus infection, which might be a mechanism in lung inflammation leading to death. In contrast, immunized mice that were co-administered ginseng or Salviae modulated CD69 expressing immune cells, did not produce IL-6, and showed significant enhancement of influenza virus specific IgA antibody in lungs after challenge virus infection. Therefore, these results indicate that both ginseng and Salviae play a role as mucosal adjuvants against influenza virus as well as immuno-modulators during influenza virus infection.     

Restricted leptin antagonism as a therapeutic approach to treatment of autoimmune diseases

Leptin, the adipocyte derived hormone, has a pivotal role in regulating energy homeostasis and appetite. Beyond this essential role in bodyweight control, leptin also regulates the immune responses. Leptin has pro-inflammatory effects on T cell populations, shifting the T helper balance towards a TH1 phenotype, through induction of pro-inflammatory cytokines and stimulation of macrophage and natural killer cell function. Acute starvation reduces serum leptin levels, resulting in an impaired cellular immune response. The TH1 pro-inflammatory immune response, a homeostatic response mediated by the low leptin levels, is also impaired during starvation. Leptin-deficient or leptin receptor mutant mice are protected against the development of several inflammatory or various T cell-dependent autoimmune diseases. Therefore, leptin appears to have a central role in the immune response and low leptin levels may protect against autoimmune disease. Here we review the role of leptin in the immune responses, with emphasis on autoimmune diseases. We will also discuss the application of leptin antagonist therapy for prevention and treatment of immunity related disorders.     

Gene expression profiling in naïve and vaccinated rainbow trout after Yersinia ruckeri infection: insights into the mechanisms of protection seen in vaccinated fish

Despite the importance and success of vaccination against bacterial diseases in fish, little is known about the mechanisms of vaccine-induced disease resistance. In this study a known efficacious bacterial vaccine, to Enteric Redmouth Disease (ERM), was used to vaccinate rainbow trout, and sixty days later the fish were challenged with the causative agent of the disease, Yersinia ruckeri. The bacterial burden in the spleen, the spleen index, and the expression profiles of pro- and anti-inflammatory cytokines and marker genes for T helper (Th) cells in the spleen and gills were analyzed, in comparison to the profiles in naïve/challenged fish. As expected, the bacterial burden in the spleen of naïve fish increased over time and was correlated with the spleen index after Y. ruckeri challenge. The gene expression data showed that pro-inflammatory cytokines were upregulated post-infection in the spleen of both naïve and vaccinated fish after Y. ruckeri challenge although the pro-inflammatory cytokine expression was much lower in vaccinated fish compared to the naïve fish. A correlated expression between pro-inflammatory cytokines and anti-inflammatory cytokines was only seen in spleen of ERM vaccinated fish, where a Th1-like response was indicated by the correlated gene expression of IFN-γ, T-bet and IL-2. In contrast, in the gills, the inflammatory gene response was enhanced in vaccinated fish compared to naïve fish, but perhaps more importantly there was a strong upregulation of IL-22 which was negatively correlated with IFN-γ gene expression at this site. Thus, it is possible that different types of adaptive responses are on-going within the vaccinated fish during infection with Y. ruckeri, potentially affected by the site and stage of infection.     

Modulating effect of glutamine on IL-1beta-induced cytokine production by human gut

BACKGROUND & AIMS: Balance between pro-and anti-inflammatory mediators plays a key role in the pathogenesis and treatment of inflammatory bowel disease. Glutamine can modulate cytokine production by intestinal mucosa in healthy subjects, but studies in inflammatory states are still limited. The aim of this work was to evaluate the effects of glutamine on IL-1beta-induced cytokine production by human gut. METHODS: Duodenal biopsies from healthy volunteers were stimulated in vitro by IL-1beta in the presence of increasing glutamine concentrations. Cytokine production was assessed in culture media by ELISA and cytokine mRNA expression in biopsies by RT-PCR. Results, in pg/mg of tissue, (median [range]), were compared by non-parametric paired tests. RESULTS: IL-1beta stimulation increased IL-6 and IL-8, but did not affect IL-4 and IL-10 production. IL-8 and IL-6 production from stimulated biopsies significantly decreased with increasing glutamine concentration from 0.5 to 10mM, (2543 [828-3634] to 1499 [282-2617] for IL-8, 62 [22-117] to 24 [12-99] for IL-6, both P<0.05), whereas IL-10 production was increased (0.7 [0.2-1.6] to 1.2 [2.6-0.5],P<0.05). Glutamine also increased IL-10 mRNA level in biopsies (P<0.05). IL-4 production was not affected by glutamine. CONCLUSIONS: Glutamine was shown in human intestinal mucosa to reduce the production of the pro-inflammatory cytokines IL-6 and IL-8, and enhance the production of the anti-inflammatory cytokine, IL-10.     

A viral-vectored RSV vaccine induces long-lived humoral immunity in cotton rats

Human respiratory syncytial virus (RSV) is the leading cause of lower airway disease in infants worldwide and repeatedly infects immunocompetent individuals throughout life. Severe lower airway RSV infection during infancy can be life-threatening, but is also associated with important sequelae including development of asthma and recurrent wheezing in later childhood. The basis for the inadequate, short-lived adaptive immune response to RSV infection is poorly understood, but it is widely recognized that RSV actively antagonizes Type I interferon (IFN) production. In addition to the induction of the anti-viral state, IFN production during viral infection is critical for downstream development of robust, long-lived immunity. Based on the hypothesis that a vaccine that induced robust IFN production would be protective, we previously constructed a Newcastle disease virus-vectored vaccine that expresses the F glycoprotein of RSV (NDV-F) and demonstrated that vaccinated mice had reduced lung viral loads and an enhanced IFN-γ response after RSV challenge. Here we show that vaccination also protected cotton rats from RSV challenge and induced long-lived neutralizing antibody production, even in RSV immune animals. Finally, pulmonary eosinophilia induced by RSV infection of unvaccinated cotton rats was prevented by vaccination. Overall, these data demonstrate enhanced protective immunity to RSV F when this protein is presented in the context of an abortive NDV infection.     

Level of protection of chickens against highly pathogenic H5 avian influenza virus with Newcastle disease virus based live attenuated vector vaccine depends on homology of H5 sequence between vaccine and challenge virus

Vaccination of poultry against avian influenza is of high priority, in particular after the dramatic spread of subtype H5N1 in Asia, Africa and Europe. Newcastle disease virus (NDV) has been developed as a vector for the expression of the main immunogen of avian influenza virus, hemagglutinin (HA). An NDV vector based vaccine has several advantages. It allows easy serological differentiation between infected and vaccinated animals by the detection of antibodies against non-HA influenza proteins. Moreover, it can be administered easily to large numbers of animals by spray or drinking water. We recently showed that chickens could be protected against infection with highly pathogenic avian influenza virus (HPAIV) A/chicken/Italy/8/98 (H5N2) after immunization with a recombinant Newcastle disease virus, NDVH5m, which expresses the homologous hemagglutinin. Here, we describe that immunization with NDVH5m conferred only partial protection against lethal infection with heterologous HPAIV A/duck/Vietnam/TG24-01/05 (H5N1). Comparison of amino acid sequences of both H5 proteins showed only 93.6% amino acid identity. Therefore, a new NDV recombinant (NDVH5Vm) was generated which expresses the H5 protein of HPAIV A/chicken/Vietnam/P41/05 (H5N1). This recombinant virus protected chickens against lethal infection with HPAIV H5N1 (Vietnam) already after one immunization. Our data thus show that application of a vector-based vaccine in the control of influenza may require adaptation of the vaccine to currently circulating viruses.     

Avian paramyxovirus serotypes 2-9 (APMV-2-9) vary in the ability to induce protective immunity in chickens against challenge with virulent Newcastle disease virus (APMV-1)

The avian paramyxoviruses (APMVs) belong to the genus Avulavirus of family Paramyxoviridae. The APMVs are classified into nine serotypes on the basis of hemagglutination inhibition (HI) and neuraminidase inhibition (NI) assays, although some serologic cross-reaction exists. Newcastle disease virus (NDV), which constitutes serotype 1 (APMV-1), is an important pathogen of poultry, but the pathogenic potential of the other APMV serotypes is poorly understood. Although antibodies to APMV -2 to -9 are prevalent in chickens, the effect of prior exposure to these serotypes on susceptibility to NDV infection and disease was not known. In the present study, chickens were immunized with APMV-2 to -9 by the oculo-nasal route and later were challenged by the same route with a highly virulent strain of NDV. Among APMV-2 to -9, only APMV-3 induced serum antibodies that cross-reacted significantly with NDV and had significant NDV-neutralizing activity in vitro. In mock-immunized chickens, challenge NDV replicated throughout the respiratory tract as well as in the brain, spleen, and enteric tract. In contrast, in APMV-3-immunized chickens, challenge NDV replication was restricted to the upper respiratory tract and trachea. Some of the other APMVs also induced partial restriction of challenge NDV replication: for example, challenge NDV was not detected in the brains of APMV-9-immunized chickens, and shedding from the respiratory tract was reduced in chickens immunized with APMV-8 and -9. All of the chickens immunized with APMV-3 survived the NDV challenge; with APMV-2, -7, -8, and -9 the percentage survival was 30%, 20%, 20%, and 52.5%, respectively; whereas none of the chickens immunized with APMV-4, -5, or -6 survived. These results show that prior infection of chickens with APMV-3 induced substantial protection against NDV challenge, whereas prior infection with APMV-2, -7, -8, and -9 can alter subsequent NDV infection. The induction of NDV-neutralizing antibodies was a marker for efficient protection, but partial protection also was observed in their absence.