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Interaction between a live avian pneumovirus vaccine and two different Newcastle disease virus vaccines in broiler chickens with maternal antibodies to Newcastle disease virus.

Broiler chicks with maternal antibodies to Newcastle disease virus (NDV) but none to avian metapneumovirus (APV) were divided into six groups. One group was kept as an unvaccinated control group. Three of the other groups were vaccinated at 1 day old with live APV vaccine or one of two live NDV vaccines (VG/GA or HB1). The remaining two groups received the APV vaccine in combination with either of the two NDV vaccines at 1 day old. At intervals after vaccination for up to 42 days, distribution of the viruses in the tissues was monitored, together with humoral antibody responses. Few NDV isolations were made from any NDV-vaccinated chicks, probably due to the presence of NDV maternal antibodies. In both dual-vaccinated groups, APV persisted longer (up to 21 days post vaccination (d.p.v.)) than in the single vaccinates (up to 14 d.p.v.). After 14 d.p.v., antibody titres against APV in both dual-vaccinated groups remained higher than the single APV vaccinates. For NDV haemagglutination inhibition antibodies, similar titres were found in the single and dual NDV VG/GA vaccinates. However, for chickens dually vaccinated with NDV HB1 and APV, the haemagglutination inhibition titres were significantly higher at 21 and 28 d.p.v. than the single HB1 vaccinates. These differences reflect the fact that NDV haemagglutination inhibition titres may depend on the NDV vaccine used.

Animals↗

Isolation and characterization of defective interfering particle of Newcastle disease virus.

Newcastle disease virus grown in embryonated eggs was separated and purified by sucrose density gradient centrifugation into two distinct type of particles, B and T, the former being normal virus particles with high activities of hemagglutination, hemolysis, neuraminidase and infectivity, the latter being non-infectious virus particles with low activities of hemolysis and neuraminidase but high hemagglutination activity. B and T particles were shown to share a common antigen by immunodiffusion test. T particles were deficient in viral RNA, since they contained only 13s RNA in a small amount, whereas B particles possessed a large amount of 57s RNA and a small amount of 13s RNA. T particles interfered with the multiplication of normal Newcastle disease virus in primary cultures of chick embryo cells.

Animals↗

Isolation and biological properties of some Moroccan strains of Newcastle disease virus.

Newcastle disease virus was isolated from six field cases in Morocco. On the basis of the mean death time of chicken embryos, the intracerebral pathogenicity index, and plaque formation on chicken embryo fibroblast monolayers, five isolates were determined to be of the velogenic pathotype. One of these differed from the others in that it agglutinated equine erythrocytes. The sixth isolate was found to be of low virulence but differed from the vaccinal strain tested.

Animals↗

Vaccination with CDF-66 strain of newcastle disease virus.

Newcastle disease vaccine CDF-66 has been proved effective by the drinking water route. A chicken dose of 10(6.2) EID50 in 12 ml of water containing 2.5% skimmed milk was found to be effective. This produced sufficient GMHI antibody response (105) and 86.6% of birds withstood challenge with the Mukteswar strain of virulent virus. The in-contact birds did not show either immune or antibody response. The vaccinated birds excreted vaccine virus only from the respiratory tract not from cloaca. The vaccine given in drinking water protected only 50% of chickens when it was given 168 h prior to challenge virus. With lesser intervals the protection was negligible. Diluted vaccine when held for 2 h at 37 degrees C and room temperature did not show a drop in potency.

Animals↗

Serological profiles of commercial broiler breeders and their progeny. 2. Newcastle disease virus.

Newcastle disease virus (NDV) hemagglutination-inhibition (HI) titers were determined for serum samples from eight commercial broiler breeder flocks and their progeny. The chickens sampled had been vaccinated and reared by different producers in different regions of the United States. Breeder flocks had the highest number of NDV-positive HI titers (greater than or equal to 1:10). Eighty percent or more of the samples from six of eight breeder flocks were positive; the geometric mean titers (GMTs) for those six breeder flocks ranged from 19 to 92. Only 3 of 8 broiler flocks had an increased frequency of positive titers and higher GMTs after vaccination. The frequency of positive titers was greater than 80% in only 2 of 8 of the oldest broiler flocks. The number of NDV-negative titers (less than 1:10) increased with age in most broiler flocks, even though all had been vaccinated once or more with live NDV vaccines.

Animals↗

Role of fusion protein cleavage site in the virulence of Newcastle disease virus.

Newcastle disease virus (NDV) causes a highly contagious and economically important disease in poultry. Viral determinants of NDV virulence are not completely understood. The amino acid sequence at the protease cleavage site of the fusion (F) protein has been postulated as a major determinant of NDV virulence. In this study, we have examined the role of F protein cleavage site sequence in NDV virulence using reverse genetics technology. The sequence G-R-Q-G-R present at the cleavage site of the F protein of avirulent strain LaSota was mutated to R-R-Q-K-R, which is present in the F cleavage site of neurovirulent strain Beaudette C (BC). The resultant mutated LaSota V.F. virus did not require exogenous protease for infectivity in cell culture, indicating that the F protein was cleaved by intracellular proteases. The virulence of the mutant and parental viruses was evaluated in vivo by intracerebral pathogenicity index (ICPI) and intravenous pathogenicity index (IVPI) tests in chickens. Our results showed that the modification of the F protein cleavage site resulted in a dramatic increase in virulence from an ICPI value of 0.00 for LaSota to a value of 1.12 for LaSota V.F. However, the ICPI value of LaSota V.F. was lower than that of BC, which had a value of 1.58. Interestingly, the IVPI tests showed values of 0.00 for both LaSota and LaSota V.F. viruses, compared to the IVPI value of 1.45 of BC. In vitro characteristics of the viruses were also studied. Our results demonstrate that the efficiency of cleavage of the F protein plays an important role if the NDV is delivered directly into the brains of chicks, but there could be other viral factors that probably affect peripheral replication, viremia, or entry into the central nervous system.

Amino Acid Sequence↗

The resistance of meat chickens vaccinated by aerosol with a live V4 Newcastle disease virus vaccine in the field to challenge with a velogenic Newcastle disease virus.

Meat chickens housed on a commercial broiler farm in Australia were vaccinated once at 10 to 11 days-of-age by aerosol with live V4 Newcastle disease virus (NDV) vaccine. Groups of vaccinated and unvaccinated birds were flown to Malaysia, where they were challenged with a virulent strain of NDV. Survival rates in vaccinated chickens challenged 7, 14, 21 or 31 d after vaccination were 0.47, 0.77, 0.97 and 0.92, respectively. All unvaccinated chickens died due to Newcastle disease (ND) following challenge. Chickens in Australia and Malaysia were bled and the serums tested for haemagglutination-inhibiting (HI) antibody to NDV. Many vaccinated birds with no detectable antibody, and all birds with a log2 titre of 2 or greater, survived challenge. The results showed that this V4 vaccine induced protective immunity in a significant proportion of chickens within 7 d of mass aerosol vaccination. This early immunity occurred in the absence of detectable circulating HI antibody. Non-HI antibody mediated immunity continued to provide protection up to 31 d after vaccination. Almost all vaccinated birds were protected within 3 w of vaccination. It is concluded that the V4 vaccine is efficacious and could be useful during an outbreak of virulent ND in Australia.

Aerosols↗

Comparison of RNA polymerase associated with Newcastle disease virus and a temperature-sensitive mutant of Newcastle disease virus isolated from persistently infected L cells.

An in vitro comparison was made of the RNA polymerase activity associated with Newcastle disease virus (NDVo) and three clones of the temperature-sensitive mutant (NDVpi) isolated from persistently infected L cells. Less polymerase activity was associated with the NDVpi clones. Also, compared to NDVo, an increase in incubation temperature from 32 to 37 or 42 C resulted in a marked decrease in polymerase activity for the temperature-sensitive mutants which coincided with their inability to replicate at 42 C.

Cell-Free System↗

Immune responses of breeding chickens to trivalent oil emulsion vaccines: responses to Newcastle disease and infectious bursal disease.

Bivalent Newcastle disease (ND)/infectious bursal disease (IBD) and trivalent ND/IBD/infectious bronchitis (IB) inactivated oil emulsion vaccines were prepared in the laboratory and evaluated under field conditions. Broiler breeder parent chickens previously vaccinated with live vaccines were inoculated with commercial monovalent ND and experimental bivalent or trivalent oil emulsion vaccines. The commercial vaccine induced a higher initial ND haemagglutination inhibition (HI) response than the experimental vaccines but, by 34 weeks after vaccination, the mean ND HI levels were not significantly different in any of the three flocks. All three vaccines provided sufficient ND immunity to protect against the clinical disease and egg production losses. The IBD responses of both flocks vaccinated with oil emulsion vaccine were similar to each other and only slightly lower than those flocks vaccinated with monovalent IBD oil emulsion vaccine in earlier experiments. Six weeks after vaccination, sufficient immunity was transferred to protect all the progeny against IBD challenge up to 33 days of age and some of them up to 45 days of age. Thirty-four weeks after vaccination of the parents with oil emulsion vaccine, the progeny were totally immune up to 27 days of age and some of them were immune until 37 days. Application of oil emulsion vaccines in bivalent or trivalent form did not impair the responses of the chickens to the monovalent components.

Animals↗

Vaccination with Newcastle disease vaccine and CpG oligodeoxynucleotides induces specific immunity and protection against Newcastle disease virus in SPF chicken.

Oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) have been proven to be immunoprotective in mouse models. However, little work has been conducted on in vivo immune responses in chicken with CpG ODN. The objective of this study was to investigate the immunoadjuvant effects of CpG ODN to Newcastle disease (ND) vaccine and its protective effects against ND virus in SPF chicken. In this report, the titre of serum IgG to ND vaccine and the proliferation of lymphocytes were monitored in SPF chickens. The results demonstrated that the above-mentioned immune responses were significantly stronger in chickens that received CpG ODN than in the birds that received only ND vaccine. Furthermore, ND vaccine plus CpG ODN protected SPF chicken from challenge with an otherwise lethal dose of ND virus. These data suggest that CpG ODN holds considerable promise as an adjuvant for future vaccines against ND virus.

Adjuvants, Immunologic↗

Genetic and phenotypic correlations between antibody responses to Escherichia coli, infectious bursa disease virus (IBDV), and Newcastle disease virus (NDV), in broiler lines selected on antibody response to Escherichia coli.

The genetic control of antibody (Ab) response to Escherichia coli (EC), infectious bursa disease virus, and Newcastle disease virus and the genetic and phenotypic correlation between these Ab responses, were evaluated under farm conditions in which chicks were simultaneously exposed to these antigens. The experimental population comprised five groups: two lines divergently selected for high (HH) or low (LL) Ab response to EC vaccination; a commercial broiler dam-line (CC), from which HH and LL had been derived; and the HH x CC and LL x CC hybrid groups (HC and LC, respectively). Lines LL and HH expressed similar symmetric divergence to all three antigens. The ranking of the LL, LC, CC, HC, and HH genetic groups according to their mean Ab responses and their very high linear correlation with the LL vs. HH genomic scale clearly indicate the additive nature of the genetic divergence between these lines. Several estimates of correlation were calculated between Ab responses of each pair of antigens and between BW and Ab to each antigen. The high correlation between group means, the near-zero within-group correlation, and the low phenotypic correlation indicate the strongly positive genetic correlation between Ab responses and no correlation with BW. The results of this study suggest that overall immunocompetence of commercial broilers can be improved by selection for high Ab response of young chicks to controlled immunization with a single antigen, without counteracting further selection for high BW.

Animals↗

Natural infection of broiler breeder chickens with endemic apathogenic Newcastle disease virus and their subsequent response to vaccination with a live V4 Newcastle disease virus vaccine.

Flocks of broiler breeder chickens housed on a commercial farm were monitored from 13 w of age for natural infection with endemic lentogenic Newcastle disease virus (NDV). Seroconversion was first detected at 17 w. By 24 w, all 8 flocks had achieved peak log2 mean haemagglutination inhibiting antibody titres of up to 4.8. Antibody titres then declined and rose again over several months, suggesting cyclic reinfection with NDV. A lentogenic NDV indistinguishable from V4 was isolated from the cloaca of one bird at 18 weeks of age. At 54 weeks of age, 6 of 8 flocks were vaccinated en masse with live V4 NDV vaccine, 3 flocks by drinking water and 3 flocks by aerosol. All flocks were serologically monitored for a further 8 w. Drinking water vaccination induced an anamnestic response in 3 flocks, showing that flocks with pre-existing active immunity to NDV may be successfully vaccinated with V4. However, in all aerosol vaccinated flocks, the procedures failed to induce a response different to that observed in unvaccinated flocks. The serological response to vaccination was greater in sires than in dams.

Animals↗

Fusion of erythrocytes by Newcastle disease virus.

Newcastle disease virus-induced fusion of chick embryo (CE) and chicken erythrocytes has been studied at the ph range between 5.5 and 8.0. The highest degree of fusion of CE erythrocytes was observed at pH 5.5, whereas the chicken erythrocytes fused at pH 5.5-6.0 only. Freezing and thawing of low-haemolytic virus preparation increased its erythrocyte fusion activity. Ammonium chloride did not cause a statistically significant effect on the multiplication of virus preparations expressing different haemolysis and erythrocyte fusion activity.

Animals↗

Transcriptional response of avian cells to infection with Newcastle disease virus.

Newcastle disease virus (NDV) causes widespread disease in poultry and wild-birds throughout the world. cDNA microarray analysis was used to examine the effect of NDV infection on host cell transcription. The results show that NDV infection causes an apparent suppression of the interferon response genes during the early stages of infection. In addition, the results reveal transcriptional silencing of cytoskeletal proteins such as the alpha, beta, and gamma types of actin, and a downregulation of the thioredoxin gene, a likely mediator of apoptosis with possible implications in NDV pathogenesis. Comparative analyses show that a majority of genes that were transcriptionally regulated during infection with another common respiratory pathogen of poultry, the avian pneumovirus, remained unaltered during NDV infection, suggesting that even phylogenetically related viruses elicit unique or "signature" patterns of host transcriptional profiles during infection of host cells.

Actins↗

The role of interferon in interference and auto-interference elicited by Newcastle disease virus.

Newcastle disease virus (NDV) strains interfere in different degree with the growth of the velogenic NDV strain Texas GB (homologous interference) and Sindbis virus (heterologous interference) in chick embryo fibroblast cells. Homologous interference was elicited by interferon-producing live or UV-inactivated strains and non-interferon-producing live or beta-propiolactone-inactivated strains and it was not influenced by actinomycin D. Thus, interferon had apparently no role in homologous interference of NDV. The growth of Sindbis virus was, however, much more inhibited by interferon-producing live or UV-inactivated NDV strains than with non-inducing ones and the interference was reversible by actinomycin D. Thus heterologous interference is apparently mediated by interferon. In chicken cells infected with the mesogenic NDV strain H, virus yields were 50 to 100 times lower at multiplicities of infection above 0.1 p.f.u./cell than below it. The interferon formed during infection played no role in auto-interference, but may well be held responsible for the mild cytopathic effect observed.

Animals↗

The mediator of cellular immunity. XII. Inhibition of activated T cells by Newcastle disease virus.

Newcastle disease virus (NDV) can interact in at least two ways with rat T cells. By adsorbing to circulating lymphocytes, the virus can transiently deflect the cells from lymph nodes and inflammatory exudates induced in the peritoneal cavity. T cells are affected regardless of age, state of activation, or position in the mitotic cycle. The effect is reversible and is mediated not only by infectious (I)-NDV, but also by UV-NDV which cannot achieve a complete replication cycle in eggs. But I-NDV has another lasting effect on activated T cells. It is revealed in the failure of virus-treated thoracic duct lymphocytes to transfer cellular resistance to Listeria monocytogenes, delayed-type hypersensitivity to soluble antigens of the parasite, and the permanent exclusion of labeled S-phase lymphocytes from inflammatory foci. Activated T cells are inhibited by virus multiplicites which have little if any effect upon the proliferative potential of antigen-sensitive T cells or localization of labeled small lymphocytes in lymph nodes. The underlying mechanism has not been determined; however, there are reasons for thinking that NDV has a lethal effect upon activated T cells, because the latter are permissive for virus replication.

Animals↗