Showing papers on "Newcastle disease published in 2003"

Newcastle disease virus (NDV)-based assay demonstrates interferon-antagonist activity for the NDV V protein and the Nipah virus V, W, and C proteins.

Abstract: We have generated a recombinant Newcastle disease virus (NDV) that expresses the green fluorescence protein (GFP) in infected chicken embryo fibroblasts (CEFs). This virus is interferon (IFN) sensitive, and pretreatment of cells with chicken alpha/beta IFN (IFN-α/β) completely blocks viral GFP expression. Prior transfection of plasmid DNA induces an IFN response in CEFs and blocks NDV-GFP replication. However, transfection of known inhibitors of the IFN-α/β system, including the influenza A virus NS1 protein and the Ebola virus VP35 protein, restores NDV-GFP replication. We therefore conclude that the NDV-GFP virus could be used to screen proteins expressed from plasmids for the ability to counteract the host cell IFN response. Using this system, we show that expression of the NDV V protein or the Nipah virus V, W, or C proteins rescues NDV-GFP replication in the face of the transfection-induced IFN response. The V and W proteins of Nipah virus, a highly lethal pathogen in humans, also block activation of an IFN-inducible promoter in primate cells. Interestingly, the amino-terminal region of the Nipah virus V protein, which is identical to the amino terminus of Nipah virus W, is sufficient to exert the IFN-antagonist activity. In contrast, the anti-IFN activity of the NDV V protein appears to be located in the carboxy-terminal region of the protein, a region implicated in the IFN-antagonist activity exhibited by the V proteins of mumps virus and human parainfluenza virus type 2.

Avian influenza and Newcastle disease.

Abstract: Avian influenza (AI) and Newcastle disease (ND) affect various avian species, especially domestic poultry, and are caused by type A orthomyxoviruses and type 1 avian paramyxoviruses, respectively. Clinical manifestations of such infections vary with the virus strain, the host species, and the presence or absence of secondary environmental factors or exacerbating agents. In domestic poultry, infections can be subclinical or induce mild to severe disease syndromes, including respiratory tract disease, decreases in egg production, or a multiorgan systemic disease with a near 100% mortality rate. Severe syndromes are caused by highly virulent specific virus strains termed highly pathogenic AI and velogenic ND viruses. The highly virulent forms of AI and ND are contained on list A of Office International des Epizooties (OIE), the official international organization for animal health and sanitary standards under the World Trade Organization. These highly virulent viruses have severe global impact on poultry health and limit international trade in poultry and poultry products. Furthermore, the viruses that cause highly pathogenic AI and highly virulent ND are potential agribioterrorism agents. However, the milder or low virulent forms of AI and ND are more common and endemic in domestic poultry in many parts of the world, but neither are contained on list A or B of OIE. Cases of human infection by AI and ND viruses have been documented, but are rare.

The impact of a monthly rest day on avian influenza virus isolation rates in retail live poultry markets in Hong Kong

Abstract: Retail live poultry markets (LPMs) may act as a reservoir of avian influenza viruses (AIV). In this study we test the hypothesis that a rest day in the LPMs where the stalls are completely emptied of poultry, cleansed, and restocked will reduce the isolation rates of avian influenza viruses. The isolation rate of H9N2 subtype viruses from chicken was significantly lower after the rest day than prior to it, indicating its impact in reducing transmission. In contrast, Newcastle disease virus (NDV) isolation rates appear unaffected by this intervention, possibly reflecting differences in herd immunity or virus transmission dynamics.

Recombinant Paramyxovirus Type 1-Avian Influenza-H7 Virus as a Vaccine for Protection of Chickens Against Influenza and Newcastle Disease

Abstract: Current vaccines to prevent avian influenza rely upon labor-intensive parenteral injection. A more advantageous vaccine would be capable of administration by mass immunization methods such as spray or water vaccination. A recombinant vaccine (rNDV-AIV-H7) was constructed by using a lentogenic paramyxovirus type 1 vector (Newcastle disease virus [NDV] B1 strain) with insertion of the hemagglutinin (HA) gene from avian influenza virus (AIV) A/chicken/NY/13142-5/94 (H7N2). The recombinant virus had stable insertion and expression of the H7 AIV HA gene as evident by detection of HA expression via immunofluorescence in infected Vero cells. The rNDV-AIV-H7 replicated in 9-10 day embryonating chicken eggs and exhibited hemagglutinating activity from both NDV and AI proteins that was inhibited by antisera against both NDV and AIV H7. Groups of 2-week-old white Leghorn chickens were vaccinated with transfectant NDV vector (tNDV), rNDV-AIV-H7, or sterile allantoic fluid and were challenged 2 weeks later with viscerotropic velogenic NDV (vvNDV) or highly pathogenic (HP) AIV. The sham-vaccinated birds were not protected from vvNDV or HP AIV challenge. The transfectant NDV vaccine provided 70% protection for NDV challenge but did not protect against AIV challenge. The rNDV-AIV-H7 vaccine provided partial protection (40%) from vvNDV and HP AIV challenge. The serologic response was examined in chickens that received one or two immunizations of the rNDV-AIV-H7 vaccine. Based on hemagglutination inhibition and enzyme-linked immunosorbent assay (ELISA) tests, chickens that received a vaccine boost seroconverted to AIV H7, but the serologic response was weak in birds that received only one vaccination. This demonstrates the potential for NDV for use as a vaccine vector in expressing AIV proteins.

Review of Newcastle disease virus with particular references to immunity and vaccination.

Abstract: Newcastle disease (ND) is a highly contagious disease. The present paper deals with classification of ND virus (NDV), clinical signs and pathology, virus strain classification and molecular backgro...

Virulence of six heterogeneous-origin Newcastle disease virus isolates before and after sequential passages in domestic chickens.

Abstract: Four serial passages of six Newcastle disease virus (NDV) isolates were performed in two-week-old White Leghorns. The viruses were recovered from chickens (Ckn-Live Bird Market and Ckn-Australia isolates), exotic (Yellow Nape [YN] Parrot, Pheasant, and Dove isolates) and wild birds (Anhinga isolate). Infected chickens were monitored clinically and humanely killed to sample tissues for histopathology and immunohistochemistry. Pathogenicity tests, to assess the virulence of the isolates for chickens, and sequence analysis of the fusion protein cleavage site were performed before and after passages. The moderately virulent Dove isolate became highly virulent with serial passage. The originally highly virulent Pheasant isolate had an increase in the intracerebral pathogenicity index (ICPI) and the intravenous pathogenicity index (IVPI) with passages in chickens. Virulence increase was not observed with Ckn-LBM, YN Parrot, Ckn-Australia, or Anhinga isolates after four chicken passages. The results demonstrate ...

The Effect of Dietary Lysine Deficiency on the Immune Response to Newcastle Disease Vaccination in Chickens

Abstract: SUMMARY. The effect of lysine deficiency on chicken immune function was evaluated using broiler chickens fed a diet with lysine at 67% of the control diet (1.24% lysine). The evaluation of humoral immune function was conducted by measuring the antibody production to a live Newcastle disease virus (NDV) vaccination using the hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA). The cellular immune function was evaluated through the use of cutaneous basophil hypersensitivity test. The antibody response to NDV vaccination was reduced in broiler chickens fed a lysine-deficient diet when measured by ELISA but not when measured by HI. The cell-mediated immune response was also reduced by lysine deficiency.

Pathogenesis of Chicken-Passaged Newcastle Disease Viruses Isolated from Chickens and Wild and Exotic Birds

Abstract: SUMMARY. The pathogenesis of six Newcastle disease virus (NDV) isolates recovered from chickens (Ckn-LBM and Ckn-Australia) and wild (Anhinga) and exotic (YN parrot, pheasant, and dove) birds was examined after the isolates had been passaged four times in domestic chickens. Groups of 10 4-wk-old specific-pathogen-free white leghorn chickens were inoculated intraconjunctivally with each one of the isolates. The infected birds were observed for clinical disease and were euthanatized and sampled at selected times from 12 hr to 14 days postinoculation or at death. Tissues were examined by histopathology, by immunohistochemistry (IHC) to detect viral nucleoprotein (IHC/NP), and by in situ hybridization to detect viral mRNA and were double labeled for apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling ([TUNEL] or IHC/caspase-3) and viral nucleoprotein (IHC/NP). Birds infected with the three low virulence viruses (Ckn-LBM, YN parrot, and Ckn-Australia) did not develop clinical disease. Microscopic lesions were observed only at the inoculation site and in organs of the respiratory system. The detection of viral nucleoprotein (N) was restricted to the inoculation site. The pheasant and dove isolates were highly virulent for chickens with marked tropism for lymphoid tissues, confirmed by the presence of large numbers of cells positive for viral N protein and viral mRNA. Viral N protein was detected early in the cytoplasm of cells in the center of the splenic ellipsoids. The apoptosis assays (TUNEL and IHC/caspase-3) showed increased apoptosis in the splenic ellipsoids as well. Apparently, apoptosis is an important mechanism in lymphoid depletion during NDV infection.

Investigations on the influence of helminth parasites on vaccination of chickens against Newcastle disease virus under village conditions.

Abstract: Prevalence studies have shown that almost 100% of free-range chickens are infected with a wide range of parasites. The infections are mostly subclinical in nature, resulting in production losses and occasionally mortality. Newcastle disease (ND), on the other hand, results in high mortality rates during epidemics. ND is a limiting factor for increasing poultry production in many tropical countries, where frequent reports indicate vaccination failures. The aim of our study was to investigate the influence of helminths on the antibody response after vaccination against Newcastle disease of free-range chickens naturally infected with parasites. Sixty chickens were divided into six groups, of which three were vaccinated against ND with a live De Soto vaccine, while the other three remained non-vaccinated. One group within the vaccinated groups and the one within the non-vaccinated group was kept naturally infected with helminth parasites, while the other two groups in each set were dewormed with fenbendazole and niclosamide, and one of each of these groups was subsequently infected with Ascaridia galli. After vaccination, all the groups were followed for 5 weeks and their antibody titres were determined weekly using a HI test. All the birds were finally challenged 4 weeks after vaccination with a virulent velogenic ND virus obtained from a field outbreak. All the vaccinated chickens seroconverted and had high antibody levels after 3 weeks, but these dropped to low levels at 4 weeks after vaccination. After challenge, the antibody titres rose in the dewormed groups but not in the parasite-infected groups. After 5 weeks, all the parasite-infected animals had significantly lower antibody titres than the dewormed animals. All the vaccinated chickens survived the challenge infection, emphasizing the importance of the cellular immune response. Further studies are needed to examine the effects of the parasitic infection on protection against ND over a longer period.

On the origins and relationships of Newcastle disease virus vaccine strains Hertfordshire and Mukteswar, and virulent strain Herts'33.

Abstract: The origins and relationships of Newcastle disease virus (NDV) vaccine strains Hertfordshire (H) and Mukteswar, and the virulent Herts'33 were studied using partial sequence analysis of the fusion protein gene. The mesogenic strain H was obtained by egg passages of a field virus isolated in England in 1933 (later known as Herts'33). Different lines of the strain Herts'33, however, divided into two distinct groups: genotype IV, and a hitherto undescribed lineage, which comprised the Weybridge line (Herts'33/56). Vaccine strain H and the two clusters comprising viruses designated Herts'33 displayed 6.5 to 6.8% and 15.6 to 16.3% mutational distances, respectively, which precluded parent-offspring relationships with either of them. In contrast, the different lines of the vaccine strain Mukteswar, which was reportedly derived from an Indian field isolate in the mid-1940s, showed 98.9 to 100% sequence similarity to strain H. It is therefore probable that the two vaccines were derived from the same virus stock.

Immunoglobulin class distribution of systemic and mucosal antibody responses to Newcastle disease in chickens.

Abstract: SUMMARY. In serum, tracheal wash fluid, and bile from chickens that were inoculated with live or inactivated Newcastle disease virus (NDV), the kinetics and immunoglobulin (Ig) class distribution of an antibody response were demonstrated. The Ig classes (IgM, IgG, and IgA) were captured using monoclonal antibodies (MAbs) in enzyme-linked immunosorbent assays (Ig-capture ELISA). The antibody specificity of the captured Ig was confirmed by binding of NDV. After inoculation with live virus, antibodies of the IgG and IgM classes were mainly found in serum. IgM was produced early from day 4 postexposure (PE) onward, IgG was detected later from day 7 PE onward, and in the tracheal wash fluid and bile, all three Ig classes were demonstrated. After inoculation of inactivated virus, a delayed response of all three classes was observed in serum, and only IgM and IgG were recognized in the tracheal fluid and bile. The type of vaccine and the route of antigen entrance may have determined the immunoglobulin class produced. The Ig-capture ELISA assay developed in this study can be useful for evaluating various strategies to improve the efficacy of Newcastle disease vaccines and to study the evoked immune mechanisms.

Occurrence of genotypes IV, V, VI and VIIa in Newcastle disease outbreaks in Germany between 1939 and 1995.

Abstract: Forty-five velogenic Newcastle disease virus strains isolated in Germany between 1939 and 1995 were analysed by restriction enzyme digestion and sequencing to shed light on the relationships of past epizootics. Viruses derived from the period prior to 1970 belonged to a clade ( IVea) of genotype IV comprising the earliest isolates from Europe, and could be isolated until the late seventies from poultry. Essex' 70-like viruses, the prototype of genotype V, were already present at the beginning of the 1970-74 epizootic and in sporadic cases thereafter, indicating that these Newcastle disease outbreaks started in Western Europe. A genotype VI ( subtype VIc) isolate was obtained in the early 1980s from a single outbreak in poultry. Outbreaks between 1993-95 were again part of a Western European epizootic caused by a genotype VIIa virus that was prevalent in the Far East

Development of a virosome vaccine for Newcastle disease virus.

Abstract: In an effort to protect chickens against Newcastle disease (ND), a nonreplicating virosome vaccine was produced by solubilization of Newcastle disease virus (NDV) with Triton X-100 followed by detergent removal with SM2 Bio-Beads. Biochemical analysis indicated that the NDV virosomes had similar characteristics as the parent virus and contained both the fusion and hemagglutinin-neuraminidase proteins. To target the respiratory tract, specific-pathogen-free chickens were immunized intranasally and intratracheally with the NDV virosome vaccine. This vaccine was compared with a standard NDV (LaSota) live-virus vaccine for commercial poultry. Seroconversion (≥ four fold increase in hemagglutination inhibition [HI] antibody titers) was achieved in all birds vaccinated with the virosome vaccine. Upon lethal challenge with a velogenic NDV strain (Texas GB), all birds receiving either vaccination method were protected against death. Antibody levels against NDV, as determined by enzyme-linked immunosorben...

The effects of avian leukosis virus subgroup J on broiler chicken performance and response to vaccination.

Abstract: The effects of avian leukosis virus subgroup J (ALV-J) infection on meat-type chickens reared in a simulated commercial setting were evaluated. Each of three ALV-J isolates was evaluated with both simulated horizontal transmission (SHT) and simulated vertical transmission (SVT). Mortality, morbidity, disease condemnations, and feed conversions were increased and body weights at processing were decreased in ALV-J infected birds as compared to sham inoculated hatch mates. The adverse effects of ALV-J infection were more severe in birds exposed by SVT than in birds exposed by SHT. At 8 weeks of age response to vaccination for infectious bronchitis virus and Newcastle disease virus or prior exposure to a pathogenic reovirus was assessed in the ALV-J and sham inoculated broiler chickens by challenge studies. Although not statistically significant, an overall trend of decreased protection to challenge after vaccination, or prior exposure, was observed in the ALV-J inoculates as compared to sham inocula...

The Impact of a Monthly Rest Day on Avian Tnfluenza Virus Isolation Rates in Retail Live Poultry Markets in Hong Kong N. Y. Kung,AB Y. Guan, N. R. Perkins, L. Bissett,C T. Ellis,C L. Sims,C

Abstract: viruses (AIV). In this study we test the hypothesis that a rest day in the LPMs where the stalls are completely emptied of poultry, cleansed, and restocked will reduce the isolation rates of avian influenza viruses. The isolation rate of H9N2 subtype viruses from chicken was significantly lower after the rest day than prior to it, indicating its impact in reducing transmission. In contrast, Newcastle disease virus (NDV) isolation rates appear unaffected by this intervention, possibly reflecting differences in herd immunity or virus transmission dynamics.

Evaluation of Three Different Vaccination Regimes Against Newcastle Disease in Central Anatolia

Abstract: A change in the vaccination strategy used in the Central Anatolia region of Turkey to combat the effects of infections with endemic virulent Newcastle disease virus (NDV) in maternally immune birds is described in this retrospective work. A novel vaccination schedule was applied to approximately 2,230,000 chickens from different breeds. The alterations were based on the use of an inactivated NDV + infectious bursal disease virus (IBDV) and the application of aerosol vaccines with different timings compared to traditional programmes. In a district in which Newcastle disease (ND) epidemics had been occurring, a satisfactory humoral protection (mHI titre >log 27) was achieved in birds up to 9-11 weeks of age by the early administration of inactivated NDV + IBDV vaccine. It is suggested that inactivated NDV + IBDV vaccination at 1 week of age be recommended as an alternative procedure to prevent both ND and infectious bursal disease (IBD), although the data presented here on immunity to IBD was essentially restricted to clinical observations.

Haemagglutinating activity of the lentogenic Newcastle disease virus strain MET95.

Abstract: Using the rapid glass plate method, the Newcastle disease virus strain MET95 showed much weaker haemagglutination (HA) activity for chicken erythrocytes than 69 other Newcastle disease viruses, including 56 field strains isolated from chickens reared in Japan between 1988 and 2001. Using erythrocytes from other avian species, only the MET95 strain failed to show HA activity for erythrocytes from ducks, geese or pigeons. The haemagglutinin-neuraminidase protein of the MET95 strain was shown to have unique substitutions of isoleucine for thereonine and leucine at amino acide residues 216 and 552. It is suggested that these two substitutions might relate to the unique HA activity of the MET95 strain. This HA activity may be a useful marker for this strain.

Efficacy of two commercial Newcastle disease virus lentogenic vaccines against virulent asiatic-type Newcastle disease viruses

Abstract: Seventy-five unvaccinated chickens were divided into three equal groups. Chickens in group A received RDVF [Lentogenic strain of Newcastle disease virus (NDV)] vaccine oculonasally at 7 d of age and through drinking water at 4 wk of age. Chickens in group B were vaccinated with LaSota (Lentogenic strain of NDV) in the same way. Group C birds were kept as unvaccinated challenge controls. Five birds from each of these groups were moved to separate pens at 7 wk of age and were challenged with a field isolate No. 105 of virulent NDV (C1, based on monoclonal antibody grouping or Asiatic type, which was isolated from a disease outbreak). Similarly, five birds from each of the groups were moved to different pens at same age and challenged with the reference strain of the virulent NDV. All the unvaccinated birds died postchallenge, but both vaccinated groups withstood the challenge. Serum samples were collected from all three groups at different times, and antibody levels (against NDV) were measured by hemagglutination inhibition test, passive hemagglutination test, and enzyme-linked immunosorbent assay. The possibility of Asiatic-type NDV causing outbreaks in commercially vaccinated flocks is discussed in this paper.

Short Communication Newcastle disease virus nucleocapsid protein: self-assembly and length-determination domains

Abstract: The nucleocapsid protein (NP) of Newcastle disease virus expressed in E. coli assembled as ring- and herringbone-like particles. In order to identify the contiguous NP sequence essential for assembly of these particles, 11 N- or C-terminally deleted NP mutants were constructed and their ability to self-assemble was tested. The results indicate that a large part of the NP N-terminal end, encompassing amino acids 1 to 375, is required for proper folding to form a herringbone-like structure. In contrast, the C-terminal end covering amino acids 376 to 489 was dispensable for the formation of herringbone-like particles. A region located between amino acids 375 to 439 may play a role in regulating the length of the herringbone-like particles. Mutants with amino acid deletions further from the C-terminal end (84, 98, 109 and 114 amino acids) tended to form longer particles compared to mutants with shorter deletions (25 and 49 amino acids).

Immunosuppression Caused by Avian Leucosis Virus of Subgroup J and its Coinfection With ReticuloEndotheliosis Virus in Broilers

Abstract: When 1 day old broilers were infected with avian leukosis virus of subgroup J(ALV J) strain NX0101,the body weight was significantly reduced,atrophy of the bursa and thymus was detected,and antibody reaction to Newcastle disease virus vaccine was inhibited,while compared to the control birds(P0 05).Such phenomena were even more serious when birds were co infected with ALV J strain NX0101 and reticuloendotheliosis virus(REV) strain SD9901 as compared to controls(P0 01) or to birds infected with ALV J alone(P0 05).ALV J infection alone gave no influence on reaction to IBDV vaccination in birds,but co infection of ALV J and REV apparently delayed antibody reactions to IBDV.This is the first report to demonstrate the immunosuppression of ALV J infection on broilers especially when co infcted with REV.

Thermostable I-2 strain of Newcastle disease virus as a rural vaccine

Abstract: The potential contribution of scavenging chicken flocks to village populations in developing countries is being reassessed partly as the result of the development in Australia of new Newcastle disease vaccines for village use. These vaccines, based on avirulent thermostable Australian strains of Newcastle disease virus (NDV) (initially strain V4 and more recently strain I-2), can be produced locally and are not entirely reliant on a cold chain. They are finding use in many developing countries. The present study deals with some practical aspects of the production and use of I-2 vaccine in developing countries. It also addresses some fundamental aspects of I-2 virus and contributes to the international database on comparative virology. The assay of avirulent strains of NDV has relied on the use of embryonated eggs, as these viruses are poorly cytopathogenic in cultured avian cells. Embryonated eggs are unsuited for repetitive assays, being both time-consuming and expensive. I-2 virus was shown to produce cyctopathic changes in chicken embryo kidney cells grown in microtitre trays. End points could be determined laboriously by careful microscopic examination or readily by gross examination of fixed and stained cultures. Cell culture was less sensitive than egg inoculation in determining viral infectivity, but endpoints obtained by both methods were highly correlated. Cell culture was used later in this study when repeated titrations of the infectivity of I-2 virus were required. Although I-2 virus is relatively thermostable, I-2 vaccines must still be kept as cool as possible. Diluents that protect against thermal inactivation could extend shelf life when storage at ambient temperatures was required. I-2 virus was suspended in several diluents that are used to protect viruses during lyophilization. Inactivation rates were established on storage at 22-25°C. The diluents that gave the best protection were 5% lactalbumin, 5% skim milk, 1% gelatin, 1% polyvinyl pyrrolidone (PVP) and a complex mixture (SPGAE) of sucrose, phosphates, glutamic acid, bovine serum albumin and EDTA. In some circumstances, I-2 vaccine will be produced in liquid form in provincial laboratories and used within a fortnight. There will be no time for conventional quality assurance tests. It would be advantageous to develop a method for rapid estimation of potency that does not involve titration in eggs, a process requiring at least 4 days. Embryonated eggs were inoculated with varying doses of I-2 virus, and the intervals until progeny virus could be detected by a haemagglutination test were determined. A standard chicken dose of I-2 vaccine (106 50% embryo infectious doses) yielded detectable haemagglutinin 11 hours after inoculation. This simple overnight assay may suffice to indicate the potency of a newly harvested vaccine. Although I-2 vaccine is usually administered by eye drop in the field, many administrators would prefer a food-based vaccine. White (polished) rice is an obvious choice, being readily available in many countries, and acceptable to chickens. However raw white rice rapidly destroys the vaccine virus that is applied to it. Boiling the rice results in an excellent vehicle for the vaccine, but one that is rapidly subject to bacterial spoilage. Raw white rice was mixed with vegetable oil and then coated with I-2 vaccine and stored at 22-25°C. Recovery of vaccine virus from oiled rice was only slightly less than recovery from boiled rice after 0.5 or 24 hours. Oiled rice may be a suitable vehicle for a food-based I-2 vaccine. Unselected strain I-2 virus possessed a degree of thermostability which was enhanced by heat selection when the I-2 master seed was produced. At present the production of I-2 vaccine involves two passages in eggs (to working seed and to vaccine) without further heat selection. Thermostability is retained. Vaccine production could be increased if further passages could be interposed between master seed and vaccine without loss of thermostability. I-2 vaccine was serially passaged 20 times in embryonated eggs and thermostability of infectivity at 56 °C was determined after each 5 passages. Thermostability was virtually unaltered after 5 passages, rate constants (k x 10-3/minutes-1) being 3.6 at passage 1 and 3.3 at passage 5. Thermostability declined with further passage. Haemagglutinating activity declined less rapidly. V4, an avirulent, enteric strain of NDV was isolated in 1966. Strain I-2 was isolated in the early 1990s and was a representative of viruses that were believed to be evolving tropism for the respiratory tract. Later isolates of NDV in Australia included a pathogenic strain, and a progenitor that formed a link between the pathogenic and the apathogenic isolates. It was important to define the biological and molecular characteristics of strain 1-2 to differentiate it from these other viruses. A reverse transcription polymerase chain reaction (RT-PCR) was developed that allowed strains V4 and I-2 to be detected in chicken tissues, and that could distinguish between these viruses. Chickens were vaccinated with either strain I-2 or strain V4 and various tissues were sampled for virus over the next 7 days. Both viruses were detected in samples from both the respiratory and digestive tracts. Strain I-2 was detected earlier than V4 in the respiratory tract and persisted for longer. Strain V4 was detected earlier than strain I-2 in the digestive tract, and persisted for longer. It was concluded that the two viruses exhibited different tissue tropisms. Amino acid sequences, deduced from nucleotide sequences, are now widely used as indicators of the pathotype of strains of NDV and in tracing the evolutionary history of isolates. The cleavage site of the fusion protein and the carboxyl terminus of the haemagglutinin-neuraminidase protein have been useful sites. Molecular studies had not previously been undertaken with strain I-2. Single tube RT-PCR techniques were developed for use with I-2 virus, the amplicons were sequenced and the amino acid sequences deduced. The cleavage activation site of I-2 was 112RKQGR116 differing only in the substitution of R for G at residue 112 from the motif of V4 and other avirulent strains of NDV. At the N terminus of the F1 protein, I-2 shared with V4 and other avirulent strains the motif 117LIG119 and not the 117FIG119 motif of virulent strains. At the carboxyl terminus of the haemagglutinin-neuraminidase protein, strain I-2 had a 7 amino acid extension. This indicates a different lineage from V4 and similar avirulent strains (45 amino acid extensions) and Australian virulent strains and their apparent precursors (9 amino acid extensions).

Production of hyperimmune serum against newcastle disease virus (NDV) in rabbits

Abstract: The quick diagnosis of Newcastle disease requires known serum against the disease. In this study, an attempt was made to raise anti- Newcastle disease virus hyperimmune serum in rabbits. Three different inoculum were prepared to inoculate in the rabbits; (i) Fresh harvested allantoic fluid containing Newcastle disease virus (NDV) Mukteswar vaccine strain; (ii) Freshly harvested ND virus pelletted through centrifuging at 40,000 rpm for two hours and resuspended in normal saline and (iii) Pelletted virus (centrifuged and suspended as in ii) with addition of incomplete Freund's adjuvant. It was observed during the monitoring of haemagglutination inhibition (HI) titre that the serum collected after series of inoculation of 1st and 2nd inoculum provided maximum titre upto 1:256. However, the serum collected after series of injection of 3rd inoculum gave maximum HI titre 1:1024. This study suggested that antigen containing incomplete Freund's adjuvant provided better immune response against Newcastle disease virus in rabbits.