Displaying publications 1 - 20 of 97 in total

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  1. van Doremalen N, Lambe T, Sebastian S, Bushmaker T, Fischer R, Feldmann F, et al.
    PLoS Negl Trop Dis, 2019 06;13(6):e0007462.
    PMID: 31170144 DOI: 10.1371/journal.pntd.0007462
    Nipah virus (NiV) is a highly pathogenic re-emerging virus that causes outbreaks in South East Asia. Currently, no approved and licensed vaccine or antivirals exist. Here, we investigated the efficacy of ChAdOx1 NiVB, a simian adenovirus-based vaccine encoding NiV glycoprotein (G) Bangladesh, in Syrian hamsters. Prime-only as well as prime-boost vaccination resulted in uniform protection against a lethal challenge with NiV Bangladesh: all animals survived challenge and we were unable to find infectious virus either in oral swabs, lung or brain tissue. Furthermore, no pathological lung damage was observed. A single-dose of ChAdOx1 NiVB also prevented disease and lethality from heterologous challenge with NiV Malaysia. While we were unable to detect infectious virus in swabs or tissue of animals challenged with the heterologous strain, a very limited amount of viral RNA could be found in lung tissue by in situ hybridization. A single dose of ChAdOx1 NiVB also provided partial protection against Hendra virus and passive transfer of antibodies elicited by ChAdOx1 NiVB vaccination partially protected Syrian hamsters against NiV Bangladesh. From these data, we conclude that ChAdOx1 NiVB is a suitable candidate for further NiV vaccine pre-clinical development.
    Matched MeSH terms: Viral Vaccines/administration & dosage; Viral Vaccines/genetics; Viral Vaccines/immunology*
  2. Zulkifli I, Abdulllah N, Azrin NM, Ho YW
    Br Poult Sci, 2000 Dec;41(5):593-7.
    PMID: 11201439
    1. Hubbard x Hubbard (HH) and Shaver x Shaver (SS) chicks given a dietary supplement of either 50 mg/kg oxytetracycline (OTC) or 1 g/kg Lactobacillus culture (LC) were exposed to 36 +/- 1 degrees C for 3 h daily from day (d) 21 to 42. 2. Prior to heat treatment, body weight (d 21) and weight gain (d 1 to d 21) of OTC and LC birds were greater than those fed the control diet. Chicks given LC had the best food efficiency followed by OTC and control birds during d 1 to d 21. Body weight (d 1 and d 21) and weight gain (d 1 to d 21) were greater for HH tlhan SS chicks. 3. After 3 weeks of heat exposure, birds receiving the LC diet had greater body weight and weight gain, higher food intake and lower food efficiency than OTC and control chicks. 4. Antibody production against Newcastle discase vaccine on d 21 was not affected by strain or diet. On d 42, while diet had negligible effect on this variable among the SS broilers, HH birds fed LC had higher antibody production than those on the control diet. 5. Neither strain nor diet had a significant effect on mortality.
    Matched MeSH terms: Viral Vaccines/immunology
  3. Yusuf M, Konc J, Sy Bing C, Trykowska Konc J, Ahmad Khairudin NB, Janezic D, et al.
    J Chem Inf Model, 2013 Sep 23;53(9):2423-36.
    PMID: 23980878 DOI: 10.1021/ci400421e
    ProBiS is a new method to identify the binding site of protein through local structural alignment against the nonredundant Protein Data Bank (PDB), which may result in unique findings compared to the energy-based, geometry-based, and sequence-based predictors. In this work, binding sites of Hemagglutinin (HA), which is an important target for drugs and vaccines in influenza treatment, have been revisited by ProBiS. For the first time, the identification of conserved binding sites by local structural alignment across all subtypes and strains of HA available in PDB is presented. ProBiS finds three distinctive conserved sites on HA's structure (named Site 1, Site 2, and Site 3). Compared to other predictors, ProBiS is the only one that accurately defines the receptor binding site (Site 1). Apart from that, Site 2, which is located slightly above the TBHQ binding site, is proposed as a potential novel conserved target for membrane fusion inhibitor. Lastly, Site 3, located around Helix A at the stem domain and recently targeted by cross-reactive antibodies, is predicted to be conserved in the latest H7N9 China 2013 strain as well. The further exploration of these three sites provides valuable insight in optimizing the influenza drug and vaccine development.
    Matched MeSH terms: Viral Vaccines*
  4. Yong CY, Liew WPP, Ong HK, Poh CL
    Biotechnol Prog, 2022 Nov;38(6):e3292.
    PMID: 35932092 DOI: 10.1002/btpr.3292
    Severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are the most impactful coronaviruses in human history, especially the latter, which brings revolutionary changes to human vaccinology. Due to its high infectivity, the virus spreads rapidly throughout the world and was declared a pandemic in March 2020. A vaccine would normally take more than 10 years to be developed. As such, there is no vaccine available for SARS-CoV and MERS-CoV. Currently, 10 vaccines have been approved for emergency use by World Health Organization (WHO) against SARS-CoV-2. Virus-like particle (VLP)s are nanoparticles resembling the native virus but devoid of the viral genome. Due to their self-adjuvanting properties, VLPs have been explored extensively for vaccine development. However, none of the approved vaccines against SARS-CoV-2 was based on VLP and only 4% of the vaccine candidates in clinical trials were based on VLPs. In the current review, we focused on discussing the major advances in the development of VLP-based vaccine candidates against the SARS-CoV, MERS-CoV, and SARS-CoV-2, including those in clinical and pre-clinical studies, to give a comprehensive overview of the VLP-based vaccines against the coronaviruses.
    Matched MeSH terms: Viral Vaccines*
  5. Yoneda M
    Uirusu, 2014;64(1):105-12.
    PMID: 25765986 DOI: 10.2222/jsv.64.105
    Nipah virus (NiV), a paramyxovirus, was first discovered in Malaysia in 1998 in an outbreak of infection in pigs and humans, and incurred a high fatality rate in humans. We established a system that enabled the rescue of replicating NiVs from a cloned DNA. Using the system, we analyzed the functions of accessory proteins in infected cells and the implications in in vivo pathogenicity. Further, we have developed a recombinant measles virus (rMV) vaccine expressing NiV envelope glycoproteins, which appeared to be an appropriate to NiV vaccine candidate for use in humans.
    Matched MeSH terms: Viral Vaccines*
  6. Yoneda M, Georges-Courbot MC, Ikeda F, Ishii M, Nagata N, Jacquot F, et al.
    PLoS One, 2013;8(3):e58414.
    PMID: 23516477 DOI: 10.1371/journal.pone.0058414
    Nipah virus (NiV) is a member of the genus Henipavirus, which emerged in Malaysia in 1998. In pigs, infection resulted in a predominantly non-lethal respiratory disease; however, infection in humans resulted in over 100 deaths. Nipah virus has continued to re-emerge in Bangladesh and India, and person-to-person transmission appeared in the outbreak. Although a number of NiV vaccine studies have been reported, there are currently no vaccines or treatments licensed for human use. In this study, we have developed a recombinant measles virus (rMV) vaccine expressing NiV envelope glycoproteins (rMV-HL-G and rMV-Ed-G). Vaccinated hamsters were completely protected against NiV challenge, while the mortality of unvaccinated control hamsters was 90%. We trialed our vaccine in a non-human primate model, African green monkeys. Upon intraperitoneal infection with NiV, monkeys showed several clinical signs of disease including severe depression, reduced ability to move and decreased food ingestion and died at 7 days post infection (dpi). Intranasal and oral inoculation induced similar clinical illness in monkeys, evident around 9 dpi, and resulted in a moribund stage around 14 dpi. Two monkeys immunized subcutaneously with rMV-Ed-G showed no clinical illness prior to euthanasia after challenge with NiV. Viral RNA was not detected in any organ samples collected from vaccinated monkeys, and no pathological changes were found upon histopathological examination. From our findings, we propose that rMV-NiV-G is an appropriate NiV vaccine candidate for use in humans.
    Matched MeSH terms: Viral Vaccines/immunology*
  7. Yoneda M
    Nippon Rinsho, 2016 12;74(12):1973-1978.
    PMID: 30550652
    Nipah and Hendra virus were first identified in mid 1990s in Australia and Malaysia, caus- ing epidemics with high mortality rate in affected animals and humans. Since their first emer- gence, they continued to re-emerge in Australia and South East Asia almost every year. Nipah and Hendra virus were classified in the new genus Henipavirus because of their un- common features amongst Paramyxoviridae. Henipaviruses are zoonotic paramyxoviruses with a broad tropism, and cause severe acute respiratory disease and encephalitis. Their high virulence and wide host range make them to be given Biosecurity Level 4 status. This review summarizes details of Henipavirus emergence, reservoir hosts and pathology, and introduce recent progress in vaccines and antivirals.
    Matched MeSH terms: Viral Vaccines/therapeutic use
  8. Yee PTI, Laa Poh C
    Virology, 2017 06;506:121-129.
    PMID: 28384566 DOI: 10.1016/j.virol.2017.03.017
    Enterovirus-A71 (EV-A71) is an etiological agent of the hand, foot and mouth disease (HFMD). EV-A71 infection produces high fever and ulcers in children. Some EV-A71 strains produce severe infections leading to pulmonary edema and death. Although the protective efficacy of the inactivated vaccine (IV) was ≥90% against mild HFMD, there was approximately 80% protection against severe HFMD. The monovalent EV-A71 IV elicits humoral immunity but lacks long-term immunogenicity. Spontaneous mutations of the EV-A71 genome could lead to antigenicity changes and the virus may not be neutralized by antibodies elicited by the IV. A better alternative would be the live attenuated vaccine (LAV) that elicits cellular and humoral immunity. The LAV induces excellent antigenicity and chances of reversion is reduced by presence of multiple mutations which could reduce pathogenicity. Besides CV-A16, outbreaks have been caused by CV-A6 and CV-A10, hence the development of bivalent and trivalent vaccines is required.
    Matched MeSH terms: Viral Vaccines/administration & dosage; Viral Vaccines/genetics; Viral Vaccines/immunology*
  9. Yee PTI, Tan SH, Ong KC, Tan KO, Wong KT, Hassan SS, et al.
    Sci Rep, 2019 03 18;9(1):4805.
    PMID: 30886246 DOI: 10.1038/s41598-019-41285-z
    Besides causing mild hand, foot and mouth infections, Enterovirus A71 (EV-A71) is associated with neurological complications and fatality. With concerns about rising EV-A71 virulence, there is an urgency for more effective vaccines. The live attenuated vaccine (LAV) is a more valuable vaccine as it can elicit both humoral and cellular immune responses. A miRNA-based vaccine strain (pIY) carrying let-7a and miR-124a target genes in the EV-A71 genome which has a partial deletion in the 5'NTR (∆11 bp) and G64R mutation (3Dp°l) was designed. The viral RNA copy number and viral titers of the pIY strain were significantly lower in SHSY-5Y cells that expressed both let-7a and miR-124a. Inhibition of the cognate miRNAs expressed in RD and SHSY-5Y cells demonstrated de-repression of viral mRNA translation. A previously constructed multiply mutated strain, MMS and the pIY vaccine strain were assessed in their ability to protect 4-week old mice from hind limb paralysis. The MMS showed higher amounts of IFN-γ ex vivo than the pIY vaccine strain. There was absence of EV-A71 antigen in the skeletal muscles and spinal cord micrographs of mice vaccinated with the MMS and pIY strains. The MMS and pIY strains are promising LAV candidates developed against severe EV-A71 infections.
    Matched MeSH terms: Viral Vaccines/administration & dosage*; Viral Vaccines/genetics; Viral Vaccines/immunology
  10. Yee PT, Poh CL
    Viruses, 2015 Dec 30;8(1).
    PMID: 26729152 DOI: 10.3390/v8010001
    The hand, foot and mouth disease is caused by a group of Enteroviruses such as Enterovirus 71 (EV-A71) and Coxsackievirus CV-A5, CV-A8, and CV-A16. Mild symptoms of EV-A71 infection in children range from high fever, vomiting, rashes and ulcers in mouth but can produce more severe symptoms such as brainstem and cerebellar encephalitis, leading up to cardiopulmonary failure and death. The lack of vaccines and antiviral drugs against EV-A71 highlights the urgency of developing preventive and treatment agents against EV-A71 to prevent further fatalities. Research groups have developed experimental inactivated vaccines, recombinant Viral Protein 1 (VP1) vaccine and virus-like particles (VLPs). The inactivated EV-A71 vaccine is considered the safest viral vaccine, as there will be no reversion to the infectious wild type strain. The recombinant VP1 vaccine is a cost-effective immunogen, while VLPs contain an arrangement of epitopes that can elicit neutralizing antibodies against the virus. As each type of vaccine has its advantages and disadvantages, increased studies are required in the development of such vaccines, whereby high efficacy, long-lasting immunity, minimal risk to those vaccinated, safe and easy production, low cost, dispensing the need for refrigeration and convenient delivery are the major goals in their design.
    Matched MeSH terms: Viral Vaccines/genetics; Viral Vaccines/immunology*
  11. Yee PT, Poh CL
    Curr Pharm Des, 2016;22(44):6694-6700.
    PMID: 27510488 DOI: 10.2174/1381612822666160720165613
    The Hand, Foot and Mouth Disease (HFMD) is caused by Enterovirus 71 (EV-A71) and Coxsackieviruses. Common HFMD symptoms are high fever (≥ 39°C), rashes, and ulcers but complications due to virulent EV-A71 may arise leading to cardiopulmonary failure and death. The lack of vaccines and antiviral drugs against EV-A71 highlights the urgency of developing preventive and treatment agents. Recent studies have reported the emergence of novel antiviral agents and vaccines that utilize microRNAs (miRNAs). They belong to a class of small (19-24 nt) non coding RNA molecules. As miRNAs play a major role in the host regulatory system, there is a huge opportunity for interplay between host miRNAs and EV-A71 expressions. A total of 42 out of 64 miRNAs were up-regulated in EV-A71-infected cells. There was consistent up-regulation of miR-1246 gene expression that targeted the DLG3 gene which contributes to neurological pathogenesis. In contrast, miR-30a that targets calcium channels for membrane transportation was down-regulated. This leads to repression of EV-A71 replication. The impact of host miRNAs on immune activation, shutdown of host protein synthesis, apoptosis, signal transduction and viral replication are discussed. miRNAs have been used in the construction of live attenuated vaccines (LAV) such as the poliovirus LAV that has miRNA binding sites for let-7a or miR-124a. The miRNAbearing vaccine will not replicate in neuronal cells carrying the corresponding miRNA but could still replicate in the gastrointestinal tract and hence remains to act as immunogens. As such, miRNAs are attractive candidates to be developed as vaccines and antivirals.
    Matched MeSH terms: Viral Vaccines/immunology; Viral Vaccines/therapeutic use; Viral Vaccines/chemistry*
  12. Yasmin AR, Yeap SK, Hair-Bejo M, Omar AR
    Avian Dis, 2016 12;60(4):739-751.
    PMID: 27902915
    Studies have shown that infectious bursal disease virus (IBDV) infects lymphoid cells, mainly B cells and macrophages. This study was aimed to examine the involvement of chicken splenic-derived dendritic cells (ch-sDCs) in specific-pathogen-free chickens following inoculation with IBDV vaccine strain (D78) and a very virulent (vv) strain (UPM0081). Following IBDV infection, enriched activated ch-sDCs were collected by using the negative selection method and were examined based on morphology and immunophenotyping to confirm the isolation method for dendritic cells (DCs). The presence of IBDV on enriched activated ch-sDCs was analyzed based on the immunofluorescence antibody test (IFAT), flow cytometry, and quantitative real-time PCR (RT-qPCR) while the mRNAs of several cytokines were detected using RT-qPCR. The isolated ch-sDCs resembled typical DC morphologies found in mammals by having a veiled shape and they grew in clusters. Meanwhile, the expression of DC maturation markers, namely CD86 and MHCII, were increased at day 2 and day 3 following vvIBDV and vaccine strain inoculation, respectively, ranging from 10% to 40% compared to the control at 2.55% (P < 0.05). At day 3 postinfection, IBDV VP3 proteins colocalized with CD86 were readily detected via IFAT and flow cytometry in both vaccine and vvIBDV strains. In addition, enriched activated ch-sDCs were also detected as positive based on the VP4 gene by RT-qPCR; however, a higher viral load was detected on vvIBDV compared to the vaccine group. Infection with vaccine and vvIBDV strains induced the enriched activated ch-sDCs to produce proinflammatory cytokines and Th1-like cytokines from day 3 onward; however, the expressions were higher in the vvIBDV group (P < 0.05). These data collectively suggest that enriched activated ch-sDCs were permissive to IBDV infection and produced a strong inflammatory and Th1-like cytokine response following vvIBDV infection as compared to the vaccine strain.
    Matched MeSH terms: Viral Vaccines/administration & dosage*; Viral Vaccines/immunology
  13. Wong SK, Tan WS, Omar AR, Tan CS, Yusoff K
    Acta Virol., 2009;53(1):35-41.
    PMID: 19301949
    Hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) plays a vital role in the viral infectivity, host immunity, and disease diagnosis. A portion of the HN gene encoding the ectodomain (nt 142-1739) was cloned and expressed in Escherichia coli yielding an insoluble HN protein and a soluble NusA-HN protein containing N-utilization substance A (NusA) fusion component. Both recombinant proteins were purified and used for immunization of chickens. The recombinant HN protein induced higher antibody titers as compared to the recombinant NusA-HN protein. These antibodies were able to react in immunoblot analysis with the corresponding recombinant proteins as well as with the HN protein of NDV.
    Matched MeSH terms: Viral Vaccines/genetics; Viral Vaccines/immunology*
  14. Wong LP, Alias H, Wong PF, Lee HY, AbuBakar S
    Hum Vaccin Immunother, 2020 09 01;16(9):2204-2214.
    PMID: 32730103 DOI: 10.1080/21645515.2020.1790279
    BACKGROUND: The development of a vaccine against SARS-CoV-2 infection is on the way. To prepare for public availability, the acceptability of a hypothetical COVID-19 vaccine and willingness to pay (WTP) were assessed to provide insights into future demand forecasts and pricing considerations.

    METHODS: A cross-sectional survey was conducted from 3 to 12 April 2020. The health belief model (HBM) was used to assess predictors of the intent to receive the vaccine and the WTP.

    RESULTS: A total of 1,159 complete responses was received. The majority reported a definite intent to receive the vaccine (48.2%), followed by a probable intent (29.8%) and a possible intent (16.3%). Both items under the perceived benefits construct in the HBM, namely believe the vaccination decreases the chance of infection (OR = 2.51, 95% CI 1.19-5.26) and the vaccination makes them feel less worry (OR = 2.19, 95% CI 1.03-4.65), were found to have the highest significant odds of a definite intention to take the vaccine. The mean ± standard deviation (SD) for the amount that participants were willing to pay for a dose of COVID-19 vaccine was MYR$134.0 (SD±79.2) [US$30.66 ± 18.12]. Most of the participants were willing to pay an amount of MYR$100 [US$23] (28.9%) and MYR$50 [US$11.5] (27.2%) for the vaccine. The higher marginal WTP for the vaccine was influenced by no affordability barriers as well as by socio-economic factors, such as higher education levels, professional and managerial occupations and higher incomes.

    CONCLUSIONS: The findings demonstrate the utility of HBM constructs in understanding COVID-19 vaccination intention and WTP.

    Matched MeSH terms: Viral Vaccines/economics
  15. Weingartl HM, Berhane Y, Caswell JL, Loosmore S, Audonnet JC, Roth JA, et al.
    J Virol, 2006 Aug;80(16):7929-38.
    PMID: 16873250
    Nipah virus (NiV), of the family Paramyxoviridae, was isolated in 1999 in Malaysia from a human fatality in an outbreak of severe human encephalitis, when human infections were linked to transmission of the virus from pigs. Consequently, a swine vaccine able to abolish virus shedding is of veterinary and human health interest. Canarypox virus-based vaccine vectors carrying the gene for NiV glycoprotein (ALVAC-G) or the fusion protein (ALVAC-F) were used to intramuscularly immunize four pigs per group, either with 10(8) PFU each or in combination. Pigs were boosted 14 days postvaccination and challenged with 2.5 x 10(5) PFU of NiV two weeks later. The combined ALVAC-F/G vaccine induced the highest levels of neutralization antibodies (2,560); despite the low neutralizing antibody levels in the F vaccinees (160), all vaccinated animals appeared to be protected against challenge. Virus was not isolated from the tissues of any of the vaccinated pigs postchallenge, and a real-time reverse transcription (RT)-PCR assay detected only small amounts of viral RNA in several samples. In challenge control pigs, virus was isolated from a number of tissues (10(4.4) PFU/g) or detected by real-time RT-PCR. Vaccination of the ALVAC-F/G vaccinees appeared to stimulate both type 1 and type 2 cytokine responses. Histopathological findings indicated that there was no enhancement of lesions in the vaccinees. No virus shedding was detected in vaccinated animals, in contrast to challenge control pigs, from which virus was isolated from the throat and nose (10(2.9) PFU/ml). Based on the data presented, the combined ALVAC-F/G vaccine appears to be a very promising vaccine candidate for swine.
    Matched MeSH terms: Viral Vaccines/immunology; Viral Vaccines/therapeutic use*
  16. Vignesh R, Shankar EM, Velu V, Thyagarajan SP
    Front Immunol, 2020;11:586781.
    PMID: 33101320 DOI: 10.3389/fimmu.2020.586781
    Matched MeSH terms: Viral Vaccines/immunology*
  17. Thakur N, Bailey D
    Microbes Infect, 2019;21(7):278-286.
    PMID: 30817995 DOI: 10.1016/j.micinf.2019.02.002
    Nipah virus is an emerging zoonotic paramyxovirus that causes severe and often fatal respiratory and neurological disease in humans. The virus was first discovered after an outbreak of encephalitis in pig farmers in Malaysia and Singapore with subsequent outbreaks in Bangladesh or India occurring almost annually. Due to the highly pathogenic nature of NiV, its pandemic potential, and the lack of licensed vaccines or therapeutics, there is a requirement for research and development into highly sensitive and specific diagnostic tools as well as antivirals and vaccines to help prevent and control future outbreak situations.
    Matched MeSH terms: Viral Vaccines/immunology
  18. Tan DS
    Med J Malaya, 1965 Sep;20(1):19-28.
    PMID: 4221407
    Matched MeSH terms: Viral Vaccines*
  19. Svetlova J, Gustin D, Manuvera V, Shirokov D, Shokina V, Prusakov K, et al.
    Int J Mol Sci, 2022 Oct 30;23(21).
    PMID: 36362010 DOI: 10.3390/ijms232113220
    Mutations in surface proteins enable emerging variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to escape a substantial fraction of neutralizing antibodies and may thus weaken vaccine-driven immunity. To compare available vaccines and justify revaccination, rapid evaluation of antibody (Ab) responses to currently circulating SARS-CoV-2 variants of interest (VOI) and concern (VOC) is needed. Here, we developed a multiplex protein microarray-based system for rapid profiling of anti-SARS-CoV-2 Ab levels in human sera. The microarray system was validated using sera samples from SARS-CoV-2-free donors and those diagnosed with COVID-19 based on PCR and enzyme immunoassays. Microarray-based profiling of vaccinated donors revealed a substantial difference in anti-VOC Ab levels elicited by the replication-deficient adenovirus vector-base (Sputnik V) and whole-virion (CoviVac Russia COVID-19) vaccines. Whole-virion vaccine-induced Abs showed minor but statistically significant cross-reactivity with the human blood coagulation factor 1 (fibrinogen) and thrombin. However, their effects on blood clotting were negligible, according to thrombin time tests, providing evidence against the concept of pronounced cross-reactivity-related side effects of the vaccine. Importantly, all samples were collected in the pre-Omicron period but showed noticeable responses to the receptor-binding domain (RBD) of the Omicron spike protein. Thus, using the new express Ab-profiling system, we confirmed the inter-variant cross-reactivity of the anti-SARS-CoV-2 Abs and demonstrated the relative potency of the vaccines against new VOCs.
    Matched MeSH terms: Viral Vaccines/genetics; Viral Vaccines/pharmacology
  20. Spradbrow PB, Ibrahim AL, Mustaffa-Babjee A, Kim SJ
    Avian Dis, 1978 Apr-Jun;22(2):329-35.
    PMID: 678237
    One-day-old chickens were transported from Australia to Malaysia and vaccinated orotracheally with an uninactivated vaccine prepared from avirulent Australian V4 strain of Newcastle disease virus (NDV). The vaccination regimes were as follows: group A, once, at 2 weeks old; group B, once, at 3 weeks old; group C, twice, at 2 and at 3 weeks old; group D, direct contact with groups A, B, and C; and group E, indirect contact with groups A, B, C, and D. Group F was unvaccinated controls. Challenge was with NDV virulent Ipoh AF 2240-226 strain, administered at 4 weeks old intramuscularly to 10 chickens in each group and orotracheally to 10 chickens in each group. The remaining chickens were challenged by contact with the inoculated chickens. Group mortalities following challenge were: A, 1/77; B, 1/34; C, 0/39; D, 0/45; E, 6/43; and F, 60/60.
    Matched MeSH terms: Viral Vaccines*
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