Genotype VII Newcastle disease viruses are associated with huge economic losses in the global poultry industry. Despite the intensive applications of vaccines, disease outbreaks caused by those viruses continue to occur frequently even among the vaccinated poultry farms. An important factor in the suboptimal protective efficacy of the current vaccines is the genetic mismatch between the prevalent strains and the vaccine strains. Therefore, in the present study, an effective and stable genotype-matched live attenuated Newcastle disease virus (NDV) vaccine was developed using reverse genetics, based on a recently isolated virulent naturally recombinant NDV IBS025/13 Malaysian strain. First of all, the sequence encoding the fusion protein (F) cleavage site of the virus was modified in silico from virulent polybasic (RRQKRF) to avirulent monobasic (GRQGRL) motif. The entire modified sequence was then chemically synthesized and inserted into pOLTV5 transcription vector for virus rescue. A recombinant virus termed mIBS025 was successfully recovered and shown to be highly attenuated based on OIE recommended pathogenicity assessment indices. Furthermore, the virus was shown to remain stably attenuated and retain the avirulent monobasic F cleavage site after 15 consecutive passages in specific-pathogen-free embryonated eggs and 12 passages in one-day-old chicks. More so, the recombinant virus induced a significantly higher hemagglutination inhibition antibody titre than LaSota although both vaccines fully protected chicken against genotype VII NDV induced mortality and morbidity. Finally, mIBS025 was shown to significantly reduce both the duration and quantity of cloacal and oropharyngeal shedding of the challenged genotype VII virus compared to the LaSota vaccine. These findings collectively indicate that mIBS025 provides a better protective efficacy than LaSota and therefore can be used as a promising vaccine candidate against genotype VII NDV strains.

Background The commercially available Newcastle disease (ND) vaccines were developed based on Newcastle disease virus (NDV) isolates genetically divergent from field strains that can only prevent clinical disease, not shedding of virulent heterologous virus, highlighting the need to develop genotype-matched vaccines Objectives This study examined the efficacy of the NDV genotype-matched vaccine, mIBS025 strain formulated in standard vaccine stabilizer, and in carboxymethyl sago starch-acid hydrogel (CMSS-AH) following vaccination via an eye drop (ED) and drinking water (DW). Methods A challenge virus was prepared from a recent NDV isolated from ND vaccinated flock. Groups of specific-pathogen-free chickens were vaccinated with mIBS025 vaccine strain prepared in a standard vaccine stabilizer and CMSS-AH via ED and DW and then challenged with the UPM/NDV/IBS362/2016 strain. Results Chickens vaccinated with CMSS-AH mIBS025 ED (group 2) developed the earliest and highest Hemagglutination Inhibition (HI) NDV antibody titer (8log 2 ) followed by standard mIBS025 ED (group 3) (7log 2 ) both conferred complete protection and drastically reduced virus shedding. By contrast, chickens vaccinated with standard mIBS025 DW (group 5) and CMSS-AH mIBS025 DW (group 4) developed low HI NDV antibody titers of 4log 2 and 3log 2 , respectively, which correspondingly conferred only 50% and 60% protection and continuously shed the virulent virus via the oropharyngeal and cloacal routes until the end of the study at 14 dpc. Conclusions The efficacy of mIBS025 vaccines prepared in a standard vaccine stabilizer or CMSS-AH was affected by the vaccination routes. The groups vaccinated via ED had better protective immunity than those vaccinated via DW.

Frequent Newcastle disease (ND) outbreaks in poultry have been reported in Southeast Asia, including Malaysia. However, limited studies have been carried out on detecting the Newcastle disease virus (NDV) from non-poultry birds. In this study, the detections of NDV were carried out using tissues samples from suspected ND cases from commercial chickens and swab samples of non-poultry birds captured in bird sanctuaries. Five samples from commercial chickens and one sample from black swans were found positive for ND. They were classified as velogenic NDV based on the partial sequencing of the fusion (F) gene, which revealed the amino acid motif on the F cleavage site of 112RRQKRF117. In addition, phylogenetic analysis based on partial F gene showed that all NVD isolates are classified as class II genotype VII subgenotype VII.2 (VIIi) and are clustered together with NDVs isolated from chickens in 2017 in Indonesia. This finding indicates the occurrence of subgenotype VII.2 (VIIi) as the fifth panzootic of ND in Malaysia and the importance of the epidemiology of virulent NDV in various avian species.

Aim:Genotype VII Newcastle disease virus (NDV) is the most predominant NDV strains that circulating in Malaysia; thus, this study was aimed to determine the susceptibility of Japanese quails toward genotype VII NDV. Clinical signs, gross pathological lesions of organs, positive detection of virus in organs and cloacal swabs, as well as the expression of the antibody titer, were used as parameters to assess the susceptibility of Japanese quails following infection of genotype VII NDV.Materials and Methods:About 20 quails were divided into three groups (n=8 for Groups A and B; n=4 for the control group). The quails in the Groups A and B were infected via intraocular route with 0.03 ml of 103.5 ELD50 and 107.0 ELD50 of NDV strain IBS 002, respectively, while the control group received 1× phosphate-buffered saline. Cloacal swabs and necropsy were taken on day 7 post-infection for all quails were subjected to one-step reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) for detection of virus and examination for gross pathological lesion, respectively. Blood serums of infected quails were taken on day 10, 14, and 21 post-day infections and were subjected for hemagglutination inhibition (HI) assay.Results:Depression and ruffled feathers, trachea rales, leg paralysis, and torticollis were shown in some of the quails in both infected groups. Based on statistical analysis, there was no significant difference (p>0.05) in clinical signs between the infected groups. The results for RT-qPCR were found to be negative for all groups, and no gross pathological lesions of organs observed for quails in both infected groups. Trachea, proventriculus, and cecal tonsil were taken for the detection of NDV by RT-qPCR, and some of the organ samples showed positive detection of virus in both infected groups. HI assay showed an increase in mean titers of antibody across time and between infected groups.Conclusion:In summary, Japanese quails are susceptible to genotype VII NDV based on parameters assessed.

This research aims to evaluate the immunogenicity of different doses of HIPRAVIAR® BPL2 inactivated Newcastle disease virus (NDV) LaSota vaccine. Specific-pathogen-free day-old chicks were divided into 3 different groups, and each group was vaccinated subcutaneously with the vaccine dose of 0.1, 0.2, and 0.5 ml, respectively. Blood samples were collected to measure NDV-specific antibody titers using a hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA). The HI result showed that birds vaccinated with 0.5 ml HIPRAVIAR® BPL2 vaccine showed an increased statistically significant antibody titer compared to the other doses. Similarly, the ELISA result corroborated the HI finding. No significant difference between the results was detected when the antibody titers were measured using two ELISA kits, Biocheck CK116, and CIVTEST® AVI NDV. The percentage antibody-positive test based on HI amongst the different days post-vaccination showed that all the birds were positive from 28 to 42 days following vaccination with HIPRAVIAR® BPL2 0.5 ml (group D), whereas the highest percentage of antibody positivity were 80% and 70% at 42 days post-vaccination with HIPRAVIAR® BPL2 0.1 ml (group B) and HIPRAVIAR® BPL2 0.2 ml (group C), respectively. In conclusion, besides the difference in seroconversion, all the vaccine doses used had important levels of seroconversion and positivity.