The expression in plants of an engineered VP2 protein of Infectious Bursal Disease Virus induces formation of structurally heterogeneous particles that protect from a very virulent viral strain

Construction and efficacy of recombinant Newcastle disease virus co-expressing VP2 and VP3 proteins of very virulent infectious bursal disease virus

Infectious bursal disease (IBD), triggered by the infectious bursal disease virus (IBDV), poses a substantial risk to the poultry industry due to its immunosuppressive nature and the emergence of highly virulent strains. Traditional vaccination strategies have limitations, prompting the need for novel approaches. This study aimed to develop a recombinant Newcastle disease virus (NDV) vector vaccine co-expressing IBDV VP2 and VP3 proteins to enhance immunogenicity and protective efficacy against IBDV. The recombinant Newcastle disease virus (rNDV) expressing both VP2 and VP3 (rNDV-VP2-VP3) was generated and compared to rNDV expressing VP2 alone (rNDV-VP2). The genetic stability and growth pattern of rNDV were evaluated and its immunogenicity was assessed in specific pathogen free (SPF) chickens. rNDV-VP2-VP3 vaccines induced higher levels of neutralising antibodies, no damage to immune organs, and significantly lower viral loads in the bursa of the falciparum. rNDV-VP2 group showed partial protection, while the placebo group exhibited severe lesions and higher mortality, suggesting that the vaccine was effective in preventing IBDV-induced damage. These findings suggest that co-expression of VP2 and VP3 in NDV vectors is a viable strategy for the development of an effective IBDV vaccine, providing a safe and effective method for controlling IBD in poultry.

Virus-like Particles Produced in Plants: A Promising Platform for Recombinant Vaccine Development

The capsid proteins of many viruses are capable of spontaneous self-assembly into virus-like particles (VLPs), which do not contain the viral genome and are therefore not infectious. VLPs are structurally similar to their parent viruses and are therefore effectively recognized by the immune system and can induce strong humoral and cellular immune responses. The structural features of VLPs make them an attractive platform for the development of potential vaccines and diagnostic tools. Chimeric VLPs can be obtained by attaching foreign peptides to capsid proteins. Chimeric VLPs present multiple copies of the antigen on their surface, thereby increasing the effectiveness of the immune response. Recombinant VLPs can be produced in different expression systems. Plants are promising biofactories for the production of recombinant proteins, including VLPs. The main advantages of plant expression systems are the overall low cost and safety of plant-produced products due to the absence of pathogens common to plants and animals. This review provides an overview of the VLP platform as an approach to developing plant-produced vaccines, focusing on the use of transient expression systems.

Effect of egg incubator temperature on sex differentiation in Korat chickens

The effect of incubator temperature on sex differentiation in Korat chickens was investigated. The experiments were divided into two sets: temperature applied throughout the entire incubation period and temperature applied during certain periods (days 3-6 of incubation) by either increasing above the standard or decreasing below the standard temperature. In each experiment, 300 Korat chicken eggs were separated into three groups of 5 repetitions, with 20 eggs in each group. This was done using a completely randomized design for each experiment: a group using a temperature below the standard for incubation (36.0 °C), a group using the standard incubation temperature (37.7 °C), and a group using a temperature above the standard for incubation (38.0 °C). W chromosomes were detected at hatch; histology examined reproductive structures after 35 days. Increasing the temperature to 38.0 °C throughout the entire incubation period resulted in no significant difference in hatching rates compared to the standard temperature (P > 0.05). Raising the temperature to 38.0 °C throughout the entire incubation and during certain periods resulted in changes in the reproductive structure of chickens, leading to a mismatch between chromosomal and gonadal sex, observed at 9.7% and 5.9% of individuals with W chromosomes possessed testes, indicating a mismatch between chromosomal and gonadal sex. However, decreasing the temperature to 36.0 °C throughout the incubation period resulted in lower hatching rates compared to the standard temperature (P < 0.05). Incubating eggs at 36.0 °C for specific periods resulted in 19.4% of genetic males developing ovaries instead of testes. The presence of ovaries in individuals without W chromosomes indicated this mismatch. The results of this study provide evidence that temperature plays a role in sex differentiation in Korat chickens, as demonstrated by the detection of W chromosomes and histological studies of testes and ovaries. Moreover, this study presents the first evidence in broilers that temperature can affect sex differentiation.

Pros and Cons on Use of Live Viral Vaccines in Commercial Chicken Flocks

The poultry industry is the largest source of meat and eggs for the growing human population worldwide. Key concerns in poultry farming are nutrition, management, flock health, and biosecurity measures. As part of the flock health, use of live viral vaccines plays a vital role in the prevention of economically important and common viral diseases. This includes diseases and production losses caused by Newcastle disease virus, infectious bronchitis virus, infectious laryngotracheitis virus, infectious bursal disease virus, Marek's disease virus, chicken infectious anemia virus, avian encephalomyelitis virus, fowlpox virus, and avian metapneumovirus. These viruses cause direct and indirect harms, such as financial losses worth millions of dollars, loss of protein sources, and threats to animal welfare. Flock losses vary by type of poultry, age of affected animals, co-infections, immune status, and environmental factors. Losses in broiler birds can consist of high mortality, poor body weight gain, high feed conversion ratio, and increased carcass condemnation. In commercial layers and breeder flocks, losses include higher than normal mortality rate, poor flock uniformity, drops in egg production and quality, poor hatchability, and poor day-old-chick quality. Despite the emergence of technology-based vaccines, such as inactivated, subunit, vector-based, DNA or RNA, and others, the attenuated live vaccines remain as important as before. Live vaccines are preferred in the global veterinary vaccine market, accounting for 24.3% of the global market share in 2022. The remaining 75% includes inactivated, DNA, subunit, conjugate, recombinant, and toxoid vaccines. The main reason for this is that live vaccines can induce innate, mucosal, cellular, and humoral immunities by single or multiple applications. Some live vaccine combinations provide higher and broader protection against several diseases or strains of viruses. This review aimed to explore insights on the pros and cons of attenuated live vaccines commonly used against major viral infections of the global chicken industry, and the future road map for improvement.

Infectious bursal disease virus' interferences with host immune cells: What do we know?

AbstractInfectious bursal disease virus (IBDV) induces one of the most important immunosuppressive diseases in chickens leading to high economic losses due increased mortality and condemnation rates, secondary infections and the need for antibiotic treatment. Over 400 publications have been listed in PubMed.gov in the last five years pointing out the research interest in this disease and the development of improved preventive measures. While B cells are the main target cells of the virus, also other immune and non-immune cell populations are affected leading a multifaceted impact on the normally well orchestrated immune system in IBDV-infected birds. Recent studies clearly revealed the contribution of innate immune cells as well as T cells to a cytokine storm and subsequent death of affected birds in the acute phase of the disease. Transcriptomics identified differential regulation of immune related genes between different chicken genotypes as well as virus strains, which may be associated with a variable disease outcome. The recent availability of primary B cell culture systems allowed a closer look into virus-host interactions during IBDV-infection. The new emerging field of research with transgenic chickens will open up new opportunities to understand the impact of IBDV on the host also under in vivo conditions, which will help to understand the complex virus-host interactions further.

Development of a Novel Assay Based on Plant-Produced Infectious Bursal Disease Virus VP3 for the Differentiation of Infected From Vaccinated Animals

Infectious bursal disease virus is the causative agent of Gumboro disease, a severe infection that affects young chickens and is associated with lymphoid depletion in the bursa of Fabricius. Traditional containment strategies are based either on inactivated or live-attenuated vaccines. These approaches have several limitations such as residual virulence or low efficacy in the presence of maternally derived antibodies (MDA) but, most importantly, the impossibility to detect the occurrence of natural infections in vaccinated flocks. Therefore, the development of novel vaccination strategies allowing the differentiation of infected from vaccinated animals (DIVA) is a priority. Recently, commercial vectored and experimental subunit vaccines based on VP2 have been proved effective in protecting from clinical disease and posed the basis for the development of novel DIVA strategies. In this study, an engineered version of the VP3 protein of IBDV (His-VP3) was produced in plants, successfully purified from Nicotiana benthamiana leaves, and used to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of anti-VP3 antibodies. The His-VP3 ELISA was validated with a panel of 180 reference sera and demonstrated to have 100% sensitivity (95% CI: 94.7-100.0) and 94.17% specificity (95% CI: 88.4-97.6). To evaluate the application of His-VP3 ELISA as a DIVA test, the novel assay was used to monitor, in combination with a commercial kit, detecting anti-VP2 antibodies, the immune response of chickens previously immunized with an inactivated IBDV vaccine, a recombinant Turkey herpes virus carrying the VP2 of IBDV (HVT-ND-IBD) or with plant-produced VP2 particles. The combined tests correctly identified the immune status of the vaccinated specific pathogen free white-leghorn chickens. Moreover, the His-VP3 ELISA correctly detected MDA against VP3 in commercial broiler chicks and showed that antibody titers fade with time, consistent with the natural decrease of maternally derived immunity. Finally, the novel assay, in combination with a VP2-specific ELISA, demonstrated its potential application as a DIVA test in chickens inoculated with VP2-based vaccines, being able to detect the seroconversion after challenge with a very virulent IBDV strain.

Oral Immunization With Plant-Based Vaccine Induces a Protective Response Against Infectious Bursal Disease

Infectious bursal disease virus (IBDV) is the etiological agent of an immunosuppressive and highly contagious disease that affects young birds causing important economic losses in the poultry industry worldwide. We have previously developed a plant-based vaccine candidate for infectious bursal disease (IBD) that is able to protect against infection with IBDV when administered through intramuscular (im) route. Given that oral vaccination is non-invasive and stimulates the immunity of the mucosal gastrointestinal surface, the initial site of contact and entry of IBDV, the aim of this work was to study if our immunogen was also able to elicit a protective immune response when orally administered. We demonstrated that 85% of the animals that received two oral doses of the vaccine formulation and all animals that were orally boosted after an im prime scheme developed virus neutralizing antibodies and were protected against IBDV infection, evidenced by the bursa/body weight (BB) ratio, absence of T-cell infiltration, and low viral load in bursa. Although mild to moderate bursal damage was observed in some of these animals, these lesions were not as severe as the ones observed in challenged control groups, which also presented signs of acute inflammation, bursal atrophy, T-cell infiltration, and absence of viral clearance. These results show that two immunizations with our recombinant immunogen are able to induce a specific and protective immune response in chicken against IBDV when orally administered in a prime/boost scheme or when the oral boost follows an im prime scheme. In conclusion, our oral plant-based vaccine candidate could represent a viable alternative to conventional vaccines and is of great interest to the poultry industry.