Virus-like particles in a new vaccination approach against infectious laryngotracheitis

Reconstitution and Mutagenesis of Avian Infectious Laryngotracheitis Virus from Cosmid and Yeast Centromeric Plasmid Clones

The genomes of numerous herpesviruses have been cloned as infectious bacterial artificial chromosomes. However, attempts to clone the complete genome of infectious laryngotracheitis virus (ILTV), formally known as Gallid alphaherpesvirus-1, have been met with limited success. In this study, we report the development of a cosmid/yeast centromeric plasmid (YCp) genetic system to reconstitute ILTV. Overlapping cosmid clones were generated that encompassed 90% of the 151-Kb ILTV genome. Viable virus was produced by cotransfecting leghorn male hepatoma (LMH) cells with these cosmids and a YCp recombinant containing the missing genomic sequences - spanning the TRS/UL junction. An expression cassette for green fluorescent protein (GFP) was inserted within the redundant inverted packaging site (ipac2), and the cosmid/YCp-based system was used to generate recombinant replication-competent ILTV. Viable virus was also reconstituted with a YCp clone containing a BamHI linker within the deleted ipac2 site, further demonstrating the nonessential nature of this site. Recombinants deleted in the ipac2 site formed plaques undistinguished from those viruses containing intact ipac2. The 3 reconstituted viruses replicated in chicken kidney cells with growth kinetics and titers similar to the USDA ILTV reference strain. Specific pathogen-free chickens inoculated with the reconstituted ILTV recombinants succumbed to levels of clinical disease similar to that observed in birds inoculated with wildtype viruses, demonstrating the reconstituted viruses were virulent. IMPORTANCE Infectious laryngotracheitis virus (ILTV) is an important pathogen of chicken with morbidity of 100% and mortality rates as high as 70%. Factoring in decreased production, mortality, vaccination, and medication, a single outbreak can cost producers over a million dollars. Current attenuated and vectored vaccines lack safety and efficacy, leaving a need for better vaccines. In addition, the lack of an infectious clone has also impeded understanding viral gene function. Since infectious bacterial artificial chromosome (BAC) clones of ILTV with intact replication origins are not feasible, we reconstituted ILTV from a collection of yeast centromeric plasmids and bacterial cosmids, and identified a nonessential insertion site within a redundant packaging site. These constructs and the methodology necessary to manipulate them will facilitate the development of improved live virus vaccines by modifying genes encoding virulence factors and establishing ILTV-based viral vectors for expressing immunogens of other avian pathogens.

The production of Newcastle disease virus-like particles in Nicotiana benthamiana as potential vaccines

Newcastle disease (ND) is a highly contagious viral respiratory and neurological disease that has a severe impact on poultry production worldwide. In the present study, an expression platform was established for the transient production in N.bethamiana of ND virus-like particles (VLPs) for use as vaccines against ND. The expression of the ND Fusion (F) and/or Hemagglutinin-neuraminidase (HN) proteins of a genotype VII.2 strain formed ND VLPs in planta as visualized under the transmission electron microscope, and HN-containing VLPs agglutinated chicken erythrocytes with hemagglutination (HA) titres of up to 13 log₂.The immunogenicity of the partially-purified ND VLPs was confirmed in specific-pathogen-free White leghorn chickens. Birds receiving a single intramuscular immunization with 1024 HA units (10 log₂) of the F/HN ND VLPs administered with 20% [v/v] Emulsigen^®-P adjuvant, seroconverted after 14 days with F- and HN-specific antibodies at ELISA titres of 5705.17 and HI geometric mean titres (GMTs) of 6.2 log₂, respectively. Furthermore, these ND-specific antibodies successfully inhibited viral replication in vitro of two antigenically closely-related ND virus isolates, with virus-neutralization test GMTs of 3.47 and 3.4, respectively. Plant-produced ND VLPs have great potential as antigen-matched vaccines for poultry and other avian species that are highly immunogenic, cost-effective, and facilitate prompt updating to ensure improved protection against emerging ND field viruses.

Virus-Like Particles: Revolutionary Platforms for Developing Vaccines Against Emerging Infectious Diseases

Virus-like particles (VLPs) are nanostructures that possess diverse applications in therapeutics, immunization, and diagnostics. With the recent advancements in biomedical engineering technologies, commercially available VLP-based vaccines are being extensively used to combat infectious diseases, whereas many more are in different stages of development in clinical studies. Because of their desired characteristics in terms of efficacy, safety, and diversity, VLP-based approaches might become more recurrent in the years to come. However, some production and fabrication challenges must be addressed before VLP-based approaches can be widely used in therapeutics. This review offers insight into the recent VLP-based vaccines development, with an emphasis on their characteristics, expression systems, and potential applicability as ideal candidates to combat emerging virulent pathogens. Finally, the potential of VLP-based vaccine as viable and efficient immunizing agents to induce immunity against virulent infectious agents, including, SARS-CoV-2 and protein nanoparticle-based vaccines has been elaborated. Thus, VLP vaccines may serve as an effective alternative to conventional vaccine strategies in combating emerging infectious diseases.

Infectious laryngotracheitis: Etiology, epidemiology, pathobiology, and advances in diagnosis and control - a comprehensive review

Infectious laryngotracheitis (ILT) is a highly contagious upper respiratory tract disease of chicken caused by a Gallid herpesvirus 1 (GaHV-1) belonging to the genus Iltovirus, and subfamily Alphaherpesvirinae within Herpesviridae family. The disease is characterized by conjunctivitis, sinusitis, oculo-nasal discharge, respiratory distress, bloody mucus, swollen orbital sinuses, high morbidity, considerable mortality and decreased egg production. It is well established in highly dense poultry producing areas of the world due to characteristic latency and carrier status of the virus. Co-infections with other respiratory pathogens and environmental factors adversely affect the respiratory system and prolong the course of the disease. Latently infected chickens are the primary source of ILT virus (ILTV) outbreaks irrespective of vaccination. Apart from conventional diagnostic methods including isolation and identification of ILTV, serological detection, advanced biotechnological tools such as PCR, quantitative real-time PCR, next generation sequencing, and others are being used in accurate diagnosis and epidemiological studies of ILTV. Vaccination is followed with the use of conventional vaccines including modified live attenuated ILTV vaccines, and advanced recombinant vector vaccines expressing different ILTV glycoproteins, but still these candidates frequently fail to reduce challenge virus shedding. Some herbal components have proved to be beneficial in reducing the severity of the clinical disease. The present review discusses ILT with respect to its current status, virus characteristics, epidemiology, transmission, pathobiology, and advances in diagnosis, vaccination and control strategies to counter this important disease of poultry.

Development and application of a colloidal gold test strip for the rapid detection of the infectious laryngotracheitis virus

Infectious laryngotracheitis disease is an acute, highly contagious viral disease seriously affecting poultry industry worldwide. In this study, a rapid and simple immune colloidal gold test strip for detecting infectious laryngotracheitis virus (ILTV) was developed based on membrane chromatography with monoclonal antibodies (mAbs) against gJ protein of ILTV and systematically evaluated for the detection of ILTV from clinical samples. mAb 2D4 1D7 was conjugated with colloidal gold as the detector antibody on the test strip. Another mAb, 1D8 1G3, was used as the capture complex at the test line (T-line), and goat antimouse IgG antibody was used as the capture antibody at the control line (C-line). The colloidal gold test strip showed high specificity in the detection of ILTV, with no cross-reaction with other avian pathogens, including infectious bronchitis virus, infectious bursal disease virus, avian influenza virus, Newcastle disease virus, fowl adenoviruses, and Marek's disease virus. Besides, the detection limit of this method was as low as 60 ELD₅₀/mL for the ILTV Wanggang strain. Furthermore, we evaluated its application in 260 clinical samples suspected of infection with ILTV. Results from the strip test were nearly identical with those from real-time PCR (coincidence rate 99.6%) and showed higher sensitivity than conventional PCR. All the results obtained in this study indicated that the colloidal gold test strip can be applied as a simple, rapid, sensitive, and specific diagnostic tool for the detection of ILTV, especially in resource-limited areas.