Progress, challenges and opportunities in fish vaccine development.

In 2014 the contribution of aquaculture to supply food for human consumption overtook wild-caught fish for the first time. Despite improvements in the aquaculture industry, it has been estimated that as much as 10% of all cultured aquatic animals are lost because of infectious diseases, amounting to >10 billion USD in losses annually on a global scale. Vaccination to prevent disease is used routinely in finfish aquaculture, especially for Atlantic salmon (Salmo salar), while in a limited capacity (or not at all) in many other fish species due to lack of vaccines, poor performance or cost. There has, nevertheless, been impressive progress in fish vaccine development over the last 4 decades with 24 licenced fish vaccines now commercially available for use in a variety of fish species. These comprise whole killed, peptide subunit, recombinant protein, DNA and live attenuated vaccines. Challenges do, however, still exist as the majority of commercial vaccines are killed whole cell pathogen preparations administered by intraperitoneal injection. This may not be the optimal route to deliver some vaccines, but lack of effective adjuvants and basic knowledge on immune response has hindered progress in the development of mucosal vaccines. The cost of injecting fish may also be prohibitive in some countries leading to disease treatment (e.g. with antibiotics) rather than using preventative measures. It is important that these issues are addressed as the industry continues to grow globally. Exciting opportunities exist for rapid development of fish vaccines in the future, with continued reduction in cost of technologies (e.g. of whole genome sequencing), regulations changing (e.g. DNA vaccines can now authorised in Europe), the introduction of novel antigen expression and delivery systems (such as virus-like particles, VLPs), development of novel adjuvants and advancements in the elucidation of basic mechanisms of mucosal immunity. Development of effective mucosal vaccines and optimisation of their delivery will facilitate novel vaccine development, and enable the aquaculture industries in LMIC to use vaccination routinely in the future. In addition, effective use of emergency (autogenous) vaccines will assist in tackling emerging disease challenges.

Vaccines and immune protection of principal Mediterranean marine fish species.

This review describes and summarizes the knowledge on established and experimental vaccines developed against viral and bacterial pathologies affecting the most important farmed marine finfish species present in the Mediterranean area, namely European seabass Dicentrarchus labrax, sea bream Sparus aurata, turbot Psetta maxima and meagre Argyrosomus regius. The diseases that have been recorded in seabass, sea bream and meagre are caused by bacteria Vibrio anguillarum, Photobacterium damselae, Tenacibaculum maritimum as well as by viruses such as Viral Encephalopathy and Retinopathy/Viral Nervous Necrosis and Lymphocystic disease. The main pathologies of turbot are instead bacteriosis provoked by Tenacibaculum maritimum, Aeromonas sp. and Vibrio anguillarum, and virosis by viral hemorrhagic septicaemia virus. Some vaccines have been optimized and are now regularly available for the majority of the above-mentioned pathogens. A measurable immune protection has been conferred principally against Vibrio anguillarum, Photobacterium damselae sub. piscicida and VER/VNN.

Current status of fish vaccines in Japan.

Aquaculture is an important industry in Japan for the sustainable production of fish. It contributes to the diversity of Japanese traditional food culture, which uses fish such as "sushi" and "sashimi". In the recent aquaculture setting in Japan, infectious diseases have been an unavoidable problem and have caused serious economic losses. Therefore, there is an urgent need to overcome the disease problem to increase the productivity of aquaculture. Although our country has developed various effective vaccines against fish pathogens, which have contributed to disease prevention on fish farms, infectious diseases that cannot be controlled by conventional inactivated vaccines are still a problem. Therefore, other approaches to developing effective vaccines other than inactivated vaccines are required. This review introduces the vaccine used in Japan within the context of the current status of finfish aquacultural production and disease problems. This review also summarizes the current research into vaccine development and discusses the future perspectives of fish vaccines, focusing on the problems associated with vaccine promotion in Japan.

Recent progress in applications of nanoparticles in fish medicine: A review.

Nanotechnology has become an extensive field of research due to the unique properties of nanoparticles, which enable novel applications. Nanoparticles have found their way into many applications in the field of medicine, including diagnostics, vaccination, drug and gene delivery. In this review, we focused on the antimicrobial effects of nanoparticles, with particular emphasis on the problem of antibiotic resistant bacteria in fisheries. The use of nanoparticle-based vaccines against many viral pathogens is a developing field in fish medicine research. Nanoparticles have gained much interest as a specific and sensitive tool for diagnosis of bacterial, fungal and viral diseases in aquaculture. Nevertheless our review also highlights the many applications of nanotechnology that are still to be explored in fish medicine. FROM THE CLINICAL EDITOR: Advance in nanotechnology has enabled the development of nanomedicine, with many ideas being used in clinical diagnosis and therapy. In this review article, the authors described the current use of nanotechnology in fish medicine. The knowledge would also impart important information for our daily living.

Challenges in Veterinary Vaccine Development.

Animals provide food and clothing in addition to other value-added products. Changes in diet and lifestyle have increased the consumption and the use of animal products. Infectious diseases in animals are a major threat to global animal health and its welfare; their effective control is crucial for agronomic health, for safeguarding food security and also alleviating rural poverty. Development of vaccines has led to increased production of healthy poultry, livestock, and fish. Animal production increases have alleviated food insecurity. In addition, development of effective vaccines has led to healthier companion animals. However, challenges remain including climate change that has led to enhancement in vectors and pathogens that may lead to emergent diseases in animals. Preventing transmission of emerging infectious diseases at the animal-human interface is critically important for protecting the world population from epizootics and pandemics. Hence, there is a need to develop new vaccines to prevent diseases in animals. This review describes the broad challenges to be considered in the development of vaccines for animals.

Sleeping With the Enemy? The Current Knowledge of Piscine Orthoreovirus (PRV) Immune Response Elicited to Counteract Infection.

Piscine orthoreovirus (PRV) is a virus in the genus Orthoreovirus of the Reoviridae family, first described in 2010 associated with Heart and Skeletal Muscle Inflammation (HSMI) in Atlantic salmon (Salmo salar). Three phases of PRV infection have been described, the early entry and dissemination, the acute dissemination phase, and the persistence phase. Depending on the PRV genotype and the host, infection can last for life. Mechanisms of immune response to PRV infection have been just beginning to be studied and the knowledge in this matter is here revised. PRV induces a classical antiviral immune response in experimental infection of salmonid erythrocytes, including transcriptional upregulation of ifn-α, rig-i, mx, and pkr. In addition, transcript upregulation of tcra, tcrb, cd2, il-2, cd4-1, ifn-γ, il-12, and il-18 has been observed in Atlantic salmon infected with PRV, indicating that PRV elicited a Th1 type response probably as a host defense strategy. The high expression levels of cd8a, cd8b, and granzyme-A in PRV-infected fish suggest a positive modulatory effect on the CTL-mediated immune response. This is consistent with PRV-dependent upregulation of the genes involved in antigen presentation, including MHC class I, transporters, and proteasome components. We also review the potential immune mechanisms associated with the persistence phenotype of PRV-infected fish and its consequence for the development of a secondary infection. In this scenario, the application of a vaccination strategy is an urgent and challenging task due to the emergence of this viral infection that threatens salmon farming.