Advances in Vaccine Development of the Emerging Novel Genotype Fowl Adenovirus 4

Abstract

Fowl adenovirus (FAdV) was first reported in Angara Goth, Pakistan, in 1987. For this reason, it is also known as “Angara disease.” It was later reported in China, Japan, South Korea, India, the United States, Canada, and other countries and regions, causing huge economic losses in the poultry industry worldwide. Notably, since June 2015, a natural outbreak of severe hydropericardium hepatitis syndrome (HHS), associated with a hypervirulent novel genotype FAdV-4 infection, has emerged in most provinces of China. The novel virus FAdV-4 spread rapidly and induced a 30-100% mortality rate, causing huge economic losses and threatening the green and healthy poultry breeding industry. Vaccines against FAdV-4, especially the emerging novel genotype, play a critical role and will be the most efficient tool for preventing and controlling HHS. Various types of FAdV-4 vaccines have been developed and evaluated, such as inactivated, live-attenuated, subunit, and combined vaccines. They have made great contributions to the control of HHS, but the details of cross-protection within FAdVs and the immunogenicity of different vaccines require further investigation. This review highlights the recent advances in developing the FAdV-4 vaccine and promising new vaccines for future research.

Molecular Characterisation of Fowl Adenovirus Associated With Hydropericardium Hepatitis Syndrome in Broiler and Layer Breeders in Azerbaijan

“…These results suggest that strains detected in this study might have been deriven from a common ancestor FAdV-4 virus circulating amongst neighboring regions. Similarly, it is possible that strains detected in this study might have been originated from the virulent strain detected in China in 2015 [32,38] since the 99% homology was observed with virulent strain of China [38] as well as the severity of clinical signs and pathological lesions observed in this study. However, the epidemiological relationship is unclear at present and warrants further investigations.…”

“…Hydropericardium hepatitis syndrome (HHS), formerly called hydropericardium syndrome (HPS) and Angara disease, was first described in 1987 in broiler chickens in Angara Goth, Pakistan [3]. Since 2015, after the detection of hypervirulent strain of FAdV-4 in China [32,38] HHS cases have increased and severe outbreaks of HHS have been reported in chicken flocks in many countries like Iran, India, China, Egypt, United Arab Emirates, Poland and USA causing economical losses especially in 3-5 weeks old broilers with mortality rate up to 100% [6][7][8][9][10][11][12][13][14][15][16][17]. After the report of hypervirulent FAdV-4 strain and its rapid spread in China [32,38] the emergent novel FAdV-4 serotype became very important virus to investigate in terms of molecular epidemiology and vaccine design.…”

“…Since 2015, after the detection of hypervirulent strain of FAdV-4 in China [32,38] HHS cases have increased and severe outbreaks of HHS have been reported in chicken flocks in many countries like Iran, India, China, Egypt, United Arab Emirates, Poland and USA causing economical losses especially in 3-5 weeks old broilers with mortality rate up to 100% [6][7][8][9][10][11][12][13][14][15][16][17]. After the report of hypervirulent FAdV-4 strain and its rapid spread in China [32,38] the emergent novel FAdV-4 serotype became very important virus to investigate in terms of molecular epidemiology and vaccine design. Since there is no report on the adenoviral diseases in chickens in Azerbaijan at present, outbreaks of HHS in broilers and layer breeders were investigated in this study to determine circulating strains and genetic diversity in relation to clinico-pathological signs.…”

An Inactivated Novel Trivalent Vaccine Provides Complete Protection against FAdV-4 Causing Hepatitis-Hydropericardium Syndrome and FAdV-8b/-11 Causing Inclusion Body Hepatitis

“…However, the intrinsic serotype-specifc neutralizing activity of Fiber limits the application and efcacy of fber-based vaccines [36]. For controlling HHS, vaccine candidates based on inactivated FAdV-4 or Fiber-2 protein have been generated and proven to be efcient [20,22,24,[37][38][39][40][41][42]. In order to develop potential vaccines providing broad crossprotection against HHS and IBH caused by various serotypes of FAdV, several bivalent vaccine candidates against both FAdV-4 and FAdV-8b, FAdV-8a and FAdV-8b, or FAdV FAdV-4 possesses two fber genes that encode Fiber-1 and Fiber-2 proteins.…”

Local cellular immune response plays a key role in protecting chickens against hepatitis-hydropericardium syndrome (HHS) by vaccination with a recombinant fowl adenovirus (FAdV) chimeric fiber protein

“…Among these diseases, HHS and IBH share common pathogenesis and immunological features, as opposed to AGE (2,4). Despite the worldwide occurrence of FAdVs and their growing economic impact, the lack of broadly protective and commercially accessible immunization strategies has led to extensive investigations on experimental vaccine antigens (3)(4)(5)(6)(7). In regards to subunit vaccines, the fiber protein, one of the major structural capsid components and surface antigens, has proven highly effective against HHS-and IBH-causing strains (8)(9)(10)(11)(12)(13)(14)(15).…”