Development and characterization of a recombinant infectious bronchitis virus expressing the ectodomain region of S1 gene of H120 strain

Abstract

Infectious bronchitis (IB), caused by infectious bronchitis virus (IBV), is a highly contagious chicken disease, and can lead to serious economic losses in poultry enterprises. The continual introduction of new IBV serotypes requires alternative strategies for the production of timely and safe vaccines against the emergence of variants. Modification of the IBV genome using reverse genetics is one way to generate recombinant IBVs as the candidates of new IBV vaccines. In this study, the recombinant IBV is developed by replacing the ectodomain region of the S1 gene of the IBV Beaudette strain with the corresponding fragment from H120 strain, designated as rBeau-H120(S1e). In Vero cells, the virus proliferates as its parental virus and can cause syncytium formation. The peak titer would reach 10(5.9) 50% (median) tissue culture infective dose/mL at 24 h post-infection. After inoculation of chickens with the recombinant virus, it demonstrated that rBeau-H120(S1e) remained nonpathogenic and was restricted in its replication in vivo. Protection studies showed that vaccination with rBeau-H120 (S1e) at 7-day after hatch provided 80% rate of immune protection against challenge with 10(3) 50% embryos infection dose of the virulent IBV M41 strain. These results indicate that rBeau-H120 (S1e) has the potential to be an alternative vaccine against IBV based on excellent propagation property and immunogenicity. This finding might help in providing further information that replacement of the ectodomain fragment of the IBV Beaudette S1 gene with that from a present field strain is promising for IBV vaccine development.

Recombinant infectious bronchitis coronavirus H120 with the spike protein S1 gene of the nephropathogenic IBYZ strain remains attenuated but induces protective immunity

“…To reduce the problems associated with vaccine reversion, researchers have explored the option of creating vaccine viruses using reverse genetic technology (e.g., Beaudette strains carrying the S1 gene of the H120 vaccine strain, virulent M41 strain, or QX-like strain) [30,48]. However, the titer of the Beaudette strains carrying the S1 gene of the vaccine H120 strain only reaches 10 6.13 ± 0.23 EID 50 [49], which is lower than that of the H120 backbone strain. Therefore, we aimed to develop a recombinant rH120-S1/YZ strain based on the H120 vaccine strain that carries the S1 gene of the ck/CH/IBYZ/2011 strain (a Chinese QX-like nephoropathogenic strain) using reverse genetic technology [35,36].…”

The avian coronavirus spike protein

“…Vaccination with recombinant IBV Beaudette with spikes of virulent M41 (BeauR-M41(S); Hodgson et al, 2004) and 4/91 (BeauR-4/91(S); Armesto et al, 2011) protected chickens against a challenge with IBV M41 and -4/91, confirming the importance of homologous spike proteins in the induction of protective immune responses. Moreover, the presence of the S1 domain of IBV vaccine strain H120 in a Beaudette background bone was already sufficient to significantly decrease morbidity after challenge with the serologically related virulent M41 (Wei et al, 2014). The recombinant virus induced IBV-specific antibodies to a similar extend as the live attenuated H120 vaccine, and could result in fewer histopathological changes.…”

“…While M41, recombinant Beaudette and BeauR-M41(S) had the ability to produce progeny virus on primary chicken kidney cells, the Vero, BHK-21 and CEF cells only supported infection and replication of Beaudette (Casais et al, 2003). A recombinant Beaudette in which the S1 gene of Beaudette was replaced by that of H120 was recently generated (rBeau-H120(S1e)) and retained its ability to grow on Vero cells (Wei et al, 2014), indicating that the prerequisites for infection of cell culture cells resides in S2 sequence of Beaudette. The N-terminal S1 domain (M41.NTD, comprising aa 19-272 of the spike) and the C-terminal S1 domain (M41.CTD, comprising aa 273-532 of the spike) of M41 were applied to chicken trachea.…”

“…Exchange of the spike protein of Beaudette by that of virulent M41 and 4/91 IBV strains in the viral Beaudette genome resulted in apathogenic recombinant viruses BeauR-4/91(S) (Armesto et al, 2011) and BeauR-M41(S) (Hodgson et al, 2004); the latter only showing poor replication in trachea and nose compared to M41 (Hodgson et al, 2004). In addition, replacement of only the S1 domain of Beaudette by that of the vaccine strain H120 rendered nonpathogenic virus that could be isolated from tracheal swabs till day 6 (Wei et al, 2014), indicating that the recombinant virus had the ability to infect and replicate in the respiratory tract. To conclude to what extend the spike protein determines in vivo tropism clinical studies comparing the organ and cell preferences of the recombinant and parent viruses are needed.…”

Structural model of the SARS coronavirus E channel in LMPG micelles

“…No effective licensed treatments exist against coronavirus infections [3][4][5], but live attenuated vaccines (LAVs) [6][7][8][9][10] and fusion inhibitors [11] are promising strategies. One CoV component critical for pathogenesis is the envelope (E) protein, as reported in several coronaviruses, e.g., MERS and SARS-CoVs [12][13][14].…”