Molecular and antigenic characteristics of Massachusetts genotype infectious bronchitis coronavirus in China

Abstract

In this study, 418 IBVs were isolated in samples from 1717 chicken flocks. Twenty-nine of the isolates were classified as the Massachusetts genotype. These 29 isolates, as well as two previously isolated Massachusetts genotype IBV strains, were studied further. Of the 31 strains, 24 were H120-like and two were M41-like isolates as determined by complete genomic sequence analysis, indicating that most of the IBV isolates were likely the reisolated vaccine virus. The remaining five IBV isolates, ck/CH/LHB/111172, ck/CH/LSD/111219, ck/CH/LHB/130598, ck/CH/LDL/110931, and ck/CH/LHB/130573, were shown to have originated from natural recombination events between an H120-like vaccine strain and other types of viruses. The virus cross-neutralization test found that the antigenicity of ck/CH/LHB/111172, ck/CH/LSD/111219, and ck/CH/LHB/130598 was similar to that of H120. Vaccination with the H120 vaccine offered complete protection against challenge with these isolates. However, isolates ck/CH/LDL/110931 and ck/CH/LHB/130573 were serotypically different from their parental viruses and from other serotypes in this study. Furthermore, vaccination with the H120 vaccine did not provide protection against challenge with these two isolates. The results of this study demonstrated that recombination is the mechanism that is responsible for the emergence of new serotype strains, and it has the ability to alter virus serotypes. Therefore, IBV surveillance of chicken flocks vaccinated with IBV live vaccines, as well as the consideration of new strategies to effectively control IBV infection using inactivated or/and genetically engineered vaccines, is of great importance.

Greater Protection against Virulent Infectious Bronchitis Virus Challenge Conferred by Recombinant Baculovirus Co-expressing S1 and N Proteins

“…As we know, IBV continuously evolves and there are scores of serotypes. Little or no cross-protection confers between different serotypes of IBVs [6,7]. Therefore, the universal IBV vaccines that protect against varying serotypes of IBV are imperative.…”

“…The IBV genome is variable and there are dozens of IBV serotypes. There is little or no cross-protection between different serotypes of IBVs or circulating variant viruses, frequently leading to immune failures and making it extremely difficult to control the disease [5][6][7].…”

Serotype, antigenicity, and pathogenicity of a naturally recombinant TW I genotype infectious bronchitis coronavirus in China

“…Nine IBV strains, including four vaccine strains (H120, LDT3-A, 4/91, and Connecticut (Conn)), four attenuated strains (ck/CH/LDL/ 091022 [LDL/091022], ck/CH/LSD/120720 [LSD/120720], ck/CH/ LGX/100508 [LGX/100508], and ck/CH/LDL/97I [LDL/97I]) and the ck/CH/LDL/140520 (nrTW I) strain (Xu et al, 2016), were used in this study. The IBV strains LDL/091022 , LSD/ 120720, and LGX/100508 (Chen et al, 2015) were isolated in China and belong to the LX4 type. These three strains were attenuated by serially passaging them 120 (P120), 90 (P90), and 70 (P70) times, respectively, in 10-day-old SPF chicken eggs.…”

“…Each of the virus stocks was prepared in 10-dayold embryonated SPF chicken eggs by the allantoic route of inoculation, and the infectious allantoic fluid was collected 48 h post-inoculation as previously described (Liu et al, 2009a). The titers of the viruses were determined as previously described (Chen et al, 2015), and the median embryo infectious dose (EID 50 ) was calculated using the method of Reed and Muench (1938).…”

“…Thus far, two major groups of classification systems, including functional tests that examine the biological functions of a virus (immunotypes, protectotypes, and serotypes) and non-functional tests that assess the viral genome (genotypes), are commonly used for IBV typing (de Wit, 2000). For a specific IBV strain, although evidence from some studies suggests that there is a high correlation between the genotype and serotype, other studies have presented conflicting data (de Wit, 2000;Zhang et al, 2015;Chen et al, 2015), which may lead to contradictory results. The disadvantages of each system are that they only analyze one or several characteristics of a virus strain.…”