Preliminary evaluation of the haemagglutination and haemagglutination inhibition tests for avian infectious bronchitis virus

Comparison of the haemagglutination inhibition test and the serum neutralisation test in tracheal organ cultures for typing infectious bronchitis virus strains

Five strains of infectious bronchitis (IB) virus, which had been compared antigenically by the serum neutralisation (SN) test in tracheal organ cultures (OC), were arbitrarily coded and then compared by the haemagglutination inhibition (HI) test. Their antigenic relationships were found to be similar by the two methods but, because of the high and variable cross reactions found in the HI test, the differences between the strains were less clear by that method. It was concluded that the HI test, in its present state of development, is considerably less type-specific than the SN test in OC, and cannot be recommended for defining antigenic relationships between strains of IB virus. However, it retains its value for diagnosing IB or for monitoring the vaccinal status of flocks.

Comparison of the enzyme-linked immunosorbent assay (ELISA), haemagglutination inhibition test and agar gel precipitation test for detection of antibodies to avian infectious bronchitis virus

The immune response after vaccination with infectious bronchitis virus (IBV) under field conditions was measured by the ELISA, haemagglutination-inhibition (HI) and agar-gel precipitin (AGP), tests. Vaccinations were performed in three flocks and one experimental group via the drinking water with the vaccine strains H 120 and H 52. In each flock 40 random serum samples were taken every 2 weeks and tested individually. In the experimental group blood samples were collected every week from each of the 10 chickens. The primary vaccination with H 120 resulted in a rapid increase of antibody titre as detected by ELISA followed by a slow decrease over the next few weeks. By the HI and AGP tests no antibody responses could be seen after this primary vaccination. Revaccination with the H 52 strain provoked a further increase in ELISA titres. In the experimental group, and in flock W, a similar increase occurred by the HI test and precipitating antibodies appeared. The formation of HI antibodies in flock T (nipple waterers) was somewhat retarded and precipitating antibodies were just detectable. In flock F revaccination did not result in the immediate production of HI and AGP antibodies. However, 6 weeks after revaccination a significant rise in ELISA, HI and AGP antibodies was observed, probably as the result of a field infection. It was demonstrated that, based on the higher sensitivity, the ELISA test is more suitable than HI and AGP to monitor antibody responses to vaccination against infectious bronchitis. Strain specificity in the HI test is discussed as a reason for its failure to detect antibodies after primary vaccination with the highly attenuated vaccine strain H 120.

Relationship between several criteria of challenge-immunity and humoral immunity in chickens vaccinated with avian infectious bronchitis vaccines

Several methods were compared for assessing the immunity of chickens vaccinated with avian-infectious bronchitis virus (IBV) by observing tracheal ciliary activity, respiratory signs and virus recovery from several organs following challenge with virus which had not been passaged in embryos. All chickens vaccinated twice with live Kita-1 strain were protected according to all criteria. However, in chickens vaccinated with killed IBV and with H-120 strain 13 weeks earlier, respiratory signs were present and tracheal virus was isolated from the birds with ciliostasis regardless of their having significant levels of haemagglutination inhibiting (HI) antibody. This indicated that only observing the ciliary activity is insufficient for assessing complete immunity and no direct correlation exists between the serum HI titre and the presence of ciliostasis, respiratory signs and virus recovery from tracheas, excluding those from kidneys and genitalia. Regardless of the serum HI titres at challenge, full protection based on the six criteria was found in some birds at 1 week and in most chickens from 2 to 6 weeks after intraocular vaccination with live Kita-1 strain.

Comparative studies with an enzyme-linked immunosorbent assay (ELISA) for antibodies to avian infectious bronchitis virus

An indirect enzyme-linked immunosorbent assay (ELISA) was used to detect IgG class-specific antibodies to avian infectious bronchitis virus (IBV) in chickens. The technique detected specific antibody with a high degree of sensitivity and was more sensitive than neutralisation or haemagglutination-inhibition methods of antibody assay. The possible application of the technique for diagnosis and research on IBV is discussed.

Procedures for the haemagglutination and the haemagglutination inhibition tests for avian infectious bronchitis virus

Various aspects of production, storage and stability of the haemagglutination (HA) activity of infectious bronchitis virus (IBV) were studied. From the results obtained, a standard procedure for the production of IBV, HA and the HA and haemagglutination inhibition (HI) tests is suggested. The main points of the suggested procedure are: (1) the virus should be concentrated but not purified; (2) the virus should be treated with phospho-lipase C type 1 (PLC), at a final concentration of one unit/ml, for two hours at 37 degrees C; (3) the virus should be stored at 4 degrees C after PLC treatment; (4) HA and HI test plates should be kept at 4 degrees C and read 45-60 min after the addition of chicken red blood cells. Using the recommended standard procedure the HA and HI tests for IBV were as reproducible as the HA and HI tests for Newcastle disease virus.

Immune response to monovalent and bivalent Newcastle disease and infectious bronchitis inactivated vaccines

Inactivated oil emulsion Newcastle disease (ND) and infectious bronchitis (IB) vaccines were prepared and evaluated in both monovalent and bivalent form. By using such vaccines as secondary boosters an enhanced immune response was produced for up to 10 weeks, at which time there was a high degree of resistance to challenge with IB virus in the bivalent vaccine group. This secondary response was most effective when preceded by a live combined ND/IB primary vaccine, which in itself did not stimulate a satisfactory antibody response. Revaccination with a bivalent inactivated vaccine containing the adjuvant BRL 5907 produced a secondary response significantly better than in the groups that received the bivalent vaccine only. When the mono- and bivalent inactivated vaccines were used as primary vaccines a poor immune response was illicited. However, revaccination with a bivalent inactivated vaccine significantly improved the response. An interesting observation was that when ND virus and IB virus were grown in the same embryonated eggs there was an increase in IB virus yield. When inactivated, and emulsified as a bivalent vaccine an enhanced immune response to IB virus was induced in the vaccinated chickens.

A serological survey for avian infectious bronchitis virus and Newcastle disease virus antibodies in backyard (free-range) village chickens in Mexico

The commercial flocks in Yucatan, Mexico are free of Newcastle disease virus (NDV) in its velogenic viscerotropic form, but little is known about the disease status of backyard poultry. A seroprevalence survey in 30 villages using haemagglutination inhibition (HI) tests for infectious bronchitis virus (IBV) and NDV antibodies was carried out from December 1997 to June 1998. The seroprevalences were 56.5% (95% CI 50-63%) for IBV and 2.2% (95% CI 0.5-3.8%) for NDV. All the villages had chickens that were positive for antibodies to IBV and nine of the villages had chickens that were positive for antibodies to NDV. This suggests that IBV may be responsible for a large proportion of the respiratory disease observed in backyard chickens in Yucatan. The implications of these findings are discussed, including the highly susceptible status of the backyard chickens in Yucatan to NDV and the possibility of this virus being one cause of the syndrome known as mortandad by the local people.

A novel protein polymorphism differentiates the California serotype of infectious bronchitis from other serotypes common to California

The California (Cal) serotype of infectious bronchitis virus (IBV) was isolated from layer flocks in southern California in the early 1980s. Since then, it has spread to the broiler-producing regions of central California, where it has been implicated in respiratory disease outbreaks in vaccinated flocks. Lack of a procedure for quickly identifying IBV serotypes in commercial chicken flocks has prevented the causal association of the IBV Cal serotype with respiratory disease outbreaks. A protein polymorphism has been identified in the matrix protein of the Cal serotype; it appears to be unique among other common serotypes of infectious bronchitis virus found in California. This polymorphism can be identified on western blots using raw or concentrated infectious allantoic fluid as the source material. Identification of the Cal serotype and of serotypes in the Mass and Conn groups can be performed rapidly using field samples from suspect flocks. The identification of this polymorphism provides an alternative method for the rapid identification of the Cal serotype of IBV.

Epitopes on the peplomer protein of infectious bronchitis virus strain M41 as defined by monoclonal antibodies

Sixteen monoclonal antibodies (Mcabs) were prepared against infectious bronchitis virus strain M41, all of them reacting with the peplomer protein. One of them, Mcab 13, was able to neutralize the virus and to inhibit hemagglutination. Competition binding assays allowed the definition of five epitopes, designated as A, B, C, D, and E, of which epitopes A and B are overlapping. Furthermore, the binding of Mcab 13 (epitope E) could be enhanced by the addition of Mcabs from group B, C, and D. A dot immunoblot assay was used to analyze the effect of denaturation on antibody recognition of the epitopes. Only the binding of Mcab 13 was affected, indicating that the epitope involved in neutralization and hemagglutination is conformation dependent. The epitopes A to D were highly conserved among IBV strains, while epitope E was specific for strains M41 and D3896. In this last strain, however, this epitope was not involved in neutralization.

Some field observations on the antibody response to avian infectious bronchitis on Auckland layer farms

Layer flocks on four Auckland poultry farms were monitored monthly for Infectious Bronchitis (IB) antibody levels, using the haemagglutination inhibition test. The same birds were bled each month and antibody levels compared with egg production. The results showed that IB vaccination at 4(1/2) and 14(1/2) weeks using the live, attenuated, New Zealand A strain virus, protected layers from IB infection on a farm with good management techniques but vaccination on another commercial farm gave less then ideal protection due possibly to intercurrent disease. Also antibody levels in naturally infected layers responded more vigorously when exposed to the field strain, compared with the response in vaccinated birds.