The indirect fluorescent antibody test for the detection of circulating antibodies in bovine tuberculosis

Detection of Lassa Virus-Reactive IgG Antibodies in Wild Rodents: Validation of a Capture Enzyme-Linked Immunological Assay

The aim of this study was to evaluate the use of a capture enzyme-linked immunosorbent assay (ELISA) for the detection of LASV-reactive IgG antibodies in Mastomys rodents. The assay was used for laboratory-bred Mastomys rodents, as well as for animals caught in the wild in various regions of West Africa. The ELISA reached an accuracy of 97.1% in samples of known exposure, and a comparison to an immunofluorescence assay (IFA) revealed a very strong agreement between the ELISA and IFA results (Cohen’s kappa of 0.81). The agreement is valid in Nigeria, and in Guinea and Sierra Leone where the lineages II and IV are circulating, respectively. Altogether, these results indicate that this capture ELISA is suitable for LASV IgG serostatus determination in Mastomys rodents as an alternative to IFA. This assay will be a strong, accurate, and semi-quantitative alternative for rodent seroprevalence studies that does not depend on biosafety level 4 infrastructures, providing great benefits for ecology and epidemiology studies of Lassa fever, a disease listed on the Research and Development Blueprint of the WHO.

In vitro immunodiagnostic assays for bovine tuberculosis

The immune response to mycobacterial infections in cattle is predominantly cellular in nature and current diagnostic tests for M. bovis are based on the measurement of T cell responses. The low sensitivity of serological assays for tuberculosis is therefore not surprising and serological tests will at best be used to complement rather than replace cellular assays. The recently developed bovine interferon gamma (IFN-gamma) assay is a rapid (24 hour) and simple whole blood in vitro assay, which in Australian field trials was found to be significantly more sensitive than the intradermal tuberculin test for the diagnosis of bovine tuberculosis. The problem of false-positive reactions, due to the cross-reactive nature of the antigen preparations used, can largely be overcome by using a comparative assay in which an animal's IFN-gamma response to bovine PPD and avian PPD are compared. Although reasonably M. bovis specific proteins have been identified and characterised, their use in either serological or cellular diagnostic assays is likely to be restricted due to the genetic diversity of the bovine immune response to M. bovis infection.

Studies on the efficiency of absorbed bovine PPD in tuberculin and serological tests

The passive haemagglutination, enzyme-linked immunosorbent assay and indirect fluorescent antibody tests were applied to study the non-specific reactions in experimentally infected guinea pigs and tuberculin positive bovines. These cross-reactions were greatly decreased after absorption of either sera with avian PPD or bovine PPD antigen with anti-avian PPD serum. The use of both absorbed sera and antigen raised the specificity of PHA and ELISA to 100%. The use of absorbed sera rendered the IFA specific in 95%. The absorption has reduced the sensitivity of ELISA, IFA and PHA by 14, 27 and 29%, respectively.

Infectious bovine keratoconjunctivitis: seasonal variation in cultural, biochemical and immunoreactive properties of Moraxella bovis isolated from the eyes of cattle

The eyes of 20 young cattle were examined over an 18 month period in which 12 members of the group contracted infectious bovine keratoconjunctivitis (IBK). On each of 23 occasions cultural, biochemical and immunoreactive properties of up to 6 isolates of Moraxella bovis derived from each eye were determined. Relationships between the clinical response of eyes, phenotypic properties of M. bovis and annual variations in the level of solar ultraviolet radiation of 280 to 320 nm wavelength were examined. M. bovis was isolated from all IBK-affected and some unaffected eyes less than one month after the maximum annual level of the mean weekly UV radiation (2,840 mWh.m-2 X nm-1) was recorded. A high proportion of M. bovis from IBK lesions were simultaneously active in haemolysis, agar corrosion, gelatin liquefaction and litmus milk peptonisation. Some of these characteristics showed marked dissociation despite consistent reactivity in the fluorescent antibody test, which had a sensitivity and specificity of 95%. Fall in the mean weekly level of UV radiation below 1,438 mWh X m-2 X nm-1 in autumn was accompanied by healing of ulcers, persistent scar formation and a decline in the number of M. bovis isolated from affected eyes. A slower decline in the number of M. bovis isolated from apparently healthy eyes occurred in the winter and occasional fresh IBK lesions occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Serological responses in experimental bovine tuberculosis

Five two-year-old heifers were each inoculated intravenously with 0.02 mg M. bovis strain AN5. Clinical, haematological and microbiological observations were made during the course of the experiment and antibody levels were measured before and after infection by means of the indirect immunofluorescent antibody (IFA) and bentonite flocculation tests. All cattle developed M. bovis infection varying in severity from peracute tuberculous pneumonia resulting in death within 33 days to chronic progressive generalised tuberculosis. Only cattle developing peracute or acute forms of tuberculosis showed marked haematological changes characterised by leucopenia with lymphopenia. Bacteraemia was detected in the two cattle with peracute tuberculosis 22 days after infection. Anti-mycobacterial antibody was detected after infection in all cattle but fluctuated markedly during the course of the disease. Of a total of 61 serum samples examined from all cattle after inoculation with M. bovis, only 38 were positive to the IFA test and 30 to the bentonite flocculation test. Only 18 were positive to both tests at any one time. IgM was the predominant type of anti-mycobacterial antibody detected by the IFA test and this was found to cross-react with M. avium in almost every sample.