Solid-phase micro-radioimmunoassay to measure immunoglobulin class-specific antibody to Mycoplasma pulmonis

La gestion sanitaire des élevages de rongeurs utilisés en recherche biomédicale: III. Le programme de surveillance des infections

HEALTH SURVEILLANCE PROGRAM: This article outlines the principal components of quality control of laboratory rodents.

Isotype commitment of B cells and dissemination of the primed state after mucosal stimulation with Mycoplasma pulmonis

Live Mycoplasma pulmonis organisms were used to examine the immune response in the bronchus-associated lymphoid tissue after primary and secondary challenge with M. pulmonis, to study the dissemination of the primed state to distal tissues (i.e., spleen, peripheral blood, and Peyer's patches), and to determine whether the chronic antigenic stimulation accompanying infection influences the isotype potential and commitment of the primed B cells recovered from the various tissues. We have shown that exposure to M. pulmonis by a variety of routes results in a generalized rise in frequency of T-dependent, antigen-sensitive B cells in all lymphoid tissues. The route of secondary exposure to M. pulmonis was found to markedly increase the frequency of M. pulmonis-specific B cells in the bronchus-associated lymphoid tissue relative to that in the Peyer's patches after intraduodenal but not intratracheal challenge. A substantial rise in the number of M. pulmonis-sensitive B cells in the peripheral blood suggests that the dissemination of the primed state, at least in part, is due to B-cell migration via lymph and blood from local sites exposed to M. pulmonis. The majority of T-dependent clones generated by M. pulmonis-specific B cells secrete exclusively immunoglobulin G1 (IgG1). We have demonstrated that the exaggerated IgG1 response was not due to the accompanying viable donor T cells in the inoculum. The predominance of IgG1 was also demonstrated in clones from the bronchus-associated lymphoid tissue of athymic BALB/c mice that were primed with M. pulmonis. Thus, we can infer that functional T cells are not required for the development of specific B cells with the potential for IgG1 expression at the time of in vivo priming. When anti-trinitrophenyl- and anti-M. pulmonis-specific clones were generated in the same splenic fragment cultures stimulated by trinitrophenylated M. pulmonis, only the M. pulmonis-specific clones showed exaggerated IgG1 expression. Therefore, we conclude that the exaggerated IgG1 response accompanying M. pulmonis infection of euthymic mice seems to be dependent, at least in part, on an intrinsic property of the B cells that develop during this antigenic stimulation.

A comparison of three vaccines against respiratory syncytial virus in calves

An inactivated vaccine against respiratory syncytial virus (RSV) was compared with two live vaccines. The inactivated (GC) vaccine consisted of glutaraldehyde-fixed bovine nasal mucosa cells persistently infected with RSV and emulsified with oil adjuvant. The live vaccines were a modified virus (MV) derived from a bovine strain of RSV and a temperature-sensitive mutant (ts-1) derived from a human strain. The GC vaccine was inoculated subcutaneously into 12 calves and the live vaccines intramuscularly into eight calves each. Nine unvaccinated calves acted as controls. The vaccines were administered in two doses 3 weeks apart and all calves were challenged intranasally with 2 X 10(7) p.f.u. of bovine RSV 3 weeks after the second dose. At the time of challenge calves given GC, MV and ts-1 vaccines had mean serum neutralizing antibody titres of 25, 19 and 2 respectively; mean titres of IgG1 antibody by radioimmunoassay were log10 4.5, 1.3 and 2.6 respectively and mean zone areas by single radial haemolysis (SRH) were 107, 27 and 36 mm2 respectively. Eleven of 12 calves given GC vaccine were completely protected against challenge but all control animals and those given the two live vaccines were infected. The mean peak titre of virus in nasal swabs of control calves was 3.0 log10 p.f.u./ml and the mean duration of virus shedding was 6.8 days. Both these parameters were significantly reduced in animals given MV and ts-1 vaccines: mean peak titres were 2.1 and 2.4 log10 p.f.u./ml and mean duration of shedding was 3.4 and 3.3 days respectively. Thus, protection correlated better with RSV antibody detected by radioimmunoassay and SRH than with neutralizing antibody. These results are discussed in relation to the possible mechanism by which protection was mediated.

Monoclonal antibodies protect against respiratory syncytial virus infection in mice

Twenty-five monoclonal antibodies (Mab) to respiratory syncytial virus (RSV) and two to hepatitis B virus were inoculated intravenously into mice. Twenty-four hours later the mice were challenged intranasally with RSV. Eleven of 14 Mab against fusion protein and four out of six Mab against a larger glycoprotein (GP84) significantly reduced the titre of RSV in the lungs when mice were killed 5 days later. Five Mab against three other RSV proteins and two Mab against hepatitis B virus had no significant effect on RSV infection. These results indicated that serum IgG against one epitope on the fusion protein and another on the larger glycoprotein (GP84) will completely protect mice against challenge. These epitopes are primary candidates for an RSV vaccine produced by techniques of gene cloning and peptide synthesis.

Infection of gnotobiotic calves with a bovine and human isolate of respiratory syncytial virus. Modification of the response by dexamethasone

A bovine and a human strain of RSV both adapted to bovine cell culture, have been inoculated separately into 13 and 7 gnotobiotic calves respectively by 3 different methods. Both strains infected calves and showed similar growth patterns. Virus was recovered from the nasopharynx between one and 11 days with peak titres between 3 and 8 days following inoculation. With the exception of 4 calves treated with dexamethasone no clinical signs and only minimal macroscopic lesions of the lung were induced, which histologically comprised a mononuclear infiltration of alveolar walls and of the peribronchiolar tissue. The serological response to both strains was similar. Antibody was detected by virus neutralisation or single radial haemolysis from 12 days after inoculation. Specific anti-RSV IgM was detected from 10 days and IgG from 16 days after inoculation. Treatment with dexamethasone (0.5 mgm/Kg daily for 10 days) enhanced lung lesions produced by the bovine strain, prolonged the period of virus shedding and increased peak titres. The specific IgM response was suppressed.

Experimental pneumonia in gnotobiotic calves produced by respiratory syncytial virus

A bovine isolate of respiratory syncytial virus (RSV), when inoculated intranasally into eight gnotobiotic calves produced significant macroscopic lesions of the lung (2-25% consolidation) but failed to produce any clinical signs of disease. The microscopic lesions comprised proliferative and exudative bronchiolitis with accompanying alveolar collapse and infiltration by mononuclear cells of the peribronchiolar tissue and alveolar walls. Virus was recovered from the nasopharynx between days 2 and 11 after infection with peak titres between days 4 and 7. Demonstration of viral antigen by immunofluorescence in nasopharyngeal cells followed a similar detection pattern. Virus was recovered from lung or detected by immunofluorescence in the bronchiolar epithelium up to 11 days following inoculation. A serological response to RSV was demonstrated both by virus neutralization and single radial haemolysis (SRH) tests, in serum of calves from 11 days following inoculation. Specific anti-RSV IgM was detected from 9 days following infection. It is suggested that the close resemblance between the experimental disease in calves and the pathology of acute bronchiolitis in children make cattle a particularly relevant model for the human disease.

Comparison of sensitivities of ELISA and radioimmunoassay for detection of class-specific antibody in mouse serum

The limits of detection of IgG1 antibody in a standard mouse antiserum by a single antiglobulin enzyme-linked immunosorbent assay (ELISA) and 2 amplified systems, a double antiglobulin ELISA and a double antiglobulin radioimmunoassay (RIA), were compared in microtitration plates with the same antigen preparation and antisera. Compared with the single antiglobulin ELISA, both amplified assays demonstrated a 64-fold increase in sensitivity for the detection of antibody at high dilutions of standard antiserum. It is concluded that the amplified ELISA offers a safer assay than the amplified RIA and of equal sensitivity for comparable consumption of antisera.

Protection of mice against Mycoplasma pulmonis infection using purified mouse immunoglobulins: comparison between protective effect and biological properties of immunoglobulin classes

Purified mouse immunoglobulins with specific activity against Mycoplasma pulmonis were examined for their ability to protect mice against intranasal (i.n.) infection with this organism. The survival of mycoplasmas in the respiratory tract of mice inoculated i.n. with M. pulmonis mixed with either IgG1, IgGa, IgG2b or IgA antibodies was less than that seen in control animals inoculated with mycoplasmas mixed with normal mouse serum. The ways in which the immunoglobulin fractions could have mediated resistance were examined in vitro. IgG1, IgG2a and IgG2b antibody fractions killed M. pulmonis in the presence of guinea-pig complement, and also promoted the phagocytosis of M. pulmonis by mouse lung macrophages. In contrast, IgA antibody did not appear to be either mycoplasmacidal or opsonic.

Class-specific antibody responses to Mycoplasma pulmonis in sera and lungs of infected and vaccinated mice

Class-specific antibodies were measured by a solid-phase microradioimmunoassay in the sera and lung washings of mice after intranasal or intravenous inoculation with live Mycoplasma pulmonis and after systemic, intranasal, or combined vaccination with Formalin-inactivated mycoplasmas. After intranasal or intravenous inoculation with live organisms, serum antibodies were first detected in immunoglobulin M (IgM) followed by IgG2, IgG1, and IgA classes, but significant levels of IgA developed only in those mice inoculated intranasally. The appearance of antibodies in lung washings was later than in serum, but again these were predominantly IgG2 and IgG1. After inoculation with killed organisms, serum antibodies were predominantly IgG1, although IgG2, IgM, and, in intranasally vaccinated mice, IgA were also present. Only IgG1 was detected in lung washings from mice vaccinated systemically, but IgA and IgG2 were present in addition in animals vaccinated intranasally. Immunofluorescence studies indicated that some antibody in lung washings from the latter group of animals was produced locally. A comparison of the levels of various class-specific antibodies and resistance to intranasal challenge suggested that local antibody of any immunoglobulin class is capable of mediating resistance in the lungs to M. pulmonis infection.