2 results
Immunity in experimentally induced enzootic pneumonia of pigs
- R. F. W. Goodwin, Ruth G. Hodgson, P. Whittlestone, Rosemary L. Woodhams
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- Journal:
- Journal of Hygiene / Volume 67 / Issue 2 / June 1969
- Published online by Cambridge University Press:
- 15 May 2009, pp. 193-208
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Hysterectomy-produced, colostrum-deprived pigs, reared in special isolation accommodation, were infected with enzootic pneumonia and later challenged with the same strain of the disease. Both the original infections and the subsequent challenges were made with intranasal inoculations of suspensions of ground pneumonic lung, but there was no evidence to suggest that any mycoplasma other than the J strain of Mycoplasma suipneumoniae was involved.
Pigs that had recovered from the disease were strongly immune to challenge, in that they developed virtually no lung lesions when inoculated with lung suspensions that produced extensive lesions of enzootic pneumonia in control animals. This was the case, even when the pigs were as young as 16 days old when first infected and were not challenged until up to 60 weeks later.
Sera from these pigs taken before infection, about 2–3 weeks after infection, at various times after natural recovery, and before and after challenge were examined using the metabolic-inhibition test, the indirect-haemagglutination test and the complement-fixation test.
The metabolic-inhibition test proved of little value, because non-specific inhibitory substances were present in the sera of some pigs both before and after infection: these substances inhibited the growth of Mycoplasma hyorhinis, Mycoplasma pneumoniae and Mycoplasma gallisepticum as effectively as M. suipneumoniae. Sometimes the non-specific inhibition was reduced by heating the sera at 56° C. for 30 min., but at other times it was not, which suggests that at least two types of non-specific inhibitors were present.
Apart from one pig, all the sera that were expected to be negative for antibodies against M. suipneumoniae proved to be so by the indirect-haemagglutination test. Titres of less than 1/5 were obtained in this test using the sera from pigs killed 12–22 days after infection, but high titres were obtained 16–60 weeks after infection. It was not possible to say whether these titres correlated with immunity.
All the pre-infection sera when examined by the complement-fixation test had titres of less than 1/10, but by 12–22 days after infection over half the serum samples had titres of 1/40 or more, and titres of 1/80–1/640 were obtained at 4 and 9 months after infection. There was some evidence to show that these titres declined more rapidly than the titres obtained in the indirect-haemagglutination test; for they were very low at 60 weeks after infection, at which time the indirect-haemagglutination titres were still high.
It seemed, therefore, that these two serological tests were measuring different aspects of the post-infection response. Also, because the complement-fixation titres were very low in two pigs that were shown to be powerfully immune, these titres did not appear to correlate with immunity.
Our work with the metabolic-inhibition test and the complement-fixation test has benefited from discussions with Dr D. Taylor-Robinson and Mr A. S. Wallis, respectively. We are grateful to Drs H. P. Chu, R. H. Leach and D. Taylor-Robinson for the reference sera and the culture mentioned in the text. Most of the expenses of this work, including the salary of two of the authors (R. G.H. and R.L.W.), were met by a grant from the Agricultural Research Council.
Some experiments relating to artificial immunity in enzootic pneumonia of pigs
- R. F. W. Goodwin, Ruth G. Hodgson, P. Whittlestone, Rosemary L. Woodhams
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- Journal:
- Journal of Hygiene / Volume 67 / Issue 3 / September 1969
- Published online by Cambridge University Press:
- 15 May 2009, pp. 465-476
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Hysterectomy-produced, colostrum-deprived pigs were injected twice with formalinized antigen prepared from the J strain of Mycoplasma suipneumoniae; the first injection was with Freund's adjuvant and the second injection without adjuvant. The immunity of these animals was tested by inoculating them intranasally with different doses of lung suspension prepared from cases of enzootic pneumonia. Two of the pigs were not killed shortly after infection, but were kept and challenged with enzootic pneumonia in order to compare the serology of experimentally-injected animals with the serology of the immune state following the experimentally-induced disease.
In a second main experiment, a pregnant sow was injected twice with nonformalinized antigen without adjuvant, and her litter was subsequently exposed to the disease at 7 days of age after suckling naturally from birth.
There was no evidence to suggest that the injections had protected the pigs in the first experiment against a high dose of infection, but they may have given some protection against low doses. The piglets suckled by the injected sow were not protected against two different doses of infection.
Serum samples taken at different stages were examined by the metabolic inhibition (MI) test, the indirect-haemagglutination (IHA) test, the complement fixation (CF) test and the gel-diffusion precipitin test, using M. suipneumoniae as antigen.
Serum samples taken before injection in the first experiment were all negative in the MI test and they became positive after the injections of antigen. However, 1 the highest MI titres obtained were not associated with obvious immunity; nor was the development of true immunity after experimental infection associated with a change in MI titre.
In the first experiment, substantial IHA titres (over 20,000) were recorded by 14 days after the second injection of antigen. Again, there was no correlation between the IHA titres and the area of pneumonia following experimental infection. In the sow experiment, IHA titres developed after the first injection and increased after the second; a high IHA titre occurred in the colostrum and titres of 320 or more were present in the piglets 7 days after birth.
The CF titres appeared earlier than the IHA titres but did not increase so markedly thereafter. Once more, there was no correlation between the titre before infection and the area of pneumonia afterwards.
In the gel-diffusion test, precipitins were demonstrated in all the post-injection serum samples tested, most of the samples being positive after the first injection. Precipitins were also demonstrated in the colostrum of the injected sow and in her uninjected litter at 7 days of age.
From these experiments it was concluded that, as judged by the development of pneumonic lesions and in marked contrast to the known immunizing effect of the disease itself, injections of antigen given in this manner had little or no protective effect against the dose levels of infection used. Nevertheless, the titres obtained in the MI, IHA and CF tests were comparable with those obtained earlier in pigs that were strongly immune, which provides further evidence for the suggestion that these tests do not measure protective immunity.
Miss Elaine Repworth provided technical assistance. Most of the expenses of this work, including the salary of two of the authors (R. G. H. and R. L. W.) were met by a grant from the Agricultural Research Council.