Further studies on caprine and ovine mycoplasmas related toMycoplasma mycoidessubsp.mycoides

Abstract

Nine caprine and ovine mycoplasma strains, said to be indistinguishable serologically from Mycoplasma mycoides subsp. mycoides (the causative organism of contagious bovine pleuropneumonia; CBPP) were examined in mice by (1) a mycoplasmaemia test, and (2) a cross-protection test. Of the nine strains, two from goats belonged to a small colony (SC) type; four caprine and three ovine strains belonged to a large colony (LC) type.The two SC strains - like a single SC strain examined in an earlier study - were indistinguishable from genuine M. mycoides subsp. mycoides as isolated from CBPP. They produced mycoplasmaemia readily. In a cross-protection test, the two SC strains and a CBPP strain immunized completely against each other.Of the seven LC strains, six - like six LC strains examined in an earlier study - were easily distinguished from genuine M. mycoides subsp. mycoides; except for one that was not tested, all were shown to lack the ability to produce mycoplasmaemia readily. In cross-protection tests all six strains immunized partially but not completely against a CBPP strain.The seventh LC strain (Mankefår 2833) was exceptional: it produced mycoplasmaemia readily, resembling the SC strains in this respect. Like other LC strains, in cross-protection tests it protected only partially against a CBPP strain. Strain Mankefår 2833 was isolated in ca. 1965 by Brack from a Barbary sheep (Ammotragus lervia) in a German zoo.The ability of Mankefår 2833 to produce mycoplasmaemia enabled it to be used as a challenge strain in cross-protection tests. For the purpose of such tests the collection of nine mycoplasma strains referred to above was augmented with six LC strains from an earlier study. Partial but not complete protection against Mankefår 2833 was produced by two caprine SC strains, one CBPP strain, and nine LC strains. Three further LC strains gave protection that may have been as strong as that produced by the homologous strain, but confirmatory experiments are needed. A strain of M. mycoides subsp. capri gave no protection against Mankefår 2833.

Observations on the antigenic differences between the so-called SC and LC strains of Mycoplasma mycoides subsp. mycoides

“…Despite the use of multiple doses, six of the LC vaccines failed to immunize as effectively as vaccine prepared from the challenge strain (P < 0 05). Because of the large challenge dose several of the G. R. SMITH AND JANET C. OLIPHANT Antigens of Mycoplasma mycoides 441 six vaccines appeared to give no immunity but, as already stated, earlier work (Hooker et al 1979;Smith et al 1980) had shown all the LC strains used in this study to be capable of immunizing partially against challenge with strain Blenheim. The results obtained with the other seven LC vaccines were not significantly different from that obtained with homologous vaccine; had the challenge dose been higher it is possible that further differences might have emerged.…”

“…For full details of all strains, including the method of cloning, see Smith & Oliphant (1981). A single dose of heat-killed vaccine prepared from each of the 13 LC strains had been shown earlier to immunize mice partially but not completely against challenge with strain Blenheim (Hooker et al 1979;Smith et al 1980). …”

“…Cross-protection tests in mice have shown that single doses of killed vaccines prepared from LC strains give only partial immunity against challenge with SC strains, whereas the immunity given by SC-strain vaccine against challenge with any SC strain is virtually complete (Hooker et al 1979;Smith, Hooker & Milligan, 1980). The LC and SC strains must, therefore, differ to some extent in their protective-antigen content; but it is not known whether the difference is qualitative, or merely quantitative.…”

Immunogenic variation among the so-called LC strains of Mycoplasma mycoides subspecies mycoides

“…The caprine SC strains, of which few have been isolated, are thought to be identical with CBPP strains. The caprine LC isolates, of which there are many, are indistinguishable by in vitro serological tests from SC (including CBPP) strains; they are, however, distinguishable on the basis of proteolysis and heat-resistance (Cottew & Yeats, 1978), sorbitol fermentation and streptomycin sensitivity (Smith & Oliphant, 1982), and mycoplasmaemia and cross-immunity tests in mice (Hooker, Smith & Milligan, 1979;Smith, Hooker & Milligan, 1980;Smith & Oliphant, 1981 a, b).…”

“…On intraperitoneal inoculation a symptomless mycoplasmaemia is produced readily in mice by SC strains but much less readily by the LC variety -with the single known exception of Mankefar 2833 (Smith et al 1980), a strain that has unusually robust growth properties (Smith & Oliphant, 1982). Cross-immunity tests are based on the ability of heterologous-strain vaccines to prevent the development of mycoplasmaemia after intraperitoneal challenge.…”