Protective Effect of Vaccines in Experimental Mycoplasma pneumoniae Disease

Abstract

The mechanisms of immunity to Mycoplasma pneumoniae were investigated by evaluating different vaccination procedures in an experimental animal model. Hamsters were immunized by intranasal inoculation of broth cultures or by parenteral injections of saline-suspended organisms. All vaccinees received a standardized intranasal challenge which produced pneumonia in 94% of controls. Intranasal immunization with virulent organisms produced a 71 % reduction in pneumonia. Subcutaneous and intraperitoneal inoculation of the same organisms yielded 56 and 61% reductions, respectively. Animals similarly immunized with an attenuated strain developed resistance to pneumonia only after intranasal infection. Serum antibody levels did not correlate with protection. Growth-inhibiting activity was demonstrated in bronchial washings of challenged animals, suggesting the development of local antibody in response to infection with M. pneumoniae. Crosschallenge studies were performed in animals vaccinated intranasally with virulent and avirulent variants of the same strain. The avirulent vaccine prevented pneumonia in animals challenged with homologous virulent organisms but not in those receiving an unrelated strain; the virulent vaccine provided protection to both homologous and heterologous challenge. These studies indicate that organism strain variation as well as vaccination technique are important determinants of the immune response to M. pneumoniae.on July 15, 2020 by guest http://iai.asm.org/ Downloaded from

Role of Humoral Antibodies in Resistance to Mycoplasma pneumoniae Pneumonia in Hamsters

“…Hamsters with a high serum antibody level produced by parenteral administration of killed M. pneumoniae vaccine did not show resistance to the experimental inoculation of M. pneumoniae (5), while animals previously infected with the organisms had a low serum antibody level but were resistant to reinfection (5)(6)(7). Hence those authors concluded that there was little correlation between serum antibody titer and protection against M. pneumoniae pneumonia in vaccinated hamsters.…”

Enhancement of Cytotoxicity of Active Macrophages by Mycoplasma: Role of Mycoplasma‐Associated Induction of Tumor Necrosis Factor‐α (TNF‐α) in Macrophages

“…One is that INF-a induced by mycoplasma-contamination in target cells might be responsible for enhancement of cytotoxic activity of macrophages and NK cells. The other is that TNF-a induced by pathogeneic mycoplasmas in human and animal, may play a role in resistance to mycoplasma infections in riz'o, through enhancement of cellular immune response (3,6) which might be responsible for protection of mycoplasma infection rather than humoral immunity in these mycoplasma infections (12). There have been several reports that mycoplasmas enhance the cytotoxic activity of macrophages and NK cells.…”

Immunological Responses of Hamsters in the Acquired Immune State to Mycoplasma pneumoniae Infection

“…hamsters previously infected with M. pneumoniae were found to be more resistant to pneumonia upon reinfection, even if they had low serum antibody titers (10,12,16). However, in our previous investigations, resistance to M. pneumoniae infection in hamsters corresponded to serum antibody titers in animals actively immunized with adjuvant vaccine (17) or adoptively immunized with serum preparations (17,18).…”

“…M. pneumoniae pneumonia responds satisfactorily to the appropriate antibiotics, but the organisms are not effectively eradicated from the respiratory tract (14,23). Efforts have been directed toward the development of a vaccine for prophylaxis (7,10,12,17,25).Resistance of humans to M. pneumoniae infection has been reported to be correlated directly with the presence of serum antibodies (7,20,22,28). In hamsters, a high level of serum antibody produced by parenteral vaccination with killed M. pneumoniae was not accompanied by protection (l 0) .…”

“…M. pneumoniae pneumonia responds satisfactorily to the appropriate antibiotics, but the organisms are not effectively eradicated from the respiratory tract (14,23). Efforts have been directed toward the development of a vaccine for prophylaxis (7,10,12,17,25).…”