Characterization of anamnestic T-cell responses induced by conventional vaccines against contagious bovine pleuropneumonia.

A better understanding of how T1 vaccination confers immunity would facilitate the rational design of improved vaccines against contagious bovine pleuropneumonia (CBPP). We show here that mycoplasmas-induced recall proliferation and IFN-γ responses are detected in cattle that received multiple shots of T1 vaccines. These anamnestic responses were under the strict control of CD4(+) T lymphocytes. Moreover, CD62L expression indicated that both CD4(+) effector memory (Tem) and central memory (Tcm) T lymphocytes are elicited in these animals. Comparative analysis with data from cattle that completely recovered from CBPP infection revealed similar anamnestic T-cell responses albeit at a lower magnitude for T1-vaccinated animals, particularly in the Tcm compartment. In conclusion, we discuss how our current understanding of T-cell responses will contribute to ongoing efforts for the improvement of future CBPP vaccines.

Genotyping of Mycoplasma mycoides subsp. mycoides SC by multilocus sequence analysis allows molecular epidemiology of contagious bovine pleuropneumonia.

Mycoplasma mycoides subsp. mycoides SC (MmmSC) is the etiological agent of contagious bovine pleuropneumonia (CBPP). Although eradicated in most developed countries, the disease reappeared in Europe in the 1990s. This reappearance may have been caused either by importation from sub-Saharan Africa, where CBPP is still endemic, or by the reemergence of virulent strains in Europe, as suggested by earlier studies. A multilocus sequence analysis scheme has been developed to address this issue and, most importantly, to be able to monitor new epidemics. The alignment of the full genome sequence of the reference strain PG1 and the partial genome sequence of a pathogenic strain allowed the identification of polymorphic sites. Nineteen initial loci were selected within housekeeping genes, genes of unknown function and non coding sequences. The suitability of these loci for genotyping MmmSC strains was first tested on six strains of diverse geographic origin. The analyses showed that the published PG1 sequence contained a number of specific polymorphisms that were therefore of no use for molecular typing. Among the eight informative polymorphic loci finally selected, only one (ftsY) was positioned within a housekeeping gene. Three main groups and 31 different allelic profiles were identified among 51 strains and strain variants examined. Cluster analysis confirmed that European strains from the 1990s did not originate from Africa. It also showed a genetic link between a European strain isolated in 1967 and those found in southern Africa and Australia. This was in agreement with historical data showing that CBPP was introduced in these regions during colonisation in the 19th century.

Analysis of cellular responses to Mycoplasma mycoides subsp. mycoides small colony biotype associated with control of contagious bovine pleuropneumonia.

A better understanding of protective immune memory against contagious bovine pleuropneumonia (CBPP) is needed in order to facilitate the development of safer vaccines based on selected components of the pathogen. For this purpose, cells collected from lymph nodes draining the lungs of Mycoplasma mycoides subsp. mycoides small colony biotype (MmmSC)-infected cattle were stimulated with the pathogen in vitro and evaluated concurrently for proliferation (CFSE based method), expression of activation, memory markers and cytokine production. Direct evidence is presented for a major contribution of CD4+ T cells to the vigorous proliferative and T1 biased cytokine recall responses observed in cattle that have recovered from infection but not in animals developing the acute form of the disease. Two different phenotypes of MmmSC-specific memory CD4 were observed based on CD62L expression and proliferative capacities. Furthermore, recall proliferation of B cells also occurred but was strictly dependent on the presence of CD4. The information provided in this study will facilitate the search for MmmSC antigens that have potential for the development of subunit vaccines against CBPP.