To identify novel antigens with immunoglobulin G2 (IgG2) specificity and immunostimulant properties for bovine Th1 cells, humoral and cellular responses were studied in cattle inoculated with initial bodies from a Mexican isolate of Anaplasma marginale and challenged with a heterologous strain. Analysis of post-immunization sera by ELISA and assaying of in vitro cellular responses in peripheral blood mononuclear cells (PBMCs) cultured in the presence of protein extracts from three Anaplasma marginale strains showed positive values of optical density ELISA readings and stimulation indices in the immunized but not control cattle. Post-immunization and post-challenge sera recognized in Western blots several proteins with molecular weights ranging from 15 to 209 kDa, twelve of which were recognized by IgG2 in the three Anaplasma marginale strains. Seven of these are novel and have not been previously reported for their IgG2 specificity; three are confirmed to be major surface proteins (MSP-1a, MSP-2, and MSP-5); and the others correspond to other well-studied MSPs but were not confirmed. Partially purified fractions of protein extracts of the Mex-17 strain were tested against PBMCs cultured in vitro. One out of the seven novel proteins induced detectable lymphoproliferation (LP) of PBMCs, and interferon-gamma was detected in supernatants of PBMC cultured in the presence of two protein fractions, including the one that caused LP. It is concluded that novel antigens, particularly the 28-kDa protein, played an additional role in the protection of immunized cattle and should be considered vaccine candidates after in vivo immunization experiments are concluded.

Objective: to determine the reaction of 53 lines and three varieties of black bean (Phaseolus vulgaris L.) to inoculation with Uromyces appendiculatus and Colletotrichum lindemuthianum, to identify genotypes resistant to rust and anthracnose.Design/methodology/approach: 10 seedlings of each genotype were inoculated in the greenhouse with a suspension of U. appendiculatus uredospores and another 10 with a suspension of C. lindemuthianum conidia. At 14 days after inoculation, the reaction of the genotypes to rust was evaluated with a severity scale of 1 to 6, and to anthracnose, with ascale of 0 to 4. The data were analyzed in a completely randomized design with 10 replications per treatment and LSD at 0.05 was applied for the separation of averages.Results: 41 genotypes showed a hypersensitivity reaction to rust, of which 25 had a reaction value of 2.0, statistically lower than those of controls. In turn, 45 genotypes were resistant to anthracnose, of which 18 had a value of 1.0, statistically similar to that of Negro Jamapa and lower than those of the rest of the genotypes.Study limitations/implications: due to the diversity of races of both pathogens, the genotypes were inoculated with monopustular isolates of the principal races of U. appendiculatus and with monosporic cultures of C. lindemuthianum, which occur in the bean crops of Veracruz and Chiapas.Findings/conclusions: 25 lines resistant to rust and 18 to anthracnose were identified, which stood out for presenting the least damage from these diseases.

Anaplasma marginale Yucatan strain was found to have low virulence in cattle. We studied the virulence of this isolate by experimental inoculation of 113 susceptible cattle at increasing doses, after which only one animal required treatment for clinical disease. Subsequently, 104 cattle received a live vaccine of this strain by inoculation, which induced immunoprotection after heterologous challenged exposure with a different A. marginale isolate. In this study 14% of the immunized cattle required treatment as compared with the control nonimmunized cattle, in which 56% required treatment. The A. marginale vaccine strains used for the immunization studies had MSP1a variable regions that were different from those used for the challenge exposure.

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