Quantitative analysis of protective T cell immunity against brucellosis
Authors: Ponomarenko D. G. , Kostyuchenko M. V. , Rakitina E. L. , Logvinenko O. V. , Khachaturova A. A. , Lukashevich D. E. , Kurcheva S. A. , Rusanova D. V. , Kulichenko A. N. 
Published: February 2024

The results of study relationship between antigen reactivity of T-lymphocyte population under ex vivo conditions and the intensity of protective post-vaccination immunity to causative agent of brucellosis are presented. Тaking into account the peculiarities of immunopathogenesis brucellosis and prevailing role of adaptive T-cell immunity to protect against the causative agent of infection, possibility predictive evaluation of protective immunity against brucellosis using CAST-tests is considered as the most important aspect of brucellosis problems. There is an obvious need for an ex vivo correlation analysis of the activity of antigen stimulation of T cells and the intensity of protective immunity formed after vaccination. A close direct proportional relationship was established between the number of live microbial cells Brucella abortus 19BA vaccine strain administered and increase in ex vivo CD3-cell activation. A close correlation was revealed between ex vivo value of antigen-induced stimulation CD3-lymphocytes and level of post-vaccination immunological protection against brucellosis infection. It has been shown that in biomodels vaccinated against brucellosis with a T-lymphocyte stimulation coefficient of 50% or more (according to intensity of antigen-induced ex vivo expression CD25), 100% protection from the development of brucellosis infection after infection with Brucella melitensis at a dose of 1 × 103 live microbial cells are provided. At the same time, there was a lack of a close correlation between an increase in the dose of brucella vaccine strain administered to biomodels and a change in geometric mean antibody titer, presence of a weakly pronounced relationship between level of agglutinins and immunological protection of biomodels from development brucellosis infection and indicators bacterial contamination body.Based on results of study, it was demonstrated that it is possible to quantify the formation and protective activity of T-cell immunity to causative agent of brucellosis based on analysis of level antigen reactivity of CD3-lymphocytes ex vivo. The data obtained and described methodological approach can be used as a predictive criterion in assessing protective level of cellular immunity to causative agent of brucellosis in vaccinated or recovering patients, as well as in order to analyze effectiveness of specific prophylaxis brucellosis and study immunogenicity and protective properties candidate for brucellosis vWe present the results of studies related to antigen reactivity of T lymphocyte population under ex vivo conditions and the intensity of protective post-vaccination immunity to causative agent of brucellosis. Due to peculiarities of immunopathogenesis in brucellosis infection and prevailing role of adaptive T cell immunity for protection against the causative agent of infection, a predictive evaluation of protective immunity against brucellosis using CAST-tests is considered the most important issue in the field. There is an obvious need for ex vivo analysis of correlations between the activity of antigen stimulation of T cells, and the intensity of protective immunity raised after vaccination. A close direct relationship was established between the number of live microbial cells of Brucella abortus 19BA vaccine strain administered, and increase in ex vivo CD3 cell activation. A close correlation (r = -0.841 ÷ -0.966, R2 = 0.708 ÷ 0.969) was revealed between ex vivo values of antigeninduced stimulation of CD3 lymphocytes, and the levels of post-vaccination immunological protection against brucellosis infection. We have shown that, in biomodels vaccinated against brucellosis with a T lymphocyte stimulation coefficient of 50% or more (according to intensity of antigen-induced ex vivo CD25 expression), 100% protection against brucellosis infection was achieved after contamination with Brucella melitensis at a dose of 1×103 live microbial cells. At the same time, a lack of a close correlation was noted between an increased dose of Brucella vaccine strain administered to biomodels, and a change in geometric mean of antibody titer (R2 = 0.357÷0.404), along with a weak relationship between the levels of agglutinins and immunological protection of biomodels from developing brucellosis infection and indices of in vivo bacterial contamination.These results suggest an opportunity to quantify development and protective activity of T cell immunity to the causal agent of brucellosis based ex vivo levels of antigen reactivity of CD3 lymphocytes. A correlation analysis between the state of T cell antigen reactivity and immunological resistance to brucellosis infection indicated a high degree of closeness between these indices. The key influence on activity of protective immunity is exerted by the levels of antigen reactivity of T lymphocytes, whereas the quotient of antigenic stimulation in CD3+CD25+ population may be considered the most informative index of immune protective activity. The data obtained and the described methodology may be used as a predictive criterion in assessing protective level of cellular immunity to causative agent of brucellosis in vaccinated or recovering patients, testing the efficiency of specific prophylaxis in brucellosis and studying immunogenicity and protective properties of candidate vaccines against brucellosis.