Adenovirus Vector-Induced CD8⁺ T Effector Memory Cell Differentiation and Recirculation, But Not Proliferation, Are Important for Protective Immunity Against Experimental Trypanosoma cruzi Infection

Abstract

Heterologous prime-boost vaccination using plasmid DNA followed by replication-defective adenovirus vector generates a large number of specific CD8⁺ T effector memory (TEM) cells that provide long-term immunity against a variety of pathogens. In the present study, we initially characterized the frequency, phenotype, and function of these T cells in vaccinated mice that were subjected to infectious challenge with the human protozoan parasite Trypanosoma cruzi. We observed that the frequency of the specific CD8⁺ T cells in the spleens of the vaccinated mice increased after challenge. Specific TEM cells differentiated into cells with a KLRG1(High) CD27(Low) CD43(Low) CD183(Low)T-bet(High) Eomes(Low) phenotype and capable to produce simultaneously the antiparasitic mediators IFNγ and TNF. Using the gzmBCreERT2/ROSA26EYFP transgenic mouse line, in which the cells that express Granzyme B after immunization, are indelibly labeled with enhanced yellow fluorescent protein, we confirmed that CD8⁺ T cells present after challenge were indeed TEM cells that had been induced by vaccination. Subsequently, we observed that the in vivo increase in the frequency of the specific CD8⁺ T cells was not because of an anamnestic immune response. Most importantly, after challenge, the increase in the frequency of specific cells and the protective immunity they mediate were insensitive to treatment with the cytostatic toxic agent hydroxyurea. We have previously described that the administration of the drug FTY720, which reduces lymphocyte recirculation, severely impairs protective immunity, and our evidence supports the model that when large amounts of antigen-experienced CD8⁺ TEM cells are present after heterologous prime-boost vaccination, differentiation, and recirculation, rather than proliferation, are key for the resultant protective immunity.

Inhibitory Receptor Expression on CD8+ T Cells Is Linked to Functional Responses against Trypanosoma cruzi Antigens in Chronic Chagasic Patients

“…Long-term nonprogressor HIV patients show higher frequencies of polyfunctional HIV-specific CD8 + T cells compared with progressor HIV patients (51), and both polyfunctional CD4 + and CD8 + T cells have been associated with an enhanced control of HIV replication (79). Even more, polyfunctional CD8 + T cells can provide protective immunity in vaccination studies against experimental T. cruzi infection (80)(81)(82). In Chagas disease, children with short-term T. cruzi infections exhibit a higher frequency of polyfunctional T cells in comparison with adults with long-term infections (83).…”

CD8+T Cell-Mediated Immunity duringTrypanosoma cruziInfection: A Path for Vaccine Development?

“…We observed that specific TEM cells differentiated into cells with a KLRG1 High CD27 Low CD43 Low CD183 Low T-bet High Eomes Low phenotype and were capable of simultaneously producing the antiparasitic mediators IFN- γ and TNF- α . Subsequently, we observed that the specific CD8 + T cells did not participate in a strong anamnestic immune response, and the protective immunity they mediated was insensitive to treatment with the cytostatic toxic agent hydroxyurea, which drastically reduced their proliferation [92]. …”

A PartialE3Deletion in Replication-Defective Adenoviral Vectors Allows for Stable Expression of Potentially Toxic Transgene Products

“…1,2 They trigger a potent inflammatory response, 3,4 which initiates adaptive immune responses to the transgene product and the antigens of the Ad vector. 5 This has led to the development of different Ad serotypes as vaccine carriers for a plethora of antigens derived from viruses, 6-10 bacteria, 11,12 parasites, 13,14 or tumor cells, [15][16][17] which have consistently induced potent and sustained B and T cell responses to the transgene products.…”