We declare no confl ict of interest.
ABSTRACTVaccinia virus is responsible for a zoonosis that usually affects cattle and human beings in Brazil. The initial clinical signs of the infection are focal red skin areas, fever, and general symptoms similar to those of a cold. Then, pustules and ulcerated lesions surrounded by edema and erythema follow, as well as local lymphadenopathy that can last for weeks. Cure and healing of the lesions occur over several weeks, leaving a typical scar in the skin of people and animals affected. The infection defi nitive diagnosis is made through morphological characterization of the virus by use of electron microscopy, followed by PCR for specifi c viral genes. Since 1963, circulating orthopoxviruses in infectious outbreaks in several regions of Brazil have been reported. Later, the etiological agent of those infections was characterized as samples of Vaccinia virus. In addition, the widespread use of those viruses in research laboratories and mass vaccination of militaries have contributed to increase the cases of those infections worldwide. Thus, several epidemiological and clinical studies are required, as well as studies of viral immunology, public health, and economic impact, because little is known about those Vaccinia virus outbreaks in Brazil.
The present study evaluates the immune response of memory CD4(+) and CD8(+) T cells from patients following a natural Vaccinia virus (VACV) infection. A total of 42 individuals were involved in the study being: 22 previously infected individuals (vaccinated or not against smallpox) and 20 non-infected individuals (vaccinated or not). A short-term in vitro stimulation with UV-inactivated VACV of whole blood cells was performed. Our study showed that previously infected individuals have a lower percentage of CD4(+) T cells expressing lymph-node homing receptors (CD4(+)CD62L(+)CCR7(+)) and higher percentage of memory CD4(+) T cells subsets (CD4(+)CD45RO(High)) when compared with non-infected subjects, after in vitro viral stimulation. We also showed that infected individuals presented higher percentages of CD4(+) and CD8(+) memory T lymphocytes expressing IFN-γ when compared to non-infected individuals. We verified that the percentage of CD4(+) and CD8(+) T memory cells expressing TNF-α was higher in infected and non-infected vaccinated subjects when compared with non-infected unvaccinated individual. We also observed that previously infected individuals have higher percentages of CD8(+) T cells expressing lymph-node homing receptors (CCR7(+) and CD62L(+)) and that the memory T cells expressing IFN-γ and TNF-α were at higher percentages in the whole blood cells from infected and non-infected vaccinated individuals, when compared to unvaccinated non-infected subjects. Thus, our findings suggest that CD4(+) and CD8(+) T cells are involved in the immune memory response against Vaccinia virus natural infection.
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