Effect of homeostatic T-cell proliferation in the vaccine responsiveness against influenza in elderly people.

BACKGROUND: Seasonal influenza virus infection is a significant cause of morbimortality in the elderly. However, there is poor vaccine efficacy in this population due to immunosenescence. We aimed to explore several homeostatic parameters in the elderly that could impact influenza vaccine responsiveness. METHODS: Subjects (> 60 years old) who were vaccinated against influenza virus were included, and the vaccine response was measured by a haemagglutination inhibition (HAI) test. At baseline, peripheral CD4 and CD8 T-cells were phenotypically characterized. Thymic function and the levels of different inflammation-related biomarkers, including Lipopolysaccharide Binding Protein (LBP) and anti-cytomegalovirus (CMV) IgG antibodies, were also measured. RESULTS: Influenza vaccine non-responders showed a tendency of higher frequency of regulatory T-cells (Tregs) before vaccination than responders (1.49 [1.08-1.85] vs. 1.12 [0.94-1.63], respectively, p = 0.061), as well as higher expression of the proliferation marker Ki67 in Tregs and different CD4 and CD8 T-cell maturational subsets. The levels of inflammation-related biomarkers correlated with the frequencies of different proliferating T-cell subsets and with thymic function (e.g., thymic function with D-dimers, r = - 0.442, p = 0.001). CONCLUSIONS: Age-related homeostatic dysregulation involving the proliferation of CD4 and CD8 T-cell subsets, including Tregs, was related to a limited responsiveness to influenza vaccination and a higher inflammatory status in a cohort of elderly people.

Thymic Function Impacts the Peripheral CD4/CD8 Ratio of HIV-Infected Subjects.

BACKGROUND: The persistence of an inverted CD4/CD8 ratio has been extensively associated with the increased morbimortality of chronic human immunodeficiency virus (HIV)-infected subjects. Thymic function is crucial for the maintenance of T cell homeostasis. We explored the impact of thymic function on the CD4/CD8 ratio of HIV-infected subjects. METHODS: In a cohort of 53 antiretroviral-naive HIV-infected subjects, the measure of thymic volume, as a representative marker for thymic function, was available at baseline and at 12, 24, and 48 weeks post antiretroviral treatment. RESULTS: Baseline thymic volume was associated with the CD4/CD8 ratio ( Ρ: = 0.413, P = .002), being this association highly dependent on the CD4 T cell levels. In subjects who achieved undetectable viral load after treatment (n = 33), a higher baseline thymic volume was associated with a higher increase in CD4 T cell counts and a decreasing trend in CD8 T cell counts during follow-up. Moreover, the baseline thymic volume was independently associated with the normalization of the CD4/CD8 ratio after 96 weeks of treatment (odds ratio, 95% confidence interval: 1.95 (1.07-3.55); P = .03). CONCLUSIONS: Our data indicate the relevance of the remaining thymic function before the start of treatment to the CD4/CD8 ratio of HIV- infected subjects and, hence, potentially, in their clinical progression.

A Lower Baseline CD4/CD8 T-Cell Ratio Is Independently Associated with Immunodiscordant Response to Antiretroviral Therapy in HIV-Infected Subjects.

We explored if baseline CD4/CD8 T-cell ratio is associated with immunodiscordant response to antiretroviral therapy in HIV-infected subjects. Comparing immunodiscordant and immunoconcordant subjects matched by pretreatment CD4 counts, we observed a lower pretreatment CD4/CD8 T-cell ratio in immunodiscordant subjects. Furthermore, pretreatment CD4/CD8 T-cell ratio, but not CD4 counts, correlated with the main immunological alterations observed in immunodiscordants, including increased regulatory T-cell (Treg) frequency and T-cell turnover-related markers. Then, in a larger cohort, only baseline CD4/CD8 T-cell ratio was independently associated with immunodiscordance, after adjusting by the viral CXCR4-tropic HIV variants. Our results suggest that the CD4/CD8 T-cell ratio could be an accurate biomarker of the subjacent immunological damage triggering immunodiscordance.