Premature aging of T cells is associated with faster HIV-1 disease progression

Immunosenescence: what does it mean to health outcomes in older adults?

The most profound consequences of immune senescence with respect to human health are the increased susceptibility to infectious diseases and decreased vaccine efficacy. Changes in both innate and adaptive immune function converge in the reduced response to vaccination and protection against infection and related diseases. The decline in thymic output of naïve T cells diminishes responses to novel antigens, such as West Nile Virus, while clonal expansions leading to defects in the T cell repertoire are associated with blunted responses of memory T cells to conserved epitopes of the influenza virus. Recent studies on how immunologic mechanisms of protection change during aging have led to novel strategies for improving vaccine responsiveness and outcomes of infectious diseases in older adults.

Vaccination in the elderly: an immunological perspective

Successful vaccination of the elderly against important infectious pathogens that cause high morbidity and mortality represents a growing public health priority. Building on the theme of aging and immunosenescence, we review mechanisms of human immunosenescence and the immune response to currently licensed vaccines. We discuss the difficulties in identifying the risk factors that, in addition to aging, cause immunosenescence and address the relative paucity of vaccine studies in the elderly. We conclude that vaccine responses are blunted in the elderly compared with that of healthy young adults. However, it is also clear that our understanding of the mechanisms underlying immunosenescence is limited and much remains to be learned to improve the effectiveness of next generation vaccines.

Association of HIV-specific and total CD8+ T memory phenotypes in subtype C HIV-1 infection with viral set point

Understanding early immunological events during HIV-1 infection that may set the course of disease progression is important for identifying correlates of viral control. This study explores the association of differentiation profiles of HIV-specific and total memory CD8(+) T cells with viral set point. A cohort of 47 HIV-1-infected individuals, with differing viral set points at 12 mo, were recruited during acute infection. We identified that the magnitude of IFN-gamma(+) T cell responses at 6 mo postinfection did not associate with viral set point at 12 mo. A subset of 16 individuals was further studied to characterize CD8(+) T cells for expression patterns of markers for memory differentiation, survival (CD127), senescence (CD57), and negative regulation (programmed death-1). We show that viral control and the predicted tempo of HIV disease progression in the first year of infection was associated with a synchronous differentiation of HIV-specific and total CD8(+) memory subpopulations. At 6-9 mo postinfection, those with low viral set points had a significantly higher proportion of early differentiated HIV-specific and total memory CD8(+) cells of a central memory (CD45RO(+)CD27(+)CCR7(+)) and intermediate memory (CD45RO(-)CD27(+)CCR7(-)) phenotype. Those with high viral set points possessed significantly larger frequencies of effector memory (CD45RO(+)CD27(-)CCR7(-)) cells. The proportions of memory subsets significantly correlated with CD38(+)CD8(+) T cells. Thus, it is likely that a high Ag burden resulting in generalized immune activation may drive differentiation of HIV-specific and total memory CD8(+) T cells.