Vaccination with SIVmac239Δnef activates CD4⁺ T cells in the absence of CD4⁺ T‐cell loss

Abstract

Background Pathogenic HIV and SIV infections characteristically deplete central memory CD4+ T cells and induce chronic immune activation, but it is controversial whether this also occurs after vaccination with attenuated SIVs and whether depletion or activation of CD4+ T cell play roles in protection against wild-type virus challenge. Methods Rhesus macaques were vaccinated with SIVΔnef and quantitative and phenotypic polychromatic flow cytometry analyses were performed on mononuclear cells from blood, lymph nodes and rectal biopsies. Results Animals vaccinated with SIVΔnef demonstrated no loss of CD4+ T cells in any tissue, and in fact CCR5+ and CD28+CD95+ central memory CD4+ T cells were significantly increased. In contrast, CD4+ T cell numbers and CCR5 expression significantly declined in unvaccinated controls challenged with SIVmac239. Also, intracellular Ki67 increased acutely as much as 3-fold over baseline in all tissues after SIVΔnef vaccination then declined following primary infection. Conclusion We demonstrated in this study that SIVΔnef vaccination did not deplete CD4+ T cells but transiently activated and expanded the memory cell population. However, increases in numbers and activation of memory CD4+ T cells did not appear to influence protective immunity.

CD16− natural killer cells: enrichment in mucosal and secondary lymphoid tissues and altered function during chronic SIV infection

“…To address this problem, we have previously used a flow cytometric bead-normalized assay to calculate absolute numbers of NK cells in peripheral blood, 34 and in this study applied the assay to enumerate NK subsets in both naive and SIV-infected macaques. In a cohort of 18 SIV-naive macaques, the median number of total NK cells was 135 cells/L of blood (range, 22-341 cells/L), similar to other reported numbers for rhesus macaques but somewhat lower compared with humans, 38,39 and, as expected, the bulk of NK cells in peripheral blood were of the CD16 ϩ subset ( Figure 3A Figure 3B).…”

“…Strikingly, expression of CCR5, CCR7, CD62L, Absolute numbers of total circulating NK cells were quantified in whole blood as previously described. 34 NK subset counts were calculated as fractions of the total absolute counts using frequencies determined by polychromatic flow cytometry (Figure 1 and CXCR3 on DN NK cells in chronically infected macaques was nearly half the levels observed in naive macaques and, although less dramatic, CCR6 expression was also significantly reduced ( Figure 4). Similarly, CCR5, CCR7, and CXCR3 were all downregulated on CD56 ϩ NK cells in infected animals.…”

“…A whole-blood, no-wash, bead-normalized assay was used to enumerate total NK cells as described, 34 and absolute counts of different NK subsets were determined by combining polychromatic flow cytometry-generated frequency data with these results.…”

Simian Immunodeficiency Virus Infection Induces Expansion of α4β7+and Cytotoxic CD56+NK Cells

“…However, even in infected animals with low levels of plasma viremia (i.e., Ͻ1,000 copies/ ml), ␣4␤7 expression was similar to that in animals with high ϩ and DN NK cells in naïve and SIV-infected macaques. (E) Absolute numbers of total circulating NK cells were determined by using a bead-based flow cytometric assay as described previously (29,30), and ␣4␤7 ϩ NK cell subset counts were extrapolated using these data combined with NK cell frequency data determined by polychromatic flow cytometry (panel A). Horizontal bars indicate median values for 20 to 27 animals.…”

“…PBMC isolation and polychromatic flow cytometry staining were carried out using protocols described previously for our laboratory (29,31); the antibodies used are listed in Table 1 (Fig. 1A).…”