Vaccination with SIVmac239Deltanef activates CD4+ T cells in the absence of CD4 T-cell loss

J Med Primatol. 2009 Oct;38 Suppl 1(Suppl 1):8-16. doi: 10.1111/j.1600-0684.2009.00370.x.


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 SIVmac239Deltanef and quantitative and phenotypic polychromatic flow cytometry analyses were performed on mononuclear cells from blood, lymph nodes and rectal biopsies.

Results: Animals vaccinated with SIVmac239Deltanef 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 SIVmac239Deltanef vaccination then declined following primary infection.

Conclusion: We demonstrated in this study that SIVmac239Deltanef 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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • CD28 Antigens / metabolism*
  • CD4-Positive T-Lymphocytes / immunology*
  • Immunologic Memory*
  • Lymphocyte Activation*
  • Macaca mulatta
  • Male
  • Simian Immunodeficiency Virus / immunology*
  • Vaccination


  • CD28 Antigens