Dramatic Rise in Plasma Viremia after CD8+ T Cell Depletion in Simian Immunodeficiency Virus–infected Macaques

TLDR

The study aimed to determine the role of CD8⁺ T cells in controlling SIV replication in vivo by depleting them with an anti‑CD8 monoclonal antibody, OKT8F. The authors performed CD8⁺ T cell depletion in six SIV‑infected macaques using OKT8F, achieving a 99.9 % reduction in peripheral CD8 cells that persisted for eight days. CD8⁺ T cell depletion resulted in a 10–1,000‑fold increase in plasma viremia in five of six macaques, demonstrating that CD8⁺ T cells are essential for suppressing SIV replication.

Abstract

To determine the role of CD8(+) T cells in controlling simian immunodeficiency virus (SIV) replication in vivo, we examined the effect of depleting this cell population using an anti-CD8 monoclonal antibody, OKT8F. There was on average a 99.9% reduction of CD8 cells in peripheral blood in six infected Macaca mulatta treated with OKT8F. The apparent CD8 depletion started 1 h after antibody administration, and low CD8 levels were maintained until day 8. An increase in plasma viremia of one to three orders of magnitude was observed in five of the six macaques. The injection of a control antibody to an infected macaque did not induce a sustained viral load increase, nor did it significantly reduce the number of CD8(+) T cells. These results demonstrate that CD8 cells play a crucial role in suppressing SIV replication in vivo.