Differential Phosphorylation of Akt and signaling in CD4+ T Cells in Pathogenic and Apathogenic SIV Infection

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• HIV and SIV infections cause CD4+ T cell apoptosis and activation-induced cell death (AICD), indicating disease progression.
• African sooty mangabeys (SM) naturally infected with SIV resist disease despite high viral loads, unlike Rhesus macaques (RM).
• Previous work indicated decreased GSK-3β mRNA in SIV+ RM compared to SIV+ SM; this study investigates protein levels and related signaling pathways.

Purpose of the Study:

• To confirm decreased GSK-3β protein expression in SIV+ RM.
• To investigate Akt kinase activity and phosphorylation at Thr308 in CD4+ T cells from SIV-infected animals.
• To correlate T cell subset-specific signaling differences with AICD and lentivirus-induced disease resistance.

Main Methods:

• Western blot analysis to assess GSK-3β protein levels.
• Flow cytometry to analyze Akt and p-AktThr308 expression in CD4+ T cells after CD3/CD28 stimulation.
• Comparison of signaling pathways and apoptosis rates across different primate species (RM, SM) and infection statuses (uninfected, SIV+).

Main Results:

• GSK-3β protein expression is confirmed to be decreased in SIV+ RM.
• SIV+ RM CD4+ T cells exhibit increased total Akt and p-AktThr308 upon stimulation, correlating with elevated apoptosis.
• These molecular and cellular differences are species-specific, T cell subset-specific, and linked to AICD.

Conclusions:

• Decreased GSK-3β and altered Akt signaling (specifically p-AktThr308) in SIV+ RM CD4+ T cells are associated with increased apoptosis and disease susceptibility.
• Species-specific differences in T cell signaling pathways, including Akt phosphorylation site specificity, may explain varying resistance to lentivirus-induced disease.
• Understanding these pathways offers insights into mechanisms of SIV/HIV pathogenesis and potential therapeutic targets.