Primary simian immunodeficiency virus SIVmnd-2 infection in mandrills (Mandrillus sphinx)

Area of Science:

• Primate immunology
• Virology
• Infectious disease modeling

Background:

• Mandrills are unique nonhuman primates (NHPs) naturally infected with two simian immunodeficiency virus (SIV) types: SIVmnd-1 and SIVmnd-2.
• Previous studies showed high SIVmnd-1 replication with only transient CD4+ and CD8+ T-cell count changes.
• Early virus-host interactions are critical for predicting viral control and disease progression in human immunodeficiency virus (HIV) infection.

Purpose of the Study:

• To investigate the immune dynamics during primary SIVmnd-2 infection in mandrills.
• To assess the impact of SIVmnd-2 on immune effectors in blood and lymph nodes (LNs).
• To compare SIVmnd-2 infection patterns with SIVmnd-1 in this NHP model.

Main Methods:

• Mandrills were infected with plasma from SIVmnd-2-infected animals to avoid in vitro strain selection.
• Viral load (plasma viremia, viral DNA in PBMCs and LNs) was monitored post-infection.
• CD4+ and CD8+ T-cell counts and activation markers in blood and LNs were analyzed.

Main Results:

• SIVmnd-2 plasma viremia peaked at days 7-10 (10^7–10^8 RNA copies/ml), followed by a decline to a set point of 10^5–10^6 RNA copies/ml.
• Viral DNA loads in PBMCs and LNs peaked similarly and stabilized during the chronic phase.
• Transient CD4+ T-cell decline in LNs was observed in animals with high peak viral loads; T-cell activation peaked around viral load peaks and returned to baseline.

Conclusions:

• SIVmnd-2 primary infection in mandrills is characterized by high initial viral replication followed by controlled viremia.
• Immune activation is transient and correlates with viral replication peaks, similar to SIVmnd-1 infection.
• The dynamics suggest that nonpathogenic SIV infection in African NHPs may follow a general pattern, providing valuable models for studying lentiviral infections.