Restricted replication of xenotropic murine leukemia virus-related virus in pigtailed macaques.
Del Prete, Gregory Q, Kearney, Mary F, Spindler, Jon et al. · Journal of virology · 2012 · DOI
Quick Summary
This study tested what happens when XMRV, a virus previously linked to ME/CFS, is deliberately introduced into macaque monkeys. The virus was unable to establish a persistent infection—it briefly appeared in the bloodstream but was quickly controlled and eliminated by the immune system. The monkeys remained healthy throughout the study, suggesting that if XMRV infection occurred in humans, it would likely be similarly limited.
Why It Matters
This study addresses a critical question in ME/CFS research: whether XMRV can establish productive infection in primate hosts. The findings support the conclusion that previous human XMRV detections were likely contamination rather than authentic infection, as intrinsic antiviral mechanisms would prevent sustained viral replication even if exposure occurred.
Observed Findings
Peak viremia of ≤2,200 viral RNA copies/ml plasma, declining to undetectable levels by 4 weeks postinfection
Viral DNA remained detectable in peripheral blood mononuclear cells through 119 days despite absent or undetectable viral RNA
Extensive G-to-A hypermutation in cell-associated viral DNA consistent with APOBEC-mediated restriction
Neutralizing antibodies detectable by 2 weeks postinfection and maintained throughout the study
No clinical illness or pathological sequelae observed in either animal during extended follow-up
Inferred Conclusions
XMRV replication and systemic spread are severely restricted in pigtailed macaques, predominantly through APOBEC-mediated hypermutation of the viral genome
If human XMRV infection were to occur, similar innate antiviral mechanisms would restrict productive viral replication
The previously reported associations between XMRV and human diseases likely reflect laboratory contamination rather than authentic infection
Antibody but not cellular immune responses effectively control XMRV in vivo in this model
Remaining Questions
Do variations in human APOBEC genotypes or expression levels affect capacity to restrict XMRV infection, and could this explain individual susceptibility differences?
What This Study Does Not Prove
This animal model study does not directly prove whether XMRV infection occurs or its role in human ME/CFS pathogenesis. Macaque immune responses may differ from human responses in ways relevant to viral persistence. The study also does not address whether XMRV could contribute to disease through transient infection or mechanisms independent of persistent viral replication.
Could transient XMRV infection, even if rapidly controlled, trigger persistent immunological changes contributing to ME/CFS pathogenesis?
How do these macaque findings translate to human infection, given potential species differences in viral tropism, receptor expression, and immune response kinetics?
Were there any tissue-specific sites where XMRV achieved higher replication despite systemic restriction, and could such sites serve as viral reservoirs?