ImmunologyTier 1Medical Sciences concept

CMV risk stratification in solid organ transplant (donor/recipient serostatus)

Core concept

Post-transplant CMV risk is stratified by donor (D) and recipient (R) CMV IgG serostatus -- the combination determines whether disease arises from primary infection (from the graft) or reactivation of latent recipient virus
Highest risk: D+/R- (seropositive donor, seronegative recipient) -- recipient has no pre-existing immunity, receives latent virus within the graft -> primary infection, most severe disease pattern
Lowest risk: D-/R- -- no virus present in donor or recipient (still needs CMV-safe blood products, but no graft-transmitted risk)

Donor/Recipient	Risk level	Mechanism
D+/R-	Highest	Primary infection from graft; no pre-existing recipient immunity
D+/R+ or D-/R+	Intermediate	Reactivation of recipient's latent virus (immunosuppression-driven)
D-/R-	Lowest	No virus present in either; use CMV-safe (leukoreduced/seronegative) blood products

Two management strategies for at-risk groups: universal prophylaxis (antiviral, e.g. valganciclovir, for a defined post-transplant period) or pre-emptive therapy (regular PCR monitoring, treat only on viraemia) -- choice depends on risk category and organ type
D+/R- patients typically receive the longest prophylaxis duration given highest disease risk and risk of severe primary infection

Trap: assuming a seropositive recipient (R+) is protected -- pre-existing immunity reduces but does not eliminate risk; reactivation under transplant immunosuppression remains common (intermediate-risk category, not low-risk)
CMV disease in a transplant recipient can present as a viral syndrome (fever, cytopenias) or as tissue-invasive disease (colitis, pneumonitis, retinitis, and notably allograft-specific involvement, e.g. CMV hepatitis in liver transplant, which can mimic rejection)
Serostatus determined pre-transplant for both donor and recipient specifically to guide this risk stratification and prophylaxis strategy -- a routine part of transplant work-up, not an incidental test

Same D/R serostatus logic (and the requirement for CMV-safe blood products in D-/R- pairs) - see blood product irradiation
CMV disease timing (typically weeks-months post-transplant, or after prophylaxis discontinuation -- "late-onset CMV") fits the broader post-transplant infection timeline framework (a separate microbiology note)
CMV reactivation risk parallels other latent herpesvirus reactivation under immunosuppression (EBV -> PTLD) -- same principle of immunosuppression unmasking latent infection, different virus and different disease consequence

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