CD4/CD8 Ratio and KT Ratio Predict Yellow Fever Vaccine Immunogenicity in HIV-Infected Patients

Background: hiv-infected individuals have deficient responses to yellow fever vaccine (yfv) and may be at higher risk for adverse events (ae). chronic immune activation–characterized by low cd4/cd8 ratio or high indoleamine 2,3-dioxygenase-1 (ido) activity—may influence vaccine response in this population. methods: we prospectively assessed ae,viremia by the yfv virus and yf-specific neutralizing antibodies (nab) in hiv-infected (cd4>350) and -uninfected adults through 1 year after vaccination. the effect of hiv status on initial antibody response to yfv was measured during the first 3 months following vaccination,while the effect on persistence of antibody response was measured one year following vaccination. we explored cd4/cd8 ratio,ido activity (plasma kynurenine/tryptophan [kt] ratio) and viremia by human pegivirus as potential predictors of nab response to yfv among hiv-infected participants with linear mixed models. results: 12 hiv-infected and 45-uninfected participants were included in the final analysis. hiv was not significantly associated with ae,yfv viremia or nab titers through the first 3 months following vaccination. however,hiv–infected participants had 0.32 times the nab titers observed for hiv-uninfected participants at 1 year following yfv (95% ci 0.13 to 0.83,p = 0.021),independent of sex,age and prior vaccination. in hiv-infected participants,each 10% increase in cd4/cd8 ratio predicted a mean 21% higher post-baseline yfv nab titer (p = 0.024). similarly,each 10% increase in kt ratio predicted a mean 21% lower post-baseline yfv nab titer (p = 0.009). viremia by human pegivirus was not significantly associated with nab titers. conclusions: hiv infection appears to decrease the durability of nab responses to yfv,an effect that may be predicted by lower cd4/cd8 ratio or higher kt ratio. © 2016 avelino-silva et al.