Chemokine receptor 5 (CCR5) plays an important role in the recruitment of monocytes
and T cells in inflammation and experimental studies suggest that CCR5 might be involved
in the pathogenesis of IgA nephropathy. A mutation in the CCR5 gene (CCR5 Delta32),
leading to a nonfunctional receptor, was recently described. We therefore evaluated
the potential role of this mutation on renal survival in patients with IgA nephropathy.
The distribution of the CCR5 Delta32 genotype was determined by polymerase chain reaction
(PCR) analysis in 228 patients with biopsy-proven IgA nephropathy. In 190 patients
with available demographic and clinical follow-up data, the effect of the mutation
on the clinical outcome was analyzed using the Log-rank test and the Cox proportional
hazard model. In vitro, the influence of the CCR5 Delta32 genotype on the chemotactic
response of monocytes was assessed.
Of the 190 patients, 158 (83.2%) had a CCR5 wild-type genotype, 29 (15.3%) were heterozygous,
and three patients had a homozygous CCR5 Delta32 genotype (1.6%). Renal survival was
significantly longer in patients with the CCR5 Delta32 genotype than in the wild-type
group (Log-rank P < 0.001). Using the multivariate Cox proportional hazard model,
the CCR5 Delta32 genotype was identified as an independent factor associated with
a lower risk to develop end-stage renal disease (ESRD) [hazard ratio (HR) 0.23, 95%
CI 0.09 to 0.57, P= 0.002]. In vitro analysis of monocytes from CCR5 Delta32 carriers
showed a reduced chemotactic response to CCR5 ligands in vitro.
Our study demonstrates an independent role of the CCR5 Delta32 genotype for the clinical
outcome in IgA nephropathy. In vitro experiments revealed a reduced chemotactic response
of monocytes from CCR5 Delta32 carriers, thus pointing out a possible pathophysiologic
explanation for the beneficial effect of the CCR5 Delta32 genotype.