Prevalence of CCR5 Gene 32-Basepair Deletion in Populations of Slavic Origin

To the Editor: We read with interest recently published brief report by Ristić et al (1) on the frequency of CCR5 chemokine receptor gene 32-basepair deletion (CCR5Δ32) in Croatian normal population. In the study, 303 randomly selected healthy Croatians were genotyped for the presence of CCR5Δ32 and 7.1% allele frequency of this most important mutation, which prevents HIV transmission and delays the onset of AIDS, was identified. It is the first study of CCR5Δ32 allele frequency in Croatian population.

We were surprised to read the author’s statement that the data on CCR5Δ32 mutation prevalence in the populations of Slavic origin were rather scarce. The authors supported their statement by citing a paper published by Voevodin et al (2) in 1998. Additionally, although the authors stated that the aim of their study was to “assess the genetic susceptibility of Croatians, as a part of the Slavic population”, they did not compare the CCR5Δ32 allele frequency established in Croats with those already found in populations of Slavic origin, but rather with the allele frequencies identified in Northern European populations, Hungarians, Turks, Italians, Greeks, Spanish, Sardinians, Basques, and Corsicans.

To identify the current evidence on CCR5Δ32 mutation prevalence in the populations of Slavic origin, we searched PubMed/Medline without any search limits using the search term CCR5 coupled with one of following terms: Slavs, Slavic, Russia, Russian, Ukraine, Ukrainian, Rusyn, Belorussia, Belorussian, Belarus, Belarusian, Belorus, Belorusian, Poland, Polish, Poles, Czechoslovakia, Czech Republic, Czech, Slovakia, Slovak, Moravian, Sorbs, Croatia, Croatian, Croat, Slovenia, Slovenian, Yugoslavia, Yugoslavic, Serbia, Serbian, Serb, Montenegro, Montenegrian, Montenegrin, Bosnia, Bosnian, Bosnian, Bosniaks, Macedonia, Macedonian, Bulgaria, and Bulgarian. The search was carried out on February 01, 2006. From the described search, 23 studies published in peer-reviewed journals were initially identified. All main review articles concerning CCR5Δ32 and other HIV resistance mutations published between 1996-2005 were carefully examined. Finally, after excluding the studies published after March 01, 2005 (because Ristić and colleagues submitted their CMJ paper on March 29, 2005) and those examining the prevalence of CCR5Δ32 mutation in individuals or patients not representing normal population (eg, HIV infected individuals, hepatitis C-infected patients, patients with pulmonary sarcoidosis, and soon), 14 studies published in peer-reviewed journals were selected and evaluated. From the results of the selected studies, it is clear that the data on CCR5Δ32 prevalence in the populations of Slavic origin are far from being scarce. The frequency of CCR5Δ32 has been already established in all three main populations of Eastern Slavs: Russians (2-9), Ukrainians (3,5,10), and Belarussians (3,9); in three out of four main Western Slavic populations: Poles (11), Czechs (12,13), and Slovaks (14); and in two populations of South Slavs: Bulgarians (15,16) and Slovenians (17), representing two main branches of South Slavs, South-Eastern and South-Western Slavs, respectively. Now, Ristić et al (1) contributed Croatian data.