Limited Protective Effect of the CCR5D32/ CCR5D32 Genotype on Human Immunodeficiency Virus Infection Incidence in a Cohort of Patients with Hemophilia and Selection for Genotypic X4 Virus

The relationship among CCR5 genotype, cytomegalovirus infection, and disease progression and death was studied among 159 human immunodeficiency virus (HIV)–infected patients with hemophilia. One patient (0.6%) had the CCR5D32/CCR5D32 genotype (which occurs in ∼2 % of the Scandinavian population) and a rapid disease course. His HIV V3 region contained genotypic features attributable to X4 virus and resembled functionally verified X4 virus and virus from patients treated with a CD4 cell–stimulating drug, tucaresol. Age-related dif-ferences in disease progression rate and survival time were seen for CCR5/CCR5 patients. Surprisingly, no protective effect of the CCR5/CCR5D32 genotype on disease progression or survival was seen for children but was evident for adults. Age group–related immunologic differences might explain this variation, and transmission route and/or viral phenotype variation within donor virus may be related to the limited protection of the CCR5D32/CCR5D32 genotype. Sequence comparisons indicate that X4 virus can be selected in vivo due to either absence of CCR5 receptors or relative increase of CXCR4 receptors. Other than CD4, several receptors among the group of 7-membrane G protein–coupled chemokine receptors have been demonstrated to be essential to human im