A study of var gene transcription in vitro using universal var gene primers

The polymorphic multigene family, var, encodes the variant antigen, Plasmod ium falciparum erythrocyte membrane protein 1 (PfEMP1), present on the surf ace of erythrocytes infected with the human malaria parasite, P. falciparum . PfEMP1 has been implicated in the pathology of malaria through its abilit y to bind to host endothelial receptors and uninfected erythrocytes. Unders tanding the relationship between host-pathology, immune response and parasi te variation is crucial, but requires a method of reliably detecting and di fferentiating all possible var genes. Several primer pairs used to date are biased and limited in their detection capacity. Here we describe a set of PCR primers that amplify the majority of cai genes in the laboratory isolat es 3D7 and A4, and appear to work equally well on all isolates tested. We u se these universal primers to examine the relationship between var gene tra nscription as assessed by reverse transcriptase-PCR (RT-PCR) with that meas ured by Northern analysis of parasite RNA. Phenotypically selected young pa rasites have multiple transcripts detected by RT-PCR, but the full-length t ranscript appears to be homogeneous. In addition, we demonstrate that the c hoice of primers used for RT-PCR is crucial in data interpretation. (C) 200 0 Elsevier Science B.V. All rights reserved.