Variant proteins of Plasmodium vivax are not clonally expressed in natural infections
Plasmodium vivax is the most widely distributed human malaria parasite and responsible for 70–80 million clinical cases each year and a large socio-economical burden. The sequence of a chromosome end from P. vivax revealed the existence of a multigene superfamily, termed vir (P. vivax variant antigens), that can be subdivided into different subfamilies based on sequence similarity analysis and which represents close to 10–20% of the coding sequences of the parasite. Here we show that there is a vast repertoire of vir genes abundantly expressed in isolates obtained from human patients, that different vir gene subfamilies are transcribed in mature asexual blood stages by individual parasites, that VIR proteins are not clonally expressed and that there is no significant difference in the recognition of VIR-tags by immune sera of first-infected patients compared with sera of multiple-infected patients. These data provide to our knowledge the first comprehensive study of vir genes and their encoding variant proteins in natural infections and thus constitute a baseline for future studies of this multigene superfamily. Moreover, whereas our data are consistent with a major role of vir genes in natural infections, they are inconsistent with a predominant role in the strict sense of antigenic variation.
Document Type: Research Article
Affiliations: 1: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Avenida Lineu Prestes 1374, São Paulo, SP 05508-900, Brazil. 2: Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Avenida Lineu Prestes 580, São Paulo, SP 05508-900, Brazil. 3: Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo, Avenida Lineu Prestes 1524, São Paulo, SP 05508-900, Brazil. 4: Fertility, Centro de Fertilização Assistida, Avenida Brig. Luís Antônio 4258, São Paulo, SP 01402-002, Brazil. 5: Departamento de Estatística, Instituto de Matemática e Estatística, Universidade de São Paulo, Rua do Matão 1010, São Paulo, SP 05508-900, Brazil.
Publication date: November 1, 2005