Variation and polymorphism in helminth parasites
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Date
2002Author
Maizels, Rick
Kurniawan Atmadja, Agnes
Metadata
Abstract
There are strong biological, evolutionary and immunological arguments for predicting extensive polymorphism among
helminth parasites, but relatively little data and few instances from which the selective forces acting on parasite diversity
can be discerned. The paucity of information on intraspecific variation stands in contrast to the fine detail with which
helminth species have been delineated by morphological techniques, accentuating a trend towards considering laboratory
strains as representative of a relatively invariant organism. However, in the fast-moving evolutionary race between host
and parasite one would predict a monomorphic species would be driven to extinction. We review the arena of intraspecific
variation for the major helminth parasites, ranging from biological properties such as host or vector preference, to
biochemical and immunological characteristics, as well as molecular markers such as DNA sequence variants. These data
are summarized, before focusing in more detail on polymorphisms within protein-coding genes of potential relevance to
the host-parasite relationship, such as vaccine candidates. In particular, we discuss the available data on a number of major
antigens from the filarial nematode Brugia malayi. Information is currently too sparse to answer the question of whether
there is antigenic variation in filariasis, but the indications are that proteins from the blood-borne microfilarial stage show
significant intraspecific variability. Future work will define whether polymorphisms in these antigens may be driven by
exposure to the host immune response or reflect some other facet of parasite biology.