In this work we investigated the frequency of polymorphism in exon II
of the gene encoding most of the amino-terminal region of the serine
rich antigen (SERA) in Plasmodium falciparum field samples.
The blood samples were colleted from P. falciparum infected individuals
in three areas of the Brazilian Amazon. Two fragments have been
characterized by polymerase chain reaction: one of 175 bp corresponding
to the repeat region with 5 octamer units and one other of 199 bp
related to the 6 repeat octamer units of SERA protein. The 199 bp
fragment was the predominant one in all the studied areas. The higher
frequency of this fragment has not been described before and could be
explained by an immunological selection of the plasmodial population in
the infected individuals under study. Since repeat motifs in the
amino-terminal region of SERA contain epitopes recognized by
parasite-inhibitor antibodies, data reported here suggest that the
analysis of the polymorphism of P. falciparum isolates in different
geographical areas is a preliminary stage before the final drawing of
an universal vaccine against malaria can be reached