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Purified antigens

As a need to have better tools for diagnosis grew, in the 1980s several purified antigens were tested with panels of well-characterized sera. The first attempts used surface glycoproteins, theoretically more exposed to the immune system. Several publications using antigens of 25,100 90,101 and 72 kDa102 did show that results improved, with higher specificity and without loss of sensitivity. The problem was that preparation of these antigens required special technical conditions and manufacturers were not interested. These purified antigens have been tested mainly in ELISA systems.

Recombinant proteins

By the end of 1980s, recombinant protein technology had grown and several laboratories published an array of candidate antigens for use in diagnostic tests, claiming good specificity and sensitivity. Even if most of them were different proteins, some proved to be homologous. The real value of these recombinant proteins was tested with the support of TDR/WHO in 10 laboratories that received 50 coded sera.103 Results showed that a single recombinant have few chances to detect all the infected samples. Therefore the tendency was to mix several recombinants.104 The better mixture (FRA and CRA) was used in kits which have been distributed to all government laboratories in Brazil.

Other recombinant proteins have been produced by several manufacturers and are widely available (i.e., Wiener ELISA Recombinante®, Immuno Comb II Chagas®, ARCHITECT Chagas®) with good results. Interestingly, some of these kits may have occasional false-positive results, probably due to reactions to remaining antigens in the process of fabrication. These recombinant antigens have also been used in combination to make rapid tests, several of which are available in the market.

 
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