The micro-focus reduction neutralization test for determining dengue and Japanese encephalitis neutralizing antibodies in volunteers vaccinated against dengue.

A micro-focus reduction neutralization test (mFRNT) was evaluated as an alternative test to the ordinary plaque reduction neutralization test (PRNT) for the determination of dengue virus and Japanese encephalitis virus neutralizing antibody responses in persons receiving dengue vaccine. The 2 tests were similar in terms of titres and ability to detect seroconversion. Although the neutralizing antibody titres obtained by mFRNT were slightly lower than those given by PRNT, the differences were less than two-fold, indicating than mFRNT was reliable. Reproducibility of mFRNT was confirmed by 10 replicate tests using the same control serum. Therefore, mFRNT may be useful in large-scale investigations of neutralizing antibody levels, for example, in young children forming part of an immunization programme; it can be performed quickly and is economical, requiring only a small volume of sera.