A neuraminidase-inhibition (NI) assay performed in microtiter plates is described. This micro-NI assay is a modification of the NI assay recommended by the World Health Organization. It reduces the quantity of reagents required and permits antigenic classification of many isolates simultaneously. To determine the accuracy and sensitivity of this micro-NI assay, 110 influenza A viruses, representing all subtypes, based upon the nine known neuraminidases (NAs), were classified by both the micro-NI and macro-NI assays in two separate laboratories. The NAs were identified accurately by the micro-NI assay. Virus mixtures were detected by both assays, although the macro-NI was clearly more sensitive. The micro-NI assay was also suitable for testing sera for the presence of antibodies to the NAs. Although the micro-NI assay did not provide the quantitation of the macro-NI assay, it did prove to be a rapid method for virus classification and antibody studies on influenza A viruses.

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Monoclonal antibodies (MAbs) were produced to four Chlamydiapsittaci isolates: NJ1 and TT3 from turkeys, VS1 from a parakeet, and B577 from an ovine abortion. MAbs were tested for reactivity with each isolate by the indirect immunofluorescent antibody technique and for neutralization by an inclusion reduction neutralization technique in tissue culture. Two genus-specific and 14 serovar-specific MAbs were produced. Genus-specific MAbs reacted with aHl avian and mammalian isolates; however, each failed to neutralize its homologous chlamydial isolate. Turkey isolates NJ1 and TT3 were antigenically similar; serovar-specific MAbs produced to each reacted equally with both isolates yet showed little or no reaction with other serovars. Serovar-specific MAbs to the parakeet and abortion isolates were distinct; no cross-reactions were seen with other serovars. None of the serovar-specific MAbs reacted with an ovine arthritis isolate. Of the 14 serovar-specific MAbs, 13 partially neutralized homologous strains with or without the addition of complement. Because of the high specificity, the serovar-specific MAbs used with the immunofluorescence technique provided a rapid and precise method to identify three serovars of C. psittaci

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