The sensitivity and the specificity of two new commercial reagent tests, an indirect fluorescent antibody test (FAT) with a mouse monoclonal antibody (MAb) against respiratory syncytial virus (RSV) and an enzymelinked immunosorbent assay (ELISA) RSV antigen detection kit, were determined by a comparison of results from these tests with those of tissue culture isolation and an indirect FAT with bovine polyclonal antibody (BPA). Of 251 nasal aspirates from infants with suspected RSV infection, positive results were found for 99 (39%) by the FAT-MAb, 93 (37%) by the FAT-BPA, and 87 (35%) by the ELISA; 69 of 240 (29%) were positive by cultures. The FAT-MAb was a more sensitive technique than cultures, with 87% sensitivity for the FAT-MAb and 84% for the ELISA. It was also more sensitive than the FAT-BPA, with 97% sensitivity for the FAT-MAb and 85% for the ELISA. This could be caused only by the distinctive volume of suspended specimens used in these tests. Of 171 negative culture specimens, positive (but not false-positive) results were found for 18% by the FAT-MAb and for 12% by the ELISA. Inversely, 13% of 69 culture positive specimens were FAT-MAb negative and 16% were ELISA negative, emphasizing the importance of tissue cultures for the maximum recovery of RSV, as well as for detection of other respiratory viruses. The FAT-MAb and ELISA were easy to perform and interpret, thus facilitating wider use.

Enteroviruses were specifically detected in crude clinical specimens or in cell cultures in which the viruses were amplified by dot hybridization by using poliovirus type 1-derived, subgenomic radiolabeled cRNA probes (riboprobes). The sensitivity of this test varied from 2.5 to 33%, when clinical specimens without cell culture were examined, and was about 85% in cell culture lysates. The specificity of the test was 90 to 100%. The riboprobe corresponding to the 5'-noncoding sequence specifically detected the majority of enteroviruses (56 of 57 tested); the riboprobe derived from the VPI capsid region hybridized with the three poliovirus serotypes and with some coxsackieviruses type A and with echovirus type 7. Echovirus 22 did not hybridize with any riboprobe. In stool specimens, nasal aspirates, and cerebrospinal fluids from patients with meningitis, only one type of virus was identified in different clinical samples from the same patient by the seroneutralization test. Hybridization allowed the detection of enteroviral RNAs easily in stool specimens and nasal aspirates but with a low efficiency in cerebrospinal fluids without amplification of the viruses in cell cultures.

The hepatitis B core antigen (HBcAg) was expressed in Escherichia coli and in Pichia pastoris. A hexahistidine tag was introduced at the C terminus of the E. coli expressed protein allowing its purification by Ni(2+)-chelate affinity chromatography. The P. pastoris expressed HBcAg was isolated following heat treatment. The two recombinant HBcAgs were purified further on a sucrose gradient. Mass spectrometry analysis suggested that HBcAg was N-acetylated only in P. pastoris and reaction with Ellman's reagent allowed the measurement respectively, of 0.37 and 0.23 mole of free sulfydryl groups per mole of HBcAg monomer expressed in E. coli or P. pastoris. Electron microscopy indicated that the E. coli and the P. pastoris proteins formed capsid-like particles with respectively, a diameter of 34 and 28-nm. Nucleic acid components were found entrapped in both particles but protected from enzymatic treatment only in the P. pastoris derived particles suggesting structural discrepancies between the two recombinant molecules. The high purity of these recombinant antigens allowed the development of a sandwich immunoassay to detect anti-HBc antibodies in human serum. The preliminary results indicate that the P. pastoris HBcAg produced intracellularly is more suitable than the renatured E. coli HBcAg for detection of anti-HBc in this diagnostic assay.

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