Multi-center European evaluation of HIV testing on serum and saliva samples.

OBJECTIVE: to evaluate the reliability of HIV antibody testing on saliva. DESIGN: matched serum and saliva samples were collected from both seronegative (n = 344) and seropositive (n = 125) individuals in five European countries. Duplicate saliva samples collected with Omni-Sal devices provided by Saliva Diagnostic System (SDS) were pooled before analysis. METHODS: all samples were analyzed by Recombinant HIV1 EIA Cambridge Bioscience and 2nd generation Abbott HIV 1&2 1A80. EIA procedures were adapted for saliva testing by modification of sample dilution and/or cut-off calculation. All saliva recording positive and/or doubtful EIA results were further analyzed by Western blot as a confirmatory method. RESULTS: EIA results obtained from sera analysis from both seropositives and seronegatives allowed for calculation of the tests' sensitivity (HIV1 Biotech: 99.2%-100%; Abbott: 100%) and specificity (both tests 100%). In the series of 125 saliva samples collected from seropositives, the EIA results were as follows: with Biotech (3 negative, 3 in the grey-zone and 119 reactive) and with Abbott (1 negative, 1 in the grey-zone and 123 reactive). One saliva sample found negative by both EIA tests, although fulfilling HIV1 WB criteria of positivity, was collected from an HIV2 infected person. Out of 125 saliva samples collected from seropositives, 121 produced positive Western Blot profiles, 4 were indeterminate and 1 was found negative whereas 125/125 sera were found positive. CONCLUSION: the reliability of HIV testing of saliva is dependent on the sensitivity of EIA tests and on the criteria used for the interpretation of Western blot tests as well. Although saliva testing offers numerous advantages for epidemiological purposes, it should not be recommended for diagnosis.

Differential diagnosis of HTLV-I and HTLV-II infections by restriction enzyme analysis of 'nested' PCR products.

A 'nested' polymerase chain reaction (PCR) assay is described which is capable of detecting single copies of human T-cell lymphotropic virus (HTLV) in genomic DNA extracted from peripheral blood mononuclear cells (PBMCs). A single set of 'nested' oligonucleotide primers, based on the highly conserved tax/rex region of the viral genome, was able to detect both HTLV-I and HTLV-II proviral sequences in clinical samples of diverse geographical origins, from the United States, Great Britain, Japan, the Caribbean, Italy, Greece, Iraq and West Africa. Rapid discrimination between HTLV-I and HTLV-II infections was achieved by restriction enzyme analysis of unpurified second-round PCR products, even in those cases in which serological assays had failed to provide a definitive result. Over a 2-year period, a total of 53 HTLV infections (37 HTLV-I and 16 HTLV-II) were identified by this technique and complete concordance with serological typing, available in 41 cases, was observed.

Comparison of ELISA, SPACE, and electron microscopy for the routine diagnosis of rotavirus infection.

Previous studies on the serological diagnosis of rotavirus infection have utilised locally produced antibodies. In this study we have compared two commercially produced assays, an ELISA (Rotazyme, Abbott) and a newly developed assay--solid phase aggregation of coupled erythrocytes (SPACE) (Wellcome Research Laboratories), with electron microscopy (EM). The SPACE test appeared less sensitive than EM. The ELISA was shown to be as sensitive as EM but more versatile. Our experience suggests that the ELISA could be successfully incorporated into the routine of any diagnostic laboratory.

Virus diarrhoea associated with pale fatty faeces.

Steatorrhoea was a significant feature in an outbreak of rotavirus gastroenteritis which affected adults and infants in hospital. Fat globules or fatty acid crystals were obvious by light microscopy (LM) in faeces from 14 of 25 patients examined. Ten of the fatty stools and two of the remainder were very pale. By electron microscopy (EM) a rotavirus was seen in 11 of the 14 fatty faeces and in only two of 11 specimens without visible fat. In a further study of pale or fatty faeces 20 such specimens sent for laboratory examination from patients not involved in the hospital outbreak were compared microbiologically with a similar number which were neither pale nor fatty. Viruses were found by EM in 11 (55%) of the pale or fatty stools; eight rotaviruses, two astroviruses and an uncultivable adenovirus were seen; one further patient had acute jaundice. In contrast, no viruses were seen by EM in the twenty specimens which were normally pigmented and without evident fat. Steatorrhoea was significantly associated with rotavirus infection of the alimentary tract which usually presented as a fatty enteritis. We conclude that rotaviruses certainly, and other viruses possibly, can impede both the digestion of fat and the pigmentation of the faeces. Inspection and LM of faeces are easy. In acute enteritis a fatty or pale stool is an indication for virological examination.

Use of the ultracentrifuge vertical rotor in the detection of rubella-specific IgM on a sucrose density gradient.

A comparison was made of the performance of swing-out and vertical ultracentrifuge rotors in the detection of rubella-specific IgM on a sucrose density gradient. Tests were performed on 30 sera, of which 11 were found to contain rubella-specific IgM by both methods. The centrifugation time for the swing-out rotor was 16 hours at 35,000 rpm. This was reduced to 2 hours using the vertical rotor at 50,000 rpm. Routine use of the vertical rotor would allow a reduction in the time taken to perform the test, increase the number of sera tested each time, and reduce wear on the ultracentrifuge.

Rapid adenovirus typing by immunoelectron microscopy.

A rapid method of typing adenoviruses by immunoelectron microscopy is discribed. This emphasizes the value of an electron microscope in diagnostic virology, especially when a rapid result is required in epidemiology.