Effects of human alpha, beta and gamma interferons on varicella zoster virus in vitro.

The antiviral effects of interferon (IFN) on varicella zoster virus (VZV) and herpes simplex virus (HSV) in vitro were examined. The values for the 50% inhibitory dose (ID50) of IFN-alpha, beta and gamma determined by plaque reduction assay, were 0.813, 0.650 and 13.750 IU/ml, respectively, against VZV and 18.00, 10.38 and 115.0 IU/ml, respectively, against HSV. Thus IFN-alpha and beta were more effective than IFN-gamma against both VZV and HSV and VZV was more sensitive than HSV to the IFNs. Five mutants of VZV which were resistant to acyclovir (ACV), phosphonoacetic acid (PAA) or bromodeoxyuridine (BUDR) were also sensitive to IFN beta, their average ID50 being 1.31 IU/ml. Analysis of virus-specific proteins by the immunofluorescent technique with various antisera showed that IFN had a significant effect before early protein synthesis.

Hantaanvirus among urban rats from a slum area in Bangkok.

A total of 106 rodents sera from slum Wat Phai Ton and slum Klong Toey were examined by immunofluorescent antibody assay during May to August 1990. The positive sera were further tested by plaque reduction neutralization test with the prototype hantaanvirus and the rat-associated hantaan like virus. Isolation attempts were also performed from their tissues. Antibody-positive rats were found in both slum areas, 32.7% in slum Wat Phai Ton and 5.6% in slum Klong Toey. Rattus norvegicus was the major species found positive. Positive plaque reduction neutralization results indicated that the infecting virus was antigenically similar to the strain of rat-associated hantaanvirus. The presence of low titer antibodies (IFA titer 32 to 128) may be an obstacle to isolation of associated virus using tissue culture.

Immunofluorescence, enzyme-linked immunosorbent assay, particle agglutination and western blot for the detection of antibody to human immunodeficiency virus type 1.

Immunofluorescence assay (IFA) has been applied for detection of antibody to human immunodeficiency virus type 1 (HIV-1). To compare the IFA with an enzyme-linked immunosorbent assay (ELISA) and particle agglutination (PA), we examined the antibody response to HIV-1 in 475 sera from AIDS, PGL and ARC patients as well as several risk groups and healthy persons by three methods. The positive results by any methods were confirmed by western blot (WB). The results by all methods were well correlated on the sera from 45 asymptomatic male homosexuals and 70 female prostitutes. There were some false positive results by ELISA in the sera from prisoners and healthy persons. Four sera from drug abusers were positive only by PA and IFA and were negative by ELISA. All were WB-inconclusive. Particle agglutination and IFA results were compared with western blot analysis on 208 ELISA-positive sera. All IFA-strongly positive sera (84%) were positive by western blot. The sera with weakly positive, negative and inconclusive results by IFA (16%) were possibly any of positive, inconclusive or negative by western blot. By PA, 200 of 208 (97%) sera were PA-positive and 1% of these sera were WB-inconclusive while the PA-negative sera were either negative or inconclusive by western blot. These results suggested that PA is a simple and sensitive method for screening of HIV-1 antibody while IFA could be a primary confirmatory test and western blot would then be used for confirming any IFA-negative or inconclusive results.