Immune activation in human rabies.

Serum cytokines were compared by enzyme-linked immunosorbent assay among (i) 28 patients with rabies, (ii) 13 patients with non-fatal encephalitis due to other viruses, (iii) 16 patients with immune-mediated neurological diseases, and (iv) 15 patients with non-viral central nervous system infections and non-HTLV-I progressive spastic paraparesis. Levels of soluble interleukin 2 receptor (S-IL2R) were comparable in groups (i)-(iii). Fewer paralytic (1/6) than encephalitic (12/22) rabies patients had elevated S-IL2R. Only one patient with rabies and one with non-fatal viral encephalitis (group ii) had elevated S-CD8. Interleukin 6 (IL-6) was elevated in 5/22 rabies patients with encephalitis and in 0/6 paralytic rabies patients. Four individuals in groups (ii) and (iii) had elevated IL-6. Patterns of cytokine responses in group (iv) were similar to those in groups (i)-(iii). The results suggest defects in immune responsiveness in paralytic rabies.

Diagnosis of rabies by polymerase chain reaction with nested primers.

A simple, sensitive, and specific polymerase chain reaction (PCR) protocol for detection of rabies virus is described. The process consists of sample preparation, reverse transcription, two-step DNA amplification, and detection of the amplified product. RNA was extracted from animal and human brain by phenol-chloroform using guanidinium thiocyanate. Viral RNA was then amplified in a two-step PCR that used two sets of nested primers designed to amplify rabies nucleocapsid (N) sequence. Rabies nucleocapsid sequence was amplified from all brain samples from 95 dogs and 3 humans with rabies confirmed by fluorescent antibody (FAT) and mouse inoculation tests (MIT). Rabies-negative brain samples (110 dogs, 2 humans) were PCR-negative. The process requires < 24 h. Detection of viral RNA was still possible in brain material that was left at room temperature for 72 h. As little as 8 pg of rabies virus RNA could be detected. This technique could have practical applications as a confirmatory test to FAT at busy rabies diagnostic centers.

Cells with natural killer activity in human rabies.

Cytotoxic lymphocyte function in 13 patients with rabies was studied by counting the number of CD56 cells and assessing natural killer (NK) cell activity. There was no significant difference in the number of killer cells between rabies patients and 31 normal controls (P greater than 0.05). Two of six non-fatal encephalitic patients due to causes other than rabies had reduced CD56 numbers. Base-line NK cell responses versus K562 cell targets did not differ among the normal control and rabies groups (P greater than 0.05). Study of the non-rabies encephalitis group showed heterogeneous results with wide variation. Significant enhancement of NK activity was seen in four rabies patients and in 10 normal control subjects tested after interferon-alpha (IFN-alpha) and IL-2. None of the four patients with encephalitis due to causes other than rabies showed such enhancement. Our results suggest that NK cells of rabies patients are not fully stimulated and that this might contribute to the virulence of rabies. The cause of this phenomenon remains unknown.