Antibodies to HSP-70 in normal donors and autoimmune hearing loss patients

Objective. To evaluate serum antibody to heat shock protein (HSP) 70 as a marker for autoimmune sensorineural hearing loss (AISNHL). Design: Sera from 20 patients with rapidly progressive sensorineural HL and 20 control volunteers without HL were tested for antibody reactivity against multiple HSP 70 substrates. Substrates included recombinant human HSP (rHuHSP) 72, purified bovine brain heat shock cognate (HSC) 73 and HSP 72, as well as heat-shocked and non-heat-shocked protein extracts from bovine kidney (MDBK) cells. All serum donors were previously tested for antibody to guinea pig inner ear supporting cells; 17 of 20 patients but none (0 of 20) of the controls were positive. Methods. Sera were tested using Western blots. Results. Reactivity with rHuHSP 70 was observed in 16 patients and 17 controls. Similarly, 15 of 20 patients and 17 of 20 controls stained for both HSP 72 and HSC 73 from the bovine brain. When tested against the heat-shock-induced and control MDBK extracts, six patients and nine controls had greater reactivity with the induced HSP 72. Conclusion: The frequency of antibodies to HSP substrates did not differ in patients and controls. Prior studies reported that HSP 72 is the 68 kD antigen commonly detected by AISNHL sera. However, we show that HSP 72 antibodies are no more prevalent in patients than in normal controls. Thus, it is unlikely that the 68 kD protein is HSP 72. Therefore, HSPs are not appropriate substrates for serodiagnosis of AISNHL.