Effect of heat or formalin treatment of leptospires on antibody response detected by immunoblotting

Abstract

Leptospira interrogans serovar icterohaemorrhagiae RGA (RGA), live or heated at 56°C for 15 min or treated with Formalin, was injected into rabbits to prepare hyperimmune serum. The pathogens L. interrogans serovars icterohaemorrhagiae RGA, icterohaemorrhagiae 1, canicola Moulton, grippotyphosa Andaman, hardjo Hardjoprajitno, and pomona Pomona and the nonpathogen Leptospina biflexa serovar patoc Patoc I were processed for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and after electrophoresis they were then transferred to nitrocellulose paper. Antiserum against RGA (live, heat killed, or Formalin killed) was used on one of each of the three blots. Formalin appeared to completely eliminate antibody response to antigens with the molecular weight of 14,000 to 20,000 (14K to 20K) but did expose an antigen at approximately 23K in the pathogens only. This same band had only slight reactivity when antiserum against heat-killed RGA was used. Heating also eliminated cross-reactivity in the 19K to 30K range and partially degraded bands in the 14K to 20K region so that one broad band rather than several discrete bands appeared. The three antiserum specimens cross-reacted with all of the serovars tested, but fewer antigens of grippotyphosa and hardjo reacted with the antisera. Against patoc, reactivity was limited primarily to the flagellar region. The most cross-reactivity was with the antiserum prepared by using live leptospires.