Production in Escherichia coli, purification and immunogenicity of acrosomal protein SP-10, a candidate contraceptive vaccine

P. Prabhakara Reddi, James R. Castillo, Kenneth Klotz, Charles J. Flickinger, John C. Herr

Research output: Contribution to journalArticlepeer-review


The testis-specific human sperm antigen, SP-10, has been designated a 'primary vaccine candidate' by the World Health Organization Taskforce on Contraceptive Vaccines. Molecular cloning and sequencing of the cDNAs coding for human (h) and baboon (b) SP-10 have been reported. To produce large amounts of pure antigen for ongoing studies of the immunogenicity and anti-fertility effects of SP-10, we used an efficient Escherichia coli expression system. The full-length open reading frames for hSP-10 and bSP-10 were placed under the inducible T7 bacteriophage RNA polymerase/promoter system. An in-frame fusion was made such that a His6 stretch was produced at the C terminus of SP-10. Upon induction of gene expression, large amounts of hSP-10 or bSP-10 were synthesized and the recombinant (re-) protein segregated into an insoluble fraction. The protein was then solubilized in 6 M guanidine-HCl and purified by immobilized metal affinity chromatography (IMAC). The yield of purified bSP-10 preparation was approx. 20 μg/ml of culture. Immunoreactivity of the purified re-SP-10 with MHS-10, a monoclonal antibody specific to SP-10, and rabbit polyclonal sera raised against SP-10, indicated that the synthesized antigen was suitable for immunization studies. Four female baboons were then immunized with the re-bSP-10 antigen. Immunoblots using pre-immune and immune sera from these animals indicated that all four baboons produced antibodies that reacted with native SP-10 extracted from human sperm in a manner identical to that of MHS-10, the positive control. Immune sera also stained the acrosome region of human and baboon sperm heads by immunofluorescence. These results demonstrated that the full-length re-bSP-10 antigen was immunogenic in female baboons and generated an immune response which recognized the native antigen on the sperm head, indicating that the recombinant antigen is a suitable vaccine immunogen.

Original languageEnglish (US)
Pages (from-to)189-195
Number of pages7
Issue number2
StatePublished - Sep 30 1994
Externally publishedYes


  • His-tag
  • MHS-10
  • Sperm protein
  • T7 RNA polymerase/promoter
  • baboon
  • human
  • immune response
  • recombinant antigen
  • signal peptide

ASJC Scopus subject areas

  • Genetics


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