Parenteral administration of GnRH constructs and adjuvants: Immune responses and effects on reproductive tissues of male mice

Abstract

a b s t r a c tTwo gonadotrophin releasing hormone (GnRH) constructs prepared by either chemical conjugation to keyhole limpet hemocyanin (GnRH-KLH) or as an expressed recombinant fusion protein (Multimer) were evaluated with or without adjuvants (immunostimulating complexes, ISCOMs, or cytosine-phosphateguanosine oligodeoxynucleotides, CpG ODNs). After subcutaneous administration to Balb/c male mice at Weeks 0, 2 and 4, these preparations were assessed for induction of immune responses and effects on reproductive organs. GnRH-KLH plus ISCOMs formulation induced strong IgG immune responses from Week 4 through Week 12 resulting in consistent reproductive organ atrophy by Week 12 after subcutaneous administration. GnRH-KLH plus CpG ODNs generated immune responses but no atrophy of reproductive tissues by Week 12. Multimer plus ISCOMs induced poor immune responses and no effects on reproductive tissues by Week 12. In the absence of additional adjuvant, none of the GnRH constructs induced reproductive organ atrophy. GnRH-KLH induced stronger immune responses when formulated with ISCOMs or CpG ODN compared to Multimer. GnRH-KLH with ISCOMs could be an effective colloidal alternative for emulsion GnRH vaccine formulations.

The immune profile induced is crucial to determine the effects of immunocastration over gonadal function, fertility, and GnRH‐I expression

“…Although there are studies that describe the effects of immunocastration using different formulations over animal reproductive functions, scarce is the evidence on the effects of different immune response profiles over blockage of reproductive activity, as well as over the GnRH‐I levels and its receptor expression.…”

Immunogenicity of a Recombinant Gonadotropin-releasing Hormone Associated to the B Subunit of Escherichia coli Heat-labile Enterotoxin Expressed in Pichia pastoris and Escherichia coli Platforms

“…Since it is a decapeptide with low molecular weight, it is necessary to use strategies capable of stimulating the immune system to generate a response against the hormone [14]. These strategies include the construction of molecules containing multiple copies of the peptide and / or fusion with carrier proteins such as bovine serum albumin (BSA), tetanus toxoid (TT), ovalbumin (OVA) [15]. However, many carrier proteins are not well defined (e.g.…”

Contraception and immunocastration vaccines. Use in veterinary medicine

“…Adjuvation with immunostimulating complexes (ISCOMs) (lipophilic saponins that form a box-like structure with the antigen) is another alternative for GnRH-KLH immunization. Preclinical studies shown the induction of elevated anti-GnRH response in immunized mice (56).…”