Abstract
Induction of an appropriate immune response against gonadotrophin releasing hormone (GnRH-I) disrupt fertility, reduce fecundity and regress tumours of reproductive system.To disrupt fertility a plasmid DNA vaccine was engineered coding eight repeats of GnRH-I and eight T-helper epitopes. Translation efficiency of the vaccine was evaluated in undifferentiated COS1 cells and found to release GnRH-I fusion protein in culture supernatant. Swiss albino female mice (N=24) were immunized with 50μg plasmid DNA construct in study weeks 0, 3, 6, 9 and 12. Group 2 mice were primed with the plasmid DNA in hemagglutinating virus of japanese envelope (HVJE) vector and subsequent boosts were carried out in phosphate buffer saline. Group 3 mice were immunized with the plasmid DNA in non-ionic surfactant vesicles (NISV) and Group 1 was served as untreated control. The effect of immunization was studied in terms of anti-GnRH-I antibody response (OD value at A540 ± SD), suppression of ovarian folliculogenesis, altered uterine histoarchitecture and impaired fertility in vivo in mating trials. In study week 24 OD values of anti- GnRH-I antibody response were 0.982 ± 0.231 in Group 3 mice, followed by 0.783 ± 0.191 in Group 2 in comparison with no response in Group 1 controls (0.237 ± 0.147). Results of mating trials showed conception failure in vaccinated mice; 51, 18 and 05 pups were seen in the uteri of Groups 1, 2 and 3 mice respectively. There was significant (p>0.001) reduction in the weight of ovaries in Group 2 (8.50 ± 2.38 mg) and Group 3 (7.25 ± 0.95 mg) mice compared to Group 1 control (15.00 ± 1.41 mg). Significant reduction of ovarian folliculogenesis was seen in Group 2 (p>0.001) and Group 3 mice (p>0.01). In conclusion, the plasmid DNA vaccine delivered in female mice with HVJE and NISV induced significantly (p>0.001) higher levels of anti-GnRH-I antibody response, suppressed ovarian and uterine function and impaired fertility in vivo.
Highlights
It has been over two decades since plasmid DNA vaccines were described as an inducer of effective immune response [1]
gonadotrophin releasing hormone (GnRH-I) is the releaser of both luteinizing hormone (LH) and follicle stimulating hormone (FSH) and is a key peptide of reproduction [8]
Results of sequence analysis revealed that the vaccine construct containing eight repeats of GnRH-I, eight T-helper epitopes, an N terminal V5 epitope and a histidine tag before stop codon (Figure 1)
Summary
It has been over two decades since plasmid DNA vaccines were described as an inducer of effective immune response [1] This type of vaccine has since been shown to hold promise for the treatment of cancer [2], allergies [3], prevention of infectious diseases [4], neutralization of fecundity of mammals [5,6] and suppression of fertility [7]. Immunoneutralization of GnRH-I using GnRH-I peptide carrier conjugates is inefficiet in terms of variable chemical conjugation and heterogeneity of antigen preparations [14]. These problem can partially be obviated by using GnRH-I fusion proteins [9]. The level of GnRH-I immunoneutralisation was evaluated by means of anti-GnRH-I antibody responses, suppression of ovarian folliculogenesis and disruption of fertility in adult female mice
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