Evaluation of infertility efficacy of theE. coliexpressed STF2-GnRH vaccine in male cats

Abstract

Gonadotropin-releasing hormone (GnRH) is secreted from the hypothalamus and anti-GnRH antibodies are not formed under normal conditions. However, administration an excess of recombinant GnRH protein results in the formation of anti-GnRH. We evaluated the efficacy of the recombinant Salmonella typhimurium flagellin fljB (STF2)-GnRH vaccine in inducing infertility in 17 intact male cats. The first vaccination and a boosting vaccine was injected for examination. Serum was obtained from blood collected at monthly intervals and anti-GnRH antibodies and testosterone concentrations were determined. Six months after the vaccination, testicular samples are obtained and used for histological examination. Compared with sham control group, the injection groups showed an increase in anti-GnRH antibody titers and testosterone concentrations tended to be reduced in the injection groups and increased in the control group. Histological evaluations and Johnsen's testicular biopsy scores revealed testicular hypoplasia in the 2 injection groups. Consequently, normal sexual maturation with sperm production was observed in the control group. In contrast, the cats that received the GnRH vaccine showed weak (2 of 7 cats) or moderate (4 out of 7 cats) dose-dependent infertility effects. On the basis of the results, the STF2-GnRH vaccine was identified to be effective in inducing infertility in male cats. The results of this study thus indicate the possibility of immunological castration targeting feral cats.

Induction of immunocontraceptive effects in both male and female mice immunized with GnRH vaccine

“…It has been suggested that low testosterone levels in male mice can lead to testicular atrophy of their testes (Han et al., 2016; Yao et al., 2018). In other studies, the GnRH vaccine reduced testosterone levels and inhibited spermatogenesis in cats (Dunshea et al., 2001; Lee et al., 2019). Therefore, our results indicated that the GnRH vaccination could decrease the synthesis of testosterone and lead to both inhibition of sperm generation and atrophy of the testis in male mice during our experimental periods.…”

Application of a high-quality, high-volume trap–neuter–return model of community cats in Seoul, Korea

“…If female cats that are less than 2 kg were released without surgery, it is likely that they will become more fertile and compensate for the lack of breeding in areas where a TNR strategy is implemented . Although various studies have investigated the use of non-surgical contraceptive methods, such as administration of the gonadotropin-releasing hormone (GnRH) vaccine, which have relatively fewer restrictions with regards to the weather or age of cats, it is not yet a feasible alternative to surgery (Levy, 2011;Levy et al, 2011;Fischer et al, 2018;Lee et al, 2019).…”

Immunogenicity and contraceptive efficacy of recombinant fusion protein encompassing Sp17 spermatozoa‐specific protein and GnRH: Relevance of adjuvants and microparticles based delivery to minimize number of injections

“…The antibody titres against recombinant Sp17 C ‐GnRH 2 , TT‐KK‐Sp17 C and GnRH‐BSA conjugates were low in pregnant mice as compared to those which failed to conceive during first and second mating (Figure ). Immunization of dogs and cats with GnRH‐based contraceptive vaccine has also shown that some of the immunized animals failed to generate adequate antibody titres, categorized as “non‐responders,” in spite of giving booster injection . It is likely that the immunized female mice that became pregnant on mating have failed to generate adequate antibody titres and may be categorized as “non‐responders.” However, the reason for failure to generate adequate antibody titres by few of the immunized animals in the inbred population of mice is not clear.…”

“…Immunization of dogs and cats with GnRH-based contraceptive vaccine has also shown that some of the immunized animals failed to generate adequate antibody titres, categorized as "non-responders," in spite of giving booster injection. [47][48][49] It is likely that the immunized female mice that became pregnant on mating have failed to generate adequate antibody titres and may be categorized as "non-responders. "…”