Developmental and reproductive toxicity testing of vaccines

The majority of new preventative and therapeutic vaccines are now assessed for developmental toxicity according to guidelines issued by the FDA in 2006. Despite the absence of confirmed effects in humans, vaccines are frequently suspected of having adverse side-effects on the development of children. Such suspicions are perhaps unavoidable considering the extremely widespread use of vaccines. The preclinical developmental toxicology studies are designed to assess possible influences of each component of the vaccine formulation-and the induced antibodies-on the development of the conceptus, neonate and suckling organism. Immune modulation by a vaccine or an adjuvant could, for instance, affect the outcome of pregnancy by interfering with the natural shift in immune balance of the mother during gestation. Maternal immunoglobulins are transferred from the mother to the offspring in order to confer passive immunity during early life. This maternal antibody transport is prenatal in humans and monkeys, but tends to be delayed until after birth in other species. Therefore, a suitable model species needs to be chosen for preclinical studies in order to ensure exposure of the foetus to the induced maternal antibodies following vaccination. Rabbits are the best laboratory model for prenatal immunoglobulin transfer, but rodents are more practical for the necessary postnatal investigations. Non-human primates are the only appropriate models for the testing of vaccines that are not immunogenic in lower species. It is advisable to test new adjuvants separately according to the ICH S5(R2) guidelines. Preclinical paediatric investigations are not currently required for vaccines, even though most vaccines are given to children. Other areas of regulatory concern include developmental immunotoxicity and effects on the preimplantation embryo. Because of the limitations of the available animal models for developmental toxicity testing, pharmacovigilance is essential.     

Reproductive toxicity testing for pharmaceuticals under ICH

Reproductive toxicity testing of drugs is performed as a 2- or 3-segment package. The choice of species for routine studies with small molecule drugs is essentially limited to the rat, rabbit, mouse and minipig. The lack of alternative species is a threat to the successful screening of drugs for teratogenicity. A proposed revision of the ICH M3 guideline addresses contradictions concerning the timing of the various reproductive and juvenile studies. This M3 draft, however, raises questions concerning the confidence that can be attributed to preliminary embryotoxicity studies with as few as six females per group. The detection of reproductive hazards could be improved by implementing methods in routine use for the testing of chemicals, such as double staining of fetuses and primordial follicle counts. Modern imaging techniques hold promise for application in the morphological examination of fetuses. An assessment of developmental immunotoxicity should be included in any future revision of the reproductive toxicity guidelines.     

Reproductive toxicity of ofloxacin

The reproductive toxicity of (+/-)-9-fluoro-2, 3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de] [1,4]benzoxazine-6-carboxylic acid (ofloxacin, Tarivid), a new antibacterial agent, was investigated in rats and rabbits after oral administration. Neither the male or female fertility nor the reproductive performance of the rats was affected by doses of up to 360 mg/kg. Ofloxacin elicited no evidence of teratogenicity when administered orally during the period of organogenesis to pregnant rats at doses of up to 810 mg/kg, or to pregnant rabbits at doses of up to 160 mg/kg. However, the female rats receiving 810 mg/kg showed salivation, dirty hair coats, soft stools, and decreases of body weight and food intake. The fetuses in the higher dose groups exhibited decreased body weight and retardation of ossification, and those in the highest dose group showed increased mortality and skeletal variations (cervical ribs, shortened 13th ribs). Further investigation of the fetal skeleton revealed that the critical period of the occurrence of skeletal variations was on days 9 and 10 of gestation. The occurrence of cervical ribs and shortened 13th ribs was not an indicator of teratogenicity when ofloxacin was administered at doses of up to 1600 mg/kg during the critical period. Moreover, the shortening of the 13th ribs was the only type of retardation of ossification degree. Decreases of maternal body weight and food intake, and increased mortality of fetuses were observed in rabbits at a dose of 160 mg/kg. In a perinatal and postnatal toxicity study in rats using doses of up to 360 mg/kg, no adverse effects were observed.     

Reproductive toxicity studies of ademetionine

S-Adenosyl-L-methionine sulphate-p-toluene sulphonate (ademetionine, SAMe), a donor of methyl groups, was examined for effects upon embryofoetal toxicity following both premating treatment and treatment during pregnancy and for peri- and post-natal toxicity in the rat at dosages of 0, 100, 200 and 400 mg/kg/d SAMe ion by subcutaneous or intravenous administration. Embryofoetal toxicity was also examined in the New Zealand White rabbit at dosages of 0, 10, 20 and 40 mg/kg/d SAMe by intravenous administration. Treatment was considered to be without adverse effect upon any of the reproductive parameters examined on either F0 or on the untreated F1 generations. There was no indication that treatment adversely affected the litter parameters including the incidences of malformations, anomalies and skeletal variants. Some slight changes in the activity of the F1 females derived from F0 animals given 400 mg/kg/d were considered to be of minimal importance. In contrast to the above, adverse effects upon the parents were noted at 400 mg/kg/d including local tissue reaction at the injection sites and retardation of body weight gain. In the intravenous studies some rigidity and dyspnoea were noted following administration. Following subcutaneous premating treatment there was also evidence of histopathological change to the kidney of the female rat. Increased water consumption was noted in this latter study and amongst females rearing offspring in the embryo foetal toxicity study in which the compound was administered intravenously. At the lower dosages administered to the rat some local tissue reaction was evident as was some retardation of body weight gain, minimal at the lowest intravenous dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

盐酸丁螺环酮的围产期毒性作用

盐酸丁螺环酮是一种具有较强抗焦虑作用的新药，大鼠围产期及哺乳期毒性试验结果表明。本品对Ｃｒｉ：ＣＤ大鼠无致畸胎作用，剂量高于１２ｍｇ／ｋｇ时对母鼠及胎仔有一定的性作用，其无作用剂量为每天给药２ｍｇ／ｋｇ，该剂量相当于人临床用量的３倍，提示就生殖一毒性而言，盐酸丁螺环酮在人临床用量的剂量范围内使用是比较安全的。     

Reproductive toxicity studies of rentiapril

(2R,4R)-2-(o-Hydroxyphenyl)-3-(3-mercaptopropionyl)-4- thiazolidinecarboxylic acid (rentiapril, SA 446), an orally active inhibitor of angiotensin converting enzyme, was examined for effects upon general reproductive performance, for embryofoetal toxicity and for peri- and postnatal toxicity in the rat at dosages of 0, 20, 100 and 500 mg/kg/d. Embryofoetal toxicity was also examined in the New Zealand White rabbit at dosages of 0, 1, 2 and 4 mg/kg/d. The compound was administered by gastric intubation. Prolonged treatment at 100 and 500 mg/kg/d during the fertility study was associated with some slight depression of body weight gain of males. Body weight gain of females during gestation was significantly depressed at 500 mg/kg/d. There was salivation in both sexes at 500 mg/kg/d and also in males receiving 100 mg/kg/d. Following this prolonged treatment in the fertility study. Fo male and female kidney weights were increased at all dosages. Although there was no obvious effect upon fertility there was an increased incidence of total litter loss at 500 mg/kg/d and mean pup weights to day 21 post partum were reduced at this dosage and at 100 mg/kg/d with delays in the attainment of some of the developmental landmarks. In the rat treatment at 500 mg/kg/d from day 7 to 17 of pregnancy did not adversely effect embryofoetal development. Subsequent development and reproductive performance of the F1 offspring was also unimpaired. During this treatment period signs of salivation were seen at 500 mg/kg/d. Slight retardation of maternal body weight gain was noted at 500 mg/kg/d and at 100 mg/kg/d but not at 20 mg/kg/d.(ABSTRACT TRUNCATED AT 250 WORDS)     

芥子气的生殖毒性

芥子气是在多次战争中使用的最有效的化学毒剂之一。作为典型的双功能烃化剂,芥子气的急性毒性和中毒人员的临床救治已成为人们关注的重点,而对芥子气给环境造成的长期影响和中毒人员的远后效应关注不足。作为已知的致突变和致癌剂,芥子气的生殖毒性尚不明确。本文简要介绍国内外关于芥子气生殖毒性研究现状。     

Reproductive toxicity of acrylamide-treated male rats

Acrylamide content is elevated in fried, baked and heat-processed starchy foods. The present experiment was conducted to investigate the reproductive toxicity of oral acrylamide in male rats. Thirty weaned SD male rats of 21-day-old were randomly allotted to three groups, and acrylamide was administered to each group at doses of 0, 5 and 10 mg/kg-d for 8 consecutive weeks. The results indicated that the growth of rats treated with acrylamide was retarded (P < 0.05), but relative weights of testes and epididymides compared to body weight were not significantly different (P > 0.05). Our results also indicate that the epididymal sperm reserves decreased significantly (P < 0.05), suggesting partial depletion of germ cells. In addition, histopathologic lesions were also present in the testes of treated rats. Furthermore, distinct expression patterns of sGC heterodimers were observed in this animal model. This may suggest different physiologic roles for sGC subunits in spermiogenesis and steroidogenesis.     

Investigating toxicity specific to adjuvanted vaccines

In an attempt to understand the unique toxicity of adjuvanted vaccines, we studied how toxicity develops over time following vaccine administration. In addition to on- and off-target toxicity typically observed with general pharmaceuticals, we observed toxicity associated with both the generation and the broad action of effectors (antibodies and/or cytotoxic T lymphocytes, CTLs). The impact on effector generation appears to be related to local tolerance specific to the adjuvant. The vaccine immune response by effectors serves to demonstrate species relevance as outlined in the recent WHO guideline on the nonclinical evaluation of adjuvanted vaccines. When regarded as pharmaceuticals that function at sites of local administration, adjuvants have inherent on- and off-target toxicity. On-target toxicity of the adjuvant is typically associated with effector generation, and could vary depending on animal species. Therefore, the use of species with sensitivity to adjuvants described in the WHO guidelines is required to evaluate the toxicity of the vaccine associated with effector generation. Changes in safety pharmacology endpoints would be considered off-target and further studies are conducted only if changes in these endpoints are observed in nonclinical or clinical studies. Thus our decision tree does not recommend the routine conduct of stand-alone safety pharmacology studies.     

Reproductive toxicity studies with oxybutynin hydrochloride

Oxybutynin hydrochloride, an anti-cholinergic/anti-spasmodic agent, was examined for its effect on fertility and peri-post natal development in the rat and its embryotoxic potential in the rat and rabbit. In the rat effects on reproductive performance included a slight increase in the incidence of foetal malformations, extended gestation period and impaired post natal performance of offspring. These findings occurred at dosages clearly associated with maternal toxicity. Oxybutynin hydrochloride did not exert an effect on reproductive processes in the rat at lower dosages or on embryonic and foetal development in the rabbit.     

Reproductive toxicity in acrylamide-treated female mice

We investigated the reproductive toxicity of acrylamide in female mice. The results from immunohistochemistry provided evidence that nitric oxide synthase (NOS) signaling was involved in the process of follicular development and atresia. Oral administration of acrylamide to female mice led to significantly reduced body weights, organ weights and the number of corpora lutea (P < 0.05). Serum progesterone concentrations were significantly reduced (P < 0.05) concomitant with the increasing doses of acrylamide; however, 17β-estradiol (E2) concentrations were unchanged with treatment. Measurement of NOS activities indicated that total NOS (TNOS), iNOS and eNOS activities were significantly increased (P < 0.05) with increasing doses of acrylamide. The results from in vitro study indicated that acrylamide reduced the viability of mouse granulosa cells in a dose-dependent manner. In summary, acrylamide affected bodily growth and development, as well as reproductive organs, the number of corpora lutea and progesterone production in female mice, possibly acting through the NOS signaling pathway.     

Reproductive toxicity of ergot alkaloids in mink

Ergot alkaloids are-synthesized by fungi of the Claviceps family that infect rye as well as other cereals and grains. Since a portion of the ranch mink diet is cereal, mink are at a risk of being exposed to ergot alkaloids. This study was performed to determine the reproductive toxicity of ergot alkaloids derived from ergot-contaminated oats in mink. Four groups of 12 female mink each were fed diets containing 0, 3, 6 or 12 ppm ergot alkaloids from 2w prior to the breeding season until the kits were approximately 33-d old (133 d). Females were mated with untreated males. Ergo talkaloids caused a transient decrease in feed consumption, but body weights were unaffected. The gestation period of the mink in the 6 ppm group was longer compared to controls. The number of mink whelping varied significantly with 9 mink whelping each in the control and 3 ppm groups compared to 4 mink in the 6 ppm group and 1 in the 12 ppm group. Ergot alkaloids had a significant effect on kit survivabilitywith no kits surviving in the 12 ppm group. Serum prolactin was significantly depressed in the 3 ergot alkaloid groups compared to the control group. This study indicated that ingestion of ergot alkaloids at 3 ppm or higher resulted in reproductive toxicity in mink.     

Reproductive toxicity and toxicokinetics of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Possible effects on the next generation after long-term exposure (subcutaneous administration) of male rats to very high doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were studied. Two dose regimes were applied: TCDD-25 (initial dose: 25 g/kg body wt; maintenance dose: 5 g/kg body wt, once weekly) and TCDD-75 (initial dose: 75 g/kg body wt; maintenance dose: 15 g/kg body wt). Male rats were treated for 10 weeks before mating and then throughout the entire 12 week mating period. They were mated to unexposed virgin females. One group of pregnant females was used for teratological evaluations, and another group was allowed to deliver. No significant differences were observed in the number of implantations or fetuses per litter, and resorption rate, and fetal weight between the controls and TCDD-treated groups. No gross-structural anomalies occurred in any of the fetuses sired by TCDD-treated males. In the TCDD-25 group an increased frequency of two types of variations was observed which also occur in controls: incompletely ossified fingers (TCDD-25=5.1%, controls=2.6%), and incompletely ossified ossa zygomatica (TCDD-25=1.8%, controls=0.5%). In the TCDD-25 group a slight but statistically significant increase was observed in the rate of stillbirths (TCDD-25=1.3%, controls=0.1%), apparently due to an unusually low frequency occurring in the controls (overall historical controls=0.6%). There was no difference in postnatal mortality (TCDD-25=1.3%, controls=1.3%). Taken together, despite the very high doses of TCDD used, the data do not provide evidence for biologically significant paternally-mediated developmental toxicity in the fetuses and newborn.     

Reproductive toxicity and toxicokinetics of 2,3,7,8-tetrachlorodibenzo-p-dioxin

The effects of a single dose of TCDD on the testis were studied in rats. The animals were treated (subcutaneously) once with TCDD doses of 0, 0.5, 1.0, 3.0, 5.0 g/kg body weight. Doses of 3.0 or 5.0 g TCDD/kg reduced the number of spermatids/testis significantly (60% of the controls). Electron microscopic inspection revealed that both doses led to a dissolution on the germinal epithelium. Altered germ cells at all developmental stages occurred in all testes evaluated. Doses of 0.5 or 1.0 g TCDD/kg did not induce any effects in the testis; therefore, under these experimental conditions of single exposure to rats the dose of 1.0 g TCDD/kg can be considered as NOAEL.     

Reproductive toxicity of caffeine in Musca dosmestica

Marked changes in fecundity were noticed in houseflies fed caffeine in the diet. Partial treatment of male and female flies with caffeine also altered the oviposition pattern. Hatchability of the eggs was reduced significantly by caffeine. Concomitant with the oviposition effect, ovarian growth was retarded, resulting in abnormal ovaries and malformed eggs. Histological studies of growth-inhibited ovaries revealed that differentiation of the oocytes was blocked. Caffeine-fed female flies showed an accumulation of hemolymph portein. In contrast, caffeine-fed male flies showed a decrease in hemolymph protein compared with controls. Several changes in the electropherogram of hemolymph protein was observed in caffeine-treated flies. Biochemical analyses of ovaries isolated from caffeine-fed flies showed that they had less RNA and protein than controls.     

甲胺磷对雄性小鼠的生殖毒性

本文采用一组试验方法对有机磷杀虫剂甲胺磷的雄性小鼠生殖毒性进行研究。以0.2,0.8和3.2mg/kg ig染毒小鼠,观察到精子活动率下降、畸形精子增多、精子线粒体酶活性下降以及睾丸组织细胞结构改变,并呈剂量-反应关系。甲胺磷对雄性小鼠生殖细胞具有潜在诱变能力,并可通过多种途径干扰生精细胞的分化和代谢。建议中毒的育龄男子定期检产精液直至结果恢复正常方可生育后代。     

Reproductive toxicity of methyl isocyanate in mice

The effects of methyl isocyanate (MIC) vapor on pregnancy and fertility were studied in mice in view of the reported increase in reproductive complications in Bhopal following the December 3, 1984, accident. The whole-body exposure of mice to 9 and 15 ppm MIC for 3 h on d 8 of gestation led to resorption of greater than 80% of implants. In more than 75% of MIC-exposed animals, all implants were lost. At these concentrations, MIC did not cause external malformations. However, there was evidence of an increase in visceral abnormalities and a decrease in fetal and placental weights and in fetal skeleton sizes. MIC disturbed the estrus cycle and decreased the mating and pregnancy rate of female mice. The mating performance of MIC-exposed male mice was also decreased. Exposure to MIC increased serum corticosterone levels of male and nonpregnant female mice. MIC exerted no significant effects on serum corticosterone and progesterone levels of pregnant mice if the pregnancy was retained but caused a significant decrease in the serum levels of these two hormones in animals that lost all the implants. These studies show that the effects of MIC in mice mimic many of the reproductive complications in Bhopal. The mechanism of the reproductive toxicity of MIC remains to be identified.