Repeated Dose Toxicity Study of a Live Attenuated Oral Cholera Vaccine in Sprague Dawley Rats

Challenges and Considerations in Selecting Animal Models for Evaluating a Live, Cold-Chain-Free, Dual-Use Vaccine (MyChol) for Diarrhoeal Diseases: A Comprehensive Review

Diarrhoeal diseases are the second leading cause of death for children under 5 years old in 69 low- and middle-income countries, with an annual economic burden of US$ 4 billion and over 525,000 lives lost. Cholera and enterotoxigenic Escherichia coli (ETEC) traveller's diarrhoea are major diarrhoeal diseases caused by Vibrio cholerae (O1 and O139 serogroups) and ETEC, which have similar pathogeneses and can co-infect. There is no exclusive vaccine for ETEC, but cholera vaccines containing the cholera toxin B (CT-B) component offer short-term cross-protection. However, licensed oral cholera vaccines are expensive due to cold-chain supplies and the need for multiple doses. A cost-effective, dual-protection, live, cold-chain-free vaccine is, therefore, required for vaccination campaigns in low-resource settings, and MyChol - a prototype cold-chain-free live attenuated cholera vaccine, targeting V. cholerae O139 and ETEC H10407 - was developed in this context. The vaccine was evaluated in three animal models (Sprague Dawley [SD] rats, BALB/c mice and New Zealand white rabbits) for safety, colonisation capacity, reactogenicity and immunogenicity against challenge strains. In suckling mice, MyChol displayed high colonisation potential compared to unformulated VCUSM14P (the vaccine candidate) and wild-type O139. In the acute toxicity assessment, the SD rats with the highest MyChol dose (1 × 107 colony-forming unit [CFU]/kg) demonstrated no adverse effects or mortality. Mice vaccinated with MyChol exhibited elevated antibody levels, including anti-CT, anti-heat-labile enterotoxin (LT), anti-CT-B and anti-LT-B. Anti-CT antibodies neutralised LT toxin in ETEC H10407 in challenge studies and cross-protected against ETEC H10407 in both mice and rabbits, preventing weight loss and diarrhoea. Ileal loop experiments in rabbits and BALB/c mice showed no reactogenicity. This review, based on our previous research, therefore provides valuable insights into improving the selection of animal models to advance preclinical evaluations of diarrhoeal vaccines.

Effects of Repeated Doses of the Vero Cell Vaccine (SARS-Cov-2 Inactivated Vaccine) on Renal Functions in Balb/C Albino Mice

Objective

Many of the vaccines developed for COVID-19 have been approved for clinical emergency use before their safety and preclinical studies have been completed. The main aim of this study was to investigate the effects of an inactivated SARS-CoV-2 virus vaccine (Vero cells) on renal function in Balb/C Albino mice.

Methods

21 healthy, 6-8 week old BALB/c male mice were divided into three equal groups, and 0.10 mL of intramuscular saline equal to the vaccine dose volume was administered to the first group. To the second group, a single dose of 0.10 mL 120 U of Vero cell inactive SARS COV-2 vaccine was administered intramuscularly. Group 3 received two consecutive doses of 0.10 mL 120 U intramuscular Vero cell inactive SARS COV-2 vaccine, 14 days apart. After administration, the clinical status, fecal and urine status, nutritional status and kidney histopathology of the mice were evaluated.

Results

It was determined that no acute toxic symptoms were observed in the mice administered the vaccine, they were in good condition, and there was no significant stimulatory reaction related to the vaccine in the tissues of the injected local area. There was no difference in feed consumption, water consumption, and body weight gains between the control group, the groups that received a single dose of vaccine, and the groups that received two doses of vaccine (p>0.05). No difference was found between the groups when urine and feces amounts were compared (p>0.05). No difference was found between the groups when urinary urea, creatinine, and serum BUN, creatinine levels were compared (p>0.05). No difference was found in the histopathological evaluation of the kidneys between the groups (p>0.05).

Conclusion

In conclusion, single or repeated injections of the SARS-CoV-2 vaccine (Vero cells) into mice were found to have no adverse effects on the animals' overall clinical health, performance abilities and kidneys.

SARS-CoV-2 inactivated vaccine (Vero cells) shows good safety in repeated administration toxicity test of Sprague Dawley rats

The outbreak of COVID-19 has posed a serious threat to global public health. Vaccination may be the most effective way to prevent and control the spread of the virus. The safety of vaccines is the focus of preclinical research, and the repeated dose toxicity test is the key safety test to evaluate the vaccine before clinical trials. The purpose of this study was (i) to observe the toxicity and severity of an inactivated SARS-CoV-2 vaccine (Vero cells) in rodent Sprague Dawley rats after multiple intramuscular injections under the premise of Good Laboratory Practice principles and (ii) to provide a basis for the formulation of a clinical trial scheme. The results showed that all animals in the experimental group were in good condition, no regular changes related to the vaccine were found in the detection of various toxicological indexes, and no noticeable stimulating reaction related to the vaccine was found in the injected local tissues. The neutralizing antibodies in the low- and high-dose vaccine groups began to appear 14 days after the last administration. In the negative control group, no neutralizing antibodies were observed from the administration period to the recovery period. Therefore, the repeated administration toxicity test of the inactivated SARS-CoV-2 vaccine (Vero cells) in Sprague Dawley rats showed no obvious toxic reaction. It was preliminarily confirmed that the vaccine can stimulate production of neutralizing antibodies and is safe in Sprague Dawley rats.

Repeat-Dose Toxicity Study Using the AFPL1-Conjugate Nicotine Vaccine in Male Sprague Dawley Rats

Tobacco smoking is the cause of 20% of Canadian deaths per year. Nicotine vaccines present a promising alternative to traditional smoking cessation products, but to date, no vaccine has been able to move through all phases of clinical trials. We have previously demonstrated that the AFPL1-conjugate nicotine vaccine does not induce systemic or immunotoxicity in a mouse model and that a heterologous vaccination approach is more advantageous than the homologous routes to inducing mucosal and systemic anti-nicotine antibodies. The purpose of this study was to confirm the safety profile of the vaccine in a repeat-dose toxicity study. The heterologous vaccination strategy was again used, and Sprague Dawley rats were administered a dose five times greater than in our previous studies. Physiological conditions, food and water consumption, body temperature, injection site inflammation, relative weights of organs, histopathology, and blood chemistry and hematology were evaluated during the course of the vaccination period to determine the safety of the vaccine. The AFPL1-conjugate nicotine vaccine did not induce clinically relevant changes or induce symptoms that would be associated with toxicity, making it a promising candidate for future investigations.

Repeated dose toxicity evaluation of a cold chain-free, live, attenuated oral cholera vaccine in Sprague Dawley rats

The repeated dose toxicity of a prototype cold chain-free, live, attenuated oral cholera vaccine containing 5 × 10⁶ CFU/mL of the VCUSM14P strain was evaluated in Sprague Dawley (SD) rats (single dose administered daily for 30 days) to ascertain its safety for clinical use. Repeated dose toxicity studies for cholera vaccines in the literature have administered 2 or 3 fixed doses at 7, 14, 21 or 69 day intervals. The present study reports an evaluation of 30 repeated doses of cholera vaccine administered at three different concentrations (Group II (1.25 × 10⁶ CFU), Group III (2.5 × 10⁶ CFU) and Group IV (5 × 10⁶ CFU)) in SD rats. The liquid vaccine was administered orally to the rats with the respective dose every day, and normal saline was administered to the control group (Group I). No significant difference (P > 0.05) was observed in the body weights and biochemical parameters of the rats after 15 and 30 repeated doses compared to those of the control group. However, compared to those of Group I, a significant increase (P < 0.05) in the organ to body weight ratios of the lungs, ureter, liver, kidney, heart and spleen was found in G-II, G-III and G-IV. In the haematological analysis, a significant increase in the WBC was observed in G-II and G-IV compared to that in G-I. The histopathological findings indicated mild to moderate degeneration in the liver, kidney, heart and spleen in the treated rats. Mild to moderate lymphocytic infiltration in the lungs was observed in the G-II and G-III rats, and severe infiltration was observed in the G-IV rats. These histopathological findings may be attributed to the 30 doses of vaccine given in daily succession without an interval. In the acute toxicity study, a single dose of vaccine up to 10 × 10⁶ CFU did not cause any adverse effects and lethality in SD rats.

A 6-week oral toxicity study of oral cholera vaccine in sprague-dawley rats

The present study was carried out to examine the toxicity and target organs of oral cholera vaccine (OCV) after repeated oral administration in Sprague-Dawley rats for 6 weeks (3 administrations, once every 2 weeks). OCV is an inactivated oral cholera vaccine that contains Vibrio cholerae and confers protection against cholera caused by V. cholera serogroups O1 (Inaba and Ogawa serotypes) and O139 (strain 4260B). The animals were orally administered either OCV placebo (negative control) or OCV at a dose equivalent to 240 times the anticipated human dose. Throughout the administration period, no significant change was detected in clinical signs, body weight, food or water consumption, urinalysis results, hematological and clinical biochemistry test results, organ weights, necropsy, or histopathological examination results. Minor changes were found in hematological and clinical biochemistry tests; however, these changes were within normal ranges. The above results suggest that oral administration of OCV in rats did not induce any toxicologically meaningful changes, and the target organs could not be determined. This study was conducted in accordance with the guidelines established by Good Laboratory Practice (2009-183, KFDA, December 22, 2009) and the OECD Principles of Good Laboratory Practice (1997).

Toxicological Assessment of the Cochleate Derived from Neisseria meningitidis Proteoliposome in Sprague Dawley Rats

BACKGROUND

The AFCo1 cochleate is a potential novel adjuvant derived from Neisseria meningitidis B proteoliposome.

AIM

The aim was to assessing the safety of AFCo1 by single and repeated doses in Sprague Dawley rats.

MATERIALS AND METHODS

Rats were grouped for treatment with AFCo1, placebo formulation or control. The first study was a single intranasal dose of 100 μl and monitoring body weight, water, and food intakes as well as clinical symptoms. Fourteen days later the rats were killed and anatomopathological studies were conducted. In a second study, four similar doses of the test substance were instilled every 5 days. Clinical observations were carried out as for the single dose study and a number of rats from each group were killed 3 and 14 days after the last dose in order to conduct hematological, hemochemical, and anatomopathological studies.

RESULTS

No variable showed differences of toxicological relevance; the histological changes found were mild and similarly frequently in the three groups. According to the irritability index calculated form histology of the nasal region, AFCo1 was also classified as nonirritating.

CONCLUSION

AFCo1 is potentially safe for human use by nasal route as evidenced by the absence of local and systemic signs of toxicity in Sprague Dawley rats.