In March 2020, the first cases of the human coronavirus disease COVID-19 were registered in Kazakhstan. We isolated the SARS-CoV-2 virus from clinical materials from some of these patients. Subsequently, a whole virion inactivated candidate vaccine, QazCovid-in, was developed based on this virus. To develop the vaccine, a virus grown in Vero cell culture was used, which was inactivated with formaldehyde, purified, concentrated, sterilized by filtration, and then adsorbed on aluminum hydroxide gel particles. The formula virus and adjuvant in buffer saline solution were used as the vaccine. The safety and protective effectiveness of the developed vaccine were studied in Syrian hamsters. The results of the studies showed the absolute safety of the candidate vaccine in the Syrian hamsters. When studying the protective effectiveness, the developed vaccine with an immunizing dose of 5 μg/dose specific antigen protected animals from a wild homologous virus at a dose of 104.5 TCID50/mL. The candidate vaccine induced the formation of virus-neutralizing antibodies in vaccinated hamsters at titers of 3.3 ± 1.45 log2 to 7.25 ± 0.78 log2, and these antibodies were retained for 6 months (observation period) for the indicated titers. No viral replication was detected in vaccinated hamsters, protected against the development of acute pneumonia, and ensured 100% survival of the animals. Further, no replicative virus was isolated from the lungs of vaccinated animals. However, a virulent virus was isolated from the lungs of unvaccinated animals at relatively high titers, reaching 4.5 ± 0.7 log TCID50/mL. After challenge infection, 100% of unvaccinated hamsters showed clinical symptoms (stress state, passivity, tousled coat, decreased body temperature, and body weight, and the development of acute pneumonia), with 25 ± 5% dying. These findings pave the way for testing the candidate vaccine in clinical human trials.
Camelpox is an infectious viral disease of camels reported in all the camel-breeding areas of Africa, north of the equator, the Middle East and Asia. It causes huge economic loss to the camel industry. We developed a live camelpox virus vaccine candidate using an attenuated strain and evaluated its safety, immunogenicity and protective efficacy in camels. The attenuated virus strain was generated from the camelpox wild-type strain M-96 by 40 consecutive passages on the chorioallantoic membrane of 11-day-old embryonated chicken eggs, henceforth called KM-40 strain. Reversion to virulence of the KM-40 strain was evaluated in camels by three serial passages, confirmed its inability to revert to virulence and its overdose administration was also found safe. Studies of immunogenicity and protective efficacy of the candidate vaccine KM-40 strain in camels was carried out using the dose of 5 x 104.0 EID50. Our data showed complete protection against the challenge infection using the virulent wild-type camelpox virus strain M-96 (dose of 105.0 EID50) which was evaluated at 1, 3, 6 and 12 months post vaccination. In summary, our candidate live attenuated egg-based camelpox vaccine strain KM-40 was found safe, protective, and thus has the potential to use safely in field conditions.
In March 2020, the first cases of human coronavirus infection COVID-19 were registered in Kazakhstan. We isolated the SARS-CoV-2 virus from the clinical material from the patients. Subsequently, a whole virion inactivated candidate vaccine, QazCovid-in, was developed based on this virus. To obtain the vaccine, a virus grown in Vero cell culture was used, which was inactivated with formaldehyde, purified, concentrated, sterilized by filtration, and then sorbed on aluminum hydroxide gel particles. The formula virus and adjuvant in buffer saline solution was used as a vaccine. The safety and protective effectiveness of the developed vaccine was studied on Syrian hamsters. The results of the studies showed the absolute safety of the candidate vaccine on the Syrian hamsters. When studying the protective effectiveness, the developed vaccine with an immunizing dose of 5 mcg/dose of a specific antigen protected animals from wild virus at a dose of 104.5 TCID50/ml. The candidate vaccine formed virus-neutralizing antibodies in vaccinated hamsters in titers from 3.3 ± 1.45 log2 to 7.25 ± 0.78 log2, which were retained for 6 months (observation period) in the indicated titers. The candidate vaccine suppressed the replication of the wild virus in the body of vaccinated hamsters, protected against the development of acute pneumonia and ensured 100% survival of the animals. At the same time, no replicative virus was isolated from the lungs of vaccinated animals. At the same time, a virulent virus was isolated from the lungs of unvaccinated animals in relatively high titers, reaching 4.5 ± 0.7 lg TCID50/ml. After challenge infection, 100% of unvaccinated hamsters became ill with clinical signs (stress state, passivity, tousled coat, decreased body temperature and body weight, and the development of acute pneumonia), of which 25 ± 5% were fatal. The findings paved the way for testing the candidate vaccine in humans in clinical trials.
Introduction. This article presents the results of isolation of camel smallpox virus (Poxviridae: Orthopoxvirus: Camelpox virus, CMLPV) and study of its reproductive properties on sensitive biological systems.Material and methods. The epizootic strain M-96 of the virus as well as its attenuated variants KM-40 and KM-70 obtained by sequential passivation were used in the study. Isolation of the pathogen from suspension of biopsy specimens was performed on cell culture and in embryonated chicken eggs (ECEs). All experiments were performed with the number of replications ensuring obtaining reliable results.Results. The CMLPV was isolated from the crusts and pox papules of the skin taken from sick camels (Camelus bactrianus) during an outbreak in various districts of the Mangistau region at the end of 2019. The signs of pathogen reproduction on chorio-allantoic membrane (CAM) were observed from 3 passages. The obtained virus caused formation of pathological changes on the CAM in the form of elevated dot or solid white formations separated from the surrounding tissue, with hemorrhagic foci in the center. The reproductive properties of the isolate on sensitive biological systems were determined in comparison with the epizootic CMLPV strain M-96, isolated earlier in the territory of Kazakhstan during the outbreak 23–24 years ago, as well as its attenuated variants. The isolated virus was given the conventional name M-2020.Discussion. When studied in two sensitive cultivation systems (cell culture and ECEs), strain M-96 and its attenuated variants KM-40, KM-70, which were used in the experiments as a control, demonstrated high infectious activity with titer 4.75-6.75 lg TCID50/cm3, while for the examined isolate M-2020 of CMLPV had the significantly lower values (3.00-4.75 lg TCID50/cm3, p > 0,05).
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