ASSESSMENT OF THE IMMUNOGENICITY AND PROTECTIVE EFFECTIVENESS OF REFLUVAC® IN MICE CHALLENGED WITH A PANDEMIC A/H1N1 INFLUENZA

This article describes the results of a pre-clinical study of immunogenicity and effectiveness of an inactivated pandemic vaccine (Refluvac (R)) on model mice. Mice received two 0.5 ml intraperitoneal inoculations with an interval of 14 days in three doses: containing 10.0, 5.0 and 2.5 mu g HA (hemagglutinin) per animal. As a comparator preparation, the study used a semi-finished product (SP) vaccine diluted with phosphate buffered saline (PBS) to obtain HA concentrations of 5 mu g and 10 mu g. For a control group, the study used PBS as the negative control. We determined the vaccine's protective effectiveness level by analyzing its response in animals challenged with a pandemic A/California/7/09 (H1N1) pdm09 virus. We assessed the immunogenicity of the vaccine by examining the mean geometric titre (GMT) of antibodies against the influenza virus as measured by hemagglutination-inhibition test (HAI). In the course of testing the GMT, we noted a dependence of the concentration of antibodies in serum on the vaccine's antigen load. The highest GMT was observed in the group of mice vaccinated with a HA load of 10.0 mu g - it amounted to 278.6 (95% CI, 135.6 to 572.4). We established a high tolerability of the vaccine tested. Our study shows that Refluvac (R) yields a high degree of protectivity against influenza A/H1N1 and prevents clinical signs, death or accumulation of influenza virus in the organs of vaccinated animals. There were deaths and clinical signs including general depression, hypodynamia and anorexia in the negative control group. The results of our study were used for the clinical study of the first Kazakhstan-produced Refluvac (R) vaccine against pandemic A/H1N1 influenza virus.