Experimental study of early protective action of live influenza vaccine against heterologous influenza infection

BACKGROUND: The live influenza vaccine is an effective means of combating influenza infection. It is characterized by ease of administration, cost-effectiveness, and rapid production, and it stimulates both systemic and local immune responses. This study investigates early protection against heterologous influenza infection within one week after immunization with the live influenza vaccine. AIM: The aim of the study was to experimentally investigate the mechanisms of early protection against heterologous influenza infection following immunization with a live influenza vaccine. MATERIALS AND METHODS: In in vitro experiments, we studied the production of type I interferons in a culture of monocyte-macrophage-derived cells using enzyme-linked immunosorbent assay. THP-1 cells were seeded at a concentration of 3 × 106 cells/ml, and after 48 hours, the vaccine strain of the live influenza vaccine was added. Mice were immunized intranasally under light ether anesthesia with the vaccine virus A/17/South Africa/2013/01(H1N1)pdm09, obtained from the virus collection of the Virology Department of the Institute of Experimental Medicine, at a dose of 6.0 lg EID50. Infection was performed on the 6th day after immunization with the virus A/Indonesia/5/2005(H5N1) IDCDC-RG2. RESULTS: During the introduction of both the vaccine virus and the parental virus A/South Africa/3626/2013 (H1N1)pdm09 into THP-1 cell cultures, an increase in the production of early cytokines was observed. Immunization with the live influenza vaccine completely protected the mice from lethal infection with a heterologous influenza virus. CONCLUSIONS: The obtained data may indicate the benefits of using the live influenza vaccine during the seasonal uptick of acute respiratory viral infections due to the stimulation of innate immune factors.