Oral polyvalent vaccine (Buccalin Berna) administration activates selected T-cell subsets and regulates the expression of polymorphonuclear leukocyte membrane molecules.

Acute respiratory tract infections (ARIS) still represent a major clinical problem during influenza outbreaks. The virus-induced impairment of the immune system favors the entry of opportunistic microorganisms into respiratory tract mucosa. A useful strategy to reduce ARIS is to provide at risk subjects an orally administrable polyvalent vaccine (OPV) comprised of bacteria strains recognised as the major ones responsible for ARIS. For the present study, the main circulating leukocyte populations of a group of healthy subjects receiving OPV were monitored as a marker of immune response. Subjects were investigated immediately before taking OPV (day 0) and 10,20, and 30 days later. Data show that T lymphocytes were induced to enhance the expression of class II MHC molecules, whilst a consistent number of CD4+ lymphocytes lost L-selectin, both phenomena indicating an activation status. OPV administration also modulated important molecules on the membrane of polymorphonuclear leukocytes, namely CD11b and CD16, strongly suggesting an activation of these cells and an enhancement of their defensive capacities. Finally, OPV was found to be able to increase the titer of serum antibodies specific for bacteria strains contained in the vaccine preparation in a portion of individuals. We conclude that OPV is able to consistently influence important immune functions and suggest that this property may be of relevance in preventing ARIS. Also, the present data may help to further our understanding of the mechanisms of OPV activity.