Baculovirus-mediated expression of a Helicobacter pylori protein-based multiepitope hybrid gene induces a potent B cell response in mice

Helicobacter pylori is a gram-negative bacterium that is present in over half of the world's population. The colonization of the stomach́s gastric mucosa by H. pylori is related to the onset of chronic gastritis, peptic ulcer, and cancer. The estimated deaths from gastric cancer caused by this bacterial infection are in the 15,000–150,000 range. Current treatment for controlling the colonization of H. pylori includes the administration of two to four antibiotics and a gastric ATPase proton pump inhibitor. Nevertheless, the bacterium has shown increased resistance to antibiotics. Despite an extensive list of attempts to develop a vaccine, no approved vaccine against H. pylori is available. Recombinant viruses are a novel alternative for the control of primary pathogenic agents. In this work, we employed a baculovirus that carries a Thp1 transgene coding for nine H. pylori epitopes, some from the literature, and others were selected in silico from the sequence of H. pylori proteins (carbonic anhydrase, urease B subunit, gamma-glutamyl transpeptidase, Lpp20, Cag7, and CagL). We verified the expression of this hybrid multiepitopic protein in HeLa cells. Mice were inoculated with the recombinant baculovirus Bac-Thp1 using various administration routes: intranasal, intragastric, intramuscular, and a combination of intranasal and intragastric. We identified a strong adjuvant-independent IgG-antibody response in the serum of recombinant baculovirus-Thp1 inoculated mice, which was specific for a strain of H. pylori isolated from a human patient. The bacterium-specific IgG-antibodies were present in sera 125 days after the first vaccine administration. Also, H. pylori-specific IgA-antibodies were found in feces at 82 days after the first inoculation. A baculovirus-based vaccine for H. pylori is promising for controlling this pathogen in humans.