Bacterial ghosts modulation of innate immunity: immune responses during chlamydia infection, 2015

Abstract

Chlamydia trachomatis (CT) is a pestilent infection affecting upwards of 90 million people worldwide. An efficacious vaccine is needed to control the morbidities and rising healthcare cost associated with genital CT infection. We have established that protection against chlamydia infection parallels with a high frequency of T helper Type 1 cells and the associated antibodies. The current study focuses on the induction of innate immune responses involved during Chlamydia infection by a Vibrio cholera ghost-based (VCG) vaccine vector. THP-1 cells were used for dose and kinetic experiments. HeLa cells were used for infectivity assays. Based on preliminary studies, we hypothesized that the induction of immune responses by a VCG-based vaccine involves multiple innate immune signaling. Multiplex assay was used to measure T helper Type I and Type II cytokine secretion by THP-1 monocytes (Mn) or macrophages (M?). Immunostimulatory cytokine secretion was significant when both cell morphologies were pulsed with VCG or VCG/murine splenocytes. We concluded that this secretion was significant enough to compliment that which would be secreted when THP-1 cells are pulsed with Chlamydia elementary bodies alone, enhancing the innate immune response during infection. Cellular supernatants (conditioned media) containing Th1-type and Th2-type cytokines were used to culture Chlamydia-infected HeLa cell monolayers. Infected HeLa monolayers cultured in the conditioned media were significantly less infected (968 IFUs) versus HeLa monolayers cultured in Earles minimum essential media (16,486 IFUs; p<0.001). We concluded that factors contained in conditioned media prevent and/or significantly reduce infection by Chlamydia and the development of inclusion forming units. KEY TERMS: Vaccine, Innate Immunity, Chlamydia trachomatis, Bacterial Ghosts, Infectious Diseases, Immunology of Infectious Diseas