Studying the Status of DC Activation and Antibody Response to OVA in Vaccinated Mice Mimicking the Natural Course of Infection

Abstract

Immunological memory is the characteristic property of an immune system, which provides protection to the host from pathogen on its re-encounter. Vaccination is used to generate long lived protective immunity in the host by providing stimulus to the immune cells, which is identical to that of the natural infection. The goal of vaccination is to generate a long-lived heterogeneous pool of memory cells i.e. T cells as well as B cells; is not achieved in some acute viral infections. In the case of various viral infections, it is observed that, under the natural course of viral infection e.g. chicken pox, the host is well equipped with long lived immunological memory as compared to the vaccinated host. This observation prompted us to hypothesize that, it may be due the gradual increase in the antigenic load as well as array of pathogen associated molecular patterns (PAMPs) in the natural infection, that are causing antigen presenting cells (APCs) to come in the wave manner as well as regulated activation of these APCs, taking up the antigen and presenting it to the naïve T cells in lymph node leading to the heterogeneous pool of activated T cells as well as B cells. So, in our present study we are trying to mimic the course of natural infection in mice by administering the PAMPs and OVA antigen (Ag) as a model antigen in gradual increasing manner as in the case of natural viral infection and looking for the accumulation and activation status of DCs in the nearest draining Lymph node. The number of DCs in the lymph node increases in the dose dependent manner but the same level of increase in the activation of DCs is not observed when natural course of infection is mimicked. Cytokine environment is also seen to have its effect on ability to present antigen and status of APCs and on effector TH response. So, we are also estimating the effector cytokine response produced after the immunization to check whether they are playing any role in recruitment and activation of DCs. The level of pro-inflammatory cytokine produced post 1st immunization in NCI 2 is similar to the vaccine regime group administered with the highest dose of PAMPs and OVA. Any vaccination strategy if is able to induce humoral response along with the cell-mediated immune response, it is considered to be the better strategy. Therefore, the present study also deals with the comparison of the humoral response between this novel vaccination strategy and conventional vaccine strategy. And the results from the study reveal the greater OVA specific IgG response induced in mice vaccinated with OVA mimicking the natural course of infection compared to the vaccine regime group