Neutrophils rapidly migrate via lymphatics after Mycobacterium bovis BCG intradermal vaccination and shuttle live bacilli to the draining lymph nodes

Abstract

The early innate response after Mycobacterium bovis bacille Calmette-Gué rin (BCG) vaccination is poorly characterized but probably decisive for subsequent protective immunity against tuberculosis. Therefore, we vaccinated mice with fluorescent BCG strains in the ear dorsum, as a surrogate of intradermal vaccination in humans. During the first 3 days, we tracked BCG host cells migrating out of the dermis to the auricular draining lymph nodes (ADLNs). Resident skin dendritic cells (DCs) or macrophages did not play a predominant role in early BCG capture and transport to ADLNs. The main BCG host cells rapidly recruited both in the dermis and ADLNs were neutrophils. Fluorescent green or red BCG strains injected into nonoverlapping sites were essentially sheltered by distinct neutrophils in the ADLN capsule, indicating that neutrophils had captured bacilli in peripheral tissue and transported them to the lymphoid organ. Strikingly, we observed BCG-infected neutrophils in the lumen of lymphatic vessels by confocal microscopy on ear dermis. Fluorescencelabeled neutrophils injected into the ears accumulated exclusively into the ipsilateral ADLN capsule after BCG vaccination. IntroductionMycobacterium bovis bacille Calmette-Guérin (BCG) is the only available vaccine against tuberculosis (TB), a major public health problem. Being included in the World Health Organization (WHO) Expanded Program for Immunization, BCG is one of the most widely administered vaccines. It confers high levels of protection against disseminated forms of TB, particularly severe in children, but its efficacy against pulmonary TB in adults is estimated to be only 50% 1 and varies widely among different geographic areas and populations. Thus, more efficient vaccines against TB are urgently needed. There are reasons to believe that such vaccines could be based on BCG. Therefore, a better understanding of the immune response induced by BCG could help in designing better strategies on a rational basis. Today, BCG vaccination is almost exclusively administered intradermally or percutaneously. 2 Early events occurring after BCG vaccination that will have a strong impact on the adaptive immune response are poorly characterized. For example, it is unknown how BCG travels from the injection site to draining lymph nodes (DLNs) and which host cells could be involved in this early process. Mononuclear phagocytes such as epidermal Langerhans cells (LCs), dermal macrophages, and dendritic cells (DCs) are ideally located to capture microorganisms entering skin. Due to their migratory capacity, DCs shuttle pathogens such as HIV 3 or Leishmania major 4 to DLNs. Bacterial dissemination from gut to mesenteric DLNs occurs via infected DCs after ingestion of Salmonella 5 or Listeria. 6 Peripheral tissue DCs are not the only cells at play in bridging innate and acquired immunity to pathogens. Soon after an inflammatory stimulus, blood monocytes are recruited to the injured tissue from which they can migrate via afferent lymph toward DLNs. There, monocytes acquire a DC ...

Difference in TB10.4 T‐cell epitope recognition following immunization with recombinant TB10.4, BCG or infection with Mycobacterium tuberculosis

“…Bacteria were thawed, sonicated, washed and diluted in PBS before immunizations and infections. Green and red fluorescent BCG expressing either eGFP or DsRed was a kind gift from Nathalie Winter [5]. Antigens rTB10.4 was produced in E. coli as described earlier [24].…”

“…Cells stained with F4/80 were washed in FACS-buffer after surface staining with primary antibodies and secondarily stained with streptavidin conjugated PerCp-Cy5. 5.…”

Changing world of neutrophils

“…Earlier studies indicated that neutrophils were able to present exogenous antigen to CD8+ T-cells [7] and recent data have shown also antigen-presentation to Th1 and Th17 cells [2]. In confocal microscopic studies neutrophils migrating with fluorescently labeled pathogen were observed in draining lymph vessels [1] and lymph nodes [21]. Moreover, the chemokine receptor CCR7 has been identified as a key player in directing neutrophil migration from the interstitium to the draining lymph nodes [6].…”

Cell tracking and velocimetric parameters analysis as an approach to assess activity of mussel (Mytilus edulis) hemocytes in vitro

“…Cell attachment to substrate per se may participate to the increase of immune activity and respiratory burst. In mammals, immune cells are known to migrate rapidly towards the site of infection (Abadie et al 2005;Chtanova et al 2008;Germain et al 2012). Interestingly, ex vivo explant experiments give evidence for accelerated random migration of immune cells, at rates of 8 lm min -1 , similar to interstitial velocities reported for neutrophils at sites of inflammation (Graham et al 2009;Kreisel et al 2010).…”