Subcapsular sinus macrophage infection after viral dissemination to distal lymph nodes maximizes germinal center responses

Abstract

Abstract Neutralizing antibodies are a hallmark of protective humoral response against many viral infections. Microanatomical structures called germinal centers (GCs) within the secondary lymphoid organs are the sites where B cells get differentiated into high affinity antibody secreting, class switched and long-lasting plasma and memory B cells. Most studies of antigen movement leading to B cell activation have been performed using subcutaneous injection, mimicking the natural route of infection. Under this condition, virus infects sinusoidal lymph node macrophages which relay the antigen to B cells to drive the GC responses. However, not much is known about antigen movement during the generation of GCs in the non-draining (or distal lymph nodes) after systemic viral dissemination. Using ZIKV infection of mice, we have mapped virus dissemination through two separate lymph node chains. Surprisingly, GCs efficiently formed in distal LNs, although with delayed kinetics compared to those directly draining the infection site. Remarkably, virus in the blood alone was not sufficient to produce GCs. Instead, virus still reached the LNs through the lymphatics and infected LN sinusoidal macrophages. This coincided with virus-induced vascular permeability in the tissue. Thus, GC formation still proceeds through sinusoidal LN macrophages even when virus is spread through the blood. Our findings reveal a conserved mechanism for antiviral B cell development in LNs distal from the site of infection.