What are the 20 nm spheres in filamentous structures of HBV?

The 20 nm spheres found in the filamentous structures of hepatitis B virus (HBV) are known as circulating aggregates of hepatitis B surface antigen (HBsAg). These structures are a crucial part of the immune response and are formed as the virus infects liver cells and begins to replicate.

HBsAg is a protein that makes up the envelope of HBV. When the virus replicates, it produces excess HBsAg that can form non-infectious particles, which are released into the bloodstream. These 20 nm spheres, or "dane particles" (the complete virus), along with filamentous and spherical forms of HBsAg, represent these excess proteins. Their presence in the circulation can be used in laboratory assays to diagnose HBV infection.

While the other options might seem plausible, they do not accurately describe the specific nature or function of these 20 nm spheres. They are not cell aggregates, as they do not represent clumps of living cells, nor do they represent viral particles in a complete sense, as these structures are not infectious. Furthermore, they are not classified as inactive virus components; rather, they play a significant role in the body’s immune response and are indicative of ongoing HBV infection, making their identification critical