**Core Concept**
Mallory bodies, also known as Mallory-Denk bodies, are characteristic histopathological features found in the cytoplasm of liver cells (hepatocytes) in certain types of liver disease. They are composed of abnormal, aggregated proteins that accumulate within the cell.

**Why the Correct Answer is Right**
Mallory bodies are primarily composed of intermediate filament proteins, specifically cytokeratins 8 and 18. These proteins are normally involved in maintaining the structural integrity of the cell. However, in the context of liver injury, such as alcoholic hepatitis or non-alcoholic steatohepatitis, the normal balance of protein expression is disrupted, leading to the accumulation of these cytokeratins in a characteristic "trabecular" pattern within the cell. This accumulation is thought to contribute to the disruption of normal cellular function and the progression of liver disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as Mallory bodies are not primarily composed of actin filaments. Actin filaments are involved in cell motility and structural support, but are not the primary component of Mallory bodies.
**Option B:** Incorrect, as Mallory bodies are not composed of smooth muscle cells. Smooth muscle cells are found in various tissues, including the gastrointestinal tract, but are not a component of Mallory bodies.
**Option C:** Incorrect, as Mallory bodies are not composed of viral particles. Mallory bodies are a histopathological feature of certain liver diseases, but are not caused by viral infections.

**Clinical Pearl / High-Yield Fact**
Mallory bodies are a classic histopathological feature of alcoholic hepatitis, and their presence is often used as a diagnostic criterion for this condition. However, it's worth noting that Mallory bodies can also be found in other types of liver disease, including non-alcoholic steatohepatitis and primary biliary cirrhosis.

**Correct Answer: C. Intermediate filament proteins (cytokeratins 8 and 18)**