CD40LG and hepatitis A virus infection: Considering the good correlation (r = 0.99, p< 0.001) between the optical density (OD) values of the paired samples, the high frequency (100%-80%) and probability (100%-85%) of IgM anti-HAV detection in saliva of HAV acute cases at 30 and 90th (100%-80%, respectively); the salivary IgM anti-HAV test showed a potential of substitute serum test in diagnosis of hepatitis A infection, mainly during the first 90 days post infection.