A case of Epstein-Barr virus-related lymphadenopathy mimicking the clinical features of IgG4-related disease

False-positive serologies for acute hepatitis A and autoimmune hepatitis in a patient with acute Epstein-Barr virus infection

Acute hepatitis remains a diagnostic challenge, and numerous infectious, metabolic and autoimmune diseases need to be effectively excluded. We present a case of a young woman with malaise, fever, jaundice and deranged liver function tests. Testing for Epstein-Barr virus (EBV) virus capsid antigen IgM/IgG was positive. Total IgG was elevated, along with positive serology for anti-hepatitis A virus (HAV)-IgM, antinuclear antibodies (ANAs) and soluble liver antigen (SLA) leading to the differential diagnosis of acute hepatitis A and autoimmune hepatitis. No specific treatment was started and liver function gradually improved. At week 4, HAV IgG and IgM were negative. At month 4, ANA and SLA were negative and total IgG normalised; EBV nuclear antigen became positive. Testing for EBV is an investigation required at baseline in acute hepatitis and physicians should carefully evaluate serological results, including those for viral and autoimmune hepatitis that may be falsely positive in infectious mononucleosis.

Natural Mosquito-Pathogen Hybrid IgG4 Antibodies in Vector-Borne Diseases: A Hypothesis

Chronic exposure to antigens may favor the production of IgG4 antibodies over other antibody types. Recent studies have shown that up to a 30% of normal human IgG4 is bi-specific and is able to recognize two antigens of different nature. A requirement for this specificity is the presence of both eliciting antigens in the same time and at the same place where the immune response is induced. During transmission of most vector-borne diseases, the pathogen is delivered to the vertebrate host along with the arthropod saliva during blood feeding and previous studies have shown the existence of IgG4 antibodies against mosquito salivary allergens. However, there is very little ongoing research or information available regarding IgG4 bi-specificity with regard to infectious disease, particularly during immune responses to vector-borne diseases, such as malaria, filariasis, or dengue virus infection. Here, we provide background information and present our hypothesis that IgG4 may not only be a useful tool to measure exposure to infected mosquito bites, but that these bi-specific antibodies may also play an important role in modulation of the immune response against malaria and other vector-borne diseases in endemic settings.