Infectious Mononucleosis

Abstract

Infectious mononucleosis is a clinical entity characterized by sore throat, cervical lymph node enlargement, fatigue, and fever most often seen in adolescents and young adults and lasting several weeks. It can be caused by a number of pathogens, but this chapter only discusses infectious mononucleosis due to primary Epstein-Barr virus (EBV) infection. EBV is a γ-herpesvirus that infects at least 90% of the population worldwide. The virus is spread by intimate oral contact among teenagers and young adults. How preadolescents acquire the virus is not known. A typical clinical picture with a positive heterophile test is usually sufficient to make the diagnosis, but heterophile antibodies are not specific and do not develop in some patients. EBV-specific antibody profiles are the best choice for staging EBV infection. In addition to causing acute illness, there can also be long-term consequences as the result of acquisition of the virus. Several EBV-related illnesses occur including certain cancers and autoimmune diseases, as well as complications of primary immunodeficiency in persons with the certain genetic mutations. A major obstacle to understanding these sequelae has been the lack of an efficient animal model for EBV infection, although progress in primate and mouse models has recently been made. Key future challenges are to develop protective vaccines and effective treatment regimens.

Figure 1. Kinetics of EBV viral load and antibody responses in subjects with primary EBV infection

Depicted are viral loads in whole blood, saliva, and oral cell pellets (black lines) as well as IgM and IgG antibodies to VCA and IgG to EBNA1 (colored lines). Note: the limit of detection of the EBV viral genomes in blood was 200 copies per mL of whole blood.

Figure 2. Kinetics of antibody responses to additional EBV antigens as determined by immunoblot

Depicted are viral loads in whole blood, saliva, and oral cell pellets (black lines) as well as the relative kinetics of antibodies generated against the EBV antigens p18, p23, BZLF1, p138, and p54 (colored lines). The gene name of each antigen and the stage of expression (IE: immediate early, E: early, or L: late) are indicated in parentheses.