Primary epstein‐barr virus infections in African infants. II. Clinical and serological observations during seroconversion

Abstract

Abstract Of 27 Ghanaian infants examined monthly for the first 15 months of life and once more at 21 months, 12 acquired primary Epstein‐Barr virus (EBV) infections by the age of 1 year and 9 others seroconverted during the subsequent period of observation. The seroconversions were not accompanied by significant clinical or physical signs of illness and in none of the infants was a diagnosis of infectious mononucleosis (IM) suspected on the basis of hematologic observations. The 12 early seroconverters, providing the most extensive follow‐up data, showed transient IgM antibody responses to EB viral capsid antigen (VCA) which in some cases initially exceeded the corresponding IgG antibodies in titer. Peak VCA‐specific IgG titers were noted 2 months after seroconversion and were comparable to those seen in IM. Most of the infants developed antibodies to the EBV‐induced early antigen complex which were directed, however, against the R (restricted) component, as observed in Burkitt's lymphoma, and not against the D (diffuse) component, as noted in IM. Low titers of VCA‐specific IgA antibodies emerged in five of the cases. Usually, EBV‐neutralizing antibodies were already present in the first anti‐VCA‐positive serum but antibodies to the EBV‐associated nuclear antigen (EBNA) and antibody‐dependent cell‐mediated cytolysis (ADCC) became detectable only months after seroconversion. No heterophil antibody responses, or at most barely significant ones, were recorded. Attempts to demonstrate EBV in throat swab specimens met with limited success, suggesting a low degree of viral excretion during silent seroconversions. Possible explanations for the differences between clinical, hematologic and serologic responses to primary EBV infections in infancy and later in life are discussed.