Differences in the Epstein-Barr Virus gp350 IgA Antibody Response Are Associated With Increased Risk for Coinfection With a Second Strain of Epstein-Barr Virus

BACKGROUND

The Epstein-Barr virus (EBV) viral glycoprotein gp350 has been proposed as a candidate antigen for an EBV vaccine. However, the proposed formulations of these vaccines have not taken into account the presence of 2 unique EBV strains (EBV-1 and EBV-2) present in areas of high incidence of the EBV-associated cancer, Burkitt lymphoma.

METHODS

In this study, we analyze the kinetics of EBV-1 and EBV-2 infection in an asymptomatic infant cohort from Kisumu, Kenya. We also analyzed the kinetics of the antibody response against 5 EBV antigens, gp350 (IgG and IgA), VCA (IgG), EBNA-1 (IgG), EAd (IgG), and Zta (IgG).

RESULTS

We observed a high frequency of coinfection with both EBV types over time, with the only observable defect in the antibody response in infants coinfected being a significantly lower level of anti-gp350 IgA at peak response. Gp350 IgA levels were also significantly lower in coinfected infants 2.5 months postinfection and at the time of coinfection.

CONCLUSIONS

These results suggest that anti-gp350 IgA antibodies may be important for sterilizing immunity against secondary infection. These findings have implications for the development of an efficacious EBV vaccine to prevent both EBV-1 and EBV-2 infection in a population at high risk for Burkitt lymphoma.

Changes in Tonsil B Cell Phenotypes and EBV Receptor Expression in Children Under 5-Years-Old

BACKGROUND

Palatine tonsils are principally B cell organs that are the initial line of defense against many oral pathogens, as well as the site of infection for others. While the size of palatine tonsils changes greatly in the first five years of life, the cellular changes during this period are not well studied. Epstein Barr virus (EBV) is a common orally transmitted virus that infects tonsillar B cells. Naïve B cells are thought to be the target of primary infection with EBV in vivo, suggesting that they are targeted by the virus. EBV enters B cells through CD21, but studies of older children and adults have not shown differences in surface CD21 between naïve B cells and other tonsil B cell populations.

METHODS

In this study, we used an 11-color flow cytometry panel to detail the changes in B cell subpopulations in human tonsils over the first five years of life from 33 healthy US children.

RESULTS

We provide reference ranges for tonsil B cell subpopulations over this age range. We show that the frequency of naïve tonsil B cells decreases over the early years of life, and that naïve B cells expressed higher surface levels of CD21 relative to other tonsil B cell populations.

CONCLUSIONS

We show that young children have a higher frequency of naïve tonsil B cells, and importantly that these cells express increased surface EBV receptor, suggesting that young children have a larger pool of cells that can be infected by the virus. © 2017 International Clinical Cytometry Society.

Identification of a novel variant of LMP-1 of EBV in patients with endemic Burkitt lymphoma in western Kenya

Background

Epstein Barr virus (EBV) is a gammaherpesvirus that is associated with nasopharyngeal carcinoma (NPC) and endemic Burkitt lymphoma (eBL). EBV carries several latent genes that contribute to oncogenesis including the latent membrane protein 1 (LMP-1), a known oncogene and constitutively active CD40 homolog. Variation in the C terminal region of LMP-1 has been linked to NPC pathogenesis, but little is known regarding LMP-1 variation and eBL.

Results

In the present study, peripheral blood samples were obtained from 38 eBL patients and 22 healthy controls in western Kenya, where the disease is endemic. The LMP-1 C-terminal region from these samples was sequenced and analyzed. The frequency of a 30 base pair deletion of LMP-1 previously linked to NPC was not associated with eBL compared to healthy controls. However a novel LMP-1 variant was identified, called K for Kenya and for the G318K mutation that characterizes it. The K variant LMP-1 was found in 40.5% of eBL sequences and 25.0% of healthy controls. All K variant sequences contained mutations in both of the previously described minimal T cell epitopes in the C terminal end of LMP-1. These mutations occurred in the anchor residue at the C-terminal binding groove of both epitopes, a pocket necessary for MHC loading.

Conclusions

Overall, our results suggest that there is a novel K variant of LMP-1 in Kenya that may be associated with eBL. Further studies are necessary to determine the functional implications of the LMP-1 variant on early events in eBL genesis.