The autoimmunity-associated gene PTPN22 potentiates toll-like receptor-driven, type 1 interferon-dependent immunity.

Immune cells sense microbial products through Toll-like receptors (TLR), which trigger host defense responses including type 1 interferons (IFNs) secretion. A coding polymorphism in the protein tyrosine phosphatase nonreceptor type 22 (PTPN22) gene is a susceptibility allele for human autoimmune and infectious disease. We report that Ptpn22 selectively regulated type 1 IFN production after TLR engagement in myeloid cells. Ptpn22 promoted host antiviral responses and was critical for TLR agonist-induced, type 1 IFN-dependent suppression of inflammation in colitis and arthritis. PTPN22 directly associated with TNF receptor-associated factor 3 (TRAF3) and promotes TRAF3 lysine 63-linked ubiquitination. The disease-associated PTPN22W variant failed to promote TRAF3 ubiquitination, type 1 IFN upregulation, and type 1 IFN-dependent suppression of arthritis. The findings establish a candidate innate immune mechanism of action for a human autoimmunity "risk" gene in the regulation of host defense and inflammation.

The promise of a prophylactic Epstein-Barr virus vaccine.

The worldwide burden of disease due to Epstein-Barr virus (EBV) infection is enormous. Diseases include endemic Burkitt lymphoma, infectious mononucleosis, cancers after transplantation, Hodgkin lymphoma, and nasopharyngeal carcinoma. A prophylactic EBV vaccine has the potential to significantly reduce the incidence and/or the severity of all these diseases. Infectious mononucleosis can be nasty and prolonged with a median duration of 17 days. Patients, especially children, undergoing bone marrow or solid organ transplantation may develop post-transplant lymphoproliferative disorder (PTLD). Preventing or modifying primary EBV infection could reduce the incidence PTLD, and also certain lymphomas and nasopharyngeal carcinoma. EBV is a major environmental risk factor for multiple sclerosis (MS). Contracting EBV is essential to getting MS, and having a childhood case of infectious mononucleosis increases that risk. Vaccinating against EBV could be vaccinating against MS.

Epstein-Barr Virus DNA in Parental Oral Secretions: A Potential Source of Infection for Their Young Children.

Background: A potential source of primary Epstein-Barr virus (EBV) infection for young children is parental oral secretions. If parents who identify with racial/ethnic categories other than white have a higher prevalence of oral EBV DNA, this difference could explain why their children acquire primary EBV infection at an earlier age than white children. Methods: To test this hypothesis, we recruited parents who brought their children <8 years old to routine clinic visits, and tested the parents' oral washes for EBV DNA by real-time polymerase chain reaction. Positive samples were assayed for encapsidated EBV DNA, which is potentially infectious, versus naked EBV DNA, which is not infectious. Results: Overall, 221/800 parents (28%) had EBV DNA in their oral washes. Oral EBV DNA was more prevalent in parents who identified as non-white as compared with white parents (P = .0004), and was more prevalent in male vs female parents (P = .04). The mean quantity of EBV DNA in positive samples was 5000 copies/mL. Encapsidated viral DNA comprised 40.3% of the total EBV DNA found in parental oral secretions. Conclusions: Our data support the hypothesis that parents could be a source of virus for their young children, because 28% of parents had a mean of 5000 EBV copies/mL of oral wash and 40.3% of the EBV DNA was encapsidated. The higher prevalence of EBV DNA in non-white parents could explain why their children acquire EBV at an earlier age than children of white parents.

The Incubation Period of Primary Epstein-Barr Virus Infection: Viral Dynamics and Immunologic Events.

Epstein-Barr virus (EBV) is a human herpesvirus that causes acute infectious mononucleosis and is associated with cancer and autoimmune disease. While many studies have been performed examining acute disease in adults following primary infection, little is known about the virological and immunological events during EBV's lengthy 6 week incubation period owing to the challenge of collecting samples from this stage of infection. We conducted a prospective study in college students with special emphasis on frequent screening to capture blood and oral wash samples during the incubation period. Here we describe the viral dissemination and immune response in the 6 weeks prior to onset of acute infectious mononucleosis symptoms. While virus is presumed to be present in the oral cavity from time of transmission, we did not detect viral genomes in the oral wash until one week before symptom onset, at which time viral genomes were present in high copy numbers, suggesting loss of initial viral replication control. In contrast, using a sensitive nested PCR method, we detected viral genomes at low levels in blood about 3 weeks before symptoms. However, high levels of EBV in the blood were only observed close to symptom onset-coincident with or just after increased viral detection in the oral cavity. These data imply that B cells are the major reservoir of virus in the oral cavity prior to infectious mononucleosis. The early presence of viral genomes in the blood, even at low levels, correlated with a striking decrease in the number of circulating plasmacytoid dendritic cells well before symptom onset, which remained depressed throughout convalescence. On the other hand, natural killer cells expanded only after symptom onset. Likewise, CD4+ Foxp3+ regulatory T cells decreased two fold, but only after symptom onset. We observed no substantial virus specific CD8 T cell expansion during the incubation period, although polyclonal CD8 activation was detected in concert with viral genomes increasing in the blood and oral cavity, possibly due to a systemic type I interferon response. This study provides the first description of events during the incubation period of natural EBV infection in humans and definitive data upon which to formulate theories of viral control and disease pathogenesis.

Transplantation of solid organ recipients shedding Epstein-Barr virus DNA pre-transplant: A prospective study.

Epstein-Barr virus (EBV) poses a significant threat to patient and graft survival post-transplant. We hypothesized that recipients who shed EBV at transplant had less immunologic control of the virus and hence were more likely to have active EBV infection and disease post-transplant. To test this hypothesis, we conducted a 5-year prospective study in primary solid organ transplant recipients. We measured EBV DNA in oral washes and blood samples by quantitative PCR before transplant and periodically thereafter for up to 4 years. Pre-transplant samples were available from 98 subjects. EBV DNA was detected pre-transplant in 32 of 95 (34%) and 5 of 93 subjects (5%) in oral wash and blood, respectively. Recipients with and without detectable pre-transplant EBV DNA were not significantly different demographically and had no significant difference in patient and graft survival (P = .6 for both comparisons) or post-transplant EBV viremia-free survival (P = .8). There were no cases of EBV-related disease or post-transplant lymphoproliferative disorder (PTLD) in any of the patients with detectable EBV DNA pre-transplant. In conclusion, detectable EBV DNA pre-transplant was not associated with differences in patient/graft survival, post-transplant EBV viremia, or EBV-related diseases including PTLD.

Cutting edge: NKG2C(hi)CD57+ NK cells respond specifically to acute infection with cytomegalovirus and not Epstein-Barr virus.

CMV induces the expansion of a unique subset of human NK cells expressing high levels of the activating CD94-NKG2C receptor that persist after control of the infection. We investigated whether this subset is CMV specific or is also responsive to acute infection with EBV. We describe a longitudinal study of CMV(-) and CMV(+) students who were acutely infected with EBV. The NKG2C(hi) NK subset was not expanded by EBV infection. However, EBV infection caused a decrease in the absolute number of immature CD56(bright)CD16(-) NK cells in the blood and, in CMV(+) individuals, induced an increased frequency of mature CD56(dim)NKG2A(+)CD57(+) NK cells in the blood that persisted into latency. These results provide further evidence that NKG2C(+) NK cells are CMV specific and suggest that EBV infection alters the repertoire of NK cells in the blood.

Age-specific prevalence of Epstein-Barr virus infection among Minnesota children: effects of race/ethnicity and family environment.

BACKGROUND: Primary Epstein-Barr virus (EBV) infection affects the host differently according to when in life it is acquired. Understanding risk factors for infection could be important for disease prevention, and the age-specific prevalence of infection must be known to optimize use of a prophylactic vaccine. METHODS: Children 18 months to 19.9 years of age who had blood drawn for medical indications during an outpatient visit were eligible. Sera were tested for immunoglobulin G antibodies against EBV viral capsid antigen by enzyme immunoassay. Family demographic and socioeconomic data were obtained via scripted telephone questionnaires. RESULTS: Consent was given for 876 of 914 (96%) subjects approached. Sera were available for 782 of 876 (89%) subjects and demographic/socioeconomic data obtained for 705 (90%) of them. Antibody prevalence, adjusted for age and sex, was as follows: non-Hispanic blacks, 74%; Asians, 62%, multiracial children, 54%; Hispanics, 50%; and non-Hispanic whites, 26%. The pattern of increases in antibody prevalence with age differed significantly by race/ethnicity, and was most divergent in the 2 youngest age groups. Adjusted EBV antibody prevalence decreased with greater household education among non-Hispanic whites, but was not associated with any other socioeconomic factor. In 42 of 51 (82%) families with >1 child in the study, the siblings' EBV antibody status was concordant (bootstrap P < .001). CONCLUSIONS: Racial/ethnic differences in EBV antibody prevalence and concordance of antibody status among siblings prompt us to speculate that both genetics and family environment contribute to acquisition of EBV infection. The ideal age to give a prophylactic vaccine may differ according to race/ethnicity.

Age-specific prevalence of Epstein-Barr virus infection among individuals aged 6-19 years in the United States and factors affecting its acquisition.

BACKGROUND: Data on the age-specific prevalence of Epstein-Barr virus (EBV) infection are relevant for determining when to administer a prophylactic vaccine. Comparison of demographic groups could identify factors associated with its acquisition. METHODS: The National Health and Nutrition Examination Surveys (NHANES) examine a representative sample of the US population. Serum specimens from NHANES participants 6-19 years old were tested for EBV antibody by enzyme immunoassay (EIA). A random portion was also tested by indirect immunofluorescence (IFA). Prevalence estimates and risk-factor comparisons used demographic data and sampling weights in logistic regression models. RESULTS: Serum specimens collected between 2003 and 2010 from 9338 individuals participating in NHANES were tested. The concordance between EIA and IFA findings was 96.7%. The overall age-adjusted EBV antibody prevalence declined from 72% in 2003-2004 to 65% in 2009-2010 (P = .027). The prevalence in 2009-2010 by age group was as follows: 6-8 years, 50%; 9-11 years, 55%; 12-14 years, 59%; 15-17 years, 69%; and 18-19 years, 89%. Within each race/ethnicity group, younger age, health insurance coverage, higher household income, and education level were significantly associated with a lower prevalence of EBV antibody. CONCLUSIONS: The EBV antibody prevalence declined in US individuals aged 6-19 years from 2003-2004 to 2009-2010, mainly because of the decrease among non-Hispanic white participants. The declining antibody prevalence over time and the consistently high observed prevalence among participants aged 12-19 years support broad use of EBV vaccine before 12 years of age.

Behavioral, virologic, and immunologic factors associated with acquisition and severity of primary Epstein-Barr virus infection in university students.

BACKGROUND: University students were studied prospectively to determine the incidence of and risk factors for acquisition of primary Epstein-Barr virus (EBV) infection and the virologic and immune correlates of disease severity. METHODS: EBV antibody-negative freshmen participated in monthly surveillance until graduation. If antibodies developed, proximate samples were assayed for viral load by polymerase chain reaction. Lymphocyte and natural killer (NK) cell numbers and activation were measured by flow cytometry, and plasma cytokine levels were measured by a multiplex assay. RESULTS: Of 546 students screened, 202 (37%) were antibody negative; 143 antibody-negative students were enrolled. During a median of 3 years of observation, 66 subjects experienced primary infection. Of these, 77% had infectious mononucleosis, 12% had atypical symptoms, and 11% were asymptomatic. Subjects reporting deep kissing with or without coitus had the same higher risk of infection than those reporting no kissing (P < .01). Viremia was transient, but median oral shedding was 175 days. Increases were observed in numbers of NK cells and CD8(+) T-cells but not in numbers of CD4(+) T-cells during acute infection. Severity of illness correlated positively with both blood EBV load (P = .015) and CD8(+) lymphocytosis (P = .0003). CONCLUSIONS: Kissing was a significant risk for primary EBV infection. A total of 89% of infections were symptomatic, and blood viral load and CD8(+) lymphocytosis correlated with disease severity.

Rapid antibody responses to Epstein-Barr virus correlate with reduced severity of primary infection.

BACKGROUND: We investigated Epstein-Barr virus (EBV) antibody kinetics in university freshmen who developed laboratory-documented primary EBV infection during prospective studies and correlated these kinetics with disease severity. METHODS: EBV-naïve participants had blood collected periodically and sera tested for EBV-specific antibodies with line blot and enzyme immunoassays. The line blot assay contained EBNA-1, p18, p23, BZLF-1, p138, and p54 antigens; the enzyme immunoassay contained viral capsid antigen and EBNA-1. Severity of illness (SOI) was graded 0 (asymptomatic) to 6 (bedridden). Participants with maximum SOI scores 0-2 were compared with those whose maximum SOI scores were 3-6. Time to first antibody response was analyzed using the semi-parametric COX model. RESULTS: A total of 201 sera from 38 college students collected before, during, and after primary EBV infection were tested. Earlier antibody responses correlated with milder symptoms. This was most pronounced for late-developing antibodies. The median time to development of p18 IgG was significantly earlier among low-SOI participants (64 days) than high-SOI patients (119 days; P = 0.0003).). Participants with mild disease developed EBNA-1 antibodies sooner than participants with more severe disease (125 days versus >270 days; P = 0.017). Participants with mild disease also showed more rapid loss of antibodies against IgG EA p138 and p54 ≥12 weeks post-infection (P = 0.012 and P = 0.026, respectively). CONCLUSIONS: These data suggest that rapid antibody responses to EBV correlate with reduced severity of primary EBV infection.

A virologic pilot study of valacyclovir in infectious mononucleosis.

BACKGROUND: Infectious mononucleosis decreases the productivity of many college students and Epstein-Barr virus (EBV) infection may result in long-term immune damage. OBJECTIVES: Evaluate the antiviral effect of valacyclovir during EBV-related acute infectious mononucleosis and explore potential clinical benefits. STUDY DESIGN: University students who presented during the first 7 days of illness were randomized to receive valacyclovir 3g/day for 14 days or not. The quantity of Epstein-Barr virus (EBV) DNA in oral and whole blood samples was determined by real-time (TaqMan) PCR. The primary outcome was the proportion of subjects with laboratory-confirmed primary EBV infection who had >or=2 log10 decrease in EBV copies/mL in oral washes during the treatment period. Secondary outcomes included clinical effects. RESULTS: Twenty subjects were studied. The proportion of valacyclovir recipients versus control subjects who had >or=2 log10 decrease in EBV copies was significantly greater for both oral wash fluid-derived cell pellet (P=0.03) and supernatant (P=0.001) samples. At the end of the treatment period, the number of reported symptoms (P=0.03) and the severity of illness (P=0.049) were reduced among valacyclovir recipients as compared with controls. CONCLUSIONS: Valacyclovir therapy caused a reduction of EBV excretion and possibly produced a clinical benefit in infectious mononucleosis. Because our study was small and not placebo-controlled, these results must be confirmed by a larger, placebo-controlled trial.

Epstein-Barr virus dynamics in asymptomatic immunocompetent adults: an intensive 6-month study.

Characterizing Epstein-Barr virus (EBV) dynamics in asymptomatic immunocompetent persons provides a baseline for defining quantitative thresholds associated with EBV disease. Studying latent membrane protein (LMP)-1 sequence variation over time could establish the rates of reactivation and superinfection, and also trace transmission. Twelve asymptomatic adult subjects were evaluated prospectively nine times over 6 months. EBV serum antibodies were measured by enzyme immunoassay. EBV DNA in oral and whole-blood samples was quantitated by real-time (TaqMan) PCR and analyzed for LMP-1 sequence variability. All 11 antibody positive subjects had EBV DNA detected in their oral compartment at least once during the 6-month study. The quantities ranged from 1.70 to 4.91 log10 copies EBV per ml of oral cell pellet. One subject was continuously viremic for 79 days. Overall, EBV DNA was detected in 63 (24%) of 260 samples from 11 antibody-positive subjects and in 0/27 samples from an antibody-negative subject. The quantities in positive samples ranged from 1.7 to 4.9 log10 copies EBV per ml. EBV LMP-1 gene sequence variations in subjects were constant over time regardless of the compartment sampled. Subjects 18-30 years old had EBV DNA detected more frequently than subjects >30 years old (38/108 positive samples versus 25/152; P<0.001). In conclusion, EBV DNA shedding is common in asymptomatic adults. The younger adults shed more frequently, which may reflect a shorter time from their primary EBV infection to sampling. The LMP-1 sequence analysis method employed here could be used to trace person-to-person transmission because patterns remained almost identical over time.

Prospective studies of infectious mononucleosis in university students.

We performed an intensive prospective study designed to obtain as much data as possible on the incubation and early illness periods of primary Epstein-Barr virus (EBV) infection. Undergraduate students who lacked EBV antibody and oral EBV DNA (EBV-naive) were seen every 2 weeks during their freshman year. Clinical and behavioral data, oral washes and venous blood were obtained. EBV antibodies were quantified by enzyme immunoassay and viral loads by PCR. During a median 8 months of observation, 14/85 subjects experienced primary EBV infections (24 cases/100 person-years). The only significant risk factor for acquisition of EBV infection was deep kissing (P=0.02). Eleven subjects had infectious mononucleosis with a median duration of 21 days. Two subjects were hospitalized. Infections were initially identified in 12 subjects by finding EBV DNA in oral cells before onset of symptoms and in 2 subjects by symptom reporting. EBV DNA and viral capsid antigen (VCA) IgM and gp350 IgG antibodies were present in the blood before onset of illness. To provide a more robust evaluation of primary EBV infection in undergraduate university students, we combined data on risk factors and antibody responses from this and an earlier study that used the exact same clinical and laboratory methods. The observation that the only significant risk factor for acquisition of EBV infection was deep kissing was confirmed. Most importantly, higher amounts of gp350 antibody correlated significantly with a lower severity of infectious mononucleosis (P<0.0001), which strengthens the rationale for a gp350-based prophylactic EBV vaccine.

Kinetics of Epstein-Barr Virus (EBV) Neutralizing and Virus-Specific Antibodies after Primary Infection with EBV.

Prospective studies of antibodies to multiple Epstein-Barr virus (EBV) proteins and EBV neutralizing antibodies in the same individuals before, during, and after primary EBV infection have not been reported. We studied antibody responses to EBV in college students who acquired primary EBV infection during prospective surveillance and correlated the kinetics of antibody response with the severity of disease. Neutralizing antibodies and enzyme-linked immunosorbent assay (ELISA) antibodies to gp350, the major target of neutralizing antibody, reached peak levels at medians of 179 and 333 days after the onset of symptoms of infectious mononucleosis, respectively. No clear correlation was found between the severity of the symptoms of infectious mononucleosis and the peak levels of antibody to individual viral proteins or to neutralizing antibody. In summary, we found that titers of neutralizing antibody and antibodies to multiple EBV proteins increase over many months after primary infection with EBV.

Valganciclovir administration to kidney donors to reduce the burden of cytomegalovirus and Epstein-Barr virus transmission during transplantation.

BACKGROUND: Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) infections are a significant cause of morbidity and mortality in transplant recipients and are often transmitted from the donor organ. METHODS: In a pilot prospective, randomized, double-blinded, placebo-controlled trial, we studied whether 14 days of pretransplant donor treatment with valganciclovir (valG) versus placebo reduced donor-to-recipient transmission, making posttransplant recipient prophylaxis more effective in reducing EBV and CMV disease. RESULTS: Seventeen D+ R- donor-recipient pairs were enrolled: 7 and 10 donors were randomized to valG and placebo, respectively. At study initiation, no donor had detectable CMV replication, five had EBV replication (two in valG, three in placebo group): EBV replication was undetectable during valG treatment, but resumed on stopping valG. Valganciclovir was tolerated without side effects or leukopenia. All recipients received routine posttransplant viral prophylaxis with valG. For recipients, viremia-free survival time, incidence, range, peak, and duration of CMV and EBV viremia were not significantly different between groups. There was no disease in the valG group but two serious viral diseases occurred in the placebo group (one CMV; one EBV-related posttransplant lymphoproliferative disorder). In the case of posttransplant lymphoproliferative disorder, the EBV DNA from the donor's oral wash and the recipient's lymphoid tissue biopsy had identical latent membrane protein 1 (LMP-1) sequence variations from the reference EBV strain, making it highly probable that the recipient's virus was of donor origin. CONCLUSION: Based on this pilot trial, we recommend an adequately powered study to determine if pretransplant donor treatment with valG can reduce posttransplant CMV and EBV disease with merely routine posttransplant recipient viral prophylaxis.

The impact of donor viral replication at transplant on recipient infections posttransplant: a prospective study.

BACKGROUND: Organ donors are often implicated as the source of posttransplant recipient infection. We prospectively studied kidney and liver donor-recipient pairs to determine if donor viral replication of cytomegalovirus (CMV), Epstein-Barr virus (EBV), and BK polyomavirus (BKV) at transplant was a risk factor for posttransplant recipient infection and disease. METHODS: Donors and recipients were studied for antibodies against CMV and EBV and for quantitative viral replication of CMV, EBV, and BKV in oral washes, urine, and whole blood pretransplant. Recipient testing continued every 3 months after transplantation. Demographic and clinical data on infections and graft and subject outcomes were obtained. RESULTS: The 98 donor-recipient pairs included 15 liver and 83 kidney transplants (18 of whom were children). No donor had detectable CMV replication; therefore, its impact on recipient CMV replication could not be analyzed. Donor EBV replication occurred in 22%, mostly in the oral wash and showed no impact on posttransplant recipient EBV replication (P=0.9) or EBV viremia (P=0.6) in kidney or liver recipients. Donor BKV replication occurred in 17%, mostly in the urine and although not associated with posttransplant recipient urinary BKV replication in recipients, it was associated with BKV viremia (P=0.02), and a significantly shorter time to BKV viremia (P=0.01) in kidney recipients. CONCLUSION: Donor replication of CMV or EBV did not impact posttransplant recipient viral replication in kidney or liver transplants. Donor urinary BKV replication is associated with recipient BKV viremia in kidney transplants.

Primary EBV infection induces an expression profile distinct from other viruses but similar to hemophagocytic syndromes.

Epstein-Barr Virus (EBV) causes infectious mononucleosis and establishes lifelong infection associated with cancer and autoimmune disease. To better understand immunity to EBV, we performed a prospective study of natural infection in healthy humans. Transcriptome analysis defined a striking and reproducible expression profile during acute infection but no lasting gene changes were apparent during latent infection. Comparing the EBV response profile to multiple other acute viral infections, including influenza A (influenza), respiratory syncytial virus (RSV), human rhinovirus (HRV), attenuated yellow fever virus (YFV), and Dengue fever virus (DENV), revealed similarity only to DENV. The signature shared by EBV and DENV was also present in patients with hemophagocytic syndromes, suggesting these two viruses cause uncontrolled inflammatory responses. Interestingly, while EBV induced a strong type I interferon response, a subset of interferon induced genes, including MX1, HERC5, and OAS1, were not upregulated, suggesting a mechanism by which viral antagonism of immunity results in a profound inflammatory response. These data provide an important first description of the response to a natural herpesvirus infection in humans.

Primary Epstein-Barr virus infection does not erode preexisting CD8⁺ T cell memory in humans.

Acute Epstein-Barr virus (EBV) infection results in an unusually robust CD8(+) T cell response in young adults. Based on mouse studies, such a response would be predicted to result in attrition of preexisting memory to heterologous infections like influenza A (Flu) and cytomegalovirus (CMV). Furthermore, many studies have attempted to define the lymphocytosis that occurs during acute EBV infection in humans, but it is unclear whether bystander T cells contribute to it. To address these issues, we performed a longitudinal prospective study of primary EBV infection in humans. During acute EBV infection, both preexisting CMV- and Flu-specific memory CD8(+) T cells showed signs of bystander activation, including up-regulation of granzyme B. However, they generally did not expand, suggesting that the profound CD8(+) lymphocytosis associated with acute EBV infection is composed largely of EBV-specific T cells. Importantly, the numbers of CMV- and Flu-specific T cells were comparable before and after acute EBV infection. The data support the concept that, in humans, a robust CD8(+) T cell response creates a new memory CD8(+) T cell niche without substantially depleting preexisting memory for heterologous infections.

A prospective clinical study of Epstein-Barr virus and host interactions during acute infectious mononucleosis.

BACKGROUND: Characterizing virus-host interactions during self-limited infectious mononucleosis could explain how Epstein-Barr virus (EBV) replication is normally controlled and provide insight into why certain immunocompromised patients fail to contain it. METHODS: University students had an average of 7 clinical and virologic evaluations during acute infectious mononucleosis. EBV was quantified in 697 samples of oral wash fluid, whole blood, peripheral blood mononuclear cells (PBMCs), and plasma by a real-time (TaqMan) polymerase chain reaction (qEBV) assay developed in our laboratory. RESULTS: Twenty of 25 subjects had serologically confirmed primary EBV infection. EBV was cleared from whole blood by a first-order process with a median half-life of 3 days, and its quantity was associated with severity of illness (r2=0.82). Oral shedding persisted at a median of >or=1x104 copies/mL for 32 weeks and was unrelated to severity of illness. Subjects with nonprimary EBV infection shed virus intermittently, and median quantities for all samples became undetectable within 4 weeks. CONCLUSIONS: Using a novel qEBV assay, we demonstrated that young adults with primary EBV infection rapidly cleared virus from blood but not from the oropharynx. High oral concentrations of EBV in asymptomatic persons who have resumed normal activities support the concept that infectious mononucleosis is most likely acquired by kissing.