Virus Carrier State Research Articles

Nervous Necrosis Virus Modulation of European Sea Bass (Dicentrarchus labrax, L.) Immune Genes and Transcriptome towards Establishment of Virus Carrier State

Viral infections of teleost fish have great environmental and economic implications in aquaculture. Nervous necrosis virus (NNV) is a pathogen affecting more than 120 different species, causing high mortality and morbidity. Herein, we studied the course of NNV experimental infection of D. labrax, focusing on survivors which indicated viral carrier state. To determine the carrier state of D. labrax head kidney, we performed a gene expression analysis of selected immune-related genes and we profiled its transcriptome 14 days post infection (dpi). All tested genes showed clear differentiations in expression levels while most of them were up-regulated 14 dpi suggesting that their role is not limited in early antiviral responses, but they are also implicated in disease persistence. To gain a better understanding of the fish that survived the acute infection but still maintained a high viral load, we studied the differential expression of 124 up-regulated and 48 down-regulated genes in D. labrax head kidney, at 14 dpi. Concluding, the NNV virus persistent profile was assessed in D. labrax, where immune-related gene modification was intense (14 dpi) and the head kidney transcriptome profile at this time point offered a glimpse into host attempts to control the infection in asymptomatic carriers.

Development of a TaqMan® Allelic Discrimination qPCR Assay for Rapid Detection of Equine CXCL16 Allelic Variants Associated With the Establishment of Long-Term Equine Arteritis Virus Carrier State in Stallions.

Equine arteritis virus (EAV) is the causative agent of equine viral arteritis (EVA), a respiratory, systemic, and reproductive disease of equids. Following natural infection, up to 70% of the infected stallions can remain persistently infected over 1 year (long-term persistent infection [LTPI]) and shed EAV in their semen. Thus, the LTP-infected stallions play a pivotal role in maintaining and perpetuating EAV in the equine population. Previous studies identified equine C-X-C motif chemokine ligand 16 (CXCL16) as a critical host cell factor determining LTPI in the stallion’s reproductive tract. Two alleles (CXCL16 S and CXCL16 r ) were identified in the equine population and correlated with the susceptibility or resistance of a CD3+ T cell subpopulation in peripheral blood to in vitro EAV infection, respectively. Interestingly, CXCL16 S has been linked to the establishment of LTPI in stallions, and thus, genotyping stallions based on CXCL16 S/r would allow identification of those at the highest risk of establishing LTPI. Thus, we developed a TaqMan® allelic discrimination qPCR assay for the genotyping of the equine CXCL16 gene based on the identification of a single nucleotide polymorphism in position 1,073 based on NCBI gene ID: 100061442 (or position 527 based on Ensembl: ENSECAG00000018406.2) located in exon 2. One hundred and sixty horses from four breeds were screened for the CD3+ T cell susceptibility phenotype to EAV infection by flow cytometry and subsequently sequenced to determine CXCL16 allelic composition. Genotyping by Sanger sequencing determined that all horses with the resistant CD3+ T cell phenotype were homozygous for CXCL16 r while horses with the susceptible CD3+ T cell phenotype carried at least one CXCL16 S allele or homozygous for CXCL16 S . In addition, genotypification with the TaqMan® allelic discrimination qPCR assay showed perfect agreement with Sanger sequencing and flow cytometric analysis. In conclusion, the new TaqMan® allelic discrimination genotyping qPCR assay can be used to screen prepubertal colts for the presence of the CXCL16 genotype. It is highly recommended that colts that carry the susceptible genotype (CXCL16 S/S or CXCL16 S/r ) are vaccinated against EAV after 6 months of age to prevent the establishment of LTPI carriers following possible natural infection with EAV.

Reactivation of Hepatitis B Virus in Cancer Patients Receiving Chemotherapy

Reactivation of Hepatitis B Virus in Cancer Patients Receiving Chemotherapy

No evidence for long-term carrier status of pigs after African swine fever virus infection.

This study targeted the assessment of a potential African swine fever virus (ASFV) carrier state of 30 pigs in total which were allowed to recover from infection with ASFV "Netherlands'86" prior exposure to six healthy sentinel pigs for more than 2months. Throughout the whole trial, blood and swab samples were subjected to routine virological and serological investigations. At the end of the trial, necropsy of all animals was performed and viral persistence and distribution were assessed. Upon infection, a wide range of clinical and pathomorphological signs were observed. After an initial acute phase in all experimentally inoculated pigs, 66.6% recovered completely and seroconverted. However, viral genome was detectable in blood samples for up to 91days. Lethal outcomes were observed in 33.3% of the pigs with both acute and prolonged courses. No ASFV transmission occurred over the whole in-contact phase from survivors to sentinels. Similarly, infectious ASFV was not detected in any of the tissue samples from ASFV convalescent and in-contact pigs. These findings indicate that the suggested role of ASFV survivors is overestimated and has to be reconsidered thoroughly for future risk assessments.

Immune responses to oral pcDNA-VP2 vaccine in relation to infectious pancreatic necrosis virus carrier state in rainbow trout Oncorhynchus mykiss

The VP2 gene of infectious pancreatic necrosis virus, encoded in an expression plasmid and encapsulated in alginate microspheres, was used for oral DNA vaccination of fish to better understand the carrier state and the action of the vaccine. The efficacy of the vaccine was evaluated by measuring the prevention of virus persistence in the vaccinated fish that survived after waterborne virus challenge. A real-time RT-qPCR analysis revealed lower levels of IPNV-VP4 transcripts in rainbow trout survivors among vaccinated and challenged fish compared with the control virus group at 45 days post-infection. The infective virus was recovered from asymptomatic virus control fish, but not from the vaccinated survivor fish, suggesting an active role of the vaccine in the control of IPNV infection. Moreover, the levels of IPNV and immune-related gene expression were quantified in fish showing clinical infection as well as in asymptomatic rainbow trout survivors. The vaccine mimicked the action of the virus, although stronger expression of immune-related genes, except for IFN-1 and IL12, was detected in survivors from the virus control (carrier) group than in those from the vaccinated group. The transcriptional levels of the examined genes also showed significant differences in the virus control fish at 10 and 45 days post-challenge.

Association between CISH polymorphisms and spontaneous clearance of hepatitis B virus in hepatitis B extracellular antigen–positive patients during immune active phase

Background Some hepatitis B extracellular antigen (HBeAg)-positive chronic hepatitis B (CHB) patients in their immune active phase can clear the virus spontaneously and enter into an inactive hepatitis B virus (HBV) carrier state, indicating a benign prognosis. In this study, the association between cytokine-inducible SRC homology 2 domain protein (CISH) gene polymorphisms at -292 (rs414171) and the spontaneous clearance of HBV in HBeAg-positive CHB patients in immune the active phase was investigated. Methods Seventy HBeAg-positive CHB patients in the immune active phase were followed up for 76 weeks without antiviral therapy. The alanine transaminase, aspartate transaminase, HBV DNA, HBeAg and hepatitis B extracellular antibody levels were tested regularly. At week 76, 27 patients were classified into group A (HBV DNA level below 2 104 IU/ml and the value of HBeAg declined below 10% of the baseline at week 76), and 43 patients were classified into group B (HBV DNA level higher than 2×104 IU/ml or the value of HBeAg did not decline substantially at week 76). CISH (rs414171) polymorphisms were also tested using the iPLEX system. Results The HBV DNA levels at week 12 were significantly greater in group B compared with group A (group A: (6.87±1.40) log10IU/ml; group B: (7.61±1.38) log10IU/ml, P=0.034) and the HBeAg values were greater in group B at week 28 compared with group A (P=0.001). The differences in HBV DNA and HBeAg values increased between the groups over time. Sixteen patients in group A and 11 in group B were genotype AA. Those with genotype AT or TT included 11 in group A and 31 in group B (AA vs. AT and TT, odds ratio 4.10 (95% confidence interval: 1.462-11.491), P=0.006). Conclusion CISH gene polymorphisms at -292 (rs414171) are associated with HBV clearance in HBeAg-positive CHB patients in the immune active phase, and AA is a favorable genotype for this effect.

Liver fibrosis progression is uncommon in patients with inactive chronic hepatitis B: A prospective cohort study with paired transient elastography examination

The European Association for the Study of the Liver (EASL) defines the inactive hepatitis B virus (HBV) carrier state based on HBV DNA and alanine aminotransferase (ALT) levels. This study aimed to evaluate the risk of disease progression in such patients. Three hundred sixty-one patients negative for hepatitis B e antigen (HBeAg) with HBV DNA levels < 20,000 IU/mL and normal ALT and without advanced fibrosis at baseline underwent liver stiffness measurement (LSM) by transient elastography between 2006 and 2008 and again between 2010 and 2012. Liver fibrosis progression was defined as an increase in LSM by 30% or more at the second assessment to levels suggestive of advanced fibrosis. At baseline, the mean age was 48 ± 11 years and 51% were males; ALT level was 28 ± 11 IU/L, HBV DNA level was 2.7 ± 1.0 log10 IU/mL, and LSM was 5.4 ± 1.5 kPa. After an interval of 44 ± 7 months, liver fibrosis progression was observed in 10 (2.8%) patients, and 49 (13.6%) started antiviral therapy. Gender, age, and levels of ALT, HBV DNA, and HBsAg were shown not to be associated with liver fibrosis progression. Among 244 patients with baseline HBV DNA < 2000 IU/mL, 2.9% had liver fibrosis progression, 8.2% started antiviral therapy, and 4.1% had HBV DNA ≥ 20,000 IU/mL during follow-up. Corresponding figures in 117 patients with baseline HBV DNA levels of 2000-20,000 IU/mL were 2.6%, 24.8%, and 7.7%, respectively (P = 1.0, < 0.001 and = 0.21 respectively). Liver fibrosis progression within 3-4 years is rare in HBeAg-negative patients with HBV DNA <20,000 IU/mL and normal ALT, but a significant proportion of patients develop treatment indications during follow-up. The study supports the EASL's definition of inactive carriers and its recommendation of regular monitoring.

Immunogenicity and Cross Protective Ability of the Central VP2 Amino Acids of Infectious Pancreatic Necrosis Virus in Atlantic Salmon (Salmo salar L.)

Infectious pancreatic necrosis virus (IPNV) is a member of the family Birnaviridae that has been linked to high mortalities in juvenile salmonids and postsmolt stages of Atlantic salmon (Salmo salar L.) after transfer to seawater. IPN vaccines have been available for a long time but their efficacy has been variable. The reason for the varying immune response to these vaccines has not well defined and studies on the importance of using vaccine trains homologous to the virulent field strain has not been conclusive. In this study we prepared one vaccine identical to the virulent Norwegian Sp strain NVI-015 (NCBI: 379740) (T217A221T247 of VP2) and three other vaccine strains developed using the same genomic backbone altered by reverse genetics at three residues yielding variants, T217T221T247, P217A221A247, P217T221A247. These 4 strains, differing in these three positions only, were used as inactivated, oil-adjuvanted vaccines while two strains, T217A221T247 and P217T221A247, were used as live vaccines. The results show that these three residues of the VP2 capsid play a key role for immunogenicity of IPNV vaccines. The virulent strain for inactivated vaccines elicited the highest level of virus neutralization (VN) titers and ELISA antibodies. Interestingly, differences in immunogenicity were not reflected in differences in post challenge survival percentages (PCSP) for oil-adjuvanted, inactivated vaccines but clearly so for live vaccines (TAT and PTA). Further post challenge viral carrier state correlated inversely with VN titers at challenge for inactivated vaccines and prevalence of pathology in target organs inversely correlated with protection for live vaccines. Overall, our findings show that a few residues localized on the VP2-capsid are important for immunogenicity of IPNV vaccines.

Reply to Dr Onal: the importance of serum angiotensin-converting enzyme level in chronic hepatitis B

We would like to thank Dr. Onal for his interest in our recent study.1 The non-invasive assessment of liver fibrosis is an ongoing research area of viral hepatitis. Hitherto, these studies have focused mainly on patients infected with hepatitis C.2–4 In this regard, our study is important because we tried to determine whether a new non-invasive fibrosis marker could be possible for patients with chronic hepatitis B as well. Despite our small-sized study, the results were promising. First of all, we did not intend to find a non-invasive marker for discriminating between patients who are in different phases of chronic hepatitis B (CHB). Our main driving force was to discriminate between mild fibrosis and advanced fibrosis using serum angiotensin-converting enzyme level. While in the planning phase of the study, as we mentioned in detailed fashion in the article, we discovered many hypothetical and theoretical facts that could lead to using serum ACE level as a marker of fibrosis in CHB. Although we did not study the power of serum ACE level for discriminating between HbeAg-negative CHB and the inactive hepatitis B virus (HBV) carrier state, we will take Dr. Onal’s valuable opinion into account in our future studies.

A Survey on the Frequency of Foot-and-Mouth Disease Virus Carriers in Cattle in North-East of Iran by RT-PCR: Implications for Revising Disease Control Strategy

Foot-and-mouth disease (FMD) is endemic in Iran. It is essential to timely evaluate the current disease control programme in Iran. Here, we report the frequency of FMD virus (FMDV) carrier state in cattle slaughtered in Mashhad abattoir, Mashhad, Khorasan Razavi, north-east of Iran, which contains long common borders with Afghanistan and Turkmenistan. Soft palate samples were collected immediately after slaughter for the detection of FMDV by RT-PCR. The results show that 37.7% of cattle (96 of 255) were carriers of the virus. Among positive samples (96), 58 (60.4%) belonged to serotype O. No evidence was detected for the presence of Asia 1 and A serotypes. Nucleotide sequencing and phylogenic dendogram showed close similarity and common lineage between our samples and viruses isolated in Pakistan. With an approximate more than 80% of cattle population vaccination coverage such a high rate of carrier state may show an extensive FMDV exposure. Therefore, limiting control programmes to timely prophylactic vaccination may be insufficient. This is also true when meat market instabilities act as a temptation to import livestock, legally or illegally, through the eastern frontiers. It is recommended to change the current prophylactic vaccination strategy to a well-developed regional control programme, with close monitoring of animal movement through eastern frontiers, supported by government commitment and educational programmes. Timely estimation of the frequency of carrier state both in cattle and small ruminants is also advocated as a gauge to monitor the virus status in the region.

Interaction of Epstein-Barr virus (EBV) with human B-lymphocytes

Epstein-Barr virus, EBV, and humans have a common history that reaches back to our primate ancestors. The virus co-evolved with man and has established a largely harmless and highly complex co-existence. It is carried as silent infection by almost all human adults. A serendipitous discovery established that it is the causative agent of infectious mononucleosis. Still, EBV became known first in 1964, in a rare, geographically prevalent malignant lymphoma of B-cell origin, Burkitt lymphoma BL. Its association with a malignancy prompted intensive studies and its capacity to immortalize B-lymphocytes in vitro was soon demonstrated. Consequently EBV was classified therefore as a potentially tumorigenic virus. Despite of this property however, the virus carrier state itself does not lead to malignancies because the transformed cells are recognized by the immune response. Consequently the EBV induced proliferation of EBV carrying B-lymphocytes is manifested only under immunosuppressive conditions. The expression of EBV encoded genes is regulated by the cell phenotype. The virus genome can be found in malignancies originating from cell types other than the B-lymphocyte. Even in the EBV infected B-cell, the direct transforming capacity is restricted to a defined window of differentiation. A complex interaction between virally encoded proteins and B-cell specific cellular proteins constitute the proliferation inducing program. In this short review we touch upon aspects which are the subject of our present work. We describe the mechanisms of some of the functional interactions between EBV encoded and cellular proteins that determine the phenotype of latently infected B-cells. The growth promoting EBV encoded genes are not expressed in the virus carrying BL cells. Still, EBV seems to contribute to the etiology of this tumor by modifying events that influence cell survival and proliferation. We describe a possible growth promoting mechanism in the genesis of Burkitt lymphoma that depends on the presence of EBV.

A Novel Virus Carrier State to Evaluate Immunotherapeutic Regimens: Regulatory T Cells Modulate the Pathogenicity of Antiviral Memory Cells

Restrictions in the diversity of an adaptive immune repertoire can facilitate viral persistence. Because a host afflicted with an immune deficiency is not likely to purge a persistent infection using endogenous mechanisms, it is important to explore adoptive therapies to supplement the host with a functional immune defense. In this study, we describe a virus carrier state that results from introducing lymphocytic choriomeningitis virus (LCMV) into adult mice possessing a restricted T cell repertoire. On infection of these mice, LCMV establishes systemic persistence, and within the CNS the virus infects astrocytes (and later oligodendrocytes) rather than its traditional parenchymal target neurons. To determine whether LCMV could be purged from a novel target selection in the absence of an endogenous immune repertoire, we adoptively transferred virus-specific memory cells into adult carrier mice. The memory cells purged virus from the periphery as well as the CNS, but they induced fatalities not typically associated with adoptive immunotherapy. When the repertoire of the recipient mice was examined, a deficiency in natural regulatory T cells was noted. We therefore supplemented carrier mice with regulatory T cells and simultaneously performed adoptive immunotherapy. Cotransfer of regulatory T cells significantly reduced mortality while still permitting the antiviral memory cells to purge the persistent infection. These data indicate that regulatory T cells can be used therapeutically to lessen the pathogenicity of virus-specific immune cells in an immunodeficient host. We also propose that the novel carrier state described herein will facilitate the study of immunotherapeutic regimens.

Pathogenesis of Epstein-Barr Virus (EBV)-carrying Lymphomas

The EBV carrier state is almost general in men. The virus induces B lymphocyte proliferation in vitro, but this is counteracted in vivo by the immune response. Therefore, EBV-induced malignancies occur only when the immune response is impaired, e.g. in transplant recipients. The versatility of the viral gene expression strategy secures the consistent maintainance of the virus in healthy individuals. The viral proteins required for transformation render the cell immunogenic. Expression of the transforming genes leads to rejection, but these genes are not required for the maintenance of the viral genome. EBV is an important contributor for malignant transformation, even when it does not directly induce cell proliferation. Several mechanisms have been unravelled in EBV-associated tumors whereby the virus may modify the cellular phenotype and may influence the interaction of tumor cells with their microenvironment. The virus carrier state can lead to the evasion of apoptosis and can intensify the response to growth promoting signals, too.

Hepatitis C virus infection in a resident elderly population: A 10-year follow-up study

Background The natural history of hepatitis C virus infection in the elderly is poorly known. Objective To assess the mortality rate, the progression of liver disease, the hepatitis C virus carrier state and the co-morbidity in a cohort of 35 out of 1063 anti-hepatitis C virus positive elderly people prospectively followed-up from 1992 to 2002. Methods Liver function tests, hepatitis C virus-RNA analysis, hepatitis C virus genotyping and abdominal ultrasonography were assessed at the beginning of the study, and then, liver function tests and ultrasonography were performed annually during the first 5 years of the follow-up. At the end of the 10-year period, causes of death were recorded, while surviving patients underwent again medical examination, liver function tests and abdominal ultrasonography. Results Out of 35 patients with a 10-year follow-up, 12 patients died: only 2 (5.7%) from liver-related disease (hepatocellular carcinoma and liver failure), whilst 10 (28.5%) from extrahepatic causes. Out of the two patients dying from liver-related causes, one was hepatitis C virus-RNA positive and one hepatitis C virus-RNA negative. Among the 23 living patients, 13 were hepatitis C virus-RNA positive (56.5%), the majority being infected with genotype 2 (69%); of them, 6 (46.1%) had persistently normal alanine aminotransferase levels. None of the hepatitis C virus-RNA positive individuals had excessive alcohol intake. Conclusion Despite the presumably long duration of infection in our cohort, the liver-related mortality was five-fold lower than that from extrahepatic causes (five-fold higher). Lack of hepatic co-morbidity factors, such as alcohol consumption, seems to be relevant for the limited severity of liver disease.

Combined passive and active immunoprophylaxis for preventing perinatal transmission of the hepatitis B virus carrier state in Shizuoka, Japan during 1980-1994.

Efficacy and limits in preventing perinatal infection with hepatitis B virus (HBV) have been examined in a model area in Japan. In Shizuoka (population of 3.6 million), immunoprophylaxis of perinatal HBV infection was started in 1980 in four institutions (Hamamatsu Medical College, Shimada City Hospital, Shizuoka Kodomo Hospital and Numazu City Hospital). Babies born to carrier mothers with hepatitis B e antigen (HBeAg) in serum received hepatitis B immune globulins at birth and 2 months thereafter and vaccines at 2, 3 and 5 months after birth. Overall, 980 of the 1030 babies born to HBeAg-positive carrier mothers were protected by the immunoprophylaxis during the 15 years from 1980 to 1994 with an efficacy of 95.1%. From 1986 to 1994 while the national immunoprophylaxis was conducted, 329,674 of the 346,637 (95.1%) expectant mothers were tested, and 2081 (0.63%) of them were positive for hepatitis B surface antigen (HBsAg). The immunoprophylaxis was given only to babies born to 764 (36.7%) of the 2081 mothers who tested positive for HBeAg. Of the 494 babies receiving immunoprophylaxis, in whom HBsAg was followed monthly after birth, 462 (93.5%) were protected. The HBV carrier state developed in the remaining 32 (6.5%) babies, 10 of whom (31.3% of the 32) turned positive for HBsAg within 1 month after birth, most likely owing to infection in utero. Passive-active immunoprophylasxis of high-risk babies was highly efficacious in preventing perinatal transmission of the HBV carrier state. Most failures (approximately 70%) occurred in the high-risk babies who were exposed to HBV after birth, and would have been avoided by careful and extensive execution of the immunoprophylaxis.

Impairment of the metabolism of dipyrone in asymptomatic carriers of the hepatitis-B virus does not occur in rapid acetylators

We previously found that, compared with healthy subjects. asymptomatic hepatitis-B virus (HBV) carriers displaying slow acetylator phenotype demonstrate a significant prolongation of the elimination half-life of 4-methylaminoantipyrine (MAA) and a decrease in the clearance of formation of 4-aminoantipyrine (AA) and 4-formylaminoantipyrine (FAA). However, the formation of 4-acetylaminoantipyrine (AAA) was unchanged. The present study was designed to examine the effect of the asymptomatic HBV carrier state on the metabolism of dipyrone. as a model drug, in rapid acetylators. The plasma and urine concentrations of the metabolites of dipyrone were measured in eight asymptomatic HBV carriers and eight healthy subjects who had normal liver function tests, all displaying the rapid acetylation phenotype and genotype, after the administration of a 1.0-g oral dose of dipyrone. The following pharmacokinetic parameters were evaluated: peak plasma concentration, time to peak plasma concentration, elimination rate constant, area under the plasma concentration-time curve (0-->infinity), amount excreted (0-->infinity), renal and non-renal clearances for MAA and the clearances of formation for AA, FAA and AAA. No significant differences were found between the two subject groups. The effect of hepatic viral carrier state on drug metabolism may vary according to metabolic pathways and genetic polymorphism.

Characterization of proteinuria in asymptomatic family members and household contacts of children with hepatitis B virus-associated membranous nephropathy

The biosocial background in which the hepatitis B virus (HBV) carrier state with membranous nephropathy (MN) develops was studied by evaluating HBV carriage and proteinuria among 195 family members and household contacts of 31 index HBV carrier children with MN. Unrelated individuals from the communities of these index cases who were negative for HBV served as controls (n = 123). HBV was determined by using third-generation enzyme-linked immunosorbent assay, slot-blot hybridization, and nested polymerase chain reaction. Patterns of proteinuria were determined by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis; immunoglobulin G and haptoglobulin were suggestive of MN. Seventy-two members (36.9%) of the study group (n = 195) were HBV carriers; 21 of these carriers (29.2%) had proteinuria. Twenty-eight members (41.2%) of the study group who were HBV negative (n = 68) and 26.8% of the controls showed proteinuria. This lack of association between HBV carriage and proteinuria remained when controlled for sex and family relationship. HBV was not protective against the development of proteinuria. Proteinuria suggestive of MN was strongly associated with an abnormal protein-creatinine ratio (P: = 0.001), but was not significantly different between subjects and controls (8.7% versus 6.5%; P: = 0.5). Genetic influences or environmental exposures in these subjects may be responsible for the proteinuria, suggesting underlying glomerular basement membrane damage. Discordance between the HBV carrier state and patterns of proteinuria in the study group suggest that HBV and MN may not be causally related or may reflect exceptional interaction between specifically vulnerable individuals and HBV.

Coinfection of multiple strains of Epstein-Barr virus in immunocompetent normal individuals: reassessment of the viral carrier state

This study reassesses the occurrence of Epstein-Barr virus (EBV) diversity and coinfection versus dominance of a single viral strain within immunocompetent normal carriers. Polymerase chain reaction analysis of several different polymorphic loci of the EBV genome was performed on collections of peripheral blood mononuclear cells and multiple lymphoid and epithelial tissues of the same individuals. Autopsy specimens from 15 individuals who died of causes unrelated to EBV infection served as normal viral carriers. Unexpectedly, coinfection of multiple distinct strains of EBV of the same type (usually type 1) and less frequently of both types 1 and 2 was found to be very high within individual viral carriers. These data indicate that coinfection with multiple EBV strains is much more prevalent in normal carriers than previously appreciated, which in turn has direct implications on EBV persistence, host–viral interaction and pathogenesis.

The complexity of the Epstein-Barr virus infection in humans.

The Epstein-Barr virus (EBV) was isolated 40 years ago from cultures of Burkitt lymphoma cells (BL). The tumor was encountered in Africa and exhibited characteristical geographical, clinical and pathological features. Serological studies revealed that the virus is ubiquitous in humans. The primary infection is often accompanied by the syndrome of acute infectious mononucleosis (IM). It can induce malignant proliferation of B lymphocytes in conditions of immunodeficiency. EBV can immortalize B lymphocytes in culture. These cells carry the virus as episomes and express 9 virally encoded proteins. Their immunological recognition constitutes the surveillance which is responsible for the healthy virus carrier state. The main virus reservoir is represented by a low number of resting B lymphocyte which contain the viral genome but do not express its transformation proteins. The viral genome is detectable in all African BLs, in variable proportions of nasopharyngeal carcinoma, Hodgkin's disease, T cell lymphoma, lymphoepithelial like carcinoma, gastric carcinoma and leiomyosarcoma cases. The role of EBV in the genesis of these tumors is unknown.

Impairment of the metabolism of dipyrone in asymptomatic carriers of the hepatitis B virus.

The pharmacokinetics of a number of drugs has been shown to be impaired in patients with acute or chronic viral liver disease. To examine the effect of the asymptomatic hepatitis B virus carrier state on the metabolism of dipyrone (INN, metamizole) as a model drug. The pharmacokinetics of the metabolites of dipyrone-4-methylaminoantipyrine, 4-aminoantipyrine, 4-formylaminoantipyrine, and 4-acetylaminoantipyrine-after a 1.0 gm oral dose of dipyrone were evaluated in nine asymptomatic carriers of hepatitis B virus with normal liver function tests and nine healthy subjects. All subjects displayed the slow acetylator phenotype. The nonrenal (metabolic) clearance of 4-methylaminoantipyrine was significantly reduced (mean +/- SEM) (123.3 +/- 15.8 versus 182.9 +/- 15.1 ml.min-1, respectively; p < 0.02) in the carriers of hepatitis B virus compared with the healthy subjects, and the elimination half-life of this metabolite was significantly longer (3.69 +/- 0.35 versus 2.64 +/- 0.28 hours, respectively; p < 0.03). The formation clearances of 4-aminoantipyrine and 4-formylaminoantipyrine were significantly smaller in the carriers of hepatitis B virus compared with healthy subjects (33.8 +/- 6.2 versus 55.2 +/- 6.4 ml.min-1; p < 0.03, and 16.7 +/- 2.2 versus 34.2 +/- 4.2 ml.min-1; p < 0.002; respectively). However, the elimination half-life of 4-formylaminoantipyrine was found to be slightly shorter in the carriers of hepatitis B virus. No significant differences were noted between the groups in the pharmacokinetics of 4-acetylaminoantipyrine. The metabolism of dipyrone is impaired in asymptomatic carriers of hepatitis B virus. Clinically latent infection with hepatitis B virus seems to exert a differential effect on metabolism of the drug. Oxidative pathways to produce 4-aminoantipyrine and 4-formylaminoantipyrine were significantly affected, whereas acetylation remained intact. This study provided an additional example of the effect of a virus on the disposition of a drug.