The accuracy of anti-human herpesvirus 6 IgM detection in children with recent primary infection.

Human herpesvirus 6 (HHV-6) has been shown to infect almost all children by 4 years of age. Even with a typical clinical presentation, HHV-6 infection is misdiagnosed frequently as measles or rubella. The aim of this study was to assess the accuracy of the IgM test for detection of recent primary HHV-6 infection. The study was conducted between January, 1998 and December, 2006 at primary health care units in Niterói, Rio de Janeiro, Brazil. Sera from 185 children, in whom measles, rubella, dengue fever and parvovirus B19 infections were excluded, were studied for anti-HHV-6 IgG and IgM antibodies using an indirect immunofluorescence test. Seventy-one (38.4%) of the children had evidence of primary HHV-6 infection. Taking the IgG avidity test as the "gold standard", the following results for IgM were obtained-sensitivity: 76.1%; specificity: 87.5%; accuracy: 82.4%. This study confirmed the low accuracy of IgM detection for the diagnosis of primary HHV-6 infection.

Role of human herpesvirus 6 infection in young Brazilian children with rash illnesses.

BACKGROUND: Human herpesvirus type 6 (HHV-6) has been shown to infect almost all children by 4 years of age. Primary infection causes an undifferentiated febrile illness, with approximately 30% of children exhibiting the classic clinical manifestations of exanthem subitum. Even with typical clinical presentation, exanthem subitum is frequently misdiagnosed as measles or rubella. Our aim was to describe the frequency and clinical manifestations of HHV-6 infection in children less than 4 years of age enrolled in a study designed to define the etiology of rash diseases. PATIENTS AND METHODS: The study was conducted between January 1998 and December 2006 at a general hospital and a large primary health care unit from Niterói, Rio de Janeiro, Brazil. Sera from 223 children, in whom measles, rubella, dengue fever, and parvovirus B19 infections were excluded, were studied for anti-HHV-6 antibodies using an indirect immunofluorescence test. Demographic and clinical data of those patients were described. RESULTS: Ninety-seven (43.5%) of the children had evidence of primary HHV-6 infection. The age of onset peaked at 6-11 months and 75% of the HHV-6 infection occurred in children between 6 and 17 months. Only 21% of the HHV-6 cases had a typical roseola-like illness and 73% and 46%, respectively, fulfilled the clinical criteria of measles and rubella suspected case. CONCLUSIONS: Our study confirms the importance of HHV-6 infection in young children and highlights the difficulties of diagnosing a rash illness on clinical grounds alone.

Functional characterization of BK virus-specific CD4+ T cells with cytotoxic potential in seropositive adults.

BK polyomavirus (BKV) reactivation is associated with a failure of T cell immunity in kidney transplant patients, and may lead to BKV-associated nephropathy (BKVN) and loss of the allograft. BKV reactivation in hematopoietic stem cell transplant recipients is associated with hemorrhagic cystitis. We have investigated T cell responses to overlapping peptide mixtures corresponding to the whole BKV major T antigen (TAg) and major capsid protein (VP1) in peripheral blood mononuclear cell samples from a cohort of healthy BKV-seropositive subjects. The majority of these individuals possessed populations of both CD8(+) and CD4(+) T cells specific for these BKV antigens. After expansion in culture, the majority of the BKV-specific CD4(+) T cells, in addition to expressing CD40L (CD154), secreted both interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, contained both granzyme A and granzyme B, and degranulated/mobilized CD107 in response to antigen-specific stimulation. These T cells thus represent potentially functional BKV-specific cytotoxic CD4(+) T lymphocytes. Secretion of both TNF-alpha and IFN-gamma by CD154(+)CD4(+) T cells on BKV-specific stimulation was associated with higher levels of granzyme B and a higher proportion of degranulating cells compared with CD154(+)CD4(+) T cells producing only IFN-gamma or neither cytokine. These healthy subjects also harbored populations of functional CD8(+) T cells specific for one or more of three newly defined HLA-A 02-restricted cytotoxic T lymphocyte epitopes within the BKV TAg as well as two HLA-A 02-restricted epitopes within the BKV VP1 we have previously described. The BKV-specific CD4(+) T cells characterized in this study may play a part in maintaining persistent memory T cell responses to the virus and thus contribute to the immune control of BKV in healthy individuals.

Discovery and epidemiology of the human polyomaviruses BK virus (BKV) and JC virus (JCV).

Although discovered over thirty years ago, many aspects of the epidemiology of BKV and JCV in the general population, such as the source of infectious virus and the mode of transmission, are still unknown. Primary infection with both BKV and JCV is usually asymptomatic, and so age seroprevalence studies have been used to indicate infection. BKV commonly infects young children in all parts of the world, with the exception of a few very isolated communities, adult seroprevalence rates of 65-90% being reached by the age of ten years. In contrast, the pattern of JCV infection appears to vary between populations; in some anti-JCV antibody is acquired early as for BKV, but in others anti-JCV antibody prevalence continues to rise throughout life. This indicates that the two viruses are probably transmitted independently and by different routes. Whilst BKV DNA is found infrequently in the urine of healthy adults, JCV viruria occurs universally, increasing with age, with adult prevalence rates often between 20% and 60%. Four antigenic subtypes have been described for BKV and eight genotypes are currently recognized for JCV. The latter have been used to trace population movements and to reconstruct the population history in various communities.

Simian virus 40 (SV40) and human cancer: a review of the serological data.

Serum antibodies are widely utilised as specific and sensitive markers of virus infections but they have been employed relatively infrequently in the investigation of simian virus 40 (SV40) as a human carcinogen. In the past few years, serological data have become available which allow an examination of whether SV40 is currently circulating in human communities and if SV40 infection is associated with human cancer. The development of EIA with virus-like particles (VLPs) of SV40, BKV and JCV has facilitated serological studies. Sera from macaques naturally infected with SV40 cross-react unambiguously with BKV and JCV VLPs. Tests of over 9000 human sera with different immunological assays reveal a common pattern of SV40 reactivity. A small proportion of sera react at low titers and this reactivity is unrelated to age or the geographic location of the donor, but correlates with the presence and titers of BKV and JCV antibodies. Absorption with BKV and JCV VLPs decreases or abolishes the SV40 reactivity of human sera. The SV40 reactivity of sera from patients with mesothelioma, osteosarcoma or lymphomas, cancers which are reported to be associated with SV40, was similar to that in their controls or other comparison groups. The SV40 reactivity of human sera appears to be almost entirely a result of cross-reactivity with BKV and JCV antibodies. Serological data thus do not support the possibility that SV40 is circulating in human communities or that it is associated with human cancer.

Population-based study of antibody to the human polyomaviruses BKV and JCV and the simian polyomavirus SV40.

Molecular studies suggest that the simian polyomavirus SV40 is present in the human population, possibly introduced in contaminated polio vaccine. However, no recent seroepidemiological data exist in England on SV40 or on the two human polyomaviruses, BKV and JCV. A comparative age seroprevalence study was undertaken on 2,435 residual sera from 1991 by haemagglutination inhibition (HI) for BKV and JCV, and virus neutralisation for SV40. The overall rates of seropositivity for BKV and JCV were 81% and 35%, respectively, and each was significantly related to age (P < 0.001). BKV seroprevalence reached 91% at 5-9 years of age, but JCV seroprevalence reached only 50% by age 60-69 years. There was a highly significant association between BKV antibody titre and age (P < 0.001), titres decreasing linearly at a rate of 8.7% per 10 years (95% CI = 7.4-10% drop). Significantly more males than females had antibody to JCV (P = 0.013). In individuals under 40 years of age there was a significant negative association between the presence of antibody to BKV and JCV (P < 0.001). By contrast, the antibody prevalence to SV40 remained at 1.3-5% throughout all age groups and titres were low. There was a significant positive association between the presence of antibody to SV40 and antibody to both BKV (P < 0.001) and JCV (P = 0.009), and also to the geometric mean titre (GMT) of BKV antibody (P = 0.011). The results indicate that BKV and JCV are transmitted by different routes. There is no serological evidence that SV40 entered the human population during the past 80 years, and the possibility of cross-reaction with BKV or JCV antibody must be considered.

Prospective study of polyomavirus type BK replication and nephropathy in renal-transplant recipients.

BACKGROUND: Nephropathy associated with the polyomavirus type BK (BKV) nephropathy has emerged as a cause of allograft failure linked to immunosuppressive regimens containing tacrolimus or mycophenolate mofetil. The presence of viral inclusions, known as "decoy cells," in urine and the presence of BKV DNA in plasma have been proposed as markers for the replication of BKV and associated nephropathy, but data from prospective studies have been lacking. METHODS: In a prospective, single-center study, we followed 78 renal-transplant recipients who were receiving immunosuppressive therapy that included tacrolimus (37 patients) or mycophenolate mofetil (41 patients). Urine was tested for the presence of decoy cells at routine visits. BKV DNA was measured 3, 6, and 12 months after transplantation and whenever decoy cells were detected. The viral load in plasma was quantified with the use of a real-time polymerase-chain-reaction method. Renal biopsy was performed if allograft function deteriorated. RESULTS: Twenty-three patients had decoy-cell shedding a median of 16 weeks after transplantation (range, 2 to 69), 10 patients had BKV viremia at a median of 23 weeks (range, 4 to 73), and 5 had BKV nephropathy at a median of 28 weeks (range, 8 to 86). Kaplan-Meier estimates of the probability of decoy-cell shedding, viremia, and nephropathy were 30 percent (95 percent confidence interval, 20 to 40 percent), 13 percent (95 percent confidence interval, 5 to 21 percent), and 8 percent (95 percent confidence interval, 1 to 15 percent), respectively. Antirejection treatment, particularly with corticosteroids, was associated with BKV replication and nephropathy. The viral load in plasma was higher in patients with BKV nephropathy than in those without nephropathy (P<0.001 by the Mann-Whitney test). BKV antibodies were detected in 77 percent of the 78 patients before transplantation, including 4 of 5 with BKV nephropathy. CONCLUSIONS: BKV nephropathy in renal-transplant recipients represents a secondary infection associated with rejection and its treatment in most cases and could be monitored by measuring the viral load in plasma.

Expression and antigenic characterization of the major capsid proteins of human polyomaviruses BK and JC in Saccharomyces cerevisiae.

BK and JC viruses are ubiquitous human polyomaviruses that are associated with post-transplant interstitial nephritis (BK virus) and progressive multifocal leucoencephalopathy (JC virus). The use of a yeast system to express the major capsid protein (VP1) of two antigenic variants of BKV (strains SB and AS) and JCV is described. VP1s of AS and JCV expressed in Saccharomyces cerevisiae produced proteins of expected molecular weight as determined by gel electrophoresis whereas that of SB appeared to be lower than anticipated. However, all VP1s self-assembled into virus-like particles (VLP) retaining sialic acid-binding and antigenic properties of native virions. This method is highly efficient for producing recombinant proteins and therefore provides an alternative to the baculovirus system.