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We studied whether antibody to two chlamydial proteins (TroA and HtrA) could be used as biomarkers of Chlamydia trachomatis infection. Methods: Recombinant proteins C. trachomatis TroA and HtrA were used as antigens in enzyme immunoassay (EIA). Both IgG and IgA antibody responses were studied. Results: IgG or IgA antibody to either protein was infrequently detected in sera from healthy blood donors or virgin girls. Patients attending the STI Clinic and patients with perihepatitis had often IgG antibody against TroA (25 and 50 % respectively) and HtrA (21 and 38 % respectively). Especially in sera from patients with chlamydial perihepatitis, the A values with TroA were high (mean 1.591). A positive correlation between C. trachomatis MIF antibody and TroA ( r = 0.7) as well as HtrA ( r = 0.5) antibody was observed in sera from STI clinic patients and perihepatitis patients. Individuals with C. trachomatis infection and positive serology already when seeking medical attention had higher A values for TroA (0.638) and HtrA (0.836) than patients with no marker of previous exposure or with no infection (0.208 and 0.234 respectively). Diagnosis of genital C. trachomatis infection is often NAAT-based, whereas serology has little value in testing for uncomplicated genital C. trachomatis infection. TroA and HtrA antibodies are potential biomarkers for evaluation of ascending and repeated C. trachomatis infection. [ABSTRACT FROM AUTHOR]

Upon binding to pathogen or self-derived cytosolic nucleic acids cyclic GMP-AMP synthase (cGAS) triggers the production of cGAMP that further activates transmembrane protein STING. Upon activation STING translocates from ER via Golgi to vesicles. Monogenic STING gain-of-function mutations cause early-onset type I interferonopathy, with disease presentation ranging from fatal vasculopathy to mild chilblain lupus. Molecular mechanisms underlying the variable phenotype-genotype correlation are presently unclear. Here, we report a novel gain-of-function G207E STING mutation causing a distinct phenotype with alopecia, photosensitivity, thyroid dysfunction, and features of STING-associated vasculopathy with onset in infancy (SAVI), such as livedo reticularis, skin vasculitis, nasal septum perforation, facial erythema, and bacterial infections. Polymorphism in TMEM173 and IFIH1 showed variable penetrance in the affected family, implying contribution to varying phenotype spectrum. The G207E mutation constitutively activates inflammation-related pathways in vitro , and causes aberrant interferon signature and inflammasome activation in patient PBMCs. Treatment with Janus kinase 1 and 2 (JAK1/2) inhibitor baricitinib was beneficiary for a vasculitic ulcer, induced hair regrowth and improved overall well-being in one patient. Protein-protein interactions propose impaired cellular trafficking of G207E mutant. These findings reveal the molecular landscape of STING and propose common polymorphisms in TMEM173 and IFIH1 as likely modifiers of the phenotype., (Copyright © 2019 Keskitalo, Haapaniemi, Einarsdottir, Rajamäki, Heikkilä, Ilander, Pöyhönen, Morgunova, Hokynar, Lagström, Kivirikko, Mustjoki, Eklund, Saarela, Kere, Seppänen, Ranki, Hannula-Jouppi and Varjosalo.)

Chlamydia trachomatis , Mycoplasma genitalium , herpes simplex virus (HSV) and human papillomavirus (HPV) cause sexually transmitted infections. In addition, human herpesvirus 6 (HHV-6) may be a genital co-pathogen. The prevalence rates of HSV, HHV-6, HPV, M. genitalium , and the C. trachomatis ompA genotypes were investigated by PCR in urogenital samples of the C. trachomatis nucleic acid amplification test positive (n = 157) and age-, community- and time-matched negative (n = 157) women. The prevalence of HPV DNA was significantly higher among the C. trachomatis positives than the C. trachomatis negatives (66% vs. 25%, p < 0.001). The prevalence of HSV (1.9% vs. 0%), HHV-6 (11% vs. 14%), and M. genitalium DNA (4.5% vs. 1.9%) was not significantly different between the C. trachomatis -positive and -negative women. Thirteen per cent of test-of-cure specimens tested positive for C. trachomatis . The prevalence of HSV, HHV-6, HPV, M. genitalium , and the C. trachomatis ompA genotypes did not significantly differ between those who cleared the C. trachomatis infection (n = 105) and those who did not (n = 16). The higher prevalence of HPV DNA among the C. trachomatis positives suggests greater sexual activity and increased risk for sexually transmitted pathogens., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

This study characterizes a large Mycoplasma pneumoniae outbreak observed in Kymenlaakso in Southeastern Finland during August 2017-January 2018. The first part of the investigation included 327 patients, who sought healthcare consultation at local GPs or hospitals due to clinical symptoms, and were tested for M. pneumoniae antibodies (Patient cohort). The second part of the investigation, conducted approximately 4 weeks after the peak of the outbreak, consisted of school screening of pupils (N = 239) in three different school buildings by PCR on respiratory specimens and questionnaires (Screening cohort). PCR positive respiratory specimens were subsequently utilized for molecular typing. The outbreak peaked in late October 2017. Of the Patient cohort, 9/106 (8.5%) respiratory specimens were PCR positive. In contrast, 3/182 (1.6%) of the Screening cohort were PCR positive. Asymptomatic carriage was observed. Multiple-locus variable-number tandem-repeat analysis (MLVA) identified two distinct MLVA types. All typed M. pneumoniae strains belonged to P1 type 1. No mutations leading to macrolide resistance were observed. In total, 61/327 (19%) of the Patient cohort had a serological indication of recent infection. The IgM test reactivity at the time of a negative PCR test result varied from a completely non-reactive value up to very strong reactivity, highlighting the difficulty in a single specimen serodiagnosis.

Chlamydia trachomatis IgG antibody testing (CAT) has been used as a screening test for tubal factor infertility (TFI), but as the CAT is only a marker of a past exposure to C. trachomatis and not of late sequelae, the positive predictive value (PPV) of the test is low. The persistence of C. trachomatis in the upper genital tract has been suggested as one of the key mechanisms in the development of TFI. Serum antibodies against C. trachomatis TroA and HtrA, proteins expressed specifically during persistent infection, have been suggested as novel biomarkers for TFI diagnostics. We studied serum IgG antibody responses against C. trachomatis TroA, HtrA and MOMP in 79 subfertile women, of whom 28 had laparoscopically proven TFI. We confirmed that the accuracy of CAT in diagnosing TFI is low, whereas TroA IgG and HtrA IgG are more accurate tests in detecting tubal occlusion and pelvic adhesions. However, the sensitivity and negative predictive value (NPV) of TroA IgG and HtrA IgG are still too low to justify their use as a screening test in clinical practice. Individual immunogenetic profiles combined with TroA and HtrA antibody responses might identify women with the highest risk for developing late complications after C. trachomatis infection.

In 2019, more than 200 cases of Chlamydia trachomatis negative/equivocal by the Aptima Combo 2 assay (AC2, target: 23S rRNA) with slightly elevated relative light units (RLUs), but positive by the Aptima Chlamydia trachomatis assay (ACT, target: 16S rRNA) have been detected in Finland To identify the cause of the AC2 CT false-negative specimens, we sequenced parts of the CT 23S rRNA gene in 40 specimens that were AC2 negative/equivocal but ACT positive. A single nucleotide polymorphism (SNP; C1515T in the C. trachomatis 23S rRNA gene) was revealed in 39 AC2/ACT discordant specimens. No decrease in the number of mandatorily notified C. trachomatis cases was observed nationally in Finland in 2010-2019. When RLUs obtained for AC2 negative specimens were retrospectively evaluated in 2011-2019, a continuous increase in the proportion of samples with RLUs 10-19 was observed since 2014, and a slight increase in the proportion of samples with RLUs 20-84 in 2017-2019, indicating that the Finnish new variant of C. trachomatis might have been spreading nationally for several years. This emphasizes that careful surveillance of epidemiology, positivity rate and test performance are mandatory to detect any changes affecting detection of infections.

The transcriptional gene expression patterns of Chlamydia trachomatis have mainly been studied using reference strains propagated in cultured cells. Here, using five low-passage-number C. trachomatis clinical isolates that originated from asymptomatic or symptomatic female patients, the in vitro expression of the ompA , cpaf , tarp , and tox genes was studied with reverse transcriptase real-time PCR during the chlamydial developmental cycle. We observed dissimilarities in the gene expression patterns between the low-passage-number clinical isolates and the reference strains. The expression of ompA and the peak of the tox expression were observed earlier in the reference strains than in most of the clinical isolates. The expression of cpaf was high in the reference strains compared with the clinical isolates at the mid-phase (6-24 hours post infection) of the developmental cycle. All of the strains had a rather similar tarp expression profile. Four out of five clinical isolates exhibited slower growth kinetics compared with the reference strains. The use of low-passage-number C. trachomatis clinical isolates instead of reference strains in the studies might better reflect the situation in human infection., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Community-acquired pneumonia (CAP) is a common disease responsible for significant morbidity and mortality. However, the definite etiology of CAP often remains unresolved, suggesting that unknown agents of pneumonia remain to be identified. The recently discovered members of the order Chlamydiales, Chlamydia-related bacteria (CRB), are considered as possible emerging agents of CAP. Parachlamydia acanthamoebae is the most studied candidate. It survives and replicates inside free-living amoeba, which it might potentially use as a vehicle to infect animals and humans. A Mycoplasma pneumoniae outbreak was observed in Kymenlaakso region in Southeastern Finland during August 2017-January 2018. We determined the occurrence of Chlamydiales bacteria and their natural host, free-living amoeba in respiratory specimens collected during this outbreak with molecular methods. Altogether, 22/278 (7.9%) of the samples contained Chlamydiales DNA. By sequence analysis, majority of the CRBs detected were members of the Parachlamydiaceae family. Amoebal DNA was not detected within the sample material. Our study further proposes that Parachlamydiaceae could be a potential agent causing atypical CAP in children and adolescents.

Since February 2019, over 160 Chlamydia trachomatis (CT) cases testing negative or equivocal by Aptima Combo 2 (AC2) but positive by Aptima CT test run with Panther instruments occurred in Finland. The AC2 test targets chlamydial 23S rRNA while the CT test targets 16S rRNA. Sequencing of 10 strains revealed a nucleotide substitution in 23S rRNA. The significance of this for the failure of the AC2 test to detect the variant is not yet known.

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The aim was to examine the prevalence of Mycoplasma genitalium and to determine the prevalence of mutations leading to resistance to macrolides and fluoroquinolones in a sexually transmitted infection clinic setting in Finland, and as a service evaluation, to validate the performance of a commercial Aptima® Mycoplasma genitalium assay. Urogenital samples were studied for M. genitalium with an automated commercial Aptima® Mycoplasma genitalium assay on the Panther® system (Hologic), and with an in-house real-time polymerase chain reaction (PCR) (mgpB). Positive specimens were further studied for mutations associated with macrolide resistance within the 23S rRNA gene and the known quinolone resistance-determining regions within genes gyrA, gyrB and parC. Altogether 17/303 (5.6%) of samples contained M. genitalium by either test. Two of the samples positive by the Aptima assay were not detected by the in-house PCR assay, although the internal control (beta-globin gene) was amplified. The Aptima assay gave an invalid result for five samples, all of which were negative by the in-house PCR. Mutations resulting in macrolide resistance were detected in 30.8% of M. genitalium-positive specimens. Prevalence of M. genitalium infections in the specimens tested is similar to that in other parts of Europe, 5.6%. The Aptima® Mycoplasma genitalium assay detected slightly more positives than the in-house PCR assay. Mutations resulting in macrolide resistance were common in M. genitalium and detection of these mutations is recommended in diagnostic laboratories to assist in selection of treatment.

Phosphatidylinositol (PI) is the precursor of many important signaling molecules in eukaryotic cells and, most probably, PI also has important functions in cellular membranes. However, these functions are poorly understood, which is largely due to that i ) only few PI species with specific acyl chains are available commercially and ii ) there are no simple methods to synthesize such species. Here, we present a simple biochemical protocol to synthesize a variety of labeled or unlabeled PI species from corresponding commercially available phosphatidylcholines. The protocol can be carried out in a single vial in a two-step process which employs three enzymatic reactions mediated by i ) commercial phospholipase D from Streptomyces chromofuscus , ii ) CDP-diacylglycerol synthase overexpressed in E. coli and iii ) PI synthase of Arabidopsis thaliana ectopically expressed in E. coli The PI product is readily purified from the reaction mixture by liquid chromatography since E. coli does not contain endogenous PI or other coeluting lipids. The method allows one to synthesize and purify labeled or unlabeled PI species in 1 or 2 days.Typically, 40-60% of (unsaturated) PC was converted to PI albeit the final yield of PI was less (25-35%) due to losses upon purification., (Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.)

Chlamydia-like organisms (CLOs) are recently identified members of the Chlamydiales order. CLOs share intracellular lifestyles and biphasic developmental cycles, and they have been detected in environmental samples as well as in various hosts such as amoebae and arthropods. In this study, we screened bat feces for the presence of CLOs by molecular analysis. Using pan-Chlamydiales PCR targeting the 16S rRNA gene, Chlamydiales DNA was detected in 54% of the specimens. PCR amplification, sequencing, and phylogenetic analysis of the 16S rRNA and 23S rRNA genes were used to classify positive specimens and infer their phylogenetic relationships. Most sequences matched best with Rhabdochlamydia species or uncultured Chlamydia sequences identified in ticks. Another set of sequences matched best with sequences of the Chlamydia genus or uncultured Chlamydiales from snakes. To gain evidence of whether CLOs in bat feces are merely diet borne, we analyzed insects trapped from the same location where the bats foraged. Interestingly, the CLO sequences resembling Rhabdochlamydia spp. were detected in insect material as well, but the other set of CLO sequences was not, suggesting that this set might not originate from prey. Thus, bats represent another potential host for Chlamydiales and could harbor novel, previously unidentified members of this order., Importance: Several pathogenic viruses are known to colonize bats, and recent analyses indicate that bats are also reservoir hosts for bacterial genera. Chlamydia-like organisms (CLOs) have been detected in several animal species. CLOs have high 16S rRNA sequence similarity to Chlamydiaceae and exhibit similar intracellular lifestyles and biphasic developmental cycles. Our study describes the frequent occurrence of CLO DNA in bat feces, suggesting an expanding host species spectrum for the Chlamydiales As bats can acquire various infectious agents through their diet, prey insects were also studied. We identified CLO sequences in bats that matched best with sequences in prey insects but also CLO sequences not detected in prey insects. This suggests that a portion of CLO DNA present in bat feces is not prey borne. Furthermore, some sequences from bat droppings not originating from their diet might well represent novel, previously unidentified members of the Chlamydiales order., (Copyright © 2016 American Society for Microbiology.)

Mammalian cells maintain the glycerophospholipid (GPL) compositions of their membranes nearly constant. To achieve this, GPL synthesis and degradation must be coordinated. There is strong evidence that A-type phospholipases (PLAs) are key players in homeostatic degradation of GPLs, but the identities of the PLAs involved have not been established. However, some members of the Patatin-like phospholipase domain-containing proteins (PNPLAs) have been implicated. Accordingly, we knocked down all the PNPLAs significantly expressed in human HeLa cells using RNA interference and then determined whether the turnover of the major glycerophospholipids is affected by using mass spectrometry and metabolic labeling with stable isotope-labeled precursors. Knockdown of PNPLA9, PNPLA6 or PNPLA4 significantly (30-50%) reduced the turnover of phosphatidylcholine, -ethanolamine and -serine. In a notable contrast, turnover of phosphatidylinositol was not significantly affected by the knockdown of any PNPLA. Depletion of PNPLA9 and PNPLA4 also inhibited G0/G1 to S cell cycle progression, which could thus be regulated by GPL turnover. These results strongly suggest that PNPLA9, -6 and -4 play a key role in GPL turnover and homeostasis in human cells. A hypothetical model suggesting how these enzymes could recognize the relative concentration of the different GPLs is proposed., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Ticks carry several human pathogenic microbes including Borreliae and Flavivirus causing tick-born encephalitis. Ticks can also carry DNA of Chlamydia-like organisms (CLOs). The purpose of this study was to investigate the occurrence of CLOs in ticks and skin biopsies taken from individuals with suspected tick bite. DNA from CLOs was detected by pan-Chlamydiales-PCR in 40% of adult ticks from southwestern Finland. The estimated minimal infection rate for nymphs and larvae (studied in pools) was 6% and 2%, respectively. For the first time, we show CLO DNA also in human skin as 68% of all skin biopsies studied contained CLO DNA as determined through pan-Chlamydiales-PCR. Sequence analyses based on the 16S rRNA gene fragment indicated that the sequences detected in ticks were heterogeneous, representing various CLO families; whereas the majority of the sequences from human skin remained "unclassified Chlamydiales" and might represent a new family-level lineage. CLO sequences detected in four skin biopsies were most closely related to "uncultured Chlamydial bacterium clones from Ixodes ricinus ticks" and two of them were very similar to CLO sequences from Finnish ticks. These results suggest that CLO DNA is present in human skin; ticks carry CLOs and could potentially transmit CLOs to humans., Competing Interests: The authors declare no conflict of interest.

APS1/APECED patients are defined by defects in the autoimmune regulator (AIRE) that mediates central T cell tolerance to many self-antigens. AIRE deficiency also affects B cell tolerance, but this is incompletely understood. Here we show that most APS1/APECED patients displayed B cell autoreactivity toward unique sets of approximately 100 self-proteins. Thereby, autoantibodies from 81 patients collectively detected many thousands of human proteins. The loss of B cell tolerance seemingly occurred during antibody affinity maturation, an obligatorily T cell-dependent step. Consistent with this, many APS1/APECED patients harbored extremely high-affinity, neutralizing autoantibodies, particularly against specific cytokines. Such antibodies were biologically active in vitro and in vivo, and those neutralizing type I interferons (IFNs) showed a striking inverse correlation with type I diabetes, not shown by other anti-cytokine antibodies. Thus, naturally occurring human autoantibodies may actively limit disease and be of therapeutic utility., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

The A-type phospholipases (PLAs) are key players in glycerophospholipid (GPL) homeostasis and in mammalian cells; Ca(2+)-independent PLA-β (iPLAβ) in particular has been implicated in this essential process. However, the regulation of this enzyme, which is necessary to avoid futile competition between synthesis and degradation, is not understood. Recently, we provided evidence that the efflux of the substrate molecules from the bilayer is the rate-limiting step in the hydrolysis of GPLs by some secretory (nonhomeostatic) PLAs. To study whether this is the case with iPLAβ as well, a mass spectrometric assay was employed to determine the rate of hydrolysis of multiple saturated and unsaturated GPL species in parallel using micelles or vesicle bilayers as the macrosubstrate. With micelles, the hydrolysis decreased with increasing acyl chain length independent of unsaturation, and modest discrimination between acyl positional isomers was observed, presumably due to the differences in the structure of the sn-1 and sn-2 acyl-binding sites of the protein. In striking contrast, no significant discrimination between positional isomers was observed with bilayers, and the rate of hydrolysis decreased with the acyl chain length logarithmically and far more than with micelles. These data provide compelling evidence that efflux of the substrate molecule from the bilayer, which also decreases monotonously with acyl chain length, is the rate-determining step in iPLAβ-mediated hydrolysis of GPLs in membranes. This finding is intriguing as it may help to understand how homeostatic PLAs are regulated and how degradation and biosynthesis are coordinated., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Heavy isotope-labeled ethanolamine and serine as well as exogenous PE and PS species were used to study trafficking of phosphatidylethanolamine (PE) and -serine (PS) molecular species between the endoplasmic reticulum (ER) and mitochondria in HeLa cells. Import of both endogenous and exogenous PS to IMM was a relatively slow process (T1/2=several hours), but depended on the acyl chains. In particular, the 38:4 and 38:5 species were imported more efficiently compared to the other PS species. Knock-down of Mitofusin 2 or Mitostatin had no detectable effect on PS import to mitochondria, suggesting that the ER-mitochondria contacts regulated by these proteins are not essential. Knock-down of PS synthase 1 inhibited PS decarboxylation, suggesting that import of PS to mitochondria is coupled to its synthesis. Also the export of PE from IMM to microsomes is a relatively slow process, but again depends markedly on the acyl chain structure. Most notably, the polyunsaturated 38:4 and 38:5 PE species were less efficiently exported, which together with rapid import of the PS precursors most probably explains their enrichment in IMM. PE synthesized via the CDP-ethanolamine was also imported to IMM, but most of the PE in this membrane derives from imported PS. In contrast to PS, all PC species made in Golgi/ER translocated similarly and rapidly to IMM. In conclusion, selective translocation of PS species and PS-derived PE species between ER and mitochondria plays a major role in phospholipid homeostasis of these organelles., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The membranes of mammalian cells contain hundreds of different phospholipid species, a variety of glycolipids and cholesterol. While the reasons for such compositional diversity are not well established, they probably relate to a multitude of membrane-associated functions each of which sets specific requirements for the chemical and physical properties of membranes. The lipid composition of membranes must therefore be accurately controlled. The maintenance of phospholipid homeostasis in a mammalian cell is a daunting task due to presence of many phospholipid (and other lipid) classes and hundreds of different molecular species. In addition, the phospholipid composition of the cellular membranes depends on several different phenomena including biosynthesis, remodelling, degradation and interorganelle trafficking. Accordingly, it is not surprising that phospholipid homeostasis in mammalian cells is poorly understood. Particularly little is known about the regulation and coordination of processes contributing to homeostasis. Nevertheless, it has become obvious that selective degradation plays a major role, albeit the enzymes involved remain to be discovered. Beside the complexity of the phenomenon, methodological limitations have hampered the progress in this field. Here, we review the key features of the processes contributing to phospholipid homeostasis in mammalian cells, with a particular emphasis on the regulation and coordination of biosynthesis and degradation., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The human parvovirus B19 is now divided into three genotypes: type 1 (prototype), type 2 (A6- and LaLi-like), and type 3 (V9-like). In overall DNA sequence, the three virus types differ by approximately 10%. The most striking DNA dissimilarity, of >20%, is observed within the p6 promoter region. Because of the scarcity of data on the biological activities and pathogenetic potentials of virus types 2 and 3, we examined the functional characteristics of these virus types. We found the activities of the three p6 promoters to be of equal strength and to be most active in B19-permissive cells. Virus type 2 capsid protein VP2, alone or together with VP1, was expressed with the baculovirus system and was shown to assemble into icosahedral parvovirus-like particles, which were reactive in the hemagglutination assay. Furthermore, sera containing DNA of any of the three B19 types were shown to hemagglutinate. The infectivities of these sera were examined in two B19-permissive cell lines. Reverse transcription-PCR revealed synthesis of spliced B19 mRNAs, and immunofluorescence verified the production of NS and VP proteins in the infected cells. All three genotypes showed similar functional characteristics in all experiments performed, showing that the three virus types indeed belong to the same species, i.e., human parvovirus B19. Additionally, the antibody activity in sera from B19 type 1- or type 2-infected subjects (long-term immunity) was examined with homo- and heterologous virus-like particles. Cross-reactivity of 100% was observed, indicating that the two B19 genotypes comprise a single serotype.

Human erythrovirus is a minute, single-stranded DNA virus causing many diseases, including erythema infectiosum, arthropathy, and fetal death. After primary infection, the viral genomes persist in solid tissues. Besides the prototype, virus type 1, two major variants (virus types 2 and 3) have been identified recently, the clinical significance and epidemiology of which are mostly unknown. We examined 523 samples of skin, synovium, tonsil, or liver (birth year range, 1913-2000), and 1,640 sera, by qualitative and quantitative molecular assays for the DNA of human erythroviruses. Virus types 1 and 2 were found in 132 (25%) and 58 (11%) tissues, respectively. DNA of virus type 1 was found in all age groups, whereas that of type 2 was strictly confined to those subjects born before 1973 (P < 0.001). Correspondingly, the sera from the past two decades contained DNA of type 1 but not type 2 or 3. Our data suggest strongly that the newly identified human erythrovirus type 2 as well as the prototype 1 circulated in Northern and Central Europe in equal frequency, more than half a century ago, whereafter type 2 disappeared from circulation. Type 3 never attained wide occurrence in this area during the past > or =70 years. The erythrovirus DNA persistence in human tissues is lifelong and represents a source of information about our past, the Bioportfolio, which, at the individual level, provides a registry of one's infectious encounters, and at the population level, a database for epidemiological and phylogenetic analyses.

Parvovirus B19 causes a variety of diseases in humans, with outcomes ranging from asymptomatic to severe, such as chronic anemia in immunocompromised patients or fetal hydrops and death after maternal infection during pregnancy. The virus may be transmitted via plasma-derived products. According to the results of solvent-detergent safety studies, an upper limit of B19 DNA in plasma pools was recently defined. To restrict the input of B19 virus into production pools, a quantitative nucleic acid test is a prerequisite. We examined the suitability of the two commercial quantitative B19 PCR tests, LightCycler-Parvovirus B19 quantification kit (Roche Diagnostics) and RealArt Parvo B19 LC PCR (Artus) for detection, quantification, and differentiation of the three known B19 genotypes, including the newly described erythrovirus variants (genotypes 2 and 3). The former kit was highly sensitive for genotype 1 but was not suitable for detection of genotype 2 or one of two genotype 3 strains. The latter kit detected and differentiated all three genotypes, albeit with lower sensitivity for one of the genotype-3 strains. We furthermore assessed the prevalence of the three B19 virus genotypes in blood donors, by screening pooled plasma samples derived from 140,160 Finnish blood-donor units. None of the pools contained detectable levels of B19 virus genotypes 2 or 3. The origin, mode of transmission, and clinical significance of these genotypes are unknown and deserve further study. The RealArt Parvo B19 LC PCR is suitable for detection, quantification, and differentiation of all three B19 virus genotypes in molecular and clinical research.

Parvovirus B19 is the exclusive human pathogen of the Erythrovirus genus. In classical view, the B19 DNA sequence shows little variability, with no disease-specific or tissue type specific associations. We examined skin biopsies from patients with B19-unrelated skin disease or from constitutionally healthy adults by polymerase chain reaction assays for four different genomic regions of the B19 virus. Sequencing showed that the skin-derived viral DNA differed within the protein-coding region from the B19 reference sequences by 10.8% and from the V9 variant by 8.6% and within the noncoding region (covering nucleotides 189-435 of the promoter region) by 26.5 and 17.2%, respectively. Despite this sequence difference, the promoter region was shown by a luciferase gene expression assay to be biologically active. We have detected a new B19 virus genotype, K71, which differs extensively from the known B19-virus genotypes and is persistently carried in human skin.

Human parvovirus B19 infection causes various clinical symptoms, such as rash, arthropathy, anemias and fetal death, but it can also remain asymptomatic. The arthropathies and anemias can become chronic for several years, not infrequently resembling autoimmune syndromes. B19 replicates only in red blood cell precursors of bone marrow or fetal liver, resulting in high-titred short-lived viremia, but viral DNA is detectable also in cells of several other types. Recently B19 DNA has been found, by very sensitive amplification tests, in certain tissues not only of symptomatic but also of healthy individuals for several years or decades after B19 infection. The mere presence of B19 DNA in these tissues of a symptomatic patient (e.g. joints in chronic arthritis or skin in dermatomyositis) thereby does not prove that the present disease is caused by B19. The diagnosis has to be verified by other innovative means. How and why viral DNA persists in the tissues of healthy individuals is under investigation.

T cell proliferation to human parvovirus B19 antigen was measured in 6 patients with recent B19 infection (1 with pneumonia and pleuritis), 1 patient with symptoms persisting >180 days after onset, 18 nonsymptomatic subjects with remote B19 immunity, and 12 B19-seronegative control subjects. Recombinantly expressed virus-like particles (VP1/2 capsids), a candidate B19 vaccine, were used as antigen. Virus-specific T helper cell proliferation was detectable in all the recently infected patients and in most (17/18) of the remotely infected subjects but not in the seronegative control subjects. The B19-specific T cell responses, in general, were most vigorous among the recently infected patients. However, such strong B19-specific proliferation was not confined within the acute phase, as 28% (5/18) of the remotely infected healthy individuals had B19-specific reactivity persisting at acute-phase levels, apparently for years or decades. These data indicate that B cells recognizing the VP1/2 capsids receive class II-restricted help from CD4(+) T lymphocytes.

Primary infection by human parvovirus B19 is often accompanied by arthropathy of varying duration, of which the most severe cases can be indistinguishable from rheumatoid arthritis (RA). While this might seem to imply a role in RA pathogenesis, recent studies have verified long-term persistence of B19 DNA in synovial tissue not only in patients with rheumatoid or juvenile arthritis, but also in immunocompetent, non-arthritic individuals with a history of prior B19 infection. However, the latter data are based on PCR amplification of short segments of DNA, with little sequence information. We determined the nucleotide sequence and examined the integrity of the protein-coding regions of B19 genomes persisting in synovial tissue and compared the results with data from synovial tissues of recently infected patients. In synovium of both previously and recently infected subjects, the viral coding regions were found to be present in an apparently continuous, intact DNA molecule. Comparison with sequences reported from blood or bone marrow showed that the synoviotropism or persistence of the B19 virus DNA was not due to exceptional mutations or particular genotype variants. The synovial retention of full-length viral genomes may represent a physiological process functioning in long-term storage of foreign macromolecules in this tissue.

The major capsid protein VP2 of human parvovirus B19, when studied in a denatured form exhibiting linear epitopes, is recognized exclusively by immunoglobulin G (IgG) antibodies of patients with acute or recent B19 infection. By contrast, conformational epitopes of VP2 are recognized both by IgG of the acute phase and by IgG of past immunity. In order to localize the VP2 linear epitope(s) specific for acute-phase IgG, the entire B19 capsid protein sequence was mapped by peptide scanning using well-characterized acute-phase and control sera. A unique heptapeptide epitope showing strong and selective reactivity with the acute-phase IgG was detected and characterized. By using this linear epitope (VP2 amino acids 344 to 350) and virus-like particles exhibiting conformational VP2 epitopes, an innovative approach, second-generation epitope-typing enzyme immunoassay, was set up for improved diagnosis of primary infections by human parvovirus B19.