Rapid syndromic PCR testing in patients with respiratory tract infections reduces time to results and improves microbial yield.

Lack of rapid and comprehensive microbiological diagnosis in patients with community acquired pneumonia (CAP) hampers appropriate antimicrobial therapy. This study evaluates the real-world performance of the BioFire FilmArray Pneumonia panel plus (FAP plus) and explores the feasibility of evaluation in a randomised controlled trial. Patients presenting to hospital with suspected CAP were recruited in a prospective feasibility study. An induced sputum or an endotracheal aspirate was obtained from all participants. The FAP plus turnaround time (TAT) and microbiological yield were compared with standard diagnostic methods (SDs). 96/104 (92%) enrolled patients had a respiratory tract infection (RTI); 72 CAP and 24 other RTIs. Median TAT was shorter for the FAP plus, compared with in-house PCR (2.6 vs 24.1 h, p < 0.001) and sputum cultures (2.6 vs 57.5 h, p < 0.001). The total microbiological yield by the FAP plus was higher compared to SDs (91% (162/179) vs 55% (99/179), p < 0.0001). Haemophilus influenzae, Streptococcus pneumoniae and influenza A virus were the most frequent pathogens. In conclusion, molecular panel testing in adults with CAP was associated with a significant reduction in time to actionable results and increased microbiological yield. The impact on antibiotic use and patient outcome should be assessed in randomised controlled trials.

The bacterial aetiology of pleural empyema. A descriptive and comparative metagenomic study.

OBJECTIVES: The view of pleural empyema as a complication of bacterial pneumonia is changing because many patients lack evidence of underlying pneumonia. To further our understanding of pathophysiological mechanisms, we conducted in-depth microbiological characterization of empyemas in clinically well-characterized patients and investigated observed microbial parallels between pleural empyemas and brain abscesses. METHODS: Culture-positive and/or 16S rRNA gene PCR-positive pleural fluids were analysed using massive parallel sequencing of the 16S rRNA and rpoB genes. Clinical details were evaluated by medical record review. Comparative analysis with brain abscesses was performed using metagenomic data from a national Norwegian study. RESULTS: Sixty-four individuals with empyema were included. Thirty-seven had a well-defined microbial aetiology, while 27, all of whom had community-acquired infections, did not. In the latter subset, Fusobacterium nucleatum and/or Streptococcus intermedius was detected in 26 patients, of which 18 had additional facultative and/or anaerobic species in various combinations. For this group, there was 65.5% species overlap with brain abscesses; predisposing factors included dental infection, minor chest trauma, chronic obstructive pulmonary disease, drug abuse, alcoholism and diabetes mellitus. Altogether, massive parallel sequencing yielded 385 bacterial detections, whereas culture detected 38 (10%) and 16S rRNA gene PCR/Sanger-based sequencing detected 87 (23%). CONCLUSIONS: A subgroup of pleural empyema appears to be caused by a set of bacteria not normally considered to be involved in pneumonia. Such empyemas appear to have a similar microbial profile to oral/sinus-derived brain abscesses, supporting spread from the oral cavity, potentially haematogenously. We suggest reserving the term 'primary empyema' for these infections.

Increased infiltration and tolerised antigen-specific CD8+ TEM cells in tumor but not peripheral blood have no impact on survival of HCMV+ glioblastoma patients.

Human cytomegalovirus (HCMV) antigens in glioblastoma (GBM) present opportunities for personalised immunotherapy. However, their presence in GBM tissue is still under debate, and evidence of their impact on functional immune responses and prognosis is sparse. Here, we investigated the presence of pp65 (UL83) and immediate early 1 (IE-1) HCMV antigens in a cohort of Norwegian GBM patients (n = 177), using qPCR, immunohistochemistry, and serology. HCMV status was then used to investigate whether viral antigens influenced immune cell phenotype, infiltration, activation and patient survival. Pp65 and IE-1 were detected by qPCR in 23% and 43% of GBM patients, respectively. Furthermore, there was increased seropositivity in GBM patients relative to donors (79% vs. 48%, respectively; Logistic regression, OR = 4.05, 95%CI [1.807-9.114], P = 0.001, also when adjusted for age (OR = 2.84, 95%CI [1.110-7.275], P = 0.029). Tissue IE-1-positivity correlated with increased CD3+CD8+ T-cell infiltration (P < 0.0001), where CD8+ effector memory T (TEM) cells accounted for the majority of CD8+T cells compared with peripheral blood of HCMV+ patients (P < 0.0001), and HCMV+ (P < 0.001) and HCMV- (P < 0.001) donors. HLA-A2/B8-restricted HCMV-specific CD8+ T cells were more frequent in blood and tumor of HCMV+ GBM patients compared with seronegative patients, and donors irrespective of their serostatus. In biopsies, the HCMV-specific CD8+ TEM cells highly expressed CTLA-4 and PD-1 immune checkpoint protein markers compared with populations in peripheral blood (P < 0.001 and P < 0.0001), which expressed 3-fold greater levels of CD28 (P < 0.001 and P < 0.0001). These peripheral blood T cells correspondingly secreted higher levels of IFNγ in response to pp65 and IE-1 peptide stimulation (P < 0.001). Thus, despite apparent increased immunogenicity of HCMV compared with tumor antigens, the T cells were tolerised, and HCMV status did not impact patient survival (Log Rank3.53 HR = 0.85 95%CI [0.564-1.290], P = 0.45). Enhancing immune functionality in the tumor microenvironment thus may improve patient outcome.

Mycobacterium tuberculosis Mce1 protein complex initiates rapid induction of transcription of genes involved in substrate trafficking.

The mammalian cell entry (Mce)1 protein complex has an important role during the initial phase of a Mycobacterium tuberculosis (M. tuberculosis) infection. Murine macrophages were infected with M. tuberculosis H37Rv or Δ-mce1 H37Rv, and total RNA was isolated from the host cells at 15, 30 and 60 min, and 4 and 10 h post-infection. With the aim of studying the role for the Mce1 protein complex on host gene expression, the RNA was hybridized onto 44 K whole-genome microarrays. Selected genes were verified by reverse-transcriptase quantitative PCR (RT-QPCR). 'Transport' was the most overrepresented biological process during the first hour post H37Rv infection. Five genes (Abca1 (21.0-fold), Slc16a10 (3.1-fold), Slc6a12 (17.9-fold), Slc6a8 (2.3-fold) and Nr1h3, (5.5-fold)) involved in substrate trafficking were verified by RT-QPCR to be upregulated by >2-fold 1 h post H37Rv infection. By 1 h post Δ-mce1 H37Rv infection, only Abca1 and Slc6a12 were upregulated by >2-fold. A number of other genes, which may be directly involved in substrate trafficking or share the same transcription, were found to have expression profiles similar to the genes involved in substrate trafficking. The Mce1 protein complex has a significant role in the transcriptional activation of genes involved in substrate trafficking during the initial phase of an M. tuberculosis infection.

Fcγ receptors in Norwegian multiple sclerosis patients and healthy controls.

BACKGROUND: Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system in genetically susceptible persons. Fcγ receptors (FcγR) are involved in autoimmune diseases. PATIENTS AND METHODS: Sixteen Norwegian patients with relapsing-remitting MS (RRMS) were studied to see whether treatment with either interferon-beta (INF-ß) or glatiramer acetate (GA) influenced the proportion of FcγR1a, FcγR2a, and FcγR3b positive monocytes, granulocytes, or lymphocytes or FcγR1a, FcγR2a, and FcγR2b mRNA levels in leukocytes. One hundred and twenty-seven patients with RRMS and 54 Norwegian healthy blood donors were also analyzed for FcγR2b polymorphisms. RESULTS: Interferon-beta or GA treatment initiated an increase in the proportion of FcγR positive lymphocytes, but did not cause major influence of the long-term proportion of FcγR positive leukocytes or their FcγR mRNA levels. No significant differences were observed between RRMS patients and healthy controls for the genotype and allele frequencies of FcγR2b polymorphisms. DISCUSSION: INF-ß or GA treatment probably has no major role in the regulation of FcγRs on immune cells in RRMS. Furthermore, polymorphisms of the inhibitory FcγR2b do not seem to influence the susceptibility for MS.

Acute suppression of serum IgM and IgA in tank workers exposed to benzene.

We investigated associations between benzene exposure and alterations of proteins and cells of the immune system among workers maintaining cargo tanks containing crude oil residues. Individual exposure to benzene, benzene in blood and urine, peripheral blood lymphocytes (total lymphocytes, lymphocytes in subpopulations CD3, CD4, CD8, CD19, CD56 and CD4/CD8 ratio), complement factors C3 and C4 and serum concentration of immunoglobulins (IgG, IgA, IgM and IgE) were analysed among 13 tank workers and nine unexposed referents (catering section). Benzene exposure was measured during three consecutive 12-h work days. Blood and urine samples were collected pre-shift on the first day (baseline), post-shift on the third day, and pre-next shift on the following morning. The time spent in the cargo tank was logged. The individual geometric mean benzene exposure in the breathing zone of tank workers over 3 days was 0.15 p.p.m. (range 0.01-0.62 p.p.m.) (n = 26). The geometric mean benzene concentration in blood post-shift was 12.3 nmol/l among tank workers versus 0.7 nmol/l among the referents. Tank workers showed a decline (versus referents) in IgM from baseline to post-shift (t-test, P = 0.04) and IgA from baseline to pre-next shift (t-test, P = 0.01). They also showed a decline in CD4 T cells from baseline to post-shift (t-test, P = 0.04). Suppression correlated with benzene exposure, benzene concentrations in blood and urine and time spent in the tank. The groups did not differ significantly in the change in other immune parameters. The clinical significance is unknown and warrants further studies.

High dose methylprednisolone induces FcgammaRI on granulocytes in MS-patients.

Immune complexes impinge on receptors for the Fc domain of IgG (FcgammaR) and may thus influence the disease course in multiple sclerosis (MS). We analyzed FcgammaR distribution on monocytes and granulocytes in twenty relapsing-remitting MS patients at baseline, immediately after a five day course of high dose intravenous methylprednisolone (IVMP) treatment and after two months. After a five day course of IVMP the proportion of granulocytes with FcgammaRI was increased, P=0,002. There was no change in FcgammaRII and FcgammaRIII expression. The effect of IVMP on FcgammaRI expression could be important for the clearance of immune complexes in MS.

IL-6: an early marker for outcome in acute ischemic stroke.

OBJECTIVES: Inflammation plays an important role in the pathophysiology of stroke. We correlated interleukin (IL)-6, IL-10, C-reactive protein (CRP) and T-lymphocyte subtype levels in acute ischemic stroke patients with stroke volume and clinical outcome. MATERIALS AND METHODS: Blood samples were obtained from 11 patients at defined intervals during 1 year. Nine healthy age-matched subjects served as controls. IL-6, IL-10 and CRP were quantified by enzyme-linked immunosorbent assay and T lymphocytes by flow cytometry. Volume measurement was carried out by computed tomography or magnetic resonance imaging and clinical outcome was scored by the European stroke scale (ESS) and Barthel index (BI). RESULTS: IL-6 levels were increased in the acute phase of stroke compared with healthy controls (P = 0.002) and correlated with larger stroke volume (P = 0.012) and less favorable prognosis after 1 year, measured by ESS (P = 0.014) and BI (P = 0.006). IL-10, CRP and T-lymphocyte subtypes in the acute phase were not correlated with stroke volume or clinical outcome. CONCLUSION: IL-6 seems to be a robust early marker for outcome in acute ischemic stroke.

Characterization of ribosomal P autoantibodies in relation to cell destruction and autoimmune disease.

Autoantibodies against the ribosomal P proteins are related to cell death and tissue destruction and are frequently exhibited in patients with systemic lupus erythematosus (SLE). In an attempt to explore the effect of tissue destruction on the induction of anti-P autoantibodies, we searched for anti-P autoantibodies by enzyme-linked immunosorbent assay in 201 antinuclear antibody (ANA)-positive individuals, in 10 patients with treated kidney SLE and in 45 acute leukaemia patients undergoing intensive chemotherapy. The autoantibody reactivity was further characterized using one- and two-dimensional immunoblot analysis and immunofluorescence. Anti-P were detected in 5.5% (11/201) of ANA-positive individuals, but not in kidney-affected SLE patients or in patients with leukaemia. Seven of 11 anti-P-positive patients had SLE (3/11), primary Sjögrens's syndrome (1/11) and other autoimmune diseases (3/11). A relation between disease activity and anti-P was suggested by follow-up examinations in one SLE patient, supported by the absence of anti-P autoantibodies in the 10 treated kidney SLE patients. Anti-P autoantibodies were detected by immunoblot in one patient with SLE indicating anti-P2 predominance and in the patient with Sjögrens's syndrome indicating anti-P1 predominance. Diverging humoral responses in these ANA- and anti-P-positive patients were further illustrated by immunofluorescence, elucidating varying nuclear reactivity and anti-P pattern. The observation of anti-P in individuals with active autoimmune disease, but not in patients with chemotherapy-induced cell damage, suggests that anti-P antibodies are part of a specific disease process, and not elicited as a response to cell destruction per se.

Immunoglobulin levels amongst persons with and without human immunodeficiency virus type 1 infection in Uganda and Norway.

CD4+-cell count and viral load monitoring are expensive and unavailable to most human immunodeficiency virus (HIV)-infected people in Africa. In an attempt to evaluate alternative methods for monitoring antiretroviral (ARV) therapy, we measured concentrations of immunoglobulin (Ig)A, IgM, IgG and IgG1 amongst adults with and without HIV in Uganda and Norway. We adjusted for disease severity by stratifying HIV-positive subjects on CD4+-cell counts above and below 200 cells/ micro l. Median serum levels of IgG, IgG1 and IgA were significantly higher in HIV-positive persons compared with HIV-negative persons in both countries (P < 0.001 and P = 0.018 for IgA in Ugandan patients). Levels of IgA in Ugandan HIV-negative subjects were significantly lower than those in HIV-positive subjects with low CD4+ compared with those with high CD4+-cell counts (P < 0.001 and P = 0.069, respectively). IgM levels were different between the HIV-negative and the two HIV-positive groups in Norway (P < 0.001). The mean levels of IgM, IgG and IgG1 in HIV-negative and -positive African subjects were generally higher than those in comparable groups of Western subjects. Our results verify that levels of IgA, IgG and IgG1 vary between HIV-negative and -positive individuals in both study populations. Their determination may be useful in monitoring both disease progression and response to ARV therapy.

The effects of interferon-alpha2a on concentrations of immunoglobulins, complement and lymphocytes in patients with multiple sclerosis.

Multiple sclerosis (MS) patients treated with type I interferon experience reduced disease activity. Because immunoglobulins (Igs), complement and lymphocytes have been given a role in the pathogenesis of MS, we investigated the longitudinal effect of interferon-alpha2a (IFNA) on the variability of these parameters. Patients were treated for 6 months with 4.5 million international units (MIU) IFNA (24 patients), 9.0 MIU IFNA (21 patients) or placebo (23 patients). IFNA induced a significant increase in concentrations of total IgG and IgG subclasses 1, 3 and 4. At 6 months, the mean concentration of IgG had increased by 1.51 g/l (CI: 0.82, 2.21) in the 9.0 MIU IFNA group. There was no significant effect of IFNA treatment on concentrations of IgG2 and IgA, while the effect on IgM was borderline significant. After 6 months, IgM had increased by 0.29 g/l (CI: -0.01, 0.65) in the 9.0 MIU IFNA group. IFNA induced a significant increase in the concentration of C1 inhibitor (INH). At 3 months, the mean concentration of C1 INH had increased by 0.033 g/l (CI: 0.01, 0.05). At 3 months, C4 had increased by 0.05 g/l (CI: 0.01, 0.09) in the 9.0 MIU IFNA group. The effect of IFNA on C4 was inconclusive but indicates an effect during the initial phase of the treatment. C3 showed no significant treatment-mediated change. IFNA induced a significant decrease in lymphocyte concentrations by 0.56 x 106 lymphocytes/ml (CI: -0.81, -0.31) at 3 months. There were no significant associations between changes in immune parameters and changes in clinical and magnetic resonance imaging scores. The results verify that IFNA modulates and activates both the innate and the adaptive arms of the immune system. The observations should be of relevance when evaluating mechanisms of action of IFN treatment in MS.

The immune response to pneumococcal polysaccharide vaccine in zinc-depleted mice.

Zinc depletion affects several facets of the immune system and the resistance to infections. We assessed the effect of zinc deprivation on the immune response to the pneumococcal polysaccharide antigens in the commercially available Pneumovax pneumococcal vaccine. Young female BALB/c mice were fed diets with 2.7, 5.8 or 25 micro g of elemental zinc per mg diet. After six weeks of pair feeding, there were significant differences in the mean body weights between the feeding groups and we demonstrated a dose response of the zinc level in the diet on growth. The induced zinc deficiency had no discernible effect on the antipneumococcal polysaccharide immunoglobulin M (IgM) response following immunization with the pneumococcal vaccine. Although zinc depletion has a detrimental effect on the immune system, the murine T-cell-independent response to antigens such as those in the pneumococcal polysaccharide capsule does not seem to be affected.

Modelling autoimmune rheumatic disease: a likelihood rationale.

Immunoglobulins (Igs) and autoantibodies are commonly tested in sera from patients with suspected rheumatic disease. To evaluate the clinical utility of the tests in combination, we investigated sera from 351 patients with autoimmune rheumatic disease (ARD) rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS) and 96 patients with nonautoimmune rheumatic disease (NAD) (fibromyalgia, osteoarthritis, etc.). Antinuclear antibodies (ANA), rheumatoid factor (RF), antibodies against DNA and extractable nuclear antigens (anti-ENA), IgG, IgA and IgM were measured for all patients. Logistic regression analysis of test results was used to calculate each patient's probability for belonging to the ARD or NAD group as well as likelihood ratios for disease. Test accuracy was investigated using receiver-operating characteristic (ROC) plots and nonparametric ROC analysis. Neither concentrations of IgG, IgA, IgM, anti-DNA nor anti-ENA gave a significant effect on diagnostic outcome. Probabilities for disease and likelihood ratios calculated by combining RF and ANA performed significantly better at predicting ARD than utilization of the diagnostic tests in isolation (P < 0.001). At a cut-off level of P = 0.73 and likelihood ratio = 1, the logistic model gave a specificity of 93% and a sensitivity of 75% for the differentiation between ARD and NAD. When compared at the same level of specificity, ANA gave a sensitivity of 37% and RF gave a sensitivity of 56.6%. Dichotomizing ANA and RF as positive or negative did not reduce the performance characteristics of the model. Combining results obtained from serological analysis of ANA and RF according to this model will increase the diagnostic utility of the tests in rheumatological practice.

The evolution and breakdown of the immune system: implications for development of autoimmune diseases.

At the most recent meeting of the Scandinavian Society for Immunology in Bergen, one of the major target phenomena was autoimmune diseases. The approach started from the evolutionary origins of immunity, went on to review some of the notable advances in molecular architecture of immune processes and finally focussed the findings on autoimmune disease.

Expression of Fc(epsilon)-receptors by human acute myelogenous leukemia (AML) blasts: studies of high- and low- (CD23) affinity receptor expression and the effects of IgE-mediated receptor ligation on functional AML blast characteristics.

Acute myelogenous leukemia (AML) blasts derived from 20 patients were examined for expression of high- (Fc(epsilon)RI) and low-affinity (Fc(epsilon)RII, CD23) IgE Fc(epsilon)-receptors. Fc(epsilon)RI expression was not detected for any patient. In contrast, expression of CD23 (at least 15% of the blasts stained positive) was detected for 6 out of the 20 patients. Acute lymphoblastic leukemia (ALL) blasts derived from 12 patients did not express CD23 (<1% positive cells for all patients). The functional effects of Fc(epsilon)R-receptor ligation were also examined for 20 patients, including the five patients with highest CD23 expression (30-55% positive cells) and five patients with verified low CD23 expression (

Favourable response to therapy with the anti-CD20 monoclonal antibody rituximab in primary chronic cold agglutinin disease.

The 'primary' form of chronic cold agglutinin disease is a clonal B-cell lymphoproliferative disorder that is notoriously difficult to treat with drugs, including corticosteroids, alkylating agents, alpha-interferon and purine analogues. We performed a small, open, uncontrolled, prospective study to evaluate the effect of therapy with the monoclonal anti-CD20 antibody rituximab. Six patients with clonal CD20(+)kappa(+) B-cell proliferation received seven courses of rituximab 375 mg/m(2), d 1, 8, 15, and 22. One patient achieved a complete response. Four partial responses were observed, including a response to re-treatment in one patient. Two patients were categorized as non-responders. Haemoglobin levels increased by a median of 4.1 g/dl in the total group and 4.7 g/dl in the responders, who also experienced a substantial improvement of clinical symptoms. The treatment was well tolerated. We discuss the effect of rituximab therapy compared with other treatment options, and try to explain why two individual patients did not respond. Despite the small numbers, the results are very encouraging. Further studies of rituximab therapy for chronic cold agglutinin disease are warranted.

Platelet-derived growth factor (PDGF) in human acute myelogenous leukemia: PDGF receptor expression, endogenous PDGF release and responsiveness to exogenous PDGF isoforms by in vitro cultured acute myelogenous leukemia blasts.

We investigated effects of Platelet-derived growth factor (PDGF) and Platelet factor 4 (PF-4) on the functional characteristics of native, human acute myelogenous leukemia (AML) blasts. AML blast expression of the PDGF-receptor alpha-chain was detected for a subset of patients (45%), whereas PDGF-receptor beta-chain expression was detected for most patients (90%). Constitutive AML blast release of the PDGF-AB isoform (the major form also derived from normal platelets) was detected for 43% of patients, whereas PDGF-BB release was not detected for any patient. The PDGF isoforms AA, AB and BB had dose-dependent and divergent effects on spontaneous and cytokine-dependent AML blast proliferation, whereas for constitutive cytokine secretion (IL-1beta, IL-6, TNF-alpha) inhibitory effects were rare and all three isoforms usually had no effect or enhanced the constitutive secretion. The PDGF effects were caused by a direct effect on the AML blasts and were not dependent on the presence of serum. The PDGF effects could also be detected after in vitro culture of AML cells in the presence of IL-4+granulocyte-macrophage colony stimulating factor. PF-4 had divergent effects on proliferation and cytokine secretion by native AML blasts. Our results suggest that exogenous (e.g. platelet-secreted) PDGF and PF-4 can function as regulators of leukemic hematopoiesis and possibly also modulate the function of residual AML cells in peripheral blood stem cell grafts. On the other hand, endogenous release of PDGF-AB by native blasts may modulate the function of normal cells in the bone marrow microenvironment (e.g. bone marrow stromal cells).

Acute phase haemolysis in chronic cold agglutinin disease.

We previously described a paradoxical form of chronic cold agglutinin disease (CAD) in which haemolysis occurred during episodes of fever but only marginally during exposure to colds. In order to investigate the molecular basis for this response we performed a 12-month prospective study of a patient with CAD and paradoxical haemolysis. Blood samples were collected monthly during health, and daily following hospitalization owing to hip fracture. During health we observed decreased levels of C3, undetectable C4, a non-functional classical pathway and a normal alternative pathway. Increased concentrations of C1-INH/C1rs complexes indicated continuous formation of C1-antibody-antigen complexes. There was a low-grade temperature-dependent fluctuating haemolysis as evidenced from measurements of lactate dehydrogenase. Following the hip fracture, the haemolysis increased. Levels of interleukin (IL)-1beta, IL-6, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha increased as did C1-INH, C3, C4, CRP, and lactate dehydrogenase. The results support our hypothesis stating that paradoxical haemolysis in CAD is controlled by the availability of early classical pathway complement molecules and that haemolysis following acute phase responses occurs as a consequence of increased complement synthesis.

Performance characteristics and clinical utility of a hybrid ELISA for detection of ANA.

To investigate the clinical utility of a newly developed hybrid ELISA for antinuclear antibodies (ANA), a cross-sectional study of patients admitted to the Section of Rheumatology was initiated. The ELISA was compared to indirect immunofluorescence (IIF) on HEp-2 cells. Accuracy of tests was analyzed using receiver-operating characteristic methodology (ROC). In addition, diagnostic sensitivity, specificity and predictive values were calculated for each assay. Results from the ROC analysis showed a slightly superior accuracy for IIF as compared to ELISA. Furthermore, IIF showed higher diagnostic sensitivity and positive predictive value for all combinations of patients and reference populations. This was due to enhanced detection by IIF, in contrast to ELISA, of diagnostically useful antibodies. IIF detected 87.4% and ELISA detected 84.2% of sera with antibodies against extractable nuclear antigens (ENA). In addition, IIF detected diagnostically important antibodies that are not included among the anti-ENA. The hybrid ELISA either lacks or does not contain the relevant antigens in sufficient amount. Inclusion of these antigens may further enhance the performance characteristics of the ELISA.

Diagnostic and biological significance of anti-p41 IgM antibodies against Borrelia burgdorferi.

We performed a prospective study to investigate the biological significance and diagnostic specificity of anti-p41 immunoglobulin (Ig)M antibodies against Borrelia burgdorferi. During a 1-year interval 2403 patients were referred to our department for B. burgdorferi serology. Sixty-three patients had repetitive positive tests for IgM anti-p41 antibodies and negative tests for anti-p41 IgG antibodies. Ten of the 63 patients recently had symptoms of erythema migrans. A confirmatory IgM Western blot gave a positive reaction in 5 patients out of 53 patients with little or no clinical evidence of B. burgdorferi infection. The remaining 48 patients were negative in this test and were considered as false-positives. Two whole cell enzyme-linked immunosorbent assay (ELISAs), two immunofluorescence assays and Western blotting were not useful as confirmatory tests. Sera from 330 blood donors and 72 cord sera were also screened for anti-p41 IgM. Five blood donor sera and five cord sera showed an IgM reactivity against p41. Based on our data we hypothesize that up to 1.5% of the population may have natural IgM antibodies against p41 in their sera. We observed that six out of nine sera with such antibodies could immobilize a B. afzelii reference strain in vitro. Whether anti-p41 IgM antibodies are capable of inactivating infective spirochetes and thereby prevent infection in vivo is, however, not yet clarified. The paradoxical conclusion that anti-p41 IgM antibodies may be a sign of resistance to infection rather than a sign of infection should be given consideration.