Clinical performance and analytical accuracy of a C6 peptide-based point-of-care lateral flow immunoassay in Lyme borreliosis serology.

We evaluated the analytical accuracy and the clinical performance of a ReaScan+ C6 LYME IgG point-of-care immunoassay (Reagena; index test). Analytical accuracy was evaluated in comparison to a C6 Lyme ELISA™ reference method (Oxford Immunotec) with retrospectively identified serum and CSF samples. The clinical performance was evaluated by using Lyme borreliosis patient and control subject serum and CSF samples. The study was conducted by following the 2015 Standards for Reporting of Diagnostic Accuracy Studies procedure. The sensitivity and specificity of the index test with serum samples were 83% and 91.6%, respectively, when C6 Lyme ELISA™ was used as a reference. The clinical sensitivity of the index test was 97.2%/96.8% for identifying Borrelia specific antibodies in definite/possible Lyme neuroborreliosis. With CSF samples, the clinical sensitivity was 97.2% for definite and 87.1% for possible Lyme neuroborreliosis. The clinical specificity of the assay was 96.1% with serum and 100% with CSF samples.

A Combination of N and S Antigens With IgA and IgG Measurement Strengthens the Accuracy of SARS-CoV-2 Serodiagnostics.

BACKGROUND: Primary diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is based on detection of virus RNA in nasopharyngeal swab samples. In addition, analysis of humoral immunity against SARS-CoV-2 has an important role in viral diagnostics and seroprevalence estimates. METHODS: We developed and optimized an enzyme immunoassays (EIA) using SARS-CoV-2 nucleoprotein (N), S1 and receptor binding domain (RBD) of the viral spike protein, and N proteins from SARS, Middle East respiratory syndrome (MERS), and 4 low-pathogenic human CoVs. Neutralizing antibody activity was compared with SARS-CoV-2 IgG, IgA, and IgM EIA results. RESULTS: The sensitivity of EIA for detecting immune response in COVID-19 patients (n = 101) was 77% in the acute phase and 100% in the convalescent phase of SARS-CoV-2 infection when N and RBD were used as antigens in IgG and IgA specific EIAs. SARS-CoV-2 infection significantly increased humoral immune responses against the 229E and NL63 N proteins. S1 and RBD-based EIA results had a strong correlation with microneutralization test results. CONCLUSIONS: The data indicate a combination of SARS-CoV-2 S1 or RBD and N proteins and analysis of IgG and IgA immunoglobulin classes in sera provide an excellent basis for specific and sensitive serological diagnostics of COVID-19.

C6 peptide enzyme immunoassay in Lyme borreliosis serology.

The cut-off values used in C6 peptide-based enzyme immunoassay (EIA), a widely used test in Lyme borreliosis (LB) serology, have not been thoroughly analysed. The objective of the study was to examine the performance of the C6 EIA, and to determine optimal cut-off values for the test. The analysed data contained results of 1368 serum samples. C6 EIA index values were compared statistically with the immunoblot (IB) test results. The identified cut-off values were further tested in a well-defined LB patient cohort. Cut-off value 1.6 appeared to be optimal when C6 EIA was used as a stand-alone test. When using C6 EIA as the first-tier test, the optimal cut-off values were 0.9 and 2.4 for negative and positive results. When C6 EIA was used as a second-tier test, samples yielding C6 index values ≥3.0 could be considered positive. The identified cut-off values had also a high sensitivity to identify seropositivity among definite LB patients. The identified cut-off values refine the role of C6 EIA in LB serology. Importantly, the use of C6 EIA leads to a reduction in the number of samples that need to be analysed using an IB, thus also reducing the costs. Two alternative workflows for LB serology including the C6 EIA are suggested.

Aetiology of febrile pharyngitis in children: Potential of myxovirus resistance protein A (MxA) as a biomarker of viral infection.

OBJECTIVES: Besides group A streptococcus (GAS), microbial causes of pharyngitis in children are not well known. We aimed to document the viral and bacterial aetiology of pharyngitis and to assess the pathogenic role of viruses by determining the myxovirus resistance protein A (MxA) in the blood as a marker of interferon response. METHODS: In this prospective observational study, throat swabs and blood samples were collected from children (age 1-16 years) presenting to the emergency department with febrile pharyngitis. Microbial cause was sought by bacterial culture, polymerase chain reaction, and serology. Blood MxA level was determined. RESULTS: A potential pathogen was detected in 88% of 83 patients: GAS alone in 10%, GAS and viruses in 13%, group C or G streptococci alone in 2% and together with viruses in 3%, and viruses alone in 59% of cases. Enteroviruses, rhinoviruses, and adenoviruses were the most frequently detected viruses. Blood MxA levels were higher in children with viral (880 [245-1250] µg/L; median [IQR]) or concomitant GAS-viral (340 [150-710] µg/L) than in those with sole GAS (105 [80-160] µg/L) infections. CONCLUSIONS: Detection of respiratory viruses simultaneously with elevated blood MxA levels supports the causative role of viruses in the majority of children with pharyngitis.

Array-in-well platform-based multiplex assay for the simultaneous detection of anti-HIV- and treponemal-antibodies, and Hepatitis B surface antigen.

Multiplex assays detecting sets of related clinical analytes simultaneously can save considerable amount of time and resources. Array-in-well (AIW) is a powerful platform for the multiplex detection of different analytes where microarrays can be printed at the bottom of microtiter wells, thus combining the potential of microarrays with the ease of handling microtiter wells. We have developed a single-step AIW assay for the simultaneous screening of HIV, Treponema pallidum subspecies pallidum (causing syphilis) and Hepatitis B virus infections targeting the specific detection of anti-HIV- and treponemal-antibodies and Hepatitis B surface antigen (HBsAg), respectively, using two different fluorescent label technologies i.e. DyLight 633 and europium nanoparticle. Double-antigen assay formats were used for anti-HIV- and treponemal-antibody detection that can simultaneously detect both IgG and IgM, and thus reduce the window period of detection. AIW assay was evaluated with well characterized serum/plasma samples (n=111), and the qualitative results were in near complete agreement with those of the reference assays. The AIW assay exhibited 100% sensitivities for all three analytes, and 100% specificities for anti-HIV antibodies and HBsAg, and 98.6% specificity for treponemal antibodies. The limit of detection of HBsAg in AIW assay was 0.18 ng/ml. This high performing AIW assay has the potential to be used as a multiplex screening test for these three infections.

TLR2 utilization of Borrelia does not induce p38- and IFN-beta autocrine loop-dependent expression of CD38, resulting in poor migration and weak IL-12 secretion of dendritic cells.

Lyme borreliosis is a tick-borne bacterial infection that in many cases is limited to the skin. However, in some patients the bacterium evades the immune response and disseminates into various organs. Dendritic cells (DCs) are among the first cells to meet invading pathogens in the skin. We have previously shown that CD38, an ectoenzyme involved in the migration of DCs and generally upregulated by microbial stimuli, is not upregulated in Borrelia garinii-stimulated DCs. In this paper, we characterize the cellular events that lead to the absence of CD38 on the DC surface after B. garinii stimulation and investigate the consequences of absent CD38 expression for the migration of DCs in vitro and in vivo. The data show that 1) effective signaling via p38 MAPK (and STAT1 and NF-kappaB) is needed for CD38 expression and 2) TLR2 stimulation, as opposed to TLR4 stimulation, does not induce IFN-beta autocrine loop-dependent expression of CD38 and secretion of IL-12. Further, we show that 3) B. garinii-stimulated DCs do not migrate effectively toward CCL19 and CCL21 and 4) after B. garinii infection of mice, the number of DCs migrating from the infection site to draining lymph nodes is only half that induced by Escherichia coli infection. Our results provide evidence for the first time that different TLR use results in different CD38 expression, which correlates with the migratory potential of DCs.

Disordered lymphoid purine metabolism contributes to the pathogenesis of persistent Borrelia garinii infection in mice.

Extracellular ATP and adenosine are important regulators of immune responses; however, contribution of purinergic signaling to host defense during persistent microbial infections remains obscure. Lyme borreliosis is a common arthropod-borne infection caused by Borrelia burgdorferi sensu lato. In this study, we investigated whether lymphoid purinergic signaling contributes to the mechanisms by which borreliae species evade the immune system and trigger joint inflammation. Intracutaneous inoculation of Borrelia garinii to C3H/He mice induced symptomatic infection manifested in elevated levels of borrelia-specific IgG Abs, persistent spirochete dissemination into the tissues and joint swelling, as well as approximately 2- to 2.5-fold enlargement of draining lymph nodes with hyperplasia of B cell follicle area and L-selectin shedding from activated T lymphocytes. Purine catabolism was also activated in lymph nodes but not spleen and blood of infected C3H/He mice within the first 4 postinfection weeks, particularly manifested in transient upregulations of adenosine triphosphatase/ectonucleoside triphosphate diphosphohydrolase and ecto-5'-nucleotidase/CD73 on CD4(+)CD8(+) T lymphocytes and adenosine deaminase activity on B220(+) B lymphocytes. Compared with borrelia-susceptible C3H/He strain, lymphocytes from C57BL/6 mice displayed markedly enhanced adenosine-generating capability due to approximately three times higher ratio of ecto-5'-nucleotidase to adenosine deaminase. Borrelia-infected C57BL/6 mice efficiently eradicated the inoculated spirochetes at more chronic stage without any signs of arthritis. Strikingly, deletion of key adenosine-generating enzyme, ecto-5'-nucleotidase/CD73, was accompanied by significantly enhanced joint swelling in borrelia-infected CD73-deficient C57BL/6 mice. Collectively, these data suggest that insufficient basal adenosine level and/or pathogen-induced disordered lymphoid purine homeostasis may serve as important prerequisite for promotion of inflammatory responses and further host's commitment to persistence of bacterial infection and arthritis development.

Leucine-rich repeats of bacterial surface proteins serve as common pattern recognition motifs of human scavenger receptor gp340.

Scavenger receptors are innate immune molecules recognizing and inducing the clearance of non-host as well as modified host molecules. To recognize a wide pattern of invading microbes, many scavenger receptors bind to common pathogen-associated molecular patterns, such as lipopolysaccharides and lipoteichoic acids. Similarly, the gp340/DMBT1 protein, a member of the human scavenger receptor cysteine-rich protein family, displays a wide ligand repertoire. The peptide motif VEVLXXXXW derived from its scavenger receptor cysteine-rich domains is involved in some of these interactions, but most of the recognition mechanisms are unknown. In this study, we used mass spectrometry sequencing, gene inactivation, and recombinant proteins to identify Streptococcus pyogenes protein Spy0843 as a recognition receptor of gp340. Antibodies against Spy0843 are shown to protect against S. pyogenes infection, but no function or host receptor have been identified for the protein. Spy0843 belongs to the leucine-rich repeat (Lrr) family of eukaryotic and prokaryotic proteins. Experiments with truncated forms of the recombinant proteins confirmed that the Lrr region is needed in the binding of Spy0843 to gp340. The same motif of two other Lrr proteins, LrrG from the Gram-positive S. agalactiae and BspA from the Gram-negative Tannerella forsythia, also mediated binding to gp340. Moreover, inhibition of Spy0843 binding occurred with peptides containing the VEVLXXXXW motif, but also peptides devoid of the XXXXW motif inhibited binding of Lrr proteins. These results thus suggest that the conserved Lrr motif in bacterial proteins serves as a novel pattern recognition motif for unique core peptides of human scavenger receptor gp340.

Anti-tumor necrosis factor-alpha treatment activates Borrelia burgdorferi spirochetes 4 weeks after ceftriaxone treatment in C3H/He mice.

BACKGROUND: The effect of anti-tumor necrosis factor (TNF)-alpha treatment in Borrelia burgdorferi-infected and ceftriaxone-treated C3H/He mice was evaluated. METHODS: Mice were infected with B. garinii A218 or B. burgdorferi sensu stricto N40. At 2 weeks of infection, one group was treated simultaneously with ceftriaxone and anti-TNF-alpha, whereas another received ceftriaxone at 2 weeks and anti-TNF-alpha 4 weeks later. One group received ceftriaxone treatment only. Infected and noninfected control groups were sham treated. RESULTS: At 14 weeks of infection, B. burgdorferi could not be detected by cultivation or by polymerase chain reaction in tissue samples of any mouse treated with ceftriaxone only. However, spirochetes grew from the tissue samples of one-third of the mice treated with anti-TNF-alpha simultaneously or 4 weeks after ceftriaxone. These activated spirochetes showed ceftriaxone sensitivity rates, plasmid profiles, and virulence rates similar to those of bacteria used to infect the mice. All infected control mice and mice given anti-TNF-alpha only were culture positive. CONCLUSIONS: This report shows that, after ceftriaxone treatment for 5 days, a portion of B. burgdorferi-infected mice still have live spirochetes in their body, which are activated by anti-TNF-alpha treatment.

Transcriptional response of human dendritic cells to Borrelia garinii--defective CD38 and CCR7 expression detected.

Lyme borreliosis is a disease, which can affect several organs and cause a variety of symptoms. In some patients, the infection may become chronic, even after antibiotic therapy, and cause persisting damage. Dendritic cells (DC) are involved in the initiation of innate and adaptive immune responses. To study interactions between Borrelia garinii (Bg), one of the causative agents of Lyme borreliosis, and human DC, we used a cDNA microarray to compare the Bg-induced DC transcriptional response with the response induced by LPS. The Bg-induced response consisted of a smaller number of genes than the LPS-induced response. The microarray showed that the ectoenzyme CD38, which has an important role in DC chemotaxis and migration to lymph nodes, was strongly up-regulated by LPS but practically not at all by Bg. This finding was confirmed with quantitative RT-PCR and with flow cytometry at the protein level. In addition, RT-PCR showed that CCR7 expression was 11-fold greater in LPS-stimulated than in Bg-stimulated cells. These findings suggest that Bg may affect crucial DC functions by blocking the up-regulation of important molecules in DC migration to lymph nodes, thus affecting further immune responses in Lyme borreliosis infection.

Use of flow cytometry for the adhesion analysis of Streptococcus pyogenes mutant strains to epithelial cells: investigation of the possible role of surface pullulanase and cysteine protease, and the transcriptional regulator Rgg.

BACKGROUND: Flow cytometry based adherence assay is a potentially powerful but little used method in the study of bacterial binding to host structures. We have previously characterized a glycoprotein-binding activity in Streptococcus pyogenes called 'strepadhesin' binding to thyroglobulin, submaxillar mucin, fetuin and asialofetuin. We have identified surface-associated pullulanase (PulA) and cysteine protease (SpeB) as carriers of strepadhesin activity. In the present paper, we investigated the use of flow cytometry as a method to study the binding of Rgg, SpeB and PulA knock-out strains to cultured human epithelial cells. RESULTS: Streptococcal mutants were readily labelled with CFDA-SE and their binding to epithelial cells could be effectively studied by flow cytometry. A strain deficient in Rgg expression showed increased binding to the analyzed epithelial cell lines of various origin. Inactivation of SpeB had no effect on the adhesion, while PulA knock-out strains displayed decreased binding to the cell lines. CONCLUSION: These results suggest that the flow cytometric assay is a valuable tool in the analysis of S. pyogenes adherence to host cells. It appears to be an efficient and sensitive tool for the characterization of interactions between the bacteria and the host at the molecular level. The results also suggest a role for Rgg regulated surface molecules, like PulA, in the adhesion of S. pyogenes to host cells.

Streptococcus pyogenes glycoprotein-binding strepadhesin activity is mediated by a surface-associated carbohydrate-degrading enzyme, pullulanase.

The interactions between pathogenic bacteria and the host need to be resolved at the molecular level in order to develop novel antiadhesive drugs and vaccines. We have previously identified strepadhesin, a novel glycoprotein-binding activity in Streptococcus pyogenes binding to thyroglobulin, submaxillar mucin, fetuin, and asialofetuin. The activity is known to be regulated by Mga, a regulator of streptococcal virulence factors, and is carried by the surface-associated streptococcal cysteine protease, SpeB. In the present study, we focused on the high strepadhesin activity in an S. pyogenes strain (NZ131rgg) lacking SpeB expression. By extracting surface proteins from the bacteria, a new strepadhesin protein was identified, and mass spectrometric analysis and database search identified it as a putative pullulanase. The gene was cloned, and the recombinant pullulanase (PulA) exhibited pullulanase and starch hydrolyzing activity, as well as strepadhesin activity. Sequencing of the pulA gene revealed an open reading frame with 3,498 bp encoding a protein of 1,165 amino acids with a predicted molecular mass of 129 kDa. PulA exhibited properties typical for a gram-positive surface protein with a putative signal sequence and LPKTGE cell wall anchoring motif and contained the four highly conserved regions common to pullulanases. Mutant bacteria deficient in PulA expression showed diminished strepadhesin activity on bacterial dot blot assay and reduced adherence to thyroglobulin immobilized on microtiter plates. Thus, S. pyogenes strepadhesin activity is carried by a surface-bound pullulanase, which combines glycoprotein-binding and carbohydrate-degrading activities in the same molecule.