Luminal Surface Plasma Treatment of Closed Cylindrical Microchannels: A Tool toward the Creation of On-Chip Vascular Endothelium

On-chip vascular microfluidic models provide a great tool to study aspects of cardiovascular diseases in vitro. To produce such models, polydimethylsiloxane (PDMS) has been the most widely used material. For biological applications, its hydrophobic surface has to be modified. The major approach has been plasma-based surface oxidation, which has been very challenging in the case of channels enclosed within a microfluidic chip. The preparation of the chip combined a 3D-printed mold with soft lithography and commonly available materials. We have introduced the high-frequency low-pressure air-plasma surface modification of seamless channels enclosed within a PDMS microfluidic chip. The plasma treatment modified the luminal surface more uniformly than in previous works. Such a setup enabled a higher degree of design freedom and a possibility of rapid prototyping. Further, plasma treatment in combination with collagen IV coating created a biomimetic surface for efficient adhesion of vascular endothelial cells as well as promoted long-term cell culture stability under flow. The cells within the channels were highly viable and showed physiological behavior, confirming the benefit of the presented surface modification.

Cognitive changes after methanol exposure: Longitudinal perspective

BACKGROUND

From 2012 to 2013, there was a mass methanol poisoning outbreak in the Czech Republic. Methanol metabolites can cause specific lesions in the basal ganglia, subcortical white matter, and optic nerve. However, long-term sequelae of methanol poisoning on cognitive functioning have not yet been explored. The current study aimed to delineate the cognitive changes observed in methanol poisoning survivors in the seven years since 2012.

METHODS

We conducted longitudinal research with repeated measurements in 2013, 2015, 2017 and 2019 to evaluate the development of cognitive changes after acute methanol poisoning. A complex neuropsychological battery consisted of tests of global cognitive performance, auditory and visual attention, executive functioning, learning and memory, working memory and language. Motor performance measures and depression scale were also included.

RESULTS

Repeated measures ANOVA of four measurements with post-hoc tests showed a significant decline in the Mini-Mental State Examination (p = 0.007); however, other parameters were not significantly decreasing. In comparison to normative values, the z-scores for each test measure, in the memory domain, in particular, ranged from 43 to 60 % of participants below 1.5 SD. Mild to severe depression levels from the onset of poisoning improved during the seven years, returning to normal in up to 27 % of participants.

CONCLUSION

In the longitudinal perspective, methanol poisoning survivors manifest progressive global cognitive decline and overall persistent below-average cognitive performance with some improvements in the frequency of depressive symptoms.

3D visual cueing shortens the double support phase of the gait cycle in patients with advanced Parkinson's disease treated with DBS of the STN

Background

Gait disturbances have emerged as some of the main therapeutic concerns in late-stage Parkinson’s disease (PD) treated with dopaminergic therapy and deep brain stimulation (DBS). External cues may help to overcome freezing of gait (FOG) and improve some of the gait parameters.

Aim

To evaluate the effect of 3D visual cues and STN-DBS on gait in PD group.

Methods

We enrolled 35 PD patients treated with DBS of nucleus subthalamicus (STN-DBS). Twenty-five patients (5 females; mean age 58.9 ±6.3) and 25 sex- and age-matched controls completed the gait examination. The gait in 10 patients deteriorated in OFF state. The severity of PD was evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn and Yahr (HY). The PD group filled the Falls Efficacy Scale-International (FES) and Freezing of Gait Questionnaire (FOGQ). Gait was examined using the GaitRite Analysis System, placed in the middle of the 10m marked path. The PD group was tested without dopaminergic medication with and without visual cueing together with the DBS switched ON and OFF. The setting of DBS was double-blind and performed in random order.

Results

The UPDRS was 21.9 ±9.5 in DBS ON state and 41.3 ±13.7 in DBS OFF state. HY was 2.5 ±0.6, FES 12.4 ±4.1 and FOGQ 9.4 ±5.7. In the DBS OFF state, PD group walked more slowly with shorter steps, had greater step length variability and longer duration of the double support phase compared to healthy controls. The walking speed and step length increased in the DBS ON state. The double support phase was reduced with 3D visual cueing and DBS; the combination of both cueing and DBS was even more effective.

Conclusion

Cueing with 3D visual stimuli shortens the double support phase in PD patients treated with DBS-STN. The DBS is more effective in prolonging step length and increasing gait speed. We conclude that 3D visual cueing can improve walking in patients with DBS.

Agreement between the GAITRite® System and the Wearable Sensor BTS G-Walk® for measurement of gait parameters in healthy adults and Parkinson's disease patients

Background

Nowadays, the most widely used types of wearable sensors in gait analysis are inertial sensors. The aim of the study was to assess the agreement between two different systems for measuring gait parameters (inertial sensor vs. electronic walkway) on healthy control subjects (HC) and patients with Parkinson's disease (PD).

Methods

Forty healthy volunteers (26 men, 14 women, mean age 58.7 ± 7.7 years) participated in the study and 24 PD patients (19 men, five women, mean age 62.7 ± 9.8 years). Each participant walked across an electronic walkway, GAITRite, with embedded pressure sensors at their preferred walking speed. Concurrently a G-Walk sensor was attached with a semi-elastic belt to the L5 spinal segment of the subject. Walking speed, cadence, stride duration, stride length, stance, swing, single support and double support phase values were compared between both systems.

Results

The Passing-Bablock regression slope line manifested the values closest to 1.00 for cadence and stride duration (0.99 ≤ 1.00) in both groups. The slope of other parameters varied between 0.26 (double support duration in PD) and 1.74 (duration of single support for HC). The mean square error confirmed the best fit of the regression line for speed, stride duration and stride length. The y-intercepts showed higher systematic error in PD than HC for speed, stance, swing, and single support phases.

Conclusions

The final results of this study indicate that the G-Walk system can be used for evaluating the gait characteristics of the healthy subjects as well as the PD patients. However, the duration of the gait cycle phases should be used with caution due to the presence of a systematic error.

Pavement patterns can be designed to improve gait in Parkinson's disease patients

BACKGROUND

Public spaces are usually designed with respect to various patient populations, but not Parkinson's disease. The objective of this study was to explore what type of easily applicable visual cueing might be used in public spaces and some interiors to improve gait in people with Parkinson's disease.

METHODS

Thirty-two patients with freezing of gait walked an 8-meter track on 6 different floor patterns in single- and dual-task conditions in random sequence. The reference pattern was a virtual large transverse chessboard, and the other patterns differed either in size (small floor stones), orientation (diagonal), nature (real paving), regularity (irregular), or no pattern. Time, number of steps, velocity, step length, cadence, and dual-task effect were calculated. The number and total duration of freezing episodes were analyzed.

RESULTS

Virtual, large, transverse floor stones improve time (P = 0.0101), velocity (P = 0.0029), number of steps (P = 0.0291), and step length (P = 0.0254) in Parkinson's disease patients compared with walking on no pattern. Virtual floor stones were superior in time and velocity to the real ones. Transverse floor stones were better than diagonal, whereas regular pattern stones were superior to irregular in some gait parameters. Subjectively, the reference pattern was preferred to the irregular one and to no pattern. No direct effect on freezing of gait was observed.

CONCLUSIONS

Parkinson's disease patients may benefit from floor patterns incorporating transverse oriented large rectangular visual cues. Because public space can be regulated with respect to people with medical conditions, the relevant legislative documents should be extended to allow for parkinsonian gait disorder. © 2019 International Parkinson and Movement Disorder Society.

A unique de novo gain-of-function variant in CAMK4 associated with intellectual disability and hyperkinetic movement disorder

Calcium/calmodulin-dependent protein kinases (CaMKs) are key mediators of calcium signaling and underpin neuronal health. Although widely studied, the contribution of CaMKs to Mendelian disease is rather enigmatic. Here, we describe an unusual neurodevelopmental phenotype, characterized by milestone delay, intellectual disability, autism, ataxia, and mixed hyperkinetic movement disorder including severe generalized dystonia, in a proband who remained etiologically undiagnosed despite exhaustive testing. We performed trio whole-exome sequencing to identify a de novo essential splice-site variant (c.981+1G>A) in CAMK4, encoding CaMKIV. Through in silico evaluation and cDNA analyses, we demonstrated that c.981+1G>A alters CAMK4 pre-mRNA processing and results in a stable mRNA transcript containing a 77-nt out-of-frame deletion and a premature termination codon within the last exon. The expected protein, p.Lys303Serfs*28, exhibits selective loss of the carboxy-terminal regulatory domain of CaMKIV and bears striking structural resemblance to previously reported synthetic mutants that confer constitutive CaMKIV activity. Biochemical studies in proband-derived cells confirmed an activating effect of c.981+1G>A and indicated that variant-induced excessive CaMKIV signaling is sensitive to pharmacological manipulation. Additionally, we found that variants predicted to cause selective depletion of CaMKIV's regulatory domain are unobserved in diverse catalogs of human variation, thus revealing that c.981+1G>A is a unique molecular event. We propose that our proband's phenotype is explainable by a dominant CAMK4 splice-disrupting mutation that acts through a gain-of-function mechanism. Our findings highlight the importance of CAMK4 in human neurodevelopment, provide a foundation for future clinical research of CAMK4, and suggest the CaMKIV signaling pathway as a potential drug target in neurological disease.

Thermostable trypsin conjugates immobilized to biogenic magnetite show a high operational stability and remarkable reusability for protein digestion

In this work, magnetosomes produced by microorganisms were chosen as a suitable magnetic carrier for covalent immobilization of thermostable trypsin conjugates with an expected applicability for efficient and rapid digestion of proteins at elevated temperatures. First, a biogenic magnetite was isolated from Magnetospirillum gryphiswaldense and its free surface was coated with the natural polysaccharide chitosan containing free amino and hydroxy groups. Prior to covalent immobilization, bovine trypsin was modified by conjugating with α-, β- and γ-cyclodextrin. Modified trypsin was bound to the magnetic carriers via amino groups using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysulfosuccinimide as coupling reagents. The magnetic biomaterial was characterized by magnetometric analysis and electron microscopy. With regard to their biochemical properties, the immobilized trypsin conjugates showed an increased resistance to elevated temperatures, eliminated autolysis, had an unchanged pH optimum and a significant storage stability and reusability. Considering these parameters, the presented enzymatic system exhibits properties that are superior to those of trypsin forms obtained by other frequently used approaches. The proteolytic performance was demonstrated during in-solution digestion of model proteins (horseradish peroxidase, bovine serum albumin and hen egg white lysozyme) followed by mass spectrometry. It is shown that both magnetic immobilization and chemical modification enhance the characteristics of trypsin making it a promising tool for protein digestion.

N-terminal region of the PB1-F2 protein is responsible for increased expression of influenza A viral protein PB1

Influenza A virus (IAV) PB1-F2 protein is encoded by an alternative reading frame (+1) within the PB1 gene. PB1-F2 has been shown to contribute to the pathogenesis of influenza virus infection as well as to the secondary bacterial infection. More recently has been shown that PB1-F2 protein may regulate a viral RNA (vRNA) polymerase activity by the interaction with PB1 protein. We proved that PB1-F2 protein increased the level of expression of PB1 protein and vRNA in the infected cells. Moreover, we demonstrated that a higher level of vRNA expression resulted in the increase of expression of multiple viral proteins, including NP, M1, and NS1. Finally, we used plasmids expressing N-terminal (1-50 aa) or C-terminal (51-87 aa) region of the PB1-F2 molecule for transfection of MDCK cells co-infected with influenza A/Puerto Rico/8/34 (H1N1) virus deficient in the PB1-F2 protein expression (PR8ΔPB1-F2). These experiments clearly showed that N-terminal region of PB1-F2 protein was responsible for the increase in PB1 protein expression. C-terminal region of PB1-F2 protein had no effect. Thus, we have identified the important function for N-terminal region of PB1-F2 protein.

Effect of proteasome inhibitors on expression of HLA-G isoforms

HLA-G primary transcript is alternatively spliced into a number of mRNAs. In addition to full length HLA-G1 protein isoform these mRNAs might also encode truncated HLA-G protein isoforms lacking one or two extracellular domains. Whereas HLA-G1 protein isoform is regularly identified, truncated HLAG protein isoforms are not detected even if all alternative spliced mRNAs are present in cells. The absence of entire domain(s) renders the truncated HLA-G protein isoforms incapable of binding peptide and beta2-microglobulin. These features of truncated HLA-G protein isoforms may result in their rapid degradation by proteasomes. Here we show that despite the presence of all alternatively spliced HLA-G transcripts in JEG-3 cells pretreated with proteasome inhibitors only a full length HLA-G1 protein isoform was regularly detected. Interestingly, immunoblot analysis showed slight increase of HLA-G1 protein in cells pretreated with proteasome inhibitors, although the expression of HLA-G1 transcript was basically not affected. Expression of HLA-G3 transcript increased in JEG-3 cells pre-incubated with LLL, however, neither HLA-G3 nor other HLA-G short protein isoform was regularly detected. In K562 transfectants proteasome inhibitor LLL greatly enhanced expression of the HLA-G1 and -G2 transcripts as well as corresponding protein isoforms. Flow cytometry analysis showed that in cells pre-treated with proteasome inhibitors cell surface expression of HLA-G1 protein decreased but the quantity of intracellularly localized HLA-G antigens increased. Altogether our results suggest that truncated HLA-G proteins isoforms are not detected in JEG-3 cells as a result of their instability and the low translation efficiency of truncated HLA-G transcripts.

Binding analysis of HLA-G specific antibodies to hematopoietic cells isolated from leukemia patients

Expression of HLA-G on the surface of malignant hematopoietic cells isolated from leukemia patients was analyzed by flow cytometry using monoclonal antibodies (mAbs) recognizing both, intact HLA-G complex (87G, 01G and MEM-G9) as well as HLA-G free heavy chain (4H84, MEM-G/1 and MEM-G/2). Prerequisite of HLA-G detection by mAbs specific to free heavy chain was mild acid treatment, which dissociates intact HLA-G complex. All mAbs, with the exception of 4H84 mAb, did not indicate the presence of HLA-G antigen in leukemia cells. Positive staining with 4H84 mAb was detected in acid-treated cells isolated from 16 out of 30 patients. Intensity of staining increased after IFN-g pre-incubation in most cases. Immunoblot analyses and RT-PCR, however, failed to detect HLA-G antigen or HLA-G transcripts in cells that bind 4H84 mAb after acid-treatment. The binding of 4H84 mAb can be explained by the acid-induced cross-reactivity of this HLA-G specific mAb with classical HLA class I molecules [15]. The results described here further demonstrate that the HLA-G molecule is not expressed in freshly isolated human leukemia cells.

Analysis of the extracellular processing of HIV-1 gp160-derived peptides using monoclonal antibodies specific to H-2Dd molecule complexed with p18-I10 peptide

The immunodominant peptide of human immunodeficiency virus 1 gp 160 for murine cytotoxic T cells of H-2d haplotype, has been originally identified as a 15 amino acid residue peptide P18IIIB (RIQRGPGRAFVTIGK) (Takahashi et al., 1988). Further studies have indicated that a more active form of the peptide is generated by removal of the C-terminal dipeptide by angiotensin-I-converting enzyme (ACE), and additional detailed studies have shown that the actual immunodominant peptide is a decamer P18-I10 (RGPGRAFVTI) (Kozlowski et al., 1993). The effect of proteolytic processing on the antigenicity of P18IIIB peptide and its analogs was investigated by functional T cell assays based on the ability of T cell receptor (TCR) to recognize a specific major histocompatibility complex class I (MHC-I)/peptide complex. Recently we described a new monoclonal antibody (MAb) KP15 directed against the MHC-I molecule H-2Dd complexed with the 10-mer peptide P18-I10. Using this MAb, the cell surface H-2Dd/P18-I10 complex can be easily detected by flow cytometry (Polakova et al., 2000). Here we examined whether peptides longer than P18-I10 decamer form H-2Dd complexes recognized by KP15 MAb. Further we also analyzed how the ACE processing of P18IIIB-related peptides of different length affects their ability to form complexes with H-2Dd recognized by MAb KP15. These experiments confirmed that the ACE digestion of 15-mer peptide P18IIIB is the most effective in the production of a peptide capable of forming complex with H-2Dd recognized by KP15 MAb. The ACE digestion of longer peptides (16-mer to 19-mer) did not produce a significant quantity of peptides, capable of forming H-2Dd complexes recognizable with by MAb KP15. Peptides shorter than P18IIIB (13-mer to 10-mer), notably the optimally sized P18-I10 peptide lost most of their capacity to form H-2Dd complexes recognized by KP15 MAb. Our results show that the extracellular processing of MHC-I-restricted peptides, which cannot be overlooked in designing peptide-based vaccines, can be also studied by as simple and rapid assay as flow cytometry, provided MAbs specific to a particular MHC-I/peptide complex are available.

Expression of the non-classical HLA-G antigen in tumor cell lines is extremely restricted

It has been proposed that tumor cells frequently associated with partial or total loss of HLA class Ia expression may abnormally express HLA-G class Ib antigen. Such peculiar HLA class I expression would allow tumor cells to escape not only from CD8+T but also from NK-cell cytotoxicity. We studied the cell surface expression of HLA-G using flow cytometry with two HLA-G specific monoclonal antibodies (87G, 01G). The JEG-3 choriocarcinoma cell line, which constitutively expresses HLA-G antigens was used as a positive control. We did not detect the cell-surface HLA-G antigens in the following 75 tumor cell lines: melanoma (22), neuroblastoma (7), retinoblastoma (1), glioma (2), breast carcinoma (3), ovarian carcinoma (3), cervical carcinoma (1), colon carcinoma (3), bladder carcinoma (2), hepatocarcinoma (1), sarcoma (2) and leukemia cell lines: T-lymphocytes (6), B-lymphocytes (13) and myelo-monocytes (9). We found that some myelomonocytic cell lines express on their surface high affinity FcgammaRI (CD64) that may result in the binding of HLA-G specific mabs to their cell surface even in the absence of HLA-G molecules. Our panel of HLA-G negative tumor cell lines accommodated 62 cell lines for which similar analysis have not been reported and also contained 13 cell lines with total or partial loss of HLA class Ia molecules. Our observation imply that under normal culture conditions the cell surface HLA-G reactive with 87G and 01G mabs is absent in most tumor cell lines of different origin.

[Atypically localized scrofuloderma]

Tuberculosis of the skin and peripheral subcutaneous lymphnodes represents the most frequent forms of extrapulmonary tuberculosis. The group of patients subjected to our observation had the highest incidence of tuberculous lymphadenitis. The second most frequent disease observed was scrofuloderma. Its profound colliquative form, the so-called tuberculosis subcutanea fistulosa profunda is extremely scarce. Our work describes one case of such a disease. The pathological process in our patient was localized in the perianal and perigenital region. Especially this localization is typical for other non-specific dermal diseases. The work stresses the tuberculous ethiology of the pathological process in this region from the differential diagnostic point of view. The fact that this disease has not been appropriately treated due to the lack of precedent cases during the past years, has caused long lasting physical and psychical suffering of the patient. (Tab. 1, Fig. 1, Ref. 5.)

[Tuberculous lymphadenitis--the most frequent symptom of extra-pulmonary tuberculosis]

The work reports about the recently detected forms of tbc of skin and peripheral lymphnodes, which were confirmed in patients of the Dermatology Department of UTaRCH, Bratislava, Podunajské Biskupice in the period 1981-1989. From the total of 221 newly detected diseases the lymphadenitis or tbc cutis colliquativa occurred in 171 patients (77.4%). The lymphadenitis was confirmed in 140 patients (63.4%). Lymphadenitis, or scrofuloderma (tbc cutis colliquativa) most frequently inflicted the cervical subcutaneous lymphnodes--in 140 patients (81.9%). Unilateral infliction of lymphnodes prevailed. Incidence of these diseases was significantly higher in women (76%) than in men (24%). Within the process of differential diagnostics, in cases with inflicted peripheral subcutaneous lymphnodes it is necessary to take into consideration the possibility of their tuberculous etiology. (Fig. 1, Tab. 3, Ref. 7.).

[Use of monoclonal antibodies against human HLA II antigens for the detection of bovine B lymphocytes and macrophages]

The crossreactivity of mouse monoclonal antibodies (MoAbs) (Tab. I) prepared against human HLA-DR and HLA-DP antigens was studied in various bovine cells: lymphocytes from lymph nodes and peripheral blood, adherent (B) and nonadherent (T) lymphocytes, monocytes, granulocytes and platelets. In the immunofluorescence test, MoAbs Bra13, Bra14, Bra20, Bra22, Bra30, Bra70, HL-38 reacted with bovine B lymphocytes and monocytes, but not with other tested cells (Tab. III, IV). These antibodies, except Bra22, were positive with B lymphocytes in the complement dependent cytotoxic test (Tab. II). The similarity of the bovine antigens and HLA-DR antigens determined by used MoAbs was also proved by immunoblotting. Monoclonal antibodies Bra38 and BraFB6 did not react with the bovine cells and separated antigens. The epitope (HLA-DR) recognized by the antibody Bra38 is probably absent in cattle. The presence of HLA-DP analogue determined by the antibody BraFB6 has not been confirmed. The crossreactive MoAbs could be used for the detection of B lymphocytes and macrophages in veterinary immunology.

Type-common and type-specific monoclonal antibodies to herpes simplex virus types 1 and 2

Seventeen monoclonal antibodies (Mabs) reacting specifically with the cells infected with herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) were characterized by a variety of immunological tests such as radioimmunoprecipitation, immunoblotting and virus-neutralization. The majority of Mabs was directed against glycoprotein B (anti-gB), six reacted with glycoprotein C (anti-gC) and one with glycoprotein G (anti-gG). Six anti-gB Mabs reacted with both types of HSV (anti-gB-1,2), two anti-gB and all the six anti-gC Mabs have been specific for HSV-1 (anti-gB-1 and anti-gC-1). The remaining two anti-gB Mabs and the anti-gG have been specific to HSV-2 (anti-gB-2 and anti-gG). Only three out of the seventeen examined Mabs neutralized the virus.

Rimantadine effects on the elasticity of bilayer lipid membranes and on ion transport through gramicidin D channels

The effect of the antiviral preparation rimantadine on lipid bilayer membranes (BLM) was studied by measuring the modulus of elasticity in the direction normal to the surface (E perpendicular) and by estimating the conductance lambda, the lifetime tau of single gramicidin D channels (GRD), and the coefficient of nonlinearity beta of current voltage characteristics (IVC) of GRD-modified BLM. Rimantadine induced a nonmonotonic change in E perpendicular of BLM prepared from a mixture of egg lecithin with cholesterol: at relatively low rimantadine concentrations (0-40 micrograms/ml) E perpendicular first increased, reached a maximum and started to decrease. The effectivity of rimantadine was dependent on the cholesterol concentration in the BLM. Changes in E perpendicular suggest an increased ordering of the lipid bilayer at low rimantadine concentrations and formation of clusters of the preparation at concentrations exceeding those necessary to obtain maximal values of E perpendicular for the given BLM lipid composition. Rimantadine concentrations lifetime by approximately 20 percent, affected the degree of IVC nonlinearity and superlinearity of GRD-modified membranes, which suggests some effect on the height of the barrier at the ionic channel mouth and in its centre.

Monoclonal antibodies to glycopolypeptides HA1 and HA2 of influenza virus haemagglutinin

Anti-haemagglutinin monoclonal antibodies were prepared and their HA1 or HA2 specificity was determined by solid phase radioimmunoassay (RIA) using purified viral haemagglutinin (HA) and haemagglutinin glycopolypeptides HA1 and HA2, by radioimmunoprecipitation followed with SDS-PAGE, by immunoblotting and by inhibition of virus-induced haemagglutination. The capacity of these methods to estimate HA1 or HA2 specificity of anti-HA monoclonal antibodies (MoAb) was compared. HA1 specificity was demonstrated for all hybridomas originating from lymphocytes of mice immunized with complete influenza virus, except IIF4 hybridoma which was HA2-specific. All hybridomas obtained with lymphocytes from mice immunized with HA glycopolypeptide HA2 were HA2-specific. Anti-HA2 MoAb neither inhibit haemagglutination induced by the virus or by HA subunits nor neutralized viral infectivity, either alone or in mixture. As expected, all anti-HA1 MoAb were H3 subtype-specific, showing usually good reactivity only with viruses close to the virus strain used for immunization. Two anti-HA1 MoAb (IVA1 and IVG6) showed unusual cross-reactivity within the H3 subtype. All anti-HA2 MoAb were broadly cross-reactive within the H3 subtype. Moreover, a half of them showed high cross-reactivity with influenza viruses of the H7 HA subtype. But the same antibodies did not react with HA of H1, H2 and H8 subtypes.

Indication and study of antigenic properties of influenza virus internal proteins by means of monoclonal antibodies

Influenza A and B viruses isolated from animals and man were studied by solid phase radioimmunoassay (SP RIA) using monoclonal antibodies to the A/Dunedin/4/73 strain nucleoprotein (NP). Only influenza A viruses isolated before 1980 interacted with the monoclonal antibody set used, while strains isolated between 1980 and 1983 failed to do so. It was shown that RIA employing monoclonal antibodies was useful for rapid identification of influenza virus NP in the allantoic fluid containing fresh influenza A virus isolates.

Monoclonal antibody against an antigen selectively assembled into vesicular stomatitis virus virions from HeLa cells

A mouse hybridoma cell line IIB9, secreting IgG2b antibody specific for a HeLa cell antigen, was obtained by fusion of a mouse myeloma cell line with spleen cells from mice immunized with purified VSV tsO45 mutant (defective in assembly of G protein) which had been reproduced at a non-permissive temperature in HeLa cells. The monoclonal antibody IIB9 was strictly specific for HeLa cells in two tests: (1) reaction with VSV or Chandipura virus phenotypically mixed with host cell antigen, (2) complement-dependent cytotoxicity test (51Cr-release).

Human cell surface proteins selectively assembled into vesicular stomatitis virus virions

Vesicular stomatitis virus (VSV) selectively assembled proteins from human cells into progeny virions. These proteins can be surface labeled before infection with 125I, and when purified virus was examined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, only two or three bands of proteins (Mr around 100K) were seen. Antisera to these proteins were produced, using as immunizing antigen VSV tsO45 mutant, defective in assembly of G protein, which had been made at the nonpermissive temperature in the three human tumor cell lines, HeLa (cervical carcinoma), T47D (breast carcinoma), and HMB2 (melanoma). After absorption with wild-type VSV, each of the antisera displayed a different pattern of reactivity; at least three antigenic specificities were detected. Two of them, corresponding to antigens selected by VSV from HeLa and T47D, were to some extent related and they showed an association mainly with epithelial cell-derived gynecological tumors, but they were absent in carcinomas of lung or of digestive tract. These (or related) antigens were expressed in a lower level in some normal tissues, mainly in ovaries. Antigen(s) assembled by VSV from the melanoma cell line was entirely different and appeared to be associated with cell growth. The grounds for selective assembly of these specific proteins by VSV are not clear; they either share with viral surface glycoproteins some physical or structural properties, which are critical for incorporation into the viral envelope, or conceivably they even may represent uncleaved precursor proteins coded by env genes of incomplete genomes of endogenous human retroviruses.

Assembly of xenotropic murine leukaemia virus-related antigens from the surface of mouse L cells by vesicular stomatitis virus

Two xenotropic murine leukaemia virus (XMuLV)-related proteins--a major envelope glycoprotein gp70 and a 90K protein (probably corresponding to the uncleaved envelope precursor)--were expressed on the surface of mouse L cells as demonstrated by lactoperoxidase-catalysed iodination and immunoprecipitation with anti-XMuLV serum. These two proteins out of many labelled cell surface proteins were selectively incorporated into vesicular stomatitis virus (VSV) virions. Significant differences were found in the amounts of labelled XMuLV-related proteins between L cells and two cell lines infected with XMuLV (rabbit SIRC and lamb LKC cells). The two viral antigens represented only a small proportion of radioactivity on L cells. While in XMuLV-infected SIRC and LKC cells, the gp70 was the major labelled surface protein no detectable amounts of XMuLV-related 90K protein or of cell-specific proteins were found in these cells.

Radioimmunoassay of influenza A virus haemagglutinin. II. Antigenic cross-reactions of influenza A (H3 subtype) viruses as determined by radioimmunoassay and haemagglutination inhibition tests

Individual rabbits differed greatly in their antibody response to the "strain-specific" and "cross-reactive" antigenic determinants on the haemagglutinin (HA) subunit of influenza virus recombinant MRC11 (H3N2) and influenza virus Dunedin (H3N2), after immunization with whole virus or bromelain-released haemagglutinin (B-HA). Consequently, diverse cross-reactions between htese viruses and A/Hong Kong/68 virus were found in the haemagglutination inhibition (HI) test as well as in homologous radioimmunoassay (125I-B-HA from MRC11:anti MRC11 serum, and 125I-B-HA from Dunedin: anti Dunedin serum) when sera from different animals were employed. Radioimmunoassay (RIA), over and above to the HI test, was able to differentiate clearly the respective HAs also with antisera reacting to the same HI titre with both corresponding influenza virus strains. Thus it appeared that antigenic differences could be identified with higher sensitivity by homologous RIA than by the HI test and that multiple antigenic determinants were reactive on the 125I-B-HA in the RIA procedure employed. MRC11 and A/HK/68 viruses were also compared by heterologous RIA (125I-B-HA from MRC11: anti A/HK/68 serum). It was found that preferentially antigenic determinants with a high degree of cross-reactivity could be studied in the heterologous system.

Use of Staphylococcus aureus for rapid radioimmunoassay of influenza A virus haemagglutinin

In a rapid method for the radioimmunoassay (RIA) of influenza A virus haemagglutinin, Staphylococcus aureus (strain Cowan I, Czechoslovak State Collection No Mau 55/64) was used for separation of bound and free antigens. With rabbit and human immune sera, the binding of antigen-antibody complexes to heat-killed, formalin-fixed staphylocci was comparable to the double antibody technique. The time required for the completion of binding reaction was about 10 min compared to 18--24 hr required for double antibody precipitation. S. aureus did not bind directly (i.e. in the absence of specific antibody) a significant amount of radiolabelled antigen.

Antigenic glycopolypeptides HA1 and HA2 of influenza virus haemagglutinin. III. Reactivity with human convalescent sera

The immune reactivity to both haemagglutinin glycopolypeptides HA1 and HA2 [prepared from bromelain-released haemagglutinin of influenza virus A/Dunedin/4/73 (H3N2)], was demonstrated by both gel double immundiffusion and radioimmunoassay in human convalescent sera obtained after natural infection during influenza epidemics in 1974/75 and 1976/77. In gel double immunodiffusion, the precipitin line(s) corresponding to glycopolypeptide HA1 were always more distinct than precipin line(s) corresponding to glycopolypeptide HA2. In radioimmunoassay, human convalescent sera revealed higher titres for binding of 125-I-labelled HA2 than for 125-I-labelled HA1. Characterization of human convalescent sera was completed by haemagglutination-inhibition test.

Antigenic glycopolypeptides HA1 and HA2 of influenza virus haemagglutinin. IV. Immunogenic properties of separated haemagglutinin glycopolypeptides

Highly purified haemagglutinin glycopolypeptides HA1 and HA2 were effective in eliciting an antibody response. HA2 had a markedly greater immunogenic potential than HA1. In gel double immunodiffusion, sera from rabbits immunized with HA2 produced more distinct precipitin lines than sera obtained by immunization with HA1. Both kinds of rabbit sera gave precipitation with homologous antigen and with bromelain-released and purified haemagglutinin (B-HA). In radioimmunoassay, sera from rabbits immunized with HA2 revealed considerable titres for 125I-labelled HA2 binding and reacted preferentially with 125I-labelled HA2. In general, sera from rabbits immunized with HA1 exhibited low titres for 125I-labelled HA1 binding: usually they reacted also with 125I-labelled B-HA and 125I-labelled HA2. Only rabbits injected with a few doses of HA1 at short intervals revealed preferential binding for 125I-labelled HA1. Glycopolypeptides HA1 and HA2 failed to induce haemagglutination-inhibiting and virus neutralizing antibodies in rabbits.

Antigenic glycopolypeptides HA1 and HA2 of influenza virus haemagglutinin. II. Reactivity with rabbit sera against intact virus and purified undissociated haemagglutinin

Rabbit sera produced against either intact virus or purified undissociated haemagglutinin were examined for reactivity with highly purified haemagglutinin glycopolypeptides. Sensitive radioimmunoassay for 125I-labelled glycopolypeptides revealed antibody reactive with either glycopolypeptide HA1, or glycopolypeptide HA2. Antibodies against the carbohydrate moiety were responsible only for a part of the binding activity. Under the conditions employed, the binding activity for glycopolypeptide HA2 was much stronger than for glycopolypeptide HA1. Competition assays suggested that immune reactivities were due to distinct antibody populations (i.e. with a specifity for glycopolypeptide HA1 and glycopolypeptide HA2, respectively). The immune reactivity to both haemagglutinin constituents, glycopolypeptides HA1 and HA2, was also shown by gel double diffusion. The precipitin line(s) corresponding to glycopolypeptide HA1 was (were) usually more distinct than precipitin line(s) corresponding to glycopolypeptide HA2. The glycopolypeptides HA1 and HA2 showed the reaction of nonidentity in immunodiffusion analysis.

Antigenic glycopolypeptides HA1 and HA2 of influenza virus haemagglutinin. I. Gel filtration in 6 M guanidine hydrochloride

Highly purified glycopolypeptides HA1 and HA2 were separated from bromelain-released haemagglutinin of influenza virus A/Dunedin/4/73 (H3N2) by gel filtration in 6 M guanidine hydrochloride under reducing conditions. The purity of both glycopolypeptides was proved by extensive studies. Despite the lack of C-terminal end, the isolated HA2 glycopolypeptide displayed some hydrophobic properties.

Radioimmunoassay of influenza A virus haemagglutinin. I. Preparation and properties of radioactive 125I-labelled bromelain-released haemagglutinin

Haemagglutinin released from influenza A virus recombinant MRC11 [antigenically identical to the strain A/Port Chalmers/1/73 (H3N2)] by bromelain treatment and purified by rate zonal centrifugation (further on B-HA) was examined for eventual contamination by neuraminidase. According to specific enzymatic activities corresponding to MRC11 virus and B-HA alone respectively, B-HA contained less than 0.1% of enzymatically active neuraminidase orginally present in the virus. Gel double diffusion tests, specifities of rabbit antisera induced by B-HA, as well as radioimmunoprecipitation experiments demonstrated that B-HA was devoid of any antigenically active neuraminidase. Precipitation of 125I-labelled B-HA with antisera to influenza virus recombinants with N2 neuraminidase has been evidently caused by antibodies to host antigenic determinaant(s) present in these sera. With respect to purity as well as radioimmunoprecipitation properties, B-HA is quite suitable for radioimmunoassay experiments.

A competitive-inhibition radioimmunoassay for influenza virus envelope antigens

A double-antibody competitive-inhibition radioimmunoassay for influenza virus envelope antigens is described. A viral antigen preparation from influenza A virus recombinant MRC11 [antigenically identical to A/Port Chalmers/1/73 (H3N2)] consisting of haemagglutinin and neuraminidase was labelled with radioiodine. Rabbit antisera were allowed to react with the labelled antigen and the resultant antigen-antibody complexes were precipitated with the appropriate antiglobulin. The competitive-inhibition radioimmunoassay was very sensitive in elucidation of differences even among closely related influenza virus strains. Attempts have been made to eliminate neuraminidase from radioimmunoprecipitation in order to obtain a competitive-inhibition radioimmunoassay system for haemagglutinin alone.

Use of cross-linking in studying the structure of RNA tumour viruses

Treatment of intact avian myeloblastosis virus (AMV) with dimethyl suberimidate dihydrochloride (DMS), a cross-linking agent specific for amino groups, was found to result in progressive cross-linking among viral proteins, as revealed by polyacrylamide gel electrophoresis (PAGE) in the presence of sodium dodecyl sulphate (SDS). Free viral proteins were not cross-linked. The cross-linked protein complex with an apparent molecular weight of 50,000 daltons was studied in detail.