Effect of the length and effective diameter of F-actin on the filament orientation in liquid crystalline sols measured by x-ray fiber diffraction

We examined factors that affect the filament orientation in F-actin sols to prepare highly well-oriented liquid crystalline sols suitable for x-ray fiber diffraction structure analysis. Filamentous particles such as F-actin spontaneously align with one another when concentrated above a certain threshold concentration. This alignment is attributed to the excluded volume effect of the particles. In trying to improve the orientation of F-actin sols, we focused on the excluded volume to see how it affects the alignment. The achievable orientation was sensitive to the ionic strength of the solvent; the filaments were better oriented at lower ionic strengths, where the effective diameter of the filament is relatively large. Sols of longer filaments were better oriented than those of shorter filaments at the same concentration, but the best achievable orientation was limited, probably because of the filament flexibility. The best strategy for making well-oriented F-actin sols is therefore to concentrate F-actin filaments of relatively short length (<1 micrometer) by slow centrifugation in a low-ionic-strength solvent (<30 mM).

Capillary electrophoresis for therapeutic drug monitoring of antiepileptics

We examined the use of capillary electrophoresis for therapeutic drug monitoring of antiepileptic drugs. Micellar electrokinetic capillary chromatography (MEKC) with a diode array detector simultaneously determined concentrations of zonisamide, a new type of antiepileptic drug, and phenobarbital, phenytoin and carbamazepine, typical antiepileptic drugs, in human serum. Zonisamide levels in human serum obtained by MEKC correlated well with levels obtained by high-performance liquid chromatography. The serum levels of phenobarbital, phenytoin and carbamazepine determined by MEKC were almost equal to those obtained by fluorescence polarization immunoassay. The reproducibility of separation and quantification with MEKC for intra- and inter-day assays were appropriate. This MEKC method could provide a simple and efficient therapeutic drug monitoring method for antiepileptic drugs, especially in patients treated with a combination of zonisamide and other antiepileptic drugs. MEKC may be an attractive method for therapeutic drug monitoring, because of its specificity of separation, automation of procedure, ease of method development, low cost, small aqueous buffer amounts, speed of analysis, small injection volume and high environment-directed performance.

Quality evaluation by capillary electrophoresis of amphotericin B injection after filtration through various membrane filters

The determination of amphotericin B, an antifungal agent, was developed using micellar electrokinetic capillary chromatography (MEKC) with a diode array detector. Repeatability and intermediate precision of MEKC analysis were acceptable. A high correlation was found between amphotericin B levels in pharmaceutical solutions obtained by MEKC and those by high-performance liquid chromatography (HPLC) (r = 0.994). This MEKC method is therefore useful for the determination of amphotericin B. The concentration of amphotericin B did not significantly change after filtration through polyethersulfone (PES, 0.2 microm) and polyvinylidene difluoride (PVDF, 0.45 microm) membrane filters. When the Fungizone injection was filtered through PES (0.2 microm) and added to 5% dextrose for injection (500 mL), particulate matters larger than 10 microm decreased by 64% to a level under the standard defined by United States Pharmacopoeia (USP XXIII). PVDF filtration (0.45 microm) did not have this effect. Our results suggest that filtration of Fungizone injection through PES (0.2 microm) membrane filters is recommended for the preparation of intravenous amphotericin B fluid.

1H nuclear magnetic resonance study on equilibrium between two four-stranded solution conformations of short d(CnT)

NMR analysis of d(C4T) showed the slow exchange between two distinct tetramers (each fully symmetric) in solution. For one tetramer, NOE cross-peak patterns characteristic of an i-motif structure (H1'-H1' and H6-H1'/H1'-H6) were observed between C1 and T5, indicating that this tetramer takes a completely intercalated conformation where the T5 residue is stacked on the C1.C1(+) pair of the other duplex (S-form). The other was found to be a tetramer in which one of the duplexes is shifted by one nucleotide unit (R-form), resulting in nonstacking 3' end thymidine residues and an equal number of stacked C.C+ pairs to that of the S-form. The same spectral features were observed for d(C3T) but neither for d(TC3) nor d(TC4), indicative of the critical role of the position of the thymidine residue in the tetrad isomerization. From NMR denaturation profiles, the S-forms were found to be more stable than the R-forms, and the linear relationship between the logarithm of the equilibrium constant (K = [tetramer]/[single]4) and the inverse of temperature (1/T) was confirmed for both forms, indicating conformity to the two-state transition model. Both enthalpy and entropy values of the formation of the S-form from four single strands were more negative than those of the R-form. The enthalpy term should contribute to the stabilization of the S-forms at low temperatures. The difference of the free energy values [DeltaG degrees(S-form) - DeltaG degrees(R-form)] was found to be -2.1 and -2.7 kJ.mol-1 at 20 degreesC for d(C4T) and d(C3T), respectively, explaining the higher stability of the S-forms. With increasing temperature, these two topologies were found to comparably exist at equilibrium in solution with slow exchange via dissociation to the single strands. A biological role of this topological isomerization is also suggested.

Effects of preparation conditions on the monodispersity of albumin microspheres

Monodisperse albumin microspheres were successfully prepared by both chemical or thermal hardening methods via membrane emulsification using microporous glass membranes with uniform pore sizes. The monodispersity of the microspheres was found to depend strongly on parameters such as albumin concentration, emulsifier concentration, and volume ratio of the internal aqueous phase (albumin solution) to the dispersion medium (organic solvent). The optimum conditions for obtaining monodisperse albumin microspheres are described.

Oxypurinol, a xanthine oxidase inhibitor and a superoxide scavenger, did not attenuate ischemic neuronal damage in gerbils

The superoxide (O2.-) scavenging activity and neuroprotective effects of oxypurinol, a xanthine oxidase inhibitor, were compared with those of alpha-phenyl-N-tert-butyl nitrone (PBN). The rate constant for the reaction of oxypurinol with O2.- at pH 7.4 was 1.71 x 10(3) M(-1) s(-1) which was more than 100-fold that of PBN (1.65 x 10 M(-1) s(-1)). Oxypurinol inhibited the release of O2.- from stimulated neutrophils better than did PBN. However, oxypurinol did not attenuate the ischemic neuronal damage in gerbils, while PBN did. These results indicate that neither xanthine oxidase inhibiting activity nor O2.- scavenging activity correlates to the therapeutic efficacy of neuroprotective agents in ischemic-reperfusion injury.

Misincorporation of 2'-deoxyoxanosine 5'-triphosphate by DNA polymerases and its implication for mutagenesis

2'-Deoxyoxanosine (dOxo) is a novel DNA lesion produced by the reaction of 2'-deoxyguanosine (dGuo) with nitrous acid and nitric oxide [Suzuki, T., Yamaoka, R., Nishi, M., Ide, H., and Makino, K. (1996) J. Am. Chem. Soc. 118, 2515-2516]. In this work, 2'-deoxyoxanosine 5'-triphosphate (dOTP) was prepared by nitrous acid treatment of 2'-deoxyguanosine 5'-triphosphate (dGTP), and its incorporation into DNA by DNA polymerases was investigated to elucidate the substrate and mutagenic properties of dOTP. Primed M13mp18 DNA was replicated by Escherichia coli DNA polymerase I Klenow fragment (Pol I Kf) in the presence of three normal dNTPs and dOTP or 2'-deoxyxanthosine 5'-triphosphate (dXTP), another major product of reaction of dGTP with nitrous acid and nitric oxide. dOTP substituted for dGTP and to a lesser extent for dATP, while dXTP substituted slightly for dGTP but not for dATP. Neither dOTP nor dXTP substituted for dCTP and dTTP. The similar results were obtained for the incorporation by T7 DNA polymerase deficient in 3'-5' exonuclease [T7(exo-)]. To quantify the substitution efficiency, kinetic parameters for incorporation of dOTP and dXTP opposite template C or T by Pol I Kf (exo-) were determined and compared with those for dGTP using oligodeoxynucleotide templates. Incorporation efficiencies (f = Vmax/Km) of dOTP (f = 0.28% min-1 microM-1) and dXTP (f = 0.10% min-1 microM-1) opposite template C were much lower than that of dGTP (f = 1506% min-1 microM-1). Frequencies of mutagenic incorporation of dOTP opposite template T were dependent on the nearest neighbor base pairs, and 1.6-3.9-fold higher than those for dGTP with the nearest neighbors containing G.C pairs. dXTP was not incorporated opposite template T with all four nearest neighbors. These data suggest that formation of dOTP, but not dXTP, from dGTP with nitrous acid or nitric oxide in the intracellular nucleotide pool would result in the elevation of the mutation frequency.

[Proliferative potential of the ear drum in the process of gerbiline cholesteatoma formation]

Mongolian gerbil frequently develop spontaneous cholesteatoma. As we reported previously, in the process of gerbiline cholesteatoma formation, effusions inside the pars flaccida are always found in the ears during the early stage, and epidermal growth factor (EGF) is also localized in the pars flaccida, especially in the mucous layer. In this study, to clarify the process of gerbiline cholesteatoma formation, we studied 22 gerbiline temporal bones by using a monoclonal antibody against bromodeoxyuridine (BrdU). BrdU-labeled cells demonstrate a proliferative potential. We also used a carbon dye method to label the micro-vase in 14 gerbiline temporal bones. Cells showing BrdU uptake were more abundant, as demonstrated immunohistochemically, in the pars flaccida of ears with early cholesteatomas than in the pars flaccida of normal ears (p < 0.01). The pars flaccida of ears with early cholesteatomas showed hypertrophy of both epithelial layers, and hyperkeratosis of the epidermal layer. BrdU-labeled cells in the pars flaccida were more localized in the mucous layers than in the epidermal layers. In contrast, in ears with cholesteatomas, BrdU-labeled cells were less abudant than in ears with early cholesteatomas. In addition, BrdU-labeled cells in the pars tensa and external auditory epidermal layers were not increased in ears with any stage of cholesteatoma formation. We used a carbon dye method to detect the micro-vasa in the intermediate layer of the ear drum. Carbon-dye-labeled vasa were more numerous in the pars flaccida with early cholesteatomas than in the pars flaccida of normal ears or ears with cholesteatomas. It is highly suspected that angiogenesis was stimulated in the pars flaccida with early cholesteatomas, because stimulation of angiogenesis by EGF has been reported. The above findings suggest that the mucous layer of the pars flaccida has the greatest proliferative potential in the process of cholesteatoma formation. Angiogenesis in the pars flaccida appears to be a reaction to proliferative changes in the mucous and epidermal layers. These changes are probably stimulated by effusion inside the pars flaccida.

[Measurement of regional cerebral blood flow using one-point arterial blood sampling and microsphere model with 123I-IMP: correction of one-point arterial sampling count by whole brain count ratio]

A correction method was proposed for measurement of the regional cerebral blood flow using one-point arterial blood sampling and a microsphere model with N-isopropyl-p-(123I)iodoamphetamine (123I-IMP). Instead of using continuous arterial blood sampling octanol-extracted counts, one-point arterial sampling whole blood counts corrected by the whole brain count ratio using 1-minute planar SPECT images were employed. The experimental subjects were 189 patients with cerebrovascular disorders. 123I-IMP, 222 MBq, was administered by intravenous infusion. Continuous arterial blood sampling was carried out for 5 minutes, and arterial blood was also sampled once at 5 minutes after 123I-IMP administration. Then the whole blood count of the one-point arterial sampling was compared with the octanol-extracted count of the continuous arterial sampling. A positive correlation was found between the two values (r = 0.87, p < 0.001). The correction method was carried out by calculation as follows. The ratio of the continuous sampling octanol-extracted count (OC) to the one-point sampling whole blood count (TC5) was compared with the whole brain count ratio (5:29 ratio, Cn) using 1-minute planar SPECT images, centering on 5 and 29 minutes after 123I-IMP administration. Correlation was found between the two values (r = 0.72, p < 0.001). The following relationship was shown from the correlation equation. OC/TC5 = 0.390969 x Cn-0.08924. Based on this correlation equation, we calculated the theoretical continuous arterial sampling octanol-extracted count (COC). COC = TC5 x (0.390969 x Cn-0.08924). There was good correlation between the value calculated with this equation and the actually measured value (r = 0.94, p < 0.001). The coefficient improved to r = 0.94 from the r = 0.87 obtained before using the 5:29 ratio for correction. For 23 of these 189 cases, another one-point arterial sampling was carried out at 6, 7, 8, 9 and 10 minutes after the administration of 123I-IMP. The correlation coefficient was also improved for these other point samplings when this correction method using the 5:29 ratio was applied. It was concluded that it is possible to obtain highly accurate input functions, i.e., calculated continuous arterial sampling octanol-extracted counts, using one-point arterial sampling whole blood counts by performing correction using the 5:29 ratio.

[Exercises on a bicycle ergometer in a family of diabetes mellitus associated with a mutation of mitochondrial DNA]

The serum pyruvate and lactate levels were studied after exercise on a bicycle ergometer in a family of diabetes mellitus (DM) associated with a mutation at nucleotide 3243 in the mitochondrial gene. A 56-year-old Japanese woman with the mutation at a percentage of 5% in the blood had insulin-dependent DM and sensory hearing loss without muscle symptoms. Her serum lactate and pyruvate levels increased markedly during and after exercise on a bicycle ergometer. Two of her sons were found to have the same mutation at a percentage of 17% and 18%, respectively. Her 26-year-old son was found to have borderline DM after oral glucose loading, although he showed no abnormalities of the metabolism of pyruvate and lactate. Her 31-year-old son showed no abnormalities after oral glucose loading and after exercise on a bicycle ergometer. Although the same mutation causes more severe MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes), little is known about whether these diabetic patients are subclinically involved with myopathy. The noninvasive ergometer exercise with determination of serum pyruvate and lactate may be useful in evaluating the severity of myopathy in these patients.

[Experience of coronary and great vessel angiography by transradial puncture]

The introduction of 5F and even 4F catheters allows transradial coronary arteriography and aortography. The efficacy and limitation of angiography via the radial artery using 5F catheter was prospectively evaluated in 200 consecutive patients. Cardiac catheterization with diagnostic angiography was successfully performed in 198 of 200 patients, including 11 patients with acetylcholine provocation test, 21 with bypass graft angiography, 38 with aortography and 5 with biopsy of the left ventricular myocardium. The transradial approach was not indicated in one patient without normal Allen's test and in one with weak radial pulse. In four patients, guide wire support was needed during manipulation because of marked tortuosity in the innominate artery. The sheath was removed immediately after the completion of the procedure, followed by 5 hours of tourniquet hemostasis without manual compression. The postoperative resting period was reduced. Peripheral vasospasm occurred in 2.5% of cases, but could be eliminated by administration of isosorbide dinitrate and lidocaine. Subcutaneous hemorrhage in the puncture site was observed in 3.0% of cases, but required no additional compression. Transradial catheterization is a minimally invasive, safe and practical alternative to the brachial or femoral artery approach in patients with normal Allen's test.

[A case of late adult-onset dentatorubral-pallidoluysian atrophy (DRPLA) successfully treated with V-P shunt operation]

A 44-year-old Japanese man was diagnosed as having late adult-onset dentatorubral-pallidoluysian atrophy (DRPLA), whose CAG repeats in the DRPLA gene were 60 and 15. He developed gait disturbance, limb ataxia, pyramidal tract signs, dementia, and psychiatric symptoms including character changes within a few years of the above diagnosis. His T 2-weighted brain MRI showed symmetric high-signal lesions in the cerebral white matter and brain stem, in addition to cerebellar, brain stem, and cerebral cortical atrophy. Since the results of RI cisternography indicated that he manifested the clinical features of normal pressure hydrocephalus (NPH), V-P shunt operation was done. In a week after the operation, his gait disturbance, pyramidal tract signs, dementia and psychiatric symptoms were remarkably improved. White matter lesions have been thought to be concomitant with late adult-onset DRPLA patients, but some of these patients may have characteristics of NPH pathophysiology.

Intermediate in reaction of 2'-deoxycytidine with nitrous acid

Using reversed phase (RP) HPLC analysis, we reinvestigated the reaction of dCyd with nitrous acid. When 10 mM 2'-deoxycytidine (dCyd) was incubated with 100 mM NaNO2 in 1.0 M acetate buffer (pH 3.7) at 37 degrees C, an unknown product (referred to compound 1) was detected. The time course of the yield of compound 1 showed profile characteristic of an intermediate. Under the physiological conditions, compound 1 was converted exclusively to dUrd with a life time of ca. 300 h. Elucidation of genotoxic effects of compound 1 may be an important subject of the future study.

Detection of 2'-deoxyoxanosine by capillary electrophoresis

We have investigated capillary electrophoresis separation of oxanine (Oxa), a base moiety of 2'-deoxyoxanosine (Figure 1), from various bases. Oxa was not well separated from the others by micelle electrokinetic chromatography which is a general method for separating of the bases. On the other hand, capillary zone electrophoresis showed much improved separation when used pH 12 where the six-membered ring of Oxa is opened.

Mechanism and intermediate for formation of 2'-deoxyoxanosine

A reaction mechanism for the direct formation of 2'-deoxyoxanosine (dOxo) from 2'-deoxyguanosine (dGuo) by nitrous acid (HNO2) or nitric oxide (NO) was explored by using guanosine (Guo) and its methyl derivatives. HNO2 treatment of 1-methylguanosine (1-Me-Guo) indicated that the exocyclic amino nitrogen (N5) of dOxo originates from imino nitrogen (N1) of dGuo. A short-lived intermediate detected in the Guo-HNO2 system by reversed phase (RP) HPLC was converted into oxanosine (Oxo) and xanthosine (Xao) at neutral pH. Based on these findings, we discuss the reaction mechanism for the formation of dOxo.

Lactobacillus casei inhibits antigen-induced IgE secretion through regulation of cytokine production in murine splenocyte cultures

BACKGROUND

Lactobacillus casei is a nonpathogenic gram-positive bacterium widely used in dairy products and has been shown to enhance the cellular immunity of the host.

METHODS

To examine the inhibitory effect of L. casei on IgE production, splenocytes obtained from ovalbumin (OVA)-primed BALB/c mice were restimulated in vitro with the same antigen in the presence of heat-killed L. casei. The effect of this bacterium on T helper (Th) phenotype development was also examined with naive T cells from OVA-specific T cell receptor-transgenic mice.

RESULTS

L. casei induced IFN-gamma, but inhibited IL-4 and IL-5 secretion, and markedly suppressed total and antigen-specific IgE secretion by OVA-stimulated splenocytes. The inhibitory effect of L. casei on IgE, IL-4, and IL-5 production was partially abrogated by addition of neutralizing antibody to IFN-gamma. Augmented IL-12 production was also observed in the cell cultures containing L. casei, and anti-IL-12 monoclonal antibody completely restored the IgE, IL-4, and IL-5 production to the control levels. The IL-12 augmentation by L. casei was macrophage-dependent. The Th cell development assay showed the ability of L. casei to induce Th1 development preferentially. This effect was also completely blocked by anti-IL-12 antibody.

CONCLUSIONS

This is the first demonstration that a nonpathogenic microorganism, L. casei, can inhibit antigen-induced IgE production through induction of IL-12 secretion by macrophages. The findings suggest a potential use of this organism in preventing IgE-mediated allergy.

Anticoagulant effects of sulphonated polyisoprenes

Sulphonated polyisoprenes (SPIPs) having various molecular weights and sulphonate group contents were synthesized and their anticoagulant activities investigated. Prolongation of blood clotting time, prothrombin time and activated partial thromboplastin time were observed in the presence of SPIPs. The anticoagulant activity in blood was affected mainly by total sulphonate group concentration; however, the molecular weight of SPIPs also had an influence. Since thrombin time was prolonged by SPIPs for a condition which supplied enough thrombin to the assay system, interactions between fibrinogen and SPIPs may be one of the anticoagulant mechanisms of SPIPs.

Determination of salicylic acid in human serum with capillary zone electrophoresis

The determination of salicylic acid (SA), a metabolite of aspirin, in human serum was developed using capillary zone electrophoresis (CZE) with diode array detection. The reproducibility of separation and quantification with CZE analysis of the extract of SA from human serum was appropriate for the intra- and inter-day assay coefficients. A high correlation was revealed between the serum SA levels in volunteers determined by CZE and those determined by a fluorescence polarization immunoassay (r=0.973, n = 12), although the former values were slightly higher than the latter. There were no peaks interfering with the assay of SA by internal standard method. This CZE method could provide a simple and efficient method for monitoring SA in patients.

Complete nucleotide sequences of 93-kb and 3.3-kb plasmids of an enterohemorrhagic Escherichia coli O157:H7 derived from Sakai outbreak

Enterohemorrhagic Escherichia coli (EHEC) O157:H7, derived from an outbreak in Sakai city, Japan in 1996, possesses two kinds of plasmids: a 93-kb plasmid termed pO157, found in clinical EHEC isolates world-wide and a 3.3-kb plasmid termed pOSAK1, prevalent in EHEC strains isolated in Japan. Complete nucleotide sequences of both plasmids have been determined, and the putative functions of the encoded proteins and the cis-acting DNA sequences have been analyzed. pO157 shares strikingly similar genes and DNA sequences with F-factor and the transmissible drug-resistant plasmid R100 for DNA replication, copy number control, plasmid segregation, conjugative functions and stable maintenance in the host, although it is defective in DNA transfer by conjugation due to the truncation and deletion of the required genes and DNA sequences. In addition, it encodes several proteins implicated in EHEC pathogenicity such as an EHEC hemolysin (HlyA), a catalase-peroxidase (KatP), a serine protease (EspP) and type II secretion system. pOSAK1 possesses a ColE1-like replication system, and the DNA sequence is extremely similar to that of a drug-resistant plasmid, NTP16, derived from Salmonella typhimurium except that it lacks drug resistance transposons.

Inhibition of human T-cell leukemia virus type 1 replication by antisense env oligodeoxynucleotide

Human T-cell leukemia virus type 1 (HTLV-1) infection is associated with adult T-cell leukemia and HTLV-associated myelopathy/tropical spastic paraparesis. Inhibition of HTLV-1 transmission is important to prevent the above HTLV-1-associated diseases. We used the antisense oligodeoxynucleotides (oligos) complementary to the first splice junction, rex responsive site, gag, env, tax, rex, and p21 and evaluated the effects on the syncytium formation between HTLV-1 producing human T-cell line, C9/PL cells, and HTLV-1-uninfected human glioma cell line, U251-MG cells. The syncytium formation was significantly inhibited the virion production assayed by antisense oligos to env, tax, gag, p21, and rex, with antisense oligo to env being the most inhibitory. Antisense oligos to env and tax also inhibited reverse transcriptase activity. Antisense oligo to env may have a potential as a preventive measure of HTLV-1 replication and transmission in vivo.

Neuroprotective effects of pterin-6-aldehyde in gerbil global brain ischemia: comparison with those of alpha-phenyl-N-tert-butyl nitrone

The superoxide (O2.-) scavenging activity and the neuroprotective effects of pterin-6-aldehyde (P6A), a xanthine oxidase inhibitor, were examined and compared with those of alpha-phenyl-N-tert-butyl nitrone (PBN), a spin trapping agent. The scavenging activity of P6A was more potent than that of PBN by 150-fold in neutrophil/phorbol myristate acetate O2.- generating system. P6A attenuated the neuronal damage with a much smaller dose and a greater efficiency than PBN in global brain ischemia in gerbils. These findings suggest that P6A is a more potent neuroprotective agent than PBN and has possible therapeutic effects against various diseases in which O2.- is involved.

Size Dependence of Polymer Composition in the Surface Layer of Poly(acrylamide-co-acrylic acid) Hydrogel Microspheres

Poly(acrylamide-co-acrylic acid) hydrogel microspheres of four different average sizes were prepared using a membrane emulsification technique. These four kinds of microspheres had average diameters of 1.35, 2.33, 3.09, and 7.43 &mgr;m in distilled water and were all fairly monodisperse. Their surface properties were studied by measuring the electrophoretic mobility of the microspheres. The mobility values were negative at pH 7.4 with the ionic strengths between 0.005 and 0.154 at 25&deg;C. More negative mobility values were obtained with smaller microspheres than the larger ones. By analyzing the data with an electrokinetic theory for "soft" surfaces, it was found that smaller microspheres have higher surface charge density than the larger ones, although all kinds of microspheres were prepared from monomer solutions with the same monomer composition. The observed size dependence of the electrophoretic mobility suggests that copolymerization of acrylamide monomers and acrylic acid monomers does not proceed homogeneously within a microsphere. That is, charged acrylic acid monomers have a tendency to be localized in the microsphere core region, whereby the surface region of microspheres becomes poor in charges, reducing the mobility of larger microspheres. This is not the case for smaller microspheres, so that their mobility becomes more negative. Copyright 1998 Academic Press. Copyright 1998Academic Press

Antibody-dependent enhancement of feline infectious peritonitis virus infection in feline alveolar macrophages and human monocyte cell line U937 by serum of cats experimentally or naturally infected with feline coronavirus

Infection of the type II feline infectious peritonitis virus (FIPV) strain 79-1146 to primary feline alveolar macrophages and human monocyte cell line U937 was enhanced by the sera of cats experimentally infected with the 79-1146 strain, but not those of cats infected with KU-2 or UCD-1 strain of type I FIPV. The experiments using sera of cats with feline infectious peritonitis (FIP) and of cats naturally infected with feline coronavirus (FCoV) revealed that infection of the FIPV 79-1146 strain to the U937 cells was enhanced only by the sera of cats infected with type II FIPV or feline enteric coronavirus. The samples positive for antibody-dependent enhancement (ADE) activity had high neutralizing antibody titers against the FIPV 79-1146 strain and the samples negative for ADE activity had low neutralizing antibody titers. These findings support the previous results where a monoclonal antibody with neutralizing activity had high ADE activity, suggesting that there was a close relationship between the neutralization and enhancement sites. And then it is also suggested that ADE of infection is likely to be induced by re-infection with the same serotype of virus in type II FIPV infection. Furthermore, U937 cells are considered useful and can be substituted for the feline macrophages for determining ADE of FIPV-infection.