Genetic, structural and functional diversities of human complement components C4A and C4B and their mouse homologues, Slp and C4

The complement protein C4 is a non-enzymatic component of the C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. The covalent binding of C4 to immunoglobulins and immune complexes (IC) also enhances the solubilization of immune aggregates, and the clearance of IC through complement receptor one (CR1) on erythrocytes. Human C4 is the most polymorphic protein of the complement system. In this review, we summarize the current concepts on the 1-2-3 loci model of C4A and C4B genes in the population, factors affecting the expression levels of C4 transcripts and proteins, and the structural, functional and serological diversities of the C4A and C4B proteins. The diversities and polymorphisms of the mouse homologues Slp and C4 proteins are described and contrasted with their human homologues. The human C4 genes are located in the MHC class III region on chromosome 6. Each human C4 gene consists of 41 exons coding for a 5.4-kb transcript. The long gene is 20.6 kb and the short gene is 14.2 kb. In the Caucasian population 55% of the MHC haplotypes have the 2-locus, C4A-C4B configurations and 45% have an unequal number of C4A and C4B genes. Moreover, three-quarters of C4 genes harbor the 6.4 kb endogenous retrovirus HERV-K(C4) in the intron 9 of the long genes. Duplication of a C4 gene always concurs with its adjacent genes RP, CYP21 and TNX, which together form a genetic unit termed an RCCX module. Monomodular, bimodular and trimodular RCCX structures with 1, 2 and 3 complement C4 genes have frequencies of 17%, 69% and 14%, respectively. Partial deficiencies of C4A and C4B, primarily due to the presence of monomodular haplotypes and homo-expression of C4A proteins from bimodular structures, have a combined frequency of 31.6%. Multiple structural isoforms of each C4A and C4B allotype exist in the circulation because of the imperfect and incomplete proteolytic processing of the precursor protein to form the beta-alpha-gamma structures. Immunofixation experiments of C4A and C4B demonstrate > 41 allotypes in the two classes of proteins. A compilation of polymorphic sites from limited C4 sequences revealed the presence of 24 polymophic residues, mostly clustered C-terminal to the thioester bond within the C4d region of the alpha-chain. The covalent binding affinities of the thioester carbonyl group of C4A and C4B appear to be modulated by four isotypic residues at positions 1101, 1102, 1105 and 1106. Site directed mutagenesis experiments revealed that D1106 is responsible for the effective binding of C4A to form amide bonds with immune aggregates or protein antigens, and H1106 of C4B catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens. The expression of C4 is inducible or enhanced by gamma-interferon. The liver is the main organ that synthesizes and secretes C4A and C4B to the circulation but there are many extra-hepatic sites producing moderate quantities of C4 for local defense. The plasma protein levels of C4A and C4B are mainly determined by the corresponding gene dosage. However, C4B proteins encoded by monomodular short genes may have relatively higher concentrations than those from long C4A genes. The 5' regulatory sequence of a C4 gene contains a Spl site, three E-boxes but no TATA box. The sequences beyond--1524 nt may be completely different as the C4 genes at RCCX module I have RPI-specific sequences, while those at Modules II, III and IV have TNXA-specific sequences. The remarkable genetic diversity of human C4A and C4B probably promotes the exchange of genetic information to create and maintain the quantitative and qualitative variations of C4A and C4B proteins in the population, as driven by the selection pressure against a great variety of microbes. An undesirable accompanying byproduct of this phenomenon is the inherent deleterious recombinations among the RCCX constituents leading to autoimmune and genetic disorders.

Technical innovation to calibrate the gantry angle indicators of linear accelerators

Finding the actual zero degree of the gantry angle is important in order to perform the mechanical quality assurance (QA) of linear accelerators. To determine real zero, we must locate a "good surface" which could be defined as a plane on the surface of the gantry head that is perpendicular to the direction of radiation. The actual gantry angle could then be defined as the angle between vertical, as indicated by a plumb bob, and the direction of the beam axis that could be indicated by the position of a BB placed in the central axis and its shadow. From this we located the real zero degree and the good surface. The good surface can be applied to check the important mechanical readouts. The technique we introduce could solve the essential problems of a traditional QA technique, as well as taking up an important role in the quality assurance of a patient's treatment.

Culicoides arakawae (Diptera: Ceratopogonidae) population succession in relation to leucocytozoonosis prevalence on a chicken farm in Taiwan

Leucocytozoonosis caused by Leucocytozoon caulleryi is a significant disease prevalent in open chicken houses of southern and eastern Asia. L. caulleryi is transmitted by Culicoides arakawae, a blood-sucking vector. Leucocytozoonosis prevalence is influenced by vector population succession. Thus this examination was performed on a farm to investigate vector population succession and leucocytozoonosis prevalence in experimental chicks and to obtain the ecology data for assessing the prevalence. The findings were as follows: (1) C. arakawae adults might be highly host specific because they were rarely discovered on cattle or pig farms, and none of the experimental chickens were infected by L. caulleryi on those farms. (2) Identifying and counting gorged and gravid C. arakawae to assess leucocytozoonosis prevalence is a practical strategy. The critical vector index should be 5.0 calculated by dividing the smallest vector mean from the prevalent period by the largest vector mean from the population not causing leucotocytozoonosis. (3) Taking vector means from three or more collections each month, should be the best assessment of leucocytozoonosis prevalence because C. arakawae succession appears to have a 3-week periodicity. Hopefully, these findings will contribute to assessing leucocytozoonosis prevalence.

Molecular genetics of the human MHC complement gene cluster

The human major histocompatibility complex (MHC) complement gene cluster (MCGC) is a highly variable region that is characterized by polymorphisms, variations in gene size and gene number, and associations with diseases. Deficiencies in complement C2 are either due to abolition of C2 protein synthesis by mini-deletions that caused frameshift mutations, or blocked secretion of the C2 protein by single amino acid substitutions. One, two or three C4 genes may be present in a human MCGC haplotype and these genes may code for C4A, C4B, or both. Deficiencies of C4A or C4B proteins are attributed to the expression of identical C4 isotypes or allotypes from the C4 loci, the absence or deletion of a C4 gene, 2-bp insertion at exon 29 or 1-bp deletion at exon 20 that caused frameshift mutations. The C4 genes are either 21 or 14.6 kb in size due to the presence of endogenous retrovirus HERV-K(C4) in the intron 9 of long C4 genes. A deletion or duplication of a C4 gene is always accompanied by its neighboring genes, RP at the 5' region, and CYP21 and TNX at the 3' region. These four genes form a genetic unit termed the RCCX module. In an RCCX bimodular structure, the pseudogene CYP21A, and partially duplicated gene segments TNXA and RP2 are present between the two C4 loci. The RCCX modular variations in gene number and gene size contributed to unequal crossovers and exchanges of polymorphic sequences/mutations, resulting in the homogenization of C4 polymorphisms and acquisitions of deleterious mutations in RP1, C4A, C4B, CYP21B and TNXB genes. RD, SKI2W, DOM3Z and RP1 are the four novel genes found between Bf and C4. RD and Ski2w proteins may be related to RNA splicing, RNA turnover and regulation of translation. The functions of Dom3z and RP1 are being investigated. The complete genomic DNA sequence between C2 and TNX is now available. This should facilitate a complete documentation of polymorphisms, mutations and disease associations for the MCGC.

Organizations and gene duplications of the human and mouse MHC complement gene clusters

The MHC complement gene cluster (MCGC) in most people contains thirteen structural genes, pseudogenes and gene segments. Novel genes RD, SKI2W, DOM3Z and RP1 are organized as two head-to-head gene pairs between complement gene Bf and the first locus of C4. Southern blot analysis shows that single-copy genes for DOM3Z are detectable in primates and other mammals. Sequence analyses revealed that the exon- intron structures of human and mouse DOM3Z genes are identical. Both human and mouse DOM3Z transcripts exhibit splice variants at the 5' regions, although the open reading frames remain identical. Cloning and characterization of the mouse RP1 cDNA revealed a reading frame for 254 amino acids with a bipartite nuclear localization signal close to the amino terminus. The mouse RP1 gene consists of 7 exons and spans 12.9 kb. Located in intron 4 of mouse RP1 is an endogenous retrovirus that probably confers the androgen-responsive expression of the Slp protein in certain male mice. The availability of the complete human and mouse MCGC genomic and cDNA sequences allows further deliberate analyses of gene duplications and evolution. The intergenic region between mouse SLP and C4 genes is more than six times larger than the corresponding region in humans. It contains the functional gene steroid CYP21A, long stretches of repetitive DNA elements, and three partially duplicated gene segments TNXA, SKI2W2 and RP2. The modular duplications of human and mouse RP-C4-CYP21-TNX (RCCX) are sharply different as SKI2W2 is absent in the human MCGC, and TNXA and RP2 are smaller in size but higher in sequence conservation in humans.

Mixed germ cell tumor presenting as intratumoral hemorrhage: report of a case originated from the pineal region

A 17-year-old male patient was brought to our clinic because of sudden onset of headache, vomiting, followed by transient loss of consciousness during a strenuous exercise. Neurologic examinations revealed that the patient had severe sensorimotor and brain stem dysfunction. Examinations of cranial CT and MR imaging showed a huge heterogeneously enhanced tumor originated from the pineal region with tumoral hemorrhage. The tumor markers were found to be high in AFP but not the beta-HCG and CEA. A clinical diagnosis highly suggestive of germ cell tumor was made. Prior to the planned emergency radiation therapy, he received an external ventricular drainage (EVD) and open biopsy of the tumor. Due to a postoperative complication of cerebellar hemorrhage observed 8 hours later, another maneuver was therefore required to extirpate the pineal tumor and cerebellar hematoma. The histological diagnosis proved to be a mixed germ cell tumor with tumoral hemorrhage. Spontaneous intratumoral hemorrhage in germ cell tumor of the pineal region is rare, probably due to compromised venous circulation within the tumor. The bleeding propensity, which may contribute to the formation of cerebellar hematoma, warrants a special attention when a biopsy procedure is to be performed.

An unequal crossover between the RCCX modules of the human MHC leading to the presence of a CYP21B gene and a tenascin TNXB/TNXA-RP2 recombinant between C4A and C4B genes in a patient with juvenile rheumatoid arthritis

The RCCX module of the human MHC class III region is comprised of four genes arranged in tandem: RP, complement C4, steroid 21-hydroxylase (CYP21), and tenascin X (TNX). Variations in the number and genes of the RCCX modules may lead to genetic and/or autoimmune diseases. Restriction fragment length polymorphism (RFLP) analysis was utilized to determine the RCCX modular variation in patients with juvenile rheumatoid arthritis (JRA). In JRA patient L1, RFLP analysis suggested the presence of a bimodular RCCX structure containing both C4A long and C4B short genes, yet missing the markers for the CYP21A and TNXA genes usually located between the C4A and C4B genes. The 7.5-kb genomic fragment spanning the CYP21-TNX-RP2 genes was cloned and sequenced, revealing that a genetic recombination occurred between TNXA of a bimodular RCCX chromosome and TNXB of a monomodular RCCX chromosome. This recombination results in a new MHC haplotype with a CYP21B gene and a TNXB/TNXA-RP2 recombinant between the two C4 genes. Elucidation of the breakpoint region provides further evidence for the instability of the MHC class III gene region as a result of the RCCX modular variation.

[Polymorphic study of CSF1PO locus in Han population in Wuhan]

Using the primers designed by Yoshida, the amplified fragment length polymorphism of the STR locus CSF1PO was studied. 8 alleles were determined from 312 unrelated individuals of Han population living in Wuhan. Sensitivity and suitability of the PCR-STR typing using Yoshida's primers were compared with the one using Hammond's. Results proved that Yoshida's method were more suitable in forensic identification than that of Hammond, especially in the typing of severely degraded DNA samples.

Modular variations of the human major histocompatibility complex class III genes for serine/threonine kinase RP, complement component C4, steroid 21-hydroxylase CYP21, and tenascin TNX (the RCCX module). A mechanism for gene deletions and disease associations

The frequent variations of human complement component C4 gene size and gene numbers, plus the extensive polymorphism of the proteins, render C4 an excellent marker for major histocompatibility complex disease associations. As shown by definitive RFLPs, the tandemly arranged genes RP, C4, CYP21, and TNX are duplicated together as a discrete genetic unit termed the RCCX module. Duplications of the RCCX modules occurred by the addition of genomic fragments containing a long (L) or a short (S) C4 gene, a CYP21A or a CYP21B gene, and the gene fragments TNXA and RP2. Four major RCCX structures with bimodular L-L, bimodular L-S, monomodular L, and monomodular S are present in the Caucasian population. These modules are readily detectable by TaqI RFLPs. The RCCX modular variations appear to be a root cause for the acquisition of deleterious mutations from pseudogenes or gene segments in the RCCX to their corresponding functional genes. In a patient with congenital adrenal hyperplasia, we discovered a TNXB-TNXA recombinant with the deletion of RP2-C4B-CYP21B. Elucidation of the DNA sequence for the recombination breakpoint region and sequence analyses yielded definitive proof for an unequal crossover between TNXA from a bimodular chromosome and TNXB from a monomodular chromosome.

Deficiency of human complement protein C4 due to identical frameshift mutations in the C4A and C4B genes

The complement protein C4, encoded by two genes (C4A and C4B) on chromosome 6p, is the most polymorphic among the MHC III gene products. We investigated the molecular basis of C4 deficiency in a Finnish woman with systemic lupus erythematosus. C4-specific mRNA was present at low concentrations in C4-deficient (C4D) patient fibroblasts, but no pro-C4 protein was detected. This defect in C4 expression was specific in that synthesis of two other complement proteins was normal. Analysis of genomic DNA showed that the proposita had both deleted and nonexpressed C4 genes. Each of her nonexpressed genes, a C4A null gene inherited from the mother, a C4A null gene, and a C4B null gene inherited from the father, all contained an identical 2-bp insertion (TC) after nucleotide 5880 in exon 29, providing the first confirmatory proof of the C4B pseudogene. This mutation has been previously found only in C4A null genes. Although the exon 29/30 junction is spliced accurately, this frameshift mutation generates a premature stop at codon 3 in exon 30. These truncated C4A and C4B gene products were confirmed through RT-PCR and sequence analysis. Among the possible genetic mechanisms that produce identical mutations is both genes, the most likely is a mutation in C4A followed by a gene conversion to generate the mutated C4B allele.

[Study of the high polymorphism STR locus-FGA in Chinese population]

Population genetic study of the complicated STR locus-FGA was performed by the method of PCR in Han population samples. A total of 21 different alleles including 7 interalleles and 63 different genotypes were observed in 349 unrelated individuals. The observed genotype discrimination showed no significant deviation from Hardy-Weinberg equilibrium and 51 family studies showed no mutation. According to the results obtained in this study(DP = 0.9612, PE = 0.7007, PIC = 0.8333), this system can be used as an useful means in forensic identification of both criminal and paternity case.

Regulation by phosphorylation of the zinc finger protein KRC that binds the kappaB motif and V(D)J recombination signal sequences

The DNA binding protein KRC (forkappaB binding andrecognitioncomponent of the V(D)J recombination signal sequence) belongs to a family of large zinc finger proteins that bind to the kappaB motif and contains two widely separated DNA binding structures. In addition to the kappaB motif, KRC fusion proteins bind to the signal sequences of V(D)J recombination to form highly ordered complexes. Here, we report that KRC may be regulated by post-translational modifications. Specific protein kinases present in the nucleus of pre-B cells phosphorylated a KRC fusion protein at tyrosine and serine residues. Such protein modifications increased DNA binding, thereby providing a mechanism by which KRC responds to signal transduction pathways. KRC is a substrate of epidermal growth factor receptor kinase and P34cdc2 kinase in vitro. Our results suggest that activation of the KRC family of transcription factors may provide a mechanism by which oncogenic tyrosine kinases regulate genes with kappaB-controlled gene regulatory elements.

Influence of incubation time, inoculum size, and glucose concentrations on spectrophotometric endpoint determinations for amphotericin B, fluconazole, and itraconazole

We addressed the influence of the incubation time (24 h versus 48 h), starting inoculum size (standard inoculum size, approximately 10(3) CFU/ml, versus large inoculum size, approximately 10(4) CFU/ml), and supplementation with 2% glucose of RPMI 1640 medium on the spectrophotometric determination of the MICs of amphotericin B, fluconazole, and itraconazole. We compared the MICs determined spectrophotometrically with those determined by the standard broth macrodilution method (National Committee for Clinical Laboratory Standards approved guideline M27-A). The agreement between the results of the spectrophotometric and standard methods for amphotericin B testing was 100%; this agreement was independent of the inoculum size and incubation time. On the other hand, the agreement for the results for fluconazole testing and itraconazole testing was dependent on the inoculum size and incubation time. With large inoculum size, excellent agreement can be achieved at 24 h. With standard inoculum size, acceptable agreement can be achieved only at 48 h. In contrast to previous observations, the addition of 2% glucose did not have any significant impact on the growth density at 24 h, nor did it improve the agreement with the standard method. Furthermore, supplemental glucose might falsely elevate the MIC at 48 h.

Four ubiquitously expressed genes, RD (D6S45)-SKI2W (SKIV2L)-DOM3Z-RP1 (D6S60E), are present between complement component genes factor B and C4 in the class III region of the HLA

The association of the HLA class III region with many diseases motivates the investigation of unidentified genes in the 30-kb segment between complement component genes Bf and C4. RD, which codes for a putative RNA binding protein, is 205 bp downstream of Bf. SKI2W (HGMW-approved symbol SKIV2L), a DEVH-box gene probably involved in RNA turnover, is 171 bp downstream of RD (HGMW-approved symbol D6S45). RP1 (HGMW-approved symbol D6S60E) is located 611 bp upstream of C4. The DNA sequence between human RD and RP1 was determined and the exon-intron structure of SKI2W elucidated. SKI2W consists of 28 exons. The putative RNA helicase domain of Ski2w is encoded by 9 exons. Further analysis of the 2.5-kb intergenic sequence between SKI2W and RP1 led to the discovery of DOM3Z. The full-length cDNA sequence of DOM3Z encodes 396 amino acids with a leucine zipper motif. Dom3z-related proteins are present in simple and complex eukaryotes. In Caenorhabditis elegans, Dom3z-related protein could be involved in the development of germ cells. Human RD-SKI2W and DOM3Z-RP1 are arranged as two head-to-head oriented gene pairs with unmethylated CpG sequences at the common 5' regulatory region of each gene pair. The ubiquitous expression pattern suggests that these four genes are probably housekeeping genes.

Effects of early postnatal dexamethasone therapy on calcium homeostasis and bone growth in preterm infants with respiratory distress syndrome

The effects of dexamethasone therapy on calcium homeostasis and bone growth were evaluated in 49 infants (24 placebo and 25 dexamethasone) who participated in a double-blind trial of early dexamethasone therapy for the prevention of chronic lung disease. Dexamethasone (0.25 mg kg(-1) b.i.d. on d 1-7; 0.12 mg kg(-1) b.i.d. on d 8-14; 0.05 mg kg(-1) b.i.d. on d 15-21; 0.02 mg kg(-1) b.i.d. on d 22-28) or saline placebo was given i.v. Serum calcium (Ca), phosphorus (P) and parathyroid hormone (PTH), and the corresponding urinary excretion of calcium (FECa) and phosphorus (FEP) were measured on d 2, 3, 7, 10, 14, 21 and 28 after starting the study. Radiographic evaluations of bone growth were also evaluated. Infants in the dexamethasone group had significantly higher PTH on d 2 (p < 0.01), 7 and 14 (p < 0.05) than infants in the placebo group. The dexamethasone-treated infants also had significantly higher FEP on d 2, 7 and 14 (p < 0.05) and lower FECa on d 7 and 14 (p < 0.05) than control infants. There was no significant difference between the groups in bone growth during the study. It was concluded that early dexamethasone therapy causes a transient elevation in PTH without apparent change in bone growth. The long-term effect remains to be evaluated further.

Technetium-99m-HMPAO brain SPECT in neonates with hypoglycemic encephalopathy

Regional brain injury in three neonates with hypoglycemic encephalopathy are presented using serial 99mTc-hexamethyl propyleneamine oxime (HMPAO) SPECT and, for comparison, MRI. During the acute stage, both 99mTc-HMPAO SPECT and MRI reveal abnormalities in the posterior cerebrum. Technetium-99m-HMPAO SPECT reveals further areas of insult, for example the frontal lobes. The degree of hypoperfusion correlates with the clinical severity of hypoglycemia during the neonatal period and subsequent neurological sequelae. Follow-up with HMPAO SPECT several months after insult demonstrates persistent hypoperfusion in some areas, mainly in the occipital and posterior parietal regions. MRI can depict morphological changes with superior resolution. Because morphological change generally follows slowly after functional change, MRI is less sensitive than HMPAO SPECT in detecting and predicting the extent of hypoglycemic cerebral injury during the acute phase. HMPAO SPECT during the acute stage is a valuable tool for evaluating the extent and severity of brain injury in neonates with hypoglycemic encephalopathy.

Holoprosencephaly due to mutations in ZIC2, a homologue of Drosophila odd-paired

Holoprosencephaly (HPE) is the most common structural anomaly of the human brain and is one of the anomalies seen in patients with deletions and duplications of chromosome 13. On the basis of molecular analysis of a series of patients with hemizygous deletions of the long arm of chromosome 13, we have defined a discrete region in band 13q32 where deletion leads to major developmental anomalies (the 13q32 deletion syndrome). This approximately 1-Mb region lies between markers D135136 and D13S147. Patients in which this region is deleted usually have major congenital malformations, including brain anomalies such as HPE or exencephaly, and digital anomalies such as absent thumbs. We now report that human ZIC2 maps to this critical deletion region and that heterozygous mutations in ZIC2 are associated with HPE. Haploinsufficiency for ZIC2 is likely to cause the brain malformations seen in 13q deletion patients.

The human DEVH-box protein Ski2w from the HLA is localized in nucleoli and ribosomes

The human helicase gene SKI2W is located between RD and RP1 in the class III region of the major histocompatibility complex. Transcripts of SKI2W are detectable in RNA samples isolated from multiple tissues. The protein product Ski2w shares striking amino acid sequence similarities to the yeast antiviral protein Ski2p that controls the translation of mRNAs, probably based on the mRNA structural integrity. Whether this translational regulation mechanism for cellular and viral RNAs exists in mammals is under investigation. Antisera against human Ski2w were generated using fusion proteins produced in bacteria or insect cells. Western blot analysis showed that the endogenous Ski2w protein is approximately 140 kDa in size and is enriched in polysomal fractions of cytoplasmic extracts from HeLa cells. Ribosomal profile studies revealed that Ski2w distributed throughout the entire sucrose gradient in the presence of Mg2+, but co-sedimented with the 18S rRNA-containing 40S subunit and the small ribosomal subunit protein S27a in the presence of EDTA. The co-sedimentation of Ski2w with the 40S subunit is not affected by RNase A treatment of the cell extract, or the addition of KCl to 0.5 M, suggesting that Ski2w is associated with the 40S ribosomal subunit. Indirect immunofluorescence experiments showed that human Ski2w is localized in the nucleoli and in the cytoplasm. In essence, human Ski2w is present at the sites of ribosome biogenesis and protein synthesis.

Voriconazole against fluconazole-susceptible and resistant candida isolates: in-vitro efficacy compared with that of itraconazole and ketoconazole

We compared the in-vitro activity of fluconazole, itraconazole, ketoconazole and voriconazole against 67 blood isolates of Candida spp. exhibiting a wide range of fluconazole MICs (0.125 to >64 mg/L). Voriconazole was the most potent in vitro, followed by itraconazole, ketoconazole and fluconazole. Itraconazole and voriconazole had in-vitro activity against fluconazole-susceptible and -resistant candida isolates. Higher itraconazole and voriconazole MICs were observed in isolates exhibiting higher fluconazole MICs, suggesting cross-resistance. Itraconazole and voriconazole MICs of > or =16 mg/L were observed only in Candida albicans and Candida tropicalis. Candida krusei and Candida glabrata exhibited itraconazole MICs of 0.5-1 mg/L and voriconazole MICs of 0.25-0.5 mg/L.

In vitro comparative efficacy of voriconazole and itraconazole against fluconazole-susceptible and -resistant Cryptococcus neoformans isolates

In vitro susceptibility testing for 50 clinical isolates of fluconazole-susceptible or -resistant Cryptococcus neoformans was performed with itraconazole and voriconazole. Voriconazole was more potent than itraconazole for fluconazole-susceptible isolates and as potent as itraconazole for fluconazole-susceptible dose-dependent isolates and for fluconazole-resistant isolates. For fluconazole-resistant isolates, the voriconazole and itraconazole MICs ranged from 1 to 2 microg/ml.

Comparison of PCR and culture to the indirect fluorescent-antibody test for diagnosis of Potomac horse fever

Potomac horse fever is an acute systemic equine disease caused by Ehrlichia risticii. Currently, serologic methods are widely used to diagnose this disease. However, serologic methods cannot determine whether the horse is presently infected or has been exposed to ehrlichial antigens in the past. The purpose of the present study was to compare the sensitivities of the nested PCR and cell culture with that of the indirect fluorescent-antibody (IFA) test for the diagnosis of Potomac horse fever. Blood and fecal specimens serially collected from a pony experimentally infected with E. risticii Maryland, blood specimens serially collected from mice inoculated with E. risticii Ohio 380, and blood and/or fecal specimens collected from 27 horses which had clinical signs compatible with Potomac horse fever were examined. These horses resided in Kentucky, Indiana, Pennsylvania, and Vermont. The IFA test titer became positive after 6 days postinoculation (p.i.) for the pony. A culture of the blood of the pony was positive for E. risticii starting on day 1 and was positive through day 28 p.i. By the nested PCR, E. risticii was detectable in the blood and feces of the pony starting on day 1 and was detectable through day 32 p.i. E. risticii was detected in the blood of subclinically infected mice by the nested PCR. Twenty-two clinical specimens were seropositive for E. risticii by the IFA test, with titers ranging from 1:20 to 1:1,280. E. risticii was cultured from 95% (20 of 21) of seropositive clinical blood specimens. E. risticii was detected in the blood by PCR in 81% (17 of 20) of the culture-positive clinical specimens. The study indicated that the nested PCR is as sensitive as culture for detecting infection with E. risticii.

Combination therapy with fluconazole and flucytosine in the murine model of cryptococcal meningitis

This study elucidates the role of combined fluconazole and flucytosine as therapy for cryptococcosis in the murine model of meningitis. Three strains of Cryptococcus neoformans for which the range of fluconazole MICs was wide--2 microg/ml (susceptible strain), 8 microg/ml (moderately susceptible strain), and 32 microg/ml (resistant strain)--were used for infection. One day postinfection, the mice were randomized into eight treatment groups: placebo; flucytosine (40 mg/kg of body weight/day); fluconazole at 3 mg/kg/day (low dosage), 10 mg/kg/day (moderate dosage), or 20 mg/kg/day (high dosage); and combined flucytosine and fluconazole at low, moderate, or high doses of fluconazole. Three major findings were demonstrated: (i) correlation between the MICs for the isolates and the in vivo effectiveness of fluconazole as assessed by the reduction in cryptococcal brain burden, (ii) a dose-response curve (a higher dose of fluconazole was significantly more efficacious than a lower dose [P < 0.001]), and (iii) synergism between fluconazole and flucytosine (therapy with a combination of fluconazole and flucytosine was superior to therapy with either agent alone [P < 0.01]).