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Biomedical subjects

R J Jackson

Publications and source records attributed to R J Jackson.

At least 109 records · Page 6Linked to original sources
PubMed1996

Mechanisms for mucosal immunogenicity and adjuvancy of Escherichia coli labile enterotoxin.

Escherichia coli labile toxin (LT) was assessed as mucosal immunogen and as adjuvant for tetanus toxoid (TT) in mice. After oral administration of LT, C57BL/6 (H-2b) and BALB/c(H-2d) mice were high mucosal and serum antibody responders, while C3H/HeN (H-2k) mice were low responders. High responders exhibited mainly serum IgG (including IgG1, IgG2a, and IgG2b), as well as IgM and IgA, while mucosal responses were IgA. Analysis of LT-B-specific CD4+ T helper (Th) cells from Peyer's patches (PP) or from spleen revealed a mixed Th1 (interferon-gamma) and Th2 (interleukin-4 and -5) cell pattern. Oral LT given with TT induced TT-specific response patterns identical to LT-B. Analysis of mRNA from TT-specific PP CD4+ Th cells also revealed a mixed Th1- and Th2- type response. Thus, antibody response profiles induced by LT are regulated by both CD4+ Th1 and Th2 cell types.

Adjuvants, Immunologic↗
PubMed1996

Environmental public health surveillance.

A holistic and collaborative approach needs to be taken in the development of environmental public health surveillance systems. Exposure and hazard surveillance integrated with outcome-based surveillance will blend fragmented strands of data into streams of information. Adequate resources and strong leadership are essential to the creation of such surveillance systems.

Child↗
PubMed1996

Construction of recombinant myxoma viruses expressing foreign genes from different intergenic sites without associated attenuation.

Two myxoma virus transient dominant selection vectors were constructed and used to generate recombinant viruses expressing single and double foreign gene insertions from intergenic sites. The intergenic insertion sites were located between the myxoma virus genes MJ2 (thymidine kinase) and MJ2a, and MA24 (beta-subunit RNA polymerase) and MA27 (fusion protein) located approximately 60 and 113 kb from the left-end of the viral genome, respectively. Recombinant myxoma viruses expressing the lacZ gene from either intergenic insertion site retained wild-type virulence. However, expression of the gus gene reduced the virulence of the recombinant viruses in vivo. Northern blot analysis indicated that the major late mRNAs encoding the viral RNA polymerase subunit and fusion protein are both of discrete size. Insertion of a foreign gene under the control of a synthetic late promoter between the MA24 and MA27 genes results in a specific-sized major late transcript for the inserted foreign gene. The MA27 gene transcripts directed by these recombinant viruses are heterogeneous in size, implying the typical pattern of poxvirus late transcription by random 3'-termination prior to polyadenylation. The transcription studies suggest signals located downstream of the insertion site direct 3'-processing of late transcripts irrespective of the gene immediately upstream.

Animals↗
PubMed1996

Efficacy of a potassium nitrate mouthwash in alleviating cervical dentine sensitivity (CDS).

Potassium nitrate (KNO3) has been used previously in a dentifrice or gel to alleviate cervical dentine sensitivity (CDS). The aim of this study was to compare a 3% KNO3 Silica/NaF mouthwash with a NaF/silica mouthwash in a 6-week multi-centre double-blind study. 47 subjects (12M; 35F, mean age 36.2 (SD 11.46) years) participated in the study. Subjects were evaluated for tactile (Yeaple probe) and air sensitivity (dental air syringe) together with subjective perception of pain (0-10 scale) at 0, 2 and 6 weeks. Results for Yeaple probe (gm wt) (Wilcoxon paired rank test) between 6 weeks and baseline, were highly significant for both groups. Differences between groups at 6 weeks were statistically significant. Subjective Yeaple probe scores (paired t-tests) between 6 weeks and baseline were significant for both groups. There were no significant differences (unpaired t-tests) between groups over 6 weeks for subjective Yeaple probe scores. Subjective air scores (paired t-tests) between 6 weeks and baseline were significant for both groups. There were significant differences (unpaired t-tests) between groups in favour of the 3% KNO3/Silica/NaF group at 6 weeks. The 2 weeks and baseline results for both groups were the same as reported for 6 weeks and baseline. The results demonstrated that a 3% KNO3/Silica/NaF mouthwash compared to a Silica/NaF control significantly reduced CDS when evaluated by tactile and thermal stimuli. A 3% KNO3/silica/NaF mouthwash would, therefore appear to have therapeutic potential to alleviate CDS.

Adolescent↗
PubMed1996

Epitope maps of the Escherichia coli heat-labile toxin B subunit for development of a synthetic oral vaccine.

Linear B- and T-cell epitopes spanning all 103 amino acids of the Escherichia coli heat-labile toxin B subunit (LT-B) were assessed in mice orally immunized with native LT or with recombinant Salmonella enteritidis expressing LT-B. Oral administration of native LT induced mucosal immunoglobulin A (IgA) antibodies reactive with an epitope at residues 85 to 91, while IgA induced by recombinant Salmonella LT-B reacted with an epitope at residues 36 to 44. Serum IgG anti-LT-B antibodies from mice orally immunized with either LT or with recombinant Salmonella LT-B were directed to both epitopes. A single T-cell epitope spanning residues 34 to 42 was identified by T-cell proliferative and cytokine responses. When a 20-mer peptide (residues 26 to 45) with B- and T-cell epitopes was given orally to BALB/c (H-2(d)) and B10 congenic (I-A(d), I-A(b), and I-A(k)) mice, significant fecal IgA and serum IgG anti-LT-B antibodies were induced. The peptide also induced LT-B-specific T-cell proliferative responses in these mice. Orally administered LT-B peptide (residues 26 to 45) induced a cytokine profile indicative of both T helper 1- and 2-type cells. The remarkable immunogenicity of this 20-mer peptide makes it a candidate for a vaccine to protect against enterotoxigenic E. coli.

Administration, Oral↗
PubMed1996

Comparison of 2 desensitizing dentifrices with a commercially available fluoride dentifrice in alleviating cervical dentine sensitivity.

Previous studies have demonstrated efficacy of desensitizing dentifrices containing strontium acetate/sodium fluoride (SrAc2F) and potassium chloride/sodium monofluorophosphate (KCl/MFP) in alleviating discomfort arising from cervical dentine sensitivity (CDS). The aim of this investigation, therefore, was to determine efficacy of a SrAc2F dentifrice compared with KCl/MFP and a commercially available fluoride dentifrice containing sodium fluoride/sodium monofluorophosphate (NaMFP). Fifty-six patients participated in a 2-center double-blind, 3-way comparative parallel 6-week clinical study. Patients were evaluated at 0, 2, and 6 weeks for tactile (Yeaple probe), air sensitivity (dental air syringe), and subjective perception of pain (VAS scores). Results for Yeaple probe scores (Wilcoxon tests) between 2 weeks and baseline were highly significant for KCl/MFP, significant for NaMFP and nonsignificant for SrAc2F; scores between 6 weeks and baseline were, however, highly significant for all groups. Subjective Yeaple probe VAS scores (paired t-tests) between 6 weeks and baseline were significant for all groups; significance was demonstrated in the KCl/MFP group between 2 weeks and baseline. Subjective air visual analogue scores (paired t-tests) between 2 weeks and baseline were highly significant for all groups. There were no significant differences between groups at any time point. The results of the study demonstrated that the commercially available fluoride-containing dentifrice was as effective as the 2 desensitizing dentifrices in alleviating CDS over time.

Acetates↗
PubMed1996

Internal initiation of translation of hepatitis C virus RNA: the ribosome entry site is at the authentic initiation codon.

Hepatitis C viral (HCV) RNA includes an internal ribosome entry segment (IRES) that extends some 30 nt into the coding region and promotes internal initiation of translation at the authentic initiation codon at nt 342. The 5'-boundary of this IRES was mapped by in vitro translation and transfection assays and was found to lie between nt 42 and 71. Within these IRES boundaries there are, in most HCV strains, three AUG triplets upstream of the authentic initiation site. Although the first, 5'-proximal, of these is absolutely conserved, a mutational analysis showed that it is not a functional initiation codon. In particular, the G residue could be substituted provided compensatory mutations were made to maintain base pairing. The other two upstream AUGs are not absolutely conserved, and mutation of the third (5'-distal) had little effect on IRES activity. When an additional AUG codon was introduced by single-site mutation just upstream of the authentic initiation codon, it was found to be used when most of the IRES had been deleted to generate an RNA translated by the scanning ribosome mechanism, but was not used in the background of the full-length IRES when internal initiation is operative. These results argue that the IRES promotes direct ribosome entry immediately at, or indeed very close to, the authentic initiation codon, and that the upstream AUGs do not serve as ribosome entry sites.

Base Sequence↗
PubMed1995

Defective point mutants of the encephalomyocarditis virus internal ribosome entry site can be complemented in trans.

Point mutations were introduced at random into cDNA corresponding to nucleotides 260-833 of the encephalomyocarditis virus (EMCV) 5' noncoding region. This region contains the internal ribosome entry site (IRES). The mutations were identified by sequence analysis and the effect on the activity of the IRES was determined using in vitro translation reactions in rabbit reticulocyte lysate. Significantly defective mutants each contained multiple point mutations. These mutants were constructed into a dicistronic mRNA expression plasmid and the activities of the mutant IRES elements were determined using the vaccinia virus/T7 RNA polymerase transient expression system in vivo. The most severely defective of these mutants displayed about 5% of wild-type activity. The activities, relative to wild type, of these mutant IRES elements determined using in vitro and in vivo assays were similar. Two deletion mutants, lacking sequences from the 5' terminus to nt 411 and 484, were also constructed. Each of these deletions inactivated the IRES in vivo (to less than 1% of wild-type activity). Coexpression within cells of the wild-type EMCV IRES, either alone or linked to another coding sequence, enhanced the activity of each of the defective IRES elements except that deleted to nt 484. The results are consistent with a model in which different regions of the IRES participate in a discontinuous transfer of an initiation complex to the 3' end of the IRES element for initiation of protein synthesis to occur.

Animals↗
PubMed1995

Unique features of internal initiation of hepatitis C virus RNA translation.

The question of whether hepatitis C virus (HCV) RNA is translated by a mechanism of internal ribosome entry has been examined by testing whether insertion of HCV sequences between the two cistrons of a dicistronic mRNA promotes translation of the downstream cistron in rabbit reticulocyte lysates. Deletion analysis showed that efficient internal initiation required a segment of the HCV genome extending from about nucleotides 40-370 and that deletions from the 3'-end of this element were highly deleterious. As the authentic initiation codon for HCV polyprotein synthesis is at nucleotide 342, this demonstrates that, besides 5'-UTR sequences, a short length of HCV coding sequences is required for internal initiation. This finding was confirmed in transfection assays of BT7-H cells and was shown to be independent of the nature of the downstream reporter cistron. The strong requirement for coding sequences is in sharp contrast to internal initiation of picornavirus RNA translation. As a probable correlate with this, it was also found that the efficiency of internal initiation was only marginally compromised when the authentic initiation codon was mutated to a non-AUG codon, again in sharp contrast with the picornaviruses. The finding that coding sequences are required for internal initiation has important implications for the design of experiments to test for internal initiation of translation of cellular mRNAs.

Animals↗
PubMed1995

Mucosal adjuvant effect of cholera toxin in mice results from induction of T helper 2 (Th2) cells and IL-4.

Despite pathophysiologic effects including diarrhea, cholera toxin (CT) is a potent mucosal immunogen and adjuvant. We investigated the influence of CT on T helper (Th)-type 1 (Th1) and Th2 cell-regulated Ag-specific B cell isotype and IgG subclass Ab responses elicited when the toxin was co-administered orally with different protein Ags. When mice were orally immunized with tetanus toxoid (TT) and CT as adjuvant, this regimen induced TT-specific secretory IgA responses in the gastrointestinal tract as well as serum IgG, including IgG1 and IgG2b subclasses, and IgA responses. This oral regimen also induced TT- and CT-B-specific IgE responses. In addition, CT also elicited adjuvant effects for Ag-specific IgG1, IgE, and IgA responses when two other protein Ags, OVA and hen egg white lysozyme, were given by the oral route. Quantitative reverse transcriptase-PCR was performed to assess levels of mRNA for Th1 (IFN-gamma) and Th2 (IL-4) cytokine expression in TT-stimulated CD4+ T cell cultures. Both Peyer's patches and splenic CD4+ T cells expressed markedly increased levels of IL-4-specific message, but did not result in changes in IFN-gamma mRNA expression. To determine whether the route of immunization influenced IgE responses, mice were immunized s.c. with TT and CT as adjuvant. Significant increases in total and TT-specific IgE Abs were induced when CT was co-administered. Taken together, these results show that CT acts as a mucosal adjuvant to enhance Th2-type responses and in particular, the IL-4 produced results in a characteristic Ab isotype pattern associated with this cytokine.

Adjuvants, Immunologic↗
PubMed1995

The protective role of enteral IgA supplementation in neonatal gut origin sepsis.

Preterm infants and infants unable to breast feed are particularly susceptible to gut origin sepsis. Many studies have shown the benefits of breast milk in decreasing the incidence of bacterial infections in neonates. Little in vivo work has focused on prevention of neonatal gut origin sepsis with breast milk components. The aim of this study was to determine whether supplementation of a standard neonatal formula with exogenous, luminally administered, human secretory IgA protects against gut origin sepsis in a newborn rabbit model. Sixty New Zealand white rabbit pups were delivered by cesarean section 1 day preterm and divided into two groups--the IgA group (n = 26) and the non-IgA group (n = 34). Animals were gavage-fed a standard artificial formula (KMR) twice daily. The IgA group was supplemented on days 3 and 4 with 6.25 mg/kg of human secretory IgA. The non-IgA group received an equal volume of saline. On the evening of day 3, the animals were orally challenged with Escherichia coli K100. The quantity of bacteria that colonized the cecum was similar in the two groups. The quantity of bacteria that translocated to the mesenteric lymph node, liver, and spleen was significantly lower in the IgA group (P < .05). The incidence of translocation to the organs was also significantly lower in the IgA group (P < .05). The exogenous secretory IgA showed specificity to E coli K100 by ELISA. These data show that neonatal formula supplemented with human secretory IgA decreases the incidence and quantity of bacterial translocation of E coli K100 in a neonatal rabbit model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Myxoma virus as a vaccine vector for rabbits: antibody levels to influenza virus haemagglutinin presented by a recombinant myxoma virus.

To determine whether myxoma virus (MV) could be used as a vector for antigen presentation to European rabbits (Oryctolagus cuniculus), despite its immunosuppressive properties, a recombinant MV expressing the influenza virus haemagglutinin (HA) was constructed. Domestic rabbits, inoculated with the recombinant virus, developed high plasma antibody titres to the HA and IgG to HA was also detected in vaginal secretions. Antibody titres to HA obtained with recombinant MV were similar to titres obtained in rabbits inoculated with vaccinia virus expressing the HA. These results indicate that MV is an efficient vector for antigen presentation in rabbits.

Animals↗
PubMed1995

Potential carcinogenicity of chloral hydrate--a review.

Chloral hydrate is commonly used to sedate children for diagnostic or therapeutic procedures. The drug has been extensively used for many years, but there are remarkably few data on its long-term health effects. Concern in this regard is raised by recent studies showing chloral hydrate to be genotoxic, causing chromosome changes and other effects in vivo and in vitro. In addition, chloral hydrate is a reactive metabolite of trichloroethylene, a known carcinogen, and is structurally similar to other carcinogenic intermediates. Two carcinogenicity studies performed using the oral route of administration in mice indicate that the drug is potentially carcinogenic--in one case after a single dose lower than the typical dose used for sedation. Practitioners should be aware of chloral hydrate's genotoxicity and potential carcinogenicity. Discretion in its use seems appropriate until further studies clarify its long term health consequences.

Animals↗
PubMed1995

Direct evidence that polypyrimidine tract binding protein (PTB) is essential for internal initiation of translation of encephalomyocarditis virus RNA.

The requirement of PTB, polypyrimidine tract binding protein, for internal initiation of translation has been tested using an RNA affinity column to deplete rabbit reticulocyte lysates of PTB. The affinity column was prepared by coupling CNBr-activated Sepharose with the segment of the 5'-untranslated region of encephalomyocarditis virus (EMCV) RNA previously shown to bind PTB. Lysates passed through this column were devoid of PTB, and were incapable of internal initiation of translation dependent on the EMCV 5'-untranslated region, while retaining the capacity for translation dependent on ribosome scanning. Full activity for internal initiation was restored by the addition of recombinant PTB at the physiologically relevant concentration of about 5 micrograms/mL. When various PTB deletion mutants were tested, it was found that this activity required virtually the full-length protein. Thus, PTB is an essential protein for internal initiation promoted by the EMCV 5'-untranslated region. However, the PTB-depleted lysate retained the capacity for internal initiation promoted by the 5'-untranslated regions of another cardiovirus, Theiler's murine encephalomyelitis virus, and of the unrelated hepatitis C virus, and in neither case did addition of recombinant PTB stimulate internal initiation. Therefore, PTB is not a universal internal initiation factor that is indispensable in every case of internal ribosome entry.

Animals↗
PubMed1994

Oral vaccine models: multiple delivery systems employing tetanus toxoid.

We have not yet directly examined the Th cell responses induced by using Salmonella/BRD 847 as a vector nor have we performed these experiments following immunization with microspheres. However, production of high serum levels of antigen-specific IgG1 may be indicative of a Th2-type response, whereas high serum levels of IgG2a may reflect a Th1-type response. An important issue in using various oral delivery systems is whether the system(s) employed affects the Th cell response to the same antigen. We therefore analyzed the serum antigen-specific IgG subclasses induced in each of the model systems we studied. Table 2 presents these results. Clearly, oral administration of soluble TT with CT as an adjuvant induced an IgG1 subclass, and encapsulation of TT within microspheres had no effect on this Th2-type response. On the other hand, oral immunization with live Salmonella expressing fragment C of tetanus toxin induced a strong IgG2a subclass response indicative of a Th1-type response. It should be noted that protection against a lethal TT challenge was afforded by elevated levels of both anti-TT IgG1 and IgG2a subclasses. We intend to examine the cytokine profiles in spleen CD4+ T cells from mice immunized with microspheres or Salmonella following in vitro antigen stimulation to confirm the T helper type responses suggested by the IgG subclass data. It will also be important to examine the cytokine patterns induced in Peyer's patch CD4+ T cells following immunization of C57BL/6 with Salmonella/BRD 847. Whereas analysis of the serum IgG subclass profile indicated a strong IgG2a response and thus a systemic Th1-type pattern, this vector also induced a good mucosal IgA response. If our current hypothesis concerning S-IgA production is correct, we would expect a predominant Th2-type profile in CD4+ T cells from Peyer's patch in these mice. Such a result would emphasize the bifurcation of T-cell responses in the systemic versus the mucosal immune environments. The data obtained to data suggest that adjuvants and various vehicle delivery systems may influence the induction of distinct T helper cell subsets to a specific antigen. The unique cytokine arrays produced by these T-cell subsets influence the immune responses in terms of systemic Ig subclasses produced, cell-mediated immune responses, and the production of mucosal S-IgA antibodies. Although additional studies are necessary, the manipulation of T-cell subsets employing adjuvants, antigen packaging, or perhaps even the addition of individual cytokines to various formulations holds significant promise for optimizing immune responses to orally administered vaccines.

Adjuvants, Immunologic↗