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Biomedical subjects

C J Birch

Publications and source records attributed to C J Birch.

At least 19 recordsLinked to original sources
PubMed2003

Evidence of patient-to-patient transmission of hepatitis C virus through contaminated intravenous anaesthetic ampoules.

Two separate cases of acute hepatitis C virus (HCV) infection following medical procedures, arthroscopy and colonoscopy, are reported. In both episodes, patient risk factors were reviewed, and staff and other patients' sera were tested for HCV antibodies and RNA. HCV RNA positive samples were genotyped, sequenced, and subjected to phylogenetic analysis. No risk factors for HCV infection were identified for either case except for medical procedures. HCV RNA positive patients were identified preceding both cases on the respective theatre lists. HCV infection in a second low risk patient was also identified. Nucleic acid sequencing and phylogenetic analysis of HCV from the two putative source patients and the three recipient patients demonstrated a high degree of relatedness respectively. The results suggest that patient-to-patient transmission occurred in both episodes via contamination of intravenous anaesthetic ampoules with HCV used on multiple patients. Injectable medication ampoules should not be used for more than one patient.

Adult↗
PubMed2003

Detection of varicella zoster virus in genital specimens using a multiplex polymerase chain reaction.

OBJECTIVE: To compare the relative proportions of varicella zoster virus (VZV) and herpes simplex viruses in specimens obtained from the genital lesions of adults presenting with presumed genital herpes infection. METHODS: Swabs of genital lesions from 6210 patients attending general practices, infectious diseases clinics within hospitals, or sexual health centres for treatment of their genital lesions were tested using polymerase chain reaction (PCR) technology. The multiplexed PCR was capable of detecting herpes simplex virus types 1 and 2 (HSV-1, HSV-2), VZV, and cytomegalovirus in a single sample. RESULTS: A total of 2225 patients had viruses detected by PCR. HSV-1 was detected in 36%, HSV-2 in 61%, and VZV in 2.9% of PCR positive samples. Of the 65 patients with VZV genital infection, many were thought to have HSV infection before laboratory testing. CONCLUSIONS: The finding of VZV in nearly 3% of virus positive genital specimens demonstrates that this virus needs to be considered as a differential diagnosis for genital herpetic lesions. Advice provided to patients with VZV genital infection regarding the source of infection, likelihood of recurrence, and potential for transmission of the virus will be different from that given to patients with HSV infection.

Adolescent↗
PubMed2001

Macrophage tropism of human immunodeficiency virus type 1 isolates from brain and lymphoid tissues predicts neurotropism independent of coreceptor specificity.

The viral determinants that underlie human immunodeficiency virus type 1 (HIV-1) neurotropism are unknown, due in part to limited studies on viruses isolated from brain. Previous studies suggest that brain-derived viruses are macrophage tropic (M-tropic) and principally use CCR5 for virus entry. To better understand HIV-1 neurotropism, we isolated primary viruses from autopsy brain, cerebral spinal fluid, blood, spleen, and lymph node samples from AIDS patients with dementia and HIV-1 encephalitis. Isolates were characterized to determine coreceptor usage and replication capacity in peripheral blood mononuclear cells (PBMC), monocyte-derived macrophages (MDM), and microglia. Env V1/V2 and V3 heteroduplex tracking assay and sequence analyses were performed to characterize distinct variants in viral quasispecies. Viruses isolated from brain, which consisted of variants that were distinct from those in lymphoid tissues, used CCR5 (R5), CXCR4 (X4), or both coreceptors (R5X4). Minor usage of CCR2b, CCR3, CCR8, and Apj was also observed. Primary brain and lymphoid isolates that replicated to high levels in MDM showed a similar capacity to replicate in microglia. Six of 11 R5 isolates that replicated efficiently in PBMC could not replicate in MDM or microglia due to a block in virus entry. CD4 overexpression in microglia transduced with retroviral vectors had no effect on the restricted replication of these virus strains. Furthermore, infection of transfected cells expressing different amounts of CD4 or CCR5 with M-tropic and non-M-tropic R5 isolates revealed a similar dependence on CD4 and CCR5 levels for entry, suggesting that the entry block was not due to low levels of either receptor. Studies using TAK-779 and AMD3100 showed that two highly M-tropic isolates entered microglia primarily via CXCR4. These results suggest that HIV-1 tropism for macrophages and microglia is restricted at the entry level by a mechanism independent of coreceptor specificity. These findings provide evidence that M-tropism rather than CCR5 usage predicts HIV-1 neurotropism.

Amino Acid Sequence↗
PubMed2000

Synthesis, stability, antiviral activity, and protease-bound structures of substrate-mimicking constrained macrocyclic inhibitors of HIV-1 protease.

Three new peptidomimetics (1-3) have been developed with highly stable and conformationally constrained macrocyclic components that replace tripeptide segments of protease substrates. Each compound inhibits both HIV-1 protease and viral replication (HIV-1, HIV-2) at nanomolar concentrations without cytotoxicity to uninfected cells below 10 microM. Their activities against HIV-1 protease (K(i) 1.7 nM (1), 0.6 nM (2), 0.3 nM (3)) are 1-2 orders of magnitude greater than their antiviral potencies against HIV-1-infected primary peripheral blood mononuclear cells (IC(50) 45 nM (1), 56 nM (2), 95 nM (3)) or HIV-1-infected MT2 cells (IC(50) 90 nM (1), 60 nM (2)), suggesting suboptimal cellular uptake. However their antiviral potencies are similar to those of indinavir and amprenavir under identical conditions. There were significant differences in their capacities to inhibit the replication of HIV-1 and HIV-2 in infected MT2 cells, 1 being ineffective against HIV-2 while 2 was equally effective against both virus types. Evidence is presented that 1 and 2 inhibit cleavage of the HIV-1 structural protein precursor Pr55(gag) to p24 in virions derived from chronically infected cells, consistent with inhibition of the viral protease in cells. Crystal structures refined to 1.75 A (1) and 1.85 A (2) for two of the macrocyclic inhibitors bound to HIV-1 protease establish structural mimicry of the tripeptides that the cycles were designed to imitate. Structural comparisons between protease-bound macrocyclic inhibitors, VX478 (amprenavir), and L-735,524 (indinavir) show that their common acyclic components share the same space in the active site of the enzyme and make identical interactions with enzyme residues. This substrate-mimicking minimalist approach to drug design could have benefits in the context of viral resistance, since mutations which induce inhibitor resistance may also be those which prevent substrate processing.

Anti-HIV Agents↗
PubMed2000

Molecular analysis of human immunodeficiency virus strains associated with a case of criminal transmission of the virus.

An investigation was done of the evidence for transmission of human immunodeficiency virus (HIV) from an HIV-positive man to several male and female sex contacts. Phylogenetic analysis of sequences from the gag and env genes showed a close relationship between the predominant virus strains from the source and 2 contacts. However, the likelihood that a female contact was infected by the source could not be determined, despite contact tracing indicating that this may have occurred. One male, shown by contact tracing and molecular evidence to have been infected by the source, subsequently transmitted HIV to his female sex partner. HIV sequence from a plasma sample used as a control in the phylogenetic analysis contained env and gag sequences that were closely related to those from the source. An epidemiologic link between these 2 individuals was subsequently confirmed by contact tracing.

Adult↗
PubMed2000

Effect of protease inhibitors on HIV-1 maturation and infectivity.

The effects of HIV-1 protease inhibitors on proteolytic processing and infectivity of virions produced from lymphocytes chronically infected with the virus were studied. Protease inhibition was detected by the accumulation of the polyprotein precursors Pr55gag and Pr160gag-pol and their cleavage intermediates. Immunoblot analysis demonstrated that while the processing of Pr55gag was largely irreversible, cleavage of Pr160gag-pol proceeded once the inhibitor was removed, although it was not completed during 96 h of subsequent observation. Virions produced during exposure of cells to protease inhibitors regained some degree of infectivity post-withdrawal of the inhibitor, suggesting that the processing of Pr160gag-pol following drug withdrawal resulted in the production of those enzymes necessary to enable at least limited viral replication. When cells were exposed to a protease inhibitor for 72 h then the inhibitor withdrawn, a lag phase of up to 24 h occurred before these cells produced virions with equivalent infectivity to virus produced from cells not exposed to drug. These observations may reflect a clinical situation likely to occur as trough plasma concentrations of protease inhibitors fall below the IC100 for HIV, highlighting the need for adherence to drug regimens containing these inhibitors.

Cell Line↗
PubMed1999

Individuals from North America, Australasia, and Africa are infected with four different genotypes of human herpesvirus 8.

To study human herpesvirus 8 (HHV-8) transmission between individuals and in populations, we developed a system for genetic fingerprinting of HHV-8 strains based on variation in the HHV-8 K1, glycoprotein B (gB), and glycoprotein H (gH) genes. Using this system, we sequenced nearly the entire K1 gene (840 bp); two segments of the gB gene (open reading frame 8), totaling 813 bp; and a 702-bp segment of the gH gene (open reading frame 22) from blood and tissue samples obtained from 40 human immunodeficiency virus-infected and noninfected individuals, including those with Kaposi's sarcoma, primary effusion lymphoma, or Castleman's disease. The specimen collection was assembled from individuals living in diverse geographical locations, including the United States, Australia, New Zealand, Uganda, and Zambia. As reported by others, K1 was the most variable gene, with up to 16% variation at the nucleotide sequence level and up to 32% variation at the amino acid sequence level. Despite this extensive sequence variation, the K1 amino acid sequence contained 14 conserved cysteine sites, suggesting a conserved tertiary structure. gB and gH sequences were highly conserved, in most cases differing by <0.6% in pairwise comparisons. K1 was the most useful gene for strain discrimination, but the other genes enabled the discrimination of strains with identical K1 sequences. Individuals from diverse geographic locations were infected with four different HHV-8 genotypes; strains did not strictly segregate by continent of origin. The majority of HHV-8 strains from the United States and Europe were relatively closely related, whereas some strains identified from Uganda and Australia were phylogenetically distant. Genotype I strains were the most common and were found on three continents. Identical sequences were found in specimens obtained from different body sites and at different times from the same individual.

AIDS-Related Opportunistic Infections↗
PubMed1999

Inactivation of feline calicivirus, a Norwalk virus surrogate.

Norwalk and Norwalk virus-like particles (NVLPs) [also known as small round structured viruses (SRSVs)] are members of the family Caliciviridae and are important causes of gastroenteritis in humans. Little is known about their survival in the environment or the disinfection procedures necessary to remove them from contaminated settings. As NVLPs cannot be grown in tissue culture, survival studies require the use of a closely related cultivable virus. This study assesses the survival of the surrogate feline calicivirus (FCV) after exposure to commercially available disinfectants and a range of environmental conditions. Disinfectants tested included glutaraldehyde, iodine, hypochlorite, a quaternary ammonium-based product, an anionic detergent and ethanol. Complete inactivation of FCV required exposure to 1000 ppm freshly reconstituted granular hypochlorite, or 5000 ppm pre-reconstituted hypochlorite solution. Glutaraldehyde and the iodine-based product effectively inactivated FCV whereas the quaternary ammonium product, detergent and ethanol failed to completely inactivate the virus. The stability of FCV in suspension and in a dried state was assessed after exposure to 4 degrees C, room temperature (20 degrees C) and 37 degrees C. With increasing temperature, the stability of FCV was found to diminish both in suspension and in the dried state. FCV in the dried state did not survive for one day at 37 degrees C. This study provides a basis for establishing guidelines for disinfection protocols to decrease the spread of NVLPs in a community setting.

Animals↗
PubMed1997

Transmission of human and feline immunodeficiency viruses via reused suture material.

Several documented cases of human immunodeficiency virus (HIV) infection have involved unconventional or unknown modes of transmission of the virus. Some such cases have occurred within a surgical setting. We investigated the potential for transmission of HIV on suture material that had been reused following passage through an HIV-infected patient. Initial experiments were conducted in vitro using HIV. To provide stronger evidence that HIV could be transmitted via this route, further experiments were undertaken in vivo using a feline immunodeficiency virus (FIV)/cat model. Both methods indicated the possibility of transmission of virus if suture materials were reused.

Animals↗
PubMed1996

Syncytium-inducing phenotype and zidovudine susceptibility of HIV-1 isolated from post-mortem tissue.

OBJECTIVE: To establish the syncytium-inducing (SI) phenotype and zidovudine (ZDV) susceptibility of HIV-1 isolates obtained from autopsy specimens. METHODS: Isolation of HIV was attempted from autopsy specimens obtained from 76 AIDS patients. Specimens of lymph node, spleen, spinal cord, brain and cerebrospinal fluid (CSF) were processed and cultured with peripheral blood mononuclear cells (PBMC) from seronegative donors. Biological phenotype was determined in a T-lymphocyte line (MT-2). ZDV susceptibility was evaluated in a PBMC-based assay. Sequencing of amino-acid codons in the reverse transcriptase gene previously shown to be associated with ZDV resistance was carried out on a subgroup of isolates. RESULTS: HIV was recovered from tissue specimens and CSF up to 5 days post-mortem, but recovery rate of infectious virus decreased as the time between autopsy and specimen processing increased. There was a lack of concordance between PBMC isolates and isolates from different tissue sites with respect to SI phenotype. ZDV-resistant virus was isolated from post-mortem specimens of patients who had received long-term ZDV therapy up until or shortly before their death. ZDV-sensitive virus re-emerged in the lymph node of patients who ceased treatment several months prior to death. Phenotypically sensitive virus obtained from lymph node tissue of three patients after a relatively short time off ZDV (4-6 months) retained some of the amino-acid substitutions known to be associated with resistance. CONCLUSION: The data suggests that ZDV resistance and re-emergence of sensitive virus does not originate in peripheral cells, and that these cells and tissues are seeded with virus present elsewhere, possibly in the germinal centres of the lymph node.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Isolation of HIV-1 from experimentally contaminated multidose local anaesthetic vials.

OBJECTIVE: To investigate the hypothesis that HIV can be transmitted via contamination of multidose vials of local anaesthetic solution through reuse of needles and syringes. DESIGN AND SETTING: Laboratory study. (1) By experiments with multidose vials and disposable needles and syringes, we identified a sequence of events in which HIV could contaminate the anaesthetic solution. (2) Three anaesthetic solutions were contaminated with a laboratory strain of HIV and tested by viral culture and p24 enzyme immunoassay one, two and four hours later to see how long the virus remained active. RESULTS: (1) Needles and syringes retained small volumes of fluid after use (mean, 25 microL; in syringe alone, mean 16 microL) which could be transferred to multidose vials of local anaesthetic. (2) 10 mL of anaesthetic solution contaminated with 8 microL of HIV-infected solution (equivalent to 1% infected lymphocytes in vivo) contained active virus one hour later. In some settings, HIV could be isolated four hours after exposure. CONCLUSION: When inadvertently contaminated with HIV, multidose solutions represent a potential source of transmissible virus.

Anesthetics, Local↗
PubMed1995

Susceptibility of HIV to inactivation by disinfectants and ultraviolet light.

Assays were developed to assess a variety of conditions and presentations of infectious HIV to potential inactivating sources. A range of commercially available disinfectants with active constituents including glutaraldehyde, chlorine, phenolics, alcohol, iodine and quaternary ammonium compounds was tested. In addition, u.v. light was investigated as a potential inactivating source. All products were assessed against cell-free HIV in culture medium and cell-associated HIV suspended in medium or whole human blood. All products completely inactivated cell-free HIV following a 1 min exposure. However, cell-associated HIV was more resilient, requiring exposure of 5 min or more for some disinfectants. The effectiveness of the disinfectants was further compromised in the presence of blood.

Blood↗
PubMed1994

The use of a scanning proton microprobe to observe anti-HIV drugs within cells.

A series of inorganic polyanions (viz. heteropolytungstates) has been shown to have antiviral activity but there was no evidence to indicate that the drugs reached their site of antiviral (HIV) activity intact. We have shown that with a scanning proton microprobe it is possible to analyse the metal content of individual cells (PBLs) treated with such a polyoxometalate drug and to determine the atomic ratio of the metals within the cell. This was found to be near that in the drug. The distribution of the metals (tungsten and cobalt) within the cell was measured and it was shown that both metals were located in the same region within the cell. These findings would suggest that the drug had entered the cells intact.

Antiviral Agents↗
PubMed1992

Clinical effects and in vitro studies of trifluorothymidine combined with interferon-alpha for treatment of drug-resistant and -sensitive herpes simplex virus infections.

Three AIDS patients with severe cutaneous herpes simplex virus (HSV) infection refractory to therapy with acyclovir and foscarnet (2 patients) were treated with a topical preparation of trifluorothymidine (TFT) and interferon-alpha. Complete healing of lesions occurred in 1 patient; a second had significant regression of the infected area. In the third, the lesion was stabilized twice after application of the preparation and reduced in size after a subsequent treatment. In vitro studies confirmed that isolates from these patients were acyclovir- or acyclovir/foscarnet-resistant. In addition, they revealed strong synergy between TFT and interferon-alpha for these isolates and for strains with wild-type drug sensitivity profiles. Topical TFT/interferon-alpha may be of benefit in the therapy of mucocutaneous HSV infections, especially when they are resistant to treatment with systemic antiviral agents.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Altered sensitivity to antiviral drugs of herpes simplex virus isolates from a patient with the acquired immunodeficiency syndrome.

Acyclovir (ACV)-resistant herpes simplex virus type 2 (HSV-2) was isolated from a patient with acquired immunodeficiency syndrome after long-term but intermittent ACV therapy. These thymidine kinase-defective isolates were sensitive in vitro to foscarnet. While combined therapy with ACV and interferon produced only partial clinical improvement, the in vitro effect of this combination against an ACV-resistant isolate from the patient was strongly synergistic. A short course (10-12 days) of intravenous foscarnet controlled severe ulceration, and clinical improvement lasted 6 months. After recurrence and further courses of foscarnet, however, the patient responded poorly, and subsequent HSV isolates were resistant to both ACV and foscarnet and hypersensitive to aphidicolin.

Acquired Immunodeficiency Syndrome↗