The role of mutation accumulation in HIV progression

The onset of AIDS is characterized by the collapse of the immune system after a prolonged asymptomatic period. The mechanistic basis of this disease progression has remained obscure, hindering the development of effective therapies. Here I present a mechanism that underlies the deterioration of the immune system during HIV infection. The elevated turnover of lymphocytes throughout the asymptomatic period is postulated to result in the accumulation of deleterious mutations, which impairs immunological function, replicative ability and viability of lymphocytes. This mutational meltdown is proposed to occur throughout the hierarchy of lymphocyte progenitors, resulting in the deterioration of lymphocyte regeneration and an ensuing rise in viral loads. A mathematical model is used to illustrate this mechanism of progressive immunological deterioration. Mutation accumulation may explain not only the decline in CD4+T cells, but also the functional deterioration of CD4+T cells, CD8+T cells and B cells, and the exhaustion of lymphocyte regeneration.     

Safety and Tolerability of Conserved Region Vaccines Vectored by Plasmid DNA,Simian Adenovirus and Modified Vaccinia Virus Ankara Administered to Human Immunodeficiency Virus Type 1-Uninfected Adults in a Randomized,Single-Blind Phase I Trial

Trial Design

HIV-1 vaccine development has advanced slowly due to viral antigenic diversity, poor immunogenicity and recently, safety concerns associated with human adenovirus serotype-5 vectors. To tackle HIV-1 variation, we designed a unique T-cell immunogen HIVconsv from functionally conserved regions of the HIV-1 proteome, which were presented to the immune system using a heterologous prime-boost combination of plasmid DNA, a non-replicating simian (chimpanzee) adenovirus ChAdV-63 and a non-replicating poxvirus, modified vaccinia virus Ankara. A block-randomized, single-blind, placebo-controlled phase I trial HIV-CORE 002 administered for the first time candidate HIV-1- vaccines or placebo to 32 healthy HIV-1/2-uninfected adults in Oxford, UK and elicited high frequencies of HIV-1-specific T cells capable of inhibiting HIV-1 replication in vitro. Here, detail safety and tolerability of these vaccines are reported.

Methods

Local and systemic reactogenicity data were collected using structured interviews and study-specific diary cards. Data on all other adverse events were collected using open questions. Serum neutralizing antibody titres to ChAdV-63 were determined before and after vaccination.

Results

Two volunteers withdrew for vaccine-unrelated reasons. No vaccine-related serious adverse events or reactions occurred during 190 person-months of follow-up. Local and systemic events after vaccination occurred in 27/32 individuals and most were mild (severity grade 1) and predominantly transient (<48 hours). Myalgia and flu-like symptoms were more strongly associated with MVA than ChAdV63 or DNA vectors and more common in vaccine recipients than in placebo. There were no intercurrent HIV-1 infections during follow-up. 2/24 volunteers had low ChAdV-63-neutralizing titres at baseline and 7 increased their titres to over 200 with a median (range) of 633 (231-1533) post-vaccination, which is of no safety concern.

Conclusions

These data demonstrate safety and good tolerability of the pSG2.HIVconsv DNA, ChAdV63.HIVconsv and MVA.HIVconsv vaccines and together with their high immunogenicity support their further development towards efficacy studies.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01151319","term_id":"NCT01151319"}}NCT01151319     

Reciprocal regulation of nuclear import of the yeast MutSα DNA mismatch repair proteins Msh2 and Msh6

DNA mismatch recognition is performed in eukaryotes by two heterodimers known as MutSα (Msh2/Msh6) and MutSβ (Msh2/Msh3) that must reside in the nucleus to function. Two putative Msh2 nuclear localization sequences (NLS) were characterized by fusion to green fluorescent protein (GFP) and site-directed mutagenesis in the context of Msh2. One NLS functioned in GFP targeting assays and both acted redundantly within Msh2. We examined nuclear localization of each of the MutS monomers in the presence and absence of their partners. Msh2 translocated to the nucleus in cells lacking Msh3 and Msh6; however, cells lacking Msh6 showed significantly decreased levels of nuclear Msh2. Furthermore, the overall protein levels of Msh2 were significantly diminished in the absence of Msh6, particularly if Msh2 lacked a functional NLS. Msh3 localized in the absence of Msh2, but Msh6 localization depended on Msh2 expressing functional NLSs. Overall, the nuclear levels of Msh2 and Msh6 decline when the other partner is absent. The data suggest a stabilization mechanism to prevent free monomer accumulation in the cytoplasm.     

Impact of Schistosoma mansoni on Malaria Transmission in Sub-Saharan Africa

Background

Sub-Saharan Africa harbors the majority of the global burden of malaria and schistosomiasis infections. The co-endemicity of these two tropical diseases has prompted investigation into the mechanisms of coinfection, particularly the competing immunological responses associated with each disease. Epidemiological studies have shown that infection with Schistosoma mansoni is associated with a greater malaria incidence among school-age children.

Methodology

We developed a co-epidemic model of malaria and S. mansoni transmission dynamics which takes into account key epidemiological interaction between the two diseases in terms of elevated malaria incidence among individuals with S. mansoni high egg output. The model was parameterized for S. mansoni high-risk endemic communities, using epidemiological and clinical data of the interaction between S. mansoni and malaria among children in sub-Saharan Africa. We evaluated the potential impact of the S. mansoni–malaria interaction and mass treatment of schistosomiasis on malaria prevalence in co-endemic communities.

Principal Findings

Our results suggest that in the absence of mass drug administration of praziquantel, the interaction between S. mansoni and malaria may reduce the effectiveness of malaria treatment for curtailing malaria transmission, in S. mansoni high-risk endemic communities. However, when malaria treatment is used in combination with praziquantel, mass praziquantel administration may increase the effectiveness of malaria control intervention strategy for reducing malaria prevalence in malaria- S. mansoni co-endemic communities.

Conclusions/Significance

Schistosomiasis treatment and control programmes in regions where S. mansoni and malaria are highly prevalent may have indirect benefits on reducing malaria transmission as a result of disease interactions. In particular, mass praziquantel administration may not only have the direct benefit of reducing schistosomiasis infection, it may also reduce malaria transmission and disease burden.     

Microbial control of cotton pests: use of the naturally occurring entomopathogenic fungus Aspergillus sp. (BC 639) in the management of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) and beneficial insects on transgenic cotton crops

The commercial adoption of transgenic Bacillus thuringiensis (Bt) cotton (Bollgard II®) reduced the use of insecticides to control Helicoverpa spp. However, the ineffectiveness of the Bt toxin against sucking pests such as silverleaf whiteflies (Bemisia tabaci) resulted in a marked increase in B. tabaci populations and in the use of insecticides to control this pest. The effect of the entomopathogenic fungus Aspergillus sp. BC 639 on B. tabaci and beneficial insects (predominantly predatory insects) was studied in commercial cotton field trials. The results showed that oil-based extracts of the entomopathogenic fungus BC 639 control the number of B. tabaci adults and nymphs in commercial transgenic cotton crops. The BC 639 fungus caused 60.0%, 67.2%, and 68.8% mortality in adults, and 54.6%, 62.3%, and 51.7% in nymphs at 7, 14, and 21 days after treatment, respectively, relative to the unsprayed controls. The effect of BC 639 at concentrations of 125, 250, and 500?ml/ha on low-density B. tabaci (～10 nymphs/leaf) did not differ significantly from that of the commercial insecticide (pyriproxifen). However, at higher densities (>50 nymphs per leaf), low concentrations of BC 639 (125 and 250?ml/ha) were not as effective as 500?ml/ha BC 639 in successfully controlling the pest. A simple graphic analysis suggested that the more B. tabaci nymphs per leaf, the fewer adults per leaf, and that once the number of nymphs increased to ～70 per leaf, a negative feedback regulatory effect reduced the survivorship of the nymphs and adults and/or caused the emigration of the adults from the contaminated leaves in search of new resources. Therefore, the ability of BC 639 to control B. tabaci adults and nymphs with minimal effects on predatory insects indicates its potential utility in supplementing integrated pest management programmes for cotton crops.     

Preliminary results from a controlled evaluation of thermal biofeedback as a treatment for essential hypertension

In a controlled trial, thermal biofeedback (n=20) and abbreviated progressive relaxation (n=22) were compared in the treatment of mild to moderate hypertensive patients whose blood pressures (BP) were initially controlled on two medications. For the clinical end point of maintaining control of BP on a single drug after treatment, biofeedback was superior to relaxation training (at 3 months, 47% success for biofeedback versus 23% for relaxation). This same result tended to be true for patient-measured home BPs. BPs from laboratory psychophysiological testing showed no consistent advantage for one treatment over the other.This research was supported by a grant from NHLB1, HL-27622.     

A review of in vitro modelling approaches to the identification and modulation of squamous metaplasia in the human tracheobronchial epithelium

Squamous metaplasia in the tracheobronchial epithelium (TBE) involves the replacement of the normal pseudostratified mucociliary epithelium with a stratified squamous epithelium. Squamous metaplasia is considered to be an adaptive response that protects the lumen from the effects of inhaled airborne pollutants, but which might also feature as a pre-neoplastic lesion preceding squamous cell carcinoma. With the exception of transglutaminase I, involucrin, and cytokeratins 5, 6 and 13, few markers that contribute to the squamous phenotype have been identified in human TBE that can be used in diagnosis or to monitor its development in laboratory investigations, and current models are inadequate to provide statistically meaningful data. Therefore, new predictive markers have been identified, and new techniques established, in epithelial in vitro models capable of expressing squamous characteristics, which will be used to identify hazardous exposures and elucidate the mechanisms by which they induce their effects. A protocol for the quantitative detection of transglutaminase activity has been standardised in keratinocytes, based on the enzymatic incorporation of fluorescein-cadaverine (FC) into bis(gamma-glutamyl) polyamine cross-links. The specificity of this compound as a transglutaminase substrate was demonstrated by using a range of competitive transglutaminase inhibitors, and by modulation of the squamous pathway. FC incorporation was localised to the cell membrane of terminally differentiating cells, and was not visible in basal, proliferating cells. High calcium-containing medium, nicotine and cigarette smoke condensates (CSC) induced an increase in FC incorporation, providing evidence of their role in enhancing the squamous pathway. Analysis by flow cytometry was used to provide a quantitative assessment of a range of optimised squamous differentiation markers, identified in normal human bronchial epithelia and in a bronchial cell line. Transglutaminase I was induced in a time-dependent manner, in post-confluent cells induced to differentiate down the squamous pathway, whereas involucrin was ubiquitously expressed and the levels of cytokeratins 5, 6 and 18 were reduced. The response of these and other differentiation markers to squamous-inducing conditions is being explored.