Higher CCR5 density on CD4 + T-cells in mothers and infants is associated with increased risk of in-utero HIV-1 transmission

OBJECTIVE

CCR5-tropic viruses are preferentially transmitted during perinatal HIV-1 infection. CCR5 density on CD4 + T-cells likely impacts susceptibility to HIV-1 infection.

DESIGN

Fifty-two mother-infant dyads were enrolled. All mothers were living with HIV-1, 27 of the infants acquired HIV-1 in utero and 25 infants remained uninfected.

METHODS

CCR5 density, together with frequencies of CD4 + and CD8 + T-cells expressing immune activation (CCR5, ICOS and HLA-DR) and immune checkpoint (TIGIT and PD-1) markers, were measured in whole blood from the dyads close to delivery.

RESULTS

Compared with mothers who did not transmit, mothers who transmitted HIV-1 had less exposure to ART during pregnancy ( P = 0.015) and higher plasma viral load close to delivery ( P = 0.0005). These mothers, additionally, had higher CCR5 density on CD4 + and CD8 + T-cells and higher frequencies of CCR5, ICOS and TIGIT-expressing CD8 + T-cells. Similarly, compared with infants without HIV-1, infants with HIV-1 had higher CCR5 density on CD4 + and CD8 + T-cells and higher frequencies of CCR5, TIGIT, and PD-1-expressing CD4 + and CD8 + T-cells as well as higher frequencies of HLA-DR-expressing CD8 + T-cells. CCR5 density on maternal CD4 + T-cells remained significantly associated with transmission after adjusting for maternal viral load and CD4 + T cell counts. Mother-infant dyads with shared high CCR5 density phenotypes had the highest risk of transmission/acquisition of infection compared with dyads with shared low-CCR5 density phenotypes.

CONCLUSION

This study provides strong evidence of a protective role for a combined mother-infant low CD4 + T-cell CCR5 density phenotype in in-utero transmission/acquisition of HIV-1.

Extragenital Sexually Transmitted Infections Among High-Risk Men Who Have Sex With Men in Johannesburg, South Africa

BACKGROUND

In South Africa, extragenital etiological sexually transmitted infection (STI) screening among men who have sex with men (MSM) is not routinely available. We aimed to determine the prevalence of STI pathogens at rectal and pharyngeal sites, syphilis seroprevalence, and associated risk factors among a selection of high-risk MSM without symptomatic urethritis attending a men's health clinic in Johannesburg, South Africa.

METHODS

A cross-sectional study was conducted in 2022. Enrolled clients self-reported demographic, sexual behavioral risks, and clinical information. Client or clinician-collected rectal and pharyngeal swabs were tested for Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium, and Trichomonas vaginalis. C. trachomatis-positive rectal samples were reflex tested for lymphogranuloma venereum. Blood specimens were screened for syphilis. Univariate and multivariate regression models were used to determine factors independently associated with the presence of an extragenital STI or syphilis.

RESULTS

Among the 97 participants (median age, 29 years), 24.7% had an extragenital STI and 9.4% had high nontreponemal antibody titers (rapid plasma reagin ≥1:16). Rectal STIs were detected in 26.4% participants: N. gonorrhoeae (14.3%), C. trachomatis (9.9%), and M. genitalium (5.5%). Pharyngeal STIs were less prevalent (4.1%). Overall, the prevalence of any STI was 41%. Sex under the influence of drugs (adjusted odds ratio, 4.94; 95% confidence interval, 1.56-15.69) and engaging in condomless receptive anal intercourse with a casual partner (adjusted odds ratio, 8.36; 95% confidence interval, 1.73-40.28) were independent risk factors for having an extragenital STI.

CONCLUSIONS

The high burden of extragenital STIs and active syphilis in asymptomatic MSM underscores the importance of routine etiological screening in this key population, as the syndromic approach would not enable detection or treatment of these infections.

Emergence of high-level azithromycin-resistant Neisseria gonorrhoeae causing male urethritis in Johannesburg, South Africa, 2021

BACKGROUND

In South Africa, Neisseria gonorrhoeae , which is the predominant cause of male urethritis, is treated syndromically using dual ceftriaxone and azithromycin therapy. We determined antimicrobial susceptibilities of N. gonorrhoeae isolates from urethral discharge specimens, and genetically characterised those with elevated minimum inhibitory concentrations (MICs) for first-line antimicrobials.

METHODS

Routine antimicrobial susceptibility testing (AST) of N. gonorrhoeae isolates included E-test for ceftriaxone, cefixime and gentamicin and agar dilution for azithromycin and spectinomycin. Neisseria gonorrhoeae Sequence Typing for Antimicrobial Resistance (NG-STAR) was performed for isolates with elevated MICs to identify antimicrobial resistance (AMR) determinants, and Neisseria gonorrhoeae Multi-Antigen Sequence Typing (NG-MAST) was used to determine strain relatedness.

RESULTS

N. gonorrhoeae was cultured from urethral discharge swab specimens obtained from 196 of 238 (82.4%) men presenting to a primary healthcare facility in Johannesburg in 2021. All viable isolates were susceptible to extended-spectrum cephalosporins. Four isolates had high azithromycin MICs ranging from 32mg/L to >256mg/L and grouped into two novel NG-MAST and NG-STAR groups. Two isolates from Group 1 (NG-MAST ST20366, NG-STAR ST4322) contained mutated mtrR (G45D) and 23S rRNA (A2059G) alleles, while the two isolates from Group 2 (NG-MAST ST20367, NG-STAR ST4323) had different mutations in mtrR (A39T) and 23S rRNA (C2611T).

CONCLUSIONS

We report the first cases of high-level azithromycin resistance in N. gonorrhoeae from South Africa. Continued AMR surveillance is critical to detect increasing azithromycin resistance prevalence in N. gonorrhoeae , which may justify future modifications to the STI syndromic management guidelines.

The evaluation of the Allplex™ BV molecular assay for the diagnosis of bacterial vaginosis in symptomatic South African females

Bacterial vaginosis (BV) is a dysbiosis of vaginal microbiota characterized by a shift from Lactobacillus species predomination to a heterogeneous mixture of anaerobes. We compared the performance characteristics of the Allplex ™ BV molecular assay with the reference test, Nugent score microscopy, for vaginal swab specimens from symptomatic South African women. A total of 213 patients were enrolled, of whom 99 (46.5%) and 132 (62.0%) were diagnosed with BV by Nugent and Allplex™, respectively. The Allplex™ BV assay displayed a sensitivity of 94.9% (95% CI, 88.7%-97.8%) and a specificity of 66.7% (95% CI, 57.6%-74.6%), with an agreement of 79.8% (95% CI, 73.9%-84.7%) (κ = 0.60). Assay design may be enhanced for improved specificity by accounting for differences in healthy and BV-associated vaginal microbiomes among women of different ethnicities.

Etiological Surveillance of Vaginal Discharge Syndrome in South Africa: 2019 to 2020

BACKGROUND

The syndromic management of vaginal discharge syndrome (VDS) is challenging because of the prevalence of mixed infection with sexually transmitted infection (STI) pathogens and non-STI causes, such as bacterial vaginosis and candidiasis (CA). We aimed to determine the relative prevalence of VDS etiologies in women presenting to sentinel primary health care clinics in South Africa. Secondary objectives were to ascertain the predictive value of speculum findings for the presence of STI pathogens and the proportion of women presenting with clinical features of CA who had identifiable yeast on vaginal smear microscopy.

METHODS

Consecutive, consenting women with complaints of abnormal vaginal discharge were enrolled between January 1, 2019, and December 31, 2020. Genital discharge swab and blood specimens were collected and transported to a central STI reference laboratory in Johannesburg.

RESULTS

A total of 364 women were enrolled at 3 sentinel sites. Bacterial vaginosis was the most common cause of VDS (163 of 361 [45.2%]; 95% confidence interval [CI], 40.1%-50.3%); however, a significant proportion had STI coinfection (71 of 163 [43.6%]; 95% CI, 35.8%-51.5%). The predominant STI etiology was Chlamydia trachomatis (73 [20.2%]; 95% CI, 16.4%-24.7%). An abnormal speculum finding had poor predictive value for STIs, and Gram stain microscopy showed yeast in only 37.2% of vaginal smears from women with CA symptoms.

CONCLUSIONS

Bacterial vaginosis is the predominant cause of VDS in South Africa; however, STI coinfection is common. Clinical findings are poorly predictive of STI etiologies or candidiasis; therefore, a rapid and accurate STI point-of-care test would be useful in optimizing VDS management.

Molecular Characterization and Detection of Macrolide and Fluoroquinolone Resistance Determinants in Mycoplasma genitalium in South Africa, 2015 to 2018

BACKGROUND

Antimicrobial resistance in Mycoplasma genitalium is a global concern, as therapeutic options are limited. We aimed to determine the prevalence of macrolide and fluoroquinolone resistance-associated genetic determinants and strain diversity in M. genitalium-positive surveillance specimens from symptomatic primary health care center attendees in South Africa (2015-2018). A secondary objective was to investigate for an association between M. genitalium strain type, HIV serostatus, and antimicrobial resistance.

METHODS

A total of 196 M. genitalium-positive specimens from adult males and females presenting with genital discharge to primary health care centers were tested for resistance-associated mutations in 23S rRNA, parC and gyrA. A dual-locus sequence type (DLST) was assigned to M. genitalium strains based on the detection of single nucleotide polymorphisms in the semiconserved 5' region of the mgpB gene (MG191-sequence typing) as well as the enumeration of short tandem repeats within the lipoprotein gene (MG309 short tandem repeat typing).

RESULTS

The A2059G mutation in 23S rRNA, associated with macrolide resistance, was detected in 3 of 182 specimens (1.7%; 95% confidence interval, 0.3-4.7). We did not detect gyrA or parC mutations associated with fluoroquinolone resistance in specimens that could be sequenced. Molecular typing with DLST revealed genetic heterogeneity, with DLST 4-11 being the most common M. genitalium strain type detected. There were no associations between DLST and macrolide resistance or HIV infection.

CONCLUSIONS

We found a low prevalence of M. genitalium strains with macrolide resistance-associated mutations over a 4-year surveillance period. Ongoing antimicrobial resistance surveillance is essential for informing genital discharge syndromic treatment guidelines.

Predictors of cell-associated HIV-1 DNA over one year in very early treated infants

BACKGROUND

Younger age of antiretroviral therapy (ART) initiation is associated with a smaller viral reservoir size in perinatally-acquired HIV-1 infection, but there is wide variability among early-treated infants. Predictors of this variability are not fully described.

METHODS

Sixty-three neonates diagnosed with HIV-1 <48 hours after birth in Johannesburg, South Africa were started on ART as soon as possible. Fifty-nine (94%) infants received daily nevirapine prophylaxis from birth until ART start. Viably-preserved peripheral blood mononuclear cells (PBMC) collected at regular intervals to 48 weeks, and from respective mothers at enrolment, were tested using integrase-targeted, semi-nested, real-time quantitative hydrolysis probe (TaqMan) PCR assays to quantify total HIV-1 subtype C viral DNA (vDNA). Predictors were investigated using Generalized Estimating Equation (GEE) regression models.

RESULTS

Thirty-one (49.2%) infants initiated ART <48 hours, 24 (38.1%) <14 days and 8 (12.7%) >14 days of birth. Three-quarters were infected despite maternal antenatal ART (however, only 9.5% of women had undetectable viral load closest to delivery) and 86% were breastfed. Higher infant CD4+ T-cell percentage and viral load <100,000 copies/ml pre-ART were associated with lower levels of vDNA copies/10 6 PBMC equivalents in the first 48 weeks after ART start. No antenatal maternal ART and breastfeeding were also associated with lower vDNA. Older age at ART initiation had a discernible negative impact when initiated >14 days.

CONCLUSIONS

Among very early treated infants, higher CD4+ T-cell percentage and viral load <100,000 copies/ml pre-ART, infection occurring in the absence of maternal antenatal ART and breastfeeding were associated with lower levels of HIV-1 DNA in the first 48 weeks of treatment.

Normalization of B Cell Subsets but Not T Follicular Helper Phenotypes in Infants With Very Early Antiretroviral Treatment

Introduction: Infant HIV-1-infection is associated with high morbidity and mortality if antiretroviral treatment (ART) is not initiated promptly. We characterized development of circulating T follicular helper cells (cTfh) and their relationship to naïve/memory B cell subsets in a cohort of neonates initiating ART within the first week of life. Methods: Infants were diagnosed within 48 hours of birth and started ART as soon as possible. The frequency and phenotype of cTfh and B cells were analyzed at enrollment (birth -19 days) and at 4, 12, and 72 weeks of age in blood of 27 HIV-1-intrauterine-infected and 25 HIV-1 exposed uninfected (HEU) infants as part of a study in Johannesburg, South Africa. cTfh cells were divided into Tfh1, Tfh2, and Tfh17 subsets. B cell phenotypes were defined as naïve, resting memory, activated memory and tissue-like memory cells. Results: HIV-1-infected infants had higher frequencies of cTfh cells than HEU infants up to 12 weeks of age and these cTfh cells were polarized toward the Tfh1 subset. Higher frequencies of Tfh1 and lower frequencies of Tfh2 and Tfh17 correlated with lower CD4+ T cell percentages. Lower frequencies of resting memory, with corresponding higher frequencies of activated memory B cells, were observed with HIV-1 infection. Importantly, dysregulations in B cell, but not cTfh cell, subsets were normalized by 72 weeks. Conclusion: Very early ART initiation in HIV-1-infected infants normalizes B cell subsets but does not fully normalize perturbations in cTfh cell subsets which remain Tfh1 polarized at 72 weeks. It remains to be determined if very early ART improves vaccine antibody responses despite the cTfh and B cell perturbations observed over the time course of this study.

Lack of association of KIR2DL1-R245 and KIR2DL1-C245 with HIV-1 control in black South Africans with HLA-C2

Activating/inhibitory Killer-cell Immunoglobulin-like Receptors (KIRs) partly regulate Natural Killer (NK) cells. KIR2DL1 allotypes with cysteine at position-245 (KIR2DL1-C²⁴⁵) express at lower levels and demonstrate weaker inhibitory signaling compared to allotypes with arginine at position-245 (KIR2DL1-R²⁴⁵). The functional consequence of either allotype in infectious diseases is unknown. Since NK cells mediate antiviral immunity, we investigated KIR2DL1-R²⁴⁵ and KIR2DL1-C²⁴⁵ in association with HIV-1 virological control in untreated immunocompetent black South Africans. Allotype carriage, determined by KIR2DL1 sequencing, was similar between uninfected South Africans (n = 104) and other black African populations, but differed significantly from Europeans, while no significant differences were noted between uninfected and HIV-1-infected individuals (n = 52). KIR2DL1 expression, measured by flow cytometry, in uninfected individuals showed higher KIR2DL1-R²⁴⁵ expression compared to KIR2DL1-C²⁴⁵ in white donors (n = 27), while black donors (n = 21) generally expressed lower levels of both allotypes. KIR2DL1 expression was reduced in HLA-C2 carriers, most evident in black HLA-C2/C2 donors. KIR2DL1-R²⁴⁵ and KIR2DL1-C²⁴⁵ did not associate with viral load when HLA-C2 ligands were present, however in HLA-C1 homozygotes, individuals with only KIR2DL1-R²⁴⁵, showed lower viral loads compared to carriers of both allotypes. The lack of association of KIR2DL1-R²⁴⁵ or KIR2DL1-C²⁴⁵ with HIV-1 control in HLA-C2 carriers may relate to lower KIR2DL1 expression levels in a population with high HLA-C2 prevalence.

The impact of bone marrow stromal antigen-2 (BST2) gene variants on HIV-1 control in black South African individuals

Bone marrow stromal cell antigen 2 (BST2 or tetherin) is a host-encoded, interferon-inducible antiviral restriction factor which blocks the release of enveloped viruses. Few studies have assessed the role of BST2 polymorphisms on HIV-1 acquisition or disease progression in sub-Saharan Africa. This study investigated the frequency of four HIV-1-associated BST2 variants rs3217318, rs12609479, rs10415893 and rs113189798 in uninfected and HIV-1 infected black South Africans. Homozygosity for the rs12609479-A minor allele, previously associated with decreased HIV-1 acquisition risk, was underrepresented in HIV-1 uninfected black South Africans (2%) compared to reference African (9%) and in particular European populations (61%) (p = .047 and p < .0001, respectively). To determine if any of these gene variants influenced HIV-1 control in the absence of antiretroviral treatment (ART), we compared HIV-1 infected ART-naïve progressors [n = 72] and controllers [n = 71], the latter includes elite controllers [EC: n = 23; VL < 50 RNA copies/ml]. Heterozygosity for the rs12609479 SNP (G/A) was enriched in progressors compared to ECs (47.2% vs 21.7%, OR = 3.50 [1.16-10.59], p = .03), while rs113189798 heterozygosity (A/G) showed a strong trend of overrepresentation in ECs compared to progressors (47.8% vs 26.4%, OR = 0.39 [0.14-1.04], p = .07). Heterozygosity for the promoter indel rs3217318 (i19/Δ19) was associated with a faster rate of CD4⁺ T-cell decline in progressors (p = .0134). Carriage of the rs3217318 (i19/Δ19), rs12609479 (G/G), rs10415893(G/A) and rs113189798 (A/G) combined genotype, denoted as i19Δ19 GG GA AG, was associated with significantly higher CD4⁺ T-cell counts in progressors (p = .03), a finding predominantly driven by the _GG_AG combination. Our data suggest that the possession of select BST2 genotype combinations may be implicated in HIV-1 disease progression and natural spontaneous control.

Chronic HIV-1 Infection Alters the Cellular Distribution of FcγRIIIa and the Functional Consequence of the FcγRIIIa-F158V Variant

Chronic HIV-infection modulates the expression of Fc gamma receptors (FcγRs) on immune cells and their antibody-dependent effector function capability. Given the increasingly recognized importance of antibody-dependent cellular cytotoxicity (ADCC) in HIV-specific immunity, we investigated the cellular distribution of FcγRIIIa on cytotoxic lymphocytes—natural killer cells and CD8⁺ T cells—and the effect of the FcγRIIIa-F158V variant on ADCC capacity in HIV-infected individuals (n = 23) and healthy controls (n = 23). Study participants were matched for F158V genotypes, carried two copies of the FCGR3A gene and were negative for FcγRIIb expression on NK cells. The distribution of CD56^dimFcγRIIIa^bright and CD56^negFcγRIIIa^bright NK cell subsets, but not FcγRIIIa surface expression, differed significantly between HIV-1 negative and HIV-1 positive donors. NK cell-mediated ADCC responses negatively correlated with the proportion of the immunoregulatory CD56^brightFcγRIIIa^dim/neg cells and were lower in the HIV-1 positive group. Intriguingly, the FcγRIIIa-F158V variant differentially affected the NK-mediated ADCC responses for HIV-1 negative and HIV-1 positive donors. Healthy donors bearing at least one 158V allele had higher ADCC responses compared to those homozygous for the 158F allele (48.1 vs. 34.1%), whereas the opposite was observed for the HIV-infected group (26.4 vs. 34.6%), although not statistically significantly different. Furthermore, FcγRIIIa⁺CD8^bright and FcγRIIIa⁺CD8^dim T cell subsets were observed in both HIV-1 negative and HIV-1 positive donors, with median proportions that were significantly higher in HIV-1 positive donors compared to healthy controls (15.7 vs. 8.3%; P = 0.016 and 18.2 vs. 14.1%; P = 0.038, respectively). Using an HIV-1-specific GranToxiLux assay, we demonstrate that CD8⁺ T cells mediate ADCC through the delivery of granzyme B, which was overall lower compared to that of autologous NK cells. In conclusion, our findings demonstrate that in the presence of an HIV-1 infection, the cellular distribution of FcγRIIIa is altered and that the functional consequence of FcγRIIIa variant is affected. Importantly, it underscores the need to characterize FcγR expression, cellular distribution and functional consequences of FcγR genetic variants within a specific environment or disease state.

Age at antiretroviral therapy initiation and cell-associated HIV-1 DNA levels in HIV-1-infected children

Background

The latent viral reservoir is the major obstacle to achieving HIV remission and necessitates life-long antiretroviral therapy (ART) for HIV-infected individuals. Studies in adults and children have found that initiating ART soon after infection is associated with a reduction in the size of the HIV-1 reservoir. Here we quantified cell-associated HIV-1 DNA in early-treated but currently older HIV-infected children suppressed on ART.

Methods

The study participants comprised of a cohort of 146 early-treated children with HIV-1 RNA <50 copies/ml enrolled as part of a clinical trial in Johannesburg, South Africa. A stored buffy coat sample collected after a median 4.3 years on ART and where HIV-1 RNA was <50 copies/ml was tested for cell-associated HIV-1 DNA levels. An in-house, semi-nested real-time quantitative hydrolysis probe PCR assay to detect total HIV-1 subtype C proviral DNA was used. Children were followed prospectively for up to 3 years after this measurement to investigate subsequent HIV-1 RNA rebound/failure while remaining on ART. Age at ART initiation, HIV-1 RNA decline prior to HIV-1 DNA measurement and other factors were investigated.

Results

A gradient between age at ART initiation and later HIV-1 DNA levels was observed. When ART was started <2 months of age, the lowest levels of cell-associated HIV-1 DNA (median 1.4 log₁₀copies/10⁶ cells, interquartile range [IQR] 0.95–1.55) were observed compared to ART started at 2–4 months (median 1.68, IQR 1.26–1.97) or 5–14 months of age (median1.98, IQR 1.69–2.25). A low CD4 T-cell count pre-treatment predicted higher levels of HIV-1 DNA on later testing. The probability of HIV-1 RNA rebound >50 copies/ml whilst on ART within 3 years after the DNA measurement was 2.07 (95% CI: 1.352–3.167) times greater if the HIV-1 DNA level was above the median of 55 copies/10⁶ cells.

Conclusions

Cell-associated HIV-1 DNA levels measured after more than 4 years on ART were lower the younger the age of the child when ART was initiated. This marker of the size of the viral reservoir also predicted subsequent viral rebound/treatment failure while ART was sustained. The results provide additional evidence of the benefits of prompt diagnosis and early ART initiation in newborns and infants.

LRP/LR Antibody Mediated Rescuing of Amyloid-β-Induced Cytotoxicity is Dependent on PrPc in Alzheimer's Disease

The neuronal perturbations in Alzheimer's disease are attributed to the formation of extracellular amyloid-β (Aβ) neuritic plaques, composed predominantly of the neurotoxic Aβ42 isoform. Although the plaques have demonstrated a role in synaptic dysfunction, neuronal cytotoxicity has been attributed to soluble Aβ42 oligomers. The 37kDa/67kDa laminin receptor has been implicated in Aβ42 shedding and Aβ42-induced neuronal cytotoxicity, as well as internalization of this neurotoxic peptide. As the cellular prion protein binds to both LRP/LR and Aβ42, the mechanism underlying this cytotoxicity may be indirectly due to the PrPc-Aβ42 interaction with LRP/LR. The effects of this interaction were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assays. PrPc overexpression significantly enhanced Aβ42 cytotoxicity in vitro, while PrP-/-  cells were more resistant to the cytotoxic effects of Aβ42 and exhibited significantly less cell death than PrPc expressing N2a cells. Although anti-LRP/LR specific antibody IgG1-iS18 significantly enhanced cell viability in both pSFV1-huPrP1-253 transfected and non-transfected cells treated with exogenous Aβ42, it failed to have any cell rescuing effect in PrP-/-  HpL3-4 cells. These results suggest that LRP/LR plays a significant role in Aβ42-PrPc mediated cytotoxicity and that anti-LRP/LR specific antibodies may serve as potential therapeutic tools for Alzheimer's disease.

Novel patented therapeutic approaches targeting the 37/67 kDa laminin receptor for treatment of cancer and Alzheimer's disease

INTRODUCTION

The 37/67 kDa high-affinity laminin receptor (laminin receptor precursor/laminin receptor, LRP/LR) is a multi-faceted cellular receptor. It plays a vital role in the malignancy of various cancer types where it is seen to contribute to invasion, adhesion, apoptosis evasion and angiogenesis. Furthermore, it has been found to play an important role in facilitating the processes leading to neurotoxicity in Alzheimer's disease (AD). Various therapeutic options targeting this receptor have been patented with the outlook on application for the treatment/prevention of these diseases.

AREAS COVERED

The various roles that LRP/LR plays in cancer, AD and infectious diseases caused by viruses and bacteria have been examined in detail and an overview of the current patented therapeutic strategies targeting this receptor is given.

EXPERT OPINION

Molecular tools directed against LRP/LR, such as antibodies and small interfering RNA, could prove to be effective in the prevention of metastasis and angiogenesis while inducing apoptosis in cancers. Moreover, these strategies could also be applied to AD where LRP/LR is seen to facilitate the production and internalization of the neurotoxic Aβ peptide. This review provides a comprehensive overview of the mechanisms by which LRP/LR is involved in eliciting pathogenic events, while showing how the use of patented approaches targeting this receptor could be used to treat them.

Anti-LRP/LR specific antibody IgG1-iS18 and knock-down of LRP/LR by shRNAs rescue cells from Aβ42 induced cytotoxicity

Alzheimer's disease (AD) is characterized by neurofibrillary tangles, senile plaques and neuronal loss. Amyloid beta (Aβ) is proposed to elicit neuronal loss through cell surface receptors. As Aβ shares common binding partners with the 37 kDa/67 kDa laminin receptor (LRP/LR), we investigated whether these proteins interact and the pathological significance of this association. An LRP/LR-Αβ₄₂ interaction was assessed by immunofluorescence microscopy and pull down assays. The cell biological effects were investigated by 3-(4,5-Dimethylthaizol-2-yl)-2,5-diphenyltetrazolium bromide and Bromodeoxyuridine assays. LRP/LR and Αβ₄₂ co-localised on the cell surface and formed immobilized complexes suggesting an interaction. Antibody blockade by IgG1-iS18 and shRNA mediated down regulation of LRP/LR significantly enhanced cell viability and proliferation in cells co-treated with Αβ₄₂ when compared to cells incubated with Αβ₄₂ only. Results suggest that LRP/LR is implicated in Αβ₄₂ mediated cytotoxicity and that anti-LRP/LR specific antibodies and shRNAs may serve as potential therapeutic tools for AD.

Anti-LRP/LR specific antibody IgG1-iS18 impedes adhesion and invasion of liver cancer cells

Two key events, namely adhesion and invasion, are pivotal to the occurrence of metastasis. Importantly, the 37 kDa/67 kDa laminin receptor (LRP/LR) has been implicated in enhancing these two events thus facilitating cancer progression. In the current study, the role of LRP/LR in the adhesion and invasion of liver cancer (HUH-7) and leukaemia (K562) cells was investigated. Flow cytometry revealed that the HUH-7 cells displayed significantly higher cell surface LRP/LR levels compared to the poorly-invasive breast cancer (MCF-7) control cells, whilst the K562 cells displayed significantly lower cell surface LRP/LR levels in comparison to the MCF-7 control cells. However, Western blotting and densitometric analysis revealed that all three tumorigenic cell lines did not differ significantly with regards to total LRP/LR levels. Furthermore, treatment of liver cancer cells with anti-LRP/LR specific antibody IgG1-iS18 (0.2 mg/ml) significantly reduced the adhesive potential of cells to laminin-1 and the invasive potential of cells through the ECM-like Matrigel, whilst leukaemia cells showed no significant differences in both instances. Additionally, Pearson's correlation coefficients suggested direct proportionality between cell surface LRP/LR levels and the adhesive and invasive potential of liver cancer and leukaemia cells. These findings suggest the potential use of anti-LRP/LR specific antibody IgG1-iS18 as an alternative therapeutic tool for metastatic liver cancer through impediment of the LRP/LR- laminin-1 interaction.

In vitro inhibition of angiogenesis by antibodies directed against the 37kDa/67kDa laminin receptor

The 37kDa/67kDa laminin receptor (LRP/LR) is a central receptor mediating interactions between tumour cells and the basement membrane and is thereby a key player in adhesion and invasion, essential processes in metastatic cancer. To affect continued tumour growth, tumours induce angiogenesis for the constant delivery of nutrients and oxygen. This study aims to determine the blocking effect of the anti-LRP/LR specific antibody, W3 on the angiogenic potential of HUVE (human umbilical vein endothelial) cells. Flow cytometric analysis revealed that 97% of HUVE cells display cell surface LRP/LR. An angiogenesis assay was conducted employing HUVE cells seeded on the basement membrane reconstituent Matrigel™ supplemented with the pro-angiogenic factor vascular endothelial growth factor (VEGF). Post 18h incubation at 37°C tubular structures, namely tube lengths were assessed. Treatment of established tubular structures with 100 µg/ml anti-LRP/LR specific antibody completely blocked angiogenesis. Our findings suggest a central role of the 37kDa/67kDa LRP/LR in tube formation and recommends anti-LRP/LR specific antibodies as potential therapeutic tools for treatment of tumour angiogenesis.

Global Alzheimer Research Summit: basic and clinical research: present and future Alzheimer research

We report here on the proceedings of the Global Alzheimer Summit that took place September 22-23, 2011 in Madrid, Spain. As Alzheimer disease (AD) is the leading cause of neurodegeneration in elderly individuals and as yet has no effective therapeutic option, it continues to stimulate global research interests. At the conference, leaders in the field of AD research provided insights into current developments in various areas of research, namely molecular mechanisms, genetics, novel aspects of AD research and translational research. Emphasis was also placed on the importance of biomarkers in the diagnosis of AD and development of current therapeutic strategies.

Structural and mechanistic commonalities of amyloid-β and the prion protein

Amyloid β (Aβ) is a major causative agent of Alzheime disease. This neurotoxic peptide is generated as a result of the cleavage of the Amyloid-Precursor-Protein (APP) by the action of beta secretase and gamma secretase. The neurotoxicity was previously thought to be the result of aggregation. However, recent studies suggest that the interaction of Aβ with numerous cell surface receptors such as N-methyl-D-aspartate (NMDA), receptor for advanced glycosylation end products (RAGE), P75 neurotrophin receptor (P75NTR) as well as cell surface proteins such as the cellular prion protein (PrP(c) ) and heparan sulfate proteoglycans (HSPG) strongly enhances Aβ induced apoptosis and thereby contributes to neurotoxicity. This review focuses on the molecular mechanism resulting in Aβ-shedding as well as Aβ-induced apoptotic processes, genetic risk factors for familial Alzheimer disease and interactions of Aβ with cell surface receptors and proteins, with particular emphasis on the cellular prion protein. Furthermore, comparisons are drawn between Alzheimer disease and prion disorders and the role of laminin, an extracellular matrix protein, glycosaminoglycans and the 37 kDa/67 kDa laminin receptor (LRP/LR) have been highlighted with regards to both neurodegenerative diseases.

Alimentary prion infections: Touchdown in the intestine

Neurodegenerative diseases are caused by proteinaceous aggregates, usually consisting of misfolded proteins which are often typified by a high proportion of β-sheets, which accumulate in the Central Nervous System. These diseases, including Morbus Alzheimer, Parkinson disease and Transmissible Spongiform Encephalopathies (TSEs)--also termed prion disorders--afflict a substantial proportion of the human population and as such the etiology and pathogenesis of these diseases has been the focus of mounting research. Although many of these diseases arise from genetic mutations or are sporadic in nature, the possible horizontal transmissibility of neurodegenerative diseases poses a great threat to population health. In this article we discuss recent studies which suggest that the "non-transmissible" status bestowed upon Alzheimer and Parkinson diseases may need to be revised as these diseases have been successfully induced through tissue transplants. Furthermore, we highlight the importance of investigating the "natural" mechanism of prion transmission including peroral and perenteral transmission, proposed routes of gastrointestinal uptake and neuroinvasion of ingested infectious prion proteins. We examine the multitude of factors which may influence oral transmissibility and discuss the zoonotic threats which Chronic Wasting Disease (CWD), Bovine Spongiform Encephalopathy (BSE) and Scrapie may pose resulting in vCJD or related disorders. In addition, we suggest that the 37 kDa/67 kDa laminin receptor on the cell surface of enterocytes, a major cell population in the intestine, may play an important role in the intestinal pathophysiology of alimentary prion infections.

Prion interaction with the 37-kDa/67-kDa laminin receptor on enterocytes as a cellular model for intestinal uptake of prions

Enterocytes, a major cell population of the intestinal epithelium, represent one possible barrier to the entry of prions after oral exposure. We established a cell culture system employing enterocytes from different species to study alimentary prion interaction with the 37-kDa/67-kDa laminin receptor LRP/LR. Human, bovine, porcine, ovine, and cervid enterocytes were cocultured with brain homogenates from cervid, sheep, and cattle suffering from chronic wasting disease (CWD), scrapie, and bovine spongiform encephalopathy (BSE), respectively. PrP(CWD), ovine PrP(Sc), and PrP(BSE) all colocalized with LRP/LR on human enterocytes. PrP(CWD) failed to colocalize with LRP/LR on bovine, porcine, and ovine enterocytes. Ovine PrP(Sc) colocalized with the receptor on bovine enterocytes, but failed to colocalize with LRP/LR on cervid and porcine enterocytes. PrP(BSE) failed to colocalize with the receptor on cervid and ovine enterocytes. These data suggest possible oral transmissibility of CWD and sheep scrapie to humans and may confirm the oral transmissibility of BSE to humans, resulting in zoonotic variant Creutzfeldt-Jakob disease. CWD might not be transmissible to cattle, pigs, and sheep. Sheep scrapie might have caused BSE, but may not cause transmissible spongiform encephalopathy in cervids and pigs. BSE may not be transmissible to cervids. Our data recommend the enterocyte model system for further investigations of the intestinal pathophysiology of alimentary prion infections.