Intracellular detection of differential APOBEC3G, TRIM5alpha, and LEDGF/p75 protein expression in peripheral blood by flow cytometry

Metastatic and non-metastatic melanoma imaging using Sgc8-c aptamer PTK7-recognizer

Melanoma is one of the most aggressive and deadly skin cancers, and although histopathological criteria are used for its prognosis, biomarkers are necessary to identify the different evolution stages. The applications of molecular imaging include the in vivo diagnosis of cancer with probes that recognize the tumor-biomarkers specific expression allowing external image acquisitions and evaluation of the biological process in quali-quantitative ways. Aptamers are oligonucleotides that recognize targets with high affinity and specificity presenting advantages that make them interesting molecular imaging probes. Sgc8-c (DNA-aptamer) selectively recognizes PTK7-receptor overexpressed in various types of tumors. Herein, Sgc8-c was evaluated, for the first time, in a metastatic melanoma model as molecular imaging probe for in vivo diagnostic, as well as in a non-metastatic melanoma model. Firstly, two probes, radio- and fluorescent-probe, were in vitro evaluated verifying the high specific PTK7 recognition and its internalization in tumor cells by the endosomal route. Secondly, in vivo proof of concept was performed in animal tumor models. In addition, they have rapid clearance from blood exhibiting excellent target (tumor)/non-target organ ratios. Furthermore, optimal biodistribution was observed 24 h after probes injections accumulating almost exclusively in the tumor tissue. Sgc8-c is a potential tool for their specific use in the early detection of melanoma.

Development of new PTK7-targeting aptamer-fluorescent and -radiolabelled probes for evaluation as molecular imaging agents: Lymphoma and melanoma in vivo proof of concept

Aptamers are single-stranded oligonucleotides that recognize molecular targets with high affinity and specificity. Aptamer that selectively bind to the protein tyrosine kinase-7 (PTK7) receptor, overexpressed on many cancers, has been labelled as probes for molecular imaging of cancer. Two new PTK7-targeting aptamer probes were developed by coupling frameworks from the fluorescent dye AlexaFluor647 or the 6-hydrazinonicotinamide (HYNIC) chelator-labelled to ^99mTc. The derivatizations via a 5'-aminohexyl terminal linker were done at room temperature and under mild buffer conditions. Physicochemical and biological controls for both imaging agents were performed verifying the integrity of the aptamer-conjugates by HPLC. Recognition of melanoma (B16F1) and lymphoma (A20) mouse cell lines by the aptamer was studied using cell binding, flow cytometry and confocal microscopy. Finally, in vivo imaging studies in tumour-bearing mice were performed. The new probes were able to bind to melanoma and lymphoma cell lines in vitro, the in vivo imaging in tumour-bearing mice showed different uptake behaviours showing for the fluorescent conjugate good uptake by B cell lymphoma while the radiolabelled conjugate did not display tumour uptake due to its high extravascular distribution, and both showed rapid clearance properties in tumour-bearing mice.

Role of RNA secondary structure in emergence of compartment specific hepatitis B virus immune escape variants

AIM

To investigate the role of subgenotype specific RNA secondary structure in the compartment specific selection of hepatitis B virus (HBV) immune escape mutations.

METHODS

This study was based on the analysis of the specific observation of HBV subgenotype A1 in the serum/plasma, while subgenotype A2 with G145R mutation in the peripheral blood leukocytes (PBLs). Genetic variability found among the two subgenotypes was used for prediction and comparison of the full length pregenomic RNA (pgRNA) secondary structure and base pairings. RNA secondary structures were predicted for 37 °C using the Vienna RNA fold server, using default parameters. Visualization and detailed analysis was done using RNA shapes program.

RESULTS

In this analysis, using similar algorithm and conditions, entirely different pgRNA secondary structures for subgenotype A1 and subgenotype A2 were predicted, suggesting different base pairing patterns within the two subgenotypes of genotype A, specifically, in the HBV genetic region encoding the major hydrophilic loop. We observed that for subgenotype A1 specific pgRNA, nucleotide 358^U base paired with 1738^A and nucleotide 587^G base paired with 607^C. However in sharp contrast, in subgenotype A2 specific pgRNA, nucleotide 358^U was opposite to nucleotide 588^G, while 587^G was opposite to 359^U, hence precluding correct base pairing and thereby lesser stability of the stem structure. When the nucleotides at 358^U and 587^G were replaced with 358^C and 587^A respectively (as observed specifically in the PBL associated A2 sequences), these nucleotides base paired correctly with 588^G and 359^U, respectively.

CONCLUSION

The results of this study show that compartment specific mutations are associated with HBV subgenotype specific alterations in base pairing of the pgRNA, leading to compartment specific selection and preponderance of specific HBV subgenotype with unique mutational pattern.

MicroRNA 142-3p attenuates spread of replicating retroviral vector in hematopoietic lineage-derived cells while maintaining an antiviral immune response

We are developing a retroviral replicating vector (RRV) encoding cytosine deaminase as an anticancer agent for gliomas. Despite its demonstrated natural selectivity for tumors, and other safety features, such a virus could potentially cause off-target effects by productively infecting healthy tissues. Here, we investigated whether incorporation of a hematopoietic lineage-specific microRNA target sequence in RRV further restricts replication in hematopoietic lineage-derived human cells in vitro and in murine lymphoid tissues in vivo. One or four copies of a sequence perfectly complementary to the guide strand of microRNA 142-3p were inserted into the 3' untranslated region of the RRV genome expressing the transgene encoding green fluorescent protein (GFP). Viral spread and GFP expression of these vectors in hematopoietic lineage cells in vitro and in vivo were measured by qPCR, qRT-PCR, and flow cytometry. In hematopoietic lineage-derived human cell lines and primary human stimulated peripheral blood mononuclear cells, vectors carrying the 142-3pT sequence showed a remarkable decrease in GFP expression relative to the parental vector, and viral spread was not observed over time. In a syngeneic subcutaneous mouse tumor model, RRVs with and without the 142-3pT sequences spread equally well in tumor cells; were strongly repressed in blood, bone marrow, and spleen; and generated antiviral immune responses. In an immune-deficient mouse model, RRVs with 142-3pT sequences were strongly repressed in blood, bone marrow, and spleen compared with unmodified RRV. Tissue-specific microRNA-based selective attenuation of RRV replication can maintain antiviral immunity, and if needed, provide an additional safeguard to this delivery platform for gene therapy applications.

Expression levels of the innate response gene RIG-I and its regulators RNF125 and TRIM25 in HIV-1-infected adult and pediatric individuals

OBJECTIVE

TLRs (Toll-like receptors) and RLRs (RIG-I-like receptors) mediate innate immune responses by detecting microorganism invasion. RIG-I activation results in the production of interferon (IFN) type 1 and IFN responsive genes (ISGs). As the ubiquitin ligases RNF125 and TRIM25 are involved in regulating RIG-I function, our aim was to assess whether the levels of these three genes vary between healthy and HIV-infected individuals and whether these levels are related to disease progression.

DESIGN

Gene expression analyses for RIG-I, RNF125, and TRIM25 were performed for HIV-infected adults and the children's peripheral blood mononuclear cells (PBMCs).

METHODS

Reverse transcription-quantitative PCRs (RT-qPCRs) were performed in order to quantify the expression levels of RIG-I, RNF125 and TRIM25 from PBMCs purified from control or HIV-infected individuals.

RESULTS

Controls express higher levels of the three genes when compared to HIV-infected patients. These expressions are clearly distinct between healthy and progressors, and are reproduced in adults and children. In controls, RNF125 is the highest expressed gene, whereas in progressors, RIG-I is either the highest expressed gene or is expressed similarly to RNF125 and TRIM25.

CONCLUSION

A pattern of expression of RIG-I, RNF125, and TRIM25 genes in HIV patients is evident. The high expression of RNF125 in healthy individuals reflects the importance of keeping RIG-I function off, inhibiting unnecessary IFN production. Consistent with this assumption, RNF125 levels are lower in HIV patients and importantly, the RNF125/RIG-I ratio is lower in patients who progress to AIDS. Our results might help to predict disease progression and unveil the role of poorly characterized host genes during HIV infection.

Detection of intracellular Factor VIII protein in peripheral blood mononuclear cells by flow cytometry

Flow cytometry is widely used in cancer research for diagnosis, detection of minimal residual disease, as well as immune monitoring and profiling following immunotherapy. Detection of specific host proteins for diagnosis predominantly uses quantitative PCR and western blotting assays. In this study, we optimized a flow cytometry-based detection assay for Factor VIII protein in peripheral blood mononuclear cells (PBMCs). An indirect intracellular staining (ICS) method was standardized using monoclonal antibodies to different domains of human Factor VIII protein. The FVIII protein expression level was estimated by calculating the mean and median fluorescence intensities (MFI) values for each monoclonal antibody. ICS staining of transiently transfected cell lines supported the method's specificity. Intracellular FVIII protein expression was also detected by the monoclonal antibodies used in the study in PBMCs of five blood donors. In summary, our data suggest that intracellular FVIII detection in PBMCs of hemophilia A patients can be a rapid and reliable method to detect intracellular FVIII levels.

Expression analysis of LEDGF/p75, APOBEC3G, TRIM5alpha, and tetherin in a Senegalese cohort of HIV-1-exposed seronegative individuals

Background

HIV-1 replication depends on a delicate balance between cellular co-factors and antiviral restriction factors. Lens epithelium-derived growth factor (LEDGF/p75) benefits HIV, whereas apolipoprotein B mRNA-editing catalytic polypeptide-like 3G (APOBEC3G), tripartite motif 5alpha (TRIM5α), and tetherin exert anti-HIV activity. Expression levels of these proteins possibly contribute to HIV-1 resistance in HIV-1-exposed populations.

Methodology/Principal Findings

We used real-time PCR and flow cytometry to study mRNA and protein levels respectively in PBMC and PBMC subsets. We observed significantly reduced LEDGF/p75 protein levels in CD4+ lymphocytes of HIV-1-exposed seronegative subjects relative to healthy controls, whereas we found no differences in APOBEC3G, TRIM5α, or tetherin expression. Untreated HIV-1-infected patients generally expressed higher mRNA and protein levels than healthy controls. Increased tetherin levels, in particular, correlated with markers of disease progression: directly with the viral load and T cell activation and inversely with the CD4 count.

Conclusions/Significance

Our data suggest that reduced LEDGF/p75 levels may play a role in resistance to HIV-1 infection, while increased tetherin levels could be a marker of advanced HIV disease. Host factors that influence HIV-1 infection and disease could be important targets for new antiviral therapies.