An Overview of Cell-Based Assay Platforms for the Solute Carrier Family of Transporters

The solute carrier (SLC) superfamily represents the biggest family of transporters with important roles in health and disease. Despite being attractive and druggable targets, the majority of SLCs remains understudied. One major hurdle in research on SLCs is the lack of tools, such as cell-based assays to investigate their biological role and for drug discovery. Another challenge is the disperse and anecdotal information on assay strategies that are suitable for SLCs. This review provides a comprehensive overview of state-of-the-art cellular assay technologies for SLC research and discusses relevant SLC characteristics enabling the choice of an optimal assay technology. The Innovative Medicines Initiative consortium RESOLUTE intends to accelerate research on SLCs by providing the scientific community with high-quality reagents, assay technologies and data sets, and to ultimately unlock SLCs for drug discovery.

Search for genomic sequences of microbial agents in atherosclerotic plaques

Atherosclerosis is a complex, multifactorial disease. Several studies have reported a possible association between infection with microbial agents and atherogenesis. Chlamydia pneumoniae (C. pneumoniae), Herpes Simplex Virus 1 (HSV1), Human Cytomegalovirus (HCMV), and Epstein Barr Virus (EBV) have been widely investigated for their possible role in atherosclerosis development, but the results obtained to date are contradictory. The aim of our study is to search DNA of the aforementioned infectious agents by means of Quantitative Real Time PCR in atherosclerotic plaques from carotid arteries obtained from 17 patients. Genomic sequences of C. pneumoniae, HSV1, HCMV were not found in any atherosclerotic lesion. Therefore, our results do not support the hypothesis of an association between these infectious agents and atherosclerosis. Conversely, three patients were found to be positive for EBV DNA, thus indicating that, at least in a limited number of patients, EBV could play a role in atherogenesis.

Polymorphisms of the BK virus subtypes and their influence on viral in vitro growth efficiency

The major capsid protein, VP1, of the human polyomavirus BK (BKV) is structurally divided into five outer loops, referred to as BC, DE, EF, GH, and HI. The BC loop includes a short region, named the BKV subtyping region, spanning nucleotides 1744-1812 and characterized by non-synonymous nucleotide polymorphisms that have been used to classify different strains of BKV into four subtypes. The aim of this study was to determine if the nucleotide changes clustered within the BKV subtyping region may influence the in vitro growth efficiency of the virus. We therefore infected the African Green Monkey kidney cell line Vero with four different viral strains (named BKV I, II, III, and IV) that contained the nucleotide sequences of the BKV subtypes within the same genomic background. Infected cells were followed for 59 days and viral replication was assessed at different time points by quantitative real-time PCR (Q-PCR). BKV I, II, and IV were successfully propagated over time in Vero cells, whereas BKV III viral loads progressively decreased during the infection course, demonstrating that the non-synonymous nucleotide polymorphisms of subtype III confer a strong disadvantage for viral replication. Since subtype III differs from all the other subtypes at position 68 of the VP1, where Leu is replaced by Gln, we created viral strains bearing Gln at this position together with the polymorphisms of subtypes I, II, IV and tested their growth in Vero cells. Our results demonstrate that this amino acid substitution does not lower the replication efficiency of subtypes I, II, and IV. In conclusion, this study provides further insights to the importance of the BC loop of BKV in the virus life cycle. In addition, given the effect of the amino acid substitutions of the four BKV subtypes on infectious spread of the virus, our results suggest the need to investigate their potential association with BKV related complications.

Lymphotropic polyomavirus is detected in peripheral blood from immunocompromised and healthy subjects

BACKGROUND

Lymphotropic Polyomavirus (LPV) was isolated from a B-lymphoblastoid cell line of an African green monkey. This virus shares some characteristics with human polyomaviruses, but it is antigenically distinct from BK Virus (BKV) and JC Virus (JCV). Seroepidemiological studies revealed that human sera react in the presence of LPV antigens, and, recently, the viral genome was amplified in the peripheral blood from patients affected with HIV-related leukoencephalopathies.

OBJECTIVES

The aims of the study were to investigate and compare the presence of LPV DNA with that of JCV and BKV in different biological samples and patient groups.

STUDY DESIGN

LPV, JCV and BKV DNA were searched and quantified in peripheral blood and CSF from HIV+ patients and in peripheral blood from healthy subjects.

RESULTS

The LPV genome was detected in peripheral blood of both HIV+ patients and healthy subjects, with a prevalence of 7.2% and 4.7% respectively, but not in CSF. However, its presence was less frequent than that of JCV and BKV.

CONCLUSIONS

The amplification of LPV genome from human peripheral blood confirms the fact that LPV can infect the human population. LPV DNA was amplified from patients affected with HIV-related leukoencephalopathies but also from HIV patients without neurological disorders and from healthy subjects. Therefore, the results do not support the hypothesis of an association between LPV infection and any neurological disease. However, given their high similarity, it is possible that LPV, as well as BKV and JCV, could establish latency in humans and cause disease only in rare circumstances.

Mutations in the external loops of BK virus VP1 and urine viral load in renal transplant recipients

Polyomavirus-associated nephropathy (PVAN) is a major complication that occurs after renal transplantation and is induced by reactivation of the human polyomavirus BK (BKV). The structure of the viral capsid protein 1 (VP1) is characterized by the presence of external loops, BC, DE, EF, GH, and HI, which are involved in receptor binding. The pathogenesis of PVAN is not well understood, but viral risk factors are thought to play a crucial role in the onset of this pathology. In an attempt to better understand PVAN pathogenesis, the BKV-VP1 coding region was amplified, cloned, and sequenced from the urine of kidney transplant recipients who did, and did not, develop the pathology. Urine viral loads were determined by using real time quantitative PCR (Q-PCR). Amino acid substitutions were detected in 6/8 patients, and 6/7 controls. The BC and EF loop regions were most frequently affected by mutations, while no mutations were found within the GH and HI loops of both patients and controls. Some mutations, that were exclusively detected in the urine of PVAN patients, overlapped with previously reported mutations, although a correlation between changes in amino acids and the development of PVAN was not found. Urine viral loads were higher than that of the proposed cut-off loads for identification of patients that are at a high risk of developing PVAN (10(7) copies/ml), both in the PVAN and control groups, thus confirming that urine viral load is not a useful predictive marker for the development of PVAN.

Presence and expression of JCV early gene large T Antigen in the brains of immunocompromised and immunocompetent individuals

JC virus (JCV) is a polyomavirus that asymptomatically infects up to 80% of the worldwide human population and establishes latency in the kidney. In the case of host immunodeficiency, it can cause progressive multifocal leukoencephalopathy (PML), which is a fatal demyelinating disease of the central nervous system. In an attempt to understand better PML pathogenesis and JCV infection, the presence of the JCV genome and expression of the early viral protein in the brain of deceased individuals, with and without HIV infection, was investigated. Sixty autopsy samples of brain tissues were collected from 15 HIV-positive PML patients, 15 HIV-positive patients with other neurological diseases, 15 HIV-positive patients without neurological disorders, and 15 HIV-negative individuals who died from diseases unrelated to the central nervous system. By means of specific Real Time Polymerase Chain Reaction, the JCV genome was detected in 14 of 15 PML brains, three of 15 HIV-positive brains (with and without neurological diseases), and 1 of 15 HIV-negative brains. JCV genotyping was also performed. Expression of the early JCV protein T Antigen was verified by a specific immunohistochemistry assay, and it was found in the brain tissues from 12 PML cases and one case with other neurological disease. The data obtained demonstrate that infection of the brain with JCV can also be observed in the brains of HIV-negative individuals, without neurological disorders. However, viral protein expression was limited to PML brains and to one brain from a patient with other neurological disease, suggesting that JCV can also be present in the brains of patients without PML.

Application of molecular tools for the diagnosis of central nervous system infections

Many infectious agents can cause central nervous system (CNS) diseases in humans. Since microbial agents infecting CNS are numerous and have different features, conventional laboratory tests may not be sensitive enough to identify and characterise viruses and bacteria in human biological specimens. Thus, the need to define methods for the diagnosis of infectious neurological diseases, such as progressive multifocal leukoencephalopathy (PML), is urgent, in order to improve the outcome of the diseases with rapid and accurate detection of the pathogens.

JC virus VP1 loop-specific polymorphisms are associated with favorable prognosis for progressive multifocal leukoencephalopathy

JC virus (JCV) is a human polyomavirus that causes progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease that mainly affects immunocompromised subjects. Since its discovery, PML has been considered a rapidly progressing fatal disease; however, amino acid substitutions in the capsid viral protein have recently been tentatively associated with changes in PML clinical course. In order to provide more insight to PML pathogenesis and identify potential prognostic markers, seven cerebrospinal fluid (CSF) samples and four brain autopsy samples were collected from patients afflicted with PML with different clinical courses (fast- and slow-progressing), and the JCV VP1 coding region was amplified, cloned, and sequenced. In addition, urine samples were collected and analyzed from nine patients with PML or other neurological diseases (ONDs) as a control group. Sequencing analysis of the genomic region encoding the VP1 outer loops revealed polymorphic residues restricted to four positions (74, 75, 117, and 128) in patients with slow PML progression, whereas no significant mutation was found in JCV isolated from urine. Collectively, these data show that JCV VP1 loop mutations are associated with a favorable prognosis for PML. It is therefore possible that slower progression of PML may be related to the emergence of a less virulent JCV strain with a lower replication rate.

[Viral infections of the fetus and newborn infant]

Viral infections may be vertically transmitted from mother to child at different times, ranging from in utero transmission, which occurs during pregnancy, perinatal transmission, which takes place during delivery and postnatal transmission, which is usually the consequence of breastfeeding. Mother-to-child transmission, which may occur after primary, recurrent or chronic maternal infection, is potentially harmful to the fetus or the newborn since it may result in miscarriage, fetal death, congenital anomalies, intrauterine growth restriction, or severe neonatal disease. Some risk factors are thought to affect the rate of mother-to-child transmission, such as the presence of other viral infections, maternal viral load, type of infection (primary versus recurrent), obstetrical procedures (prolonged rupture of membranes, mode of delivery), social-economical conditions and breastfeeding. For some of the vertically transmitted viruses, interventions are nowadays available to prevent mother-to-child transmission, such as vaccines, passive immunization, antiviral drugs. Moreover, perinatal and postnatal infections may be prevented by the use of elective caesarean delivery and avoidance of breastfeeding.

A family based linkage analysis of HLA and 5-HTTLPR gene polymorphisms in Sardinian children with autism spectrum disorder

Autism spectrum disorders (ASD) are characterized by a broad range in clinical presentation. Although a definite genetic cause has not yet been fully demonstrated, family based studies suggest that a multigenic pattern may be responsible for susceptibility, but most results are conflicting and have yet to be replicated. The purpose of this investigation was to analyze the linkage of the human leukocyte antigen (HLA) and the human serotonin transporter coding (5-HTTLPR) genes with ASD in a group of 37 families of Sardinian ethnicity in insular Italy. In 50% of these families, ASD is linked to HLA, and in the other 50% it is linked to 5-HTTLPR polymorphic genes; in other words, linkage to one or the other was evident in all cases. Despite a very homogenous genetic pattern being generally reported for Sardinians, the linkage observed with HLA and 5-HTTLPR genetic regions indicated a statistically defined heterogeneity (p=0.002). No allelic HLA or 5-HTTLPR polymorphisms were specifically associated with ASD, suggesting these loci as markers of other genes mapped in their close proximity that may be more directly involved and thus may merit further analytical studies.