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Hochhalter et al. Association between HCMV and GBM

performed ISH using a HCMV DNA probe cocktail and this study reported no strong evidence of HCMV in any
found that 81% of samples analyzed demonstrated of the samples. A few samples were found to contain
HCMV specific staining. Another study utilized low levels of viral reads but upon closer inspection
[58]
multiple detection assays to test for the presence of the authors report that these reads likely represented
HCMV. The targets for these assays were IE1-72, pp65, artifact or non-pathological infections. Finally, evidence
and late antigen. A total of 36 formalin-fixed paraffin- of human papillomavirus (HPV) and hepatitis B were
embedded (FFPE) GBM samples were tested across found in a few LGG samples, however, the authors
each assay with varying rates of detection. A total of of this study state that these findings need further
33 out of the 36 samples (91.6%) stained positive for evidence to substantiate this association. [36]
IE1-72. The other two HCMV antigens, pp65 and late
antigen, stained positive in 28/36 (77.7%) and 26/36 Lastly, another study used droplet digital PCR
(72.2%), respectively. [60] (ddPCR) to detect the presence of HCMV, human
herpes virus 6 (HHV-6), and Epstein-Barr virus (EBV)
On the other hand, several recent studies have in brain tissue samples. A total of 112 brain tissue
[61]
reported no association between HCMV and GBM. samples comprising 45 glioblastoma, 12 astrocytoma
One study utilized several approaches including a grade III, 2 astrocytoma grade II, 4 astrocytoma grade
prospective and retrospective analysis to detect the I, and 49 controls were included in this study. The
presence of HCMV in tissue, plasma, and serum of study reported that neither HCMV nor HHV-6A was
high-grade glioma (HGG) patients. [35] The authors detected in any of the astrocytoma samples. A higher
of this study retrospectively analyzed 25 fresh frequency of positivity was observed for EBV and
frozen tissues from GBM patients using PCR, tissue HHV-6B compared to controls. [61]
microarrays from 70 HGG patients using IHC, and 20
FFPE GBM tissues using IHC and CISH targeted at A few recent studies may shed light onto why there is
IE1/2 and pp65. All tissue analyzed for the presence such discrepancy observed in the literature. A study
of HCMV were found to be negative irrespective of by Yamashita et al. attempted to detect HCMV
[34]
method used. [35] The prospective arm of the study in GBM samples through a wide range of detection
contained 18 patients with newly diagnosed HGG. methods. They were unable to detect the presence
From these patients, a total of 11 FFPE whole of HCMV in many of the samples. Interestingly, the
sections, 38 plasma samples, and 15 serum samples authors noted that the HCMV positivity demonstrated
were analyzed. Tissue samples were analyzed for in a few samples were actually the HCMV antibodies
HCMV using real-time PCR, CISH, and IHC under binding to non-viral human proteins such as human
[34]
the same protocols as the retrospective arm. Utilizing albumin and myelin basic protein. This finding
these different detection methods there was no suggests a previously unknown cross-reactivity among
[35]
evidence of HCMV in the 11 FFPE samples. Eight HCMV antibodies. Another study by Holdhoff et al.
of 15 patients were seropositive for HCMV. Of the assessed whether altering experimental conditions
38 plasma samples that were collected HCMV was could generate false positive results. The authors of
detected in low levels in 3 samples at baseline and this study demonstrated positive staining in previously
only one in follow up. [35] negative control fibroblast cells by using higher
concentrations of the primary HCMV monoclonal
Another study took a comprehensive approach to antibody. Similarly, varying antibody concentrations
analyze a wide variety of samples using NGS to detect in brain tumor FFPE samples demonstrated false
the presence of viral genomes in the samples. positive staining. Taken together, the authors of
[36]
This analysis was performed through the publically this study suggest that false positive staining can
available sequencing datasets from the Cancer be readily achieved simply by using high antibody
Genome Atlas (TCGA). The samples tested included concentrations even with antibodies that are designed
157 RNA-seq datasets from primary GBM, 13 to be specific. [35]
recurrent GBM, 514 low-grade gliomas, 17 recurrent
low-grade gliomas, and 5 normal brain, and whole THERAPEUTIC TARGETS FOR HCMV
genome sequencing (WGS) datasets from 51 primary
GBM, 10 recurrent GBM, and 20 normal matched The potential for novel breakthroughs in treating
blood samples. In addition, 92 RNA-seq datasets patients with GBM has led to a search for HCMV
from MRI-guided biopsies and 9 glioma stem-like cell specific targets. Currently, there are two main
cultures were analyzed. Finally, 64 DNA-seq datasets approaches that are being pursued; one focuses on
from 11 meningiomas and their corresponding blood anti-viral therapy and the other focuses on HCMV
control samples were also analyzed. The authors of directed immunotherapy.
Neuroimmunology and Neuroinflammation ¦ Volume 4 ¦ June 16, 2017 101