Subacute Sclerosing Panencephalitis

Brain tropism acquisition: The spatial dynamics and evolution of a measles virus collective infectious unit that drove lethal subacute sclerosing panencephalitis

It is increasingly appreciated that pathogens can spread as infectious units constituted by multiple, genetically diverse genomes, also called collective infectious units or genome collectives. However, genetic characterization of the spatial dynamics of collective infectious units in animal hosts is demanding, and it is rarely feasible in humans. Measles virus (MeV), whose spread in lymphatic tissues and airway epithelia relies on collective infectious units, can, in rare cases, cause subacute sclerosing panencephalitis (SSPE), a lethal human brain disease. In different SSPE cases, MeV acquisition of brain tropism has been attributed to mutations affecting either the fusion or the matrix protein, or both, but the overarching mechanism driving brain adaptation is not understood. Here we analyzed MeV RNA from several spatially distinct brain regions of an individual who succumbed to SSPE. Surprisingly, we identified two major MeV genome subpopulations present at variable frequencies in all 15 brain specimens examined. Both genome types accumulated mutations like those shown to favor receptor-independent cell-cell spread in other SSPE cases. Most infected cells carried both genome types, suggesting the possibility of genetic complementation. We cannot definitively chart the history of the spread of this virus in the brain, but several observations suggest that mutant genomes generated in the frontal cortex moved outwards as a collective and diversified. During diversification, mutations affecting the cytoplasmic tails of both viral envelope proteins emerged and fluctuated in frequency across genetic backgrounds, suggesting convergent and potentially frequency-dependent evolution for modulation of fusogenicity. We propose that a collective infectious unit drove MeV pathogenesis in this brain. Re-examination of published data suggests that similar processes may have occurred in other SSPE cases. Our studies provide a primer for analyses of the evolution of collective infectious units of other pathogens that cause lethal disease in humans.

Diagnostic reference value of antibody levels measured using enzyme immunoassay for subacute sclerosing panencephalitis

High measles-specific antibody titers in the cerebrospinal fluid (CSF) have important diagnostic significance for subacute sclerosing panencephalitis (SSPE), a progressive neurological disorder caused by measles virus variants. However, the diagnostic reference value of antibody levels and the usefulness of the CSF/serum ratio measured using enzyme immunoassays (EIAs) for SSPE diagnosis remain unclear. To facilitate SSPE diagnosis using EIAs, measles immunoglobulin G (IgG) titers in the CSF and serum of patients with and without SSPE were measured and their CSF/serum antibody ratios evaluated. Serum and CSF antibody levels were compared among three patients with SSPE (59 paired samples), 37 non-SSPE patients, and 2618 patients of unknown backgrounds. Of the 59 paired samples from three patients with SSPE, 56 paired samples (94.9%) showed CSF measles IgG levels ≥0.5 IU/mL and a CSF/serum ratio ≥0.05, whereas non-SSPE cases showed CSF measles IgG levels <0.1 IU/mL and a CSF/serum ratio <0.03. Of the 2618 CSF samples with unknown backgrounds, 951 showed measurable IgG levels with EIA, with a CSF/serum ratio peak of 0.005-0.02, with a 90th percentile of 0.05. Assuming the SSPE criteria as CSF measles IgG ≥0.5 IU/mL and a CSF/serum ratio ≥0.05, only 20 samples (0.8%) with unknown backgrounds were categorized as having SSPE. Conversely, assuming the non-SSPE criteria as CSF measles IgG <0.1 IU/mL and a CSF/serum ratio <0.03, 2403 samples (92%) with unknown backgrounds were categorized as not having SSPE. In conclusion, high CSF/serum ratios (≥0.05) and high measles CSF IgG levels (≥0.5 IU/mL) may be useful for diagnosing SSPE.

Measles in the 21st Century: Progress Toward Achieving and Sustaining Elimination

The global measles vaccination program has been extraordinarily successful in reducing measles-related disease and deaths worldwide. Eradication of measles is feasible because of several key attributes, including humans as the only reservoir for the virus, broad access to diagnostic tools that can rapidly detect measles-infectious persons, and availability of highly safe and effective measles-containing vaccines (MCVs). All 6 World Health Organization (WHO) regions have established measles elimination goals. Globally, during 2000–2018, measles incidence decreased by 66% (from 145 to 49 cases per million population) and deaths decreased by 73% (from 535 600 to 142 300), drastically reducing global disease burden. Routine immunization with MCV has been the cornerstone for the control and prevention of measles. Two doses of MCV are 97% effective in preventing measles, qualifying MCV as one of the most effective vaccines ever developed. Mild adverse events occur in <20% of recipients and serious adverse events are extremely rare. The economic benefits of measles vaccination are highlighted by an overall return on investment of 58 times the cost of the vaccine, supply chains, and vaccination. Because measles is one of the most contagious human diseases, maintenance of high (≥95%) 2-dose MCV coverage is crucial for controlling the spread of measles and successfully reaching measles elimination; however, the plateauing of global MCV coverage for nearly a decade and the global measles resurgence during 2018–2019 demonstrate that much work remains. Global commitments to increase community access to and demand for immunizations, strengthen national and regional partnerships for building public health infrastructure, and implement innovations that can overcome access barriers and enhance vaccine confidence, are essential to achieve a world free of measles.

Small Non-coding RNA Expression Following Respiratory Syncytial Virus or Measles Virus Infection of Neuronal Cells

Respiratory syncytial virus (RSV) or measles virus (MeV) infection modifies host responses through small non-coding RNA (sncRNA) expression. We show that RSV or MeV infection of neuronal cells induces sncRNAs including various microRNAs and transfer RNA fragments (tRFs). We show that these tRFs originate from select tRNAs (GCC and CAC for glycine, CTT and AAC for Valine, and CCC and TTT for Lysine). Some of the tRNAs are rarely used by RSV or MeV as indicated by relative synonymous codon usage indices suggesting selective cleavage of the tRNAs occurs in infected neuronal cells. The data implies that differentially expressed sncRNAs may regulate host gene expression via multiple mechanisms in neuronal cells.

Electroencephalography Patterns of Subacute Sclerosing Panencephalitis

Introduction and background: This article explores the electroencephalography (EEG) pattern in patients of suspected subacute sclerosing panencephalitis (SSPE) visiting Lady Reading Hospital, Peshawar. Pakistan has a huge deficit of research culture, and limited studies are done on this topic. This study concluded that a typical pattern is the most common EEG pattern, although atypical and normal EEG patterns were also observed. It is worth inclusion into the existing literature and may be used for future literature review of similar studies done elsewhere in Pakistan to give a wider perspective comprised of a larger sample size - integrating all studies.

Objective: To determine the frequency of different patterns of EEG (typical, atypical, and normal) in SSPE patients.

Methodology: Seventy-seven patients of both male and female genders between ages one to 20 years, who were diagnosed with SSPE, were included in the study. Dyken’s criteria were used to diagnose the patients. A prior history of previous measles infection with signs and symptoms suggestive of SSPE and positive anti-measles IgG antibodies in the cerebrospinal fluid (CSF) was found in all the patients included in the study. Besides this, typical EEG patterns and raised CSF globulin levels were also used for confirmation of the diagnosis. All the patients fulfilling the above criteria and presenting to the neurology department of Lady Reading Hospital, Peshawar, from February 1, 2019, to November 30, 2019, were included in the study. All the patients underwent the EEG monitoring in the same EEG laboratory and were reported by the same consultant with careful exclusion of any artifacts during the study.

Result: There were 59 (76.62%) males and 18 (23.37%) females. The mean age was 15 ± 8.6 years, and the mean duration of symptoms was 4.79 ± 1.68 months. EEG was normal in 14 (18.18%) patients, while 63 (81.81%) patients had an abnormal EEG pattern, with a majority of 53 (84.12%) patients showing periodic delta wave complexes. Only 10 (15.87%) patients showed atypical patterns.

Conclusion: Almost all the patients of SSPE showed periodic high-amplitude delta waves complexes, which usually occurs in patients with a disease duration of more than four months. However, further studies with a large sample size are needed for the confirmation of this observation.

Utility of enzyme immunoassays for diagnosis of subacute sclerosing panencephalitis

BACKGROUND

Subacute sclerosing panencephalitis (SSPE) is a progressive neurologic disorder caused by the measles virus (MV) and is identified by positive MV-specific antibody titers, detected mainly by hemagglutination inhibition (HI) tests in the cerebrospinal fluid (CSF). However, an alternative method, the enzyme immunoassay (EIA), has increasingly become a preferred method for detecting MV antibodies. To establish the index for SSPE diagnosis using EIA, we investigated the correlation between HI and EIA titers of MV antibodies in SSPE patients.

METHODS

Data on MV antibody titers and measurement methods at the time of diagnosis in 89 Japanese SSPE cases diagnosed between 1979 and 2006 were obtained by a survey. We also assessed the serum and CSF MV antibody titers in three patients with SSPE and serum MV antibody titers in 38 healthy adults using immunoglobulin G (IgG)-EIA and HI.

RESULTS

In all cases diagnosed as SSPE, IgG-EIA titers in the CSF were ≥0.49 IU/mL. There was a positive correlation between serum antibody values in the controls measured by IgG-EIA and HI. In patients with SSPE, both serum and CSF antibody values, measured by IgG-EIA, and HI, were positively correlated, and a positive correlation was found between the serum and CSF MV antibody titers as measured by IgG-EIA. The serum/CSF MV antibody titer ratios determined by IgG-EIA were <20 in most SSPE patients.

CONCLUSIONS

Immunoglobulin G-EIA may be a suitable alternative method for SSPE diagnosis; however, its potential utility and the cut-off point of ≥0.49 IU/mL should be tested with additional patient cohorts.

Measles virus persistence and its consequences

Clearance of measles virus is complex. Infectious virus is cleared by the adaptive immune response manifested by the characteristic maculopapular rash. CD8+ T cells are major effectors of infectious virus clearance, a process that may fail in individuals with compromised cellular immune responses leading to progressive giant cell pneumonia and/or measles inclusion body encephalitis. In contrast to the usual rapid clearance of infectious virus, clearance of viral RNA is slow with persistence in lymphoid tissue for many months. Persistence of MeV RNA may contribute to the late development of the slowly progressive disease subacute sclerosing panencephalitis in children infected at a young age and to measles-associated immune suppression but also to maturation of the immune response and development of life-long immunity.

High risk of subacute sclerosing panencephalitis following measles outbreaks in Georgia

OBJECTIVE

To describe cases and estimate subacute sclerosing panencephalitis (SSPE) risk following large-sale measles outbreaks in Georgia. A rare, fatal late complication of measles, SSPE is often overlooked in assessments focused on the acute illness. Georgia had 8377 and 11,495 reported measles cases during the 2004-2005 and 2013-2015 outbreaks, respectively, but SSPE burden has not been assessed.

METHODS

SSPE cases diagnosed during 2008-2017 were identified from hospitalization registries in major neurological departments likely to admit SSPE patients. Information on reported measles cases and deaths was obtained from the national measles surveillance system and published reports. The risk of SSPE (number of measles cases per one SSPE case) was calculated for cases associated with the 2004-2005 outbreak. Crude estimates were adjusted to account for potential under-reporting of measles, using 50%, 25% and 10% estimates of completeness of reporting.

RESULTS

Sixteen SSPE cases diagnosed during 2008-2017 were identified. Eleven (92%) of 12 SSPE cases with a known history of measles had infection at ≤2 years and one (8%) at 3 years of age. Crude estimate of SSPE risk for the 2004-2005 outbreak was 1:1396. Adjusted estimates were 1:2792, 1:1:5584 and 1:13 960, assuming 50%, 25% and 10% completeness of reporting measles cases, respectively.

CONCLUSIONS

The review demonstrated substantial risk of SSPE in Georgia, supporting recent data suggesting that risk of SSPE following measles infection is higher than previously thought. To prevent SSPE in Georgia, very high timely immunization coverage for measles should be achieved among children, and immunity gap among adults should be closed.