Comparative Study on Molecular Epidemiology of Measles H1a Outbreak and Sporadic Cases in Shandong Province, 2013-2019

Background: Measles caused by measles virus (MeV) is a highly contagious viral disease which has also been associated with complications including pneumonia, myocarditis, encephalitis, and subacute sclerosing panencephalitis. The current study collected33 strains from 2013 to 2019 in 13 cities of Shandong province and separate them into 2 group, outbreak cases and sporadic cases. Comparative of genetic characterization between 15 outbreak strains and 18 sporadic strains was made using nucleotide sequencing of the C-terminal region of the N protein gene(N-450). Results: The results showed that all 33 stains belonged to genotype H1a. The outbreak strains and sporadic strains distribute crossly in phylogenetic tree. Sequences alignment revealed some interesting G and A transversion, which change the amino acids, on sites 1317, 1422, 1543. The nucleotide sequence and amino acid homologies of 15 Shandong outbreak isolates were 98%–100% (0–10 nucleotide variation) and 97.7%–100%, for sporadic isolations, they are 97.3%–100% and 96.6%–100% respectively. The mean evolution rate of 15 outbreak isolations and 18 sporadic isolations was 4.73× 10-3 and 2.068× 10-3 substitutions per site per year separately, which is higher than the study made before 2002. Conclusions: This report compared epidemic and genetic characteristics of outbreak strains and sporadic strains, and raise evolutionary study of sporadic cases may be helpful for discovery of the possibility of outbreak, especially in the stage of measles elimination.

SSPE (SUBACUTE SCLEROSING PANENCEPHALITIS) - THE GREAT MASQUERADER

Background: SSPE is chronic progressive encephalitis affecting children and young adults which usually presents with cognitive decline and behavioural changes followed by periodic myoclonic jerks, seizures, vision loss and ataxia. High degree of suspicion is required as the presentation can be variable and can have many differentials. Aim: We aim to study various presentations of SSPE Methods and Material: Retrospective study was done to analyse various presentations in patients diagnosed with SSPE as per modied Dykens criteria from a tertairy care centre over a period of 2 years (1st January 2018-31st December 2020). Results: 6 cases of SSPE were identied. Case1 - 22 months old presented with subacute history of ataxia, multical myoclonus and developmental regression. Gradually myoclonus worsened to involve trunk and developed drop attacks. Case 2 - 17 years boy presented with single episode of seizure. Case 3- 25 years female with 5 months gestation presented with subacute vision loss followed by progressive cognitive decline, behavioural changes, Parkinsonism, Dystonia and stimulus sensitive myoclonus. Case4- 28 years female presented with rapidly progressive cognitive decline and behavioural changes. Case 5- 32 years male presented with history of myoclonic jerks and dropping of objects. Gradually developed progressive behavioural changes and cognitive decline and became vegetative. Case6 - 9 year old child presented with faciobrachial seizures (myoclonic jerks) and scholastic backwardness. Conclusions: SSPE can manifest with varied presenting complaints. Also, Results of EEG, MRI and CSF examination can change during the disease course. Therefore, high degree of suspicion is required for early diagnosis of this challenging entity.

Short-stalk isoforms of CADM1 and CADM2 trigger neuropathogenic measles virus-mediated membrane fusion by interacting with the viral hemagglutinin

Measles virus (MeV), an enveloped RNA virus in the family Paramyxoviridae , usually causes acute febrile illness with skin rash, but in rare cases persists in the brain, causing a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE). MeV bears two envelope glycoproteins, the hemagglutinin (H) and fusion (F) proteins. The H protein possesses a head domain that initially mediates receptor binding and a stalk domain that subsequently transmits the fusion-triggering signal to the F protein. We have recently shown that cell adhesion molecule 1 (CADM1, also known as IGSF4A, Necl-2, SynCAM1) and CADM2 (also known as IGSF4D, Necl-3, SynCAM2) are host factors enabling cell-cell membrane fusion mediated by hyperfusogenic F proteins of neuropathogenic MeVs as well as MeV spread between neurons lacking the known receptors. CADM1 and CADM2 interact in cis with the H protein on the same cell membrane, triggering hyperfusogenic F protein-mediated membrane fusion. Multiple isoforms of CADM1 and CADM2 containing various lengths of their stalk regions are generated by alternative splicing. Here we show that only short-stalk isoforms of CADM1 and CADM2 predominantly expressed in the brain induce hyperfusogenic F protein-mediated membrane fusion. While the known receptors interact in trans with the H protein through its head domain, these isoforms can interact in cis even with the H protein lacking the head domain and trigger membrane fusion, presumably through its stalk domain. Thus, our results unveil a new mechanism of viral fusion triggering by host factors. Importance Measles, an acute febrile illness with skin rash, is still an important cause of childhood morbidity and mortality worldwide. Measles virus (MeV), the causative agent of measles, may also cause a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE), several years after acute infection. The disease is fatal, and no effective therapy is available. Recently, we have reported that cell adhesion molecule 1 (CADM1) and CADM2 are host factors enabling MeV cell-to-cell spread in neurons. These molecules interact in cis with the MeV attachment protein on the same cell membrane, triggering the fusion protein and causing membrane fusion. CADM1 and CADM2 are known to exist in multiple splice isoforms. In this study, we report that their short-stalk isoforms can induce membrane fusion by interacting in cis with the viral attachment protein independently of its receptor-binding head domain. This finding may have important implications for cis -acting fusion triggering by host factors.

VARIATIONS IN CLINICAL PRESENTATION, NEUROIMAGING AND EEG PATTERNS OF SUBACUTE SCLEROSING PANENCEPHALITIS

Objective: To determine the variations in clinical presentation, neuroimaging and electroencephalography patterns of subacute sclerosing panencephalitis. Study Design: Cross-sectional study. Place and Duration of Study: Children’s Hospital & Institute of Child Health, Lahore, Pakistan, from Jul to Dec 2020. Methodology: We recruited children presented with clinical features suggestive of subacute sclerosing panencephalitis, along with positive anti-measles antibodies on cerebrospinal fluid. Association between variables was determined to formulate an early diagnosis of subacute sclerosing panencephalitis. Results: Out of 47 children, 29 were males with a mean age of 6.54 ± 2.9 years. Only 23% were fully immunized against measles, 36.2% were unvaccinated and 40.4% received partial immunization. The mean age of measles infection was 1.49 ± 1.2 years; the mean interval between measles and onset of SSPE was 4.13 ± 3 years. Atypical clinical presentation was seen in 38.3% with intractable epilepsy (8.5%), focal deficit (8.5%) and extrapyramidal symptoms (8.5%) being commonest followed by coma (6.4%), visual loss (4.3%) and psychosis (2.1%). Neuroimaging was suggestive of cortical hyperintensities in 46.8% and was normal in 46.8%. Electroencephalography showed burst suppression in 55.3% and atypical findings in 19.1%. Younger age (1-1.5 years) of measles and unimmunized status were associated with early onset of SSPE with a p-value of 0.001 and 0.05 respectively. Non-immunized status was associated with atypical presentation of SSPE (p-value <0.05). Conclusion: The younger age of measles infection and failure to receive complete immunization led to early onset of Subacute sclerosing panencephalitis with an atypical presentation.

M protein of subacute sclerosing panencephalitis virus, synergistically with the F protein, plays a crucial role in viral neuropathogenicity

Subacute sclerosing panencephalitis (SSPE) is a rare fatal neurodegenerative disease caused by a measles virus (MV) variant, SSPE virus, that accumulates mutations during long-term persistent infection of the central nervous system (CNS). Clusters of mutations identified around the matrix (M) protein in many SSPE viruses suppress productive infectious particle release and accelerate cell–cell fusion, which are features of SSPE viruses. It was reported, however, that these defects of M protein function might not be correlated directly with promotion of neurovirulence, although they might enable establishment of persistent infection. Neuropathogenicity is closely related to the character of the viral fusion (F) protein, and amino acid substitution(s) in the F protein of some SSPE viruses confers F protein hyperfusogenicity, facilitating viral propagation in the CNS through cell–cell fusion and leading to neurovirulence. The F protein of an SSPE virus Kobe-1 strain, however, displayed only moderately enhanced fusion activity and required additional mutations in the M protein for neuropathogenicity in mice. We demonstrated here the mechanism for the M protein of the Kobe-1 strain supporting the fusion activity of the F protein and cooperatively inducing neurovirulence, even though each protein, independently, has no effect on virulence. The occurrence of SSPE has been estimated recently as one in several thousand in children who acquired measles under the age of 5 years, markedly higher than reported previously. The probability of a specific mutation (or mutations) occurring in the F protein conferring hyperfusogenicity and neuropathogenicity might not be sufficient to explain the high frequency of SSPE. The induction of neurovirulence by M protein synergistically with moderately fusogenic F protein could account for the high frequency of SSPE.