Sherman McCall

Characterization of the 1918 “Spanish” Influenza Virus Matrix Gene Segment

ABSTRACT The coding region of influenza A virus RNA segment 7 from the 1918 pandemic virus, consisting of the open reading frames of the two matrix genes M1 and M2, has been sequenced. While this segment is highly conserved among influenza virus strains, the 1918 sequence does not match any previously sequenced influenza virus strains. The 1918 sequence matches the consensus over the M1 RNA-binding domains and nuclear localization signal and the highly conserved transmembrane domain of M2. Amino acid changes that correlate with high yield and pathogenicity in animal models were not found in the 1918 strain. Phylogenetic analyses suggest that both genes were mammalian adapted and that the 1918 sequence is very similar to the common ancestor of all subsequent human and classical swine matrix segments. The 1918 sequence matches other mammalian strains at 4 amino acids in the extracellular domain of M2 that differ consistently between avian and mammalian strains, suggesting that the matrix segment may have been circulating in human strains for at least several years before 1918.

AMPA protects cultured neurons against glutamate excitotoxicity through a phosphatidylinositol 3-kinase-dependent activation in extracellular signal-regulated kinase to upregulate BDNF gene expression

The signal transduction and molecular mechanisms underlying α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionate (AMPA)‐mediated neuroprotection are unknown. In the present study, we determined a major AMPA receptor‐mediated neuroprotective pathway. Exposure of cerebellar granule cells to AMPA (500 µm) + aniracetam (1 µm), a known blocker of AMPA receptor desensitization, evoked an accumulation of brain‐derived neurotropic factor (BDNF) in the culture medium and enhanced TrkB‐tyrosine phosphorylation following the release of BDNF. AMPA also activated the src‐family tyrosine kinase, Lyn, and the downstream target of the phosphatidylinositol 3‐kinase (PI3‐K) pathway, Akt. Extracellular signal regulated kinase (ERK), a component of the mitogen‐activated protein kinase (MAPK) pathway, was also activated. K252a, a selective inhibitor of neurotrophin signaling, blocked the AMPA‐mediated neuroprotection. The involvement of BDNF release in protecting neurons by AMPA was confirmed using a BDNF‐blocking antibody. AMPA‐mediated neuroprotection is blocked by PP1, an inhibitor of src family kinases, LY294002, a PI3‐K inhibitor, or U0126, a MAPK kinase (MEK) inhibitor. Neuroprotective concentrations of AMPA increased BDNF mRNA levels that was blocked by the AMPA receptor antagonist, 1,2,3,4‐tetrahydro‐6‐nitro‐2,3‐dioxo‐benzo[f]quinoxaline‐7‐sulfonamide (NBQX). The increase in BDNF gene expression appeared to be the downstream target of the PI3‐K‐dependent activation of the MAPK cascade since MEK or the PI3‐K inhibitor blocked the AMPA receptor‐mediated increase in BDNF mRNA. Thus, AMPA receptors protect neurons through a mechanism involving BDNF release, TrkB receptor activation, and a signaling pathway involving a PI3‐K dependent activation of MAPK that increases BDNF expression.

Autopsy series of 68 cases dying before and during the 1918 influenza pandemic peak

The 1918 to 1919 “Spanish” influenza pandemic virus killed up to 50 million people. We report here clinical, pathological, bacteriological, and virological findings in 68 fatal American influenza/pneumonia military patients dying between May and October of 1918, a period that includes ∼4 mo before the 1918 pandemic was recognized, and 2 mo (September–October 1918) during which it appeared and peaked. The lung tissues of 37 of these cases were positive for influenza viral antigens or viral RNA, including four from the prepandemic period (May–August). The prepandemic and pandemic peak cases were indistinguishable clinically and pathologically. All 68 cases had histological evidence of bacterial pneumonia, and 94% showed abundant bacteria on Gram stain. Sequence analysis of the viral hemagglutinin receptor-binding domain performed on RNA from 13 cases suggested a trend from a more “avian-like” viral receptor specificity with G222 in prepandemic cases to a more “human-like” specificity associated with D222 in pandemic peak cases. Viral antigen distribution in the respiratory tree, however, was not apparently different between prepandemic and pandemic peak cases, or between infections with viruses bearing different receptor-binding polymorphisms. The 1918 pandemic virus was circulating for at least 4 mo in the United States before it was recognized epidemiologically in September 1918. The causes of the unusually high mortality in the 1918 pandemic were not explained by the pathological and virological parameters examined. These findings have important implications for understanding the origins and evolution of pandemic influenza viruses.

The relationship between encephalitis lethargica and influenza: A critical analysis

Since encephalitis lethargica’s (EL) prevalence in the 1920s, epidemiologic and clinical debate has persisted over whether EL was caused by, potentiated by, or merely coincident with the Spanish influenza pandemic. Epidemiologic analyses generally suggest that the disorders were coincidental. Beginning in the 1970s, modern experiments on archival brain samples mainly failed to confirm a direct relationship between influenza and EL. These experimental studies have technical limitations, e.g., the appropriateness of antibodies, polymerase chain reaction (PCR) primers and controls, and the extreme paucity and age of available material. These factors render the case against influenza less decisive than currently perceived. Nevertheless, there is little direct evidence supporting influenza in the etiology of EL. Almost 100 years after the EL epidemic, its etiology remains enigmatic, raising the possibility of a recurrence of EL in a future influenza pandemic.

Assessing Behavior in Extinct Animals: Was Smilodon Social?

It has been suggested that saber-tooth species such as Smilodon fatalis were social because partially healed skeletal injuries were found at Rancho La Brea, California. This conclusion assumes injured animals would die without help. This paper will rebut assertions of sociality. First, cats use metabolic reserves to heal quickly without feeding. Second, dehydration is a more profound limitation than starvation as prey carcasses only provide a quarter of necessary water. Injured animals must be mobile enough to find water or die of dehydration. Their presence in a tar pit also strongly suggests locomotion. Finally, the relatively small brain found in Smilodon is not consistent with sociality. Another argument for sociality has been the large ratio of Smilodon to other species in the La Brea tar pits. However, the remains of a non-social species, the Golden eagle (Aquila chrysaetus), are about as common as Smilodon. Contrariwise, the highly social grey wolf (Canis lupus) and coyote (Canis latrans) are extremely rare. Available evidence does not support sociality in Smilodon.

A historical analysis of the relationship between encephalitis lethargica and postencephalitic parkinsonism: A complex rather than a direct relationship

Postencephalitic parkinsonism has been considered unique among disorders with parkinsonian features because it is believed to have a unitary etiology associated with the virus that presumably caused encephalitis lethargica. Careful analysis of the historical record, however, suggests that this relationship is more complex than commonly perceived. In most cases, the diagnosis of acute encephalitis lethargica was made post hoc, and virtually any catarrh‐like illness was considered to have represented encephalitis lethargica, often after an oral history‐taking that was undoubtedly subject to patient recall and physician bias. Also, postencephalitic parkinsonism and oculogyric crises were not recognized as sequelae to encephalitis lethargica until well after other sequelae such as movement disorders and mental disturbances had been identified (see previous paper). We suggest here that the relationship between encephalitis lethargica and postencephalitic parkinsonism is not simplistic, i.e., encephalitis lethargica was not solely responsible for the etiology of postencephalitic parkinsonism, thus aligning the latter with most other parkinsonian disorders that are now believed to have multiple causes.

Evidence for an enterovirus as the cause of encephalitis lethargica

BackgroundThe epidemic of encephalitis lethargica (EL), called classical EL, was rampant throughout the world during 1917–1926, affecting half a million persons. The acute phase was lethal for many victims. Post-encephalitic parkinsonism (PEP) affected patients for decades. Our purpose was to investigate the cause of classical EL by studying the few available brain specimens. Cases of PEP and modern EL were also studied. Transmission electron microscopy (TEM) and immunohistochemistry were employed to examine brain from four classical EL cases, two modern EL cases and one PEP case.MethodsStandard methods for TEM, immunohistochemistry and RTPCR were applied.Results27 nm virus-like particles (VLP) were observed in the cytoplasm and nuclei of midbrain neurons in all classical EL cases studied. Large (50 nm) VLP and 27 nm intranuclear VLP were observed in the modern EL cases and the PEP case. Influenza virus particles were not found. VLP were not observed in the control cases. TEM of cell cultures inoculated with coxsackievirus B4 and poliovirus revealed both small and large intranuclear virus particles and small cytoplasmic particles, similar to the VLP in EL neurons. In the EL brains, nascent VLP were embedded in putative virus factories and on endoplasmic reticulum (ER). The VLP in the cases of classical EL survived, whereas ribosomes underwent autolysis due to the lack of refrigeration and slow formaldehyde fixation of whole brain. The VLP were larger than ribosomes from well preserved brain. Immunohistochemistry of classical EL cases using anti-poliovirus and anti-coxsackievirus B polyclonal antibodies showed significant staining of cytoplasm and nuclei of neurons as well as microglia and neuropil. Purkinje cells were strongly stained.A 97-bp RNA fragment of a unique virus was isolated from brain tissue from acute EL case #91558. Sequence analysis revealed up to 95% identity to multiple human Enteroviruses. Additional cases had Enterovirus positive reactions by real time PCR.ConclusionsThe data presented here support the hypothesis that the VLP observed in EL tissue is an Enterovirus.

Does the historical literature on encephalitis lethargica support a simple (direct) relationship with postencephalitic Parkinsonism

This article and the subsequent one suggest that the currently accepted view of a simplistic (direct) relationship between encephalitis lethargica (EL) and postencephalitic Parkinsonism (PEP) is based on a incomplete evaluation of the epidemic period literature. In this article we provide a detailed analysis of the literature from the period that demonstrates that Parkinsonism was not initially part of acute EL symptomatology, that PEP was not typically the prevailing type of chronic EL and that oculogyric crises were never part of acute EL symptomatology and not initially associated with PEP. The second paper uses these finding, and also examines the clinical justifications for concluding that all patients with PEP had prior acute episodes of EL, to reevaluate the presumed direct etiologic relationship between EL and PEP.