1. Taylor Goldbeck

2.  Professor and Head of Neuropathology at Yale- Department of Surgery and Faculty of Neurosciences and Virology  Focuses on dementia was emphasis on TSEs  “We think it is most likely the host PrP is a required receptor for TSE viruses, and that viral PrP-membrane interactions ultimately cause a pathological PrP response. Ongoing experiments are designed to test this viral hypothesis”

5.  Prion strain- defined as “infectious isolates that, when transmitted to identical hosts, exhibit distinct prion-disease phenotypes”  Prion strain diversity first seen in goats  PrP-c and PrP-sc can be unglycosylated, monoglycosylated or diglycosylated. Aguzzi, A., Heikenwalder, M., Polymenidou, M. (2007). Insights into prion strains and neurotoxicity. Nature. 8:552-561

6. Aguzzi et al. (2007). Insights into prion strains and neurotoxicity. Nature.8): 552-561

7.  PrP-res ◦ Part of response, not the cause ◦ Host protein  “(i) The variety of unique and mutable agent strains, a property of nuclei acid not protein” ◦ Initial thoughts on this point?

8.  Manuelidis et al (1997)  Argue: ◦ Several strains, same PrP amino acid sequence ◦ Different phenotypes  Due to PrP protein or hidden virus?  Experiment ◦ Change a CJD strain into a strain that produced plaques and cerebellar lesions  Evaluated host recognition by responses of microglia and astrocytes  Used inbred mice, guinea pigs, and rats.  2/6 rats showed a response after first passage Manueldis, L., Fritch, W., Xi, Y. (1997). Evolution of a strain of CJD that Induces BSE-Like Plaques. Science. 277(5322): 94-98.

10.  If you were pro protein-only hypothesis, how would you explain the reactive microglia and astrocytes?  Authors state “Species barrier and host responses (reactive microglia, astrocytes, and development of new strain that can produce plaques/lesions from a strain that couldn’t before) to the foreign agent are too complex to just be explained by the host’s PrP sequence” ◦ If you were pro protein-only hypothesis, how would you respond to this?

11.  “TSE strains maintain their identity despite various changes in prion protein. This fact strongly implicates a relatively stable but mutable viral genome” (from Yale bio page)  Wanted to see whether PrP-res itself encoded intrinsic infectivity characteristics  Slow SY strain and fast virulent FU CJD strain infect GT1 cells into various cell lines ◦ Kept phenotypes through passage but remained indistinguishable by PrP-res banding or glycosylation patterns  FU had different PrP-res patterns in different cell lines  Still had same incubation time and clinical features ◦ Amount of PrP-res was not quantitatively related to infectivity  “It is the biology of these agents: their evolution spread, cell specificity, latency, virus-like interference capabilities and occusional mutation which continues to indicate a viral causative agent” ◦ Arjona et al. (2004). Two Creutzfeldt-Jakob disease agents reproduce prion protein-independent identities in cell cultures. PNAS. 101(23): 8768-8773

12.  Authors argue “These findings (two strains that have different phenotypes but same PrP- res banding or glycosylation patterns) are problematic for the prion hypothesis where abnormal PrP folding or glycosylation, and hense PrP-res band patterns, are postulated to encode each agent strain” ◦ If you were pro- protein-only hypothesis, how would you respond?

13.  Methods: Exposed cells to various dilutions of prion samples, let the cells propagate, determined the proportion of PrP-sc containing cells by ELISA ◦ Strain 22L transferred from brain to PK1 cells ◦ In the presence of swainsonine, 22L-infected PK1 cells led to drug-resistant variants ◦ 22L prions transferred to R33 cell population ◦ R33 incompetent/swa-sensitive cells return to brain Mahal et at. (2010). Transfer of a prion strain to different hosts leads to emergence of strain variants. PNAS. 107(52): 22653-22658

14.  Showed prions can adapt to survive in a new host environment ◦ When transferring from one cell line to another, prion properties chance  “Darwinian Evolution without DNA” ◦ Prions can develop mutations  drug resistance ◦ Fold in different ways  new strains ◦ Transferred to a new host  which strain ‘wins’?  Your thoughts ◦ If you were Manulidis, how would you respond to this paper?

15.  Back to PrP glycosylation ◦ Study by Cancellotti et al., (2013) showed that the passage of mice that expressed a PrP that either partially or completely lacked N-glycan affected the phenotypic characteristics of at least one TSE strain  Back to species barrier ◦ Quasispecies hypothesis  Several PrP-sc conformations in infectious innoculum. One best suited for new host is selected for  Problem- there isn’t a lot of evidence that a large number of conformations exists in an innoculum  Another problem?  Explaining the relationship between PrP-res and infectivity Poggiolini, I., Saverloni, D., Parchi, P. (2013). Prion Protein Misfolding, Strains, and Neurotoxicity: An Update from Studies on Mammalian Prions. International Journal of Cellular Biology. 1-24 Soto, C and Castilla, J. (2004). The controversial protein-only hypothesis of prion propagation. Nature medicine. 563-567