I had a lot of thoughts on these papers, as my last co-op was using gut microbiota to try and influence development of allergies and autoimmune disorders. My first thought is I really liked the Buffington paper, while I did not like reading the Reber paper at all. First and foremost, I felt as though the Reber paper was disorganized and incredibly difficult to read, additionally, it seemed as though their results had anomalies which made it difficult to draw conclusions from the data. One such example of this can be found in Fig1D-1E. While I understood the concept, I am wondering how one could draw a conclusion from the data presented when the vehicle decreased almost 10% in % time in open arms. The vehicle has no experimental manipulation, and as such, the 2 week interval between immunizations should not have resulted in such a drastic increase in anxiety like behavior. It's misleading to show significance in Fig1E because despite that the difference is significant there and not in Fig1D, it seems as though this is only due to the strange decrease in time spent in open arms in vehicle, which the experimental conditions shouldn't have changed. It is a huge decrease too, and it seems as though this is an anomaly that is giving misleading data.
Moving to the Buffington paper, I appreciated their clear results and their experimental design. Reading through I kept thinking back to my own work with gut microbiota, and in those experiments we postulated (in a similar way as Reber, I think) that it wasn't the bacteria themselves conferring the effects, but rather it was the bacterial epitopes on the surface of their membranes that were interacting with the immune system to confer effects. As such, it was interesting to read the Buffington paper as it seemed, based on the heat-killed experiments, that it was the actual bacteria and not their cell-surface protein composition that were causing the behavioral significance. I thought it was incredibly smart to include the heat-killed experiment, as it demonstrated that the results were probably based more on the vagal-gut interaction rather than immune modulation. It was interesting to see that the bacteria rescued behavior when administered at 4weeks rather than at 8weeks. On one had, especially since ASD is present before puberty, this makes sense. But I also have to wonder if its not also due to the ability of the bacteria to colonize. At least in my own work on the subject, the point in development at which the bacteria were administered impacted how the bacteria would colonize the gut. To that extent, it could be that the effects occurred depended on long-term gut microbiota changes (i.e. colonization) that were impacted based on the developmental time point. Additionally, it would have been interesting to take MRD offspring and try to induce the behavioral endophenotype using antibiotics.