INTERVIEW：Tackling Encephalitis: Expanding the Possibilities of Autoantibody Detection with TBA

We had the opportunity to speak with Dr. Ryota Amano from the Neurology Department of Fujiyoshida Municipal Hospital about his impressions and the practical applicability of "Mosaic 3" using Tissue-Based Assay (TBA). This technology leverages staining pattern analysis on tissue slides from the hippocampus and cerebellum to measure autoantibodies.

u  The Reality of Implementation from the Medical Field

Q: What initially motivated you to start using MOSAIC 3?

It’s challenging to make an accurate diagnosis with just the lineblot test in the PNS (paraneoplastic neurological syndrome) panel. Lineblot tests are said to have a high rate of false positives, so I want to ensure confirmation with TBA . Ideally, I would first perform TBA, and if positive findings are observed, use the lineblot test for confirmation. In short, both are necessary, but since I can only submit lineblot tests in the current environment of Japan, I’ve been wondering if there’s a way to address this.

While researching Euroimmun’s products, I found something that, although is RUO, seemed usable. After visiting the lab in Kashiwa to learn how to use it, I was convinced, “This is something I can do in my hospital!”

With TBA, I can test for various antibodies at once, get results faster, NMDAR antibody can be detected specifically. Moreover, it’s also cheaper than outsourcing test for NMDAR antibody. By explaining these benefits within the hospital, I was able to get approval for its implementation.

 

u  Initial Challenges and the Learning Curve

Q: Was it difficult when you first started using Mosaic?

If you have a fluorescence microscope, the assay procedure itself is possible.

When I first started using Mosaic, there were several instances where I thought the results were positive, but upon confirmation with EUROIMMUN, I was told they were "not specific." Through these experiences, I compared results, refined my observations, and developed my own criteria over time.

After about six tests, I began to recognize patterns that deviated from the norm. By the time I had tested around ten patients, I felt more confident in my ability to make judgments. Of course, the number of assays I experienced is still low, I continued refining my approach by experimenting through trial and error.

I sent images to EUROIMMUN for confirmation about four times, and the results usually came back soon. This feedback greatly supported my learning process, allowing me to become more comfortable and accurate in interpreting the results myself.

 

u  How Do Antibody Tests Help in Patient Treatment?

Q: Could you please tell us specifically what kind of patients are most targeted for self-antibody measurements?

For patients with encephalitis, abnormalities are often found through MRI or cerebrospinal fluid tests. However, it’s not always clear at that moment whether the cause is infectious or autoimmune. 

That’s why I perform TBA on all suspected patients. So far, I tested ten patients, and in four cases, I identified the possibility of autoimmune antibodies, though none tested positive for NMDA receptor antibodies.

The strength of TBA lies in its ability to broadly screen for the presence of any autoimmune antibodies without being restricted to specific ones. Once we confirm that the condition is autoimmune rather than infectious, we can confidently proceed with treatment, which can potentially improve the patient’s prognosis.

Ultimately, in the early stages of treatment, it’s less important to know which specific antibody is involved and more critical to determine whether any autoimmune antibody is present. Although the sensitivity is not necessarily high, TBA can detect most autoimmune antibodies, and just knowing that there is some kind of autoantibody can be sufficiently helpful.

u  Early Treatment Approach: Combining Steroid Pulse and IVIg

In the treatment of autoimmune encephalitis, the combination of steroid pulse therapy and IVIg is recommended. However, the timing of IVIg administration largely depends on the physician's judgment. In cases of infection, herpes virus is often suspected, but outsourcing  PCR test results can take several days to almost a week to return in Japan.

Considering this time lag, it may be more effective to begin treatment early, addressing both the potential for infection and autoimmune causes, rather than waiting for PCR results before starting IVIg. However, IVIg treatment is not very effective for infectious encephalitis and may even worsen the situation due to side effects such as thrombosis. The results of TBA are highly useful for making an early decision on whether to proceed with IVIg. While precise data is lacking, early treatment is thought to offer a better chance for improved patient outcomes.

 

u  Specific Case Where TBA Led to Treatment

Q: Could you share any notable cases in which the use of "Mosaic 3" for self-antibody measurement was particularly useful in a clinical setting?

My particularly notable case involved a male patient in his 30s with significant cerebellar atrophy. His MRI showed no clear abnormal signals, and while it resembled spinal cerebellar atrophy, cerebrospinal fluid analysis revealed only a slight increase in cell count, with no inflammatory findings in blood tests.

Curious about the cause, I performed TBA, which revealed the presence of an autoantibody staining the cerebellum. Further testing at Hokkaido University identified this as the extremely rare SEZ6L2 antibody. Without TBA, I might not have reached a diagnosis, and treatment options could have been missed. While the patient is still undergoing treatment, reaching the correct diagnosis and initiating appropriate therapy was possible thanks to TBA.

Additionally, there were three other cases where the specific autoantibody could not be identified, but TBA suggested autoimmune mechanisms. This led to immune therapy, which improved the patients’ conditions. The ability to confidently rule out infection and confirm autoimmune pathology was a critical factor in advancing treatment in these cases.

 u  Why Recommend Mosaic to Neurologists?

Q: For neurologists facing challenges, how would you suggest using Mosaic?

TBA (tissue-based assay) is an essential tool for diagnosing autoimmune encephalitis. With a fluorescence microscope, Mosaic 3 allows performing TBA and detecting NMDA receptor antibodies. The process is straightforward, and results can be interpreted within approximately 90 minutes. Compared to outsourcing test for NMDA antibody in Japan, it’s more cost-effective and delivers faster results.

Outsourcing test for NMDA antibody only provides a positive or negative result, without returning images, which makes it difficult to interpret borderline cases or correlate findings with clinical data. Mosaic enables you to observe and make judgments directly. While it takes some practice initially, anyone can distinguish between strongly fluorescent positive results and completely negative ones, moreover, a faint glow may indicate the presence of autoantibodies, even at a low titer This hands-on approach facilitates faster treatment decisions.

Other kits, such as Mosaic 6, which include specific antibodies, can also be utilized similarly, but the drawback is that TBA cannot be performed. In TBA, it’s important to be cautious about potential false positives, especially with serum samples. Despite this, for physicians looking to expedite early diagnosis and have more control over their evaluations, Mosaic is an extremely valuable tool.