primate [1,2], MRI should detect viral replication in different areas of the central nervous system.
Acute Disseminated Encephalomyelitis Associated with Poliomyelitis Vaccine
Subhash C. Arya, MBBS, PhD Research Physician Centre for Logistical Research and Innovation M-122 (of part 2), Greater Kailash-II New Delhi, India
To the Editor: In a recent article by Ozawa et al., “Acute disseminated encephalomyelitis associated with poliomyelitis vaccine” , type 2 polio virus strain multiplication in the patient’s central nervous system spared the target neurons. Instead, virus-associated lesions were detected during T2-weighted magnetic resonance imaging (MRI) in the spinal cord. These high-intensity lesions were confined to C1-2, C4-5, and T1-2 on the sagittal section and at the right side of cervical cord on the axial section. Sequencing of the polio vaccine virus type 2 isolate revealed an A3 G mutation at nucleotide 481, T3 C mutation at nucleotides 500 and 795, and a G3 C mutation at nucleotide 1195. Irrespective of the human leukocyte antigen type of the patient , the pathogenic potential of the isolate could be established by in vivo tests of its neurovirulence. Events identical to these would be quite likely in countries known to be polio-free. In Japan the presence of poliomyelitis is absent despite the circulation of potentially neurovirulent recombinant poliovirus strains in raw sewage and river water . These strains do not pose any danger to the inhabitants per se. Nevertheless, incessant rain, flooding of river water, or other disasters could expose inhabitants to infected river water or sewage flowing in the streets. Certainly atypical clinical presentations that are attributable to viral replication from sites that are not known to be afflicted by polio viruses would pose serious challenges for clinicians. Although MRI of the central nervous system would be an asset for clinical management, researchers should investigate the emerging subtle alterations in the pathogenicity of mutant polio virus isolates. Polio virus mutants should be characterized using the most-sensitive route of inoculation into the most-sensitive animal species. For parent Sabin vaccine strains, intraspinal viral inoculation in patas monkeys has been the most-sensitive procedure followed, in order of sensitivity, by cynomolous, vervet, rhesus, and baboons . Transgenic mice carrying cell receptors for polio viruses might fail to detect any nonmotor involvement because they lack grasping and manipulative capacities whereas primates have enlarged “higher centers” in the brain and possess rump-sitting pads. After inoculation of polio virus mutants in the
© 2001 by Elsevier Science Inc. All rights reserved. 0887-8994/01/$—see front matter
References  Ozawa H, Noma S, Yoshida Y, Sekine H, Hashimoto T. Acute disseminated encephalomyelitis associated with poliomyelitis vaccine. Pediatr Neurol 2000;23:177-9.  Yoshida H, Hour H, Master K, Miramar T. Characterization of vaccine-associated polioviruses isolated from sewage and river water in Japan. Lancet 2000;356:1461-3.  Boulger LR, Perkins FT. The effect of the route of inoculation and species of monkey on the sensitivity of the neurovirulence of test. International Symposium on neurovirulence of viral vaccines. Munich, 1965:117-32.
Response: We are grateful for your valuable suggestion in response to our article . Our 6-year-old patient was given the oral poliomyelitis vaccine twice, at 1 and 2 years of age. She never experienced a repetitive infection. We cannot explain the route of the infection. As a matter of fact, two children from the patient’s neighborhood were given the oral poliomyelitis vaccine in May 1997, but we did not mention this fact in our article because the relationship was unknown. Disasters, such as incessant rain and flooding of river water, had not occurred in Hachioji city in 1997. Therefore we believe that the patient was infected via mutated poliomyelitis vaccine excreted by extrafamilial contacts. We also believe that the investigation into the pathogenicity of mutant poliovirus isolates is important. We possess the mutant isolates, but cannot study them because of ethical reasons and cost. Hiroshi Ozawa, MD Department of Pediatrics, Tokyo Metropolitan Hachioji Chilren’s Hospital 4-33-13 Daimachi Hachioji-city Tokyo, 193-0931 Japan. Reference  Ozawa H, Noma S, Yoshida Y, Sekine H, Hashimoto T. Acute disseminated encephalomyelitis associated with poliomyelitis vaccine. Pediatr Neurol 2000;23:177-9.