neurological diseases<\/a>, i.e. multiple sclerosis (MS) and other demyelinating diseases, Guillain\u2013Barre\u00a0syndrome (GBS) and myasthenia gravis often create management problems to\u00a0travel medicine practitioners: there is some concern that\u00a0these conditions could be worsened either by naturally\u00a0acquired infections or by some travel medicine interventions. Moreover, medications to treat the underlying disease\u00a0could interact with some antimalarials and vaccines.<\/p>\nThe first step\u00a0is a careful risk assessment based on the actual knowledge\u00a0of host factors, travel characteristics and environmental\u00a0factors. Contrary to what usually happens with healthy\u00a0travellers, risk assessment may lead travel medicine practitioners to advise against the travel, e.g. when a primary\u00a0travel medicine intervention is absolutely contraindicated and the patient is at high risk of infection or when the\u00a0clinical condition of the patient may worsen because of the\u00a0travel. When travel is not contraindicated, we have to\u00a0consider the possibility to avoid some interventions when\u00a0risk assessment shows a low risk.<\/p>\n
The impact of some immunizations on the underlying\u00a0disease represents an area of concern, since both infections\u00a0and vaccinations may trigger (or have been suspected to)\u00a0neurological autoimmune diseases like MS and GBS. The\u00a0events leading to autoimmune activation after an infection\u00a0(or an immunization) are unknown, but three mechanisms might be involved. The first is antigen-specific and it\u00a0is called molecular mimicry: since some viral and\u00a0bacterial proteins are similar to human proteins (e.g.\u00a0myelin), the immune response may also be directed to\u00a0self antigens.\u00a0The second mechanism is called bystander\u00a0activation and occurs when an infection, through the\u00a0death of host cells, may release previously sequestered\u00a0self-antigens and subsequently allow the activation of\u00a0self-reactive T and B cells that are normally quiescent.\u00a0This activation may be mediated by the release of\u00a0cytokines.\u00a0The third mechanism is non-specific:\u00a0protein of viral and bacterial origin may activate T or B\u00a0cells in ways that are independent from the antigen\u00a0specificity of the responding lymphocyte; this process can\u00a0activate autoreactive lymphocytes.\u00a0The development of\u00a0autoantibodies is frequently observed in virus-infected\u00a0animal models and in patients with viral infections.8\u00a0Nevertheless, only a minority of patients develops clinically\u00a0important autoimmune manifestations, presumably reflecting an individual susceptibility due to genetic factors.4 Since\u00a0infection may cause an autoimmune disease, it is theoretically possible that (under\u00a0particular circumstances) immunization also might trigger a demyelinating disease: some\u00a0vaccines could contain proteins similar to myelin (molecular\u00a0mimicry) or produce a cytokine cascade resulting in\u00a0activation of autoreactive T and B cells leading to an\u00a0immune-mediate inflammatory demyelination.4,9 Furthermore, adjuvants are added to several vaccines to improve\u00a0the immunogenicity, and someone could raise doubts about\u00a0a possible role of such substances in the development of\u00a0autoimmunity. Fortunately, at present only aluminum salts\u00a0are widely used in vaccines, with more than a 75 year record\u00a0of safety all over the world. A recent systematic review on\u00a0adverse events after exposure to aluminum-containing\u00a0vaccines against diphtheria, tetanus, and pertussis found\u00a0no evidence that aluminum salts cause any serious or longlasting adverse events.\u00a0On the contrary, on the basis of\u00a0experimental models, it has hypothesized that recently\u00a0developed oil adjuvants like squalene may induce autoantibodies: their capacity to enhance production of proinflammatory cytokines could stimulate antibody responses to\u00a0foreign antigens and, under particular conditions, selfantigens also.\u00a0Further investigation is needed on this type\u00a0of adjuvant and on its possible role in promoting\u00a0autoimmunity. At present, a squalene-containig adjuvant\u00a0(i.e. MF59) is utilized in an influenza vaccine marketed in\u00a0Europe only.<\/p>\n
<\/p>\n
Reference:<\/h4>\n
Franco Giovanetti. Travel Medicine and Infectious Disease (2007) 5, 7\u201317<\/p>\n","protected":false},"excerpt":{"rendered":"
It is estimated that worldwide international arrivals by any\u00a0form of transport have been around 763 million in 2004.\u00a0Such increased mobility involves all kind of travellers\u00a0(tourists, workers, businessmen) and all age […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[20],"tags":[370,369],"_links":{"self":[{"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/posts\/580"}],"collection":[{"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/comments?post=580"}],"version-history":[{"count":1,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/posts\/580\/revisions"}],"predecessor-version":[{"id":581,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/posts\/580\/revisions\/581"}],"wp:attachment":[{"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/media?parent=580"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/categories?post=580"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bocsci.com\/blog\/wp-json\/wp\/v2\/tags?post=580"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}