Immunogenicity of Botulinum Toxin A: Insights.

BACKGROUND: Botulinum toxin A (BoNT-A) is widely used in treating dystonia and spasticity to managing chronic migraine and cosmetic applications. However, its immunogenic potential presents challenges, such as the development of neutralizing antibodies that lead to diminished therapeutic efficacy over time, known as secondary nonresponse. OBJECTIVE: This review aims to bridge the knowledge gap regarding the immunogenic mechanisms of BoNT-A and to explore effective management strategies to mitigate these immune responses. MATERIALS AND METHODS: The authors conducted a systematic search in databases including PubMed, Embase, and Web of Science, using keywords related to BoNT-A's immunogenicity. The selection process refined 157 initial articles down to 23 relevant studies, which underwent analysis to investigate the underlying mechanisms of immunogenicity and the factors influencing it. RESULTS: The analysis revealed that both the neurotoxin component and the neurotoxin-associated proteins could elicit an immune response. However, only antibodies against the core toxin influence therapeutic outcomes. Various patient-specific factors such as genetic predispositions and prior immune experiences, along with treatment-related factors such as dosage and frequency, play crucial roles in shaping these responses. CONCLUSION: Understanding the specific immunogenic triggers and responses to BoNT-A is critical for optimizing treatment protocols and improving patient outcomes.

Prevalence of neutralising antibodies in patients treated with botulinum toxin type A for spasticity.

Botulinum toxin (BT) has been used with great success to treat various muscle hyperactivity disorders. Occasionally, antibodies against BT (BT-AB) can be formed. When they are directed against the neurotoxin component of the BT drug, they are called neutralising antibodies. They can reduce the therapeutic effect partially or completely. We have measured neutralising BT-AB by use of the mouse diaphragm assay (MDA) in 42 adult patients with spasticity in the order of their appearance in the clinic. The patients had been treated for at least 2 years with BT type A (BT-A) and received on an average 14.2 +/- 6.1 BT-A injection series. BT-A was applied as Botox only, Dysport only or by sequential application of both preparations. The mean cumulative doses were 4,610 +/- 1,936 units Botox and 14,033 +/- 7,566 units Dysport, respectively. The mean treatment time was 4.5 +/- 1.8 (2-8) years. All patients were initially responsive to BT-A therapy. MDA detected BT-AB in 12% (5/42) of patients. However, in three patients the BT-AB titre was very low (<0.3 mIU/ml), in one it was intermediate (0.6 mIU/ml) and in one patient it was high (>1.0 mIU/ml). All BT-AB negative patients and also two of the patients with low BT-AB titre remained clinically responsive to BT therapy throughout the study. In conclusion, prevalence of BT-AB formation with clinical relevance (6%, 3/42) in adult patients with spasticity is not higher than that of BT-treated patients with cervical dystonia and much lower than that of BT-treated patients with infantile cerebral palsy.

Immunogenicity induced by botulinum toxin injections for limb spasticity: A systematic review.

BACKGROUND: The imputability of neutralizing antibodies (NABs) in secondary non-response (SnR) to botulinum toxin (BoNT) injections for limb spasticity is still debated. OBJECTIVE: This systematic literature review aimed to determine the prevalence of NABs after BoNT injections for limb spasticity and analyze their determinants and their causal role in SnR. METHODS: We searched MEDLINE via PubMed, Cochrane and Embase databases for articles published during 1990-2018. Two independent reviewers extracted the data and assessed the quality of studies with a specific scale (according to PRISMA and STROBE guidelines). Because the techniques used to detect NABs did not influence the results, we calculated the global (all studies) sensitivity and specificity of NAB positivity to reveal SnR. RESULTS: We included 14 articles published from 2002 to 2018 (including an epublication) describing 5 randomized controlled trials and 5 interventional and 4 observational studies. The quality was satisfactory (mean score 18/28 arbitrary units). NAB detection was the primary criterion in 5 studies and a secondary criterion in 9. In total, 1234 serum samples for 1234 participants (91% with stroke) were tested after injection. NAB prevalence was about 1%, with no significant difference among formulations. NAB positivity seemed favoured by long-duration therapy with high doses and a short interval between injections. The identification of non-response by NAB positivity had poor global sensitivity (56%) but very high specificity (99.6%). No consensual criteria were used to diagnose non-response to BoNT injection. CONCLUSIONS: NAB prevalence is much lower after BoNT treatment for limb spasticity than cervical dystonia. Consensual criteria must be defined to diagnose non-response to BoNT injection. Because immunogenicity is not the most common cause of non-response to BoNT injection, NABs should be sought in individuals with SnR with no other cause explaining the treatment inefficacy. A test with 100% specificity is recommended. In cases for which immunogenicity is the most likely cause of non-response to BoNT injections, some biological arguments suggest trying another BoNT, but no clinical evidence supports this strategy.

Immunization with neurofilament light protein induces spastic paresis and axonal degeneration in Biozzi ABH mice.

Axonal damage is the major cause of irreversible neurologic disability in patients with multiple sclerosis. Although axonal damage correlates with antibodies against neurofilament light (NF-L) protein, a major component of the axonal cytoskeleton, the possible pathogenic role of autoimmunity to axonal antigens such as NF-L has so far been ignored. Here we show that Biozzi ABH mice immunized with NF-L protein develop neurologic disease characterized by spastic paresis and paralysis concomitant with axonal degeneration and inflammation primarily in the dorsal column of the spinal cord. The inflammatory central nervous system lesions were dominated by F4/80+ macrophages/microglia and relatively low numbers of CD4+ and CD8+ T-cells. In splenocyte cultures, proliferation to NF-L was observed in CD4+ T-cells accompanied by the production of the proinflammatory cytokine interferon-gamma. Elevated levels of circulating antibodies recognizing recombinant mouse NF-L were present in the serum, and immunoglobulin deposits were observed within axons in spinal cord lesions of mice exhibiting clinical disease. These data provide evidence that autoimmunity to NF-L protein induces axonal degeneration and clinical neurologic disease in mice, indicating that autoimmunity to axonal antigens, as described in multiple sclerosis, may be pathogenic rather than acting merely as a surrogate marker for axonal degeneration.

Spasticity in multiple sclerosis: Contribution of inflammation, autoimmune mediated neuronal damage and therapeutic interventions.

In contrast to other diseases that go along with spasticity (e.g. spinal cord injury), spasticity in chronic autoimmune diseases involving the CNS is complicated by the ongoing damage of neuronal networks that leads to permanent changes in the clinical picture of spasticity. Multiple sclerosis (MS) is the most frequent autoimmune disease of the central nervous system (CNS) and spasticity is one of the most disabling symptoms. It occurs in more than 80% MS patients at some point of the disease and is associated with impaired ambulation, pain and the development of contractures. Besides causing cumulative structural damage, neuroinflammation occurring in MS leads to dynamic changes in motor circuit function and muscle tone that are caused by cytokines, prostaglandins, reactive oxygen species and stress hormones that affect neuronal circuits and thereby spasticity. The situation is complicated further by the fact that therapeutics used for the immunotherapy of MS may worsen spasticity and drugs used for the symptomatic treatment of spasticity have been shown to have the potential to alter immune cell function and CNS autoimmunity itself. This review summarizes the current knowledge on the immunologic pathways that are involved in the development, maintenance, dynamic changes and pharmacological modulation of spasticity in MS.

Human T-lymphotropic virus type I antibodies in the serum of patients with tropical spastic paraparesis in the Seychelles.

Tropical spastic paraparesis (TSP), a chronic myelopathy of unknown etiology, was studied in the Seychelles. Human T-lymphotropic virus type I (HTLV-I) and human immunodeficiency virus antibodies were determined using an enzyme-linked immunosorbent assay and confirmed with an indirect fluorescent antibody test in serum samples of 20 patients with TSP and 16 controls. Test results indicated that 17 patients (85%) and two controls (transverse myelopathy and clinically probable multiple sclerosis) were positive for HTLV-I. Serum samples of nine healthy controls and five with other neurologic diseases were negative for HTLV-I. No serum samples were positive for human immunodeficiency virus. Estimated relative risk for TSP in those subjects whose serum is positive for HTLV-I antibodies is 40. This result is highly statistically significant. Although primarily associated with adult T-cell leukemia and non-Hodgkin's lymphoma, HTLV-I could also be an etiologic agent of TSP.

Spastic paraparesis of obscure origin. A case-control study of HTLV-I positive and negative patients from Rio de Janeiro, Brazil.

In order to find clinical findings that could significantly discriminate between HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and HTLV-I negative spastic paraparesis of obscure origin (SPOneg) prior to serological testing, and to find risk factors significantly associated with HAM/TSP we devised a case-control study. Sixty consecutive SPO patients were studied without previous knowledge of their HTLV-I serological status. Thirty-four (56.7%) turned out to be HTLV-I positive and 26 (43.3%) HTLV-I negative. HTLV-I infected patients tended to have more commonly motor and bladder disturbances at the beginning of their illness and a disease that was still in progression at the time of the examination. Bladder dysfunction, constipation and penile impotence, and more widespread pyramidal signs, were also more frequent during the whole course of their illness. Likewise, an increased intrathecal synthesis of IgG was found more often in the HTLV-I positive group. The only risk factor for HTLV-I infection significantly associated to HAM/TSP was a prior history of sexually transmitted diseases. These results suggest that, at least in RJ, HAM/TSP might be mainly sexually acquired.

HTLV-I associated myelopathy/tropical spastic paraparesis in a 7-year-old boy associated with infective dermatitis.

HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic myelopathy characterized by a slowly progressive spastic paraparesis and sphincter disturbances beginning in adulthood. Only eight well-documented cases occurring in childhood and adolescence have been described. Infective dermatitis associated to the HTLV-I (IDH) is a chronic eczema of childhood occurring in vertically infected carriers. Here we describe a 7-year-old boy with HAM/TSP and IDH. The neurological manifestations were spastic gait, hyperreflexia of lower limbs, clonus and bilateral Babinski's sign. High levels of HTLV-I antibodies in the serum and in the cerebrospinal fluid were observed. The association of these two diseases and the early onset of HAM/TSP are probably related to a strong humoral anti-HTLV-I response.

[Tropical spastic paraparesis in Martinique. High prevalence of anti-HTLV-I antibodies]. / Paraparésies spastiques tropicales en Martinique. Haute prévalence d'anticorps HTLV-I.

Owing to the frequent occurrence in tropical countries of subacute spinal cord diseases of unknown origin, a nosological entity called tropical spastic paraparesis has been individualized. Twenty-two cases have been observed in Martinique. The presence in the serum of antibodies directed against human T-cell leukaemia/lymphoma virus (HTLV-I) in 15 of these 22 patients suggests that this lymphotropic virus or a related one might also be neurovirulent.

Neutralizing antibodies and secondary therapy failure after treatment with botulinum toxin type A: much ado about nothing?

OBJECTIVES: As the indications and duration of treatment of botulinum toxin type A (BoNT-A) increase, so do reports of patients who fail therapy after initially responding well. Although a loss of efficacy is commonly thought to be associated with neutralizing antibodies (NAbs), this relationship is not strongly correlated, and other factors may play a significant role. To explore this issue, we evaluated levels of NAbs in a large selected cohort of secondary nonresponders to BoNT-A using the highly sensitive mouse phrenic nerve-hemidiaphragm assay. METHODS: Serum samples from 503 patients treated with BoNT-A who had a variety of diagnoses were tested for the presence of NAbs. RESULTS: Fewer than half of the patients (n = 224, 44.5%) were found to be NAb-positive, indicating that in more than half of the secondary nonresponders, lack of efficacy is not due to NAb formation. The proportion of secondary nonresponders with NAbs was greater for higher dose indications (focal spasticity and spasmodic torticollis) than for lower dose indications (blepharospasm and hemifacial spasm) and increased with shorter injection intervals. Neutralizing antibody development was independent of the commercial preparation used. CONCLUSIONS: Our results indicate that although NAb formation does play a role in secondary treatment failure with BoNT-A, this is not the cause in all patients, and the influence of other factors needs to be investigated. Gaining a better understanding of the underlying mechanisms for secondary treatment failure may help in the prediction, diagnosis, management, and prevention of this problem.

Immunological findings in neurological diseases associated with antibodies to HTLV-I: activated lymphocytes in tropical spastic paraparesis.

A retrovirus involvement in the etiology of certain neurological diseases is currently an area of intense interest. Tropical spastic paraparesis and other chronic progressive myelopathies have been clearly associated with increased serum and cerebrospinal fluid antibody titers to human T-lymphotropic virus type I; however, little is known about the cellular immune response. In the present study, activated T-lymphocytes were found in the peripheral blood of patients with this disorder. There were increased numbers of large CD3-positive cells that also expressed histocompatibility leukocyte Class II (DR) and interleukin 2-receptor molecules. In addition, a significantly elevated spontaneous lymphoproliferative response was demonstrated in all patients. This is consistent with the known in vitro effects of human T-lymphotropic virus type I. In one patient, a defect in the generation of measles virus-specific cytotoxic T cells was identified. These observations indicate abnormalities of the cellular immune response in tropical spastic paraparesis.

Antibody to human and simian retrovirus, HTLV-I, HTLV-II, HIV, STLV-III, and SRV-I not increased in patients with multiple sclerosis.

We have tested sera from patients with multiple sclerosis, matched controls, and those with other neurological diseases, as well as sera from patients with the acquired immunodeficiency syndrome and controls and patients with tropical spastic paraparesis (TSP) and controls for antibody to human T-lymphotropic virus type I (HTLV-I), HTLV-II, human immunodeficiency virus (HIV), simian T-lymphotropic virus type III, or simian retrovirus type I by immunofluorescent activity test, and for HTLV-I and HIV by the ELISA method. Sera from patients with multiple sclerosis and matched controls, and from patients with optic neuritis and Parkinson's or other neuromuscular diseases did not have antibody to any of the retroviruses tested. Specimens from TSP patients and some controls contained HTLV-I antibody. We conclude from our study that only TSP patients had serological evidence of infection with one of the retroviruses studied.

HTLV-I, adult T-cell leukemia, and tropical spastic paraparesis.

Human lymphotropic retroviruses have been identified as the etiological agents of adult T-cell leukemia and acquired immunodeficiency syndrome (AIDS). Human T-lymphotropic virus type I (HTLV-I) has been linked to the etiology of ATL, and human immunodeficiency virus type I (HIV-1) has been identified as the cause of AIDS. Both retroviruses are T-cell tropic. HTLV-I is a transforming virus, whereas HIV-1 is a cytopathic virus and kills the cells it infects. HTLV-I has recently been identified from some patients with tropical spastic paraparesis, and it appears that HTLV-I infection alone or in the presence of other cofactors may be important in the development of this neurological dysfunction.

Antibody to human T-lymphotropic virus type 1 in West-Indian-born UK residents with spastic paraparesis.

Of 13 West-Indian-born UK residents with spastic paraparesis of unknown cause, 11 were tested for serum antibody to human T-cell lymphotropic virus type 1 and all were positive. Their magnetic resonance imaging scans were normal or showed only minor abnormalities in the brain, and the spinal cord was normal in the 5 investigated. Of 48 patients with multiple sclerosis, mainly caucasian, none had antibody to HTLV-1 in the blood.

Endemic tropical spastic paraparesis associated with human T-lymphotropic virus type I: a clinical and seroepidemiological study of 25 cases.

Tropical spastic paraparesis (TSP) is a common myeloneuropathy with primary and predominant involvement of the pyramidal tract and minimal sensory loss. The epidemic form of TSP is related to toxic nutritional factors, but the endemic form occurs in clusters in tropical areas, especially in India, Africa, the Seychelles, Colombia, and areas of the Caribbean. We describe the clinical and epidemiological features of 25 TSP patients from Martinique (French West Indies) with serum antibodies to human T-lymphotropic virus type I (HTLV-I). Furthermore, all 11 patients who were seropositive for HTLV-I had specific HTLV-I antibodies in their CSF. All were women. The age of onset varied from 25 to 60 years (mean, 45 years). The main clinical features are spastic paraparesis or paraplegia with spasticity of the upper limbs, minimal sensory loss, and bladder dysfunction. Minimal estimated incidence and prevalence are 1 per 100,000 inhabitants per year and 8 per 100,000, respectively. Seventeen percent of the relatives of patients with HTLV-I-associated TSP have HTLV-I antibodies (1 husband and 7 children). In Martinique, the prevalence of HTLV-I antibodies in the general population is about 2% and reaches 10% for neurological disorders other than TSP. Since our initial report, the association between spastic paraparesis and HTLV-I has been confirmed in Jamaica, Colombia, and Japan, suggesting the neurotropism of this lymphotropic human retrovirus.

The role of HTLV-I in tropical spastic paraparesis in Jamaica.

We report clinical and laboratory investigations of 47 native-born Jamaican patients with endemic tropical spastic paraparesis and of 1 patient with tropical ataxic neuropathy. Mean age at onset was 40 years, with a female-male preponderance (2.7:1). Neurological features of endemic tropical spastic paraparesis are predominantly those of a spastic paraparesis with variable degrees of proprioceptive and/or superficial sensory impairment. Using enzyme-linked immunoabsorbent assay (ELISA), IgG antibodies to human T-lymphotropic virus type I (HTLV-I) were present in 82% of sera and 77% of cerebrospinal fluids. On Western blot analysis, IgG antibodies detected the p19 and p24 gag-encoded core proteins in both serum and cerebrospinal fluid. Titers were tenfold higher by ELISA in serum than in cerebrospinal fluid, and some oligoclonal bands present in fluid were not seen in serum. Serum-cerebrospinal fluid albumin ratios were normal, and IgG indexes indicated intrathecal IgG synthesis. Histopathological changes showed a chronic inflammatory reaction with mononuclear cell infiltration, perivascular cuffing, and demyelination that was predominant in the lateral columns. In 1 patient, a retrovirus morphologically similar to HTLV-I on electron microscopy was isolated from spinal fluid. Our investigations show that endemic tropical spastic paraparesis in Jamaica is a retrovirus-associated myelopathy and that HTLV-I or an antigenically similar retrovirus is the causal agent.

Pathological and immunological observations on tropical spastic paraparesis in patients from Jamaica.

The neuropathological examination of the spinal cord of 2 Jamaican patients with classical tropical spastic paraparesis disclosed an intense chronic meningomyelitis with demyelination. In the 1 case in which serum and cerebrospinal fluid were available, antibodies to the human T-lymphotropic virus type 1 were found.