Dirk E. Teuwen

The Yellow Fever Virus Vaccine Induces a Broad and Polyfunctional Human Memory CD8+ T Cell Response

The live yellow fever vaccine (YF-17D) offers a unique opportunity to study memory CD8+ T cell differentiation in humans following an acute viral infection. We have performed a comprehensive analysis of the virus-specific CD8+ T cell response using overlapping peptides spanning the entire viral genome. Our results showed that the YF-17D vaccine induces a broad CD8+ T cell response targeting several epitopes within each viral protein. We identified a dominant HLA-A2-restricted epitope in the NS4B protein and used tetramers specific for this epitope to track the CD8+ T cell response over a 2 year period. This longitudinal analysis showed the following. 1) Memory CD8+ T cells appear to pass through an effector phase and then gradually down-regulate expression of activation markers and effector molecules. 2) This effector phase was characterized by down-regulation of CD127, Bcl-2, CCR7, and CD45RA and was followed by a substantial contraction resulting in a pool of memory T cells that re-expressed CD127, Bcl-2, and CD45RA. 3) These memory cells were polyfunctional in terms of degranulation and production of the cytokines IFN-γ, TNF-α, IL-2, and MIP-1β. 4) The YF-17D-specific memory CD8+ T cells had a phenotype (CCR7−CD45RA+) that is typically associated with terminally differentiated cells with limited proliferative capacity (TEMRA). However, these cells exhibited robust proliferative potential showing that expression of CD45RA may not always associate with terminal differentiation and, in fact, may be an indicator of highly functional memory CD8+ T cells generated after acute viral infections.

Yellow fever vaccine — how does it work and why do rare cases of serious adverse events take place?

Yellow fever 17D vaccine is one of the most successful vaccines ever developed and over 540 million doses have been used. Nevertheless there has been very little known about the mechanism of protection induced by the vaccine. The last couple of years have seen important advances made in understanding how the vaccine works involving studies of the innate and adaptive immune responses plus a systems biology approach. Like all vaccines, the 17D vaccine causes rare serious adverse events (SAEs) following immunization. At present, the mechanism(s) of SAEs is(are) poorly understood but our advances in understanding the immune response induced by the vaccine have promise to help elucidate the mechanism of SAEs.

Case of Yellow Fever Vaccine-associated Viscerotropic Disease with Prolonged Viremia, Robust Adaptive Immune Responses, and Polymorphisms in CCR5 and RANTES Genes

BACKGROUND The live attenuated yellow fever vaccine 17D (YF-17D) is one of the most effective vaccines. Despite its excellent safety record, some cases of viscerotropic adverse events develop, which are sometimes fatal. The mechanisms underlying such events remain a mystery. Here, we present an analysis of the immunologic and genetic factors driving disease in a 64-year-old male who developed viscerotropic symptoms. METHODS We obtained clinical, serologic, virologic, immunologic and genetic data on this case patient. RESULTS Viral RNA was detected in the blood 33 days after vaccination, in contrast to the expected clearance of virus by day 7 after vaccination in healthy vaccinees. Vaccination induced robust antigen-specific T and B cell responses, which suggested that persistent virus was not due to adaptive immunity of suboptimal magnitude. The genes encoding OAS1, OAS2, TLR3, and DC-SIGN, which mediate antiviral innate immunity, were wild type. However, there were heterozygous genetic polymorphisms in chemokine receptor CCR5, and its ligand RANTES, which influence the migration of effector T cells and CD14+CD16bright monocytes to tissues. Consistent with this, there was a 200-fold increase in the number of CD14+CD16bright monocytes in the blood during viremia and even several months after virus clearance. CONCLUSION In this patient, viscerotropic disease was not due to the impaired magnitude of adaptive immunity but instead to anomalies in the innate immune system and a possible disruption of the CCR5-RANTES axis.

Immune Response during Adverse Events after 17D-Derived Yellow Fever Vaccination in Europe

BACKGROUND In 1999-2000, reports of fatalities after vaccination with 17D-derived yellow fever vaccine (YEL) focused mainly on cases of YEL-associated adverse events (YEL-AEs) and YEL-associated viscerotropic disease (YEL-AVD). Here, we investigated 6 recent European cases to provide insight regarding immune response involvement and to identify potential risk factors. METHODS Clinical, microbiological, molecular biological, and immunological assays were performed on serum from 6 patients with YEL-AEs, including 5 with YEL-AVD and 1 with YEL-associated neurotropic disease (YEL-AND). RESULTS The levels of 3 liver enzymes associated with infection were clearly increased in all patients with YEL-AVD, but no elevations were observed in the patient with YEL-AND. In the patients with severe YEL-AVD, platelet counts were markedly reduced (< 100,000 cells/microL). The only patient with fatal YEL-AVD exhibited a cytokine profile comparable to that seen in YF: high levels of interleukin (IL)-6, IL-8, monocyte chemotactic protein (MCP)-1, monokine induced by interferon-gamma, and growth-related oncogene (GRO). The other patients with YEL-AVD exhibited similar but less severe cytokine profiles. The patient with YEL-AND exhibited a cytokine profile similar to that found in vaccinees without YEL-AEs: elevated levels of RANTES and low levels of GRO, MCP-1, transforming growth factor-beta1, and tumor necrosis factor-beta. CONCLUSIONS On the basis of these results, we conclude that elevations in cytokine levels and reductions in platelet counts are suitable surrogate markers for patients likely to experience severe adverse reactions to YEL.

Rabies Post-Exposure Prophylaxis in the Philippines: Health Status of Patients Having Received Purified Equine F(ab')2 Fragment Rabies Immunoglobulin (Favirab)

Background Recommended treatment for severe rabies exposure in unvaccinated individuals includes wound cleaning, administration of rabies immunoglobulins (RIG), and rabies vaccination. We conducted a survey of rabies treatment outcomes in the Philippines. Methods This was a case series involving 7,660 patients (4 months to 98 years of age) given purified equine RIG (pERIG) at the Research Institute for Tropical Medicine (Muntinlupa, Philippines) from July 2003 to August 2004 following Category II or III exposures. Data on local and systemic adverse reactions (AR) within 28 days and biting animal status were recorded; outcome data were obtained by telephone or home visit 6–29 months post-exposure. Results Follow-up data were collected for 6,464 patients. Of 151 patients with laboratory-confirmed rabies exposure, 143 were in good health 6–48 months later, seven could not be contacted, and one 4-year-old girl died. Of 16 deaths in total, 14 were unrelated to rabies exposure or treatment. Two deaths were considered PEP failures: the 4-year old girl, who had multiple deep lacerated wounds from a rabid dog of the nape, neck, and shoulders requiring suturing on the day of exposure, and an 8-year-old boy who only received rabies PEP on the day of exposure. Conclusions This extensive review of outcomes in persons with Category III exposure shows the recommended treatment schedule at RITM using pERIG is well tolerated, while survival of 143 laboratory-confirmed rabies exposures confirms the intervention efficacy. Two PEP intervention failures demonstrate that sustained education and training is essential in rabies management.

A Randomized, Double-Blind, Controlled Trial of the 17D Yellow Fever Virus Vaccine Given in Combination with Immune Globulin or Placebo: Comparative Viremia and Immunogenicity

We evaluated whether coadministration of the yellow fever (YF) virus vaccine with human immunoglobulin (Ig) that contained YF virus-neutralizing antibodies would reduce post-vaccination viremia without compromising immunogenicity and thus, potentially mitigate YF vaccine-associated adverse events. We randomized 80 participants to receive either YF vaccine and Ig or YF vaccine and saline placebo. Participants were followed for 91 days for safety and assessments of viremia and immunogenicity. There were no differences found between the two groups in the proportion of vaccinated participants who developed viremia, seroconversion, cluster of differentiation (CD)-8(+) and CD4(+) T-cell responses, and cytokine responses. These results argue against one putative explanation for the increased reporting of YF vaccine side effects in recent years (i.e., a change in travel clinic practice after 1996 when hepatitis A prophylaxis with vaccine replaced routine use of pre-travel Ig, thus potentially removing an incidental YF vaccine-attenuating effect of anti-YF virus antibodies present in Ig).

Rabies post-exposure prophylaxis with purified equine rabies immunoglobulin: one-year follow-up of patients with laboratory-confirmed category III rabies exposure in the Philippines.

Category III rabies post-exposure prophylaxis (PEP) encompasses wound cleansing, infiltration of rabies immunoglobulins (RIG) and rabies vaccination. A Manila-based prospective prescription monitoring one-year follow-up study enrolled 193 patients, aged 16 months-79 years. Patients received PEP, including infiltration of highly purified equine RIG (pERIG, Favirab), following exposure to animals confirmed rabid by direct fluorescence antibody test (dFAT). No serious adverse events were considered related to PEP. One-year post-exposure, 191 of the 193 patients (99%) were in good health. Two deaths occurred, one due to myocardial infarction (unrelated to rabies) in a 73-year-old man, 291 days post-exposure, and one due to rabies infection in a six-year-old boy, 28 days post-exposure. The results show the recommended PEP treatment is highly effective. The single rabies fatality demonstrates the importance of ensuring immediate and complete application of recommended PEP, sustained education and training in rabies management.

Addressing the treatment gap and societal impact of epilepsy in Rwanda--Results of a survey conducted in 2005 and subsequent actions.

This study, supported by the Rwandan Ministry of Health and the World Health Organization, was conducted in 2005 to determine the prevalence of epilepsy and its sociocultural perception in Rwanda, as well as epilepsy-related knowledge and practices of health-care professionals (HCPs). A cross-sectional, nationally representative survey was conducted throughout Rwanda by trained investigators. Participants were recruited by random cluster sampling based on the organization of administrative units in the country. Overall, 1137 individuals (62% from rural areas) were interviewed. The prevalence of epilepsy was estimated to be 49 per 1000 people or 41 per 1000 for active epilepsy. Onset of epilepsy before the age of 2 years was reported in 32% of the cases. Family history of epilepsy, head trauma, and premature delivery were reported in 53%, 50%, and 68% of the cases, respectively. Most (68%) patients did not receive any medical treatment for epilepsy; 21.5% had received some form of traditional treatment. According to responses from the general population, people with epilepsy should not be entitled to schooling (according to 66%), to work (according to 72%), to the use of public places (according to 69%), or to marriage (according to 66%). Furthermore, 50% believed that epilepsy was untreatable, and 40% thought that it was transmissible. Of the 29 HCPs interviewed, the majority knew the definition of epilepsy and status epilepticus, as well as basic treatment options and side effects. However, 90% believed that treatment was only necessary in the first week after a seizure. Living with epilepsy was associated heavily with stigma, and a significant treatment gap (68%) was identified. Following this study, numerous actions have been taken by the Rwandan government, the Rwandan League Against Epilepsy, and several nongovernmental organizations to increase awareness about epilepsy and to close the treatment gap. An overview of these activities is provided.

Comorbidity of Cerebral Palsy, the Cyst of the Corpus Callosum, Parenchymal Cyst, Epilepsy and Cardiac Disease: About an Observation

Motor impairment of cerebral origin is a syndrome that induces a reduction in activity, the origin of which is brain injury or a non-progressive and definitive abnormality occurring in a developing immature brain. Motor disability, spastic, dyskinetic or ataxic, is often associated with sensory, cognitive, sensory and behavioral disorders with or without epileptic disease. View of accidental discoveries of corpus callosum abnormalities, most often asymptomatic or associated with psychomotor retardation, epilepsy, neurological disorders or cardiomyopathy, a high technical platform must be available for its diagnosis. We report in this article the case of a 7-year-old boy followed at the neuropsychiatric center Joseph Guislain of the Brothers of Charity of Lubumbashi in Congo (DRC) since 2016 for generalized tonic-clonic seizures, in whom the diagnosis of cerebral palsy on cyst of corpus callosum and in the right parietal lobe, as well as cardiopathy was posed during its consultation in September 2017. This case was published with parental consent.