Heterogeneity in Plasmodium falciparum whole sporozoite vaccine induced humoral immune responses and protection in African volunteers: The role of age, human pegivirus and human immunodeficiency virus co-infections.

Malaria, a vector borne disease caused by Plasmodium species remains a major public health problem especially in sub-Saharan Africa. In 2018 alone, there were an estimated 228 million clinical cases and 405,000 deaths attributed to malaria. New tools such as efficacious vaccines, better drugs and diagnostics are needed to supplement the current malaria control tools that rest mainly on vector control measures. Clinical trials in malaria naïve volunteers have demonstrated high level of sterile vaccine induced protection in healthy individuals immunized with live, metabolically active, irradiation attenuated purified sporozoites (PfSPZ Vaccine) or live non-attenuated purified sporozoites given under chloroquine chemoprophylaxis (PfSPZ-CVac). Immunogenicity and protective efficacy against malaria induced by these whole sporozoite based vaccines varies widely between European/US versus African volunteers. Interestingly, variations in protection and immunogenicity of these malaria vaccines have been observed among African volunteers residing in different malaria endemic regions of East and West Africa. These different outcomes could be linked to levels of malaria pre-exposure and co-infections at the time of vaccination. Until recently safety, tolerability, immunogenicity and protective efficacy of PfSPZ Vaccine in immunocompromised populations including individuals infected with the Human Immunodeficiency Virus (HIV) was unknown. Given the high geographical overlap of HIV and malaria, an effective malaria vaccine deployed in this population could possibly support the long-term objective of regional elimination of malaria by using mass vaccination. Furthermore, the role of asymptomatic, under researched, highly prevalent viruses like Human Pegivirus (HPgV-1) circulating in Sub-Saharan Africa on malaria pathogenesis and vaccination outcomes remains elusive. The aims of this PhD thesis include: 1) Evaluate the safety, tolerability, efficacy, and immunogenicity of the PfSPZ Vaccine in different populations and age groups residing in malaria endemic countries. 2) Compare the safety, tolerability, efficacy, and immunogenicity of two different whole sporozoite based vaccination approaches, PfSPZ Vaccine and PfSPZ-CVac in Equatorial Guinean adults. 3) The unbiased assessment of PfSPZ Vaccine induced humoral immunity using protein microarrays probed with serum samples of HIV positive and HIV negative volunteers to understand immune status before vaccination, immuno-dominance of vaccine induced antibody targets, and distinct antibody profiles that might be associated with vaccine-induced protection. 4) Investigate the interaction of chronic HPgV-1 co-infection on PfSPZ Vaccine induced humoral immunity and protection against homologous CHMI. These aims are structured around 6 manuscripts presented in this PhD thesis. Manuscript 1-3: Safety, immunogenicity, and efficacy of radiation attenuated whole sporozoite vaccine (PfSPZ Vaccine) in African populations of different ages In this chapter, we include the outcomes of clinical trials conducted in Bagamoyo, Tanzania. These trials for the first time i) evaluated the safety, immunogenicity and efficacy against homologous CHMI of irradiation attenuated purified Plasmodium falciparum sporozoites (PfSPZ Vaccine) in adult volunteers; ii) tested increasing dosages of PfSPZ Vaccine in different age groups including adults, adolescents, children and infants. We found PfSPZ vaccine to be safe and well tolerated and that vaccine inoculation by intravenous inoculation is well accepted even in younger age groups. Protective efficacy varied in the different trials leading to the identification of a vaccine regimen of 9x105PfSPZ per dose as suitable for further development. PfSPZ Vaccine induce immune responses, both cellular and humoral, were age dependent with infants mounting no measurable malaria specific cellular immunity in peripheral blood. Surprisingly, compared to other age groups, older children and adolescents mounted higher cellular and humoral immune responses. These findings are relevant for further optimization of PfSPZ vaccine regimen that might need to be adapted to different age groups to optimize vaccine induced protection. As an extension of these trials, we have compared PfSPZ Vaccine safety, immunogenicity and efficacy in HIV positive versus HIV negative volunteers. We observed marked differences in PfSPZ Vaccine induced efficacy between HIV positive (0%) and HIV negative individuals (80%) undergoing homologous CHMI(Manuscript in preparation). Manuscript 4: Immunogenicity and protective efficacy of radiation-attenuated and chemo-attenuated PfSPZ vaccines in Equatoguinean adults This work describes the outcome of a first time side-by-side comparison of two whole sporozoite based vaccine approaches (PfSPZ Vaccine and PfSPZCVac) in malaria pre-exposed individuals of Equatorial Guinea. We evaluated PfSPZ Vaccine dosages (2.7 X106) given three times at 8-week interval and PfSPZ CVac dose (1X105) given three times at 4 weeks interval. Homologous CHMI was employed for assessment of vaccine efficacy. Both approaches were safe and well tolerated in malaria pre-exposed individuals but the immunogenicity and protective efficacy differed. Vaccine efficacy was lower in the PfSPZ Vaccine group (27%) compared to the PfSPZ CVac group (55%), despite induction of about 2.9 times higher antibody titres against the circumsporozoite protein in the PfSPZ Vaccine group prior to CHMI. These results highlight the potential involvement of different protective immune mechanisms induced by each of the two whole sporozoite vaccines approaches and the effect of malaria pre-exposure on pfSPZ CVac vaccine induced efficacy in comparison to malaria naïve volunteers. We show that induction of high antibody titres against the circumsporozoite protein does not correlate with protection since no difference was observed between CHMI protected and non-protected volunteers. Manuscript 5: HIV-1 positive and HIV-1 negative Tanzanian adults undergoing whole irradiation attenuated Plasmodium falciparum sporozoite vaccination mount antibody responses targeting the circumsporozoite protein and merozoite surface protein 5 In this manuscript, we investigated antibody profiles binding to 262 pre-selected antigens of Pf before and after vaccination as well as after homologus CHMI. We aimed to identify antibody profiles that might explain the observed poor vaccine induced protection in HIV positive individuals. We found a lower - albeit not statistically significant - antigen breadth in HIV positive volunteers at baseline before first vaccine inoculation. Immunization with PfSPZ Vaccine induced IgG and IgM isotypes specific for the Merozoite surface protein 5 (PfMSP 5) and the circumsporozoite protein (PfCSP) regardless of HIV infection status. Interestingly, volunteers displayed a highly personalized IgG and IgM immune profiles targeting Pf antigens before vaccination and these remained unchanged after PfSPZ vaccination confirming our previous results of antigenic imprinting in malaria. Manuscript 6: Role of Pegivirus infections in whole Plasmodium falciparum sporozoite vaccine induced humoral immunity and controlled human malaria infections in African volunteers In this study, we wanted to understand the role of human pegivirus infections in East and Western African adult volunteers and its impact on PfSPZ Vaccine induced humoral immune responses and homologous CHMI. We found HPgV-1 to be highly prevalent in our volunteers (29.2%) with circulating genotypes 1, 2 and 5 as described in other African settings. HPgV-1 infection did not alter PfSPZ vaccine induced antibody responses and parasite multiplication rates during CHMI. However, a higher proportion of individuals were protected against homologous CHMI that had ongoing, active human pegivirus infections. Significantly higher serum concentrations of IL-2 and IL-17A were measured in HPgV-1 positive volunteers likely indicating chronic activation of the immune system. CHMI was safe and well tolerated in HPgV-1 positive individuals since the viremia did not change upon acute asexual blood stage parasitemia. These results highlight the potential impact of chronic, asymptomatic viral infections on PfSPZ vaccine efficacy that needs confirmation in larger cohorts and in field studies of naturally occurring malaria infections

Red blood cell indices and\ud Prevalence of Hemoglobinopathies and Glucose 6 Phosphate Dehydrogenase Deficiencies in Male Tanzanian Residents of Dar es Salaam

Hemoglobinopathies, disorders of hemoglobin structure and production, are one of the most common monogenic disorders in humans. Glucose 6 phosphate dehydrogenase deficiency (G6PD) is an inherited enzymopathy resulting in increased oxygen stress susceptibility of red blood cells. The distributions of these genetic traits in populations living in tropical and subtropical regions where malaria has been or is still present are thought to result from survival advantage against severe life threatening malaria disease. 384 male Tanzanian volunteers residing in Dar es Salaam were typed for G6PD, sickle cell disease and α-thalassemia. The most prominent red blood cell polymorphism was heterozygous α+-thalassemia (37.8%), followed by the G6PD(A) deficiency (16.4%), heterozygous sickle cell trait (15.9%), G6PD(A-) deficiency (13.5%) and homozygous α+-thalassemia (5.2%). 35%, 45%, 17% and 3% of these volunteers were carriers of wild type gene loci, one, two or three of these hemoglobinopathies, respectively. We find that using a cut off value of 28.6 pg. for mean corpuscular hemoglobin (MCH), heterozygous α+-thalassemia can be predicted with a sensitivity of 84% and specificity of 72% in this male population. All subjects carrying homozygous α+-thalassemia were identified based on their MCH value < 28.6 pg

Los extranjeros en el marco de la normativa laboral de la Unión Europea

La acción de la Unión Europea en la gestión de flujos migratorios ha estado, en los últimos años, encaminada a conseguir la armonización de las políticas de inmigración de sus Estados miembros, tarea que hasta ahora ha sido ardua y complicada, pues ello significa atravesar las fronteras de la soberanía nacional de cada país, y es este el factor preponderante por el cual actualmente no existe una política europea común en este ámbito. En este sentido, la política de inmigración tiene su piedra angular en la admisión de inmigrantes económicos y por tanto es necesario abordarla a nivel europeo en el contexto del desarrollo progresivo de una política común de inmigración coherente, una responsabilidad que reside en la cooperación de todos los Estados miembros. Así, el presente trabajo es un acercamiento a los instrumentos jurídicos existentes a nivel de la UE y a la situación actual.Graduado o Graduada en Relaciones Laborales y Recursos Humanos por la Universidad Pública de NavarraLan Harremanetan eta Giza Baliabideetan Graduatua Nafarroako Unibertsitate Publikoa

Red blood cell indices and prevalence of hemoglobinopathies and glucose 6 phosphate dehydrogenase deficiencies in male Tanzanian residents of Dar es Salaam

Hemoglobinopathies, disorders of hemoglobin structure and production, are one of the most common monogenic disorders in humans. Glucose 6 phosphate dehydrogenase deficiency (G6PD) is an inherited enzymopathy resulting in increased oxygen stress susceptibility of red blood cells. The distributions of these genetic traits in populations living in tropical and subtropical regions where malaria has been or is still present are thought to result from survival advantage against severe life threatening malaria disease. 384 male Tanzanian volunteers residing in Dar es Salaam were typed for G6PD, sickle cell disease and α-thalassemia. The most prominent red blood cell polymorphism was heterozygous α(+)-thalassemia (37.8%), followed by the G6PD(A) deficiency (16.4%), heterozygous sickle cell trait (15.9%), G6PD(A-) deficiency (13.5%) and homozygous α(+)-thalassemia (5.2%). 35%, 45%, 17% and 3% of these volunteers were carriers of wild type gene loci, one, two or three of these hemoglobinopathies, respectively. We find that using a cut off value of 28.6 pg. for mean corpuscular hemoglobin (MCH), heterozygous α(+)-thalassemia can be predicted with a sensitivity of 84% and specificity of 72% in this male population. All subjects carrying homozygous α(+)-thalassemia were identified based on their MCH value < 28.6 pg

Safety and differential antibody and T-cell responses to Plasmodium falciparum sporozoite vaccine by age in Tanzanian adults, adolescents, children, and infants

In 2016, there were more cases and deaths caused by malaria globally than in 2015. An effective vaccine would be an ideal additional tool for reducing malaria's impact. Sanaria; ®; PfSPZ Vaccine, composed of radiation-attenuated, aseptic, purified, cryopreserved; Plasmodium falciparum; (Pf) sporozoites (SPZ) has been well tolerated and safe in malaria-naïve and experienced adults in the United States and Mali and protective against controlled human malaria infection with Pf in the United States and field transmission of Pf in Mali, but had not been assessed in younger age groups. We, therefore, evaluated PfSPZ Vaccine in 93 Tanzanians aged 45 years to 6 months in a randomized, double-blind, normal saline placebo-controlled trial. There were no significant differences in adverse events between vaccinees and controls or between dosage regimens. Because all age groups received three doses of 9.0 × 10; 5; PfSPZ of PfSPZ Vaccine, immune responses were compared at this dosage. Median antibody responses against Pf circumsporozoite protein and PfSPZ were highest in infants and lowest in adults. T-cell responses were highest in 6-10-year olds after one dose and 1-5-year olds after three doses; infants had no significant positive T-cell responses. The safety data were used to support initiation of trials in &gt; 300 infants in Kenya and Equatorial Guinea. Because PfSPZ Vaccine-induced protection is thought to be mediated by T cells, the T-cell data suggest PfSPZ Vaccine may be more protective in children than in adults, whereas infants may not be immunologically mature enough to respond to the PfSPZ Vaccine immunization regimen assessed