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Background: Infections with Plasmodium ovale are widely distributed but rarely investigated, and the resulting burden of disease has been underestimated. Plasmodium ovale curtisi Duffy binding protein domain region II (PocDBP-RII) is an essential ligand for reticulocyte recognition and host cell invasion by P. ovale curtisi. However, the genomic variation, antigenicity and immunogenicity of PocDBP-RII remain major knowledge gaps. Methods: A total of 93 P. ovale curtisi samples were collected from migrant workers who returned to China from 17 countries in Africa between 2012 and 2016. The genetic polymorphism, natural selection and copy number variation (CNV) were investigated by sequencing and real-time PCR. The antigenicity and immunogenicity of the recombinant PocDBP-RII (rPocDBP-RII) protein were further examined, and the humoral and cellular responses of immunized mice were assessed using protein microarrays and flow cytometry. Results: Efficiently expressed and purified rPocDBP-RII (39 kDa) was successfully used as an antigen for immunization in mice. The haplotype diversity (Hd) of PocDBP-RII gene was 0.105, and the nucleotide diversity index (π) was 0.00011. No increased copy number was found among the collected isolates of P. ovale curtisi. Furthermore, rPocDBP-RII induced persistent antigen-specific antibody production with a serum IgG antibody titer of 1: 16,000. IFN-γ-producing T cells, rather than IL-10-producing cells, were activated in response to the stimulation of rPocDBP-RII. Compared to PBS-immunized mice (negative control), there was a higher percentage of CD4+CD44highCD62L− T cells (effector memory T cells) and CD8+CD44highCD62L+ T cells (central memory T cells) in rPocDBP-RII‑immunized mice. Conclusions: PocDBP-RII sequences were highly conserved in clinical isolates of P. ovale curtisi. rPocDBP-RII protein could mediate protective blood-stage immunity through IFN-γ-producing CD4+ and CD8+ T cells and memory T cells, in addition to inducing specific antibodies. Our results suggested that rPocDBP-RII protein has potential as a vaccine candidate to provide assessment and guidance for malaria control and elimination activities. [ABSTRACT FROM AUTHOR]

A novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in China in 2019 and later ignited a global pandemic. Contrary to expectations, the effect of the pandemic was not as devastating to Africa and its young population compared to the rest of the world. To provide insight into the possible reasons for the presumed immune sufficiency to coronavirus disease 2019 (COVID-19) in Africa, this review critically examines literature published from 2020 onwards on the dynamics of COVID-19 infection and immunity and how other prevalent infectious diseases in Africa might have influenced the outcome of COVID-19. Studies characterising the immune response in patients with COVID-19 show that the correlates of protection in infected individuals are T-cell responses against the SARS-CoV-2 spike protein and neutralising titres of immunoglobin G and immunoglobin A antibodies. In some other studies, substantial pre-existing T-cell reactivity to SARS-CoV-2 was detected in many people from diverse geographical locations without a history of exposure. Certain studies also suggest that innate immune memory, which offers protection against reinfection with the same or another pathogen, might influence the severity of COVID-19. In addition, an initial analysis of epidemiological data showed that COVID‑19 cases were not severe in some countries that implemented universal Bacillus Calmette–Guerin (BCG) vaccination policies, thus supporting the potential of BCG vaccination to boost innate immunity. The high burden of infectious diseases and the extensive vaccination campaigns previously conducted in Africa could have induced specific and non-specific protective immunity to infectious pathogens in Africans. [ABSTRACT FROM AUTHOR]

The pattern of epidemic meningococcal disease in the African meningitis belt may be influenced by the background level of population immunity but this has been measured infrequently. A standardised enzyme-linked immunosorbent assay (ELISA) for measuring meningococcal serogroup A IgG antibodies was established at five centres within the meningitis belt. Antibody concentrations were then measured in 3930 individuals stratified by age and residence from six countries. Seroprevalence by age was used in a catalytic model to determine the force of infection. Meningococcal serogroup A IgG antibody concentrations were high in each country but showed heterogeneity across the meningitis belt. The geometric mean concentration (GMC) was highest in Ghana (9.09 μg/mL [95% CI 8.29, 9.97]) and lowest in Ethiopia (1.43 μg/mL [95% CI 1.31, 1.57]) on the margins of the belt. The force of infection was lowest in Ethiopia (λ = 0.028). Variables associated with a concentration above the putative protective level of 2 μg/mL were age, urban residence and a history of recent vaccination with a meningococcal vaccine. Prior to vaccination with the serogroup A meningococcal conjugate vaccine, meningococcal serogroup A IgG antibody concentrations were high across the African meningitis belt and yet the region remained susceptible to epidemics.

This study aimed to evaluate the durability of the immunogenicity of MVA85A beyond infancy. Participants in an immunogenicity study of MVA85A administered at age of 4 months had additional evaluation 14 months after initial vaccination for IFN-γ ELISPOT responses to Ag85A peptide and ESAT6/CFP-10 and tuberculin skin test (TST). 112 children participated in this study. The anthropometry, biochemical and haematological safety profile were similar between the MVA85A recipients and controls. MVA85A recipients still had significantly higher immune responses to Ag85A compared to the controls. The majority of these children had negative responses to the TST as well as the ESAT6/CFP-10 antigens. In summary, MVA85A-vaccinated children had a persistently higher Ag85A immune response 14 months following vaccination than controls. All the children had negligible evidence of latent infection with M. tuberculosis (Mtb), suggesting that deploying a prophylactic vaccine against Mtb infection at this age could still be effective in this setting., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Influenza viruses are adept in human populations. Indeed, they have the capacity to evade the immune system through mechanisms of mutations (antigenic drift) and major variations in surface protein expression (antigenic shift). When a major change occurs, the risk of a human pandemic arises. Three influenza pandemics occurred during the 20th century, the most serious being the Spanish influenza. The last pandemic of the past century occurred in 1968, and the responsible virus infected an estimated 1-3 million people throughout the world. The first pandemic of the present century occurred in 2009 and was sustained by a H1N1 strain (A/California/07/09). In 1997, a novel avian influenza virus, H5N1, first infected humans in China. Since its emergence, the H5N1 virus has spread from Asia to Europe and Africa, resulting in the infection of millions of poultry and wild birds. So far, 522 human cases and 322 deaths have been reported by the WHO. Many studies have therefore been performed to obtain efficacious and safe H5N1 vaccines. One of these is Aflunov(®). Aflunov is a prepandemic monovalent A/H5N1 influenza vaccine adjuvanted with MF59 produced by Novartis Vaccines and Diagnostics. In nonclinical studies conducted in rabbits, Aflunov proved to be well-tolerated, did not cause maternal or embryo-fetal toxicity, was not teratogenic, and had no effects on postnatal development. In clinical studies, Aflunov proved safe and well-tolerated in infants, children, adolescents, adults and the elderly. In the same subjects, the vaccine elicited robust immunogenicity against both homologous (A/Vietnam/1194/2004 clade 1) and heterologous viral strains (for instance, A/Indonesia/05/2005 or A/Turkey/15/2006) and induced immunologic memory. Thus, in 2010, the CHMP issued a positive opinion on Aflunov and in January 2011 Aflunov was given marketing authorization. This vaccine could be very useful in the event of adaptation of the H5N1 virus to humans, which could cause a new pandemic.

Background: Group A meningococci are the source of major epidemics of meningitis in Africa. An affordable, highly immunogenic meningococcal A conjugate vaccine is needed., Methods: We conducted two studies in Africa to evaluate a new MenA conjugate vaccine (PsA-TT). In study A, 601 children, 12 to 23 months of age, were randomly assigned to receive PsA-TT, a quadrivalent polysaccharide reference vaccine (PsACWY), or a control vaccine (Haemophilus influenzae type b conjugate vaccine [Hib-TT]). Ten months later, these children underwent another round of randomization within each group to receive a full dose of PsA-TT, a one-fifth dose of PsACWY, or a full dose of Hib-TT, with 589 of the original participants receiving a booster dose. In study B, 900 subjects between 2 and 29 years of age were randomly assigned to receive PsA-TT or PsACWY. Safety and reactogenicity were evaluated, and immunogenicity was assessed by measuring the activity of group A serum bactericidal antibody (SBA) with rabbit complement and performing an IgG group A-specific enzyme-linked immunosorbent assay., Results: In study A, 96.0% of the subjects in the PsA-TT group and 63.7% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline; in study B, 78.2% of the subjects in the PsA-TT group and 46.2% of those in the PsACWY group had SBA titers that were at least four times as high as those at baseline. The geometric mean SBA titers in the PsA-TT groups in studies A and B were greater by factors of 16 and 3, respectively, than they were in the PsACWY groups (P<0.001). In study A, the PsA-TT group had higher antibody titers at week 40 than the PsACWY group and had obvious immunologic memory after receiving a polysaccharide booster vaccine. Safety profiles were similar across vaccine groups, although PsA-TT recipients were more likely than PsACWY recipients to have tenderness and induration at the vaccination site. Adverse events were consistent with age-specific morbidity in the study areas; no serious vaccine-related adverse events were reported., Conclusions: The PsA-TT vaccine elicited a stronger response to group A antibody than the PsACWY vaccine. (Funded by the Meningitis Vaccine Project through a grant from the Bill and Melinda Gates Foundation; Controlled-Trials.com numbers, ISRCTN78147026 and ISRCTN87739946.).

Chronic infections in mice can result in defects in memory CD8 T cell properties including low expression of the IL-7Ralpha (CD127). To determine whether defects in memory CD8 T cell formation exist during human chronic infections and to what extent these defects may be allele- or epitope-specific, we compared influenza (Flu), vaccinia (VV) and EBV-specific CD8 T cells to HIV-specific CD8 T cells, using a panel of 13 HIV tetramers. Compared to Flu, VV or EBV, HIV tetramer+ CD8 T cells expressed significantly lower levels of CD127, and this reduction was pervasive across all epitopes and alleles tested and over a wide range of viral loads and CD4 counts. These results indicate impaired HIV-specific memory CD8 T cell differentiation, regardless of level of control of viremia, epitopes targeted or restricting HLA alleles.