Naturally acquired immunity to sexual stageP. falciparumparasites

Parasitology ◽  
2016 ◽  
Vol 143 (2) ◽  
pp. 187-198 ◽  
Author(s):  
WILL J. R. STONE ◽  
KATHLEEN W. DANTZLER ◽  
SANDRA K. NILSSON ◽  
CHRIS J. DRAKELEY ◽  
MATTHIAS MARTI ◽  
...  
Keyword(s):  
Current Knowledge ◽  
Acquired Immunity ◽  
Transmission Blocking ◽  
Erythrocyte Surface ◽  
Antibody Titres ◽  
Specific Proteins ◽  
Specialized Form ◽  
Transmission Stage ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

SUMMARYGametocytes are the specialized form ofPlasmodiumparasites that are responsible for human-to-mosquito transmission of malaria. Transmission of gametocytes is highly effective, but represents a biomass bottleneck for the parasite that has stimulated interest in strategies targeting the transmission stages separately from those responsible for clinical disease. Studying targets of naturally acquired immunity against transmission-stage parasites may reveal opportunities for novel transmission reducing interventions, particularly the development of a transmission blocking vaccine (TBV). In this review, we summarize the current knowledge on immunity against the transmission stages ofPlasmodium. This includes immune responses against epitopes on the gametocyte-infected erythrocyte surface during gametocyte development, as well as epitopes present upon gametocyte activation in the mosquito midgut. We present an analysis of historical data on transmission reducing immunity (TRI), as analysed in mosquito feeding assays, and its correlation with natural recognition of sexual stage specific proteins Pfs48/45 and Pfs230. Although high antibody titres towards either one of these proteins is associated with TRI, the presence of additional, novel targets is anticipated. In conclusion, the identification of novel gametocyte-specific targets of naturally acquired immunity against different gametocyte stages could aid in the development of potential TBV targets and ultimately an effective transmission blocking approach.

scholarly journals Model-informed COVID-19 vaccine prioritization strategies by age and serostatus

2020 ◽  
Author(s):  
Kate M Bubar ◽  
Kyle Reinholt ◽  
Stephen M Kissler ◽  
Marc Lipsitch ◽  
Sarah Cobey ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Cumulative Incidence ◽  
Acquired Immunity ◽  
Years Of Life Lost ◽  
Serological Tests ◽  
Transmission Blocking ◽  
Individual Level ◽  
Transmission Rates ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

Limited initial supply of SARS-CoV-2 vaccine raises the question of how to prioritize available doses. Here, we used a mathematical model to compare five age-stratified prioritization strategies. A highly effective transmission-blocking vaccine prioritized to adults ages 20-49 years minimized cumulative incidence, but mortality and years of life lost were minimized in most scenarios when the vaccine was prioritized to adults over 60 years old. Use of individual-level serological tests to redirect doses to seronegative individuals improved the marginal impact of each dose while partially addressing existing inequities in COVID-19 impact. While maximum impact prioritization strategies were broadly consistent across countries, transmission rates, vaccination rollout speeds, and estimates of naturally acquired immunity, this framework can be used to compare impacts of prioritization strategies across contexts.

scholarly journals Model-informed COVID-19 vaccine prioritization strategies by age and serostatus

Science ◽  
2021 ◽  
Vol 371 (6532) ◽  
pp. 916-921 ◽  
Author(s):  
Kate M. Bubar ◽  
Kyle Reinholt ◽  
Stephen M. Kissler ◽  
Marc Lipsitch ◽  
Sarah Cobey ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Severe Acute Respiratory Syndrome ◽  
Cumulative Incidence ◽  
Acquired Immunity ◽  
Years Of Life Lost ◽  
Serological Tests ◽  
Individual Level ◽  
Transmission Rates ◽  
Effective Transmission ◽  
Transmission Blocking Vaccine

Limited initial supply of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine raises the question of how to prioritize available doses. We used a mathematical model to compare five age-stratified prioritization strategies. A highly effective transmission-blocking vaccine prioritized to adults ages 20 to 49 years minimized cumulative incidence, but mortality and years of life lost were minimized in most scenarios when the vaccine was prioritized to adults greater than 60 years old. Use of individual-level serological tests to redirect doses to seronegative individuals improved the marginal impact of each dose while potentially reducing existing inequities in COVID-19 impact. Although maximum impact prioritization strategies were broadly consistent across countries, transmission rates, vaccination rollout speeds, and estimates of naturally acquired immunity, this framework can be used to compare impacts of prioritization strategies across contexts.

scholarly journals Sexual Development in Non-Human Parasitic Apicomplexa: Just Biology or Targets for Control?

Animals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2891
Author(s):  
Teresa Cruz-Bustos ◽  
Anna Sophia Feix ◽  
Bärbel Ruttkowski ◽  
Anja Joachim
Keyword(s):  
Sexual Reproduction ◽  
Sexual Development ◽  
Current Knowledge ◽  
Life Cycles ◽  
Complex Life Cycles ◽  
Transmission Blocking ◽  
New Hosts ◽  
Sexual Stages ◽  
New Generation ◽  
Effective Transmission

The phylum Apicomplexa is a major group of protozoan parasites including gregarines, coccidia, haemogregarines, haemosporidia and piroplasms, with more than 6000 named species. Three of these subgroups, the coccidia, hemosporidia, and piroplasms, contain parasites that cause important diseases of humans and animals worldwide. All of them have complex life cycles involving a switch between asexual and sexual reproduction, which is key to their development. Fertilization (i.e., fusion of female and male cells) results in the formation of a zygote that undergoes meiosis, forming a new generation of asexual stages. In eukaryotes, sexual reproduction is the predominant mode of recombination and segregation of DNA. Sex is well documented in many protist groups, and together with meiosis, is frequently linked with transmission to new hosts. Apicomplexan sexual stages constitute a bottleneck in the life cycle of these parasites, as they are obligatory for the development of new transmissible stages. Consequently, the sexual stages represent attractive targets for vaccination. Detailed understanding of apicomplexan sexual biology will pave the way for the design and implementation of effective transmission-blocking strategies for parasite control. This article reviews the current knowledge on the sexual development of Apicomplexa and the progress in transmission-blocking vaccines for their control, their advantages and limitations and outstanding questions for the future.

scholarly journals Evaluation of two lead malaria transmission blocking vaccine candidate antibodies in natural parasite-vector combinations

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Anais Bompard ◽  
Dari F. Da ◽  
Rakiswendé S. Yerbanga ◽  
Sumi Biswas ◽  
Melissa Kapulu ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Vaccine Candidate ◽  
Transmission Blocking ◽  
Transmission Blocking Vaccine

The immune response and the evaluation of acquired immunity against gastrointestinal nematodes in cattle: a review

Parasitology ◽  
2000 ◽  
Vol 120 (7) ◽  
pp. 25-42 ◽  
Author(s):  
E. CLAEREBOUT ◽  
J. VERCRUYSSE
Keyword(s):  
Immune Response ◽  
Immune Responses ◽  
Protective Immunity ◽  
Current Knowledge ◽  
Small Ruminants ◽  
Gastrointestinal Nematodes ◽  
Gastrointestinal Parasites ◽  
Acquired Immunity ◽  
Immunological Parameters ◽  
Iga Response

The present review discusses the immune responses to gastrointestinal nematodes in cattle and the different immunological and parasitological parameters used to assess acquired immunity. Measuring acquired immunity to gastrointestinal nematodes in cattle (e.g. for the evaluation of candidate parasite vaccines) is hampered by the limited understanding of bovine immune responses against gastrointestinal parasites. In this paper the available data on protective immunity against gastrointestinal nematodes, and especially Ostertagia ostertagi, in cattle are compared with the current knowledge of protective immune responses against gastrointestinal nematodes in rodent models and small ruminants. In contrast to the immune response in mice, which is controlled by T helper 2 (Th2) lymphocytes and results in mast cell- or goblet cell- mediated expulsion of adult worms, bovine immune responses to O. ostertagi do not show a clear Th2 cytokine profile, nor do they result in rapid expulsion of the parasite. The first manifestation of immunity to O. ostertagi in calves is a reduction of worm fecundity, possibly regulated by the local IgA response. Worm numbers are only reduced after a prolonged period of host–parasite contact, and there are indications that O. ostertagi actively suppresses the host's immune response. Until the mechanisms of protective immunity against O. ostertagi are revealed, the use of immunological parameters to estimate acquired immunity in cattle is based on their correlation with parasitological parameters and on extrapolation from rodent and small ruminant models. Assessing the resistance of calves against a challenge infection by means of parasitological parameters is probably still the most accurate way to measure acquired immunity against gastrointestinal nematodes.

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