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Abstract
Nanomaterials have been shown to affect gut microbiota (GM) both in vivo and in vitro. The effects have been shown to depend on size, dose, dose duration and functional groups. In general, more studies seem to indicate dose-dependent adverse effects of NMs towards GM. Standardized protocols are needed for characterization of NMs, dosing, and test systems (both in vitro and in vivo).
Some nanomaterials (NMs) have been shown to possess antimicrobial activity and cause GM dysbiosis. Since NMs are being used widely, a systematic assessment of the effects of NMs on GM is warranted. In this systematic review, a total of 46 in vivo and 22 in vitro studies were retrieved from databases and search engines including Science-Direct, Pubmed and Google scholar. Criteria for assessment of studies included use of in vitro or in vivo studies, characterization of NMs, use of single or multiple doses as well as consistency of results. GM dysbiosis has been studied most widely on TiO2, Ag, Zn-based NMs. There was moderate evidence for GM dysbiosis caused by Zn- and Cu-based NMs, Cu-loaded chitosan NPs and Ag NMs, and anatase TiO2 NPs, as well as low evidence for SWCNTs, nanocellulose, SiO2, Se, nanoplastics, CeO2, MoO3 and graphene-based NMs. Most studies indicate adverse effects of NMs towards GM. However, more work is required to elucidate the differences on the reported effects of NM by type and sex of organisms, size, shape and surface properties of NMs as well as effects of exposure to mixtures of NMs. For consistency and better agreement among studies on GM dysbiosis, there is need for internationally agreed protocols on, inter alia, characterization of NMs, dosing (amounts, frequency and duration), use of sonication, test systems (both in vitro and in vivo), including oxygen levels for in vitro models.
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Lourenço J, Obolski U, Swarthout TD, Gori A, Bar-Zeev N, Everett D, Kamng'ona AW, Mwalukomo TS, Mataya AA, Mwansambo C, Banda M, Gupta S, French N, Heyderman RS. Determinants of high residual post-PCV13 pneumococcal vaccine-type carriage in Blantyre, Malawi: a modelling study. BMC Med 2019; 17:219. [PMID: 31801542 PMCID: PMC6894346 DOI: 10.1186/s12916-019-1450-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 10/24/2019] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND In November 2011, Malawi introduced the 13-valent pneumococcal conjugate vaccine (PCV13) into the routine infant schedule. Four to 7 years after introduction (2015-2018), rolling prospective nasopharyngeal carriage surveys were performed in the city of Blantyre. Carriage of Streptococcus pneumoniae vaccine serotypes (VT) remained higher than reported in high-income countries, and impact was asymmetric across age groups. METHODS A dynamic transmission model was fit to survey data using a Bayesian Markov-chain Monte Carlo approach, to obtain insights into the determinants of post-PCV13 age-specific VT carriage. RESULTS Accumulation of naturally acquired immunity with age and age-specific transmission potential were both key to reproducing the observed data. VT carriage reduction peaked sequentially over time, earlier in younger and later in older age groups. Estimated vaccine efficacy (protection against carriage) was 66.87% (95% CI 50.49-82.26%), similar to previous estimates. Ten-year projected vaccine impact (VT carriage reduction) among 0-9 years old was lower than observed in other settings, at 76.23% (CI 95% 68.02-81.96%), with sensitivity analyses demonstrating this to be mainly driven by a high local force of infection. CONCLUSIONS There are both vaccine-related and host-related determinants of post-PCV13 pneumococcal VT transmission in Blantyre with vaccine impact determined by an age-specific, local force of infection. These findings are likely to be generalisable to other Sub-Saharan African countries in which PCV impact on carriage (and therefore herd protection) has been lower than desired, and have implications for the interpretation of post-PCV carriage studies and future vaccination programs.
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Affiliation(s)
- J Lourenço
- Department of Zoology, University of Oxford, Oxford, UK.
| | - U Obolski
- School of Public Health, Tel Aviv University, Tel Aviv, Israel.,Porter School of the Environment and Earth Sciences, Tel Aviv University, Tel Aviv, Israel
| | - T D Swarthout
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.,Clinical Sciences Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - A Gori
- NIHR Mucosal Pathogens Research Unit, Division of Infection & Immunity, University College London, London, UK
| | - N Bar-Zeev
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.,Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
| | - D Everett
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.,The Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - A W Kamng'ona
- Department of Biomedical Sciences, College of Medicine, University of Malawi, Blantyre, Malawi
| | - T S Mwalukomo
- Department of Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - A A Mataya
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | | | - M Banda
- Ministry of Education, Blantyre, Malawi
| | - S Gupta
- Department of Zoology, University of Oxford, Oxford, UK
| | - N French
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.,Centre for Global Vaccine Research, Institute of Infection and Global Health, University of Liverpool, Liverpool, UK
| | - R S Heyderman
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi.,NIHR Mucosal Pathogens Research Unit, Division of Infection & Immunity, University College London, London, UK
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