Microfilaremic loiasis is associated with T cell hyporesponsiveness against SARS-CoV-2
13 affiliations
- 1Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
- 2Department of Medicine I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria
- 3I, Department of Medicine, Division of Infectious Diseases, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
- 4Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
- 5Protozoa Immunology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- 6German Centre for Infection Research, Partner Sites Hamburg-Lübeck, Borstel-Riems, Germany
- 7Drug Implementation Research Group, Bernhard Nocht Institute for Tropical Medicine, and I, Department of Medicine, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany
- 8Radboud University Medical Center, Department of Medical Microbiology, Nijmegen, The Netherlands
- 9Section Interface, Helminth Immunology Group, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
- 10Department of Biology, University Hamburg, Hamburg, Germany
- 11Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
- 12German Center for Infection and Research (DZIF), Partner site Tübingen, Tübingen, Germany
- 13MSH Medical School Hamburg, Institute for Translational Medicine, Hamburg, Germany
Abstract
Background: Loiasis is a chronic filarial infection endemic to Central and West Africa. Although long considered benign, increasing evidence links loiasis to substantial morbidity and mortality. The infection is associated with immune modulation, including Th2-skewed responses and elevated regulatory cytokines. Clinically, loiasis is classified as microfilaremic (presence of circulating microfilariae) or amicrofilaremic (“occult”) disease, the latter defined by a history of eyeworm migration without detectable microfilaremia. This study investigated how chronic L. loa infection influences antibody and T cell responses to SARS-CoV-2 following natural infection. Methods: Between 2022 and 2024, this cross-sectional study was done in rural and periurban villages of the Ngounié and Moyen-Ogooué provinces of Gabon. Study procedures included diagnostics for loiasis and immunological assays. Microfilaremia was confirmed by stained blood smear microscopy, and occult disease was identified using the Rapid Assessment Procedure for Loiasis. SARS-CoV-2-specific IgG responses to spike and nucleocapsid proteins were measured by ELISA, and IFN-γ responses to spike antigen were assessed using an interferon-gamma release assay. Results: Overall, 192 participants were categorized as microfilaremic (n = 43), occult loiasis (n = 59), or without evidence of active loiasis (n = 90). IFN-γ responses were reduced in microfilaremic individuals compared with other participants (p = 0.031), whereas IgG responses did not differ. Subsequent analysis across the three groups confirmed that IFN-γ responses were lower in microfilaremic compared with occult participants (p = 0.012). Conclusion: These findings suggest that microfilaremic loiasis may impair proinflammatory T cell responses to viral antigens, highlighting the need for further research into the broader immunological effects of Loa loa infection in endemic populations. Author summary: Loiasis is a parasitic infection caused by the worm Loa loa and is common in parts of Central and West Africa. Although long considered relatively benign, growing evidence indicates that loiasis is associated with substantial morbidity. The immunological consequences of chronic Loa loa infection remain poorly understood. A small number of studies suggest that Loa loa may influence immune regulation, but its broader impact on antiviral immunity is largely unknown. The COVID-19 pandemic provided a unique opportunity to examine immune responses to a newly emerging virus in a population where loiasis is endemic. We therefore investigated how different forms of Loa loa infection influence immune responses after natural SARS-CoV-2 infection. We compared individuals with circulating microfilariae in their blood (microfilaremic), individuals with occult loiasis (history of eye worm), and individuals without signs of active infection. We found that microfilaremic individuals had weaker virus-specific IFN-γ T cell responses, while antibody levels were similar across groups. These findings suggest that active loiasis may dampen certain antiviral immune functions. Understanding the underlying mechanisms is important, as such immune modulation could affect responses to vaccines and other infectious diseases in endemic regions.
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BibTeX
@article{stock2026microfilaremic,
title = {{Microfilaremic loiasis is associated with T cell hyporesponsiveness against SARS-CoV-2}},
author = {Maximilian Augé Stock and Dearie Glory Okwu and Ayong More and Anna Doralt and Rodrigue Bikangui and Ismaël Pierrick Mikelet Boussoukou and Kirsten Alexandra Eberhardt and Maren Sandkuhl and Rella Zoleko Manego and Ghyslain Mombo-Ngoma and Matthew McCall and Minka Breloer and Meral Esen and Marylyn Addo and Bertrand Lell and Luzia Veletzky and Rafiou Adamou and Maria Sophia Mackroth},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = oct,
doi = {10.1371/journal.pntd.0014104},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014104},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Microfilaremic loiasis is associated with T cell hyporesponsiveness against SARS-CoV-2
AU - Maximilian Augé Stock
AU - Dearie Glory Okwu
AU - Ayong More
AU - Anna Doralt
AU - Rodrigue Bikangui
AU - Ismaël Pierrick Mikelet Boussoukou
AU - Kirsten Alexandra Eberhardt
AU - Maren Sandkuhl
AU - Rella Zoleko Manego
AU - Ghyslain Mombo-Ngoma
AU - Matthew McCall
AU - Minka Breloer
AU - Meral Esen
AU - Marylyn Addo
AU - Bertrand Lell
AU - Luzia Veletzky
AU - Rafiou Adamou
AU - Maria Sophia Mackroth
PY - 2026
DA - 2026/10/01
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014104
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014104
AB - Background: Loiasis is a chronic filarial infection endemic to Central and West Africa. Although long considered benign, increasing evidence links loiasis to substantial morbidity and mortality. The infection is associated with immune modulation, including Th2-skewed responses and elevated regulatory cytokines. Clinically, loiasis is classified as microfilaremic (presence of circulating microfilariae) or amicrofilaremic (“occult”) disease, the latter defined by a history of eyeworm migration without detectable microfilaremia. This study investigated how chronic L. loa infection influences antibody and T cell responses to SARS-CoV-2 following natural infection. Methods: Between 2022 and 2024, this cross-sectional study was done in rural and periurban villages of the Ngounié and Moyen-Ogooué provinces of Gabon. Study procedures included diagnostics for loiasis and immunological assays. Microfilaremia was confirmed by stained blood smear microscopy, and occult disease was identified using the Rapid Assessment Procedure for Loiasis. SARS-CoV-2-specific IgG responses to spike and nucleocapsid proteins were measured by ELISA, and IFN-γ responses to spike antigen were assessed using an interferon-gamma release assay. Results: Overall, 192 participants were categorized as microfilaremic (n = 43), occult loiasis (n = 59), or without evidence of active loiasis (n = 90). IFN-γ responses were reduced in microfilaremic individuals compared with other participants (p = 0.031), whereas IgG responses did not differ. Subsequent analysis across the three groups confirmed that IFN-γ responses were lower in microfilaremic compared with occult participants (p = 0.012). Conclusion: These findings suggest that microfilaremic loiasis may impair proinflammatory T cell responses to viral antigens, highlighting the need for further research into the broader immunological effects of Loa loa infection in endemic populations. Author summary: Loiasis is a parasitic infection caused by the worm Loa loa and is common in parts of Central and West Africa. Although long considered relatively benign, growing evidence indicates that loiasis is associated with substantial morbidity. The immunological consequences of chronic Loa loa infection remain poorly understood. A small number of studies suggest that Loa loa may influence immune regulation, but its broader impact on antiviral immunity is largely unknown. The COVID-19 pandemic provided a unique opportunity to examine immune responses to a newly emerging virus in a population where loiasis is endemic. We therefore investigated how different forms of Loa loa infection influence immune responses after natural SARS-CoV-2 infection. We compared individuals with circulating microfilariae in their blood (microfilaremic), individuals with occult loiasis (history of eye worm), and individuals without signs of active infection. We found that microfilaremic individuals had weaker virus-specific IFN-γ T cell responses, while antibody levels were similar across groups. These findings suggest that active loiasis may dampen certain antiviral immune functions. Understanding the underlying mechanisms is important, as such immune modulation could affect responses to vaccines and other infectious diseases in endemic regions.
SN - 1935-2735
ER -