Biology subjects

Maina, M.

Publications and source records attributed to Maina, M..

6 recordsLinked to original sources

bioRxiv2026

Direct Virus-Bacteria Binding Enhances Streptococcus equi subsp. zooepidemicus Colonisation and Bacterial-Driven Immune Activation During H3N8 Equine Influenza A Virus Co-Infection

Respiratory viral-bacterial co-infections cause severe disease across species, yet the molecular mechanisms underlying enhanced pathogenesis remain poorly understood. This study characterised H3N8 equine influenza A virus (IAV) and Streptococcus equi subspecies zooepidemicus (SEZ) co-infections using complementary ultrastructural and transcriptomic approaches. Transmission electron microscopy demonstrated direct physical binding between spherical (A/equine/Miami/63) and filamentous (A/equine/Sussex/89 and A/equine/Newmarket/5/2003) IAV isolates and SEZ, including when SEZ was heat-inactivated ({theta}SEZ). Lectin staining revealed that SEZ expresses predominantly 2,3-linked sialic acids, the receptor for equine IAV. However, virus-bacteria binding persisted despite neuraminidase treatment. Scanning electron microscopy quantification demonstrated that viral pre-infection significantly enhanced bacterial adherence to cells of the DH82 canine macrophage-like cell line (2-fold increase, p<0.01) but not ExtEqFL (equine lung-derived) cells, revealing cell-type-specific enhancement. RNA-sequencing analysis showed that bacterial infection drove most transcriptional changes during co-infection with little difference in the number of differentially expressed genes (DEGs) between infection with SEZ alone (146 DEGS) or after pre-infection with either A/equine/Sussex/89 (166 DEGS) or A/equine/Newmarket/5/2003 (149 DEGS). Validation of upregulation of selected cytokines by RT-qPCR and ELISA demonstrated that SEZ infection drives dramatic cytokine upregulation compared to mock or {theta}SEZ controls. Viral pre-infection did not alter the SEZ-induced pro-inflammatory cytokine responses (IL-6, IL-8, TNF-) but significantly reduced IFN-{beta} expression compared to SEZ infection alone. These findings suggest that direct virus-bacteria physical interactions may drive cell-type-specific enhancement of bacterial colonisation, fundamentally advancing our understanding of respiratory co-infection pathogenesis.

microbiology↗

bioRxiv2026

Serine proteases are required to activate influenza D virus haemagglutinin-esterase fusion (HEF) protein

Influenza D virus (IDV), the most recently identified member of the Orthomyxoviridae, was first isolated from pigs but cattle have been identified as the reservoir host. To date, IDV has not been confirmed to cause human disease. Like the haemagglutinin (HA) of influenza A virus (IAV) and the haemagglutinin-esterase fusion (HEF) protein of influenza C virus (ICV), the IDV HEF is produced as a precursor protein (HEF0) that must be proteolytically cleaved by host cell proteases (into HEF1 and HEF2) to gain its fusion capacity. The proteases that activate IAV HA have been extensively studied, but those responsible for activation of IDV HEF were unknown. Identifying these proteases is key to understanding early virus-host interactions and host restriction. Therefore, we generated ICV and IDV pseudotyped viruses (PVs) in HEK 293T producer cells with or without co-transfection of plasmids expressing different type II serine proteases. Subsequent transduction of swine testicular (ST) cells indicated strong activation of both ICV and IDV PVs by the human airway trypsin-like protease (HAT) and its swine homologue (swAT). Furthermore, like influenza A/Puerto Rico/8/34 (H1N1) virus, addition of exogenous protease is not essential for IDV replication in MDCK II cells, most likely due to endogenous expression of matriptase. In conclusion, our data unveil new information on host cell proteases that activate ICV and IDV HEF proteins. Importantly, the data suggest that protease specificity is not a factor in restriction of IDV replication in the human upper respiratory tract.

microbiology↗

bioRxiv2025

Development and optimisation of Influenza C and Influenza D pseudotyped viruses

To facilitate the study of influenza C (ICV) and influenza D (IDV) viruses, we generated lentiviral pseudotyped viruses (PVs) expressing the hemagglutinin-esterase fusion (HEF) glycoprotein from ICV (C/Minnesota/33/2015) and IDV (D/Swine/Italy/199724-3/2015, D/Bovine/France/5920/2014, and D/Bovine/Ibaraki/7768/2016). The production of these PVs was optimised using different amount of human airway trypsin-like (HAT) protease to enhance HEF maturation, and the transduction efficiency was evaluated in multiple cell lines. Using these PVs, we established a pseudovirus-based microneutralisation (pMN) assay to measure neutralising antibody responses and adapted an esterase activity assay to evaluate PV. Specific antisera neutralised PVs but failed to inhibit esterase activity. These findings confirm that ICV and IDV PVs provide a scalable, sensitive, and safe tool for antiviral screening, and sero-epidemiological research.

immunology↗

bioRxiv2022

Dityrosine cross-links are present in Alzheimer's disease-derived tau oligomers and paired helical filaments (PHF) which promotes the stability of PHF-core tau (297-391) in vitro.

A characteristic hallmark of Alzheimers Disease (AD) is the pathological aggregation and deposition of tau into paired helical filaments (PHF) in neurofibrillary tangles (NFTs). Oxidative stress is an early event during AD pathogenesis and is associated with tau-mediated AD pathology. Oxidative environments can result in the formation of covalent dityrosine crosslinks that can increase protein stability and insolubility. Dityrosine cross-linking has been shown to occur in vivo in A{beta} plaques and -synuclein aggregates in Lewy bodies, and this modification may increase the insolubility of these aggregates and their resistance to degradation. Using the PHF-core tau fragment (residues 297 - 391) as a model, we have previously demonstrated that dityrosine formation traps tau assemblies to reduce further elongation. However, it is unknown whether dityrosine crosslinks are found in tau deposits in vivo in AD and its relevance to disease mechanism is unclear. Here, using transmission electron microscope (TEM) double immunogold-labelling, we reveal that neurofibrillary NFTs in AD are heavily decorated with dityrosine crosslinks alongside tau. Single immunogold-labelling TEM and fluorescence spectroscopy revealed the presence of dityrosine on AD brain-derived tau oligomers and fibrils. Using the tau (297-391) PHF-core fragment as a model, we further showed that prefibrillar tau species are more amenable to dityrosine crosslinking than tau fibrils. Dityrosine formation results in heat and SDS stability of oxidised prefibrillar and fibrillar tau assemblies. This finding has implications for understanding the mechanism governing the insolubility and toxicity of tau assemblies in vivo.

biochemistry↗

bioRxiv2020

Outcomes of Isoniazid Preventive Therapy among people living with HIV in Kenya: A retrospective study of routine health care data

Introduction Isoniazid preventive therapy (IPT) taken by People Living with HIV (PLHIV) protects against tuberculosis (TB). Despite its recommendation, there is scarcity of data on the uptake of IPT among PLHIV and factors associated with treatment outcomes. We aimed to determine the proportion of PLHIV initiated on IPT, IPT treatment outcomes and screening for TB during and after IPT.Methods A retrospective cohort study of a representative sample of PLHIV initiated on IPT between July 2015 and June 2018 in Kenya. We abstracted information on socio-demographic, TB screening practices, IPT initiation, follow up, and outcomes from health facilities’ patient record cards, IPT cards and IPT registers. Further, we assessed baseline characteristics as potential correlates of developing TB during and after treatment and IPT completion using multivariable logistic regression.Results We enrolled 138,442 PLHIV into ART during the study period and initiated 95,431 (68.9%) into IPT. Abstracted files for 4708 patients initiated on IPT, out of which 3891(82.6%) had IPT treatment outcomes documented, 4356(92.5%) had ever been screened for TB at every clinic visit and 4,243(90.1%) had documentation of TB screening on the IPT tool before IPT initiation. 3712(95.4%) of patients with documented IPT treatment outcomes completed their treatment. 42(0.89%) of the abstracted patients developed active TB, 16(38.1%) during and 26(61.9%) after completing IPT. Follow up for TB at 6-month post-IPT completion was done for 2729(73.5%) of patients with IPT treatment outcomes. Sex, Viral load suppression and clinic type were associated with TB development (p<0.05). Levels 4, 5, FBO, and private facilities and IPT prescription practices were associated with IPT completion (p<0.05).Conclusion Two-thirds of PLHIV were initiated on IPT, with a high completion rate. TB screening practices were better during IPT than after completion. Development of TB during and after IPT emphasises need for keen follow up.View Full Text

scientific communication and education↗

bioRxiv2019

PURPOSEFUL DESIGN OF A SURVEY TOOL TO EVALUATE THE ADEQUACY OF HOSPITALS WATER SANITATION AND HYGIENE AND ALLOCATE RESPONSIBILITY FOR ACTION - FROM WASH FIT to WASH FAST

BackgroundPoor water sanitation and hygiene (WASH) in health care facilities increases hospital associated infections and results in greater use of second line antibiotics, which drives antimicrobial resistance. The existing assessment tool, Water and Sanitation for Health Facility Improvement Tool (WASH FIT), is designed for self-assessment in smaller primary facilities. A tool is needed for larger facilities with multiple inpatient units, that supports comparison of multiple facilities and identifies who is responsible for action at different levels of the health system.\n\nMethodsWe adapted the WASH FIT tool to: 1) create a simple numeric scoring approach to enable comparison of hospitals and facilitate tracking of WASH performance over time; (2) identify indicators that can be assessed and scored for each hospital ward to help identify variation within facilities and; (3) identify those responsible to effect positive change at different levels of the health system. We used a pilot, analysis of interview data and consultative stakeholder meetings to establish the feasibility and face validity of the WASH Facility Survey Tool (WASH FAST).\n\nResultsWASH FAST can be used to produce an aggregate percentage score at facility level to summarise hospitals overall WASH status and illustrate variation across hospitals. Thirty-four of the 65 indicators spanning four WASH domains can be assessed at ward level enabling between ward variations to be highlighted. Three levels of responsibility for WASH service monitoring and improvement were identified that were supported by qualitative data and multiple stakeholders: the county/regional level, hospital senior management and the infection prevention and control committee within the healthcare facility.\n\nConclusionWe propose WASH FAST can be used as a survey tool to assess, improve and monitor progress of WASH and IPC in hospitals in resource-limited settings, providing useful data for decision making and contributing to wider quality improvement efforts.

epidemiology↗