The SARS-CoV-2 Omicron variant has become the dominant SARS-CoV-2 variant around the world and exhibits immune escape to current COVID-19 vaccines to some extent due to its numerous spike mutations. Here, we evaluated the immune responses to booster vaccination with intramuscular adenovirus-vectored vaccine (Ad5-nCoV), aerosolized Ad5-nCoV, a recombinant protein subunit vaccine (ZF2001) or homologous inactivated vaccine (CoronaVac) in those who received two doses of inactivated COVID-19 vaccines 6 months prior. We found that the Ad5-nCoV booster induced potent neutralizing activity against the wild-type virus and Omicron variant, while aerosolized Ad5-nCoV generated the greatest neutralizing antibody responses against the Omicron variant at day 28 after booster vaccination, at 14.1-fold that of CoronaVac, 5.6-fold that of ZF2001 and 2.0-fold that of intramuscular Ad5-nCoV. Similarly, the aerosolized Ad5-nCoV booster produced the greatest IFNγ T-cell response at day 14 after booster vaccination. The IFNγ T-cell response to aerosolized Ad5-nCoV was 12.8-fold for CoronaVac, 16.5-fold for ZF2001, and 5.0-fold for intramuscular Ad5-nCoV. Aerosolized Ad5-nCoV booster also produced the greatest spike-specific B cell response. Our findings suggest that inactivated vaccine recipients should consider adenovirus-vectored vaccine boosters in China and that aerosolized Ad5-nCoV may provide a more efficient alternative in response to the spread of the Omicron variant.

T-cell immunity plays an important role in the control of SARS-CoV-2 and has a great cross-protective effect on the variants. The Omicron BA.1 variant contains more than 30 mutations in the spike and severely evades humoral immunity. To understand how Omicron BA.1 spike mutations affect cellular immunity, the T-cell epitopes of SARS-CoV-2 wild-type and Omicron BA.1 spike in BALB/c (H-2^d) and C57BL/6 mice (H-2^b) were mapped through IFNγ ELISpot and intracellular cytokine staining assays. The epitopes were identified and verified in splenocytes from mice vaccinated with the adenovirus type 5 vector encoding the homologous spike, and the positive peptides involved in spike mutations were tested against wide-type and Omicron BA.1 vaccines. A total of eleven T-cell epitopes of wild-type and Omicron BA.1 spike were identified in BALB/c mice, and nine were identified in C57BL/6 mice, only two of which were CD4⁺ T-cell epitopes and most of which were CD8⁺ T-cell epitopes. The A67V and Del 69-70 mutations in Omicron BA.1 spike abolished one epitope in wild-type spike, and the T478K, E484A, Q493R, G496S and H655Y mutations resulted in three new epitopes in Omicron BA.1 spike, while the Y505H mutation did not affect the epitope. These data describe the difference of T-cell epitopes in SARS-CoV-2 wild-type and Omicron BA.1 spike in H-2^b and H-2^d mice, providing a better understanding of the effects of Omicron BA.1 spike mutations on cellular immunity.

Background: Malaria remains a serious public health threat, especially in Africa. The challenge in detecting low-density Plasmodium infections via traditional microscopy hampers effective malaria surveillance and control. To date, there are no reports on nationwide community-based molecular detection for malaria in Sierra Leone. Methods: In 2022, during the COVID-19 pandemic, we conducted a nationally representative, age-stratified cross-sectional epidemiological survey in Sierra Leone during the rainy season to investigate the prevalence of Plasmodium infection. A total of 2112 individuals aged 2 years or older were recruited nationwide and all participants completed the survey and provided whole blood samples. Nucleic acids were extracted from the blood samples and tested for Plasmodium infection using quantitative PCR (qPCR), with species identification performed on 400 of these samples. Results: Among all 2112 samples, the Plasmodium qPCR positivity rate was 63.0% (95% CI 61.0 to 65.1), and the regionally weighted positivity rate was 62.9% (95% CI 58.3 to 67.4) in Sierra Leone. In 400 randomly selected positive samples, 97.75% were infected with Plasmodium falciparum , and 20.5% carried multiple Plasmodium species. The positivity rate significantly decreased in individuals aged 60 years above, and the rate was higher in males. Healthcare workers had the lowest positivity rate. Rural areas had a slightly higher positivity rate than urban areas yet showed no significant difference. Based on threshold cycle values, 18.6% of positive samples showed relatively low parasitaemia. Additionally, 93.5% of infected individuals self-reported as asymptomatic. Conclusions: This study highlights the importance of molecular diagnosis in malaria-endemic areas for surveillance, diagnosis and treatment. The high prevalence of malaria infection among individuals aged ≥20 years, together with the high prevalence of asymptomatic, low-density infections, indicates a sustained potential transmission reservoir. Additionally, urban and rural malaria prevalence showed no statistically significant difference, a finding that underscores the need for greater attention to urban malaria.

Adeno-associated virus (AAV) vectors face a critical translational challenge in ocular gene therapy due to pre-existing neutralizing antibodies (NAbs) whose seroprevalence limits patient eligibility. Standard NAb detection using non-ocular cell models (Human Embryonic Kidney 293T) may inadequately predict retinal transduction inhibition due to cell type-related variations in receptor usage and immunogenicity. This study established parallel NAb detection platforms utilizing human retinal pigment epithelial (ARPE-19) cells and standard 293T cells to systematically evaluate clinical serum samples against ophthalmologically relevant AAV serotypes (2, 5, 8, 9) via luciferase reporter-based transduction inhibition assays. Comparative analysis demonstrated ARPE-19 exhibited 42–48% higher NAb titers against AAV5/9 compared to 293T cells, with distinct serotype-biased neutralization hierarchies observed between cellular models. Furthermore, female-derived sera exhibited significantly elevated NAbs against particular serotypes in the ARPE-19 system. Critically, inter-serotype cross-neutralization correlation patterns differed substantially between cellular platforms. These findings demonstrate that physiologically relevant retinal cellular models provide essential immunological profiling data, revealing NAb characteristics obscured in standard assays. Consequently, employing retinal cell-based platforms is crucial for optimizing AAV serotype selection, patient stratification, and predicting clinical outcomes in ocular gene therapy.

Retinal degenerative diseases, such as Stargardt disease and age-related macular degeneration (AMD), are leading causes of irreversible blindness, and AAV-