Evaluation of sample pooling for the detection of SARS-CoV-2 in a resource-limited setting, Dominican Republic.

INTRODUCTION: COVID-19 is a worldwide public health threat. Diagnosis by RT-PCR has been employed as the standard method to confirm viral infection. Sample pooling testing can optimize the resources by reducing the workload and reagents shortage, and be useful in laboratories and countries with limited resources. This study aims to evaluate SARS-CoV-2 detection by sample pooling testing in comparison with individual sample testing. MATERIALS AND METHODS: We created 210 pools out of 245 samples, varying from 4 to 10 samples per pool, each containing a positive sample. We conducted detection of SARS-CoV-2-specific RdRp/E target sites. RESULTS: Pooling of three samples for SARS-CoV-2 detection might be an efficient strategy to perform without losing RT-PCR sensitivity. CONCLUSIONS: Considering the positivity rate in Dominican Republic and that larger sample pools have higher probabilities of obtaining false negative results, the optimal sample size to perform a pooling strategy shall be three samples.

Evaluation of sample pooling for the detection of SARS-CoV-2 in a resource-limited setting, Dominican Republic Evaluación del análisis de muestras agrupadas para la detección de SARS-CoV-2 en entornos con recursos limitados, República Dominicana

Introduction COVID-19 is a worldwide public health threat. Diagnosis by RT-PCR has been employed as the standard method to confirm viral infection. Sample pooling testing can optimize the resources by reducing the workload and reagents shortage, and be useful in laboratories and countries with limited resources. This study aims to evaluate SARS-CoV-2 detection by sample pooling testing in comparison with individual sample testing. Materials and methods We created 210 pools out of 245 samples, varying from 4 to 10 samples per pool, each containing a positive sample. We conducted detection of SARS-CoV-2-specific RdRp/E target sites. Results Pooling of three samples for SARS-CoV-2 detection might be an efficient strategy to perform without losing RT-PCR sensitivity. Conclusions Considering the positivity rate in Dominican Republic and that larger sample pools have higher probabilities of obtaining false negative results, the optimal sample size to perform a pooling strategy shall be three samples.

Evaluation of sample pooling for the detection of SARS-CoV-2 in a resource-limited setting, Dominican Republic.

INTRODUCTION: COVID-19 is a worldwide public health threat. Diagnosis by RT-PCR has been employed as the standard method to confirm viral infection. Sample pooling testing can optimize the resources by reducing the workload and reagents shortage, and be useful in laboratories and countries with limited resources. This study aims to evaluate SARS-CoV-2 detection by sample pooling testing in comparison with individual sample testing. MATERIALS AND METHODS: We created 210 pools out of 245 samples, varying from 4 to 10 samples per pool, each containing a positive sample. We conducted detection of SARS-CoV-2-specific RdRp/E target sites. RESULTS: Pooling of three samples for SARS-CoV-2 detection might be an efficient strategy to perform without losing RT-PCR sensitivity. CONCLUSIONS: Considering the positivity rate in Dominican Republic and that larger sample pools have higher probabilities of obtaining false negative results, the optimal sample size to perform a pooling strategy shall be three samples.

The impact of cyclin-dependent kinases 4 and 6 inhibitors in the immune response to mRNA SARS-CoV-2 vaccine in women with breast cancer. (preprint)

Introduction: Patients with cancer have a higher risk of complications and death from coronavirus disease 2019 (COVID19), thus vaccination is crucial in this population. Oncologic therapies can affect vaccination response, but few data are available about the immune response to mRNA SARS-CoV-2 vaccines in patients with breast cancer receiving cyclin-dependent kinases 4/6 inhibitors (CDK4/6i). Our study aimed to assess the immunogenicity and safety of the mRNA-1273 vaccine in patients treated with CDK4/6i in comparison with a group of volunteer health workers.Methods: We conducted a prospective, single-center study including patients with breast cancer treated with CDK4/6i and a comparative group of health care workers (HCW). Blood samples were collected before and after first dose administration, and after second dose. The primary endpoint was to compare the rate and magnitude of humoral and T-cell responses after full vaccination. Neutralizing antibodies titers, the correlation between neutralizing and anti-S antibodies, the incidence of COVID-19 after vaccination, and safety were defined as secondary objectives.Results: No differences were observed in the rate of either anti-S or neutralizing antibodies after full vaccination, being 100% in both groups. A positive correlation was found between neutralizing and anti-S antibodies. However, the rate of anti-S CD4 and CD8 T-cell response after complete vaccination was a 15% lower in the CDK4/6i group, although differences were not statistically significant (CD4 T-cell response 69.2% vs 84.6%; p 0.324; anti-S T-cell CD8 response 69.2% vs 84.6%; p 0.324). No differences in the incidence of COVID-19 after vaccination were found (19.2% vs 11.5%, p 0.703). Patients with vaccine breakthrough showed lower levels of anti-S antibody after the first dose (492.29 vs 157.96; p 0.029) and lower titers of neutralizing antibodies after full vaccination (p 0.068). The rate of adverse events was higher in patients treated with CDK4/6i. No serious adverse events were reported in any of the two groups.Conclusion: While a robust humoral response was observed in the CDK4/6i group, a limited T cell response was found, without differences in the rate of subsequent COVID-19. Further insight into the underlying mechanisms is crucial to improve breast cancer patients’ protection and to adjust vaccination strategies in this specific population.

Impact of SARS-CoV-2-specific memory B cells on the immune response after mRNA-based Comirnaty vaccine in seronegative health care workers (preprint)

Purpose To analyze the impact of SARS-COV-2-specific memory B cells (MBC) on the immune response after two doses of mRNA-based Comirnaty COVID-19 vaccine in seronegative health care workers. This study is seeking a rationale for boosting vaccines.Methods Longitudinal study including 31 seronegative health care workers with undetectable MBCs (IgG-MBC- group), 24 seronegative with detectable MBCs (IgG-MBC + group), and 24 seropositive with detectable MBCs (IgG + MBC + group). The level of neutralizing, anti-S IgG, IgA, and IgM antibodies was quantified by ELISA. In addition, specific memory B and T cells were quantified by flow cytometry.Results The level of specific MBCs, and isotypes, in the IgG-MBC- group was lower compared to that found in IgG-MBC+ (p = 0.0001) and IgG + MBC+ (p < 0.0001) groups, respectively. Neutralizing and anti-S IgG antibodies were at lower levels in the IgG-MBC- group after the vaccine. Specific MBCs directly correlated with specific CD4 + T cells (although not significant, p = 0.065), while no correlation was found with specific CD8 + T cells (p = 0.156) after the vaccine. In parallel, neutralizing antibodies only positively correlated with specific CD4 + T cells (p = 0.034).Conclusions IgG-MBC- individuals showed the worst humoral and cellular responses, both in frequency and magnitude, after vaccine. Individuals whose antibodies wane and become undetectable after a given period of time post vaccine and show no specific MBCs are less protected and hence are good candidates for boosting vaccine. On the other hand, seronegative individuals with specific MBC showed faster and higher responses compared to the IgG-MBC- group.

Analysis of the Immunogenicity of mRNA-1273 SARS-CoV-2 Vaccine in Breast Cancer Patients Treated With Cyclin-Dependent Kinases 4 and 6 Inhibitors (CDKi): Limited T-Cell Immunity Despite Satisfactory Humoral Response. (preprint)

SARS-CoV-2 vaccination in cancer patients has become crucial because of their higher risk of complications and death from COVID19. We performed a prospective study to assess the immunogenicity of SARS-CoV-2 vaccine in cancer patients treated with CDKi and compared their immune response with patients treated with chemotherapy. While a robust humoral response was observed in the CDKi patients compared with chemotherapy patients, limited T-cell immunity was achieved in both groups.

SARS-CoV-2 cellular immune response in uninfected health care workers with prolonged and close exposure to COVID-19 patients (preprint)

Health care workers (HCW) are at an increased risk since they are directly exposed to SARS-CoV-2 infected patients, nevertheless, some remained without the development of anti-SARS-CoV-2 antibodies, suggesting lesser susceptibility to infection1-5. This study aimed to ascertain a potential specific cellular immune response to SARS-CoV-2 in these largely exposed HCWs.In this cross-sectional, case-control study, we analyzed 39 exposed uninfected HCWs and 17 convalescent HCWs. Cellular immune response was evaluated after SARS-CoV-2 stimulation with peptide pools (proteins S, M, and N), using bead-based multiplex assay (12 cytokines).Overall, 94.8% of uninfected HCWs had some degree of specific cellular response to SARS-CoV-2 structural proteins that could be classified, according to the number of cytokine production, as strong (61.5%), partial (33.3%), and weak/no response (5.1%). Strong responders showed a higher anti-inflammatory cytokine production (IL5 and IL10, p<0.001 and 0.002, respectively), and similar (IFN-γ and TNF-α, p=0.435 and 0.532, respectively) or higher (IL12, p=0.021) pro-inflammatory production compared to convalescents, resulted in a predominantly Th2 response. This study demonstrated a consistent and polyfunctional immune cellular response after stimulation with SARS-CoV-2 peptides in extensively exposed individuals that should be considered to establish the infection susceptibility, the impact in herd immunity, and the risk of relapses.