Search

Background Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) has emerged throughout the world. Building knowledge around Covid‐19 is crucial to devise facts based approaches to respond efficiently against this pandemic. Aim We aimed to investigate pre‐existing humoral cross‐reactive immunity to SARS‐CoV‐2. Method We have tested the reactivity against SARS‐CoV‐2 nucleocapsid (N) antigen of sera collected from healthy healthcare volunteers in 2014. We assessed immunoglobulins reactive against SARS‐CoV‐2 N‐antigen using a well‐validated serological platform; Elecsys assay. Results Sera from 32 subjects (out of 135 [23.7%]) were reactive to SARS‐CoV‐2 N‐antigen, suggesting the presence of anti‐SARS‐CoV‐2 N‐antigen antibodies. Conclusion Although the clinical relevance of the observed reactivity can only be speculated and needs to be investigated, the implication of this finding for coronavirus disease 2019 seroepidemiological survey and vaccines' clinical trials is critical., This is the first report clearly showing a cross‐reactive humoral response against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Our data is adding to the accumulating data that point toward the existence of cross‐reactive immunity to SARS‐CoV‐2, as it showed that years before the coronavirus disease 2019 pandemic people had cross‐reactive antibodies against SARS‐CoV‐2.

HIV-exposed uninfected infants (HEU) represent a growing population in developing countries including Gabon. Several studies have shown the vulnerability of these infants toward infectious diseases. The aim of the study was to contribute to the global effort to understand how HIVexposure or anti retroviral therapy affects infants’ blood elements. We assessed HEU infants’ complete blood count using a blood analyzer instrument. Our investigations showed that among the observed clinically relevant hematological abnormalities events, thrombocytosis was the most prevalent clinically relevant hematological abnormality associated with HEU infants’. We showed that HEU infants had significantly higher platelets count than HUinfants. Therefore, higher level of platelets seems to characterize HEU infants when compared to HU infants.

Tuberculosis (TB) is the leading cause of death due to an infectious agent, but only a small fraction of those infected develop the disease. Cytokines are involved in the mediation and regulation of immunity, and their secretion patterns may reflect the infection status. To increase our understanding of immune response to M. tuberculosis infection, we conducted a cross-sectional study investigating M. tuberculosis infection status and comparing the release profiles of cytokines GM-CSF, IFN-γ, IL-1β, IL-10, IL-12 (p70), IL-2, IL-4, IL-5, IL-6, IL-8, TNF-α, in community controls (CCs) and healthy healthcare workers (HCWs) highly exposed to TB. Among HCWs and CCs, the probability of latent M. tuberculosis (LTB+) infection was respectively 5.4 (p = 0.002) and 3.4 (p = 0.006) times higher in men than women. The odds ratio of LTB infection was 4 times higher among HCWs in direct contact with active TB patients than other HCW (p = 0.01). Whole blood supernatant cytokine responses to M. tuberculosis antigens showed differential pro-inflammatory responses between HCWs and CCs. CCsLTB− had higher IL-1β responses than HCWsLTB− (p = 0.002). HCWsLTB+ had significantly higher IL-8 responses to M. tuberculosis antigens than HCWsLTB− (p = 0.003) and CCsLTB− (p = 0.015). HCWsLTB+/− showed weak but positive TNF-α responses to M. tuberculosis antigen stimulation compared to CCsLTB+/− (p ≤ 0.015). Looking at T-helper (1 and 2) responses, HCWsLTB+ and CCsLTB+ had significantly higher IFN-γ and IL-2 responses compared to HCWsLTB− and CCsLTB− (p LTB+ and CCsLTB+ than in non-infected CCsLTB− (p M. tuberculosis antigen specific responses in HCWsLTB+ varied based on active TB exposure gradient. HCWsLTB+ who were highly exposed to active TB (≥3 hours per day) had significantly higher IFN-γ and IL-8 responses (p ≤ 0.02) than HCWs LTB+ not in direct contact with active TB patients. HCWsLTB+ working with active TB patients for 5 to 31 years had a significantly enhanced secretion of proinflammatory cytokines (GM-CSF, IFN-γ, IL-1β, IL-2, IL-6, IL-8, IL-12p70, TNF-α) compared to HCWsLTB− (p LTB+ than HCWsLTB−. In conclusion, LTBI individuals controlling the M. tuberculosis infection have an enhanced TB specific Th1-cytokines/proinflammatory response combined with selected Th2 type/anti-inflammatory cytokines induction.

Pathogen sensing and recognition through pattern recognition receptors, and subsequent production of pro-inflammatory cytokines, is the cornerstone of the innate immune system. Despite the fact that HIV-exposed uninfected (HEU) infants are prone to serious bacterial infections, no study has focused on the functionality of their bacteria recognition system. This is the first study to investigate baseline levels of three critically important immune response molecules in this population: complement component (C)-3, toll-like receptor (TLR)-4, and C-reactive protein (CRP). We enrolled 16 HEU and 6 HIV-unexposed (HU) infants. TLR4 function was investigated by stimulating whole blood with increasing concentrations of TLR4-agonist ultrapure lipopolysaccharides. TLR4/TLR4-agonist dose response were assessed by measuring IL-6 secretion. Complement C3 and CRP were measured by photo spectrometry. Data showed no significant differences in baseline concentration of CRP between HEU and HU infants. Complement C3 was significantly higher in HEU infants than HU infants. TLR4 anergy was observed in 7 of 12 HEU infants, whereas the rest of HEU infants (n = 4) and the control HU infants tested (n = 3) showed responsive TLR4. None of the HEU infants investigated in this study had severe infections in the year after their birth. In conclusion, TLR4 anergy can occur in HEU infants without necessarily translating to increased vulnerability to infectious diseases.

An increased risk of serious bacterial infections in HIV exposed uninfected (HEU) infants has been demonstrated. Although neutrophils are essential for the protection of infants against bacterial infections, no study has investigated their profile in HEU infants to date. In this study, we assessed the function of neutrophils in HEU infants using the Nitroblue tetrazolium (NBT) reduction test. Among 25 HEU infants, 9 (36%) showed a reduced ability of their neutrophils to produce Reactive Oxygen Species (ROS) upon stimulation with bacteria. No alteration of total neutrophil counts was noted in the blood of HEU infants indicating that the alteration observed in the 36% of HEU infants may only be functional. Conclusively, impaired neutrophil function could be a factor of vulnerability in HEU infants.