Seroprevalence and risk factors of SARS-CoV-2 infection in an urban informal settlement in Nairobi, Kenya, December 2020

Introduction: Urban informal settlements may be disproportionately affected by the COVID-19 pandemic due to overcrowding and other socioeconomic challenges that make adoption and implementation of public health mitigation measures difficult. We conducted a seroprevalence survey in the Kibera informal settlement, Nairobi, Kenya, to determine the extent of SARS-CoV-2 infection. Methods: Members of randomly selected households from an existing population-based infectious disease surveillance (PBIDS) provided blood specimens between 27th November and 5th December 2020. The specimens were tested for antibodies to the SARS-CoV-2 spike protein. Seroprevalence estimates were weighted by age and sex distribution of the PBIDS population and accounted for household clustering. Multivariable logistic regression was used to identify risk factors for individual seropositivity. Results: Consent was obtained from 523 individuals in 175 households, yielding 511 serum specimens that were tested. The overall weighted seroprevalence was 43.3% (95% CI, 37.4 – 49.5%) and did not vary by sex. Of the sampled households, 122(69.7%) had at least one seropositive individual. The individual seroprevalence increased by age from 7.6% (95% CI, 2.4 – 21.3%) among children (<5 years), 32.7% (95% CI, 22.9 – 44.4%) among children 5 – 9 years, 41.8% (95% CI, 33.0 – 51.1%) for those 10-19 years, and 54.9%(46.2 – 63.3%) for adults (≥20 years). Relative to those from medium-sized households (3 and 4 individuals), participants from large (≥5 persons) households had significantly increased odds of being seropositive, aOR, 1.98(95% CI, 1.17 – 1.58), while those from small-sized households (≤2 individuals) had increased odds but not statistically significant, aOR, 2.31 (95% CI, 0.93 – 5.74). Conclusion: In densely populated urban settings, close to half of the individuals had an infection to SARS-CoV-2 after eight months of the COVID-19 pandemic in Kenya. This highlights the importance to prioritize mitigation measures, including COVID-19 vaccine distribution, in the crowded, low socioeconomic settings.

Immune transcriptomes of highly exposed SARS-CoV-2 asymptomatic seropositive versus seronegative individuals from the Ischgl community

SARS-CoV-2 infection ranges from asymptomatic to severe with lingering symptomatology in some. This prompted investigation of whether or not asymptomatic disease results in measurable immune activation post-infection. Immune activation following asymptomatic SARS-CoV-2 infection was characterized through a comparative investigation of the immune cell transcriptomes from 43 asymptomatic seropositive and 52 highly exposed seronegative individuals from the same community 4–6 weeks following a superspreading event. Few of the 95 individuals had underlying health issues. One seropositive individual reported Cystic Fibrosis and one individual reported Incontinentia pigmenti. No evidence of immune activation was found in asymptomatic seropositive individuals with the exception of the Cystic Fibrosis patient. There were no statistically significant differences in immune transcriptomes between asymptomatic seropositive and highly exposed seronegative individuals. Four positive controls, mildly symptomatic seropositive individuals whose blood was examined 3 weeks following infection, showed immune activation. Negative controls were four seronegative individuals from neighboring communities without COVID-19. All individuals remained in their usual state of health through a five-month follow-up after sample collection. In summary, whole blood transcriptomes identified individual immune profiles within a community population and showed that asymptomatic infection within a super-spreading event was not associated with enduring immunological activation.

Patterns and persistence of SARS-CoV-2 IgG antibodies in a US metropolitan site

BackgroundEstimates of seroprevalence to SARS-CoV-2 vary widely. We ascertained IgG levels across a single US metropolitan site, Chicago, over the 2020 summer, a period when restrictions on activities had been lifted.MethodsWe utilized a self-sampled dried blood spot assay to quantitatively monitor antibodies to the receptor binding domain (RBD) of the spike glycoprotein of SARS-CoV-2 in 1545 participants, with return of blood spot cards either by mail or in-person drop-off.ResultsSeroprevalence was 19.8%, with no significant difference between method of contact, or between essential and non-essential workers. Only a small number (1.2%) of participants reported having had a diagnosis of COVID-19 based on virus detection, consistent with a 16-fold greater exposure to SARS-CoV-2 measured by serology than detected by viral testing. Only a modest correlation was observed between having antibodies to SARS-CoV-2 nucleocapsid compared to RBD, with many only having detectable anti-RBD antibodies. From a subset of those who participated in repeat testing, three-quarters of seropositive individuals retained detectable antibodies for at least 120 days. One seropositive individual experienced a strong boost in IgG levels following a symptomatic illness, suggestive of potential re-exposure.ConclusionsThese data underscore the importance of a self-collected, quantitative assay with adequate sensitivity to detect antibodies at the lower levels among non-hospitalized persons with community-acquired exposure to COVID-19.

Concomitant Infections of Influenza A H1N1 and Disseminated Cryptococcosis in an HIV Seropositive Patient

ABSTRACTRespiratory viral infections, especially influenza have a potential to form a fatal association with cryptococcosis in the setting of compromised immunity. Considering the lethality of these two infections, we report an unusual case of dual infection of pandemic influenza A H1N1 and disseminated cryptococcosis in an HIV seropositive individual.

Human neutralizing human immunodeficiency virustype 2-specific Fab molecules generated by phage display

A panel of human immunodeficiency virus type 2 (HIV-2)-neutralizing, recombinant Fab fragments was generated by using the phage display technique. The combinatorial library was derived from an asymptomatic, HIV-2-seropositive individual and constructed on the surface of filamentous phage by using the pComb3 phagemid vector and then screened against native HIV-2 envelope glycoprotein (gp125). Ten of 30 Fab fragments generated displayed strong reactivity in an ELISA and were therefore selected for further study. Six of these possessed neutralizing capacity, with titres varying from 20 to 80 against the homologous HIV-2 strain, and one also had a weak neutralizing capacity against a heterologous HIV-2 isolate, K135. Sequencing of the heavy chain CDR3 regions showed that the gp125-specific Fabs represented individual clones. These reagents may be useful for studies on the conformational structures of the HIV-2 envelope antigens and their immunogenicity, which may help in vaccine design. Furthermore, the cloned Fab genes may be transformed into whole IgG for eukaryotic expression, and as such used for therapeutic and immunoprophylactic studies in HIV-2-infected macaques and, possibly, for human immunoprophylaxis against HIV-2.