Analysis of 772 complete severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes from early in the Boston-area epidemic revealed numerous introductions of the virus, a small number of ...which led to most cases. The data revealed two superspreading events. One, in a skilled nursing facility, led to rapid transmission and significant mortality in this vulnerable population but little broader spread, whereas other introductions into the facility had little effect. The second, at an international business conference, produced sustained community transmission and was exported, resulting in extensive regional, national, and international spread. The two events also differed substantially in the genetic variation they generated, suggesting varying transmission dynamics in superspreading events. Our results show how genomic epidemiology can help to understand the link between individual clusters and wider community spread.
•Serum IgG developed in 95% mildly symptomatic patients by day 14 and all seroconverted by day 30.•Serum IgM and IgA antibody responses were lower and less frequent than corresponding IgG ...responses.•Serum IgM and IgA responses peaked and declined earlier in 100% of mild symptomatic individuals.•<45% of asymptomatic infected individuals had seroconverted by day 30 post-PCR diagnosis.•Impact on modeling of herd immunity.
Studies on serological responses following coronavirus disease-2019 (COVID-19) have been published primarily in individuals who are moderately or severely symptomatic, but there are few data from individuals who are mildly symptomatic or asymptomatic.
We measured IgG, IgM, and IgA to the receptor-binding domain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by using enzyme-linked immunosorbent assay in mildly symptomatic (n = 108) and asymptomatic (n = 63) on days 1, 7, 14, and 30 following RT-PCR confirmation in Bangladesh and when compared with pre-pandemic samples, including healthy controls (n = 73) and individuals infected with other viruses (n = 79).
Mildly symptomatic individuals developed IgM and IgA responses by day 14 in 72% and 83% of individuals, respectively, while 95% of individuals developed IgG response, and rose to 100% by day 30. In contrast, individuals infected with SARS-CoV-2 but who remained asymptomatic developed antibody responses significantly less frequently, with only 20% positive for IgA and 22% positive for IgM by day 14, and 45% positive for IgG by day 30 after infection.
These results confirm immune responses are generated following COVID-19 who develop mildly symptomatic illness. However, those with asymptomatic infection do not respond or have lower antibody levels. These results will impact modeling needed for determining herd immunity generated by natural infection or vaccination.
The World Health Organization recommends the use of oral cholera vaccine (OCV) in cholera control efforts. Euvichol®, pre-qualified in 2015, is the leading component of the Global OCV stockpile, but ...data on its field effectiveness are limited. To evaluate Euvichol® vaccine effectiveness (VE), we conducted a case-control study between September 2018 to March 2020 following an OCV campaign in November 2017 in Haiti.
Cases were individuals with acute watery diarrhea. Stool samples were tested by culture and real-time polymerase chain reaction of the Vibrio cholerae ctxA gene. Cases were matched to four community controls without diarrhea by residence, enrollment time, age, and gender, and interviewed for sociodemographics, risk factors, and self-reported vaccination. Cholera cases were analyzed by conditional logistic regression in the VE study. Non-cholera diarrhea cases were analyzed in a bias-indicator study.
We enrolled 15 cholera cases matched to 60 controls, and 63 non-cholera diarrhea cases matched to 249 controls. In the VE analysis, eight (53%) cases reported vaccination with any number of doses compared to 43 (72%) controls. Adjusted two-dose OCV VE was 69% (95% CI -71 to 94%).
Between 10-27 months after vaccination, Euvichol® was effective and similar to Shanchol™, suggesting that it can serve as one component of multi-sectoral comprehensive cholera control.
Relatively few coronavirus disease cases and deaths have been reported from sub-Saharan Africa, although the extent of its spread remains unclear. During August 10–September 11, 2020, we recruited ...2,214 participants for a representative household-based cross-sectional serosurvey in Juba, South Sudan. We found 22.3% of participants had severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor binding domain IgG titers above prepandemic levels. After accounting for waning antibody levels, age, and sex, we estimated that 38.3% (95% credible interval 31.8%–46.5%) of the population had been infected with SARS-CoV-2. At this rate, for each PCR–confirmed SARS-CoV-2 infection reported by the Ministry of Health, 103 (95% credible interval 86–126) infections would have been unreported, meaning SARS-CoV-2 has likely spread extensively within Juba. We also found differences in background reactivity in Juba compared with Boston, Massachusetts, USA, where the immunoassay was validated. Our findings underscore the need to validate serologic tests in sub-Saharan Africa populations.
Estimates of incidence based on medically attended cholera can be severely biased. Vibrio cholerae O1 leaves a lasting antibody signal and recent advances showed that these can be used to estimate ...infection incidence rates from cross-sectional serologic data. Current laboratory methods are resource intensive and challenging to standardize across laboratories. A multiplex bead assay (MBA) could efficiently expand the breadth of measured antibody responses and improve seroincidence accuracy. We tested 305 serum samples from confirmed cholera cases (4 to 1083 d postinfection) and uninfected contacts in Bangladesh using an MBA (IgG/IgA/IgM for 7 Vibrio cholerae O1-specific antigens) as well as traditional vibriocidal and enzyme-linked immunosorbent assays (2 antigens, IgG, and IgA). While postinfection vibriocidal responses were larger than other markers, several MBA-measured antibodies demonstrated robust responses with similar half-lives. Random forest models combining all MBA antibody measures allowed for accurate identification of recent cholera infections (e.g., past 200 days) including a cross-validated area under the curve (cvAUC
) of 92%, with simpler 3 IgG antibody models having similar accuracy. Across infection windows between 45 and 300 days, the accuracy of models trained on MBA measurements was non-inferior to models based on traditional assays. Our results illustrated a scalable cholera serosurveillance tool that can be incorporated into multipathogen serosurveillance platforms.
Reliable estimates of cholera incidence are challenged by poor clinical surveillance and health-seeking behavior biases. We showed that cross-sectional serologic profiles measured with a high-throughput multiplex bead assay can lead to accurate identification of those infected with pandemic Vibrio cholerae O1, thus allowing for estimates of seroincidence. This provides a new avenue for understanding the epidemiology of cholera, identifying priority areas for cholera prevention/control investments, and tracking progress in the global fight against this ancient disease.
The effects of sanitation and hygiene interventions on the gut microbiome and enteric pathogen burden are not well understood. We measured the association between free chlorine residue (FCR) levels ...in drinking water, microbiome composition, and stool enteric pathogens in infants and young children in Haiti.OBJECTIVEThe effects of sanitation and hygiene interventions on the gut microbiome and enteric pathogen burden are not well understood. We measured the association between free chlorine residue (FCR) levels in drinking water, microbiome composition, and stool enteric pathogens in infants and young children in Haiti.FCR levels were measured in household drinking water and enteric pathogen burden was evaluated using multiplex RT-PCR of stool among 131 children from one month to five years of age living in Mirebalais, Haiti. Microbiome profiling was performed using metagenomic sequencing.METHODSFCR levels were measured in household drinking water and enteric pathogen burden was evaluated using multiplex RT-PCR of stool among 131 children from one month to five years of age living in Mirebalais, Haiti. Microbiome profiling was performed using metagenomic sequencing.Most individuals lived in households with undetectable FCR measured in the drinking water (112/131, 86%). Detection of enteric pathogen DNA in stool was common and did not correlate with household water FCR. The infant microbiome in households with detectable FCR demonstrated reduced richness (fewer total number of species, P=0.04 Kruskall-Wallis test) and less diversity by Inverse Simpson measures (P=0.05) than households with undetectable FCR. Infants in households with a detectable FCR were more likely to have abundant Bifidobacterium. Using in vitro susceptibility testing, we found that some Bifidobacterium species were resistant to chlorine.RESULTSMost individuals lived in households with undetectable FCR measured in the drinking water (112/131, 86%). Detection of enteric pathogen DNA in stool was common and did not correlate with household water FCR. The infant microbiome in households with detectable FCR demonstrated reduced richness (fewer total number of species, P=0.04 Kruskall-Wallis test) and less diversity by Inverse Simpson measures (P=0.05) than households with undetectable FCR. Infants in households with a detectable FCR were more likely to have abundant Bifidobacterium. Using in vitro susceptibility testing, we found that some Bifidobacterium species were resistant to chlorine.FCR in household drinking water did not correlate with enteric pathogen burden in our study.CONCLUSIONSFCR in household drinking water did not correlate with enteric pathogen burden in our study.
Objectives
Uncovering and addressing disparities in infectious disease outbreaks require a rapid, methodical understanding of local epidemiology. We conducted a seroprevalence study of SARS-CoV-2 ...infection in Holyoke, Massachusetts, a majority Hispanic city with high levels of socio-economic disadvantage to estimate seroprevalence and identify disparities in SARS-CoV-2 infection.
Methods
We invited 2000 randomly sampled households between 11/5/2020 and 12/31/2020 to complete questionnaires and provide dried blood spots for SARS-CoV-2 antibody testing. We calculated seroprevalence based on the presence of IgG antibodies using a weighted Bayesian procedure that incorporated uncertainty in antibody test sensitivity and specificity and accounted for household clustering.
Results
Two hundred eighty households including 472 individuals were enrolled. Three hundred twenty-eight individuals underwent antibody testing. Citywide seroprevalence of SARS-CoV-2 IgG was 13.1% (95% CI 6.9–22.3) compared to 9.8% of the population infected based on publicly reported cases. Seroprevalence was 16.1% (95% CI 6.2–31.8) among Hispanic individuals compared to 9.4% (95% CI 4.6–16.4) among non-Hispanic white individuals. Seroprevalence was higher among Spanish-speaking households (21.9%; 95% CI 8.3–43.9) compared to English-speaking households (10.2%; 95% CI 5.2–18.0) and among individuals in high social vulnerability index (SVI) areas based on the CDC SVI (14.4%; 95% CI 7.1–25.5) compared to low SVI areas (8.2%; 95% CI 3.1–16.9).
Conclusions
The SARS-CoV-2 IgG seroprevalence in a city with high levels of social vulnerability was 13.1% during the pre-vaccination period of the COVID-19 pandemic. Hispanic individuals and individuals in communities characterized by high SVI were at the highest risk of infection. Public health interventions should be designed to ensure that individuals in high social vulnerability communities have access to the tools to combat COVID-19.
Previously we identified an intra-S-phase cell cycle checkpoint elicited by the DNA-damaging carcinogen benzoapyrene-dihydrodiol epoxide (BPDE). Here we have investigated the roles of lesion bypass ...DNA polymerases polκ and polη in the BPDE-induced S-phase checkpoint. BPDE treatment induced the re-localization of an ectopically expressed green fluorescent protein-polκ fusion protein to nuclear foci containing sites of active DNA synthesis in human lung carcinoma H1299 cells. In contrast, a similarly expressed yellow fluorescent protein-polη fusion protein showed a constitutive nuclear focal distribution at replication forks (in the same cells) that was unchanged in response to BPDE. BPDE-induced formation of green fluorescent protein-polκ nuclear foci was temporally coincident with checkpoint-mediated S-phase arrest. Unlike “wild-type” cells, Polk-/- mouse embryonic fibroblasts (MEFs) failed to recover from BPDE-induced S-phase arrest, while exhibiting normal recovery from S-phase arrest induced by ionizing radiation and hydroxyurea. XPV fibroblasts lacking polη showed a normal S-phase checkpoint response to BPDE (but failed to recover from the UV light-induced S-phase checkpoint), in sharp contrast to Polk-/- MEFs. The persistent S-phase arrest in BPDE-treated Polk-/- cells was associated with increased levels of histone γH2AX (a marker of DNA double-strand breaks (DSBs)) and activation of the DSB-responsive kinases ATM and Chk2. These data suggest that in the absence of polκ, replication forks stall at sites of damage and collapse and generate DSBs. Therefore, we conclude that the trans-lesion synthesis enzyme polκ is specifically required for normal recovery from the BPDE-induced S-phase checkpoint.
Defects in DNA replication are implicated as early and causal events in malignancy. However, the immediate effects of impaired DNA replication licensing on cell cycle progression of non-malignant ...human cells are unknown. Therefore, we have investigated the acute effects of Mcm7 ablation using synchronized cultures of untransformed Human Dermal Fibroblasts (HDF). Mcm7 ablation elicited a G1 delay associated with impaired activation of CDK4 and CDK2 and reduced Rb phosphorylation. The cell cycle delay of Mcm7-ablated cells was not associated with a DNA damage response. However, levels of cyclin D1 mRNA were specifically reduced and binding of RNA Polymerase II to the CYCD1 promoter was decreased in Mcm7-depleted cells. Similar to Mcm7-deficiency, Mcm2- or Cdc6-depletion led to impaired cyclin D expression. Ectopic over-expression of Cdc6 in quiescent cells promoted cyclin D1 expression, CDK4 activation and G1 progression. Therefore timely and efficient expression of cyclin D1 during G1 phase requires replication licensing. Reconstitution of cyclin D1 expression was insufficient to correct the G1 delay of Mcm7-depleted cells, indicating that additional cell cycle events during G1are dependent on replication licensing. However, ectopic expression of the HPV-E7 oncoprotein, and the resulting bypass of the requirement for cyclin D1-Rb signaling enabled Mcm7-depleted cells to enter S-phase. HPV-E7-induced S-phase entry of Mcm7-depleted cells led to a DNA damage response, a hallmark of pre-malignancy. Taken together, our results suggest the existence of a 'replication licensing restriction point' that couples pre-RC assembly with G1 progression in normal cells to minimize replication stress, DNA damage and tumorigenesis.
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