High seroprevalence of SARS-CoV-2 in white-tailed deer (Odocoileus virginianus) at one of three captive cervid facilities in Texas

Free-ranging white-tailed deer (Odocoileus virginanus) across the United States are increasingly recognized as involved in SARS-CoV-2 transmission cycles. Through a cross-sectional study of 80 deer at three captive cervid facilities in central and southern Texas, we provide evidence of 34 of 36 (94.4%) white-tailed deer at a single captive cervid facility seropositive for SARS-CoV-2 by neutralization assay (PRNT90), with endpoint titers as high as 1280. In contrast, all tested white-tailed deer and axis deer (Axis axis) at two other captive cervid facilities were seronegative, and SARS-CoV-2 RNA was not detected in respiratory swabs from deer at any of the three facilities. These data support transmission among captive deer that cannot be explained by human contact for each infected animal, as only a subset of the seropositive does had direct human contact. The facility seroprevalence was more than double of that reported from wild deer, suggesting that the confined environment may facilitate transmission. Further exploration of captive cervids and other managed animals for their role in the epizootiology of SARS-CoV-2 is critical for understanding impacts on animal health and the potential for spillback transmission to humans or other animal taxa.

The TZM-bl Reporter Cell Line Expresses Kynureninase That Can Neutralize 2F5-like Antibodies in the HIV-1 Neutralization Assay

Induction of broadly neutralizing antibodies targeting ectodomain of the transmembrane (TM) glycoprotein gp41 HIV-1 provides a basis for the development of a universal anti-viral vaccine. The HeLa cell-derived TZM-bl reporter cell line is widely used for the estimation of lentiviruses neutralization by immune sera. The cell line is highly permissive to infection by most strains of HIV, SIV, and SHIV. Here we demonstrated that TZM-bl cells express a 48 kDa non-glycosylated protein (p48) recognized by broadly neutralizing monoclonal antibody (mAb) 2F5 targeting the ELDKWA (aa 669–674) epitope of gp41TM of HIV-1. A significant amount of p48 was found in the cell supernatant. The protein was identified as human kynureninase (KYNU), which has the ELDKWA epitope. The protein is further called “p48 KYNU”. The HIV-1 neutralization by mAb 2F5 and 4E10 in the presence of p48KYNU was tested on Jurkat and TZM-bl cells. It was demonstrated that p48KYNU reduces neutralization by 2F5-like antibodies, but it has almost no effect on mAb 4E10. Therefore, p48KYNU can attenuate HIV-1 neutralization by 2F5-like antibodies and hence create false-negative results. Thus, previously tested immune sera that recognized the ELDKWA-epitope and demonstrated a “weak neutralization” of HIV-1 in TZM-bl assay should be reevaluated.

Dengue virus seroprevalence study in Bangphae district, Ratchaburi, Thailand: A cohort study in 2012-2015

Background To determine the seroprevalence and transmission dynamics of dengue virus (DENV), age-stratified longitudinal serological surveys were conducted in Bangphae district, Ratchaburi province, Thailand, for 3 years between April 2012 and April 2015. Methodology The surveys enrolled 2012 healthy children and adults between 1 and 55 years-of-age, and a longitudinal serosurvey of six repeated bleeds of the same cohort of individuals was conducted every 8 months for the first 2 years (M0, M8, M16) and every half a year (M24, M30, M36) for the rest of the study period. All samples were tested using in-house indirect sandwich dengue IgG ELISA to determine DENV antibody titer, and 640 paired samples which showed rising of DENV IgG titers in paired serum were further tested using in-house neutralization assay, Plaque Reduction Neutralization Test (PRNT50). Principal findings When compared against the gold standard based on the results of PRNT50, sensitivity and specificity of indirect ELISA were found to be both about 85%. The overall DENV IgG positivity determined by ELISA was 74.3% in 2012 and increased to 79.4% by the final sample collection in 2015. In our study sample, more than 98% of subjects older than 25 years were found to be seropositive. Among 518 IgG negative subjects at enrollment, the seroconversion rates were measured in paired bleeds; the rates (between successive visits, approximately 6 months) ranged between 4.8% (between M16 and M24) and 14.7% (between M0 and M8). The dominant serotype of primary DENV infection cases based on seroconversion was identified from the PRNT results and it was DENV-2. Conclusions Our study documented high levels of seroprevalence and rate of transmission. Given the importance of the serostatus and disease burden in consideration for dengue vaccine introduction, our data could be used in decision-making on implementation of various dengue control and preventive measures.

Neutralization of ancestral SARS-CoV-2 and variants Alpha, Beta, Gamma, Delta, Zeta and Omicron by mRNA vaccination and infection-derived immunity through homologous and heterologous variants

Emerging SARS-CoV-2 variants of concern/interest (VOC/VOI) raise questions about effectiveness of neutralizing antibodies derived from infection or vaccination. As the population immunity to SARS-CoV-2 has become more complex due to prior infection and/or vaccination, understanding the antigenic relationship between variants is needed. Here, we have assessed in total 104 blood specimens from convalescent individuals after infection with early-pandemic SARS-CoV-2 (pre-VOC) or with Alpha, Beta, Gamma or Delta, post-vaccination after double-dose mRNA-vaccination and break through infections due to Delta or Omicron. Neutralization against seven authentic SARS-CoV-2 isolates (B.1, Alpha, Beta, Gamma, Delta, Zeta, Omicron) was assessed by plaque-reduction neutralization assay. We found highest neutralization titers against the homologous (previously infecting) variant, with lower neutralization efficiency against heterologous variants. Significant loss of neutralization for Omicron was observed but to a varying degree depending on previously infecting variant (23.0-fold in Beta-convalescence up to 56.1-fold in Alpha-convalescence), suggesting that infection-derived immunity varies, but independent of the infecting variant is only poorly protective against Omicron. Of note, Zeta VOI showed also pronounced escape from neutralization of up to 28.2-fold in Alpha convalescent samples. Antigenic mapping reveals both Zeta and Omicron as separate antigenic clusters. Double dose vaccination showed robust neutralization for Alpha, Beta, Gamma, Delta and Zeta, with fold-change reduction of only 2.8 (for Alpha) up to 6.9 (for Beta). Escape from neutralization for Zeta was largely restored in vaccinated individuals, while Omicron still showed a loss of neutralization of 85.7-fold compared to pre-VOC SARS-CoV-2. Combined immunity from infection followed by vaccination or vaccine breakthrough infection showed highest titers and most robust neutralization for heterologous variants. Breakthrough infection with Delta showed only 12.5-fold reduced neutralization for Omicron, while breakthrough infection with Omicron showed only a 1.5-fold loss for Delta, suggests that infection with antigenically different variants can boost immunity for antigens closer to the vaccine strain. Antigenic cartography showed also a tendency towards broader neutralizing capacity for heterologous variants. We conclude that the complexity of background immunity needs to be taken into account when assessing new VOCs. Development towards separate serotypes such as Zeta was already observed before Omicron emergence, thus other factors than just immune escape must contribute to Omicrons rapid dominance. However, combined infection/vaccination immunity could ultimately lead to broad neutralizing capacity also against non-homologous variants.

DISAPPEARANCE OF ANTIBODIES IN COVID-19 MYTHS ORREALITY

Objective: To explore the disappearance of neutralizing antibodies from patients, their myths, and facts. Study Design: Cross-sectional study. Place and Duration of Study: Combined Military Hospital Multan Pakistan, from Jul 2021 to Aug 2021. Methodology: A total of 100 blood samples were collected from 100 COVID-19 patients. These 100 patients were followed up for a period of 3 months. Antibodies were determined with the modified neutralization assay method and enzyme-linked immuno-sorbent assay (ELISA). Results: The antibody level by NA and ELISA peaked on days 30-35 then decreased slightly. In multivariate analysis, patients aged 25-35, 36-56, and 57-84 years had a higher neutralizing antibody level than those aged 10-21 years. The patient with the worst clinical manifestation had a higher neutralizing antibody titer. In serum samples, IgG was undetectable at 18.3% and 11% and the geographical mean reciprocal titers dropped from 244 at 3-month period and neutralizing antibodies, the geographical mean reciprocal titers dropped from 874 at 3 months. Conclusion: All COVID-19 patients were seropositive and significantly neutralizing antibody response. Neutralizing antibody levels depend on the time after the onset of symptoms, age, and severity of the disease.

SARS-CoV-2 Omicron neutralization by therapeutic antibodies, convalescent sera, and post-mRNA vaccine booster

The rapid spread of the highly contagious Omicron variant of SARS-CoV-2 along with its high number of mutations in the spike gene has raised alarm about the effectiveness of current medical countermeasures. To address this concern, we measured neutralizing antibodies against Omicron in three important settings: (1) post-vaccination sera after two and three immunizations with the Pfizer/BNT162b2 vaccine, (2) convalescent sera from unvaccinated individuals infected by different variants, and (3) clinical-stage therapeutic antibodies. Using a pseudovirus neutralization assay, we found that titers against Omicron were low or undetectable after two immunizations and in most convalescent sera. A booster vaccination significantly increased titers against Omicron to levels comparable to those seen against the ancestral (D614G) variant after two immunizations. Neither age nor sex were associated with differences in post-vaccination antibody responses. Only three of 24 therapeutic antibodies tested retained their full potency against Omicron and high-level resistance was seen against fifteen. These findings underscore the potential benefit of booster mRNA vaccines for protection against Omicron and the need for additional therapeutic antibodies that are more robust to highly mutated variants.

Neutralization against Omicron SARS-CoV-2 from previous non-Omicron infection

The explosive spread of the Omicron SARS-CoV-2 variant underscores the importance of analyzing the cross-protection from previous non-Omicron infection. We developed a high-throughput neutralization assay for Omicron SARS-CoV-2 by engineering the Omicron spike gene into an mNeonGreen USA-WA1/2020 SARS-CoV-2 (isolated in January 2020). Using this assay, we determined the neutralization titers of patient sera collected at 1- or 6-months after infection with non-Omicron SARS-CoV-2. From 1- to 6-month post-infection, the neutralization titers against USA-WA1/2020 decreased from 601 to 142 (a 4.2-fold reduction), while the neutralization titers against Omicron-spike SARS-CoV-2 remained low at 38 and 32, respectively. Thus, at 1- and 6-months after non-Omicron SARS-CoV-2 infection, the neutralization titers against Omicron were 15.8- and 4.4-fold lower than those against USA-WA1/2020, respectively. The low cross-neutralization against Omicron from previous non-Omicron infection supports vaccination of formerly infected individuals to mitigate the health impact of the ongoing Omicron surge.

Long Term Protective Immunity to Goatpox in Goats After Single Immunization with a Live Attenuated Goatpox Vaccine

In this study, duration of immunity following single shot vaccination using an attenuated goatpox vaccine (GTPV/Uttarkashi/1978) was evaluated in sero-negative kids for 52 months. Long term immunity was evaluated by clinical protection upon virulent virus challenge and serum neutralization assay applied for serum samples. Rise in level of GTPV specific antibodies was found to be maximum on 21 days post vaccination, which was maintained between 1 and 2 years of immunization with steady decline. Upon virulent virus challenge on 21 days, 12, 24, 42 and 52 months post vaccination, protection in all vaccinated animals was evident, whereas, control animals developed severe clinical disease. This is for the first time that long term immunity of a live goatpox vaccine has been investigated up to 52 months of post-vaccination in goats and it has immense potential in controlling and eradicating goatpox from an enzootic situation.

mRNA-1273 and BNT162b2 mRNA vaccines have reduced neutralizing activity against the SARS-CoV-2 Omicron variant

The BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines generate potent neutralizing antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the global emergence of SARS-CoV-2 variants with mutations in the spike protein, the principal antigenic target of these vaccines, has raised concerns over the neutralizing activity of vaccine-induced antibody responses. The Omicron variant, which emerged in November 2021, consists of over 30 mutations within the spike protein. Here, we used an authentic live virus neutralization assay to examine the neutralizing activity of the SARS-CoV-2 Omicron variant against mRNA vaccine-induced antibody responses. Following the 2nd dose, we observed a 30-fold reduction in neutralizing activity against the omicron variant. Through six months after the 2nd dose, none of the sera from naive vaccinated subjects showed neutralizing activity against the Omicron variant. In contrast, recovered vaccinated individuals showed a 22-fold reduction with more than half of the subjects retaining neutralizing antibody responses. Following a booster shot (3rd dose), we observed a 14-fold reduction in neutralizing activity against the omicron variant and over 90% of boosted subjects showed neutralizing activity against the omicron variant. These findings show that a 3rd dose is required to provide robust neutralizing antibody responses against the Omicron variant.