Evidence of Reduced Virulence and Increased Colonization among Pneumococcal Isolates of Serotype 3 Clade II Lineage in Mice

Recent phylogenetic profiling of pneumococcal serotype 3 (Pn3) isolates revealed a dynamic interplay among major lineages with the emergence and global spread of a variant termed Clade II. The cause of Pn3 clade II dissemination along with epidemiological and clinical ramifications are currently unknown. Here, we sought to explore biological characteristics of dominant Pn3 clades in a mouse model of pneumococcal invasive disease and carriage. Carriage and virulence potential were strain dependent with marked differences among clades. We found that clinical isolates from Pn3 clade II are less virulent and less invasive in mice compared to clade I isolates. We also observed that clade II isolates are carried for longer and at higher bacterial densities in mice compared to clade I isolates. Taken together, our data suggest that the epidemiological success of Pn3 clade II could be related to alterations in the pathogen's ability to cause invasive disease and to establish a robust carriage episode.

Comparison of pneumococcal immunogenicity elicited by the PCV13 and PCV15 vaccines in adults 18 through 49 years of age

AIM

Pneumococcal conjugate vaccines (PCV13, PCV15, PCV20) effectively target the capsular polysaccharides of the most common disease-causing Streptococcus pneumoniae serotypes. In this short communication, we analyzed healthy participants who received PCV13 and PCV15 vaccines as part of a recently concluded exploratory clinical trial and report antibody responses to the 13 shared serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F) as well as functional OPA responses to serotype 3.

METHODS

Sera from 87 adult participants (18 through 49 years of age) randomized to receive either PCV13 or PCV15 were collected (n = 46 or n = 41, respectively), from 17 study centers in the US. IgG concentrations of the 13 shared serotypes and serotype 3-specific OPA titers were analyzed before and 1 month after vaccination using internally validated assays.

RESULTS

At 1 month after vaccination, IgG GMCs of the 13 shared serotypes in PCV13 were similar to those for PCV15. Specifically, serotype 3 OPA GMTs and 95% CIs were similar 1 month after vaccination for PCV13 (62.9 [48.9, 80.9]) and PCV15 (71.1 [50.9, 99.2]).

CONCLUSION

In healthy participants who received either PCV13 or PCV15, similar serotype-specific responses were observed between all shared serotypes when a uniform validated internal assay was used. Of note, data from this study suggest that both vaccines induce similar functional antibody responses against pneumococcal serotype 3.

Animal models for studying covid-19, prevention, and therapy: Pathology and disease phenotypes

Translational models have played an important role in the rapid development of safe and effective vaccines and therapeutic agents for the ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Animal models recapitulating the clinical and underlying pathological manifestations of COVID-19 have been vital for identification and rational design of safe and effective vaccines and therapies. This manuscript provides an overview of commonly used COVID-19 animal models and the pathologic features of SARS-CoV-2 infection in these models in relation to their clinical presentation in humans. Also discussed are considerations for selecting appropriate animal models for infectious diseases such as COVID-19, the host determinants that can influence species-specific susceptibility to SARS-CoV-2, and the pathogenesis of COVID-19. Finally, the limitations of currently available COVID-19 animal models are highlighted.

Modeling SARS-CoV-2: Comparative Pathology in Rhesus Macaque and Golden Syrian Hamster Models

Coronavirus disease 2019 (COVID-19) in humans has a wide range of presentations, ranging from asymptomatic or mild symptoms to severe illness. Suitable animal models mimicking varying degrees of clinical disease manifestations could expedite development of therapeutics and vaccines for COVID-19. Here we demonstrate that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection resulted in subclinical disease in rhesus macaques with mild pneumonia and clinical disease in Syrian hamsters with severe pneumonia. SARS-CoV-2 infection was confirmed by formalin-fixed, paraffin-embedded (FFPE) polymerase chain reaction (PCR), immunohistochemistry, or in situ hybridization. Replicating virus in the lungs was identified using in situ hybridization or virus plaque forming assays. Viral encephalitis, reported in some COVID-19 patients, was identified in one macaque and was confirmed with immunohistochemistry. There was no evidence of encephalitis in hamsters. Severity and distribution of lung inflammation were substantially more in hamsters compared with macaques and exhibited vascular changes and virus-induced cytopathic changes as seen in COVID-19 patients. Neither the hamster nor macaque models demonstrated evidence for multisystemic inflammatory syndrome (MIS). Data presented here demonstrate that macaques may be appropriate for mechanistic studies of mild asymptomatic COVID-19 pneumonia and COVID-19-associated encephalitis, whereas Syrian hamsters may be more suited to study severe COVID-19 pneumonia.

BNT162b vaccines protect rhesus macaques from SARS-CoV-2

A safe and effective vaccine against COVID-19 is urgently needed in quantities that are sufficient to immunize large populations. Here we report the preclinical development of two vaccine candidates (BNT162b1 and BNT162b2) that contain nucleoside-modified messenger RNA that encodes immunogens derived from the spike glycoprotein (S) of SARS-CoV-2, formulated in lipid nanoparticles. BNT162b1 encodes a soluble, secreted trimerized receptor-binding domain (known as the RBD-foldon). BNT162b2 encodes the full-length transmembrane S glycoprotein, locked in its prefusion conformation by the substitution of two residues with proline (S(K986P/V987P); hereafter, S(P2) (also known as P2 S)). The flexibly tethered RBDs of the RBD-foldon bind to human ACE2 with high avidity. Approximately 20% of the S(P2) trimers are in the two-RBD 'down', one-RBD 'up' state. In mice, one intramuscular dose of either candidate vaccine elicits a dose-dependent antibody response with high virus-entry inhibition titres and strong T-helper-1 CD4+ and IFNγ+CD8+ T cell responses. Prime-boost vaccination of rhesus macaques (Macaca mulatta) with the BNT162b candidates elicits SARS-CoV-2-neutralizing geometric mean titres that are 8.2-18.2× that of a panel of SARS-CoV-2-convalescent human sera. The vaccine candidates protect macaques against challenge with SARS-CoV-2; in particular, BNT162b2 protects the lower respiratory tract against the presence of viral RNA and shows no evidence of disease enhancement. Both candidates are being evaluated in phase I trials in Germany and the USA1-3, and BNT162b2 is being evaluated in an ongoing global phase II/III trial (NCT04380701 and NCT04368728).

The effect of SARS-CoV-2 D614G mutation on BNT162b2 vaccine-elicited neutralization

Initial COVID-19 vaccine candidates were based on the original sequence of SARS-CoV-2. However, the virus has since accumulated mutations, among which the spike D614G is dominant in circulating virus, raising questions about potential virus escape from vaccine-elicited immunity. Here, we report that the D614G mutation modestly reduced (1.7-2.4-fold) SARS-CoV-2 neutralization by BNT162b2 vaccine-elicited mouse, rhesus, and human sera, concurring with the 95% vaccine efficacy observed in clinical trial.

Evidence for an unknown agent antigenically related to the hepatitis E virus in dairy cows in the United States

Genotypes 3 and 4 hepatitis E virus (HEV) strains within the species Orthohepevirus A in the family Hepeviridae are zoonotic. Recently, a genotype 4 HEV was reportedly detected in fecal samples of cows, although independent confirmation is lacking. In this study, we first tested serum samples from 983 cows in different regions in the United States for the presence of immunoglobulin G (IgG) anti-HEV and found that 20.4% of cows were seropositive. The highest seroprevalence rate (68.4%) was from a herd in Georgia. In an attempt to genetically identify HEV in cattle, a prospective study was conducted in a known seropositive dairy herd by monitoring 10 newborn calves from birth to 6 months of age for evidence of HEV infection. At least 3 of the 10 calves seroconverted to IgG anti-HEV, and importantly the antibodies presented neutralized genotype 3 human HEV, thus, indicating the specificity of IgG anti-HEV in the cattle. However, our extensive attempts to identify HEV-related sequences in cattle using broad-spectrum reverse transcription-polymerase chain reaction assays and MiSeq deep-sequencing technology failed. The results suggest the existence of an agent antigenically related to HEV in cattle, although, contrary to published reports, we showed that the IgG recognizing HEV in cattle was not caused by HEV infection.

Virome of US bovine calf serum

Using viral metagenomics we analyzed four bovine serum pools assembled from 715 calves in the United States. Two parvoviruses, bovine parvovirus 2 (BPV2) and a previously uncharacterized parvovirus designated as bosavirus (BosaV), were detected in 3 and 4 pools respectively and their complete coding sequences generated. Based on NS1 protein identity, bosavirus qualifies as a member of a new species in the copiparvovirus genus. Also detected were low number of reads matching ungulate tetraparvovirus 2, bovine hepacivirus, and several papillomaviruses. This study further characterizes the diversity of viruses in calf serum with the potential to infect fetuses and through fetal bovine serum contaminate cell cultures.

Phylogenetic relationships of Staphylococcus aureus from bovine mastitis based on coagulase gene polymorphism

Coagulase gene restriction fragment length polymorphism (RFLP) patterns were analyzed to determine the phylogenetic relationship among isolates of Staphylococcus aureus from the Czech Republic (n = 27), France (n = 48), Korea (n = 115) and the United States (n = 278). A total of 468 isolates of S. aureus were subtyped into 41 coagulase genotypes. Cluster analysis placed the 41 types into nine clusters. Eighteen API Staph profiles were determined for 102 S. aureus isolates representing 1 to 4 isolates of each coagulase type. The results of the study suggest that based on coagulase gene RFLP analysis, several genetic variants of S. aureus are prevalent. Comparison of coagulase and API Staph profiles indicated that the two identification system were independent of each other.