An emm-type specific qPCR to track bacterial load during experimental human Streptococcus pyogenes pharyngitis

Background Streptococcus pyogenes causes a profound global burden of morbidity and mortality across its diverse clinical spectrum. To support a new controlled human infection (‘challenge’) model seeking to accelerate S. pyogenes vaccine development, we aimed to develop an accurate and reliable molecular method for quantifying bacterial load from pharyngeal swabs collected during experimental human pharyngitis. Methods Combined sequential RNA + DNA extraction from throat swabs was compared to traditional separate RNA-only and DNA-only extractions. An emm-type specific qPCR was developed to detect the emm75 challenge strain. Results from the qPCR were compared to culture, using throat swab samples collected in a human challenge study. Results The qPCR was 100% specific for the emm75 challenge strain when tested against a panel of S. pyogenes emm-types and other respiratory pathogens. Combined RNA + DNA extraction had similar yield to traditional separate extractions. The combined extraction method and emm75 qPCR had 98.8% sensitivity compared to culture for throat swabs collected from challenge study participants. Conclusions We have developed a reliable molecular method for measuring S. pyogenes bacterial load from throat swabs collected in a controlled human infection model of S. pyogenes pharyngitis. Trial registration NCT03361163 on 4th December 2017.

Cell culture model vaccine trial against sheep pox

The purpose of this study was to establish and evaluate the cell culture model vaccine produced in our situation through inoculation of Russian VNIIZJ sheep pox vaccine strain to Vero cells and challenge of target animals. The TCID50/ml of the model vaccine strain was 103.1 and the ID50/ml of the challenge strain Stravropolskii was 103.15respectively. The virulence of the model vaccine was evaluated in laboratory mice and it was safe. Total 75% of the vaccinated sheep were survived at 6-months post injecttion, while 50% of the vaccinated sheep were survived at 9-12 months’ post injection. It shows this model vaccine protected at certain level against sheep pox, and further studies are required to improve it. Хонины цэцэг өвчний эсийн өсгөвөрт вакцины загвар бэлтгэн туршсан дүн Бидний судалгааны ажлын зорилго өөрийн орны нөхцөлд хонины цэцэг өвчний эсийн өсгөвөрт вакцины загвар гарган авах байсан бөгөөд энэ ажлын хүрээнд ОХУ-ын ВНИИЗЖ хонины цэцэг өвчний омгийг Vero эсийн өсгөвөрт өсгөвөрлөн хонинд амь сорил тавих замаар шалгасан болно. Вакцины загварт хэрэглэсэн вирусын эс эмгэгшүүлэх тун 103.1 TCID50/мл харин амь сорилд ашиглах өндөр хоруу чанартай хонины цэцгийн Ставропольский амьд омгийн өвчлүүлэх тун 103.15 ӨТ50/мл байлаа. Вакцины загварын хоруу чанарыг лабораторийн хулгана ашиглан шалган үзэхэд аюулгүй байв. Вакцины загварын идэвхит чанарыг нийт 4 хонинд амь сорил тавьж шалган үзэхэд вакцины загвар таригдсанаас хойш 6 сарын дараа 75% хамгаалж, харин 9 болон 12 сар дээрээ 50% хамгаалж байгаа нь энэ вакцины загвар хонины цэцэг өвчнөөс тодорхой хэмжээнд хамгаалах идэвхитэй байгааг харуулж байна. Цаашид энэ вакцины загварыг илүү боловсруулах шаардлагатай байна. Түлхүүр үг: Vero эс, амьд вирус, вакцин, хонь

Serum levels of anti-PspA and anti-PspC IgG decrease with age and do not correlate with susceptibility to experimental human pneumococcal colonization

Older adults are at increased risk of pneumococcal disease. This work aims to evaluate whether there is any decrease in serum IgG against variants of the antigens Pneumococcal surface protein A (PspA) and Pneumococcal surface protein C (PspC) in healthy adults with increasing age. Levels of IgG against PspA and PspC variants were determined by ELISA in serum samples comparing volunteers 18–30 years of age with volunteers who were 50–70+ before and after an experimental pneumococcal colonization challenge. The serotype 6B strain used in the challenge belongs to a minor group of pneumococcal isolates expressing two PspC variants. There was a decrease in levels of IgG with increasing age for the most common PspA variants and for all PspC variants analyzed. No correlation was found between basal levels of IgG against these antigens and protection against colonization. There was an increase in levels of IgG against PspA variants that are more cross-reactive with the variant expressed by the challenge strain post challenge in younger individuals who became colonized. Since the challenge strain used in our study expresses two different PspC variants, an increase in serum IgG against all PspC variants tested was observed in younger individuals who became colonized. For some of the antigen variants tested, a decrease in serum IgG was observed in young volunteers who were challenged but did not become colonized. Serum IgG antibodies against PspA and PspC variants thus decrease with age in healthy adults, but there is no correlation between levels of IgG against these antigens and protection against human experimental colonization. Though no correlation between naturally induced serum IgG antibodies against PspA and PspC and protection against colonization was observed, these results do not rule out the protective potential of these antigens as vaccines against pneumococcal infections.

In Vivo Genome and Methylome Adaptation of cag-Negative Helicobacter pylori during Experimental Human Infection

ABSTRACT Multiple studies have demonstrated rapid bacterial genome evolution during chronic infection with Helicobacter pylori. In contrast, little was known about genetic changes during the first stages of infection, when selective pressure is likely to be highest. Using single-molecule, real-time (SMRT) and Illumina sequencing technologies, we analyzed genome and methylome evolution during the first 10 weeks of infection by comparing the cag pathogenicity island (cagPAI)-negative H. pylori challenge strain BCS 100 with pairs of H. pylori reisolates from gastric antrum and corpus biopsy specimens of 10 human volunteers who had been infected with this strain as part of a vaccine trial. Most genetic changes detected in the reisolates affected genes with a surface-related role or a predicted function in peptide uptake. Apart from phenotypic changes of the bacterial envelope, a duplication of the catalase gene was observed in one reisolate, which resulted in higher catalase activity and improved survival under oxidative stress conditions. The methylomes also varied in some of the reisolates, mostly by activity switching of phase-variable methyltransferase (MTase) genes. The observed in vivo mutation spectrum was remarkable for a very high proportion of nonsynonymous mutations. Although the data showed substantial within-strain genome diversity in the challenge strain, most antrum and corpus reisolates from the same volunteers were highly similar to each other, indicating that the challenge infection represents a major selective bottleneck shaping the transmitted population. Our findings suggest rapid in vivo selection of H. pylori during early-phase infection providing adaptation to different individuals by common mechanisms of genetic and epigenetic alterations. IMPORTANCE Exceptional genetic diversity and variability are hallmarks of Helicobacter pylori, but the biological role of this plasticity remains incompletely understood. Here, we had the rare opportunity to investigate the molecular evolution during the first weeks of H. pylori infection by comparing the genomes and epigenomes of H. pylori strain BCS 100 used to challenge human volunteers in a vaccine trial with those of bacteria reisolated from the volunteers 10 weeks after the challenge. The data provide molecular insights into the process of establishment of this highly versatile pathogen in 10 different human individual hosts, showing, for example, selection for changes in host-interaction molecules as well as changes in epigenetic methylation patterns. The data provide important clues to the early adaptation of H. pylori to new host niches after transmission, which we believe is vital to understand its success as a chronic pathogen and develop more efficient treatments and vaccines.

Successes and Failures of the Live-attenuated Influenza Vaccine: Can We Do Better?

Background The effectiveness of the live-attenuated influenza vaccine (LAIV) can vary widely, ranging from 0% to 50%. The reasons for these discrepancies remain largely unclear. Methods We use mathematical models to explore how the efficacy of LAIV is affected by the degree of mismatch with the currently circulating influenza strain and interference with pre-existing immunity. The models incorporate 3 key antigenic distances: the distances between the vaccine strain, pre-existing immunity, and the challenge strain. Results Our models show that an LAIV that is matched with the currently circulating strain is likely to have only modest efficacy. Our results suggest that the efficacy of the vaccine would be increased (optimized) if, rather than being matched to the circulating strain, it is antigenically slightly further from pre-existing immunity than the circulating strain. The models also suggest 2 regimes in which LAIV that is matched to circulating strains may be protective: in children before they have built immunity to circulating strains and in response to novel strains (such as antigenic shifts) which are at substantial antigenic distance from previously circulating strains. We provide an explanation for the variation in vaccine effectiveness between studies and countries of vaccine effectiveness observed during the 2014–2015 influenza season. Conclusions LAIV is offered to children across the world; however, its effectiveness significantly varies between studies. Here, we propose a mechanistic explanation to understand these differences. We further propose a way to select the LAIV strain that would have a higher chance of being protective.

Q&A on the Paper of Kurukulasuriya et al. (2017) on IBD Vaccine Efficacy Against a Canadian Variant IBDV Strain in Broiler Chickens

Kurukulasuriya, et al. (2017) are reporting the efficacy of two IBD vaccines against an early (6 days post-hatch) challenge with a variant Canadian IBDV strain in broilers. A modified live vaccine(UNIVAX BD) administered by SQ route at 1 dayof-age delayed infection whereas an HVT-IBD vector vaccine (VAXXITEK HVT+IBD) administered in ovodid not protect. Furthermore, the authors suggested that the HVT-IBD vector induced immunosuppression responsible for an earlier IBDV challenge strain replication in the bursa. The data presented in the paper showed no evidence of VAXXITEK HVT+IBD vaccine take since the mean IBD ELISA antibody titer at D35 in the vaccinated/non-challenged group was not significantly different from that of the non-vaccinated group. It wasmuch lower than the expected one based on previous studies performed in the same conditions : in ovo vaccination of broilers [1,2]. Since there is no evidence of vaccine take, the other potential effects (immunosuppression and earlier IBDV replication in the bursa) observed in that group cannot be attributed to the vaccine. Since its launch in 2006 in Brazil, VAXXITEK HVT+IBD has been licensed in more than 75 countries and more than 80 billion birds have been vaccinated. VAXXITEK HVT+IBD is protecting against a wide variety of IBDV strains including the classical, the very virulent and different variant strains. To our knowledge, noabsence of efficacy nor bursa depletions have been so far officially reported as long as the vaccine has been administered properlyto healthy embryonated eggs or to healthy one-day-old chicks.

Complete Genome Sequencing of a Classical Swine Fever Virus Strain Endemic in Vietnam

ABSTRACT A Vietnamese strain of classical swine fever virus, VN91, was isolated in Hung Yen in 1991. While VN91 has been used as a challenge strain in efficacy tests of vaccines, its genetic background has never been described. Here, we report the genome sequence of the strain circulating in Vietnam.

Protective effects of indigenous Escherichia coli against a pathogenic E. coli challenge strain in pigs

To investigate the inhibitory effect of indigenous enterobacteria on pathogenic Escherichia coli, a challenge trial with postweaning pigs was conducted. A pathogenic E. coli strain was administered to all animals and their health was closely monitored thereafter. Faecal samples were taken from three healthy and three diarrhoeic animals. Samples were cultivated on MacConkey agar and isolates were subcultured. A soft agar overlay assay was used to determine the inhibitory activity of the isolates. A total of 1,173 enterobacterial isolates were screened for their ability to inhibit the E. coli challenge strain. Colony forming units of enterobacteria on MacConkey agar were not different between healthy and diarrhoeic animals in the original samples. Furthermore, numbers of isolates per animal were also not significantly different between healthy (482 isolates) and diarrhoeic animals (691 isolates). A total of 43 isolates (3.7%) with inhibitory activity against the pathogenic E. coli challenge strain were detected. All inhibitory isolates were identified as E. coli via MALDI-TOF. The isolates belonged to the phylotypes A, C and E. Many isolates (67.4%) were commensal E. coli without relevant porcine pathogenic factors, but toxin- and fimbrial genes (stx2e, fae, estIb, elt1a, fas, fan) were detected in 14 inhibitory isolates. Healthy animals showed significantly (P=0.003) more inhibitory isolates (36 of 482 isolates; 7.5%) than diseased animals (7 of 691 isolates; 1.0%). There were no significant correlations regarding phylotype or pathogenic factors between healthy and diseased animals. This study has shown that a small proportion of indigenous E. coli is able to inhibit in vitro growth of a pathogenic E. coli strain in pigs. Furthermore, healthy animals possess significantly more inhibitory E. coli strains than diarrhoeic animals. The inhibition of pathogenic E. coli by specific indigenous E. coli strains may be an underlying principle for the containment of pathogenic E. coli in pigs.