Retrospective assessment of the antigenic similarity of egg-propagated and cell culture-propagated reference influenza viruses as compared with circulating viruses across influenza seasons 2002–2003 to 2017–2018

Producción CientíficaSuboptimal vaccine effectiveness against seasonal influenza is a significant public health concern, partly explained by antigenic differences between vaccine viruses and viruses circulating in the environment. Haemagglutinin mutations within vaccine viruses acquired during serial passage in eggs have been identified as a source of antigenic variation between vaccine and circulating viruses. This study retrospectively compared the antigenic similarity of circulating influenza isolates with egg- and cell-propagated reference viruses to assess any observable trends over a 16-year period. Using annual and interim reports published by the Worldwide Influenza Centre, London, for the 2002–2003 to 2017–2018 influenza seasons, we assessed the proportions of circulating viruses which showed antigenic similarity to reference viruses by season. Egg-propagated reference viruses were well matched against circulating viruses for A/H1N1 and B/Yamagata. However, A/H3N2 and B/Victoria cell-propagated reference viruses appeared to be more antigenically similar to circulating A/H3N2 and B/Victoria viruses than egg-propagated reference viruses. These data support the possibility that A/H3N2 and B/Victoria viruses are relatively more prone to egg-adaptive mutation. Cell-propagated A/H3N2 and B/Victoria reference viruses were more antigenically similar to circulating A/H3N2 and B/Victoria viruses over a 16-year period than were egg-propagated reference viruses

Identification of a Human Monoclonal Antibody to Replace Equine Diphtheria Anti-toxin for the Treatment of Diphtheria

Diphtheria anti-toxin (DAT) has been used to treat Corynebacterium diphtheriae infection for over one hundred years. While the global incidence of diphtheria has declined in the 20th century, the disease remains endemic in many parts of the world and significant outbreaks still occur. Diphtheria anti-toxin is an equine polyclonal antibody with considerable side effects that is in critically short supply globally. A safer, more readily available alternative to DAT would be desirable. In the current study, we cloned human monoclonal antibodies (HuMabs) directly from antibody secreting cells of human volunteers immunized with Td vaccine. We isolated a diverse panel of HuMabs that recognized diphtheria toxoid and recombinant protein fragments of diphtheria toxin. Forty-one unique HuMabs were expressed in 293T cells and tested for neutralization of diphtheria toxin in in vitro cytotoxicity assays. The lead candidate HuMab, 315C4 potently neutralized diphtheria toxin with an EC50 of 0.65 ng/mL. Additionally, 25 μg of 315C4 completely protected guinea pigs in an in vivo lethality model. In comparison, 1.6 IU of DAT was necessary for full protection resulting in an estimated relative potency of 64 IU/mg for 315C4. We further established that our lead candidate HuMab binds to the receptor binding domain of diphtheria toxin and blocks the toxin from binding to the putative receptor, heparin binding-epidermal growth factor like growth factor. The discovery of a specific and potent neutralizing antibody against diphtheria toxin holds promise as a potential human therapeutic and is being developed for human use

Human Monoclonal Antibody HCV1 Effectively Prevents and Treats HCV Infection in Chimpanzees

Hepatitis C virus (HCV) infection is a leading cause of liver transplantation and there is an urgent need to develop therapies to reduce rates of HCV infection of transplanted livers. Approved therapeutics for HCV are poorly tolerated and are of limited efficacy in this patient population. Human monoclonal antibody HCV1 recognizes a highly-conserved linear epitope of the HCV E2 envelope glycoprotein (amino acids 412-423) and neutralizes a broad range of HCV genotypes. In a chimpanzee model, a single dose of 250 mg/kg HCV1 delivered 30 minutes prior to infusion with genotype 1a H77 HCV provided complete protection from HCV infection, whereas a dose of 50 mg/kg HCV1 did not protect. In addition, an acutely-infected chimpanzee given 250 mg/kg HCV1 42 days following exposure to virus had a rapid reduction in viral load to below the limit of detection before rebounding 14 days later. The emergent virus displayed an E2 mutation (N415K/D) conferring resistance to HCV1 neutralization. Finally, three chronically HCV-infected chimpanzees were treated with a single dose of 40 mg/kg HCV1 and viral load was reduced to below the limit of detection for 21 days in one chimpanzee with rebounding virus displaying a resistance mutation (N417S). The other two chimpanzees had 0.5-1.0 log(10) reductions in viral load without evidence of viral resistance to HCV1. In vitro testing using HCV pseudovirus (HCVpp) demonstrated that the sera from the poorly-responding chimpanzees inhibited the ability of HCV1 to neutralize HCVpp. Measurement of antibody responses in the chronically-infected chimpanzees implicated endogenous antibody to E2 and interference with HCV1 neutralization although other factors may also be responsible. These data suggest that human monoclonal antibody HCV1 may be an effective therapeutic for the prevention of graft infection in HCV-infected patients undergoing liver transplantation

Risk of COVID-19 after natural infection or vaccination

BACKGROUND: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. METHODS: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 \u3e7-15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. FINDINGS: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05-0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01-0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. INTERPRETATION: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. FUNDING: National Institutes of Health

Quantification of In Vitro and In Vivo Cryptosporidium parvum Infection by Using Real-Time PCR

Established methods for quantifying experimental Cryptosporidium infection are highly variable and subjective. We describe a new technique using quantitative real-time PCR (qPCR) that can be used to measure in vitro and in vivo laboratory infections with Cryptosporidium. We show for the first time that qPCR permits absolute quantification of the parasite while simultaneously controlling for the amount of host tissue and correlates significantly with established methods of quantification in in vitro and in vivo laboratory models of infection

An Early Intestinal Mucosal Source of Gamma Interferon Is Associated with Resistance to and Control of Cryptosporidium parvum Infection in Mice

Resistance to and control of Cryptosporidium parvum infection in mice in the absence of adaptive immunity appears to be gamma interferon (IFN-γ) dependent. Using an IFN-γ-neutralizing antibody in a murine model, we demonstrated increased susceptibility to infection within 24 h. We correlated this early resistance and control with increased mucosal expression of IFN-γ and demonstrate that CD8(+) T-cell receptor αβ intestinal intraepithelial lymphocytes express and secrete this cytokine shortly after infection. The rapid kinetics of IFN-γ expression and secretion by naive CD8(+) T cells in response to a protozoan pathogen have not previously been demonstrated

A preliminary report of a randomized controlled phase 2 trial of the safety and immunogenicity of mRNA-1273 SARS-CoV-2 vaccine

BACKGROUND: Vaccines are urgently needed to prevent the global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We assessed the safety and immunogenicity of vaccine candidate mRNA-1273, encoding the prefusion-stabilized spike protein of SARS-CoV-2.METHODS: This phase 2, randomized, observer-blind, placebo-controlled trial was conducted at 8 sites in the USA, in healthy adults aged ≥18 years with no known history or risk of SARS-CoV-2 infection, and had not previously received an investigational CoV vaccine or treatment. Participants were stratified into two age cohorts (≥18-<55 and ≥55) and were randomly assigned (1:1:1) to either 50 or 100 µg of mRNA-1273, or placebo administered as two intramuscular injections 28 days apart. The primary outcomes were safety, reactogenicity, and immunogenicity assessed by anti-SARS-CoV-2-spike binding antibody level (bAb). Secondary outcome was immunogenicity assessed by SARS-CoV-2 neutralizing antibody (nAb) response.RESULTS: Between 29 May and 8 July 2020, 600 participants were randomized, 300 per age cohort. The most common solicited adverse reactions were pain at injection site, headache, and fatigue following each vaccination in both age cohorts. One serious adverse event deemed unrelated by the site investigator occurred 33 days post-vaccination one. mRNA-1273 induced bAb and nAb by 28 days post-vaccination one that were higher at the 100 µg dose relative to the 50 µg dose; this difference was less apparent post-vaccination two. Binding antibodies and nAb increased substantially by 14 days following the second vaccination (day 43) to levels exceeding those of convalescent sera and remained elevated through day 57.CONCLUSIONS: Vaccination with mRNA-1273 resulted in significant immune responses to SARS-CoV-2 in participants 18 years and older, with an acceptable safety profile, confirming the safety and immunogenicity of 50 and 100 µg mRNA-1273 given as a 2 dose-regimen

Analysis of Sequence Diversity at the Highly Polymorphic Cpgp40/15 Locus among Cryptosporidium Isolates from Human Immunodeficiency Virus-Infected Children in South Africa

Cryptosporidium sp. is a significant cause of diarrheal disease, particularly in human immunodeficiency virus (HIV)-infected patients in developing countries. We recently cloned and sequenced several alleles of the highly polymorphic single-copy Cryptosporidium parvum gene Cpgp40/15. This gene encodes a precursor protein that is proteolytically cleaved to yield mature cell surface glycoproteins gp40 and gp15, which are implicated in zoite attachment to and invasion of enterocytes. The most-striking feature of the Cpgp40/15 alleles and proteins is their unprecedented degree of sequence polymorphism, which is far greater than that observed for any other gene or protein studied in C. parvum to date. In this study we analyzed nucleic acid and amino acid sequence polymorphism at the Cpgp40/15 locus of 20 C. parvum isolates from HIV-infected South African children. Fifteen isolates exhibited one of four previously identified genotype I alleles at the Cpgp40/15 locus (Ia, Ib, Ic, and Id), while five displayed a novel set of polymorphisms that defined a new Cpgp40/15 genotype I allele, designated genotype Ie. Surprisingly, only 15 of these isolates exhibited concordant type I alleles at the thrombospondin-related adhesive protein of Cryptosporidium and Cryptosporidium oocyst wall protein loci, while five isolates (all of which displayed Cpgp40/15 genotype Ic alleles) displayed genotype II alleles at these loci. Furthermore, the last five isolates also manifested chimeric genotype Ic/Ib or Ic/II alleles at the Cpgp40/15 locus, raising the possibility of sexual recombination within and between prototypal parasite genotypes. Lastly, children infected with isolates having genotype Ic alleles were significantly older than those infected with isolates displaying other genotype I alleles

Serum anti-toxin B antibody correlates with protection from recurrent Clostridium difficile infection (CDI)

BACKGROUND: Previous studies have demonstrated a correlation between Clostridium difficile anti-toxin A serum antibodies and protection against symptomatic disease and recurrence. METHODS: A neutralizing monoclonal antibody to C. difficile toxin A (CDA1) developed by MBL and Medarex, Inc. was studied in a phase II, randomized, double-blind, placebo-controlled trial in patients receiving standard of care treatment for C. difficile infection (CDI). Twenty-nine subjects received a single intravenous infusion of 10mg/kg CDA1 and 17 subjects received placebo and were evaluated for recurrence of CDI during the 56-day study period. Serum antibodies against C. difficile toxin A and B were measured by ELISA and cytotoxicity assay at various time points before and after infusion. FINDINGS: CDI recurrence occurred in 5 of 29 (17%) in the CDA1 group and 3 of 17 (18%) (p=NS) in the placebo group with a trend toward delay in time to recurrence in the group treated with CDA1. The geometric mean concentration of antibody to an epitope of the receptor-binding domain of toxin B (0.300 and 1.20microg/ml, respectively; p=0.02) and geometric mean titer of neutralizing B antibody (8.00 and 100, respectively; p=0.02) at study day 28 were lower for those subjects with recurrence compared to those who did not recur. In addition, a significantly greater proportion of subjects who recurred were infected with the epidemic BI/NAP1/027 strain compared with those that did not recur (88% vs. 22%; p=0.002). Finally, in a multiple logistic regression analysis neutralizing anti-toxin B at day 14 (p\u3c0.001), anti-toxin A at day 28 (p\u3c0.001) and infection with the BI/NAP1/027 strain at enrollment (p=0.002) were all predictive of CDI recurrence. INTERPRETATION: In this prospective study, lower concentrations of neutralizing anti-toxin B and anti-toxin A antibody and infection with the BI/NAP1/027 strain of C. difficile were significantly associated with recurrence of CDI