Development of a Kinetic ELISA and Reactive B Cell Frequency Assay to Detect Respiratory Syncytial Virus Pre-Fusion F Protein-Specific Immune Responses in Infants

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of respiratory disease in infants, making vaccination an attractive preventive strategy. Due to earlier reports of vaccine-enhanced disease in RSV-naive children, assessing prior RSV infection is critical for determining eligibility for future infant vaccine trials. However, this is complicated by the presence of maternally transferred maternal antibodies. We sought to develop assays that measure immune responses to RSV pre-fusion (F) protein that discriminates between maternal and infant responses.

METHODS

We measured RSV-specific responses in two groups of children <3 years of age; those with laboratory-confirmed RSV (RSV-infected) and those enrolled prior to their first RSV season (RSV-uninfected). Serial blood samples were obtained and recent infections with RSV and other respiratory viruses were assessed during follow-up. An RSV pre-F-specific kinetic enzyme-linked immunosorbent assay (kELISA) and an F-specific reactive B cell frequency (RBF) assay were developed.

RESULTS

One hundred two young children were enrolled between July 2015 and April 2017; 74 were in the RSV-uninfected group and 28 were in the RSV-infected group. Participants were asked to provide sequential blood samples over time, but only 53 participants in the RSV-uninfected group and 22 participants in the RSV-infected groups provided multiple samples. In the RSV-infected group, most had positive kELISA and RBF during the study. In the RSV-uninfected group, two patterns emerged: declining kELISA values without reactive B cells, due to maternal transplacental antibody transfer, and persistently positive kELISA with reactive B cells, due to asymptomatic undiagnosed RSV infection.

CONCLUSIONS

A kELISA targeting RSV pre-F epitopes and an RBF assay targeting RSV F-specific B cells generally allow discrimination between maternally and infant-derived antibodies.

Pan-ebolavirus protective therapy by two multifunctional human antibodies

Ebolaviruses cause a severe and often fatal illness with the potential for global spread. Monoclonal antibody-based treatments that have become available recently have a narrow therapeutic spectrum and are ineffective against ebolaviruses other than Ebola virus (EBOV), including medically important Bundibugyo (BDBV) and Sudan (SUDV) viruses. Here, we report the development of a therapeutic cocktail comprising two broadly neutralizing human antibodies, rEBOV-515 and rEBOV-442, that recognize non-overlapping sites on the ebolavirus glycoprotein (GP). Antibodies in the cocktail exhibited synergistic neutralizing activity, resisted viral escape, and possessed differing requirements for their Fc-regions for optimal in vivo activities. The cocktail protected non-human primates from ebolavirus disease caused by EBOV, BDBV, or SUDV with high therapeutic effectiveness. High-resolution structures of the cocktail antibodies in complex with GP revealed the molecular determinants for neutralization breadth and potency. This study provides advanced preclinical data to support clinical development of this cocktail for pan-ebolavirus therapy.

Cooperativity mediated by rationally selected combinations of human monoclonal antibodies targeting the henipavirus receptor binding protein

Hendra virus and Nipah virus (NiV), members of the Henipavirus (HNV) genus, are zoonotic paramyxoviruses known to cause severe disease across six mammalian orders, including humans. We isolated a panel of human monoclonal antibodies (mAbs) from the B cells of an individual with prior exposure to equine Hendra virus (HeV) vaccine, targeting distinct antigenic sites. The most potent class of cross-reactive antibodies achieves neutralization by blocking viral attachment to the host cell receptors ephrin-B2 and ephrin-B3, with a second class being enhanced by receptor binding. mAbs from both classes display synergistic activity in vitro. In a stringent hamster model of NiV Bangladesh (NiV_B) infection, antibodies from both classes reduce morbidity and mortality and achieve synergistic protection in combination. These candidate mAbs might be suitable for use in a cocktail therapeutic approach to achieve synergistic potency and reduce the risk of virus escape.

Doyle et al. describe two human monoclonal antibodies that target the henipavirus receptor-binding protein, HENV-103 and HENV-117, that display highly potent activity in vitro and enhanced therapeutic efficacy in vivo when delivered as a cocktail.

Proteo-Genomic Analysis Identifies Two Major Sites of Vulnerability on Ebolavirus Glycoprotein for Neutralizing Antibodies in Convalescent Human Plasma

Three clinically relevant ebolaviruses - Ebola (EBOV), Bundibugyo (BDBV), and Sudan (SUDV) viruses, are responsible for severe disease and occasional deadly outbreaks in Africa. The largest Ebola virus disease (EVD) epidemic to date in 2013-2016 in West Africa highlighted the urgent need for countermeasures, leading to the development and FDA approval of the Ebola virus vaccine rVSV-ZEBOV (Ervebo®) in 2020 and two monoclonal antibody (mAb)-based therapeutics (Inmazeb® [atoltivimab, maftivimab, and odesivimab-ebgn] and Ebanga® (ansuvimab-zykl) in 2020. The humoral response plays an indispensable role in ebolavirus immunity, based on studies of mAbs isolated from the antibody genes in peripheral blood circulating ebolavirus-specific human memory B cells. However, antibodies in the body are not secreted by circulating memory B cells in the blood but rather principally by plasma cells in the bone marrow. Little is known about the protective polyclonal antibody responses in convalescent plasma. Here we exploited both single-cell antibody gene sequencing and proteomic sequencing approaches to assess the composition of the ebolavirus glycoprotein (GP)-reactive antibody repertoire in the plasma of an EVD survivor. We first identified 1,512 GP-specific mAb variable gene sequences from single cells in the memory B cell compartment. Using mass spectrometric analysis of the corresponding GP-specific plasma IgG, we found that only a portion of the large B cell antibody repertoire was represented in the plasma. Molecular and functional analysis of proteomics-identified mAbs revealed recognition of epitopes in three major antigenic sites - the GP head domain, the glycan cap, and the base region, with a high prevalence of neutralizing and protective mAb specificities that targeted the base and glycan cap regions on the GP. Polyclonal plasma antibodies from the survivor reacted broadly to EBOV, BDBV, and SUDV GP, while reactivity of the potently neutralizing mAbs we identified was limited mostly to the homologous EBOV GP. Together these results reveal a restricted diversity of neutralizing humoral response in which mAbs targeting two antigenic sites on GP - glycan cap and base - play a principal role in plasma-antibody-mediated protective immunity against EVD.

Neutralizing and protective human monoclonal antibodies recognizing the N-terminal domain of the SARS-CoV-2 spike protein

Most human monoclonal antibodies (mAbs) neutralizing SARS-CoV-2 recognize the spike (S) protein receptor-binding domain and block virus interactions with the cellular receptor angiotensin-converting enzyme 2. We describe a panel of human mAbs binding to diverse epitopes on the N-terminal domain (NTD) of S protein from SARS-CoV-2 convalescent donors and found a minority of these possessed neutralizing activity. Two mAbs (COV2-2676 and COV2-2489) inhibited infection of authentic SARS-CoV-2 and recombinant VSV/SARS-CoV-2 viruses. We mapped their binding epitopes by alanine-scanning mutagenesis and selection of functional SARS-CoV-2 S neutralization escape variants. Mechanistic studies showed that these antibodies neutralize in part by inhibiting a post-attachment step in the infection cycle. COV2-2676 and COV2-2489 offered protection either as prophylaxis or therapy, and Fc effector functions were required for optimal protection. Thus, natural infection induces a subset of potent NTD-specific mAbs that leverage neutralizing and Fc-mediated activities to protect against SARS-CoV-2 infection using multiple functional attributes.

SARS-CoV-2 Antibody Positivity and Prevalence in an Outpatient Medical Setting in Las Vegas, NV

Background

SARS-CoV-2 antibody testing shows the prevalence of COVID-19 disease in different communities and has epidemiological significance.

Methods

SARS-CoV-2 IgM and IgG were tested in 319 patients, staff and visitors of a primary care clinic in Las Vegas, NV on a continuous as-requested basis.

Results

Prevalence of SARS-CoV-2 antibodies was 3.76% in a primary care office in Las Vegas, NV. Positivity of IgM was 0.31% and IgG 3.44%. The most common symptoms reported amongst those who tested positive were cough, shortness of breath and loss of smell and taste. The most common comorbidities included hypertension, chronic lung disease, seasonal allergies, and type 2 diabetes mellitus, in that order.

Conclusion

Prevalence was 2.3% in Washoe County, NV in June 2020 and 3.76% in Clark County, NV in April-June 2020. This has important implications for heavily populated urban areas.

Analysis of a Therapeutic Antibody Cocktail Reveals Determinants for Cooperative and Broad Ebolavirus Neutralization

Structural principles underlying the composition of protective antiviral monoclonal antibody (mAb) cocktails are poorly defined. Here, we exploited antibody cooperativity to develop a therapeutic mAb cocktail against Ebola virus. We systematically analyzed the antibody repertoire in human survivors and identified a pair of potently neutralizing mAbs that cooperatively bound to the ebolavirus glycoprotein (GP). High-resolution structures revealed that in a two-antibody cocktail, molecular mimicry was a major feature of mAb-GP interactions. Broadly neutralizing mAb rEBOV-520 targeted a conserved epitope on the GP base region. mAb rEBOV-548 bound to a glycan cap epitope, possessed neutralizing and Fc-mediated effector function activities, and potentiated neutralization by rEBOV-520. Remodeling of the glycan cap structures by the cocktail enabled enhanced GP binding and virus neutralization. The cocktail demonstrated resistance to virus escape and protected non-human primates (NHPs) against Ebola virus disease. These data illuminate structural principles of antibody cooperativity with implications for development of antiviral immunotherapeutics.

Outbreaks of highly pathogenic avian influenza in zoo birds caused by HA clade 2.3.4.4 H5N6 subtype viruses in Japan in winter 2016

In late 2016, two zoos, one in northern Japan and the other in central Japan, experienced highly pathogenic avian influenza (HPAI) outbreaks, in which multiple zoo birds were infected with H5N6 subtype HPAI virus (HPAIV). Here, we report an overview of these HPAI outbreaks. HPAIV infections were confirmed by virus isolation in three black swans (Cygnus atratus) and three snowy owls (Bubo scandiacus) kept in the Omoriyama Zoo hospital. At Higashiyama Zoo and Botanical Gardens, following the death of a black swan at a zoo pond, nine waterfowl, including two black swans, four cackling geese (Branta hutchinsii leucopareia), two mallards (Anas platyrhynchos), and a wigeon (Anas penelope), died after HPAIV infection in isolation facilities. Based on the presence of H5-specific antibodies in their sera, two surviving black swans and a surviving mallard at Higashiyama Zoo appeared to have HPAIV infection, although the virus was not isolated. The detectable levels of antibodies (≥10 HI) were maintained for at least 5-9 months, as determined by haemagglutinin inhibition test. Isolation of two H5N6 subtype HPAIVs from an open-air pond where affected zoo birds were previously housed at Higashiyama Zoo strongly indicates that wild waterfowl associated with aquatic environments brought the virus to the zoo. The phylogenetic relationships of the 18 isolates indicated direct viral transmission among birds within each zoo. In both zoos, containment of suspected birds in isolation facilities might have allowed the virus spread among birds inside the facility. However, maintaining containment measures and strict sanitation procedures could facilitate successful physical containment and clearance of HPAIV in both zoos.

Multifunctional Pan-ebolavirus Antibody Recognizes a Site of Broad Vulnerability on the Ebolavirus Glycoprotein

Ebolaviruses cause severe disease in humans, and identification of monoclonal antibodies (mAbs) that are effective against multiple ebolaviruses are important for therapeutics development. Here we describe a distinct class of broadly neutralizing human mAbs with protective capacity against three ebolaviruses infectious for humans: Ebola (EBOV), Sudan (SUDV), and Bundibugyo (BDBV) viruses. We isolated mAbs from human survivors of ebolavirus disease and identified a potent mAb, EBOV-520, which bound to an epitope in the glycoprotein (GP) base region. EBOV-520 efficiently neutralized EBOV, BDBV, and SUDV and also showed protective capacity in relevant animal models of these infections. EBOV-520 mediated protection principally by direct virus neutralization and exhibited multifunctional properties. This study identified a potent naturally occurring mAb and defined key features of the human antibody response that may contribute to broad protection. This multifunctional mAb and related clones are promising candidates for development as broadly protective pan-ebolavirus therapeutic molecules.

Serologic markers of viral infection and risk of non-Hodgkin lymphoma: A pooled study of three prospective cohorts in China and Singapore

Incidence rates of non-Hodgkin lymphoma (NHL) and distributions of certain viruses differ between East Asian and Western populations. There are limited data on associations between serologic markers of multiple viral infections in pre-diagnostic blood and NHL risk in East Asians. We conducted a nested case-control study of 214 NHL cases and 214 matched controls from three population-based prospective cohorts in Shanghai and Singapore. Antibodies against antigens from herpesviruses, Hepatitis B (HBV) and C (HCV) virus and polyomaviruses were measured in plasma or serum using fluorescent bead-based multiplex assays. Conditional logistic regression was used to evaluate associations between antibody levels and NHL risk. An increased risk of NHL was observed for higher compared to lower EA-D (Odds Ratio (OR) = 2.04, 95% Confidence Interval (CI) = 1.10-3.81; ptrend  = 0.005) and ZEBRA (OR = 2.17, 95% CI = 0.96-4.89; ptrend  = 0.008) Epstein-Barr Virus (EBV) antibodies, as well as for antibody seropositivity against the IE1A human herpesvirus-6 (HHV-6) antigen (OR = 1.85, 95% CI = 1.04-3.29). An increased NHL risk was also observed for higher compared to lower antibodies against the HBV-HBc and HBe antigens. An increased risk of NHL in relation to EBV and HBV infection in East Asians is consistent with findings in several studies of Western populations, suggesting similar viral risk factors for NHL in these diverse populations with distinct patterns of NHL. The association between HHV-6 antibodies and NHL has not previously been reported in a prospective study in this population and will require replication.

Evaluating the performance of the focus HerpeSelect® HSV-2 IgG in veterans with chronic hepatitis C infection

Epidemiologic links between chronic hepatitis C and herpes simplex type-2 infection have been suggested; however, type-specific tests for HSV-2 infection have not been validated in patients with chronic hepatitis C infection. The Focus HerpeSelect(®) HSV-2 IgG (Cypress, California) assay and the Biokit HSV-2 rapid assay (Biokit USA, Lexington, MA) were performed on serum samples obtained from 84 veterans with chronic hepatitis C who demonstrated a previously positive HSV-2 serologic test in their medical records. Using the Biokit HSV-2 as the comparator assay, the positive predictive value, and specificity for the HerpeSelect(®) HSV-2 assay were 62.1% (95%CI: 49.3-73.8) and 41.9% (95%CI: 27.0-57.9), respectively. Increasing the HerpeSelect(®) HSV-2 index value defining a positive test result from >1.1 to ≥2.89 increased the assay's specificity to 97.7% (95%CI: 87.7-99.6) and the positive predictive value to 94.1%(95%CI: 71.2-99.0). J. Med. Virol. 9999: 1-5, 2015. © 2015 Wiley Periodicals, Inc. In veterans with chronic hepatitis C infection, HerpeSelect(®) HSV-2 index values between 1.1 and 2.89 should be confirmed with an alternate test for HSV-2 infection.

The Humoral Immune Response to HCV: Understanding is Key to Vaccine Development

Hepatitis C virus (HCV) remains a global problem, despite advances in treatment. The low cost and high benefit of vaccines have made them the backbone of modern public health strategies, and the fight against HCV will not be won without an effective vaccine. Achievement of this goal will benefit from a robust understanding of virus-host interactions and protective immunity in HCV infection. In this review, we summarize recent findings on HCV-specific antibody responses associated with chronic and spontaneously resolving human infection. In addition, we discuss specific epitopes within HCV's envelope glycoproteins that are targeted by neutralizing antibodies. Understanding what prompts or prevents a successful immune response leading to viral clearance or persistence is essential to designing a successful vaccine.

DNA vaccine expressing conserved influenza virus proteins protective against H5N1 challenge infection in mice

Influenza vaccination practice, which is based on neutralizing antibodies, requires being able to predict which viral strains will be circulating. If an unexpected strain, as in the 1997 H5N1 Hong Kong outbreak, or even a pandemic emerges, appropriate vaccines may take too long to prepare. Therefore, strategies based on conserved influenza antigens should be explored. We studied DNA vaccination in mice with plasmids expressing conserved nucleoprotein (NP) and matrix (M) from an H1N1 virus. After vaccination, mice were challenged with A/H5N1 viruses of low, intermediate, and high lethality. A/NP+A/M DNA vaccination reduced replication of A/Hong Kong/486/97 (HK/486), a nonlethal H5N1 strain, and protected against lethal challenge with more virulent A/Hong Kong/156/97 (HK/156). After HK/156 exposure, mice survived rechallenge with A/Hong Kong/483/97 (HK/483), although the DNA vaccination alone protected poorly against this highly virulent strain. In the absence of antigenically matched hemagglutinin-based vaccines, DNA vaccination with conserved influenza genes may provide a useful first line of defense against a rapidly spreading pandemic virus.

Secondary rearrangements and hypermutation generate sufficient B cell diversity to mount protective antiviral immunoglobulin responses

Variable (V) region gene replacement was recently implicated in B cell repertoire diversification, but the contribution of this mechanism to antibody responses is still unknown. To investigate the role of V gene replacements in the generation of antigen-specific antibodies, we analyzed antiviral immunoglobulin responses of "quasimonoclonal" (QM) mice. The B cells of QM mice are genetically committed to exclusively express the anti-(4-hydroxy-3-nitrophenyl) acetyl specificity. However, approximately 20% of the peripheral B cells of QM mice undergo secondary rearrangements and thereby potentially acquire new specificities. QM mice infected with vesicular stomatitis virus (VSV), lymphocytic choriomeningitis virus, or poliovirus mounted virus-specific neutralizing antibody responses. In general, kinetics of the antiviral immunoglobulin responses were delayed in QM mice; however, titers similar to control animals were eventually produced that were sufficient to protect against VSV-induced lethal disease. VSV neutralizing single-chain Fv fragments isolated from phage display libraries constructed from QM mice showed VH gene replacements and extensive hypermutation. Thus, our data demonstrate that secondary rearrangements and hypermutation can generate sufficient B cell diversity in QM mice to mount protective antiviral antibody responses, suggesting that these mechanisms might also contribute to the diversification of the B cell repertoire of normal mice.

Viral antibodies in blood in obsessive compulsive disorder

IgG viral antibodies for herpes simplex virus -1, varicella zoster virus, cytomegalovirus, measles and mumps were studied in 76 subjects with obsessive compulsive disorder and compared with a control population. There was a significantly higher titre for some of the antibodies, most specifically for herpes simplex virus type 1 and mumps. This suggests a possible role for these viral infections in the pathogenesis of obsessive compulsive disorder.

Risk factors in multiple sclerosis: a population-based case-control study in Hautes-Pyrénées, France

A population-based study of the prevalence and risk factors of multiple sclerosis (MS) was conducted in the Hautes-Pyrénées, the southwestern region of France. The prevalence rate per 100,000 was equal to 40. Data on the past medical history of 63 MS patients and matched controls were collected. The frequency and age at occurrence of common childhood infections were similar for both the MS cases and controls. There was no difference between the frequency of vaccination for MS patients and for controls. However, the age at which MS patients were immunized against poliomyelitis was significantly higher than the corresponding age for controls (15.8 years versus 8.9 years, P less than 0.01). Antibody titers for various viruses were measured. The mumps antibody titer was significantly higher in the MS patients than in the controls. Also, MS patients tended to have higher titers for measles antibodies.

Age-specific prevalence of complement-fixing antibodies to sixteen viral antigens: a computer analysis of 58,500 patients covering a period of eight years

The age-specific prevalence of CF antibodies against 16 viral antigens was determined by using the computerized data registry of the routine diagnostic laboratory of the authors' department. The material consisted of data based on serum specimens from about 58,500 patients. All ages from newborn infants to 90-year-olds were represented. The sera had been collected and tested with a CF screening test over a period of 8 years (1971-1978). Several different antibody prevalence patterns were distinguished in regard to the rapidity and timing of the initial increase of the prevalence, as well as to the mode of later changes in prevalence. For most respiratory viruses a rapid increase of the prevalence was seen through the childhood continuing, for some of them, up to the 30s (influenza A and coronavirus), while rather variable patterns were found in the older age groups. Herpes simplex and cytomegaloviruses showed, interestingly, another type of pattern: a slow increase of prevalence continuing through the whole age range. The frequency of herpes simplex antibodies reached 90% by the age of 80 years. Antibody levels against any antigen in infants less than one-month-old were equal to those in 20- to 40-year-old adults, and the expected rapid decrease of antibodies took place within the first 6 months of life. Possible influences of epidemics and repeated exposures to different viruses (external boosting), and of latent or chronic infections (internal boosting), as well as of technical variations, on the observed prevalence patterns are discussed.

Viral antibodies in multiple sclerosis

The sera of 176 MS patients and of 150 healthy adult controls were assayed for antibodies against mumps, rubella, Sendai and herpes simplex viruses, a higher prevalence of measles c.f.a. having already been demonstrated in the MS patients. The CSF of 48 of the MS patients were subjected to the same tests. The patients differed from the controls in a higher prevalence of h.i.a. to mumps and of c.f.a. to herpes simplex. For the latter, but not for the former, the prevalence was statistically higher only in patients treated with immunosuppressants. To date measles seems to be the most seriously incriminated virus in the etiopathogenesis of MS, mumps ranking second.