36 research outputs found
Study of the surface glycoprotein of Rift Valley fever virus using monoclonal antibodies
A thesis submitted to the Faculty of Medicine
University of the Witwatersrand, Johannesburg
for the De +ee of Doctor of Philosophy
Johannesburg, 1992The structural, functional and antigenic properties of the envelope glycoproteins
of Rift Valley fever virus (RVFV) were analyzed using a panel of monoclonal
antibodies (MAbs). In order to gain a better understanding of the role of the
RVFV surface proteins in infection and pathogenesis, the mechanisms ofanti:~odymediated
neutralization of the virus were examined, as well as the fl}action of the
glycoproteins in viral attachment and penetration.
Of the twenty three MAbs which were generated, fourteen were directed against
the G1 and nine against the G2 protein of RVFV. The topological relationship
of the antigenic determinants to each other on the viral glycoproteins was achieved
using competitive binding assays with enzyme-labelled MAbs. For the RVFV 01
protein, four antigenic domains which may be interlinked were identified. The
domains G1 I, II and IV were involved in virus neutralization and
haemagglutination, while G1 III was associated with low level C'-dependent
neutralization.
With regard to the G2 protein, four antigenic domains which appear to be
spatially distinct were identified. Domain G2 I exhibited significant neutralizing
and haemagglutination activity, while G2 II was involved in haernagglutination
and weak C(-dependent neutralization. The remaining 02 regions neutralized to
a low level only in the presence of C'. The majority of the epitopes on bath viral
glycoproteins were highly conformational, indicating that the native protein
structure is necessary for the recognition and expression of the functional
activities of these particular antibodies.
Protective determinants were shown to occur on both Gland 02, demonstrating
that both RVFV envelope proteins are important in viral pathogenesis. The
neutralization studies, in turn, revealed that the inhibition of virus attachment is
not the principal means of antibody-mediated neutralization of RVFV. Instead,
such ..ieutralization appears to be the result of several different processes,
including synergistic neutralization by combinations of different antibodies,
prevention of virus binding, virus internalization and the blocking of the viral life
cycle at an intracellular stage. Further insight into RVFV infectivity was obtained
by showing that both glycoproteins are involved in virus entry into the host cell.
Finally, the present. findings strongly support an endosomal route of entry and
penetration for RVFV, associated with concomitant allosteric changes in the 01
protein
Revision of clinical case definitions: influenza-like illness and severe acute respiratory infection
Abstract in English, Arabic, Chinese, French, Russian, SpanishThe formulation of accurate clinical case definitions is an integral part of an effective process of public health surveillance. Although such definitions should, ideally, be based on a standardized and fixed collection of defining criteria, they often require revision to reflect new knowledge of the condition involved and improvements in diagnostic testing. Optimal case definitions also need to have a balance of sensitivity and specificity that reflects their intended use. After the 2009-2010 H1N1 influenza pandemic, the World Health Organization (WHO) initiated a technical consultation on global influenza surveillance. This prompted improvements in the sensitivity and specificity of the case definition for influenza - i.e. a respiratory disease that lacks uniquely defining symptomology. The revision process not only modified the definition of influenza-like illness, to include a simplified list of the criteria shown to be most predictive of influenza infection, but also clarified the language used for the definition, to enhance interpretability. To capture severe cases of influenza that required hospitalization, a new case definition was also developed for severe acute respiratory infection in all age groups. The new definitions have been found to capture more cases without compromising specificity. Despite the challenge still posed in the clinical separation of influenza from other respiratory infections, the global use of the new WHO case definitions should help determine global trends in the characteristics and transmission of influenza viruses and the associated disease burden.info:eu-repo/semantics/publishedVersio
Epidemiology of influenza B/Yamagata and B/Victoria lineages in South Africa, 2005-2014
BACKGROUND : Studies describing the epidemiology of influenza B lineages in South Africa are lacking. METHODS : We conducted a prospective study to describe the circulation of influenza B/Victoria and B/
Yamagata lineages among patients of all ages enrolled in South Africa through three respiratory
illness surveillance systems between 2005 and 2014: (i) the Viral Watch (VW) program
enrolled outpatients with influenza-like illness (ILI) from private healthcare facilities
during 2005±2014; (ii) the influenza-like illnesses program enrolled outpatients in public
healthcare clinics (ILI/PHC) during 2012±2014; and (iii) the severe acute respiratory illnesses
(SARI) program enrolled inpatients from public hospitals during 2009±2014. Influenza
B viruses were detected by virus isolation during 2005 to 2009 and by real-time
reverse transcription polymerase chain reaction from 2009±2014. Clinical and epidemiological
characteristics of patients hospitalized with SARI and infected with different influenza B
lineages were also compared using unconditional logistic regression.
RESULTS : Influenza viruses were detected in 22% (8,706/39,804) of specimens from patients with ILI
or SARI during 2005±2014, of which 24% (2,087) were positive for influenza B. Influenza B
viruses predominated in all three surveillance systems in 2010. B/Victoria predominated prior to 2011 (except 2008) whereas B/Yamagata predominated thereafter (except 2012). B
lineages co-circulated in all seasons, except in 2013 and 2014 for SARI and ILI/PHC surveillance.
Among influenza B-positive SARI cases, the detection of influenza B/Yamagata compared
to influenza B/Victoria was significantly higher in individuals aged 45±64 years
(adjusted odds ratio [aOR]: 4.2; 95% confidence interval [CI]: 1.1±16.5) and 65 years
(aOR: 12.2; 95% CI: 2.3±64.4) compared to children aged 0±4 years, but was significantly
lower in HIV-infected patients (aOR: 0.4; 95% CI: 0.2±0.9).
CONCLUSION : B lineages co-circulated in most seasons except in 2013 and 2014. Hospitalized SARI
cases display differential susceptibility for the two influenza B lineages, with B/Victoria being
more prevalent among children and HIV-infected persons.The National
Institute for Communicable Diseases (NICD)
(http://www.nicd.ac.za/) and the US Centers for
Disease Control and Prevention (https://www.cdc.
gov/) grant number 5U51/IP000155.http://www.plosone.orgam2017Medical Virolog
Global update on the susceptibility of human influenza viruses to neuraminidase inhibitors, 2015-2016.
Four World Health Organization (WHO) Collaborating Centres for Reference and Research on Influenza and one WHO Collaborating Centre for the Surveillance, Epidemiology and Control of Influenza (WHO CCs) assessed antiviral susceptibility of 14,330 influenza A and B viruses collected by WHO-recognized National Influenza Centres (NICs) between May 2015 and May 2016. Neuraminidase (NA) inhibition assay was used to determine 50% inhibitory concentration (IC50) data for NA inhibitors (NAIs) oseltamivir, zanamivir, peramivir and laninamivir. Furthermore, NA sequences from 13,484 influenza viruses were retrieved from public sequence databases and screened for amino acid substitutions (AAS) associated with reduced inhibition (RI) or highly reduced inhibition (HRI) by NAIs. Of the viruses tested by WHO CCs 93% were from three WHO regions: Western Pacific, the Americas and Europe. Approximately 0.8% (n = 113) exhibited either RI or HRI by at least one of four NAIs. As in previous seasons, the most common NA AAS was H275Y in A(H1N1)pdm09 viruses, which confers HRI by oseltamivir and peramivir. Two A(H1N1)pdm09 viruses carried a rare NA AAS, S247R, shown in this study to confer RI/HRI by the four NAIs. The overall frequency of A(H1N1)pdm09 viruses containing NA AAS associated with RI/HRI was approximately 1.8% (125/6915), which is slightly higher than in the previous 2014-15 season (0.5%). Three B/Victoria-lineage viruses contained a new AAS, NA H134N, which conferred HRI by zanamivir and laninamivir, and borderline HRI by peramivir. A single B/Victoria-lineage virus harboured NA G104E, which was associated with HRI by all four NAIs. The overall frequency of RI/HRI phenotype among type B viruses was approximately 0.6% (43/7677), which is lower than that in the previous season. Overall, the vast majority (>99%) of the viruses tested by WHO CCs were susceptible to all four NAIs, showing normal inhibition (NI). Hence, NAIs remain the recommended antivirals for treatment of influenza virus infections. Nevertheless, our data indicate that it is prudent to continue drug susceptibility monitoring using both NAI assay and sequence analysis
Results from the WHO external quality assessment for the respiratory syncytial virus pilot, 2016-17
Background:
External quality assessments (EQAs) for the molecular detection of
respiratory syncytial virus (RSV) are necessary to ensure the provision
of reliable and accurate results. One of the objectives of the pilot of
the World Health Organization (WHO) Global RSV Surveillance, 2016-2017,
was to evaluate and standardize RSV molecular tests used by
participating countries. This paper describes the first WHO RSV EQA for
the molecular detection of RSV.
Methods:
The WHO implemented the pilot of Global RSV Surveillance based on
the WHO Global Influenza Surveillance and Response System (GISRS) from
2016 to 2018 in 14 countries. To ensure standardization of tests, 13
participating laboratories were required to complete a 12 panel RSV EQA
prepared and distributed by the Centers for Disease Control and
Prevention (CDC), USA. The 14th laboratory joined the pilot late and
participated in a separate EQA. Laboratories evaluated a RSV rRT-PCR
assay developed by CDC and compared where applicable, other Laboratory
Developed Tests (LDTs) or commercial assays already in use at their
laboratories.
Results:
Laboratories performed well using the CDC RSV rRT-PCR in
comparison with LDTs and commercial assays. Using the CDC assay, 11 of
13 laboratories reported correct results. Two laboratories each reported
one false-positive finding. Of the laboratories using LDTs or
commercial assays, results as assessed by Ct values were 100% correct
for 1/5 (20%). With corrective actions, all laboratories achieved
satisfactory outputs.
Conclusions:
These findings indicate that reliable results can be expected from
this pilot. Continued participation in EQAs for the molecular detection
of RSV is recommended.
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Results from the WHO external quality assessment for the respiratory syncytial virus pilot, 2016-17
BACKGROUND : External quality assessments (EQAs) for the molecular detection of respiratory
syncytial virus (RSV) are necessary to ensure the provision of reliable and accurate results. One of the objectives of the pilot of the World Health Organization
(WHO) Global RSV Surveillance, 2016-2017, was to evaluate and standardize RSV
molecular tests used by participating countries. This paper describes the first WHO
RSV EQA for the molecular detection of RSV.
METHODS : The WHO implemented the pilot of Global RSV Surveillance based on the
WHO Global Influenza Surveillance and Response System (GISRS) from 2016 to 2018
in 14 countries. To ensure standardization of tests, 13 participating laboratories were
required to complete a 12 panel RSV EQA prepared and distributed by the Centers for
Disease Control and Prevention (CDC), USA. The 14th laboratory joined the pilot late
and participated in a separate EQA. Laboratories evaluated a RSV rRT-PCR assay developed
by CDC and compared where applicable, other Laboratory Developed Tests
(LDTs) or commercial assays already in use at their laboratories.
RESULTS : Laboratories performed well using the CDC RSV rRT-PCR in comparison with
LDTs and commercial assays. Using the CDC assay, 11 of 13 laboratories reported correct
results. Two laboratories each reported one false-positive finding. Of the laboratories
using LDTs or commercial assays, results as assessed by Ct values were 100% correct
for 1/5 (20%). With corrective actions, all laboratories achieved satisfactory outputs.
CONCLUSIONS : These findings indicate that reliable results can be expected from
this pilot. Continued participation in EQAs for the molecular detection of RSV is recommended.The Bill and Melinda Gates Foundation, the Respiratory Viruses Branch, Division of Viral Diseases, CDC, Atlanta, and the CDC International Reagent Resource (IRR), USA.http://www.wileyonlinelibrary.com/journal/irvam2020Medical Virolog
Revision of clinical case definitions: influenza-like illness and severe acute respiratory infection
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