Utility of glutaraldehyde-fixed turkey red blood cells for influenza virus detection after 18 months of storage

Turkey red blood cells (tRBCs) are an essential reagent used in the laboratory diagnosis of influenza viruses. Fresh tRBCs when stored at 4 °C have a shelf life of less than a week. Previous studies have shown the utility of glutaraldehyde-fixed tRBCs, with an increased shelf life, for use in hemagglutination (HA) assays. In the present study, we report their functionality after storage for 18 months, at -80 °C. Three influenza A subtypes, namely, H3N2, H1N1 and H5N1, were used in the study. Hemagglutination assay was performed using freshly prepared 0.5 % tRBCs suspension and stored 1 % glutaraldehyde-fixed tRBCs. There was no significant difference in the HA titers obtained using fresh and stored tRBCs. The validation of the HA assay was carried out, to determine the specificity, linearity, precision, accuracy, and robustness of the assay. All of the titers were within the acceptable range, indicating the validity of the HA assay using stored tRBCs. Hemagglutination inhibition assay was also performed to compare the antibody titers obtained using stored and fresh tRBCs. The stored RBCs also gave equivalent antibody titers, as compared to the fresh tRBCs. Thus, the present study demonstrates the utility of glutaraldehyde-fixed tRBCs after one and a half years of storage.

Spatio-temporal distribution & seasonality of highly pathogenic avian influenza H5N1 & H5N8 outbreaks in India, 2006-2021

Background & objectives

The highly pathogenic avian influenza (HPAI) H5N1 and H5N8 viruses have been one of the leading causes of avian diseases worldwide, resulting in severe economic losses and posing potential zoonotic risk. There are no reports on the correlation of the seasonality of H5N1 and H5N8 viruses with the migratory bird season in India, along with the species affected. The present report describes the distribution and seasonality of HPAI outbreaks in India from 2006 to 2021.

Methods

The data on the occurrence and locations of outbreaks in India and affected bird species were collated from the Food and Agriculture Organization of the United Nations database and grouped by month and year. The distribution and seasonality of HPAI H5N1 and H5N8 viruses were analyzed.

Results

A total of 284 H5N1 outbreaks were reported since 2006, with a surge in 2021. The initial outbreaks of H5N1 were predominantly in poultry. Since 2016, 57 outbreaks of H5N8 were also reported, predominantly in wild birds. Most of the outbreaks of HPAI were reported from post monsoon onwards till pre-summer season (i.e. between October and March) with their peak in winter, in January. Apart from poultry, the bird species such as owl, Indian peafowl, lesser adjutant, crows and wild migratory birds such as demoiselle crane, northern pintail and bar-headed goose were positive for HPAI.

Interpretation & conclusions

Such studies on the seasonality of HPAI outbreaks would help in the development of prevention and control strategies. The recent human infections of H5N1 and H9N2 viruses highlight the need to strengthen surveillance in wild, resident, migratory birds and in poultry along with One Health studies in India.

The evolution, characterization and phylogeography of avian influenza H9N2 viruses from India

The low pathogenic avian influenza H9N2 virus is a significant zoonotic agent and contributes genes to highly pathogenic avian influenza (HPAI) viruses. H9N2 viruses are prevalent in India with a reported human case. We elucidate the spatio-temporal origins of the H9N2 viruses from India. A total of 30H9N2 viruses were isolated from poultry and environmental specimens (years 2015-2020). Genome sequences of H9N2 viruses (2003-2020) from India were analyzed, revealing several substitutions. We found five reassortant genotypes. The HA, NA and PB2 genes belonged to the Middle-Eastern B sublineage; NP and M to the classical G1 lineage; PB1, PA and NS showed resemblance to genes from either HPAI-H7N3/H5N1 viruses. Molecular clock and phylogeography revealed that the introduction of all the genes to India took place around the year 2000. This is the first report of the genesis and evolution of the H9N2 viruses from India, and highlights the need for surveillance.

Replication of SARS-CoV-2 in cell lines used in public health surveillance programmes with special emphasis on biosafety

Background & objectives

Polio, measles, rubella, influenza and rotavirus surveillance programmes are of great public health importance globally. Virus isolation using cell culture is an integral part of such programmes. Possibility of unintended isolation of SARS-CoV-2 from clinical specimens processed in biosafety level-2 (BSL-2) laboratories during the above-mentioned surveillance programmes, cannot be ruled out. The present study was conducted to assess the susceptibility of different cell lines to SARS-CoV-2 used in these programmes.

Methods

Replication of SARS-CoV-2 was studied in RD and L20B, Vero/hSLAM, MA-104 and Madin-Darby Canine Kidney (MDCK) cell lines, used for the isolation of polio, measles, rubella, rotavirus and influenza viruses, respectively. SARS-CoV-2 at 0.01 multiplicity of infection was inoculated and the viral growth was assessed by observation of cytopathic effects followed by real-time reverse transcription-polymerase chain reaction (qRT-PCR). Vero CCL-81 cell line was used as a positive control.

Results

SARS-CoV-2 replicated in Vero/hSLAM, and MA-104 cells, whereas it did not replicate in L20B, RD and MDCK cells. Vero/hSLAM, and Vero CCL-81 showed rounding, degeneration and detachment of cells; MA-104 cells also showed syncytia formation. In qRT-PCR, Vero/hSLAM and MA-104 showed 10⁶ and Vero CCL-81 showed 10⁷ viral RNA copies per μl. The 50 per cent tissue culture infectious dose titres of Vero/hSLAM, MA-104 and Vero CCL-81 were 10^5.54, 10^5.29 and 10^6.45/ml, respectively.

Interpretation & conclusions

Replication of SARS-CoV-2 in Vero/hSLAM and MA-104 underscores the possibility of its unintended isolation during surveillance procedures aiming to isolate measles, rubella and rotavirus. This could result in accidental exposure to high titres of SARS-CoV-2, which can result in laboratory acquired infections and community risk, highlighting the need for revisiting biosafety measures in public health laboratories.

Selection and application of biological safety cabinets in diagnostic and research laboratories with special emphasis on COVID-19

The ongoing coronavirus disease (COVID-19) pandemic is a global public health emergency. Adherence to biosafety practices is mandatory to protect the user as well as the environment, while handling infectious agents. A biological safety cabinet (BSC) is the most important equipment used in diagnostic and research laboratories in order to safeguard the product, the person, and the environment. The World Health Organization has emphasized the use of validated BSCs in order to ensure quality of the results. There are different classes of BSCs that are used in various work environments based on the need. It is imperative to use appropriate levels of biosafety and types of BSCs in laboratories based on the risk assessment of the pathogen used. During the development of COVID-19 laboratories and training of laboratory staff, we came across several queries about the functions and selection of BSCs and realized that the knowledge about the detailed information on selections and applications of BSCs is scanty. There are several guidelines regarding the biosafety aspects for diagnostic and research laboratories handling infectious pathogens from national and international agencies. However, there is no detailed information on the use of appropriate types of BSCs and their functions in the context of Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2). In view of this, the present paper describes in detail the selection and applications of BSCs, which could be useful for laboratories handling or planning to handle SARS-CoV-2 and suspected samples.

Application of frozen and stored glutaraldehyde-fixed turkey red blood cells for hemagglutination and hemagglutination inhibition assays for the detection and identification of influenza viruses

INTRODUCTION

Hemagglutination (HA) and hemagglutination inhibition (HI) assays are conventionally used for the detection and identification of influenza viruses, using red blood cells (RBCs) from mammalian and avian sources. However, there could be limitations for availability of fresh RBCs due to situations such as pandemics, public health emergencies, outbreaks in avian species, lack of animal facilities, animal ethics concerns; or resource-constrained laboratories, and laboratories which do not carry out HA and HI assays routinely. Turkey RBCs (tRBCs) are widely used for HA and HI assays of influenza viruses. The present study explored the possibility of the use of glutaraldehyde-fixed tRBCs, which could be stored at -80 ^ºC and readily used for HA and HI assays.

MATERIALS AND METHODS

A total of nine subtypes of human and avian influenza viruses, A H1N1, H3N2, H4N6, H5N1, H6N1, H7N9, H9N2, H11N1 and type B, were used in the study. Turkey RBCs were fixed with glutaraldehyde. The HA and HI assays were performed three times by two different operators using fresh and glutaraldehyde fixed tRBCs. The significance of difference in HA and HI titers between fixed and fresh RBCs was compared using 't-test'. The performance of fixed RBCs was evaluated before and after storing at -80 ^ºC for three weeks.

RESULTS

There was no significant difference (p > 0.05) between mean HA and HI titers using fresh and glutaraldehyde-fixed turkey RBCs. In addition, the HA and HI titers using fixed tRBCs before and after storing at -80 ^ºC were equivalent, indicating suitability of the fixed and stored RBCs.

CONCLUSIONS

This is the first report of the use of fixed and stored tRBCs for HA and HI assays of influenza viruses, highlighting their applicability as a ready-to-use reagent for laboratory diagnosis of influenza.

Steps, implementation and importance of quality management in diagnostic laboratories with special emphasis on coronavirus disease-2019

A well-established and functional quality management system is an integral part of any diagnostic laboratory. It assures the reliability and standards of the laboratory function. A pandemic situation such as that caused by the influenza H1N1 2009 virus or the recent severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) increases the demands on the public health system, and the need to build, upgrade and expand the number of diagnostic laboratories. The Coronavirus disease-19 (COVID-19) pandemic caused by the SARS-CoV-2 unleashed a public health emergency of an unprecedented scale. The need has been highlighted for the accreditation of tests relating to COVID-19 by the National Accreditation Board for Testing and Calibration Laboratories (NABL) or any agencies approved by the World Health Organization (WHO) or Indian Council of Medical Research. The implementation of quality system in diagnostic laboratories would ensure accurate, reliable and efficient test results at par with the international standards. The functional aspects of a laboratory such as a well-defined organogram, standard operating procedures, good laboratory practices, quality controls, human resources, equipment management, reagents, inventory of records, proper communication need to be addressed to assure quality. Biosafety considerations should include the guidelines laid out by the WHO, the Institutional Biosafety Committee and the Department of Biotechnology, Government of India for carrying out diagnostic work in the laboratory. Currently, there are 1922 laboratories, operational for COVID-19 diagnosis in India. Considering the urgency of testing, the NABL has expedited the process of accreditation and issued accreditation to 818 laboratories. The adherence to the practicable aspects of quality described in this article would help in establishing quality in COVID-19 testing laboratories.

Assessing the susceptibility of highly pathogenic avian influenza H5N1 viruses to oseltamivir using embryonated chicken eggs

Background & objectives:

The susceptibility of influenza viruses to neuraminidase inhibitors (NAIs) is studied using enzyme-based assays, sequence analysis and in vitro and in vivo studies. Oseltamivir carboxylate (OC) is the active prodrug of the NAI oseltamivir. There is lack of information on the use of embryonated chicken eggs for studying susceptibility of highly pathogenic avian influenza (HPAI) H5N1 viruses to antiviral drugs. The aim of the present study was to assess the use of 10 day old embryonated chicken eggs for studying antiviral susceptibility of HPAI H5N1 viruses.

Methods:

Two HPAI H5N1 viruses isolated from India were used in the study. Fluorescence-based NAI assay was performed to determine antiviral susceptibility of these viruses. In ovo antiviral assays were carried out using 10 day old embryonated chicken eggs. The virus dilutions were incubated with 14 μg/ml of OC and inoculated in the allantoic cavity. In the eggs, 50 per cent egg infectious dose (EID₅₀) titres as well as mortality were quantitated.

Results:

The two viruses used were susceptible to OC in the NAI assay. It was found that there was a significant drop in EID₅₀ titres; however, no significant protection from mortality after OC treatment was observed.

Interpretation & conclusions:

By measuring viral titres, the egg model was suitable to study the susceptibility of HPAI viruses to antiviral drugs along with NAI assay. The present study highlights the use of eggs as a model to study susceptibility of HPAI viruses to OC.

A virus precipitation method for concentration & detection of avian influenza viruses from environmental water resources & its possible application in outbreak investigations

Background & objectives

Avian influenza (AI) viruses have been a major cause of public health concern. Wild migratory birds and contaminated environmental sources such as waterbodies soiled with bird droppings play a significant role in the transmission of AI viruses. The objective of the present study was to develop a sensitive and user-friendly method for the concentration and detection of AI viruses from environmental water sources.

Methods

Municipal potable water, surface water from reservoirs and sea were spiked with low pathogenic AI viruses. To concentrate the viruses by precipitation, a combination of potassium aluminium sulphate with milk powder was used. Real-time reverse transcription-polymerase chain reaction was performed for virus detection, and the results were compared with a virus concentration method using erythrocytes. Drinking water specimens from poultry markets were also tested for the presence of AI viruses.

Results

A minimum of 10^1.0 EID₅₀(50% egg infectious dose)/ml spiked H5N1 and 10^1.7 EID₅₀/ml spiked H9N2 viruses were detected from spiked potable water; 10^1.0 and 10^2.0 EID₅₀/ml spiked H5N1 virus was detected from surface water and seawater samples, respectively. The present method was more sensitive than the erythrocyte-binding method as approximately 10-fold higher infectious virus titres were obtained. AI H9N2 viruses were detected and isolated from water from local poultry markets, using this method.

Interpretation & conclusions

Viability and recovery of the spiked viruses were not affected by precipitation. The present method may be suitable for the detection of AI viruses from different environmental water sources and can also be applied during outbreak investigations.

Amantadine resistance markers among low pathogenic avian influenza H9N2 viruses isolated from poultry in India, during 2009-2017

Antiviral susceptibility screening of avian influenza (AI) H9N2 viruses is crucial considering their role at the animal-human interface and potential to cause human infections. The Matrix 2 (M2) inhibitors (amantadine and rimantadine) have been used for prophylaxis and treatment of influenza A virus infections, however, resistance to these drugs has been widely reported. Information about amantadine susceptibility of H9N2 viruses from India is scanty. Matrix genes of 48H9N2 viruses isolated from India during 2009-2017 were sequenced and M2 trans-membrane region sequences were screened for mutations which are known to confer resistance to amantadine namely, L26F, V27A, A30 T/V, S31N and G34E. All the viruses isolated during the year 2009 were sensitive to amantadine. However, resistance started to appear since the year 2010 and all the viruses isolated from the year 2015 onwards showed presence of molecular markers conferring resistance to amantadine. Majority of the resistant viruses exhibited S31 N mutation. Four isolates showed presence of V27A + S31 N dual mutations. Comparison of the M2 sequences from other Asian countries showed different patterns of amantadine resistance wherein phylogenetic analysis of the M genes of the strains from Pakistan formed a separate cluster. In conclusion, the present study reports prevalence and gradual increase of amantadine resistance among AI H9N2 viruses in India, emphasizing the importance of the antiviral surveillance.

A novel I117T substitution in neuraminidase of highly pathogenic avian influenza H5N1 virus conferring reduced susceptibility to oseltamivir and zanamivir

Occurrence of avian influenza (AI) with Neuraminidase (NA) mutations which confer reduced neuraminidase inhibitor (NAI) susceptibility has remained a cause of concern. The susceptibility to NAIs of 67 highly pathogenic avian influenza H5N1 viruses isolated during 2006-2012 in India was tested in phenotypic fluorescence-based NA inhibition assay, sequence analysis and in ovo. One isolate showed a novel NA I117T amino acid substitution (N2 numbering) and eight isolates showed previously known NAI-resistance marker mutations (I117V, E119D, N294S, total 9/67). The overall incidence of resistant variants was 13.4%. The novel I117T substitution reduced oseltamivir susceptibility by 18.6-fold and zanamivir susceptibility by 11.8-fold, compared to the wild type AI H5N1virus, thus showed cross-resistance to both oseltamivir and zanamivir in NA inhibition assays. However, the other two isolates with I117V substitution were sensitive to both the NAIs. In addition, the comparison of growth of the I117T and I117V variants in presence of NAI's in the in ovo assays exhibited difference in growth levels. The present study reports the natural occurrence of a novel I117T mutation in AI H5N1 virus conferring cross-resistance to oseltamivir and zanamivir highlighting the urgent need of antiviral surveillance of AI viruses.

Morphological and Biochemical Characteristics of Avian Faecal Droppings and Their Impact on Survival of Avian Influenza Virus

Environmental specimens such as faecal droppings are considered important for the detection of avian influenza viruses (AIV). In view of lower rates of AIV isolation from avian faecal droppings, characterization of droppings is imperative to elucidate contributing factors. However, there are no reports on morphological and biochemical characteristics of droppings. The objective of the present study was the characterization of droppings from different avian species and their impact on the AIV detection and isolation. A total of 373 droppings belonging to 61 avian species from 22 families of apparently healthy wild migratory, resident, domestic birds and poultry were studied during five winter migratory bird seasons between 2007 to 2012 and 2016-2017. The colour, morphology and size of the droppings varied from species-to-species. These data could be useful for the identification of avian species. Droppings from 67% of the avian species showed acidic pH (4.5-6.5); nine species showed neutral pH (7.0), and 11 species showed alkaline pH (7.5). The infectious titers of AIV in droppings with acidic pH were significantly lower (p < 0.05) than those of the droppings with neutral and alkaline pH. However, acidic pH did not hamper AIV detection by real-time RT-PCR. In order to avoid the impact of acidic pH, collecting fresh droppings into viral transport medium (pH 7.0-7.5) would help improve the rate of AIV isolation.