Biology subjects

Duggal, N. K.

Publications and source records attributed to Duggal, N. K..

6 recordsLinked to original sources

bioRxiv2022

Environmental Stability of Enveloped Viruses is Impacted by the Initial Volume and Evaporation Kinetics of Droplets

Efficient spread of respiratory viruses requires the virus to maintain infectivity in the environment. Environmental stability of viruses can be influenced by many factors, including temperature and humidity. Our study measured the impact of initial droplet volume (50, 5, and 1 {micro}L) and relative humidity (RH: 40%, 65%, and 85%) on the stability of influenza A virus, bacteriophage, Phi6, a common surrogate for enveloped viruses, and SARS-CoV-2 under a limited set of conditions. Our data suggest that the drying time required for the droplets to reach quasi-equilibrium (i.e. a plateau in mass) varied with RH and initial droplet volume. The macroscale physical characteristics of the droplets at quasi-equilibrium varied with RH but not with initial droplet volume. We observed more rapid virus decay when the droplets were still wet and undergoing evaporation, and slower decay after the droplets had dried. Initial droplet volume had a major effect on virus viability over the first few hours; whereby the decay rate of influenza virus was faster in smaller droplets. In general, influenza virus and SARS-CoV-2 decayed similarly. Overall, this study suggests that virus decay in media is closely correlated with the extent of droplet evaporation, which is controlled by RH. Taken together, these data suggest that decay of different viruses is more similar at higher RH and in smaller droplets and is distinct at lower RH and in larger droplets. Importantly, accurate assessment of transmission risk requires use of physiologically relevant droplet volumes and careful consideration of the use of surrogates. FundingNational Institute of Allergy and Infectious Diseases, National Institute of Neurological Disorders and Stroke, National Institutes of Health; Department of Health and Human Services; Flu Lab. ImportanceDuring the COVID-19 pandemic, policy decisions were being driven by virus stability experiments involving SARS-CoV-2 applied to surfaces in large droplets at various humidity conditions. The results of our study indicate that determination of half-lives for emerging pathogens in large droplets likely over-estimates transmission risk for contaminated surfaces, as occurred during the COVID-19 pandemic. Our study implicates the need for the use of physiologically relevant droplet sizes with use of relevant surrogates in addition to what is already known about the importance of physiologically relevant media for risk assessment of future emerging pathogens.

microbiology↗

bioRxiv2021

Infectious SARS-CoV-2 is emitted in aerosols

Respiratory viruses such as SARS-CoV-2 are transmitted in respiratory droplets and aerosols, which are released during talking, breathing, coughing, and sneezing. Non-contact transmission of SARS-CoV-2 has been demonstrated, suggesting transmission in aerosols. Here we demonstrate that golden Syrian hamsters emit infectious SARS-CoV-2 in aerosols, prior to and concurrent with the onset of mild clinical signs of disease. The average emission rate is 25 infectious virions/hour on days 1 and 2 post-inoculation, with average viral RNA levels 200-fold higher than infectious virus in aerosols. Female hamsters have delayed kinetics of viral shedding in aerosols compared to male hamsters, with peak viral emission for females on dpi 2 and for males on dpi 1. The majority of virus is contained within aerosols <8 {micro}m in size. Thus, we provide direct evidence that, in hamsters, SARS-CoV-2 is an airborne virus.

microbiology↗

bioRxiv2021

Adenovirus transduction to express human ACE2 causes obesity-specific morbidity in mice, impeding studies on the effect of host nutritional status on SARS-CoV-2 pathogenesis.

The COVID-19 pandemic has paralyzed the global economy and resulted in millions of deaths globally. People with co-morbidities like obesity, diabetes and hypertension are at an increased risk for severe COVID-19 illness. This is of overwhelming concern because 42% of Americans are obese, 30% are pre-diabetic and 9.4% have clinical diabetes. Here, we investigated the effect of obesity on disease severity following SARS-CoV-2 infection using a well-established mouse model of diet-induced obesity. Diet-induced obese and lean control C57BL/6N mice, transduced for ACE2 expression using replication-defective adenovirus, were infected with SARS-CoV-2, and monitored for lung pathology, viral titers, and cytokine expression. No significant differences in tissue pathology, viral replication or cytokine expression were observed between lean and obese groups. Notably, significant weight loss was observed in obese mice treated with the adenovirus vector, independent of SARS-CoV-2 infection, suggesting an obesity-dependent morbidity induced by the vector. These data indicate that the adenovirus-transduced mouse model of SARS-CoV-2 infection is inadequate for performing nutrition studies, and caution should be used when interpreting resulting data.

pathology↗

bioRxiv2020

Persistence of Zika virus RNA in the epididymis of the male reproductive tract

Zika virus (ZIKV) can infect developing fetuses in utero and cause severe congenital defects. This in utero transmission can occurs following ZIKV infection during pregnancy via sexual transmission or mosquito bite. Infected men may shed ZIKV RNA in semen for over six months post symptom onset, indicating that ZIKV may persistently infect the male reproductive tract (MRT). However, the site of persistent infection in the MRT and whether ZIKV can recrudesce in the MRT is unknown. We hypothesized that if ZIKV establishes a persistent infection in the MRT, then immunosuppressant treatment should stimulate ZIKV replication. We tested this hypothesis in a wild-type mouse model of ZIKV sexual transmission. Male mice were infected with ZIKV and immunosuppressed when they no longer shed infectious virus in their ejaculates. After immunosuppression, ejaculates and MRT tissues were monitored for infectious virus and ZIKV RNA. Our results show that ZIKV recrudescence did not occur following immunosuppression, as we did not detect significant levels of infectious virus in ejaculates or MRT tissues following immunosuppression. We did detect ZIKV RNA in the epididymides of mice treated with the immunosuppressant cyclophosphamide. Further analysis revealed that this ZIKV RNA was contained within the lumen of the epididymis. Our findings suggest that ZIKV persistently infects the epididymis within the male reproductive tract. This study provides insight into the mechanisms behind ZIKV sexual transmission, which may inform public health decisions regarding ZIKV risks. ImportanceZika virus (ZIKV) is an emerging mosquito-transmitted virus that typically causes mild and self-limiting febrile illness in humans; however, during the recent epidemic of ZIKV in the Americas, severe birth defects, such as microcephaly and club foot, were reported in infants born to ZIKV infected mothers. Additionally, sexual transmission has been identified as a secondary method of ZIKV transmission. Since ZIKV can be isolated from semen of infected men long after initial infection, it is imperative to understand the mechanism(s) of ZIKV infection of the male reproductive tract to prevent sexual transmission and ZIKV-associated birth defects. The significance of our research is in identifying a site of persistent ZIKV infection in the male reproductive tract and in assessing the likelihood that a persistently infected individual will begin shedding infectious virus in semen again. This information will enhance our understanding of ZIKV sexual transmission and inform health decisions regarding ZIKV risks.

microbiology↗

bioRxiv2020

Differential pathogenesis of Usutu virus isolates in mice

Usutu virus (USUV; Flavivirus), a close phylogenetic and ecological relative of West Nile virus, is a zoonotic virus that can cause neuroinvasive disease in humans. USUV is maintained in an enzootic cycle between Culex mosquitoes and birds. Since the first isolation in 1959 in South Africa, USUV has spread throughout Africa and Europe. Reported human cases have increased over the last few decades, primarily in Europe, with symptoms ranging from mild febrile illness to severe neurological effects. In this study, we investigated whether USUV has become more pathogenic during emergence in Europe. Interferon /{beta} receptor knockout (Ifnar1-/-) mice were inoculated with recent USUV isolates from Africa and Europe, as well as the historic 1959 South African strain. The three tested African strains and one European strain from Spain caused 100% mortality in inoculated mice, with similar survival times and histopathology in tissues. Unexpectedly, a European strain from the Netherlands caused only 12% mortality and significantly less histopathology in tissues from mice compared to mice inoculated with the other strains. Viremia was highest in mice inoculated with the recent African strains and lowest in mice inoculated with the Netherlands strain. Based on phylogenetics, the USUV isolates from Spain and the Netherlands were derived from separate introductions into Europe, suggesting that disease outcomes may differ for USUV strains circulating in Europe. These results also suggest that while more human USUV disease cases have been reported in Europe recently, circulating African USUV strains are still a potential major health concern. Author SummaryUsutu virus (USUV) is an emerging mosquito-borne virus that causes severe neuroinvasive disease in humans. USUV was first detected in Africa in 1959, and cases of human disease have increased in recent years. Most USUV disease cases are now reported in Europe, where the virus currently circulating. One possibility for the increase in case numbers is that USUV strains have become more pathogenic over time during its spread from Africa into Europe. We compared the pathogenesis of five USUV isolates from Africa and Europe in a mouse model. Three isolates from Africa and one isolate from Europe caused 100% mortality in mice. Surprisingly, one isolate from Netherlands caused only 12% motality. Significantly less histopathology was observed in tissues from mice inoculated with the Netherlands strain compared to mice inoculated with the other four strains. Our results suggest that, even though more human USUV disease cases have been reported in Europe recently, African USUV strains are also highly pathogenic.

microbiology↗

bioRxiv2020

Development and characterization of infectious clones of two strains of Usutu virus

Usutu virus (USUV; genus Flavivirus; family Flaviviridae) is a mosquito-borne, positive-sense RNA virus that is currently causing significant die-offs in numerous bird species throughout Europe and has caused infections in humans. Currently, there are no molecular clones for USUV, hence, hindering studies on the pathogenesis and transmission of USUV. In this report, we demonstrate the development and characterization of infectious clones for two modern strains of USUV isolated from Europe and Africa. We show that the infectious clone-derived viruses replicated similarly to the parental strains in both mammalian and insect cells. Additionally, we observed similar levels of replication and pathogenesis in two mouse models. This reverse genetics system will aid the scientific community in studying and developing USUV infection, transmission, diagnostics, and vaccines.

molecular biology↗