Comparison of Plaque Size, Thermal Stability, and Replication Rate among SARS-CoV-2 Variants of Concern

SARS-CoV-2, like other RNA viruses, has a propensity for genetic evolution owing to the low fidelity of its viral polymerase. Several recent reports have described a series of novel SARS-CoV-2 variants. Some of these have been identified as variants of concern (VOCs), including alpha (B.1.1.7, Clade GRY), beta (B.1.351, Clade GH), gamma (P.1, Clade GR), and delta (B.1.617.2, Clade G). VOCs are likely to have some effect on transmissibility, antibody evasion, and changes in therapeutic or vaccine effectiveness. However, the physiological and virological understanding of these variants remains poor. We demonstrated that these four VOCs exhibited differences in plaque size, thermal stability at physiological temperature, and replication rates. The mean plaque size of beta was the largest, followed by those of gamma, delta, and alpha. Thermal stability, evaluated by measuring infectivity and half-life after prolonged incubation at physiological temperature, was correlated with plaque size in all variants except alpha. However, despite its relatively high thermal stability, alpha’s small plaque size resulted in lower replication rates and fewer progeny viruses. Our findings may inform further virological studies of SARS-CoV-2 variant characteristics, VOCs, and variants of interest. These studies are important for the effective management of the COVID-19 pandemic.

Histopathological Spectrum of Spongiotic Dermatitis from a Tertiary Care Centre

BACKGROUND Spongiotic dermatitis is a common diagnosis in routine dermatopathology practice. Clinically it includes eczema and its clinicopathological variants. The main purpose of a biopsy in such cases is to come to a precise diagnosis. We wanted to study the different histopathological features commonly seen in spongiotic dermatitis. METHODS This is a cross sectional study conducted at a Government Medical College in Kerala, South India. All lesions reported as cases belonging to the category of spongiotic dermatitis during the one-year period were included in the study. Patients who presented with an established diagnosis of spongiotic dermatitis were excluded from the study. The study included 41 skin biopsies. RESULTS The age distribution pattern revealed that the highest percentage was in the 10 - 20 years age group (21.95 %) with a male preponderance (68.29 %). Small plaque parapsoriasis was the most common lesion (24 %) encountered in the study. CONCLUSIONS Some of the histopathological features are specific and characteristic for each entity like small plaque parapsoriasis, pityriasis rosea and erythema annulare centrifugum whereas some features overlap in lesions like irritant contact dermatitis and photoallergic contact dermatitis. Therefore, clinical history combined with microscopic features will help us render a precise diagnosis. KEYWORDS Spongiotic, Dermatitis, Inflammatory, Histopathological

The Molluscum Contagiosum Gene MC021L Partially Compensates for the Loss of Its Vaccinia Virus Homolog, F13L

ABSTRACT Orthopoxviruses produce two antigenically distinct infectious enveloped virions termed intracellular mature virions and extracellular virions (EV). EV have an additional membrane compared to intracellular mature virions due to a wrapping process at the trans-Golgi network and are required for cell-to-cell spread and pathogenesis. Specific to the EV membrane are a number of proteins highly conserved among orthopoxviruses, including F13, which is required for the efficient wrapping of intracellular mature virions to produce EV and which plays a role in EV entry. The distantly related molluscipoxvirus, molluscum contagiosum virus, is predicted to encode several vaccinia virus homologs of EV-specific proteins, including the homolog of F13L, MC021L. To study the function of MC021, we replaced the F13L open reading frame in vaccinia virus with an epitope-tagged version of MC021L. The resulting virus (vMC021L-HA) had a small-plaque phenotype compared to vF13L-HA but larger than vΔF13L. The localization of MC021-HA was markedly different from that of F13-HA in infected cells, but MC021-HA was still incorporated in the EV membrane. Similar to F13-HA, MC021-HA was capable of interacting with both A33 and B5. Although MC021-HA expression did not fully restore plaque size, vMC021L-HA produced amounts of EV similar to those produced by vF13L-HA, suggesting that MC021 retained some of the functionality of F13. Further analysis revealed that EV produced from vMC021L-HA exhibit a marked reduction in target cell binding and an increase in dissolution, both of which correlated with a small-plaque phenotype. IMPORTANCE The vaccinia virus extracellular virion protein F13 is required for the production and release of infectious extracellular virus, which in turn is essential for the subsequent spread and pathogenesis of orthopoxviruses. Molluscum contagiosum virus infects millions of people worldwide each year, but it is unknown whether EV are produced during infection for spread. Molluscum contagiosum virus contains a homolog of F13L termed MC021L. To study the potential function of this homolog during infection, we utilized vaccinia virus as a surrogate and showed that a vaccinia virus expressing MC021L-HA in place of F13L-HA exhibits a small-plaque phenotype but produces similar levels of EV. These results suggest that MC021-HA can compensate for the loss of F13-HA by facilitating wrapping to produce EV and further delineates the dual role of F13 during infection.

Characterization of Plaque Variants and the Involvement of Quasi-Species in a Population of EV-A71

Viral plaque morphologies in human cell lines are markers for growth capability and they have been used to assess the viral fitness and selection of attenuated mutants for live-attenuated vaccine development. In this study, we investigate whether the naturally occurring plaque size variation reflects the virulence of the variants of EV-A71. Variants of two different plaque sizes (big and small) from EV-A71 sub-genotype B4 strain 41 were characterized. The plaque variants displayed different in vitro growth kinetics compared to the parental wild type. The plaque variants showed specific mutations being present in each variant strain. The big plaque variants showed four mutations I97L, N104S, S246P and N282D in the VP1 while the small plaque variants showed I97T, N237T and T292A in the VP1. No other mutations were detected in the whole genome of the two variants. The variants showed stable homogenous small plaques and big plaques, respectively, when re-infected in rhabdomyosarcoma (RD) and Vero cells. The parental strain showed faster growth kinetics and had higher viral RNA copy number than both the big and small plaque variants. Homology modelling shows that both plaque variants have differences in the structure of the VP1 protein due to the presence of unique spontaneous mutations found in each plaque variant This study suggests that the EV-A71 sub-genotype B4 strain 41 has at least two variants with different plaque morphologies. These differences were likely due to the presence of spontaneous mutations that are unique to each of the plaque variants. The ability to maintain the respective plaque morphology upon passaging indicates the presence of quasi-species in the parental population.

Resolution of post-adalimumab vitiligo with secukinumab in a patient with psoriasis vulgaris

Plaque psoriasis is a chronic debilitating condition, and biologic agents that inhibit tumor necrosis factor-α (TNF-α) are widely employed in management of the condition. Notwithstanding, several paradoxical adverse reactions have been reported with TNF-α inhibitors, including vasculitis, vitiligo, alopecia areata, sarcoidosis and other granulomatous diseases. Herein, we report the case of a 63-year-old man who developed vitiligo while on therapy with adalimumab following failure of conventional agents for plaque psoriasis. After discontinuation of adalimumab and initiation of secukinumab, vitiligo and other psoriatic symptoms gradually resolved. After 1 year of treatment, only small plaque areas were present in the flexor site with complete remission in the extensor area along with near complete resolution of depigmented areas. In this case of possible adalimumab-induced vitiligo in a patient with plaque psoriasis, secukinumab resolved both the symptoms of psoriasis and the likely adalimumab-related vitiligo.