Virulence Profiles of Wild-Type, P.1 and Delta SARS-CoV-2 Variants in K18-hACE2 Transgenic Mice.

Since December 2019, the world has been experiencing the COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and we now face the emergence of several variants. We aimed to assess the differences between the wild-type (Wt) (Wuhan) strain and the P.1 (Gamma) and Delta variants using infected K18-hACE2 mice. The clinical manifestations, behavior, virus load, pulmonary capacity, and histopathological alterations were analyzed. The P.1-infected mice showed weight loss and more severe clinical manifestations of COVID-19 than the Wt and Delta-infected mice. The respiratory capacity was reduced in the P.1-infected mice compared to the other groups. Pulmonary histological findings demonstrated that a more aggressive disease was generated by the P.1 and Delta variants compared to the Wt strain of the virus. The quantification of the SARS-CoV-2 viral copies varied greatly among the infected mice although it was higher in P.1-infected mice on the day of death. Our data revealed that K18-hACE2 mice infected with the P.1 variant develop a more severe infectious disease than those infected with the other variants, despite the significant heterogeneity among the mice.

Virulence profiles of wild-type, P.1 and delta SARS-CoV-2 variants in K18-hACE2 transgenic mice

Since December 2019, the world has been experiencing the COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and we now face the emergence of several variants. We aimed to assess the differences between the wild-type (Wt) (Wuhan) strain and the P.1 (Gamma) and Delta variants using infected K18-hACE2 mice. The clinical manifestations, behavior, virus load, pulmonary capacity, and histopathological alterations were analyzed. The P.1-infected mice showed weight loss and more severe clinical manifestations of COVID-19 than the Wt and Delta-infected mice. The respiratory capacity was reduced in the P.1-infected mice compared to the other groups. Pulmonary histological findings demonstrated that a more aggressive disease was generated by the P.1 and Delta variants compared to the Wt strain of the virus. The quantification of the SARS-CoV-2 viral copies varied greatly among the infected mice although it was higher in P.1-infected mice on the day of death. Our data revealed that K18-hACE2 mice infected with the P.1 variant develop a more severe infectious disease than those infected with the other variants, despite the significant heterogeneity among the mice.

A rabies virus vampire bat variant shows increased neuroinvasiveness in mice when compared to a carnivore variant

Rabies is one of the most important zoonotic diseases and is caused by several rabies virus (RABV) variants. These variants can exhibit differences in neurovirulence, and few studies have attempted to evaluate the neuroinvasiveness of variants derived from vampire bats and wild carnivores. The aim of this study was to evaluate the neuropathogenesis of infection with two Brazilian RABV street variants (variant 3 and crab-eating fox) in mice. BALB/c mice were inoculated with RABV through the footpad, with the 50% mouse lethal dose (LD50) determined by intracranial inoculation. The morbidity of rabies in mice infected with variant 3 and the crab-eating fox strain was 100% and 50%, respectively, with an incubation period of 7 and 6 days post-inoculation (dpi), respectively. The clinical disease in mice was similar with both strains, and it was characterized initially by weight loss, ruffled fur, hunched posture, and hind limb paralysis progressing to quadriplegia and recumbency at 9 to 12 dpi. Histological lesions within the central nervous system (CNS) characterized by nonsuppurative encephalomyelitis with neuronal degeneration and necrosis were observed in mice infected with variant 3 and those infected with the crab-eating fox variant. However, lesions and the presence of RABV antigen, were more widespread within the CNS of variant-3-infected mice, whereas in crab-eating fox-variant-infected mice, RABV antigens were more restricted to caudal areas of the CNS, such as the spinal cord and brainstem. In conclusion, the results shown here demonstrate that the RABV vampire bat strain (variant 3) has a higher potential for neuroinvasiveness than the carnivore variant. (AU) i

A rabies virus vampire bat variant shows increased neuroinvasiveness in mice when compared to a carnivore variant.

Rabies is one of the most important zoonotic diseases and is caused by several rabies virus (RABV) variants. These variants can exhibit differences in neurovirulence, and few studies have attempted to evaluate the neuroinvasiveness of variants derived from vampire bats and wild carnivores. The aim of this study was to evaluate the neuropathogenesis of infection with two Brazilian RABV street variants (variant 3 and crab-eating fox) in mice. BALB/c mice were inoculated with RABV through the footpad, with the 50% mouse lethal dose (LD50) determined by intracranial inoculation. The morbidity of rabies in mice infected with variant 3 and the crab-eating fox strain was 100% and 50%, respectively, with an incubation period of 7 and 6 days post-inoculation (dpi), respectively. The clinical disease in mice was similar with both strains, and it was characterized initially by weight loss, ruffled fur, hunched posture, and hind limb paralysis progressing to quadriplegia and recumbency at 9 to 12 dpi. Histological lesions within the central nervous system (CNS) characterized by nonsuppurative encephalomyelitis with neuronal degeneration and necrosis were observed in mice infected with variant 3 and those infected with the crab-eating fox variant. However, lesions and the presence of RABV antigen, were more widespread within the CNS of variant-3-infected mice, whereas in crab-eating fox-variant-infected mice, RABV antigens were more restricted to caudal areas of the CNS, such as the spinal cord and brainstem. In conclusion, the results shown here demonstrate that the RABV vampire bat strain (variant 3) has a higher potential for neuroinvasiveness than the carnivore variant.

Análise da textura de músculos peitorais submetidos à fixação e conservação em álcool / Tenderness analysis of muscles fixed and kept in alcohol

A textura, ou maciez, pode ser avaliada pela mensuração da força necessária para ocorrer o cisalhamento das fibras musculares. Objetivou-se, nesse trabalho, a análise da textura de músculos submetidos à fixação e conservação em álcool, ao longo de um ano, mediante uso de um aparelho analisador de textura. Foram utilizados 48 peitos de frangos jovens, pesados, fixados e conservados em álcool etílico 96° GL. As análises foram realizadas após 15, 30, 90, 180 e 360 dias de conservação, além do grupo controle de músculos frescos. Os valores da força de cisalhamento dos diferentes grupos aumentaram progressivamente de 3,38 (grupo controle) até 15,31 Kgf (180 dias), caindo para 9,53 Kgf após 360 dias. Concluiu-se que quando músculos são submetidos à fixação e conservação em álcool 96° GL, ocorre diminuição da maciez, tornando-os quase cinco vezes mais rígidos ao corte após seis meses, e três vezes mais rígidos após um ano. Sugere-se que a dissecção de peças anatômicas musculares ocorra até 90 dias após fixação e conservação em álcool 96° GL ou ao redor de um ano nesse agente conservante, pois há menor rigidez tissular nesses períodos. Embora se tenha estudado o efeito do álcool na textura de tecido muscular de aves, acredita-se que, devido à grande homogeneidade tissular neste caso, tais dados possam ser extrapolados ou servir de base para estudos similares em outras espécies.

Texture, or tenderness, may be evaluated by measuring the force necessary to cause rupture of muscle fibers. The aim of this paper was to analyze the texture of muscles fixed and kept in alcohol, throughout a year, by using a texture analyzer. Forty eight poultry breasts were weighted, fixed and kept in a 96° GL ethylic alcohol solution. Analyses were performed at 15, 30, 90, 180 and 360 days of conservation, besides the one of the control group of fresh breasts. Values of shear forces of different groups increased progressively from 3.38 (control group) to 15.31 Kgf (180 days), decreasing to 9.53Kgf after 360 days. It was concluded that when muscles are fixed and kept in ethylic alcohol 96° GL the tenderness is decreased, becoming almost five times harder during the first six months and three times harder after a year. It is suggested that muscle anatomic pieces dissection occurs up to 90 days after fixation and conservation in 96° GL alcohol or around 1 year on this conservation product because there is smaller muscle stiffness in these times. Although the alcohol effect in texture of poultry muscle tissue has being studied in this paper, it is believed that, due this great tissue homogeneity, these data might be taken or being basis to similar studies in other species.