Dengue Virus-Specific Antibodies Enhance Brazilian Zika Virus Infection.

Anti-Flavivirus antibodies are highly cross-reactive and may facilitate Zika virus (ZIKV) infection through the antibody-dependent enhancement (ADE) mechanism. We demonstrate that dengue-specific antibodies enhance the infection of a primary Brazilian ZIKV isolate in a FcγRII-expressing K562 cell line. In addition, we demonstrate that serum samples from dengue-immune pregnant women enhanced ZIKV infection. These findings highlight the need for epidemiological studies and animal models to further confirm the role of ADE in the development of congenital and neurological complications associated with ZIKV infections.

First reported cases of SARS-CoV-2 infection in pets in São Paulo, Brazil.

Background and Aim: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the global coronavirus pandemic (COVID-19) in humans in 2019. Although SARS-CoV-2 infection is primarily asymptomatic and transitory in companion animals, the role of these animals in the life cycle of the virus remains unclear. This study aimed to survey the first SARS-CoV-2 infection cases in pets, including a dog and three cats in São Paulo, Brazil. Materials and Methods: We invited COVID-19-positive pet owners to participate in the survey and obtained nasal, oropharyngeal, and rectal swab samples from their pets. These samples were placed in vials and subjected to a real-time quantitative polymerase chain reaction. In addition, the owners answered an epidemiological questionnaire, and the pets underwent clinical examination and monitoring. Results: Out of 49 sampled pets, 3/19 (15.8%) cats and 1/30 (3.3%) dogs tested positive, with wide variations in viral loads. Despite the limitations of size and non-randomized sampling, our results showed that cats are more susceptible than dogs to SARS-CoV-2 infection, presenting a cat: dog ratio of 4.8: 1. Only one cat presented mild and transitory respiratory symptoms. Conclusion: Although SARS-CoV-2 infection was detected in pets in the largest South American city and the COVID-19 epicenter at the time, these first detected pet cases displayed either none or mild clinical signs.

Frequent Infection of Cats With SARS-CoV-2 Irrespective of Pre-Existing Enzootic Coronavirus Immunity, Brazil 2020.

Carnivores such as cats and minks are highly susceptible to SARS-CoV-2. Brazil is a global COVID-19 hot spot and several cases of human-to-cat transmission have been documented. We investigated the spread of SARS-CoV-2 by testing 547 domestic cats sampled between July-November 2020 from seven states in southern, southeastern, and northeastern Brazil. Moreover, we investigated whether immune responses elicited by enzootic coronaviruses affect SARS-CoV-2 infection in cats. We found infection with significantly higher neutralizing antibody titers against the Gamma variant of concern, endemic in Brazil during 2020, than against an early SARS-CoV-2 B.1 isolate (p<0.0001), validating the use of Gamma for further testing. The overall SARS-CoV-2 seroprevalence in Brazilian cats during late 2020 validated by plaque reduction neutralization test (PRNT90) was 7.3% (95% CI, 5.3-9.8). There was no significant difference in SARS-CoV-2 seroprevalence in cats between Brazilian states, suggesting homogeneous infection levels ranging from 4.6% (95% CI, 2.2-8.4) to 11.4% (95% CI, 6.7-17.4; p=0.4438). Seroprevalence of the prototypic cat coronavirus Feline coronavirus (FCoV) in a PRNT90 was high at 33.3% (95% CI, 24.9-42.5) and seroprevalence of Bovine coronavirus (BCoV) was low at 1.7% (95% CI, 0.2-5.9) in a PRNT90. Neutralizing antibody titers were significantly lower for FCoV than for SARS-CoV-2 (p=0.0001), consistent with relatively more recent infection of cats with SARS-CoV-2. Neither the magnitude of SARS-CoV-2 antibody titers (p=0.6390), nor SARS-CoV-2 infection status were affected by FCoV serostatus (p=0.8863). Our data suggest that pre-existing immunity against enzootic coronaviruses neither prevents, nor enhances SARS-CoV-2 infection in cats. High SARS-CoV-2 seroprevalence already during the first year of the pandemic substantiates frequent infection of domestic cats and raises concerns on potential SARS-CoV-2 mutations escaping human immunity upon spillback.