SARS-CoV-2 infectivity and antigenic evasion: spotlight on isolated Omicron sub-lineages.

Since the SARS-CoV-2 outbreak in 2019, a diversity of viral genomic variants has emerged and spread globally due to increased transmissibility, pathogenicity, and immune evasion. By the first trimester of 2023 in Chile, as in most countries, BQ and XBB were the predominant circulating sub-lineages of Omicron. The molecular and antigenic characteristics of these variants have been mainly determined using non-authentic spike pseudoviruses, which is often described as a limitation. Additionally, few comparative studies using isolates from recent Omicron sub-lineages have been conducted. In this study, we isolated SARS-CoV-2 variants from clinical samples, including the ancestral B.1.1, Delta, Omicron BA.1, and sub-lineages of BA.2 and BA.5. We assessed their infectivity through cell culture infections and their antibody evasion using neutralization assays. We observed variations in viral plaque size, cell morphology, and cytotoxicity upon infection in Vero E6-TMPRSS2 cells for each variant compared to the ancestral B.1.1 virus. BA.2-derived sub-variants, such as XBB.1.5, showed attenuated viral replication, while BA.5-derived variants, such as BQ.1.1, exhibited replication rates similar to the ancestral SARS-CoV-2 virus. Similar trends were observed in intestinal Caco-2 cells, except for Delta. Antibody neutralization experiments using sera from individuals infected during the first COVID-19 wave (FWI) showed a consistent but moderate reduction in neutralization against Omicron sub-lineages. Interestingly, despite being less prevalent, BQ.1.1 showed a 6.1-fold greater escape from neutralization than XBB.1.5. Neutralization patterns were similar when tested against sera from individuals vaccinated with 3xBNT162b2 (PPP) or Coronavac-Coronavac-BNT162b2 (CCP) schedules. However, CCP sera showed 2.3-fold higher neutralization against XBB.1.5 than FWI and PPP sera. This study provides new insights into the differences between BA.2 and BA.5-derived variants, leading to their eventual outcompetition. Our analysis offers important evidence regarding the balance between infectivity and antigenic escape that drives the evolution of second-generation SARS-CoV-2 variants in the population.

Meningitis tuberculosa: un desafío diagnóstico en pediatría / Tuberculous meningitis: diagnostic challenge in pediatrics

Resumen La meningitis por Mycobacterium tuberculosis es infrecuente en pediatría y su diagnóstico definitivo representa un desafío clínico. Presentamos el caso de un lactante de dos años, que presentó un cuadro de meningitis crónica. Se logró el diagnóstico tras la sospecha imagenológica y la confirmación tras la búsqueda seriada del complejo M. tuberculosis por RPC en LCR y en biopsia de tejido cerebral. A pesar de sus complicaciones, el paciente respondió favorablemente al tratamiento antituberculoso. En Chile, la tuberculosis es infrecuente en niños y los síntomas son generalmente inespecíficos. Los hallazgos en RM cerebral asociados a alteraciones del LCR permiten sospechar el compromiso meníngeo precozmente. Se recomienda iniciar el tratamiento antituberculoso empírico ante la sospecha, ya que mejora el pronóstico. A pesar de los avances diagnósticos y terapéuticos, la meningitis tuberculosa sigue teniendo una alta tasa de complicaciones y un pronóstico ominoso.

Abstract Mycobacterium tuberculosis meningitis is rare in the pediatric population and its definitive diagnosis represents a clinical challenge. We present the case of a 2-year-old infant with chronic meningitis. Diagnosis was accomplished by suggestive radiological findings and serial search for M. tuberculosis complex by real-time polymerase chain reaction (qPCR) in cerebrospinal fluid (CSF) and in brain tissue. Despite the complications, the patient evolved favorably with the tuberculosis treatment. In Chile, tuberculosis is a rare disease in children and symptoms are generally nonspecific. Brain MRI findings associated with CSF alterations allow early suspicion of MTBC. Start of empirical antituberculosis treatment upon suspicion is recommended given it is associated with better prognosis. Despite diagnostic and therapeutic advances, MTBC continues to have a high complication rate and an ominous prognosis.

Insights into neutralizing antibody responses in individuals exposed to SARS-CoV-2 in Chile.

Chile has one of the worst numbers worldwide in terms of SARS-CoV-2 positive cases and COVID-19-related deaths per million inhabitants; thus, characterization of neutralizing antibody (NAb) responses in the general population is critical to understanding of immunity at the local level. Given our inability to perform massive classical neutralization assays due to the scarce availability of BSL-3 facilities in the country, we developed and fully characterized an HIV-based SARS-CoV-2 pseudotype, which was used in a 96-well plate format to investigate NAb responses in samples from individuals exposed to SARS-CoV-2 or treated with convalescent plasma. We also identified samples with decreased or enhanced neutralization activity against the D614G spike variant compared with the wild type, indicating the relevance of this variant in host immunity. The data presented here represent the first insights into NAb responses in individuals from Chile, serving as a guide for future studies in the country.

Infección atípica y neurorretinitis por Bartonella henselae en una unidad de hospitalización pediátrica: comunicación de tres casos / Bartonella henselae with atypical infection and neuroretinitis in a pediatric unit: report of three cases

Resumen Bartonella henselae es el agente etiológico de la enfermedad por arañazo de gato (EAG), infección endémica en Chile. Típicamente se presenta como una linfadenopatía regional autolimitada y menos frecuentemente con compromiso sistémico y manifestaciones extraganglionares: en hígado, bazo, hueso, ojo, entre otros. Se presentan tres casos de infección atípica por Bartonella henselae en las que se evidenció compromiso ocular, manifestado como una neurorretinitis. Esta revisión destaca la importancia de la búsqueda activa de complicaciones oculares en pacientes con compromiso sistémico por Bartonella henselae, implicando un cambio en el tratamiento y pronóstico de la enfermedad.

Abstract Bartonella henselae is cat scratch disease's etiological agent, which is considered an endemic infection in Chile. It typically presents as a self-limited regional lymphadenopathy and less frequently with systemic involvement and extranodal or atypical manifestations: hepatosplenic, ocular or musculoskeletal involvement, among others. We present three cases of atypical cat scratch disease with ocular compromise, as neurorretinitis. This review highlights the importance of the active search for ocular complications in patients with disseminated cat scratch disease, leading to possible change in treatment and prognosis of the disease.

[Bartonella henselae with atypical infection and neuroretinitis in a pediatric unit: report of three cases]. / Infección atípica y neurorretinitis por Bartonella henselae en una unidad de hospitalización pediátrica: comunicación de tres casos.

Bartonella henselae is cat scratch disease's etiological agent, which is considered an endemic infection in Chile. It typically presents as a self-limited regional lymphadenopathy and less frequently with systemic involvement and extranodal or atypical manifestations: hepatosplenic, ocular or musculoskeletal involvement, among others. We present three cases of atypical cat scratch disease with ocular compromise, as neurorretinitis. This review highlights the importance of the active search for ocular complications in patients with disseminated cat scratch disease, leading to possible change in treatment and prognosis of the disease.