The durability of circulating neutralizing antibody (nAb) responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and their boosting by vaccination remains to be defined. We show that outpatient and hospitalized SARS-CoV-2 seropositive individuals mount a robust neutralizing antibody (nAb) response that peaks at days 23 and 27 post-symptom onset, respectively. Although nAb titers remained higher in hospitalized patients, both study groups showed long-lasting nAb responses that can persist for up to 12 months after natural infection. These nAb responses in previously seropositive individuals can be significantly boosted through immunization with two doses of the CoronaVac (Sinovac) or one dose of the BNT162b2 (BioNTech/Pfizer) vaccines, suggesting a substantial induction of B cell memory responses. Noteworthy, three obese previously seropositive individuals failed to mount a booster response upon vaccination, warranting further studies in this population. Immunization of naïve individuals with two doses of the CoronaVac vaccine or one dose of the BNT162b2 vaccine elicited similar levels of nAbs compared to seropositive individuals 4.2 to 13.3 months post-infection with SARS-CoV-2. Thus, this preliminary evidence suggests that both, seropositive and naïve individuals, require two doses of CoronaVac to ensure the induction of robust nAb titers.

A significant gap in exposure data for most livestock and zoonotic pathogens is common for several Latin America deer species. This study examined the seroprevalence against 13 pathogens in 164 wild and captive southern pudu from Chile between 2011 and 2023. Livestock and zoonotic pathogen antibodies were detected in 22 of 109 wild pudus (20.18%; 95% CI: 13.34–29.18) and 17 of 55 captive pudus (30.91%; 95% CI: 19.52–44.96), including five Leptospira interrogans serovars (15.38% and 10.71%), Toxoplasma gondii (8.57% and 37.50%), Chlamydia abortus (3.03% and 12.82%), Neospora caninum (0.00% and 9.52%), and Pestivirus (8.00% and 6.67%). Risk factors were detected for Leptospira spp., showing that fawn pudu have statistically significantly higher risk of positivity than adults. In the case of T. gondii, pudu living in “free-range” have a lower risk of being positive for this parasite. In under-human-care pudu, a Pestivirus outbreak is the most strongly suspected as the cause of abortions in a zoo in the past. This study presents the first evidence of Chlamydia abortus in wildlife in South America and exposure to T. gondii, L. interrogans, and N. caninum in wild ungulate species in Chile. High seroprevalence of livestock pathogens such as Pestivirus and Leptospira Hardjo in wild animals suggests a livestock transmission in Chilean template forest.

SARS-CoV-2 infection susceptibility in dogs and cats has been documented, with identified risk factors contributing to transmission dynamics. Understanding viral prevalence and the evolution of emerging variants across pandemic waves can clarify the potential role of pets as reservoirs. This study evaluated 3298 serum samples (1921 dogs, 1377 cats) collected from 2020 to 2024. Samples were analyzed using ELISA and viral neutralization assays, revealing a positivity rate of 2.7%. We assessed neutralizing antibody titers (nAbs) against the Wuhan-Hu-1 and Omicron BA.1 strains, finding higher titers in felines compared to canines. A marked reduction in samples exceeding the detection limit was observed after November 2022. Longitudinal data from up to 30 months in a dog and 15 months in two cats demonstrated sustained antibody responses, with increased nAb titers in 7 of 14 monitored animals. Multivariable logistic regression of 275 samples indicated that a pet’s vaccination status was associated with an increased risk of infection, while spring season, the owner’s number of COVID-19 vaccinations, and the owner’s vaccination status were protective factors. These results emphasize the significance of vaccination strategies for both human and animal health, supporting the One Health approach.

The SARS-CoV-2 Omicron variant and its sublineages continue to cause COVID-19-associated pediatric hospitalizations, severe disease, and death globally. BNT162b2 and CoronaVac are the main vaccines used in Chile. Much less is known about the Wuhan-Hu-1 strain-based vaccines in the pediatric population compared to adults. Given the worldwide need for booster vaccinations to stimulate the immune response against new Omicron variants of SARS-CoV-2, we characterized the humoral and cellular immune response against Omicron variant BA.1 in a pediatric cohort aged 10 to 16 years who received heterologous vaccination based on two doses of CoronaVac, two doses of CoronaVac (2x) plus one booster dose of BNT162b2 [CoronaVac(2x) + BNT162b2 (1x)], two doses of CoronaVac plus two booster doses of BNT162b2 [CoronaVac(2x) + BNT162b2 (2x)], and three doses of BNT162b2. We observed that the [CoronaVac(2x) + BNT162b2 (2x)] vaccination showed higher anti-S1 and neutralizing antibody titers and CD4 and CD8 T cell immunity specific to the Omicron variant compared to immunization with two doses of CoronaVac alone. Furthermore, from all groups tested, immunity against Omicron was highest in individuals who received three doses of BNT162b2. We conclude that booster vaccination with BNT162b2, compared to two doses of CoronaVac alone, induces a greater protective immunity.

Hantaviruses are segmented negative-sense RNA viruses that package their genome into helical ribonucleocapsids, by oligomerization of the nucleocapsid (N) protein along the viral RNA. Upon transmission to humans, hantaviruses can cause severe disease characterized by increased vascular permeability in the microvasculature, a key driver of pathogenesis. In patients and rodent reservoirs, robust and persistent antibody responses against the nucleocapsid (N) protein are consistently observed. Here we investigated whether the hantavirus N protein, described as a strictly intracellular protein, is released into the extracellular environment during viral infection. By using diverse experimental approaches, we demonstrate that in cells infected with Andes virus (ANDV) or the non-pathogenic Tula virus (TULV), the N protein localizes on the plasma membrane. Transfection experiments further revealed that the surface localization of N proteins from Murine , Arvicoline , Neotomine and Sigmodontine rodent-reservoir-associated hantaviruses did not require co-expression of other viral proteins indicating that its trafficking to the cell surface is mediated by a mechanism distinct from canonical virion assembly pathways. Moreover, we show that the N protein is secreted from cells into the extracellular milieu and is further transferred to neighboring cells. Interestingly, despite being present on the cell surface and secreted into the extracellular media, the TULV N protein transfer of the N protein to neighboring cells was significantly lower compared to that of ANDV N protein. The extracellular presence of hantavirus N proteins, and likely also from other clinically-relevant bunyaviruses, unveils new possible functions of the protein during the viral infection cycle, which is likely related to immune responses, immune modulation and viral pathogenesis.