Haemovigilance survey and screening strategy for arthropod-borne viruses in blood donors from Argentina

Arthropod-borne viruses (arboviruses) count among emerging infections, which represent a major challenge for transfusion safety worldwide. To assess the risk of arboviruses-transmission by transfusion (ATT), we performed a survey to evaluate the potential threat for transfusion safety. Samples were retrospectively and randomly collected from donors who donated during the peak of dengue incidence in Cordoba (years: 2016 and 2019-2022). A cost-efficient strategy for molecular screening was implemented with a nucleic acid test (NAT) configured with Flavivirus and Alphavirus-universal degenerated primers targeting conserved gene regions. Besides, we evaluated the neutralizing antibody (NAb) prevalence by plaque reduction neutralization test (PRNT). A total of 1438 samples were collected. Among the NAT-screened samples, one resulted positive for Flavivirus detection. Subsequent sequencing of the PCR product revealed Saint Louis Encephalitis Virus (SLEV) infection (GeneBank accession number OR236721). NAb prevalence was 2.95% for anti-Dengue, 9.94% anti-SLEV, 1.09% anti-West Nile Virus, and 0% anti-Chikungunya. One of the NAb-positive samples also resulted positive for IgM against SLEV but negative by ARN detection. This is the first haemovigilance study developed in Argentina that evaluates the potential risk of ATT and the first research to determine the prevalence of NAb against Flavivirus through PNRT to avoid possible cross-reactions between Ab against Flavivirus. Herein, the finding of one SLEV-viremic donor and the detection of anti-SLEV IgM in a different donor demonstrated a potential threat for transfusion safety and emphasized the need for increased vigilance and proactive measures to ensure the safety of blood supplies.

Neutralizing response elicited by homologous and heterologous prime booster vaccination against ancestral SARS-CoV-2 B.1, P.1, C.37 and B.1.617.2 variants

Heterologous Covid-19 vaccination strategies arose due to interruption of vaccination programs plus delay and shortage of vaccine supplies. We analysed neutralizing response against ancestral SARS-CoV-2 B.1 and P.1, C.37 and B.1.67.2 variants elicited by 16 homologous and heterologous protocols combining Gam-COVID-Vac, ChAdOx1-S, Ad5-nCorV, BBIBP-CorV and mRNA-1273 vaccines. Homologous mRNA-1273 and heterologous schemes of a non-replicative viral vector/inactivated virus-based vaccine combined with mRNA-1273 induced significantly broader and greater neutralizing antibody-response. Moreover, serum from participants vaccinated with combinations of ChAdOx1-S/Ad5-nCorV and BBIBP-CorV/non-replicative viral vector-based vaccines showed higher or equivalent neutralizing response compared to homologous protocols, pointing them as good alternative platforms. BBIBP-CorV used as second dose exhibited significantly lower neutralizing response compared to other protocols, demonstrating that it should not be recommended as second dose. The information provided herein is valuable to redesign vaccination strategies, especially for low-income countries that still struggle with low percentages of immunized populations and vaccine supply shortage.

Evaluation of the Gam-COVID-Vac and vaccine-induced neutralizing response against SARS-CoV-2 lineage P.1 variant in an Argentinean cohort

We evaluated humoral immune-response elicited by Sputnik-V by measuring anti-Spike (S) IgG antibodies (Abs) and neutralizing antibodies (NAb) prior to, 14 and 42 days after-vaccination. The safety and disease rates among vaccinated individuals were also evaluated. Since SARS-CoV-2 lineage P.1 is rapidly spreading in Argentina, virus-neutralizing activity of Sputnik-V-elicited and infection-elicited NAb faced to P.1 were also assessed. A total of 285 participants were recruited; all reported good tolerance, without any severe adverse event. Nine COVID-19 cases were confirmed in fully vaccinated individuals and viable P.1 variant was successfully isolated from one of them. At day 42, 99.65% of the individuals had anti-S IgG; however, 23.15% had not detectable NAbs. Significantly higher neutralization potency against WT compared to P.1 (p < 0·001) was observed. Some samples failed to neutralize P.1, mainly among vaccinated-naїve subjects; however, no significant differences were observed among previously infected-vaccinated individuals. Our results corroborated that Sputnik-V is safe and induces an efficient humoral immune response, although not all immunized subjects develop Nabs. Herein, we show for the first time, evidence of infectious SARS-CoV-2 shedding from Sputnik-V fully vaccinated individuals, by the isolation of viable virus from the nasopharyngeal swab of one participant of our study, 139 days after receiving the second dose. Thereby, we provide evidence indicating that the vaccine might avoid severe forms of COVID-19 but does not prevent infection nor prevents transmission from a fully vaccinated individual.

Genomic Characterization and Seroprevalence Studies on Alphaviruses in Uruguay

Alphaviruses (Togaviridae) are arboviruses frequently associated with emerging infectious diseases. In this study, we aimed to investigate the presence of alphaviruses in Uruguay by detecting the viral genome in mosquitoes and neutralizing antibodies in equines. A total of 3,575 mosquitoes were analyzed for alphavirus genome detection. Serologic studies were performed on 425 horse sera by plaque reduction neutralization test (PRNT80) against Venezuelan equine encephalitis virus (VEEV) subtype IAB, Pixuna virus (PIXV), Rio Negro virus (RNV), western equine encephalitis virus (WEEV), and Madariaga virus (MADV). Mosquitoes belonging to six genera were captured and 82.9% were identified as Culex pipiens. Two Cx. pipiens pools collected in Fray Bentos and Las Toscas localities were alphavirus positive, and phylogenetic analyses showed that the sequences grouped into two different clusters: the lineage I of eastern equine encephalitis virus and RNV (VEEV complex), respectively. Plaque reduction neutralization test assays showed antibodies against strains of the VEEV complex, MADV, and WEEV. Rio Negro virus was the most geographically widespread virus, showing higher seroprevalences (up to 20%). Seroprevalences against VEEV IAB ranged between 4.6% and 13%; antibodies against PIXV, WEEV, and MADV were less frequent (3-4%). In conclusion, RNV exhibited the highest seroprevalence in horses, a wide geographical distribution, and viral genome was detected in Cx. pipiens mosquitoes. Madariaga virus had a low seroprevalence in equines, but an epizootic lineage typical of North America was detected in Cx. pipiens mosquitoes. Taken together, our results show that alphaviruses are present in Uruguay with variable occurrence and geographical distribution being a potential threat for human and equine health.

Alphaviruses: Serological Evidence of Human Infection in Paraguay (2012-2013)

INTRODUCTION

Alphaviruses can produce febrile illness and encephalitis in dead-end hosts such as horses and humans. Within this genus, the Venezuelan Equine Encephalitis virus (VEEV) complex includes pathogenic epizootic subtypes and enzootic subtypes that are not pathogenic in horses (except subtype IE, Mexican strains), although they can cause febrile symptoms in humans. The Rio Negro virus (RNV-VEEV subtype VI) circulates in Argentina, where it was associated with undifferentiated febrile illness. Mayaro (MAYV) and Una (UNAV) viruses belong to a different group, the Semliki Forest virus complex, with confirmed circulation.

OBJECTIVE

The present study aimed to determine RNV, MAYV, and UNAV seroprevalences by plaque reduction neutralization test in 652 samples of Paraguayan individuals mainly from the Central Department, between years 2012 and 2013.

METHODS

Samples with antibodies titer >1:20 against RNV were also tested for Mosso das Pedras-subtype IF, subtype IAB, and Pixuna (PIXV)-subtype IV viruses that belongs to VEEV antigenic complex.

RESULTS

The overall seroprevalence of RNV was 3.83%, and for UNAV it was 0.46%, and no neutralizing antibodies were detected against MAYV in the studied population. Two of the twenty-seven heterotypic samples were positive for PIXV. The 50.1% of neutralizing antibody titers against RNV were high (equal to or greater than 1/640), suggesting recent infections. The effect of age on the prevalence of RNV was negligible.

CONCLUSIONS

These results bring new information about neglected alphaviruses in South America, and these data will serve as the basis for future studies of seroprevalence of other VEEV, and studies to search potential hosts and vectors of these viruses in the region.

Tissue tropism of Saint Louis encephalitis virus: Histopathology triggered by epidemic and non-epidemic strains isolated in Argentina

Saint Louis encephalitis virus (SLEV) reemerged in South America, and caused encephalitis outbreaks at the beginning of the 21st century. To enhance our knowledge about SLEV virulence, we performed comparative pathogenesis studies in Swiss albino mice inoculated with two different variants, the epidemic strain CbaAr-4005 and the non-epidemic strain CorAn-9275. Only the infection of mice with SLEV strain CbaAr-4005 resulted in high viremia, invasion of peripheral tissues including the lungs, kidney, and spleen, and viral neuroinvasion. This was associated with inflammatory pathology in the lungs, spleen, and brain as well as morbidity and mortality. In contrast, neither signs of desease nor viral replication were observed in mice infected with strain CorAn-9275. Interestingly, important loss of B cells and development of altered germinal centers (GC) were detected in the spleen of mice infected with strain CbaAr-4005, whereas mice infected with SLEV CorAn-9275 developed prominent GC with conserved follicular architecture, and neutralizing antibodies.

Virulence variation among epidemic and non-epidemic strains of Saint Louis encephalitis virus circulating in Argentina

Saint Louis encephalitis virus caused an outbreak of febrile illness and encephalitis cases in Córdoba, Argentina, in 2005. During this outbreak, the strain CbaAr-4005 was isolated from Culex quinquefasciatus mosquitoes. We hypothesised that this epidemic variant would be more virulent in a mouse model than two other non-epidemic strains (78V-6507 and CorAn-9275) isolated under different epidemiological conditions. To test this hypothesis, we performed a biological characterisation in a murine model, including mortality, morbidity and infection percentages and lethal infection indices using the three strains. Mice were separated into age groups (7, 10 and 21-day-old mice) and analysed after infection. The strain CbaAr-4005 was the most infective and lethal of the three variants, whereas the other two strains exhibited a decreasing mortality percentage with increasing animal age. The strain CbaAr-4005 produced the highest morbidity percentages and no significant differences among age groups were observed. The epidemic strain caused signs of illness in all inoculated animals and showed narrower ranges from the onset of symptoms than the other strains. CbaAr-4005 was the most virulent for Swiss albino mice. Our results highlight the importance of performing biological characterisations of arbovirus strains likely to be responsible for emerging or reemerging human diseases.

Detection of Orthobunyavirus in mosquitoes collected in Argentina

Bunyamwera virus (BUNV) (Bunyaviridae, genus Orthobunyavirus, serogroup Bunyamwera) is considered an emerging pathogen for humans and animals in American countries. The CbaAr-426 strain of BUNV was recovered from mosquitoes Ochlerotatus albifasciatus (Diptera: Culicidae) collected in Córdoba province (Argentina), where serological studies detected high seroprevalences in humans and animals. Molecular detection of Orthobunyavirus was performed in mosquitoes collected in Córdoba province. Seventeen mosquito pools of Oc. albifasciatus, Ochlerotatus scapularis and Culex quinquefasciatus (Diptera: Culicidae) showed positive results; four of these positive pools, all of Oc. scapularis, were sequenced. All amplicons grouped with BUNV in the Bunyamwera serogroup. The findings highlight the circulation of BUNV in Córdoba province and represent the first report of BUNV-infected Oc. scapularis mosquitoes in Argentina.