Leveraging Beneficial Off-Target Effects of Live-Attenuated Rotavirus Vaccines

Genetic diversity and evolution of G12P[6] DS-1-like and G12P[9] AU-1-like Rotavirus strains in Brazil

In the early 2000s, the global emergence of rotavirus (RVA) G12P[8] genotype was noted, while G12P[6] and G12P[9] combinations remained rare in humans. This study aimed to characterize and phylogenetically analyze three Brazilian G12P[9] and four G12P[6] RVA strains from 2011 to 2020, through RT-PCR and sequencing, in order to enhance our understanding of the genetic relationship between human and animal-origin RVA strains. G12P[6] strains displayed a DS-1-like backbone, showing a distinct genetic clustering. G12P[6] IAL-R52/2020, IAL-R95/2020 and IAL-R465/2019 strains clustered with 2019 Northeastern G12P[6] Brazilian strains and a 2018 Benin strain, whereas IAL-R86/2011 strain grouped with 2010 Northern G12P[6] Brazilian strains and G2P[4] strains from the United States and Belgium. These findings suggest an African genetic ancestry and reassortments with co-circulating American strains sharing the same DS-1-like constellation. No recent zoonotic reassortment was observed, and the DS-1-like constellation detected in Brazilian G12P[6] strains does not seem to be genetically linked to globally reported intergenogroup G1/G3/G9/G8P[8] DS-1-like human strains. G12P[9] strains exhibited an AU-1-like backbone with two different genotype-lineage constellations: IAL-R566/2011 and IAL-R1151/2012 belonged to a VP3/M3.V Lineage, and IAL-R870/2013 to a VP3/M3.II Lineage, suggesting two co-circulating strains in Brazil. This genetic diversity is not observed elsewhere, and the VP3/M3.II Lineage in G12P[9] strains seems to be exclusive to Brazil, indicating its evolution within the country. All three G12P[9] AU-1-like strains were closely relate to G12P[9] strains from Paraguay (2006-2007) and Brazil (2010). Phylogenetic analysis also highlighted that all South American G12P[9] AU-1-like strains had a common origin and supports the hypothesis of their importation from Asia, with no recent introduction from globally circulating G12P[9] strains or reassortments with local G12 strains P[8] or P[6]. Notably, certain genes in the Brazilian G12P[9] AU-1-like strains share ancestry with feline/canine RVAs (VP3/M3.II, NSP4/E3.IV and NSP2/N3.II), whereas NSP1/A3.VI likely originated from artiodactyls, suggesting a history of zoonotic transmission with human strains. This genomic data adds understanding to the molecular epidemiology of G12P[6] and G12P[9] RVA strains in Brazil, offering insights into their genetic diversity and evolution.

A retrospective nationwide register-based study to evaluate the non-specific effects of first MMR vaccination among children in Finland

BACKGROUND

According to earlier studies, live vaccines like measles-mumps-rubella (MMR) vaccine could reduce also other infections than only the infections they are targeted against. This non-specific effect has been seen especially in studies in low-income countries and results from high-income countries have not been unambiguous. In 2011 Finland changed the recommended schedule for the first MMR vaccination from 18 months to 12 months of age. This change created a natural experiment for evaluating the potential non-specific effects.

METHODS

This is a retrospective nationwide register-based cohort study of Finnish children born between 2008 and 2012. Children were divided into two cohorts by age at MMR vaccination: children administered early MMR vaccination (11 through 12 months of age) and late MMR vaccination (18 through 19 months of age). Morbidity was evaluated during the main follow-up period (from 13 to 17 months of age) and before any MMR vaccination (3 to 10 months) and after all were vaccinated with MMR (20 to 35 months) as control follow-up periods. We analyzed all infections and did additional analyzes for urinary tract infections (UTI) and bronchitis. Injuries were analyzed as a control outcome.

RESULTS

Early MMR vaccinated children (N = 79949) had fewer infections compared to late MMR vaccinated (N = 60965) during the main follow-up period. The incidence rate ratio (IRR) was 0.84 (95 % confidence interval (95 % CI) 0.81-0.87). However, similar differences were also observed during the control follow-up periods. MMR vaccinated children had less UTI in the main follow-up period (IRR 0.73, 0.60-0.89) but not in the control follow-up periods. When stratified by sex, the difference was observed among girls but not in boys.

CONCLUSION

No clear evidence was found for non-specific effects in infectious diseases morbidity. However, there could be a nonspecific effect on UTI. Confirmation is needed from other studies, especially from high-income countries.

Prospects on Repurposing a Live Attenuated Vaccine for the Control of Unrelated Infections

Live vaccines use attenuated microbes to acquire immunity against pathogens in a safe way. As live attenuated vaccines (LAVs) still maintain infectivity, the vaccination stimulates diverse immune responses by mimicking natural infection. Induction of pathogen-specific antibodies or cell-mediated cytotoxicity provides means of specific protection, but LAV can also elicit unintended off-target effects, termed non-specific effects. Such mechanisms as short-lived genetic interference and non-specific innate immune response or long-lasting trained immunity and heterologous immunity allow LAVs to develop resistance to subsequent microbial infections. Based on their safety and potential for interference, LAVs may be considered as an alternative for immediate mitigation and control of unexpected pandemic outbreaks before pathogen-specific therapeutic and prophylactic measures are deployed.