Publication date: Jul 23, 2025

We have previously reported that microorganism-associated antigens (MAAs) share high sequence and conformational homology with tumor-associated antigens (TAAs) as well as T cells cross-react with homologous MAA/TAA pairs. More recently, we have also shown that the SARS-CoV-2 preventive vaccine, besides the humoral response, is able to elicit also a T cell response which cross-react with homologous TAAs. In the present study we analyzed the mandatory pediatric vaccines, namely the hexavalent vaccine (Diphtheria, Tetanus, Pertussis (whooping cough), Polio, Haemophilus influenzae type b (Hib), Hepatitis B) and the MMR (measles, mumps and rubella), and the chickenpox vaccine. MHC class I epitopes (9 mers) from each of these vaccines were predicted for the most frequent 12 HLA A and B alleles. Overall, 3177 strong binders (SBs) were identified and the most frequently associated allele is the HLA-A*02:01. Of these, 397 are predicted for the hexavalent vaccine and 571 in the MMR vaccine. A molecular mimicry with 59 SBs derived from cellular proteins has been identified and 13 of these proteins are significantly overexpressed in several human cancers. All these results strongly suggest that the mandatory pediatric vaccinations may potentially elicit a CD8 T cell response against several microbial epitopes in individuals with different genetic background. Such microbial epitopes show high homology with epitopes from cellular proteins overexpressed in multiple cancer types. Therefore, a potential anti-microbial CD8 T cell response may cross-react against cancer cells. This would imply that the pediatric vaccinations may be a preventive measure against both microbial infections and a broad spectrum of tumors. A large-scale immune-epidemiological study will be needed to confirm the proposed suggestive results.

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