Cytomegalovirus, an mRNA vaccine to prevent congenital infections
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In the Western world, cytomegalovirus (CMV) is the first cause of congenital infection, i.e. infection transmissible from mother to child, although it is much less known than other potentially dangerous infectious pathologies if contracted during pregnancy (especially for the unborn child, such as rubella or toxoplasmosis). There is currently no vaccine against this virus, although several are under study. One, in particular, has reached phase three of the experimentation – the international multicenter study CMVictory – and is aimed precisely at preventing infection in the uterus. CMVictory is a double-blind randomized study involving several Australian, Japanese, US, Israeli and European centres, two of which are Italian: the San Martino Polyclinic Hospital in Genoa and the IRCCS San Gerardo dei Tintori Foundation in Monza (which is the coordinator center for our country).
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An infection often asymptomatic, but not for everyone
According to the Istituto Superiore di Sanità (ISS), it is estimated that, in industrialized countries, 40 to 80% of the population is infected by the cytomegalovirus during their lifetime. In Italy, in fact, about 70-80% of the adult population is positive for anti-CMV antibodies. Transmission occurs through the exchange of bodily fluids such as saliva, blood, urine, seminal fluid, vaginal secretions, breast milk and, during pregnancy, also through the placenta. Once you have been infected, CMV remains latent, ie it is never completely eliminated from the body and can be reactivated in the event of a lowering of the immune system.
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There are also different strains of this virus, so you can get infected several times in your life. In the latter two cases (reactivation of the virus or re-infection with a different strain) we speak of secondary infection, while we speak of primary infection in the others. The infection is in most cases asymptomatic, but can be dangerous in immunocompromised people and in children under two years of age, in whom CMV can cause even permanent damage to many different organs, including eyes, lungs, digestive system and central nervous system.
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The risks for children
In the case of infection of the fetus during pregnancy, the unborn child risks developing psychomotor retardation, visual or hearing impairment, microcephaly, epilepsy. Some children develop symptoms of infection acquired in utero even months or years after birth: in these cases the diagnosis is not always immediate, so it is probable that the number of cases of congenital infection is underestimated. “Cytomegalovirus infection is in fact the first cause of deafness of non-genetic origin in children, and one of the first for the development of neurological disorders, always excluding genetic causes – they explain to Health Anna Locatelli And Sara Ornaghirespectively director and research doctor of the Complex Structure of Obstetrics of San Gerardo di Monza”.
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The risk of transmitting the infection to the fetus, the two experts continue, is greater in cases of primary infection, i.e. when the woman contracts CMV infection for the first time during pregnancy. However, the latest studies show that, once the infection is transmitted, the risk for the unborn child of developing symptomatic disease is equivalent, whether the mother has primary or non-primary infection. Congenital fetal infections and those that occur during or shortly after birth (for example during the breastfeeding phase) are particularly dangerous, which is why the CMVictory study is focused on developing a vaccine that is able to prevent them.
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The CMVictory study
“The pandemic has greatly speeded up the study and development of a vaccine against CMV, which until recently seemed unthinkable to obtain, at least in a short time, due to the existence of many different strains”, says Locatelli. It is an mRNA vaccine, meaning that it uses the same technology as the vaccines that have been developed against Sars-Cov-2. “Phase 1 and 2 studies – continues Ornaghi – have shown that the vaccine is able to generate a good antibody response that lasts over time”.
I already had rubella as a child and was also vaccinated shortly after. Do I have to get the vaccine again in anticipation of a pregnancy?
The phase 3 CMVictory study will be based on two groups of participants aged between 16 and 40 who are in close contact with young children (which is one of the main risk factors for infection): a the first group will be made up of women who have already contracted CMV infection in the past, the second of women who do not have antibodies against this virus. “The enrollment of women who test positive for antibodies against CMV has already been completed”, explains Ornaghi. “On the other hand, the enrollment of women who have never contracted the infection is underway: around 2,500 are missing internationally”.
Also focus on prevention
“While waiting for a vaccine against CMV to be available – recalls Locatelli – it is also important to promote and disseminate good standards for the prevention of infection in pregnant women”. The two experts in fact explain that, while there is a popular culture The prevention of other diseases that can be dangerous if contracted during pregnancy is not widely used, but CMV is not.For example, pregnant women who are already mothers of other small children should observe some important hygiene rules, such as wash your hands thoroughly after changing the diaper and avoid exchanging food (and therefore saliva) with the young child. “The hope – concludes Locatelli – is that the possible approval of a vaccine against this virus could have the double effect to reduce infections and to promote knowledge on this issue”.
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