Side effect of vaccination
Vaccination increases male fertility – proven in mice
One of the myths that makes some men avoid vaccinations is their negative impact on fertility. However, studies of the effect of vaccination on the reproduction of laboratory mice conducted by Novosibirsk scientists have found the opposite effect. These results are not only of interest to fundamental science, but also have practical applications, for example, in animal husbandry.
The resources of any living organism are limited, so it often has to find a compromise, solving the problem of what to spend them on. For example, for the fight against pathogenic microorganisms or for reproduction?
But in order to reproduce, you need to stay alive banally. Therefore, when in contact with a pathogen, the immune system usually gets priority. There is another scenario: during the breeding season, when male mammals have a higher level of secretion of the male sex hormone testosterone, their immunity is suppressed. This, for example, is "used" blood-sucking ixode mites, increasing their activity.
How do his potential partners react to the immune status of the male? It has long been shown that the activation of immune protection in a male house mouse leads to a decrease in the attractiveness of its smell for individuals of the opposite sex. Scientists learned this by observing the behavior of a female in a test, where she was offered a choice of litter from a cage of an ordinary male and an "immunized" one, who was injected with sheep erythrocytes – a standard laboratory inducer of an immune response.
And there is one important nuance here. Females on average spent less time near the litter of the male, whose scent tags signaled a possible infection. At the same time, their interest fell, first of all, in relation to individuals with a weak immune response to foreign antigens. Thus, males who actively develop specific antibodies practically do not lose their odor attractiveness and retain the chances of leaving offspring.
And what does the stronger sex "think" about in such a situation? According to one hypothesis, when the immune system recognizes an alien "invasion" into the body, it serves as a signal of an increased risk of death. The compensation mechanism is ingeniously simple – you need to multiply urgently! This assumption is supported by ethnographic observations, according to which the peoples living in the territory with a large variety and abundance of pathogens have a higher birth rate.
To test this hypothesis, scientists from the Center for Genetic Resources of the Institute of Cytology and Genetics SB RAS (Novosibirsk) we conducted an experiment on laboratory mice, choosing the vaccination procedure as a model of pathogenic load. After all, the processes that occur in the body in both of these cases are similar. Both with natural infection and with the vaccine, a foreign protein enters the body, which the immune system recognizes and begins to produce antibodies to it.
In the experiment, male mice were injected with either antigen proteins or a saline solution (control group), and then kept in pairs with females until they became pregnant.
In the first two days, the control males mated more successfully with the females, but subsequently the immunized males outperformed them in this indicator. The number of their offspring eventually turned out to be 30% more than the control ones, including due to the larger litter size. Thus, the activation of the immune system did not suppress, but, on the contrary, increased the reproductive ability of males.
Cumulative curves of fertile mating (A) and the number of offspring (B). Graphs from the article Moshkin et al., Reproductive Output in Antigen Treated Male Mice, published in the journal Clinical Research in Animal Science – VM.
Moreover, the embryos conceived by such males turned out to be slightly larger on average, and the mothers took care of them more carefully. Although female mice cannot be called particularly caring – refusal to feed offspring is not uncommon for them. Perhaps all this is also the result of the inclusion of mechanisms of population protection, and the body of the expectant mother receives from the partner, along with seminal fluid, and some information that there is a threat to the population and that the value of offspring increases.
This work opens up interesting prospects for animal husbandry. An increase in the fertility of male producers by a third is a very tempting result, and you can get it simply by combining vaccination and mating schedules. Of course, scientists cannot guarantee yet that the results obtained on mice can be fully translated into cows and pigs, but they have no doubt that vaccination can improve their performance to some extent. As for the human population, here we have something to think about…
Prepared using materials from the press service of the ICiG SB RAS (Novosibirsk)
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