What are the challenges facing the development of effective vaccines against pathogens with hyper variable genome sequences?

“What is the point in constantly making new vaccines against the same infectious diseases?”

To answer this question, one must ask: ‘what makes for an effective vaccine?’

To explain this, it is important to recognise that a vaccine is simply an inactive form of a pathogen – the bacterium or virus which causes the disease – and the introduction of this vaccine containing the pathogen stimulates an immune response; which helps fight against the disease. At first glance, it seems an atrocious plan to purposefully sicken us, but the vaccination unsurprisingly, in actual fact, can introduce antibodies, as in passive immunity. Alternatively, they can stimulate the production of them from the individuals own immune system, in ‘active immunity’. One can easily recognise the importance of the antibodies in helping us from becoming bed-ridden or more seriously, they can save us from potentially, the verge of the ominous hazard that is, death.

Although, these antibodies work such that they each have unique binding sites, receptor-like, and the pathogen has ‘antigens’, which almost stick-out and form an identity for the pathogen. For an antibody to be work, its binding site must be of a complementary shape to the antigen, and thus they form an antibody-antigen complex. After forming this ‘complex’ by attaching to antigens, they destroy them, though the means by which they carry out this termination does vary.

However, this doesn’t address the question concerning why we need to make new vaccines for the same diseases. Thus, we need to consider antigenic variability, which is where pathogens essentially change their identity deeming them unrecognisable. This change was the change of antigens on the surface of the pathogen. The antigen no longer corresponded to the aforementioned antibodies, and the ‘complex’ could no longer be formed; thus an immune response would never arise. So, it can be established that a troublesome problem is the changing nature to some pathogens and their antigens, such as the influenza virus. Even more worrying would be the finding of a hyper variable sequence, found in the genome, which run in the nucleotides. Nucleotides are chemicals consisting of an organic base, sugar and a phosphate, and are the basic units of which the nucleic acids DNA and RNA are made. The hyper variable sequence would particularly raise concerns because they have a high rate of variation, though the rate of variation differs from one type to the next. Nonetheless, this stipulates that to form an effective measure against these sequences would also require a vaccine which is as ever varying as the pathogens in question.

Unfortunately, such a vaccine is not yet possible, at least now, within the current progress of research. There are many scientific challenges such as the variation which results in the ill-fated truth that an effective vaccine needs to be able to launch an all-encompassing response to all of the diverse strains of a pathogen with a hyper variable genome sequence. An insufficient knowledge about required immunity means that researchers face uncertainty about the parameters for ample immunity against both infection and disease, and so under current scientific knowledge, are simply unable to find a solution.

This lack of scientific knowledge isn’t helped by the social challenges which arrive in the form of ethical concerns surrounding the nature of human subject trials. It is important to acknowledge that though primate studies and computer models can be useful, they by no means provide as detailed a picture as human subject trials can. Nonetheless, in spite of the advantages, the complications appear, and one reason for the difficulties in carrying out human trials could be the volunteers being entitled to a host of treatments, not the vaccinations alone. They are to be made clear of possible adverse effects which the testing vaccination may have, and they are also to be told of the perils of seropositivity from immunisation. I am surprised to inform you that I had paid enough attention to tell you that seropositivity is merely a rather fancy word for one showing a high level of antibody. Such formalities hinder the progress of trials and consequently, the development of vaccines.

Vaccines have changed countless lives and inevitably will continue to do so in a world of advancing science. New opportunities will surface and many hurdles will be overcome; as has happened before in the past. Nonetheless, in the future, the current scientific challenges need to be overwhelmed and the development of vaccinations needs to include the production of vaccines which solve the impediments raised by the hyper variable genome sequence.

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About mLukon

I am currently undertaking my A Levels at my sixth form and am an aspiring medicine student and doctor. I would like to pursue a career in this field because it interests me and involves the intrinsic love for the sciences which I have, as well as being a challenging subject. I enjoy playing football amongst other sports, and also enjoy reading books, but manga is the genre which interests me the most.