Drugs and neurotransmitters

This eChapter has an introduction to pharmacology and drug nomenclature followed by a detailed discussion of routes of administration starting with oral administration (with absorption from the gastrointestinal tract, and first pass liver metabolism. This is followed by a discussion of rectal, sublingual and injection routes of administration(intravenous, intra-arterial, subcutaneous, intramuscular, intrathecal and epidural). Then the topical, pulmonary and intraosseus routes of administration are considered.

The development of an effective vaccine against Chlamydia : utilisation of a non-toxic mucosal adjuvant to generate a protective mucosal response

Chlamydia is responsible for a wide range of diseases with enormous global economic and health burden. As the majority of chlamydial infections are asymptomatic, a vaccine has greatest potential to reduce infection and disease prevalence. Protective immunity against Chlamydia requires the induction of a mucosal immune response, ideally, at the multiple sites in the body where an infection can be established. Mucosal immunity is most effectively stimulated by targeting vaccination to the epithelium, which is best accomplished by direct vaccine application to mucosal surfaces rather than by injection. The efficacy of needle-free vaccines however is reliant on a powerful adjuvant to overcome mucosal tolerance. As very few adjuvants have proven able to elicit mucosal immunity without harmful side effects, there is a need to develop non-toxic adjuvants or safer ways to administered pre-existing toxic adjuvants. In the present study we investigated the novel non-toxic mucosal adjuvant CTA1-DD. The immunogenicity of CTA1-DD was compared to our "gold-standard" mucosal adjuvant combination of cholera toxin (CT) and cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN). We also utilised different needle-free immunisation routes, intranasal (IN), sublingual (SL) and transcutaneous (TC), to stimulate the induction of immunity at multiple mucosal surfaces in the body where Chlamydia are known to infect. Moreover, administering each adjuvant by different routes may also limit the toxicity of the CT/CpG adjuvant, currently restricted from use in humans. Mice were immunised with either adjuvant together with the chlamydial major outer membrane protein (MOMP) to evaluate vaccine safety and quantify the induction of antigen-specific mucosal immune responses. The level of protection against infection and disease was also assessed in vaccinated animals following a live genital or respiratory tract infectious challenge. The non-toxic CTA1-DD was found to be safe and immunogenic when delivered via the IN route in mice, inducing a comparable mucosal response and level of protective immunity against chlamydial challenge to its toxic CT/CpG counterpart administered by the same route. The utilisation of different routes of immunisation strongly influenced the distribution of antigen-specific responses to distant mucosal surfaces and also abrogated the toxicity of CT/CpG. The CT/CpG-adjuvanted vaccine was safe when administered by the SL and TC routes and conferred partial immunity against infection and pathology in both challenge models. This protection was attributed to the induction of antigen-specific pro-inflammatory cellular responses in the lymph nodes regional to the site of infection and rather than in the spleen. Development of non-toxic adjuvants and effective ways to reduce the side effects of toxic adjuvants has profound implications for vaccine development, particularly against mucosal pathogens like Chlamydia. Interestingly, we also identified two contrasting vaccines in both infection models capable of preventing infection or pathology exclusively. This indicated that the development of pathology following an infection of vaccinated animals was independent of bacterial load and was instead the result of immunopathology, potentially driven by the adaptive immune response generated following immunisation. While both vaccines expressed high levels of interleukin (IL)-17 cytokines, the pathology protected group displayed significantly reduced expression of corresponding IL-17 receptors and hence an inhibition of signalling. This indicated that the balance of IL-17-mediated responses defines the degree of protection against infection and tissue damage generated following vaccination. This study has enabled us to better understand the immune basis of pathology and protection, necessary to design more effective vaccines.

Immunity against a Chlamydia infection and disease may be determined by a balance of IL-17 signaling

Most vaccines developed against Chlamydia using animal models provide partial protection against a genital tract infection. However, protection against the oviduct pathology associated with infertility is highly variable and often has no defining immunological correlate. When comparing two adjuvants (CTA1-DD and a combination of Cholera toxin plus CpG- oligodeoxynucleotide–CT/CpG) combined with the chlamydial major outer membrane protein (MOMP) antigen and delivered via the intranasal (IN), sublingual (SL) or transcutaneous (TC) routes, we identified two vaccine groups with contrasting outcomes following infection. SL immunization with MOMP/CTA1-DD induced a 70% reduction in the incidence of oviduct pathology, without significantly altering the course of infection. Conversely, IN immunization with MOMP/CT/CpG prevented an ascending infection, but not the oviduct pathology. This anomaly presented a unique opportunity to study the mechanisms by which vaccines can prevent oviduct pathology, other than by controlling the infection. The IL-17 signaling in the oviducts was found to associate with both the enhancement of immunity to infection and the development of oviduct pathology. This conflicting role of IL-17 may provide some explanation for the discordance in protection between infection and disease and suggests that controlling immunopathology, as opposed to the rapid eradication of the infection, may be essential for an effective human chlamydial vaccine that prevents infertility.

Immunization with a MOMP-based vaccine protects mice against a Pulmonary Chlamydia challenge and identifies a disconnection between infection and pathology

Chlamydia pneumoniae is responsible for up to 20% of community acquired pneumonia and can exacerbate chronic inflammatory diseases. As the majority of infections are either mild or asymptomatic, a vaccine is recognized to have the greatest potential to reduce infection and disease prevalence. Using the C. muridarum mouse model of infection, we immunized animals via the intranasal (IN), sublingual (SL) or transcutaneous (TC) routes, with recombinant chlamydial major outer membrane protein (MOMP) combined with adjuvants CTA1-DD or a combination of cholera toxin/CpG-oligodeoxynucleotide (CT/CpG). Vaccinated animals were challenged IN with C. muridarum and protection against infection and pathology was assessed. SL and TC immunization with MOMP and CT/CpG was the most protective, significantly reducing chlamydial burden in the lungs and preventing weight loss, which was similar to the protection induced by a previous live infection. Unlike a previous infection however, these vaccinations also provided almost complete protection against fibrotic scarring in the lungs. Protection against infection was associated with antigen-specific production of IFNγ, TNFα and IL-17 by splenocytes, however, protection against both infection and pathology required the induction of a similar pro-inflammatory response in the respiratory tract draining lymph nodes. Interestingly, we also identified two contrasting vaccinations capable of preventing infection or pathology individually. Animals IN immunized with MOMP and either adjuvant were protected from infection, but not the pathology. Conversely, animals TC immunized with MOMP and CTA1-DD were protected from pathology, even though the chlamydial burden in this group was equivalent to the unimmunized controls. This suggests that the development of pathology following an IN infection of vaccinated animals was independent of bacterial load and may have been driven instead by the adaptive immune response generated following immunization. This identifies a disconnection between the control of infection and the development of pathology, which may influence the design of future vaccines.