DEFICIENT ANTIPNEUMOCOCCAL POLYSACCHARIDE RESPONSES IN HIV-SEROPOSITIVE PATIENTS

In a prospective study, serological responses and opsonic activity tow ards Streptococcus pneumoniae were measured in 60 HIV-infected patient s and 25 controls after the administration of the 23-valent pneumococc al vaccine (Pneumovax(R)). Serum samples were collected before vaccina tion and at weeks 1, 2, 4, and 12 after vaccination and were tested fo r the presence of antibodies against a mixture of capsular polysacchar ide antigens (pool) and against type 3 and type 4 antigens (PS3 and PS 4), using an ELISA. A serological response was defined as a two-fold o r greater increase in serum titer after vaccination. Opsonophagocytosi s was measured in patients with a definite response against PS3. Gener ally, prevaccination antipneumococcal antibody titers were clearly hig her in HIV-infected patients than in healthy controls. After vaccinati on, antipool antibody responses were found in 76% of vaccinated patien ts; 24% of the patients were non-responders. In patients with more tha n 0.300 X 10(9) CD4+ cells per liter the percentage of responders was 94%; in patients with fewer than 0.300 X 10(9) CD4+ cells per liter th is percentage was 68% (P < 0.05). The antipool response in control sub jects was 92%. A serological response to PS3 and PS4 was found in 29% and 49% of the patients, respectively, and was correlated with CD4+ ce ll count. In controls, these percentages were 48% and 92%, respectivel y. In 30% of responding patients, antibody titers dropped already to p revaccination levels by week 12 after vaccination. Opsonophagocytosis was not significantly improved by vaccination, probably because of a r elatively high preexisting opsonic activity. Although prevaccination c onditions may have had an important influence on the study outcome, th e results are not in favor of a significant beneficial effect of vacci nation with Pneumovax(R) on antibody formation in HN-infected patients . This raises further questions as to the relevance of pneumococcal va ccination in this population.